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 January 27, 2025, 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 1-6 are pending in this application and are under examination in this Office Action. No claims have been allowed.
Drawings
The drawings are objected to under 37 CFR 1.84(p)(4) and MPEP § 608.02(e) because the same spectrum-measuring element is inconsistently designated in the drawings and the written description. Figures 3 and 8 identify the spectrum-measuring lifeline as “OPA,” while Figures 1 and 7 and the written description identify OSA 13 as the optical spectrum analyzer / spectrum information acquirer that measures the signal spectrum and supplies spectrum information.
Specifically, paragraphs [0014], [0019], [0054], and [0057] describe OSA 13 as performing the corresponding spectrum-measurement function.
As drawn, Figures 3 and 8 are inconsistent with the remainder of the disclosure. The designation must be corrected so that the same element is identified consistently throughout the application. No new matter should be entered.
Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application.
Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as “amended.” If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency.
Additional replacement sheets may be necessary to show the renumbering of the remaining figures.
Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either “Replacement Sheet” or “New Sheet” pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
Specification
The specification is objected to because it contains inconsistent terminology and reference designations that render portions of the disclosure unnecessarily unclear. Correction is required.
Regarding paragraph [0043],
Paragraph [0043] states that the second embodiment is a configuration in which optical transmission system 100 “does not include an OPA.” The same paragraph then explains that optical transmission system 100a differs from optical transmission system 100 because “the OSA 13 is not provided.” In the remainder of the disclosure, OSA 13 is identified as the optical spectrum analyzer / spectrum information acquirer. Thus, “OPA” is inconsistent with the disclosed component designation and should be corrected if “OSA” was intended.
Regarding paragraphs [0044] and [0045],
Paragraph [0044] correctly introduces optical receiver 12a for the second embodiment but subsequently states that “the optical receiver 12 acquires quality information.” Paragraph [0045] likewise refers to quality information and spectrum information output from “the optical receiver 12,” although the second embodiment identifies the receiver as optical receiver 12a. The reference designation should be made consistent.
Regarding paragraphs [0050]-[0052] and [0056],
Paragraph [0050] introduces filter calculation unit 14b but subsequently states that “the filter calculation unit 14 sets the calculated filter.” Paragraphs [0051] and [0052] refer to optical transmitter 10 while describing optical transmission system 100b, which is expressly defined as including optical transmitter 10b. Paragraph [0056] again refers to an optical signal transmitted by optical transmitter 10 after identifying optical transmitter 10b as the transmitter in the third embodiment. These reference designations should be corrected for consistency. Any amendment must not introduce new matter.
Claim Objections
Claims 1, 2, 4, 5, and 6 are objected to because of informalities. Appropriate correction is required.
Regarding claim 1,
Claim 1 recites “an optical receiver configured to receive the optical signal equalized by the equalizer and acquires quality information” and later recites “a filter generator configured to generate a filter ... and sets the filter in the equalizer.” These clauses lack parallel grammatical construction. The phrases should be corrected, for example, to recite “configured to receive ... and acquire” and “configured to generate ... and set,” or otherwise be amended to provide proper grammatical form without changing the scope of the claim.
Regarding claim 2,
Claim 2 terminates with a comma rather than a period. Each claim must end with a period. See MPEP § 608.01(m). Correction is required.
Regarding claim 4,
Claim 4 contains improper punctuation and spacing in the phrase “according to claim 1 ,wherein.” The punctuation and spacing should be corrected.
Regarding claim 5,
Claim 5 twice recites “an equalization processing.” The grammatical form should be corrected, for example, to “equalization processing,” if that is what applicant intends.
Regarding claim 6,
Claim 6 recites “generating, by a filter generator a filter.” The parenthetical phrase lacks a comma after “filter generator.” The grammatical and punctuation defect should be corrected, for example, to “generating, by a filter generator, a filter,” if that is what applicant intends.
Claim Rejections - 35 U.S.C. § 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.
Claim 4 is 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 4,
Claim 4 recites that “the filter generator generates the filter including a frequency width to be compensated and a coefficient for achieving an optimum signal quality and sets the filter in the equalizer.”
The phrase “a coefficient for achieving an optimum signal quality” does not provide an objective boundary for determining what coefficient satisfies the claim. Claim 4 does not identify the signal-quality metric by which “optimum” is determined, the comparison standard against which the quality is evaluated, or the criterion that establishes when the optimum has been reached.
The written description identifies multiple materially different signal-quality measures, including BER, Q value, SNR, FEC number, and an adaptive-equalizer error signal. The written description also identifies multiple different determination criteria for an optimum frequency width / coefficient: a value whose difference from a predetermined signal-quality value is less than a threshold, the candidate value producing maximum signal quality, or a searched value producing optimum signal quality within a predetermined range.
The specification further states that other criteria may be used.
Because different disclosed quality metrics and different disclosed optimization criteria can produce different coefficient values, and because the claim does not identify which metric or criterion defines “optimum signal quality,” it is unclear where the boundary of the claimed coefficient lies.
The disclosure does not resolve the ambiguity because it expressly presents the listed criteria as alternatives and leaves open unspecified “other criteria.”
