Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
DETAILED OFFICE ACTION
Information Disclosure Statement
The information disclosure statement (IDS) submitted on 2024-05-20 in compliance with the provisions of 37 CFR 1.97 has been considered by the examiner and made of record in the application file.
Claim Status
Claims 1-20 are pending in this application and are under examination in this Office Action. No claims have been allowed.
Claim Rejections - 35 USC § 112(b)
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION. —The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
Claims 9-20 are rejected under 35 U.S.C. 112(b) as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor, or for pre-AIA the applicant regards as the invention.
Regarding claim 9,
Claim 9 recites "an out-of-band region in the enhanced scattering fiber, the out-of-band region being outside of the enhanced scattering bandwidth, the out-of-band region being configured to propagate a telecom signal at a telecom signal wavelength, the out-of-band region exhibiting an out-of-band scattering that is less than the in-band enhanced scattering, the out-of-band region configured to propagate the optical telecom signal."
There is a lack of antecedent basis for "the optical telecom signal" because claim 9 previously introduces "a telecom signal at a telecom signal wavelength," not "an optical telecom signal." As written, it is unclear whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in the claim. Accordingly, the metes and bounds of claim 9 are not reasonably certain, and claim 9 is indefinite.
Regarding claim 10,
Claim 10 depends from claim 9 and recites a second in-band enhanced scattering region in the enhanced scattering fiber, the second in-band enhanced scattering region being different than the first in-band enhanced scattering region, the second in-band enhanced scattering region exhibiting a second in-band enhanced scattering, the second in-band enhanced scattering region having a second enhanced scattering bandwidth, and the second in-band enhanced scattering being greater than Rayleigh scattering.
Because claim 10 depends, directly or indirectly, from claim 9, claim 10 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 10 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 10 are not reasonably certain, and claim 10 is indefinite.
Regarding claim 11,
Claim 11 depends from claim 9 and recites that the enhanced scattering bandwidth spans a wavelength range of less than fifteen nanometers (15 nm).
Because claim 11 depends, directly or indirectly, from claim 9, claim 11 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation
recited in claim 11 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 11 are not reasonably certain, and claim 11 is indefinite.
Regarding claim 12,
Claim 12 depends from claim 9 and recites that the telecom signal wavelength is centered at approximately 1550 nanometers (nm).
Because claim 12 depends, directly or indirectly, from claim 9, claim 12 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 12 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 12 are not reasonably certain, and claim 12 is indefinite.
Regarding claim 13,
Claim 13 depends from claim 12 and recites that the enhanced scattering bandwidth is between approximately 1535 nm and approximately 1549 nm.
Because claim 13 depends, directly or indirectly, from claim 9, claim 13 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 13 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 13 are not reasonably certain, and claim 13 is indefinite.
Regarding claim 14,
Claim 14 depends from claim 9 and recites that the in-band enhanced scattering region comprises an attenuation (ae,dB), a back-scatter per unit length (pe), the pe being greater than Rayleigh scattering pR, and a back-scatter enhancement (Re,dB), the Re,dB being equal to 10·log10(pe/pR). Because claim 14 depends, directly or indirectly, from claim 9, claim 14 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 14 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal"
refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 14 are not reasonably certain, and claim 14 is indefinite.
Regarding claim 15,
Claim 15 depends from claim 14 and recites that the enhanced scattering optical fiber is further configured to extend the reach of the optical transmission system proportionally with Re,dB and inversely with ae,dB. Because claim 15 depends, directly or indirectly, from claim 9, claim 15 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 15 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 15 are not reasonably certain, and claim 15 is indefinite.
Regarding claim 16,
Claim 16 depends from claim 14 and recites that the Re,dB is between approximately fifteen decibels (15 dB) and approximately 24 dB.
Because claim 16 depends, directly or indirectly, from claim 9, claim 16 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 16 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 16 are not reasonably certain, and claim 16 is indefinite.
Regarding claim 17,
Claim 17 depends from claim 9 and recites that the out-of-band scattering is substantially the same as Rayleigh scattering. Because claim 17 depends, directly or indirectly, from claim 9, claim 17 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 17 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 17 are not reasonably certain, and claim 17 is indefinite.
Regarding claim 18,
Claim 18 depends from claim 9 and recites that the out-of-band scattering is substantially the same as scattering in an unprocessed fiber. Because claim 18 depends, directly or indirectly, from claim 9, claim 18 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 18 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9.
Accordingly, the metes and bounds of claim 18 are not reasonably certain, and claim 18 is indefinite.
Regarding claim 19,
Claim 19 depends from claim 9 and recites that the enhanced scattering optical fiber is greater than approximately 1 km in length. Because claim 19 depends, directly or indirectly, from claim 9, claim 19 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 19 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9. Accordingly, the metes and bounds of claim 19 are not reasonably certain, and claim 19 is indefinite.
Regarding claim 20,
Claim 20 depends from claim 9 and recites that the telecom signal wavelength is at least one nanometer (1 nm) outside of the enhanced scattering bandwidth.
Because claim 20 depends, directly or indirectly, from claim 9, claim 20 incorporates the indefinite limitation "the optical telecom signal" from claim 9. The additional limitation recited in claim 20 does not provide antecedent basis for "the optical telecom signal" and does not clarify whether "the optical telecom signal" refers to the previously recited "telecom signal," a different optical signal, or another signal not previously recited in claim 9. Accordingly, the metes and bounds of claim 20 are not reasonably certain, and claim 20 is indefinite.
For purposes of examination, and without withdrawing the above 35 U.S.C. 112(b) rejection, "the optical telecom signal" in claim 9 is interpreted as referring to the previously recited "telecom signal."
Claim Rejections – 35 U.S.C. § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for the obviousness rejections set forth in this Office Action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having
ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
As reiterated by the Supreme Court in KSR, and as set forth in MPEP 2141 (R-01.2024), II, the factual inquiries of Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), applied for establishing a background for determining obviousness under 35 U.S.C. §103, are summarized as follows:
Determining the scope and content of the prior art;
Ascertaining the differences between the prior art and the claims at issue;
Resolving the level of ordinary skill in the pertinent art; and
Considering objective evidence indicative of obviousness or non-obviousness, if present.
This application currently names joint inventors. In considering patentability of the claims, the examiner presumes that the subject matter disclosed in the prior art was created by another (i.e., not by the inventive entity) unless proven otherwise. Applicant is advised of the obligation under 37 C.F.R. § 1.56 to point out the inventor and effective filing dates of each claim, and any evidence of common ownership/assignment as of the effective filing date, so that the examiner may properly consider the applicability of 35 U.S.C. § 102(b)(2)(C) for any potential 35 U.S.C. § 102(a)(2) prior art against the claimed invention(s).
Claims 1, 3, 5, 6, 7, 8, 9, 10, 12 and 14-19 are rejected under 35 U.S.C. § 103 as being unpatentable over Ip et al. (WO2020163577A1) in view of Kremp et al. (US20160356709A1), further in view of Handerek et al. (“Improved Optical Power Budget in Distributed Acoustic Sensing Using Enhanced Scattering Optical Fibre,” Optical Fiber Sensors 2018), further in view of Westbrook et al. (“Enhanced Optical Fiber for Distributed Acoustic Sensing beyond the Limits of Rayleigh Backscattering,” iScience, 2020).
Claim 1
Ip expressly teaches an optical transmission system in which communication channels and distributed fiber optic sensing channels coexist on the same optical fiber using different wavelengths, WDM/DWDM, and a telecom-scale fiber link.
Ip states: "FIG. 6 shows a schematic diagram of an illustrative arrangement of a bidirectional dual-usage fiber architecture, where communications and sensing applications coexist on different wavelengths and sensing pulses and communications channels propagate in different directions in the optical fiber to mitigate nonlinear interaction according to aspects of the present disclosure" [Ip, ¶ [0015], p. 3, FIG. 6].
