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 .
Claim Rejections - 35 USC § 112
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.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claim 7 rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Regarding claim 7:
The claim recites the limitation: “…each satisfying an expression: i + 4(j) for j of 0 to x-1 for each ith group from 1 to x.” The meaning of i, j, and x are unclear to the examiner. It is clear that they pertain to the channels, but they do not prescribe any means by which to associate j or i with a channel, or what x is signifies. The examiner has considered the claim in light of the specification but cannot determine with reasonable certainty what this expression defines and limits.
The examiner interprets this expression as an attempt to define a channel index mapping – to specify which channel indices fall within each of the x channel groups as a function of n and x.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all 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.
Claim(s) 1-5, and 10-12 is/are rejected under 35 U.S.C. 103 as being unpatentable over Zhang (Zhang et al., "Numerical Demonstration of 800 Gbps WDM Silicon Photonic Transmitter with Sub-decibel surface-normal optical interfaces", Micromachines, 2022) in view of Morrison (US20230072926A1).
Regarding claim 1:
Zhang discloses a photonic integrated circuit (PIC) with one or more banks of wave division multiplexing (WDM) source circuitry (Figure 1a, a WDM with a silicon “photonic transmitter” that is clearly a photonic integrated circuit), wherein each of the banks of WDM circuitry comprises:
light emitters to output optical signals at n consecutive wavelength channels having a channel spacing therebetween (Figure 1, an 8-channel WDM source on SOI is disclosed, channel spacings found in Table 4).
The light sources themselves are not explicitly defined or disclosed, and are just an implicit part of the disclosure; “As can be seen, the optical transmitter is characterized channel by channel using a tunable continuous wave laser,” section 4, as an example of the light source assumed.
A skilled artisan would be motivated to have the number of light sources correspond to the number of wavelength channels, as additional light sources would lead to underutilization of light sources, and too few light sources would lead to underutilization of wavelength channels. As such, n light emitters would be an obvious design choice.
a plurality of m of optical output couplers over the substrate (Zhang discloses a plurality of bidirectional grating couplers [BGCs, Figure 3] integrated on the silicon substrate, serving as optical output couplers that couple optical signal out of the PIC via surface-normal coupling. Figure 1a, Section 2.4);
a plurality of p multi-mode interference (MMI) couplers between the light emitters and the output couplers (Zhang discloses two, 1x4 angled multi-mode interference couplers, positioned structurally between the optical modulator/source section and the grating coupler output section of the WDM transmitter, Figure 1a, Section 1, Section 3. This is a direction structural read on the claimed plurality of p MMI couplers in the claimed position),
wherein each of the MMI couplers is to multiplex n/p optical signals received from a subset of the light emitters (Zhang discloses that two [p] 1x4 MMIs multiplex the 8 [n] wavelength channel signals to produce n/p = 8/2 = 4 signals per MMI coupler) and to output n/p multiplexed signals power split across each of n/p ports (Zhang discloses that each 1x4 MMI outputs 4 multiplexed signals across 4 output ports, corresponding to the n/p = 4; Figures 10c-10d show the transmission spectra of the two MMIs and the n/p = 4 signals in each);
and a plurality of optical interleavers between the MMI couplers and the output couplers (Abstract, “…interleaved AMMI WDM device.”; Figure 1a shows the two 1x4 AMMIs and a plurality of bidirectional grating based MZI optical interleaver structure), wherein the plurality of interleavers is:
coupled to receive n of the multiplexed signals (Zhang discloses that the optical interleaver receives the combined outputs of both 1x4 AMMIs, thereby receiving all n=8 multiplexed signals, Figure 1a) and
to output m composite signals, each of which includes all the n channels (there are m [2] bidirectional grating coupler output ports outputting the totality of the n [8] channel signals).
Zhang does not disclose a plurality of n light emitters specifically.
Morrison disclose a plurality of individual semiconductor laser sources (optical sources 101 are an array of laser sources; as in paragraph 71, they may be distributed feedback lasers 101 with a plurality of semiconductor optical amplifiers, making them semiconductor laser sources).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in Zhang under the teachings of Morrison to include a plurality of n light emitters. Zhang already necessitates the existence of light emitters, but Morrison solidifies the correspondence between the n light emitters and n wavelength channels. This may be accomplished using components (laser light sources), materials (semiconductor lasers), and routine design oversight (placement of parts) known to a skilled artisan, and would predictably result in a device which maximally utilizes the light sources available for the desired output with minimal loss in a cost efficient manner.
Regarding claim 2:
Zhang in view of Morrison discloses the PIC of claim 1, wherein:
n is at least 8 (Zhang, Figure 1a, 8 wavelength channels corresponding to n = 8 are disclosed);
Zhang is silent on the hybrid silicon laser, and teaches a channel spacing of exactly 200 GHz, not less than 200 GHz.