Accordingly, one of ordinary skill in the art would not be able to determine with reasonable certainty which coefficients fall within and outside the scope of claim 4.
Therefore, the metes and bounds of claim 4 are not reasonably certain, and claim 4 is indefinite under 35 U.S.C. 112(b).
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 nonobviousness, if present.
The key to supporting a rejection under 35 U.S.C. § 103 is a clear articulation of the reason or reasons why the claimed invention would have been obvious, with an articulated reasoning having a rational underpinning.
The analysis below identifies the teachings relied upon for each limitation and states a claim-specific reason for the proposed combination.
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, 2, and 6 are rejected under 35 U.S.C. § 103 as being unpatentable over Nakajima et al. (US20010019436A1) in view of Liu et al. (US20030020989A1).
Claim 1
Nakajima expressly teaches the basic optical transmission architecture recited in claim 1: a transmitting station, a receiving station, an optical transmission path between them, and one or more optical tunable filters placed in that optical path.
Nakajima states: “As shown in the diagram, the system is configured such that a transmitting Station (TX) 11 and a receiving station (RX) 12 are provided as terminal stations, and an optical fiber 21 as an optical transmitting path, and m repeaters 22 (22-1 to 22-m) and n optical tunable filters 23 (23-1 to 23-n) are placed between the transmitting and receiving Stations 11 and 12. Each of the optical tunable filters 23 is a filter whose transmission factor versus wavelength characteristic can be controlled variably.” [Nakajima, ¶¶ [0068]-[0069], FIG. 1]
With respect to the limitation “an optical transmitter configured to transmit an optical signal,” Nakajima expressly identifies transmitting station 11a and its optical senders as generating optical signals of respective wavelengths and multiplexing them for transmission over the optical fiber.
Nakajima teaches: “In FIG. 5, a block 110 (110-1) is arranged to produce an optical Signal of wavelength λ1, then perform pre-emphasis control on it and output the pre-emphasis controlled optical Signal to an arrayed waveguide grating (AWG) 111 and comprises an optical sender (OS) 110a with forward error correction (FEC), a post-amplifier (POST AMP) 110b, and an attenuator (ATT) 110c. More specifically, the optical sender 110a with FEC produces an optical signal of wavelength λ1, then performs FEC on it and outputs the resulting Signal to the post-amplifier 110b. ... The AWG 111 multiplexes the optical signals of wavelengths λ1, λ2, ... λn from the blocks 110-1, 110-2, ... and 110-n and outputs the multiplexed optical Signal to the optical coupler 112, which in turn sends the multiplexed optical Signal over the optical fiber 32.” [Nakajima, ¶¶ [0085]-[0088], FIG. 5]
With respect to the limitation “an equalizer configured to equalize the optical signal transmitted from the optical transmitter in an optical domain,” Nakajima teaches optical tunable filter 23 as an all-optical, wavelength-dependent filter positioned in the transmission path, whose optical transmission characteristic is varied by a controller.
The equalization therefore occurs on the optical signal itself, before reception and optical-to-electrical data recovery.
Nakajima states: “The optical tunable filter is composed of a filter section 231, a controller 232, a photodiode (PD) 233, and an optical coupler (CPL) 234. The filter section 231 is a filter that has its transmission factor versus wavelength characteristic varied by the controller 232. ... The photodiode 233 subjects the received filter control Signal to opto-electrical conversion and then outputs the resulting electrical filter control Signal to the controller 232, which in turn varies the transmission factor versus wavelength characteristic of the filter Section 231 in accordance with the input filter control signal. The filter section 231 then outputs the received optical Signal in accordance with the controlled transmission factor versus wavelength characteristic, which is then sent to the receiving Station 12a over the optical fiber 32.” [Nakajima, ¶¶ [0081]-[0083], FIG. 4]
With respect to the limitation “an optical receiver configured to receive the optical signal equalized by the equalizer and acquires quality information regarding quality of the received optical signal,” Nakajima expressly measures Q factor and BER at the receiving station after the optical signal has traversed the optical tunable filter and the transmission path.
Nakajima teaches: “The receiving station 12a measures the OSNR and Q factor of a received signal in the measurement Section 51 and then sends a filter control signal for the optical filter 23 over the optical fiber 31 to the transmitting station 11a so that variations in the OSNR and Q factor are eliminated. The transmitting Station 11a sends the received filter control signal to the optical tunable filter 23 over the optical filter 32. In the optical tunable filter 23, its transmission factor versus wavelength characteristic is controlled. The filter control signal is also carried in the overhead as shown in FIG. 7A by way of example.” [Nakajima, ¶ [0077], FIG. 3]
Nakajima further states: “The Q factor monitor 125 measures the Q factor of the optical Signal of wavelength λi from the optical coupler 120d and provides the measurement to a controller 127. The BER measurement device 126 measures the bit error rate of the optical signal of wavelength λi received by the optical receiver 120e and provides the measurement to the controller 127. The bit error rate can be measured readily by counting the number of error corrections by FEC.” [Nakajima, ¶ [0097], FIG. 6]
With respect to the limitation “a filter generator configured to generate a filter to be used for equalization processing on the basis of spectrum information of the optical signal equalized by the equalizer and the quality information and sets the filter in the equalizer,” Nakajima provides a controller coupled to an optical spectrum analyzer, Q-factor monitor, and BER monitor. The controller computes the optical-filter transmission characteristic from those measurements and produces the filter-control signal that sets the optical tunable filter.