Ip states: "FIG. 6 shows an architecture according to aspects of the present disclosure of a bidirectional dual-usage system where data communication channels and DFOS coexist on the same optical fiber. The system includes a fiber-pair supporting two-way communications
between two nodes, which can be located in data centers or at add-drop/repeater sites" [Ip, ¶ [0049], p. 12, FIG. 6].
Regarding the limitation “a transmitter configured to transmit an optical telecom signal, the optical telecom signal having a telecom signal wavelength,” Ip teaches full C-band dense WDM telecom traffic and PS-144QAM communication channels, which necessarily require optical telecom transmitters and telecom carrier wavelengths. More particularly, Ip teaches the following actual field-trial telecom transmission:
Ip states: "In this experimental field trial, the DFOS application coexisted with full C-band 38-Tb/s transmission of dense WDM (DWDM) traffic where each of the 92x48-Gbaud channels carried PS144QAM at net data rate ≥400-Gb/s and average spectral efficiency (SE) of 8.3 b/s/Hz. To allow simultaneous DOFS, we reserve a spectral hole of three 50-GHz channels in FIG. 7" [Ip, ¶ [0057], p. 14].
Regarding the limitation “an optical amplifier optically coupled to the transmitter, the optical amplifier configured to amplify the optical telecom signal,” Ip teaches the use of booster amplifiers in the communication/sensing architecture and the filtering of ASE noise generated by those amplifiers. In a WDM/DWDM optical communication transmission system, a booster amplifier optically coupled after transmission equipment is an optical amplifier configured to amplify the transmitted optical communication signal.
Ip states: "As may be observed, the communications channels and sensing pulses travel in opposite directions in each fiber to reduce their mutual nonlinear interference, allowing both systems to operate in the C-band with low loss. As configured, diplexers are employed to
multiplex/demultiplex communication and sensing signals. This advantageously prevents out-of-band amplified spontaneous emission (ASE) noise from the booster amplifiers from swamping the weak Rayleigh back-reflection of the DFOS system, which co-propagates with the communication channels at substantially lower power, as shown in the figure" [Ip, ¶ [0050], p. 12, FIG. 6].
To the extent additional amplifier disclosure is desired, Ip also explains that optical amplification schemes such as EDFA or Raman amplification are used in optical sensing/communication links:
Ip states: "Optical amplification schemes, such as EDFA or Raman amplifications, can amplify the sensing signals with added optical ASE noise, which is wide band compared to the sensing signal" [Ip, ¶ [0031], pp. 6-7].
Regarding the limitation “a telecom optical fiber suitable for telecommunications applications, the telecom optical fiber being longer than forty kilometers (40 km),” Ip expressly teaches a 55 km field-installed fiber cable and also 110 km propagation obtained using two 55 km spans. A 55 km fiber cable is longer than 40 km and is used for C-band DWDM telecom transmission.
Ip states: "The FIG. 8(A) waterfall plot was recorded using Rayleigh-based DVS on a 55-km fiber cable in a metropolitan area. The horizontal and vertical axes denote fiber position and time, respectively" [Ip, ¶ [0056], p. 14, FIG. 8(A)].
Ip states: "FIG. 8(C) shows the constellation diagrams of one of the PS-144 QAM in back-to-back configuration and after 110-km propagation (two 55-km spans concatenated, with the bidirectional architecture implemented on one of the spans). The launch power of the sensing
pulse was adjusted for optimum operation of both communication and DOFS systems. The presence of the sensing pulse did not produce any perceptible difference in signal quality of the transmission channels. Error free operation (pre-FEC BER < 2.2x10-2) was achieved, demonstrating the feasibility of the scheme" [Ip, ¶ [0058], p. 14, FIG. 8(C)].
Regarding the limitation “an enhanced scattering optical fiber optically coupled to the telecom optical fiber, the enhanced scattering optical fiber being configured to extend reach of the optical transmission system,” Ip does not expressly disclose replacing or supplementing the fiber span with the specific enhanced scattering optical fiber recited in the claim. However, within analogous art, Kremp teaches high backscattering optical fibers and Handerek teaches using such an enhanced scattering optical fiber after a long standard G.652 lead-in fiber to improve the optical power budget and reach/sensitivity of distributed acoustic sensing.
Kremp states: "The present disclosure provides high backscattering waveguides (e.g., optical fibers) and sensors employing high backscattering optical fibers. Briefly described, one embodiment comprises a high backscattering fiber that reflects a relative power that is more than three (3) decibels (dB) above the Rayleigh scattering. For some embodiments, the high backscattering fiber also exhibits a coupling loss of less than 0.5 dB" [Kremp, ¶ [0004], p. 1].
Handerek states: "A 1 km long scattering fibre was processed in a manner similar to that described in reference [4] using the techniques of [5]. The attenuation was measured using an OTDR and was found to be 0.4 dB/km. The fibre core was a standard G.652 compliant single mode type" [Handerek, p. 1, Section 2].
Handerek states: "For long-range testing, a 40 km length of G.652 fibre was placed between the interrogator and the PZT coil assembly" [Handerek, p. 2, Section 3].
Westbrook further teaches that engineered enhanced-scattering fibers were known to improve DAS sensing signal over telecom-length fiber spans, with less than 0.5 dB/km attenuation and compensation of attenuation over a 1.5-km length.
Westbrook states: "We report on engineered fibers with enhanced optical backscattering that exceeds Rayleigh scattering limits by more than one order of magnitude. We measure attenuation less than 0.5 dB/km from 1,300 to 1,650 nm. By controlling the enhanced backscatter over a 1.5-km length, we compensate for this attenuation, resulting in a higher backscatter signal at the end of the fiber." [Westbrook, p. 1, Summary].
Westbrook states: "Such systems can be implemented over lengths in excess of 40 km of standard fiber, and the output can be interpreted with various algorithms giving information about mechanical faults, fluid flow, seismic activity, vehicle traffic, security intrusions, and other disturbances." [Westbrook, p. 1].
Regarding the limitation “an in-band enhanced scattering region in the enhanced scattering optical fiber, the in-band enhanced scattering region having an enhanced scattering bandwidth,” Kremp expressly teaches a reflectivity enhancement in one or more desired in-band wavelength ranges and teaches that enhanced backscatter may exist only in a controlled range of wavelengths.
Kremp states: "High backscattering optical fibers and the sensors with high backscattering fibers, as disclosed herein, provide solutions that increase backscatter without significantly
affecting other properties of the waveguide. This is accomplished by altering or modifying the refractive index by applying an appropriate spatial pattern that creates a refractive index perturbation, which: (a) causes a reflectivity that is greater than three (3) or preferably greater than ten (10) decibels (dB) above Rayleigh scattering within one or more ranges of desired wavelengths (in-band) (for both single and multiple wavelength windows); but (b) maintains signal integrity and exhibits a coupling loss with a standard single-mode or multimode fiber of less than 0.5 dB, or preferably less than 0.2 dB" [Kremp, ¶ [0014], pp. 1-2].
Kremp states: "the enhanced backscatter Rp→r(λ,z,l) should preferably exist only in a well controlled range of wavelengths (in-band), which may be equal to the bandwidth of the interrogation scheme (OTDR, OFDR, etc.), to keep the required dosage of the actinic radiation and the induced additional transmission loss for the guided light as low as possible" [Kremp, US 2016/0356709 A1, ¶ [0025], p. 3].
Regarding the limitation that the in-band enhanced scattering region comprises attenuation (ae,dB), a back-scatter per unit length (ρe), ρe greater than Rayleigh scattering ρR, and a back-scatter enhancement (Re,dB) equal to 10·log10(ρe/ρR), Kremp teaches the same physical quantities using reflectivity density / relative reflected power per unit length, Rayleigh backscatter, enhanced backscatter greater than Rayleigh, and decibel comparison to Rayleigh.