Morrison further teaches that:
each of the light emitters comprise a hybrid silicon laser (paragraph 30, “the optical sources may be fabricated on a platform comprising III-V semiconductor material”, laser sources comprising group III-V semiconductor materials are heterogeneously integrated onto a silicon photonics platform, the standard for hybrid silicon laser architectures);
and the channel spacing is less than 200 GHz (paragraph 27, channel spacings of 12.5, 25, 33, 50, 100, and 200 GHz are disclosed and present many possible channel spacings for such a device).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Morrison to include hybrid silicon laser light sources and channel spacings of less than 200 GHz. This may be accomplished using materials (group III-V lasers integrated into silicon) and placement techniques/design oversight (selection of channel spacings) known in the art, and would predictably result in a device with greater channel density and aggregate bandwidth.
Regarding claim 3:
Zhang in view of Morrison teaches the PIC of claim 2, wherein:
The WDM source circuitry comprises a single WDM transmitter block outputting to a plurality of m bidirectional grating couplers – i.e., one bank (k=1) with m output couplers (Figure 1a).
Zhang does not disclose a plurality of k banks, nor does it disclose k(m) total output couplers across multiple replicated bank structures.
Morrison teaches multiple source blocks feeding separate PICs (Figure 7, PICs 702a and 702b). This relationship constitutes one set of laser sources feeding two PICs, instead of the claimed two WDM source banks on a single PIC.
However, the key teaching here is that routing multi-wavelength source outputs to multiple independent optical processing paths is taught and present in both the instant invention and the prior art – splitting a laser source array across multiple output bearing circuits is a known and practiced architecture.
A skilled artisan would use this teaching in the invention of claim 2 as follows: Zhang teaches a WDM source unit cell with n light emitters, p MMI couplers, an MZI interleaver, m output couplers, all on a SOI substrate as claimed. This constitutes one bank. Zhang’s explicit design goal is high bandwidth (800 Gbps, Title) aggregated through one bank.
A skilled artisan would recognize that higher bandwidth may be achieved by scaling up, as motivated by Morrison. Morrison’s Figure 7 shows that a single laser array can drive two independent optical processing paths simultaneously, where each output port of each dual-output laser source (708) feeds a separate PIC (702a/b). This teaches that the resulting outputs are independent and parallel, containing their own multiplexing elements (806a/b) as seen in Figures 8 and 9.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 2 above under the teachings of Morrison to route the output paths of Morrison’s Figure 7 in two integrated banks on a single SOI substrate, each bank being a replica of Zhang’s unit cell (MMI couplers into interleaver into output couplers), fed by its own subset of laser sources. The motivation is explicit: co-integration on a single substrate reduces packaging complexity, eliminates chip-to-chip coupling loss, and leverages the existing 300mm SOI fabrication platform used in Zhang. This predictably results in a device where k banks with m bidirectional grating couplers per bank are present (k(m) total output couplers on one PIC), leading to greater bandwidth with simpler packaging complexity, requiring no more than the existing fabrication process on a known unit cell and scaling with known motivations and design oversight. Additionally, the performance of each bank is independently predictable from Zhang’s single-bank device, constituting known elements, known methods, and predictable results.
Regarding claim 4:
Zhang in view of Morrison discloses the PIC of claim 1,
Wherein the MMI couplers (as seen in Figure 1a) comprise:
one or more first MMI couplers to receive from a first subset of the emitter’s odd ones of the channels (this is the first subset, the signals shown in Figure 10c); and one or more second MMI couplers to receive from a second subset of the emitters even ones of the channels (the other set of MMIs, as in Figure 10d).
“As the second stage, the MZI functions as a comb filter with two complementary outputs that divides the optical signals into two groups with odd (λ1, λ3, λ5, λ7) and even channel numbers (λ2, λ4, λ6, λ8), respectively,” section 3.3, pp. 11.
Regarding claim 5:
Zhang in view of Morrison discloses the PIC of claim 4, wherein
the optical interleavers are coupled to interleave multiplexed odd ones of the channels with multiplexed even ones of the channels.
Zhang describes this odd/even channel separation from the demultiplexing perspective. However, Zhang also discloses that the interleaved AMMI architecture, including the MZI interleaver and bidirectional couplers, functions as “both the perfectly vertical grating couplers and 3-dB power splitter/combiner.” This indicates that bidirectional MZI interleaving separates odd and even channels in the demultiplex direction by combining odd and even channels in the multiplex direction – a skilled artisan understands that this is a fundamental property of reciprocal optical devices like the one disclosed. Operating the same MZI interleaver in the transmit direction to combine multiplexed odd channels with multiplexed even channels into composite output signals requires no modification to the device and yields the predictable result of a WDM multiplexed output carrying all n channels.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 4 above under the teachings of Zhang to operate the bidirectional interleaved AMMI architecture in the transmit direction, by combining multiplexed odd channels from the first AMMI with multiplexed even channels from the second AMMI via the interleaver. Doing so is a straightforward reversal of operations of the explicitly disclosed demultiplexing function, requires no new component design, and produces the predictable result of a fully multiplexed WDM output signal at the bidirectional grating couplers.
Regarding claim 10:
Zhang in view of Morrison discloses the PIC of claim 1, wherein:
the interleavers comprise one stage (Figure 1).
Zhang does not teach multiple stages.