Nakajima states: “The optical coupler 123 provides the optical signal from the optical coupler 121 to an optical Spectrum analyzer 128 and a photodiode 129. The analyzer measures the power and OSNR of the input optical signal of wavelength λi and provides the measurements to the controller 127. ... Based on the Q factor (or the bit error rate) and the OSNR of the optical signal of wavelength λi input from the Q factor monitor 125, the BER measurement device 126, and the spectrum analyzer 128, the controller 127 computes the amount of pre-emphasis on the optical signal of wavelength λi performed by the transmitting Station 11a and the transmission factor for the optical Signal of wavelength λi in the optical tunable filter 23 so that the transmission characteristic of the optical Signal of wavelength λi is homogenized and optimized. Based on the computational results, the controller 127 produces control signals (a pre-emphasis control signal for controlling the amount of pre-emphasis for the optical Signal of wavelength λi in the transmitting Station 11a and a filter control Signal for controlling the transmission factor versus wavelength characteristic of the optical tunable filter 23) ... .” [Nakajima, ¶¶ [0098]-[0100], FIG. 6]
Although Nakajima already uses an optical spectrum analyzer in the receiving-side feedback loop, to the extent that applicant argues that Nakajima does not expressly describe using the complete measured spectrum of the already-equalized optical signal as the filter-generation input, Liu expressly teaches that precise feature in the same optical-equalization art.
Liu expressly teaches: “Further described is an optical system which is operable to receive an optical input signal, the optical system comprising an optical signal input, an optical signal output, a plurality of harmonic filter stages driven by a plurality of control voltages, and an optical path optically connecting the optical Signal output to the optical Signal input through the plurality of harmonic filter stages. The plurality of harmonic filter stages are operable to selectively attenuate by wavelength the optical Signal carried on the optical path to thereby generate an equalized optical Signal at the optical Signal output. Also provided is an optical spectrum analyzer connected to the optical Signal output and operable to receive the equalized optical Signal and to measure the optical power spectrum of the equalized optical Signal. A controller is further in communication with and operable to control the plurality of harmonic filter stages, the controller further in communication with the optical spectrum analyzer whereby the controller is operable to receive data representing a measurement of the optical power spectrum of the equalized optical Signal and to compare that measured optical power spectrum to a target power spectrum. Based on the comparison, the controller adjusts the plurality of harmonic filter stages such that the attenuation imposed by the plurality of harmonic filters is adjusted to cause the power spectrum of the equalized optical Signal to more closely approximate the target power spectrum.” [Liu, ¶ [0031], FIGS. 6-8]
Liu further explains the actual closed-loop generation and setting of the equalizer: “During step 820, the actual output power spectrum (as opposed to the target output power spectrum) from the equalizer 125 is determined. The task of the control algorithm is then to control the equalizer 125 in order to make the actual output power spectrum as close as possible to the target output power spectrum. Thus, at Step 825, the target and actual output power spectra are compared. The comparison preferably breaks down the difference between the actual transfer function and the target transfer function into harmonic component values, Such as Fourier harmonic component amplitude and phase constants. The control algorithm will then at step 830 calculate desired phase and amplitude shifts for each of these components Such that the actual output power Spectrum more closely matches the target output power spectrum. When the control algorithm operates a multistage optical equalizer 125, it then controls those multiple Stages according to the harmonic component value changes calculated in step 830. This is done at step 835 by dynamically controlling the control Voltages to the individual Stage filters 605 (1...N) within the equalizer 125.” [Liu, ¶¶ [0097]-[0098], FIG. 8]
One of ordinary skill in the art would have been motivated to combine Nakajima with Liu because both references are directed to adaptive optical equalization in optical communication systems, both use wavelength-dependent optical filters/equalizers, and both use measured characteristics of the optical signal as feedback to a controller that changes the equalizer transfer characteristic. Nakajima already places an optical spectrum analyzer and quality monitors in the receiving-side feedback path and uses the resulting information to calculate an optical-filter control signal. Liu teaches the complementary and more explicit known technique of measuring the actual output power spectrum of the equalized optical signal itself, comparing that spectrum with a desired spectrum, calculating the necessary filter-function changes, and dynamically applying those changes to the optical filter stages.
A person having ordinary skill in the art would have recognized that applying Liu’s output-spectrum feedback technique to Nakajima’s existing OSA/Q/BER-controlled optical tunable filter would provide a richer and more direct measurement of the wavelength-dependent distortion remaining after optical equalization. The modification would permit the controller to use both received-signal quality information and the measured post-equalization spectrum when calculating the filter characteristic, thereby improving the ability of the known closed loop to converge toward the desired equalized response. This is not a change in the principle of operation of Nakajima; the system would still transmit an optical signal, optically equalize it with a tunable optical filter, measure the received signal, calculate an updated filter characteristic, and set that characteristic in the optical equalizer.