Kremp states: "With Rp→r(λ,z,l), we denote the relative amount of power that is being reflected per unit length from fiber mode Ep to a counter-propagating mode Er at wavelength λ due to the additional refractive index perturbation Δn(x,y,z) in a section of length l at position z. Rp→r(λ,z,l) has the unit 1/m, so it is actually a reflectivity density, but, for
convenience, we sometimes refer to it as the relative reflected power, reflectivity, or enhanced backscatter, respectively" [Kremp, ¶ [0023], p. 3].
Kremp states: "With Rp→r(Rayleigh)(λ,z), we denote the Rayleigh backscatter from fiber mode Ep to a counter-propagating mode Er at wavelength λ and position z, which is well known to add incoherently and therefore is independent of the integration length l. Assuming that the Rayleigh and enhanced backscatter add incoherently as well, the total backscatter of the fiber is approximately given by R(total)p→r(λ,z,l) = R(Rayleigh)p→r(λ,z)+Rp→r(λ,z,l)" [Kremp, ¶ [0024], p. 3].
Kremp states: "Preferably, for some embodiments, Rp→r(λ,z,l) is considered sufficiently strong if it is more than 10 dB above the native Rayleigh scattering of the fiber. In the case of standard single mode fiber, the native Rayleigh scattering level is approximately 6·10-11/mm. Applying the decadic logarithm and multiplying with a factor of 10, we obtain 10 log10(6·10-11)=-102.22" [Kremp, ¶ [0029], p. 4].
Additionally, Handerek provides an actual enhanced scattering fiber having a measured attenuation and a measured in-band scattering enhancement above base Rayleigh scattering:
Handerek states: "A 1 km long scattering fibre was processed in a manner similar to that described in reference [4] using the techniques of [5]. The attenuation was measured using an OTDR and was found to be 0.4 dB/km. The fibre core was a standard G.652 compliant single mode type" [Handerek, p. 1, Section 2].
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted
from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Westbrook also teaches that a controlled enhanced-scattering band can be measured while the out-of-band measurement remains near the Rayleigh scattering level of the unprocessed fiber, thereby reinforcing that the out-of-band region is suitable for normal transmission rather than enhanced scattering.
Westbrook states: "A 10-nm enhanced scattering bandwidth is observed." [Westbrook, p. 4, FIG. 1A].
Westbrook states: "This out-of-band measurement is very close to the Rayleigh scatter level of the unprocessed fiber as is apparent in Figure 1B, which includes a short length of unprocessed fiber exhibiting only Rayleigh scattering." [Westbrook, p. 4, FIG. 1B].
Regarding the limitation “an out-of-band region in the enhanced scattering optical fiber, the out-of-band region comprising wavelengths that are outside of the enhanced scattering bandwidth, the telecom signal wavelength being in the out-of-band region, the out-of-band region exhibiting an out-of-band scattering, the out-of-band scattering being less than the ρe in the in-band enhanced scattering region, the out-of-band region configured to propagate the optical telecom signal,” Kremp teaches enhanced scattering within a desired in-band range and Rayleigh-like lower scattering outside that desired range. Handerek supplies the specific example of 1540 nm being inside the scattering band and 1550 nm being outside the scattering
bandwidth, with the 1550 nm trace representing the Rayleigh backscattering level of unenhanced fiber.
Kremp states: "the high backscattering optical fiber can attain a backscattered signal (within a desired range or multiple desired ranges of wavelengths (in-band) and at a desired longitudinal resolution length) that is at least 3 dB, or preferably at least 10 dB, above the Rayleigh backscatter observed outside of the desired range (out-of-band) at the desired longitudinal resolution length" [Kremp, ¶ [0014], p. 2].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Regarding the limitation “a receiver optically coupled to the enhanced scattering optical fiber, the receiver configured to receive the optical telecom signal,” Ip teaches received PS-144QAM communication-channel signal quality after propagation and coherent detection/DSP, and therefore teaches receiver-side receipt of the optical telecom signal.
Ip states: "FIG. 8(C) shows the constellation diagrams of one of the PS-144 QAM in back-to-back configuration and after 110-km propagation (two 55-km spans concatenated, with the bidirectional architecture implemented on one of the spans). The launch power of the sensing pulse was adjusted for optimum operation of both communication and DOFS systems. The presence of the sensing pulse did not produce any perceptible difference in signal quality of the transmission channels. Error free operation (pre-FEC BER < 2.2x10-2) was achieved, demonstrating the feasibility of the scheme" [Ip, ¶ [0058], p. 14, FIG. 8(C)].
One of ordinary skill in the art would have been motivated to combine Ip with Kremp because Ip already identifies the desirable architecture: live C-band DWDM communication channels and distributed fiber sensing coexisting on the same optical fiber. Ip also identifies the key design pressure that must be handled in such systems: sensing pulses/backscatter signals should not degrade telecom channels, and ASE/noise and nonlinear interaction should be controlled by wavelength separation, diplexing, and opposite propagation. Kremp teaches a known enhanced backscattering fiber that increases backscatter in a selected in-band wavelength range while leaving out-of-band wavelengths closer to Rayleigh backscatter and preserving signal integrity/coupling to standard single-mode or multimode fiber. A person of ordinary skill would therefore have recognized that using Kremp’s wavelength-controlled enhanced scattering fiber in Ip’s dual-use telecom/sensing fiber system would predictably increase sensing signal strength and reach while allowing telecom signals to be placed outside the enhanced scattering band to avoid substantial penalty. That combination merely uses a
known enhanced fiber, designed for OTDR/OFDR/DAS sensing signal improvement, in the known environment of telecom/sensing coexistence taught by Ip.
One of ordinary skill in the art would have been further motivated to apply Handerek because Handerek demonstrates that a 1 km enhanced scattering fiber after a 40 km G.652 lead-in produces a much stronger signal at a telecom-length range and gives specific design evidence that 1540 nm can be in the enhanced band while 1550 nm remains outside the enhanced scattering bandwidth at the Rayleigh/unprocessed level. This directly addresses the same problem faced in Ip: using fiber sensing over long deployed telecom links without degrading communication channels. The combination is a predictable use of known WDM channel separation, known enhanced scattering fibers, and known long-reach DAS/OTDR design principles to improve sensing reach while preserving telecom transmission. Therefore, claim 1 would have been obvious.
One of ordinary skill in the art would have been further motivated to apply Westbrook because Westbrook confirms, before the present effective filing date, that enhanced optical fiber could provide more than an order of magnitude backscatter improvement, attenuation less than 0.5 dB/km across telecom wavelengths, and compensation of attenuation over kilometer-scale lengths. Westbrook therefore supplies additional reasonable expectation of success for inserting or coupling an enhanced scattering fiber into the long telecom/sensing architecture of Ip while using the in-band/out-of-band spectral behavior taught by Kremp and Handerek. The combination would have predictably improved distributed sensing reach and SNR while preserving telecom signal propagation outside the enhanced scattering bandwidth.
Claim 3
With respect to claim 3, all limitations of claim 1 are taught by Ip, Kremp, Handerek and Westbrook, except claim 3 additionally recites that the telecom signal wavelength is centered at approximately 1550 nm. However, within analogous art, Ip teaches C-band DWDM telecom transmission, and Handerek teaches 1550 nm as the out-of-band wavelength outside the enhanced scattering bandwidth. Kremp likewise teaches enhanced backscatter design around the conventional 1550 nm telecom region.