The proposed combination would have involved no more than using a known spectrum-feedback technique of Liu in the known feedback-controlled optical equalizer of Nakajima to obtain the predictable result expressly taught by both references: improved wavelength-dependent equalization of an optical transmission signal. Both references disclose controllers, optical filters, optical spectrum measurement, and iterative adjustment; therefore, a person of ordinary skill would have had a reasonable expectation that the measurements and control calculation taught by Liu could be incorporated into Nakajima’s controller without undue experimentation.
Accordingly, the combined teachings of Nakajima and Liu teach every limitation of claim 1, including an optical transmitter, optical-domain equalization of the transmitted optical signal, receipt and acquisition of received-signal quality information, acquisition of spectrum information for the equalized optical signal, generation of the equalizer filter based on both spectrum and quality information, and setting the generated filter in the optical equalizer.
Claim 2
With respect to claim 2, all limitations of claim 1 are taught by Nakajima and Liu, as set forth above, except wherein claim 2 additionally expressly teaches a spectrum information acquirer configured to acquire spectrum information of the optical signal equalized by the equalizer, and that the filter generator uses the spectrum information acquired by that spectrum information acquirer together with the quality information. However, within analogous art, Nakajima itself expressly teaches the separately identifiable spectrum-information-acquiring structure, namely optical spectrum analyzer 128, and Liu independently teaches an optical spectrum analyzer coupled to the equalizer output for acquisition of the equalized-signal power spectrum.
Nakajima states: “The optical coupler 123 provides the optical signal from the optical coupler 121 to an optical Spectrum analyzer 128 and a photodiode 129. The analyzer measures the power and OSNR of the input optical signal of wavelength λi and provides the measurements to the controller 127.” [Nakajima, ¶ [0098], FIG. 6]
Nakajima further identifies the spectrum-information acquirer as part of the measurement structure: “That is, in the present embodiment, the measurement section 51 shown in FIG. 3 is constructed from the Q factor monitor 125, the BER measurement device 126 and the optical Spectrum analyzer 128, and the controller 127. Further, the Q factor monitor 125, the BER measurement device 126, the optical spectrum analyzer 128 correspond to the transmission characteristic measurement means and the controller 127 corresponds to the transmission characteristic control means.” [Nakajima, ¶ [0100], FIG. 6]
Liu independently teaches the same separation between the spectrum acquisition structure and controller: “Also provided is an optical spectrum analyzer connected to the optical Signal output and operable to receive the equalized optical Signal and to measure the optical power spectrum of the equalized optical Signal. A controller is further in communication with and operable to control the plurality of harmonic filter Stages, the controller further in communication with the optical spectrum analyzer whereby the controller is operable to receive data representing a measurement of the optical power spectrum of the equalized optical Signal and to compare that measured optical power spectrum to a target power spectrum.” [Liu, ¶ [0031]]
One of ordinary skill in the art would have understood Nakajima’s optical spectrum analyzer 128 to be the claimed “spectrum information acquirer” because it is a distinct optical measurement component that acquires wavelength-dependent power/OSNR information and supplies that information to the controller that generates the filter-control signal. Liu makes the correspondence even more explicit by placing the optical spectrum analyzer directly at the optical equalizer output and using the measured output spectrum as controller input.
To the extent a modification is considered necessary, one of ordinary skill in the art would have been motivated to configure Nakajima’s spectrum analyzer in the output-monitoring arrangement taught by Liu because the purpose of both devices is the same: acquire wavelength-domain information used to control an adaptive optical filter. Doing so would merely select a known, directly compatible location for a known spectrum-measurement device in a known feedback loop and would predictably provide spectrum information representing the signal after the optical equalizer. The quality-information path of Nakajima would remain unchanged, so the controller would use both the separate spectrum-acquirer output and the Q/BER information as recited.
Accordingly, the additional limitation of claim 2 would have been obvious over the same Nakajima/Liu combination for the reasons above.
Claim 6
Claim 6 recites the method counterpart of the claim-1 optical transmission architecture. Nakajima and Liu teach each claimed method step through operation of the apparatuses discussed above.
With respect to “transmitting, by an optical transmitter, an optical signal,” Nakajima teaches optical senders producing wavelength channels and AWG 111 multiplexing those optical signals for transmission over optical fiber 32.
Nakajima states: “The AWG 111 multiplexes the optical signals of wavelengths λ1, λ2, ... λn from the blocks 110-1, 110-2, ... and 110-n and outputs the multiplexed optical Signal to the optical coupler 112, which in turn sends the multiplexed optical Signal over the optical fiber 32.” [Nakajima, ¶ [0088], FIG. 5]
With respect to “equalizing, by an equalizer, the transmitted optical signal in an optical domain,” Nakajima teaches controller 232 varying the transmission-factor-versus-wavelength characteristic of optical filter section 231 and that filter section outputting the received optical signal according to the controlled characteristic.
Nakajima states: “The photodiode 233 subjects the received filter control Signal to opto-electrical conversion and then outputs the resulting electrical filter control Signal to the controller 232, which in turn varies the transmission factor versus wavelength characteristic of the filter Section 231 in accordance with the input filter control signal. The filter section 231 then outputs the received optical Signal in accordance with the controlled transmission factor versus wavelength characteristic, which is then sent to the receiving Station 12a over the optical fiber 32.” [Nakajima, ¶ [0083], FIG. 4]
With respect to “receiving, by an optical receiver, the equalized optical signal and acquiring quality information regarding quality of the received optical signal,” Nakajima teaches receiving station 12a, Q-factor monitor 125, and BER measurement device 126 as quoted above.
Nakajima states: “The Q factor monitor 125 measures the Q factor of the optical Signal of wavelength λi from the optical coupler 120d and provides the measurement to a controller 127. The BER measurement device 126 measures the bit error rate of the optical signal of wavelength λi received by the optical receiver 120e and provides the measurement to the controller 127.” [Nakajima, ¶ [0097], FIG. 6]
With respect to “generating, by a filter generator, a filter to be used for equalization processing on the basis of spectrum information of the equalized optical signal and the quality information and setting the filter in the equalizer,” Nakajima computes the transmission characteristic from Q/BER and OSA information and generates a filter-control signal, while Liu expressly teaches measuring the actual output spectrum of the equalized signal and calculating/applying optical-filter adjustments from that spectrum.
Nakajima teaches: “Based on the Q factor (or the bit error rate) and the OSNR of the optical signal of wavelength λi input from the Q factor monitor 125, the BER measurement device 126, and the spectrum analyzer 128, the controller 127 computes ... the transmission factor for the optical Signal of wavelength λi in the optical tunable filter 23 so that the transmission characteristic of the optical Signal of wavelength λi is homogenized and optimized. Based on the computational results, the controller 127 produces ... a filter control Signal for controlling the transmission factor versus wavelength characteristic of the optical tunable filter 23.” [Nakajima, ¶¶ [0099]-[0100], FIG. 6]
Liu states: “During step 820, the actual output power spectrum ... from the equalizer 125 is determined. The task of the control algorithm is then to control the equalizer 125 in order to make the actual output power spectrum as close as possible to the target output power spectrum. ... The control algorithm will then at step 830 calculate desired phase and amplitude shifts for each of these components Such that the actual output power Spectrum more closely matches the target output power spectrum. ... This is done at step 835 by dynamically controlling the control Voltages to the individual Stage filters 605 (1...N) within the equalizer 125.” [Liu, ¶¶ [0097]-[0098], FIG. 8]
One of ordinary skill in the art would have been motivated to perform Nakajima’s disclosed transmission/equalization/measurement/control sequence using Liu’s explicit output-spectrum control calculation for the same reasons discussed for apparatus claim 1.
Method claim 6 does not require a materially different architecture; it recites the operational use of that architecture.
Nakajima already teaches transmitting, optically filtering/equalizing, receiving, measuring Q/BER/OSNR, calculating a filter characteristic, and applying a filter-control signal.
Liu expressly supplies the use of the measured spectrum of the equalized output as a calculation input.
Implementing Liu’s spectrum-comparison step during Nakajima’s existing feedback cycle would have been a predictable process improvement: the receiver/controller obtains a more direct description of residual spectral distortion and calculates an optical-filter adjustment that is then applied to the tunable optical filter.
Because both references use iterative feedback to the same class of optical equalizer, the combination would have required only routine programming/control changes and would have had a reasonable expectation of success.
Accordingly, claim 6 would have been obvious over Nakajima in view of Liu.
Claim 3 is rejected under 35 U.S.C. § 103 as being unpatentable over Nakajima et al. in view of Liu et al., and further in view of Ge et al. (US 2020/0036446 A1).
Claim 3
With respect to claim 3, all limitations of claim 1 are taught by Nakajima and Liu, as set forth above, except wherein claim 3 additionally expressly teaches that the optical receiver itself further acquires spectrum information of the optical signal equalized by the equalizer and the filter generator uses the spectrum information acquired by the optical receiver together with the quality information. However, within analogous art, Ge expressly teaches incorporating the spectrum-acquisition function into the optical receiver itself.
Ge states: “The optical receiver 20 further includes a capture unit 31, a spectrum detector 32, and a correction information generator 33. The capture unit 31 acquires a digital signal output from the ADC 23. This digital signal represents electric field information of a received optical signal.” [Ge, ¶ [0049], FIG. 4]
Ge further states: “The spectrum detector 32 detects a reception spectrum based on a digital signal acquired by the capture unit 31. In particular, the spectrum of a received optical signal is detected. According to the reception spectrum detected by the spectrum detector 32, the correction information generator 33 generates correction information for correcting the shape of the transmission spectrum of the optical signal in the source device that is the source of the optical signal (i.e., the optical transmitter 10 implemented in the optical transceiver 1). In this example, the correction information indicates tap coefficients of the FIR filter 13 that performs pre-emphasis for an optical signal in the optical transmitter 10. That is, the correction information generator 33 calculates tap coefficients to be set for the FIR filter 13.” [Ge, ¶ [0051], FIG. 4]
Ge additionally teaches receiver-side delivery and setting of the calculated filter coefficients: “The tap coefficients are reported to the source device that is the source of the optical signal. For example, when an optical signal is transmitted from the optical transceiver 1 to the optical transceiver 2 ... the optical receiver 20 implemented in the optical transceiver 2 may calculate the tap coefficients. In this case, the optical transceiver 2 transmits the calculated tap coefficients to the optical transceiver 1. Then, the tap coefficients are set for the FIR filter 13 in the optical transceiver 1.” [Ge, ¶ [0052]]
Ge further explains that the reception spectrum can be output by the receiver for coefficient generation: “The optical receiver 20 does not necessarily need to include the correction information generator 33. In this case, information indicating a reception spectrum detected by the spectrum detector 32 is transmitted to another device (e.g., source device or SDN). The other device calculates tap coefficients based on the reception spectrum. Then the tap coefficients are given to the FIR filter 13 of the source device.” [Ge, ¶ [0060]]
One of ordinary skill in the art would have been motivated to incorporate Ge’s receiver-integrated spectrum detector into the Nakajima/Liu system because Nakajima already obtains received-signal spectrum information through a dedicated OSA and uses that information for feedback control, while Ge teaches a known alternative in which spectrum information is calculated directly inside the receiver from digitized electric-field samples.