Ip states: "In this experimental field trial, the DFOS application coexisted with full C-band 38-Tb/s transmission of dense WDM (DWDM) traffic where each of the 92x48-Gbaud channels carried PS144QAM at net data rate ≥400-Gb/s and average spectral efficiency (SE) of 8.3 b/s/Hz. To allow simultaneous DOFS, we reserve a spectral hole of three 50-GHz channels in FIG. 7" [Ip, ¶ [0057], p. 14].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
Kremp states: "FIGS. 1A and 1B are graphs showing the reflectivity for one embodiment in which the integration length is one (1) millimeter (mm) in a 119.5 centimeter (cm) long fiber section with a design level of -80 decibel (dB) backscatter per 1 mm (1/mm) in a wavelength range of 1550±7.5 nanometers (nm)" [Kremp, ¶ [0007], p. 1, FIGS. 1A-1B].
One of ordinary skill in the art would have been motivated to use an optical telecom signal centered at approximately 1550 nm because the C-band around 1550 nm is a standard low-loss
telecommunications window, Ip uses full C-band DWDM traffic, and Handerek expressly demonstrates 1550 nm as an out-of-band wavelength when the enhanced scattering band is at 1535-1545 nm. Placing the telecom signal at approximately 1550 nm would have predictably allowed the telecom signal to propagate in the out-of-band region while the enhanced scattering fiber improves sensing at nearby in-band wavelengths. Therefore, claim 3 would have been obvious.
Claim 5
With respect to claim 5, all limitations of claim 1 are taught by Ip, Kremp, Handerek and Westbrook, except claim 5 additionally recites that the enhanced scattering optical fiber is further configured to extend the reach of the optical transmission system proportionally with Re,dB and inversely with ae,dB. However, within analogous art, Handerek teaches the practical result of using enhanced scattering fiber to improve signal-to-noise ratio and sensitivity at long range, while Kremp teaches that enhanced backscatter and loss/attenuation are related design considerations. A proportional relationship between reach improvement and backscatter enhancement, and an inverse relationship with attenuation, is the predictable physical result of increasing useful backscattered signal while reducing attenuation.
Handerek states: "We demonstrate a significant increase in the optical power budget of distributed acoustic sensing using enhanced scattering optical fibre. Signal to noise ratio is increased by around 16 dB at both 1 km and 41 km range and sensitivity by more than 30 dB
at 41 km" [Handerek, Improved Optical Power Budget in Distributed Acoustic Sensing Using Enhanced Scattering Optical Fibre, p. 1].
Handerek states: "Table 1. Performance results for G.652 and grating fibres ... Improvement (dB) 6.3 15.7 12.5 31.8 16.0 33.4" [Handerek, p. 4, Table 1].
Westbrook further supports the reach relationship because it teaches that controlling the enhanced backscatter over 1.5 km compensates attenuation and produces higher signal at the fiber end.
Westbrook states: "By controlling the enhanced backscatter over a 1.5-km length, we compensate for this attenuation, resulting in a higher backscatter signal at the end of the fiber." [Westbrook, p. 1, Summary].
Kremp states: "Those having skill in the art will appreciate that the ability to tailor Δnz(z) in Eq. (5) results in a corresponding ability to tailor the amount of backscattering without significantly affecting other signal transmission and reflection properties, such as e.g., loss, nonlinearity, or mode field diameter" [Kremp, ¶ [0031], p. 4].
One of ordinary skill in the art would have been motivated to configure the enhanced scattering optical fiber to extend reach according to the amount of backscatter enhancement and attenuation because those are the known result-effective variables controlling the received backscatter signal budget. Handerek demonstrates that increasing the in-band backscatter of the fiber provides a much larger sensing signal after a 40 km lead-in, while Kremp teaches tailoring the amount of backscattering without substantially affecting transmission properties. Increasing Re,dB increases the useful returned signal, whereas increasing ae,dB consumes
optical power over distance. A person of ordinary skill would therefore have optimized these known variables to extend reach, producing the claimed proportional/inverse relationship. Therefore, claim 5 would have been obvious.
Claim 6
With respect to claim 6, all limitations of claim 5 are taught by Ip, Kremp, Handerek and Westbrook, except claim 6 additionally recites that Re,dB is between approximately 15 dB and approximately 24 dB. However, within analogous art, Handerek expressly teaches approximately 15 dB above base Rayleigh scattering. Kremp teaches a design level of -80 dB/mm in the 1550±7.5 nm band and also teaches native Rayleigh scattering at approximately -102.22 dB/mm, corresponding to about 22 dB enhancement.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, Section 2, FIG. 1(b)].
Kremp states: "FIGS. 1A and 1B are graphs showing the reflectivity for one embodiment in which the integration length is one (1) millimeter (mm) in a 119.5 centimeter (cm) long fiber section with a design level of -80 decibel (dB) backscatter per 1 mm (1/mm) in a wavelength range of 1550±7.5 nanometers (nm)" [Kremp, ¶ [0007], p. 1, FIGS. 1A-1B].
Kremp states: "Preferably, for some embodiments, Rp→r(λ,z,l) is considered sufficiently strong if it is more than 10 dB above the native Rayleigh scattering of the fiber. In the case of standard single mode fiber, the native Rayleigh scattering level is approximately 6·10-11/mm. Applying the decadic logarithm and multiplying with a factor of 10, we obtain 10 log10(6·10-11)=-102.22" [Kremp, ¶ [0029], p. 4].
One of ordinary skill in the art would have been motivated to select an enhancement in the 15-24 dB range because the range is shown by the prior art to provide meaningful DAS/OTDR signal improvement without requiring impractically large scattering or unacceptable attenuation/MPI. Handerek demonstrates an approximately 15 dB in-band enhancement with long-reach DAS performance improvements, while Kremp demonstrates a design level that is approximately 22 dB above native Rayleigh scattering. Selecting a value within this proven operating range would have been a routine selection from a known workable range to balance stronger backscatter against attenuation and MPI. Therefore, claim 6 would have been obvious.
Claim 7
With respect to claim 7, all limitations of claim 1 are taught by Ip, Kremp, Handerek and Westbrook, except claim 7 additionally recites that the out-of-band scattering is substantially the same as Rayleigh scattering. However, within analogous art, Kremp teaches enhanced scattering in-band and Rayleigh backscatter outside the desired range. Handerek expressly teaches that the 1550 nm out-of-band trace represents the Rayleigh backscattering level of unenhanced G.652 fiber.
Kremp states: "the high backscattering optical fiber can attain a backscattered signal (within a desired range or multiple desired ranges of wavelengths (in-band) and at a desired longitudinal resolution length) that is at least 3 dB, or preferably at least 10 dB, above the Rayleigh backscatter observed outside of the desired range (out-of-band) at the desired longitudinal resolution length" [Kremp, ¶ [0014], p. 2].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
One of ordinary skill in the art would have been motivated to keep out-of-band scattering substantially the same as Rayleigh scattering because Ip teaches simultaneous communication and sensing in a WDM/DWDM environment where communication channels should not be degraded by the sensing function. The known solution taught by Kremp and confirmed by Handerek is to confine the scattering enhancement to the sensing band and leave out-of-band wavelengths near ordinary Rayleigh level. That design predictably reduces communication-channel penalty while preserving enhanced sensing in the selected band. Therefore, claim 7 would have been obvious.
Westbrook provides additional confirmation that out-of-band scattering is close to Rayleigh scattering of the unprocessed fiber.
Westbrook states: "This out-of-band measurement is very close to the Rayleigh scatter level of the unprocessed fiber as is apparent in Figure 1B, which includes a short length of unprocessed fiber exhibiting only Rayleigh scattering." [Westbrook, p. 4, FIG. 1B].
Claim 8
With respect to claim 8, all limitations of claim 1 are taught by Ip, Kremp, Handerek and Westbrook, except claim 8 additionally recites that the enhanced scattering optical fiber is greater than approximately 1 km in length. However, within analogous art, Handerek teaches a 1 km long enhanced scattering fiber and demonstrates its use after a 40 km G.652 lead-in. In view of the word “approximately,” this teaching reads on the recited greater-than-approximately-1-km limitation, or at least renders it obvious to use an enhanced scattering length of approximately 1 km or slightly greater.
Handerek states: "A 1 km long scattering fibre was processed in a manner similar to that described in reference [4] using the techniques of [5]. The attenuation was measured using an OTDR and was found to be 0.4 dB/km. The fibre core was a standard G.652 compliant single mode type" [Handerek, p. 1, Section 2].
Handerek states: "We have demonstrated improved distributed acoustic and vibration sensing using a 1 km length of optical fibre with continuous, grating-enhanced backscattering along its length" [Handerek, p. 4, Section 5].
One of ordinary skill in the art would have been motivated to use an enhanced scattering fiber length of approximately 1 km or greater because Handerek shows that such a length is practical, continuous, and effective for long-range DAS improvement after a 40 km standard-fiber lead-in. In the Ip telecom/sensing architecture, a fiber segment long enough to provide distributed sensing improvement at locations of interest would be useful, and Handerek provides the predictable working example. Therefore, claim 8 would have been obvious.
Westbrook also teaches enhanced backscatter over 1.5 km and therefore confirms enhanced scattering fiber lengths greater than approximately 1 km.
Westbrook states: "By controlling the enhanced backscatter over a 1.5-km length, we compensate for this attenuation, resulting in a higher backscatter signal at the end of the fiber." [Westbrook, p. 1, Summary].
Claim 9
With respect to independent claim 9, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, the phrase “the optical telecom signal” is interpreted as referring to the previously recited “telecom signal.” Claim 9 recites a broader optical transmission system than claim 1 and omits the transmitter, optical amplifier, and receiver. The remaining limitations are taught by the same combination of Ip, Kremp, Handerek, and Westbrook.
Regarding “a telecom optical fiber that exceeds forty kilometers (40 km) in length,” Ip teaches a 55 km fiber cable used in a metropolitan field trial and also 110 km propagation through two 55 km spans. Handerek separately teaches sensing systems over lengths in excess of 40 km and a 40 km G.652 lead-in fiber.
Ip states: "The FIG. 8(A) waterfall plot was recorded using Rayleigh-based DVS on a 55-km fiber cable in a metropolitan area. The horizontal and vertical axes denote fiber position and time, respectively" [Ip, ¶ [0056], p. 14, FIG. 8(A)].
Ip states: "FIG. 8(C) shows the constellation diagrams of one of the PS-144 QAM in back-to-back configuration and after 110-km propagation (two 55-km spans concatenated, with the bidirectional architecture implemented on one of the spans). The launch power of the sensing pulse was adjusted for optimum operation of both communication and DOFS systems. The presence of the sensing pulse did not produce any perceptible difference in signal quality of the transmission channels. Error free operation (pre-FEC BER < 2.2x10-2) was achieved, demonstrating the feasibility of the scheme" [Ip, ¶ [0058], p. 14, FIG. 8(C)].
Handerek states: "Sensing systems can be implemented over lengths in excess of 40 km of standard fibre, and the output can be interpreted with various algorithms giving information about mechanical faults, fluid flow, seismic activity, vehicle traffic, security intrusions, and other disturbances" [Handerek, p. 1].
Handerek states: "For long-range testing, a 40 km length of G.652 fibre was placed between the interrogator and the PZT coil assembly" [Handerek, p. 2, Section 3].
Regarding “an enhanced scattering fiber optically coupled to the telecom optical fiber, the enhanced scattering fiber configured to extend reach of the optical transmission system,” Kremp teaches the enhanced scattering fiber itself, and Handerek teaches optically using a 1 km enhanced scattering fiber after a 40 km standard fiber lead-in to improve the optical power budget.
Kremp states: "The present disclosure provides high backscattering waveguides (e.g., optical fibers) and sensors employing high backscattering optical fibers. Briefly described, one embodiment comprises a high backscattering fiber that reflects a relative power that is more
than three (3) decibels (dB) above the Rayleigh scattering. For some embodiments, the high backscattering fiber also exhibits a coupling loss of less than 0.5 dB" [Kremp, ¶ [0004], p. 1].
Handerek states: "A 1 km long scattering fibre was processed in a manner similar to that described in reference [4] using the techniques of [5]. The attenuation was measured using an OTDR and was found to be 0.4 dB/km. The fibre core was a standard G.652 compliant single mode type" [Handerek, p. 1, Section 2].
Handerek states: "Table 1. Performance results for G.652 and grating fibres ... Improvement (dB) 6.3 15.7 12.5 31.8 16.0 33.4" [Handerek, p. 4, Table 1].
Regarding “an in-band enhanced scattering region in the enhanced scattering fiber, the in-band enhanced scattering region exhibiting an in-band enhanced scattering, the in-band enhanced scattering region having an enhanced scattering bandwidth, the in-band enhanced scattering being greater than Rayleigh scattering,” Kremp and Handerek expressly teach in-band enhanced scattering greater than Rayleigh scattering and an enhanced scattering bandwidth.
Kremp states: "High backscattering optical fibers and the sensors with high backscattering fibers, as disclosed herein, provide solutions that increase backscatter without significantly affecting other properties of the waveguide. This is accomplished by altering or modifying the refractive index by applying an appropriate spatial pattern that creates a refractive index perturbation, which: (a) causes a reflectivity that is greater than three (3) or preferably greater than ten (10) decibels (dB) above Rayleigh scattering within one or more ranges of desired wavelengths (in-band) (for both single and multiple wavelength windows); but (b)
maintains signal integrity and exhibits a coupling loss with a standard single-mode or multimode fiber of less than 0.5 dB, or preferably less than 0.2 dB" [Kremp, ¶ [0014], pp. 1-2].
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Regarding “an out-of-band region in the enhanced scattering fiber, the out-of-band region being outside of the enhanced scattering bandwidth, the out-of-band region being configured to propagate a telecom signal at a telecom signal wavelength, the out-of-band region exhibiting an out-of-band scattering that is less than the in-band enhanced scattering,” Kremp teaches that the enhanced backscatter is in-band and the Rayleigh backscatter is observed out-of-band, while Handerek teaches that 1550 nm is outside the scattering bandwidth and represents Rayleigh backscattering level of unenhanced G.652 fiber.
Kremp states: "the high backscattering optical fiber can attain a backscattered signal (within a desired range or multiple desired ranges of wavelengths (in-band) and at a desired longitudinal resolution length) that is at least 3 dB, or preferably at least 10 dB, above the Rayleigh backscatter observed outside of the desired range (out-of-band) at the desired longitudinal resolution length" [Kremp, ¶ [0014], p. 2].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
One of ordinary skill in the art would have been motivated to combine these teachings for claim 9 for the same core reasons explained with respect to claim 1. Ip provides the telecom/sensing fiber-link architecture and demonstrates that telecom DWDM traffic can coexist with fiber sensing over long deployed fiber. Kremp provides the known enhanced scattering fiber with a controlled in-band/out-of-band spectral profile. Handerek provides the long-reach 40 km lead-in plus 1 km enhanced scattering-fiber demonstration and the specific 1540/1550 nm spectral relationship. The combination would have predictably yielded the claim-9 system: a telecom fiber longer than 40 km coupled to an enhanced scattering fiber having an in-band enhanced scattering region and an out-of-band region for propagating a telecom signal. Therefore, claim 9 would have been obvious.
Claim 10
With respect to claim 10, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 10 additionally recites that the in-band enhanced scattering region is a first in-band enhanced scattering region and that the system further comprises a second in-band enhanced scattering region in the enhanced scattering fiber, different from the first, having a second enhanced scattering bandwidth and second in-band
enhanced scattering greater than Rayleigh scattering. However, within analogous art, Kremp expressly teaches single and multiple wavelength windows and teaches that index variations may include two or more primary length scales, which would provide different enhanced scattering regions/bandwidths.