The references therefore address the same measurement problem using compatible implementations.
The modification would have predictably reduced or eliminated the need for a separate optical-spectrum-analyzer hardware path while preserving the same spectrum-feedback function. In the combined system, Ge’s capture unit and spectrum detector would process the signal received after Nakajima’s optical tunable filter; consequently, the reception spectrum acquired by the receiver would represent the optical signal after the claimed optical-domain equalization.
Nakajima’s Q/BER quality-information path and Liu’s post-equalization spectrum-based filter adjustment would remain available to the same controller/filter generator.
A person of ordinary skill would have had a reasonable expectation of success because Ge expressly teaches FFT-based reception-spectrum detection from receiver samples and generation of filter coefficients from that spectrum, while the base combination already requires digital/control processing of measured optical characteristics.
Integrating the known receiver-spectrum function is therefore a predictable substitution of one known spectrum-acquisition implementation for another, not a change in the principle of optical equalization.
Accordingly, claim 3 would have been obvious over Nakajima in view of Liu and further in view of Ge.
Claim 4 is rejected under 35 U.S.C. § 103 as being unpatentable over Nakajima et al. in view of Liu et al., and further in view of Childers et al. (US 2009/0097849 A1).
Claim 4
With respect to claim 4, all limitations of claim 1 are taught by Nakajima and Liu, as set forth above, except wherein claim 4 additionally expressly teaches that the filter generator generates the filter including a frequency width to be compensated and a coefficient for achieving an optimum signal quality and sets that filter in the equalizer. However, within analogous art, Childers expressly teaches adaptive control of an optical-filter bandwidth based on BER/Q feedback, while Nakajima expressly teaches an optimum control coefficient/allocation selected according to maximum Q-factor performance.
Childers teaches the frequency-width/bandwidth portion of the limitation: “The performance of the BW and wavelength tunable optical filter 10 is illustrated by the graph 11 of FIG. 1. This graph 11 illustrates that both the BW 12 and the center wavelength 13 of the BW and wavelength tunable optical filter 10 are independently adjustable. The BW and wavelength tunable optical filter 10 is operable for receiving a plurality of wavelengths ... and passing only one or more selected wavelengths.” [Childers, ¶ [0021], FIG. 1]
Childers further teaches use of signal-quality feedback to adapt that frequency width: “The RX 18 includes a BER and/or signal quality (Q) monitoring module 32, using forward error correction (FEC) coding or the like, operable for providing feedback to the BW and wavelength tunable optical filter 10, such that the BW adaptive optical filter is truly BW adaptive.” [Childers, ¶ [0023], FIG. 4]
Childers expressly characterizes the process as optimization: “The methodologies of the present invention are very robust adaptively optimizing the BW (and performance) of the RXs used. This is especially important in dynamic reconfigurable WDM systems, where imperfect filtering caused by uncertain numbers of ROADM nodes may now be compensated for on-the-fly.” [Childers, ¶ [0027]]
The claimed “coefficient for achieving an optimum signal quality” is additionally taught by Nakajima’s optimization coefficient X/Xopt. Nakajima precalculates an optimum allocation between filter control and transmitter control, searches multiple filter percentages, measures average Q, and selects the percentage when average Q is maximum.
Nakajima states: “The transmission characteristic control unit, in equalizing the transmission characteristics, precalculates the optimum allocation of control between the controlled variable of the pre-emphasis and the controlled variable of the wavelength characteristic of the optical tunable filter (i.e., the allocation that allows pre-emphasis control and the wavelength characteristic control to be carried out most effectively) and controls the pre-emphasis and the wavelength characteristic according to the optimum allocation. By doing so, not only can the transmission characteristics be equalized, but also, the optimum transmission characteristics can be obtained.” [Nakajima, ¶ [0023]]
Nakajima further teaches how the optimum coefficient is selected: “The process of calculating the optimum allocation may be performed, assuming that the transmission factors of the optical tunable filter to which reference is made are 100%, by controlling the amounts of pre-emphasis in the transmitting Station to equalize the second transmission characteristic values each time the transmission factors of the filter are reduced by a percentage, calculating the average of the equalized second transmission characteristic values over all wavelengths each time the transmission factors of the filter are reduced by the percentage, and using the percentage of a reduction in the transmission factors when the average is a maximum as the optimum allocation.” [Nakajima, ¶ [0028]]
Nakajima further identifies the quality criteria used in the optimization: “The first transmission characteristic values may be optical signal to noise ratios (OSNR), and the second transmission characteristic values may be Q factors. Otherwise, the first transmission characteristic values may be optical signal to noise ratios (OSNR), and the second transmission characteristic values may be bit error rates (BER).” [Nakajima, ¶ [0034]]
One of ordinary skill in the art would have been motivated to incorporate Childers’s bandwidth-adaptive optical-filter teaching into the optical equalizer of the Nakajima/Liu combination because all three references seek to optimize optical transmission quality by adaptively controlling an optical filter. Nakajima adjusts a wavelength-dependent optical-filter characteristic from received Q/BER/OSNR information; Liu adjusts an optical equalizer from the measured output spectrum; and Childers teaches that the frequency bandwidth of the optical filter itself is an adjustable filter parameter and should be adapted from BER/Q feedback.