Kremp states: "High backscattering optical fibers and the sensors with high backscattering fibers, as disclosed herein, provide solutions that increase backscatter without significantly affecting other properties of the waveguide. This is accomplished by altering or modifying the refractive index by applying an appropriate spatial pattern that creates a refractive index perturbation, which: (a) causes a reflectivity that is greater than three (3) or preferably greater than ten (10) decibels (dB) above Rayleigh scattering within one or more ranges of desired wavelengths (in-band) (for both single and multiple wavelength windows); but (b) maintains signal integrity and exhibits a coupling loss with a standard single-mode or multimode fiber of less than 0.5 dB, or preferably less than 0.2 dB" [Kremp, ¶ [0014], pp. 1-2].
Kremp states: "In another embodiment, there would be two or more primary length scales for the index variations. In yet another embodiment, the backscattering signal would vary along the fiber. The backscattering signal might be the same as the native, inherent scattering for certain points along the fiber" [Kremp, ¶ [0061], p. 7].
One of ordinary skill in the art would have been motivated to include a second in-band enhanced scattering region because WDM/DWDM telecom systems such as those taught by Ip use multiple wavelength channels and spectral planning. Kremp teaches that the enhanced scattering may be provided in multiple wavelength windows and with multiple primary length
scales. Using multiple enhanced scattering regions would have predictably allowed different sensing/interrogation wavelengths or different sections of the fiber link to be optimized independently while keeping telecom wavelengths outside those enhanced bands. Therefore, claim 10 would have been obvious.
Claim 12
With respect to claim 12, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 12 additionally recites that the telecom signal wavelength is centered at approximately 1550 nm. This limitation is taught for the same reasons discussed with respect to claim 3. However, within analogous art, Ip teaches C-band WDM/DWDM telecom communication, and Handerek teaches 1550 nm as an out-of-band wavelength outside the enhanced scattering bandwidth.
Ip states: "In this experimental field trial, the DFOS application coexisted with full C-band 38-Tb/s transmission of dense WDM (DWDM) traffic where each of the 92x48-Gbaud channels carried PS144QAM at net data rate ≥400-Gb/s and average spectral efficiency (SE) of 8.3 b/s/Hz. To allow simultaneous DOFS, we reserve a spectral hole of three 50-GHz channels in FIG. 7" [Ip, ¶ [0057], p. 14].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
One of ordinary skill in the art would have been motivated to center the telecom signal wavelength at approximately 1550 nm because it is a conventional telecom C-band region used for optical communication, and Handerek demonstrates that 1550 nm can be outside the enhanced scattering band. Selecting 1550 nm would have predictably allowed the telecom signal to propagate outside the enhanced scattering bandwidth while keeping sensing enhancement nearby in the C-band. Therefore, claim 12 would have been obvious.
Claim 14
With respect to claim 14, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 14 additionally recites that the in-band enhanced scattering region comprises attenuation (ae,dB), back-scatter per unit length (ρe), ρe greater than Rayleigh scattering ρR, and a back-scatter enhancement (Re,dB) equal to 10·log10(ρe/ρR). However, within analogous art, Kremp teaches reflectivity density / relative reflected power per unit length, Rayleigh backscatter, and enhanced backscatter greater than Rayleigh. Handerek teaches measured attenuation and an approximately 15 dB enhancement above base Rayleigh scattering.
Kremp states: "With Rp→r(λ,z,l), we denote the relative amount of power that is being reflected per unit length from fiber mode Ep to a counter-propagating mode Er at wavelength λ due to the additional refractive index perturbation Δn(x,y,z) in a section of length l at position z. Rp→r(λ,z,l) has the unit 1/m, so it is actually a reflectivity density, but, for
convenience, we sometimes refer to it as the relative reflected power, reflectivity, or enhanced backscatter, respectively" [Kremp, ¶ [0023], p. 3].
Kremp states: "With Rp→r(Rayleigh)(λ,z), we denote the Rayleigh backscatter from fiber mode Ep to a counter-propagating mode Er at wavelength λ and position z, which is well known to add incoherently and therefore is independent of the integration length l. Assuming that the Rayleigh and enhanced backscatter add incoherently as well, the total backscatter of the fiber is approximately given by R(total)p→r(λ,z,l) = R(Rayleigh)p→r(λ,z)+Rp→r(λ,z,l)" [Kremp, ¶ [0024], p. 3].
Kremp states: "Preferably, for some embodiments, Rp→r(λ,z,l) is considered sufficiently strong if it is more than 10 dB above the native Rayleigh scattering of the fiber. In the case of standard single mode fiber, the native Rayleigh scattering level is approximately 6·10-11/mm. Applying the decadic logarithm and multiplying with a factor of 10, we obtain 10 log10(6·10-11)=-102.22" [Kremp, ¶ [0029], p. 4].
Handerek states: "A 1 km long scattering fibre was processed in a manner similar to that described in reference [4] using the techniques of [5]. The attenuation was measured using an OTDR and was found to be 0.4 dB/km. The fibre core was a standard G.652 compliant single mode type" [Handerek, p. 1, Section 2].
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced
scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
One of ordinary skill in the art would have understood that Re,dB = 10·log10(ρe/ρR) is the ordinary decibel expression of an enhancement ratio between the enhanced scattering per unit length and the Rayleigh scattering per unit length. The prior art expressly measures and describes the same relationship as dB enhancement above Rayleigh scattering. Therefore, applying the standard logarithmic dB expression to the enhanced-versus-Rayleigh backscatter taught by Kremp and Handerek would have been a predictable mathematical statement of the known physical relationship rather than a patentable structural difference. Therefore, claim 14 would have been obvious.
Claim 15
With respect to claim 15, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 14 are taught by Ip, Kremp, Handerek and Westbrook, except claim 15 additionally recites that the enhanced scattering optical fiber is further configured to extend the reach of the optical transmission system proportionally with Re,dB and inversely with ae,dB. This limitation is taught or rendered obvious for the same reasons discussed with respect to claim 5.
Handerek states: "We demonstrate a significant increase in the optical power budget of distributed acoustic sensing using enhanced scattering optical fibre. Signal to noise ratio is increased by around 16 dB at both 1 km and 41 km range and sensitivity by more than 30 dB
at 41 km" [Handerek, Improved Optical Power Budget in Distributed Acoustic Sensing Using Enhanced Scattering Optical Fibre, p. 1].
Handerek states: "Table 1. Performance results for G.652 and grating fibres ... Improvement (dB) 6.3 15.7 12.5 31.8 16.0 33.4" [Handerek, p. 4, Table 1].
Kremp states: "Those having skill in the art will appreciate that the ability to tailor Δnz(z) in Eq. (5) results in a corresponding ability to tailor the amount of backscattering without significantly affecting other signal transmission and reflection properties, such as e.g., loss, nonlinearity, or mode field diameter" [Kremp, ¶ [0031], p. 4].
One of ordinary skill in the art would have been motivated to configure the claim-14 enhanced scattering fiber to increase reach according to the known link budget variables: stronger in-band backscatter increases the returned sensing signal and greater attenuation reduces usable reach. Handerek demonstrates the practical benefit at 1 km and 41 km, and Kremp teaches tailoring backscatter while preserving transmission properties. Thus, configuring reach to vary proportionally with Re,dB and inversely with ae,dB is the predictable design result of using the prior-art enhanced scattering fiber in a long optical link. Therefore, claim 15 would have been obvious.
Claim 16
With respect to claim 16, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 14 are taught by Ip, Kremp, Handerek and Westbrook, except claim 16 additionally recites that Re,dB is between
approximately 15 dB and approximately 24 dB. This limitation is taught for the same reasons discussed with respect to claim 6.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Kremp states: "FIGS. 1A and 1B are graphs showing the reflectivity for one embodiment in which the integration length is one (1) millimeter (mm) in a 119.5 centimeter (cm) long fiber section with a design level of -80 decibel (dB) backscatter per 1 mm (1/mm) in a wavelength range of 1550±7.5 nanometers (nm)" [Kremp, ¶ [0007], p. 1, FIGS. 1A-1B].