A person of ordinary skill would have recognized filter bandwidth as a frequency-width parameter defining the portion of the optical spectrum passed/compensated by the filter. Selecting that width as another adjustable parameter in Nakajima’s controller would have been a straightforward extension of the already-variable wavelength-dependent filter characteristic.
Childers expressly demonstrates that adjusting the width improves OSNR/BER performance and that BER/Q feedback provides a practical basis for choosing the width.
The coefficient portion likewise would not have required invention.
Nakajima expressly searches a percentage/control-allocation variable and chooses the value when average Q is maximum; thus, Nakajima’s X/Xopt is a coefficient selected for optimum signal quality.
Combining this known optimum coefficient with Childers’s known adaptive filter width would have yielded a filter defined by both a frequency width and an optimized coefficient, exactly as recited.
The controller would then set those generated filter parameters in the optical equalizer already present in the base combination.
The combination would have had a reasonable expectation of success because the cited references use the same measurable performance quantities Q, BER, OSNR, and optical spectrum to tune optical filtering parameters in feedback.
The modification merely applies known adjustable parameters to a known adaptive optical equalizer to obtain the predictable result of improved signal quality.
Accordingly, claim 4 would have been obvious over Nakajima in view of Liu and further in view of Childers.
Claim 5 is rejected under 35 U.S.C. § 103 as being unpatentable over Nakajima et al. in view of Liu et al., further in view of Zhou et al. (US 2020/0162165 A1), and further in view of Matsushita et al., “64-GBd PDM-256QAM and 92-GBd PDM-64QAM Signal Generation using Precise-Digital-Calibration aided by Optical-Equalization,” OFC 2019, W4B.2.
Claim 5
With respect to claim 5, all limitations of claim 1 are taught by Nakajima and Liu, as set forth above, except wherein claim 5 additionally expressly teaches that the filter generator generates the filter including a coefficient for performing equalization processing in an electrical domain in the optical transmitter and a coefficient for performing equalization processing in an optical domain in the equalizer, and sets the filter in both the optical transmitter and the equalizer. However, within analogous art, Nakajima already teaches a common controller producing separate transmitter-pre-emphasis and optical-filter control signals and an optimum allocation ratio between those controls; Zhou expressly teaches coefficient-based electrical FIR pre-equalization together with coefficient-based optical FIR equalization; and Matsushita expressly teaches optimizing the distribution of compensation between the digital/electrical and optical domains using an optimization parameter.
Nakajima teaches coordinated generation of transmitter-side and optical-filter control: “Based on the Q factor (or the bit error rate) and the OSNR of the optical signal of wavelength λi ... the controller 127 computes the amount of pre-emphasis on the optical signal of wavelength λi performed by the transmitting Station 11a and the transmission factor for the optical Signal of wavelength λi in the optical tunable filter 23 so that the transmission characteristic of the optical Signal of wavelength λi is homogenized and optimized. Based on the computational results, the controller 127 produces control signals (a pre-emphasis control signal for controlling the amount of pre-emphasis for the optical Signal of wavelength λi in the transmitting Station 11a and a filter control Signal for controlling the transmission factor versus wavelength characteristic of the optical tunable filter 23).” [Nakajima, ¶¶ [0099]-[0100], FIG. 6]
Nakajima also expressly teaches a coefficient-like split between the two domains of control: “Assuming the ratio representing the optimum allocation between a controlled variable of the transmission factor versus wavelength characteristic and a controlled variable of the amounts of pre-emphasis to be X to 1-X, a variation in the first transmission characteristic values by control of the wavelength characteristic according to the optimum allocation is the product of the difference and X, and a variation in the first transmission characteristic values by control of the amounts of pre-emphasis according to the optimum allocation is the product of the difference and 1-X.” [Nakajima, ¶ [0032]]
While Nakajima does not expressly require that the transmitter-side control be implemented as an electrical-domain FIR coefficient, Zhou expressly teaches that known implementation and, in the same transmitter, expressly teaches optical FIR coefficients.