Kremp states: "Preferably, for some embodiments, Rp→r(λ,z,l) is considered sufficiently strong if it is more than 10 dB above the native Rayleigh scattering of the fiber. In the case of standard single mode fiber, the native Rayleigh scattering level is approximately 6·10-11/mm. Applying the decadic logarithm and multiplying with a factor of 10, we obtain 10 log10(6·10-11)=-102.22" [Kremp, ¶ [0029], p. 4].
One of ordinary skill in the art would have selected a 15-24 dB enhancement because Handerek demonstrates approximately 15 dB and Kremp demonstrates an approximately 22 dB enhancement when its -80 dB/mm design level is compared to the native Rayleigh level of approximately -102.22 dB/mm. These values are proven working values in the same
technology. Selecting a value in this range would have been a routine optimization to balance sensing signal improvement with attenuation and MPI. Therefore, claim 16 would have been obvious.
Claim 17
With respect to claim 17, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 17 additionally recites that the out-of-band scattering is substantially the same as Rayleigh scattering. This limitation is taught for the same reasons discussed with respect to claim 7.
Kremp states: "the high backscattering optical fiber can attain a backscattered signal (within a desired range or multiple desired ranges of wavelengths (in-band) and at a desired longitudinal resolution length) that is at least 3 dB, or preferably at least 10 dB, above the Rayleigh backscatter observed outside of the desired range (out-of-band) at the desired longitudinal resolution length" [Kremp, ¶ [0014], p. 2].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
One of ordinary skill in the art would have been motivated to keep the out-of-band region at substantially Rayleigh scattering level because the telecom signal of Ip is to coexist with fiber sensing, and the communication wavelength should avoid the enhanced scattering penalty.
Kremp expressly teaches Rayleigh backscatter outside the desired enhanced range, and Handerek verifies 1550 nm outside the scattering bandwidth at unenhanced Rayleigh level. Therefore, claim 17 would have been obvious.
Claim 18
With respect to claim 18, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 18 additionally recites that the out-of-band scattering is substantially the same as scattering in an unprocessed fiber. However, within analogous art, Kremp teaches enhanced backscatter above Rayleigh observed outside the desired range, meaning the outside range is not enhanced like the in-band region. Handerek expressly teaches that the 1550 nm out-of-band trace represents the Rayleigh backscattering level of unenhanced G.652 fiber.
Kremp states: "the high backscattering optical fiber can attain a backscattered signal (within a desired range or multiple desired ranges of wavelengths (in-band) and at a desired longitudinal resolution length) that is at least 3 dB, or preferably at least 10 dB, above the Rayleigh backscatter observed outside of the desired range (out-of-band) at the desired longitudinal resolution length" [Kremp, ¶ [0014], p. 2].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
One of ordinary skill in the art would have been motivated to keep out-of-band scattering substantially the same as an unprocessed fiber because that design allows the telecom signal to propagate through the enhanced scattering fiber without experiencing the enhanced-scattering penalty. This was a predictable consequence of confining the index perturbation and enhanced backscatter to the sensing band. Therefore, claim 18 would have been obvious.
Westbrook further teaches that the out-of-band measurement is close to the unprocessed Rayleigh scatter level, which directly supports the limitation that the out-of-band scattering is substantially the same as scattering in an unprocessed fiber.
Westbrook states: "This out-of-band measurement is very close to the Rayleigh scatter level of the unprocessed fiber as is apparent in Figure 1B, which includes a short length of unprocessed fiber exhibiting only Rayleigh scattering." [Westbrook, p. 4, FIG. 1B].
Claim 19
With respect to claim 19, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 19 additionally recites that the enhanced scattering optical fiber is greater than approximately 1 km in length. This limitation is taught for the same reasons discussed with respect to claim 8.
Handerek states: "A 1 km long scattering fibre was processed in a manner similar to that described in reference [4] using the techniques of [5]. The attenuation was measured using
an OTDR and was found to be 0.4 dB/km. The fibre core was a standard G.652 compliant single mode type" [Handerek, p. 1, Section 2].
Handerek states: "We have demonstrated improved distributed acoustic and vibration sensing using a 1 km length of optical fibre with continuous, grating-enhanced backscattering along its length" [Handerek, p. 4, Section 5].
One of ordinary skill in the art would have been motivated to use an enhanced scattering fiber of approximately 1 km or greater in the claim-9 optical transmission system because Handerek demonstrates that such a length is scalable, continuous, and effective after a telecom-length 40 km lead-in. Applying that fiber length to Ip’s long telecom/sensing link would have predictably improved the received sensing signal at locations of interest without changing the basic principle of operation. Therefore, claim 19 would have been obvious.
Westbrook also teaches an enhanced-fiber length greater than approximately 1 km by disclosing controlled enhanced backscatter over a 1.5-km length.
Westbrook states: "By controlling the enhanced backscatter over a 1.5-km length, we compensate for this attenuation, resulting in a higher backscatter signal at the end of the fiber." [Westbrook, p. 1, Summary].
Claims 2, 4, 11, 13 and 20 are rejected under 35 U.S.C. § 103 as being unpatentable over Ip et al. in view of Kremp, further in view of Handerek et al., further in view of Westbrook et al., and further in view of Lu et al. (“Low-Loss Random Fiber Gratings Made With an fs-IR Laser for Distributed Fiber Sensing,” Journal of Lightwave Technology, 2019).
Claim 2
With respect to claim 2, all limitations of claim 1 are taught by Ip, Kremp, Handerek and Westbrook, except claim 2 further requires that the enhanced scattering bandwidth spans a wavelength range of less than fifteen nanometers (15 nm). However, within analogous art, Handerek expressly teaches an enhanced scattering bandwidth from 1535 nm to 1545 nm, which is a 10 nm bandwidth and therefore less than 15 nm.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Additionally, Lu teaches that narrow enhanced backscattering bandwidth is a known and controllable design feature for long-haul distributed fiber sensor systems.
Lu states: "Compared to conventional random gratings having broadband backscattering enhancement, the demonstrated random fiber grating has a well defined narrower bandwidth of backscattering enhancement, higher laser-induced backscattering level, and lower laser-induced loss, which are critical for long-haul distributed fiber sensor systems with high measurement accuracy" [Lu, Journal of Lightwave Technology, vol. 37, no. 18, p. 4697].
Lu states: "Because the laser’s repetition rate can be precisely tuned, both the bandwidth Δλ and central wavelength λ0, where the backscattering is enhanced, can be very well controlled" [Lu, p. 4698].
Westbrook independently teaches a 10 nm enhanced scattering bandwidth, which is less than the claimed 15 nm range.
Westbrook states: "A 10-nm enhanced scattering bandwidth is observed." [Westbrook, p. 4, FIG. 1A].
One of ordinary skill in the art would have been motivated to select an enhanced scattering bandwidth less than 15 nm because Ip teaches coexistence of telecom communication channels and sensing wavelengths in a WDM/DWDM fiber environment, where spectral separation and channel assignment are fundamental design constraints. Kremp teaches confining enhanced backscatter to a controlled wavelength band to avoid increasing loss/noise outside the desired sensing band, and Handerek demonstrates that a 10 nm enhanced scattering band provides useful sensing improvement while leaving 1550 nm outside the enhanced band at Rayleigh level. Selecting a less-than-15 nm band is therefore a predictable optimization of the known
wavelength-controlled enhanced scattering fiber to preserve adjacent telecom channels and reduce OSNR penalty. Therefore, claim 2 would have been obvious.
Claim 4
With respect to claim 4, all limitations of claim 3 are taught by Ip, Kremp, Handerek and Westbrook, except claim 4 additionally recites that the enhanced scattering bandwidth is between approximately 1535 nm and approximately 1549 nm. However, within analogous art, Handerek expressly teaches increased backscattering from 1535-1545 nm, which is within the claimed approximate 1535-1549 nm spectral window. Lu further teaches that the center wavelength and bandwidth of the enhanced backscattering can be controlled.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, Section 2, FIG. 1(a)].
Lu states: "Because the laser’s repetition rate can be precisely tuned, both the bandwidth Δλ and central wavelength λ0, where the backscattering is enhanced, can be very well controlled" [Lu, p. 4698].
One of ordinary skill in the art would have been motivated to select the enhanced scattering band between approximately 1535 nm and approximately 1549 nm because that region places the sensing enhancement below a 1550 nm telecom channel while allowing the telecom channel to remain outside the enhanced scattering bandwidth. Handerek demonstrates exactly that design relationship by placing 1540 nm in the scattering band and 1550 nm outside the scattering bandwidth at the Rayleigh level. To the extent applicant argues that the upper edge must approach 1549 nm rather than 1545 nm, Kremp and Lu teach that the enhanced backscatter spectrum, center wavelength, and bandwidth are controllable design parameters, and adjusting a controlled enhanced scattering window within the C-band to avoid the telecom carrier would have been a routine optimization yielding predictable results. Therefore, claim 4 would have been obvious.
Additionally, because claim 4 uses the term “approximately,” the 1535-1545 nm enhanced band expressly measured by Handerek is highly probative of the claimed approximately 1535-1549 nm range. The remaining extension toward 1549 nm is a small, predictable C-band edge adjustment that Lu expressly teaches can be controlled by tuning bandwidth and center wavelength, and that Kremp teaches can be set through the spatial structure of the refractive-index modification.
Claim 11
With respect to claim 11, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 11 additionally recites that the enhanced scattering bandwidth spans a wavelength range of less than 15 nm. This limitation is taught for the same reasons discussed with respect to claim 2. However, within analogous art, Handerek teaches an enhanced scattering bandwidth from 1535-1545 nm, which is 10 nm, and Lu teaches bandwidth and center wavelength control for enhanced backscattering.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Lu states: "Because the laser’s repetition rate can be precisely tuned, both the bandwidth Δλ and central wavelength λ0, where the backscattering is enhanced, can be very well controlled" [Lu, p. 4698].
One of ordinary skill in the art would have been motivated to select a less-than-15 nm bandwidth in the claim-9 system because it narrows the sensing enhancement and leaves adjacent telecom wavelengths available for out-of-band propagation. The claimed bandwidth is
a predictable implementation of the wavelength-control teachings of Kremp, Handerek, and Lu in the WDM/DWDM environment of Ip. Therefore, claim 11 would have been obvious.
Claim 13
With respect to claim 13, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 12 are taught by Ip, Kremp, Handerek and Westbrook, except claim 13 additionally recites that the enhanced scattering bandwidth is between approximately 1535 nm and approximately 1549 nm. This limitation is taught or at least rendered obvious for the same reasons discussed with respect to claim 4. However, within analogous art, Handerek teaches increased backscattering from 1535-1545 nm, which is within the claimed approximate region, and Lu teaches that bandwidth and center wavelength may be controlled.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Lu states: "Because the laser’s repetition rate can be precisely tuned, both the bandwidth Δλ and central wavelength λ0, where the backscattering is enhanced, can be very well controlled" [Lu, p. 4698].
One of ordinary skill in the art would have been motivated to use an enhanced scattering bandwidth between approximately 1535 nm and 1549 nm in the claim-12 system because that spectral placement allows an approximately 1550 nm telecom channel to remain outside the enhanced scattering band while sensing occurs in a nearby C-band region. Such spectral placement is a routine WDM design selection and is supported by Handerek’s 1535-1545 nm demonstration and Lu’s controllability teaching. Therefore, claim 13 would have been obvious.
Additionally, as explained for claim 4, because claim 13 uses “approximately,” Handerek’s 1535-1545 nm enhanced scattering band is a strong teaching within the claimed approximate 1535-1549 nm range, and Lu teaches that both bandwidth and center wavelength are precisely controllable. Extending or shifting the upper edge to approximately 1549 nm while keeping a 1550 nm telecom carrier outside the enhanced band would have been no more than a routine C-band wavelength-planning adjustment.
Claim 20
With respect to claim 20, for purposes of prior-art rejection only and without withdrawing any separate 35 U.S.C. §112(b) rejection, all limitations of claim 9 are taught by Ip, Kremp, Handerek and Westbrook, except claim 20 additionally recites that the telecom signal wavelength is at least one nanometer (1 nm) outside of the enhanced scattering bandwidth. However, within analogous art, Handerek teaches an enhanced scattering bandwidth from 1535-1545 nm and teaches 1550 nm as an out-of-band wavelength. The 1550 nm
telecom/signal wavelength is therefore about 5 nm outside the 1545 nm upper edge of the enhanced scattering bandwidth, satisfying the claimed at-least-1-nm spacing.
Handerek states: "The in band OFDR trace shows a scattering signal approximately 15 dB above the base Rayleigh scattering level of the fibre. Fig. 1(b) shows a spectrum extracted from a 2 m section of an OFDR trace recorded in the OBR standard mode. While this mode on the OBR measures at most 70 m of fibre, it can still be used to estimate the enhanced scattering bandwidth of the fibre. This is observed to be from 1535-1545 nm" [Handerek, p. 2, Section 2, FIG. 1(b)].
Handerek states: "Fig. 1(a) shows OFDR traces taken at 1540 nm, within the scattering band of the fibre, and at 1550 nm, outside the scattering bandwidth" [Handerek, p. 1, Section 2, FIG. 1(a)].
Additionally, Ip teaches reserving spectral holes and using WDM/DWDM spectral separation to permit communication and sensing coexistence, and Lu teaches that bandwidth and center wavelength may be controlled.
Ip states: "In this experimental field trial, the DFOS application coexisted with full C-band 38-Tb/s transmission of dense WDM (DWDM) traffic where each of the 92x48-Gbaud channels carried PS144QAM at net data rate ≥400-Gb/s and average spectral efficiency (SE) of 8.3 b/s/Hz. To allow simultaneous DOFS, we reserve a spectral hole of three 50-GHz channels in FIG. 7" [Ip, ¶ [0057], p. 14].
Lu states: "Because the laser’s repetition rate can be precisely tuned, both the bandwidth Δλ and central wavelength λ0, where the backscattering is enhanced, can be very well controlled" [Lu, p. 4698].
Westbrook additionally teaches that the enhanced scattering can be measured in a 10-nm band and that the out-of-band measurement is close to the Rayleigh scatter level of the unprocessed fiber, further supporting a telecom carrier placed outside the enhanced band.
One of ordinary skill in the art would have been motivated to place the telecom signal wavelength at least 1 nm outside the enhanced scattering bandwidth because the whole design objective in the combined system is to preserve telecom signal quality while improving sensing. Ip teaches spectral separation and WDM/DWDM coexistence; Kremp teaches that enhanced scattering can be confined to a selected band; Handerek demonstrates the specific 1535-1545 nm enhanced band and 1550 nm out-of-band Rayleigh-level scattering; and Lu teaches center/bandwidth control. The at-least-1-nm spacing is therefore a routine wavelength-planning choice that predictably avoids the enhanced scattering band while leaving the sensing enhancement available. Therefore, claim 20 would have been obvious.
It is noted that any citations to specific, pages, columns, lines, or figures in the prior art references and any interpretation of the reference should not be considered to be limiting in any way. A reference is relevant for all it contains and may be relied upon for all that it would have reasonably suggested to one having ordinary skill in the art. See MPEP 2123.
Conclusion
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/MOHAMMED ABDELRAHEEM/Examiner, Art Unit 2635
/DAVID C PAYNE/Supervisory Patent Examiner, Art Unit 2635
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