Zhou teaches an electrical-domain coefficient: “Electrical pre-equalization with FIR filter coefficients [-0.2 1 -0.2] largely removes the ISI, but the ERpp is reduced from 5.76 dB to 4.6 dB, and the rms OMA is reduced from 0.75 mW to 0.65 mW.” [Zhou, ¶ [0038], FIGS. 8A-8B]
Zhou in the same paragraph teaches optical-domain filter coefficients: “The proposed 3-tap optical equalization technique with FIR tap (optical field) coefficients [0.36, -0.2, 0.36] allows effective ISI mitigation without degrading the rms OMA, although the ERpp is reduced to 4.3 dB due to the increased DC components.” [Zhou, ¶ [0038], FIGS. 8A-8B, PDF p. 18]
Zhou further expressly teaches joint use of the two equalization domains: “From the simulated results 901-906, one can see that the proposed one-tap optical equalization technique can achieve similar performance as the conventional three-tap electrical pre-equalization technique ... Although further increasing optical tap from one to two does not improve the performance by using optical equalization only, about 0.8 dB further performance gain can be achieved by using joint three-tap electrical and two-tap optical equalization (as compared to purely electrical pre-equalization).” [Zhou, ¶ [0039], FIGS. 9A-9C]
Zhou also states: “The method 1100 can optionally include electrically pre-equalizing the signal to be transmitted (optional stage 1110). In implementations employing electrical pre-equalization, the electrical pre-equalization can be accomplished with an electrical pre-equalizer 220 as previously described. Electrical pre-equalization can consist of amplifying a high-frequency component of an electrical signal to be modulated. Although electrical pre-equalization is optional to operation of the system, it can further improve the performance of the system when used in conjunction with the optical equalization techniques described herein.” [Zhou, ¶ [0046], FIG. 11]
The prior-art record further contains an especially close NPL teaching by Matsushita et al. that directly describes optimization of the distribution between digital/electrical and optical equalization using an optical-equalization parameter.
Matsushita states in the Abstract: “We propose to precisely distribute equalization for transceiver imperfection between digital and optical domain. 1.7- and 4.6-dB OSNR tolerance improvements were confirmed for PDM-256QAM and PDM-64QAM signals with net-rates of 793 and 851 Gbps/carrier.” [Matsushita, Abstract, p. 1]
Matsushita further teaches: “Another approach to mitigate the increase of PAPR is using both digital and optical compensation. Recently, a joint digital and optical pre-compensation optimized by BER for silicon photonics transceiver has been demonstrated ... In this paper we propose a precise-digital-calibration technique aided by optical-equalization.” [Matsushita, p. 1]
Matsushita expressly identifies the optimization parameter and setting of the optical filter: “Then, the amplitude trend of Tx compensation response ... with a parameter α to optimize the distribution of amplitude component between digital and optical equalization is set to an optical filter.” [Matsushita, p. 2]
Matsushita further reports the optimization process using signal quality: “The OSNR dependence of received Q-factor in back-to-back configuration for 64-GBaud PDM-256QAM, 88 and 92-GBd PDM-64QAM is shown in Fig. 3. The parameter α was varied to optimize the distribution of amplitude component between digital and optical equalization compensation.” [Matsushita, p. 2, FIG. 3]
One of ordinary skill in the art would have been motivated to implement Nakajima’s transmitter-side pre-emphasis control as the known electrical FIR pre-equalization taught by Zhou because both techniques compensate transmitter/system bandwidth limitations before optical transmission and are expressly coordinated with optical-domain compensation. Nakajima already calculates separate control quantities for transmitter pre-emphasis and for the optical tunable filter; Zhou provides a concrete coefficient-based implementation for those respective electrical and optical equalization functions.
A person of ordinary skill would likewise have been motivated to use Zhou’s optical FIR tap coefficients as the filter coefficients implementing the optical-domain portion of Nakajima’s tunable optical-filter response. Both references teach optical filtering to compensate frequency-dependent distortion, and Zhou expressly demonstrates that joint electrical/optical equalization improves performance over purely electrical equalization. Thus, configuring the common filter generator/controller to produce one set of coefficients for the transmitter electrical equalizer and another set of coefficients for the optical equalizer would have been a predictable implementation of Nakajima’s already-coordinated two-control architecture.
Matsushita further provides a direct reason to optimize how much compensation is assigned to each domain: the digital/electrical domain provides precise ripple compensation but raises PAPR, whereas optical equalization can suppress PAPR and provide broadband amplitude-trend compensation. Its parameter α is expressly varied to optimize the distribution using received Q/OSNR performance.
A skilled artisan applying this teaching to Nakajima’s X/(1-X) allocation and Zhou’s electrical/optical FIR coefficient implementations would have had a clear design path for generating the respective electrical and optical coefficients and setting them in the respective transmitter/equalizer blocks.
The references are strongly analogous: each concerns high-speed optical communication and compensation of wavelength/frequency-response impairments, each recognizes a tradeoff in allocating compensation, and each uses controllable equalization parameters to improve received signal quality.
The combination would preserve Nakajima’s overall architecture and feedback controller while implementing known coefficient-based electrical and optical equalizers and a known optimized distribution between them.
The expected result improved signal quality while distributing compensation between electrical and optical domains is expressly demonstrated by Zhou and Matsushita.
Accordingly, claim 5 would have been obvious over Nakajima in view of Liu, further in view of Zhou, and further in view of Matsushita.
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