Horst teaches a PIC with multiple stages of interleaving (Figure 1), hence one or more stages, and wherein a last of the stages comprises m interleavers, and wherein each of the m interleavers is coupled to an individual one of the m output couplers (insofar as m = 1, Horst teaches this limitation, in “3 st”).
Horst teaches that the “last stage” of the cascaded binary tree – the stage closest to the channel outputs – comprises the maximum number of parallel splitters in the demux direction (4 parallel splitters, “1 st A” to “1 st D”). In the mux direction, the “3 st” element is the last stage, with m = 1. However, for a scaled architecture, m > 1 output couplers are a necessary outcome as a direct consequence of binary tree topology.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Horst to implement Zhang’s WDM transmitter with m > 1 output couplers using Horst’s cascaded tree to arrive at a last interleaver stage comprising m parallel interleavers – one per output couplers – as this is a mathematically inevitable consequence of the binary tree topology scaled to m outputs.
Regarding claim 11:
Zhang in view of Morrison discloses the PIC of claim 1, wherein:
the MMI couplers are arrayed along a first dimension and adjacent to the emitters (the two 1x4 AMMIs are part of a 1x2 array arranged along a first dimension);
Zhang does not teach the emitter array or waveguide crossings.
Morrison teaches that:
the emitters are arrayed along a first dimension of the substrate (Figure 4B, Figure 8, light emitter array 708);
Morrison does not teach the waveguide crossings explicitly, however:
Optical waveguide crossings on silicon photonic platforms are well known in the art as a standard planar layout element for routing waveguides on a planar substrate when signal paths must intersect. It would have been obvious to a skilled artisan implementing Zhang’s WDM transmitter with the co-liner emitter/MMI layout of claim 11 to include waveguide crossings between the MMI couplers and the interleaver stage. When the MMI couplers are arranged co-linearly and adjacent to the emitters along the first substrate dimension, the waveguide paths routing MMI output ports to the interleaver inputs necessarily produce intersecting waveguide paths on the planar substrate. Waveguide crossings are the standard and only available solution for handling such intersections in a planar silicon photonic layout, and their use in this context requires no inventive step. Thus, it would be obvious to configure each of the banks of WDM source circuitry, such that they further comprise one or more optical waveguide crossings between the MMI couplers and the interleavers,
the waveguide crossings spatially organizing the channels into sets that are to be interleaved (this is inherent to the use of waveguide crossings in the claimed architectural context; grouping channels into the correct interleaved sets as a direct consequence of their routing geometry).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Morrison and routine knowledge in the art to array the emitters along a first direction and to organize the channels into interleaved sets with optical crossings between the MMIs and interleavers. This may be accomplished using machining techniques and components known in the art, and would predictably result in a device which can reliably scale optical channels in arrays of light emitting and interleaving architectures, promoting greater signal throughput with minimal loss.
Regarding claim 12:
Zhang in view of Morrison discloses the PIC of claim 1, wherein:
no semiconductor optical amplifiers are included in any of the banks of WDM source circuitry.
This is a negative limitation. Zhang discloses a WDM transmitter architecture comprising light emitters, MMI couplers, an MZI interleaver, and BGC output couplers – there is no explicit disclosure of semiconductor optical amplifiers. In fact, Zhang discloses that the on-chip optical amplification is unavailable on silicon photonic platforms (“As the on-chip optical amplification function is not currently available, the power budget of the silicon photonic circuits is of paramount importance and directly related to the quality of optical communications,”) making the absence of on-chip SOAs a given fact.
Claim(s) 6, 7, 13, 17, 18, and 20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Zhang (Zhang et al., "Numerical Demonstration of 800 Gbps WDM Silicon Photonic Transmitter with Sub-decibel surface-normal optical interfaces", Micromachines, 2022) in view of Morrison (US20230072926A1) and further in view of Horst (“Cascaded Mach-Zehnder wavelength filters in silicon photonics for low loss and flat pass-band WDM (de-)multiplexing”, Optics Express, 2013).
Regarding claim 6:
Zhang in view of Morrison discloses the PIC of claim 4, wherein
Zhang does not explicitly disclose 3 or more light emitters coupled to the two MMI couplers, but they would be an obvious design choice to a skilled artisan to implement, as discussed in the rejection of claim 1. Zhang additionally does not teach the cascade of two or more stages as claimed.
Morrison discloses MMI couplers coupled to three or more light emitters (optical sources 101 are an array of laser sources; as in paragraph 71, and array 708 in Figure 8, there are 8 shown). As such:
the first MMI couplers (806a) are each coupled to three or more of the light emitters;
the second MMI couplers (806b) are each coupled to three or more of the light emitters;
Morrison does not disclose the plurality of interleavers comprises a cascade of two or more stages, wherein a first of the stages comprises three or more interleavers.
Horst discloses WDM (de)multiplexing on a binary tree of cascaded Mach Zehnder like lattice filters (Title, Abstract, Figure 1).
Horst additionally teaches that a plurality of interleavers may comprise a cascade of two or more stages (Figure 1).
Horst does not explicitly teach a first stage comprising three or more interleavers as claimed. However, horst discloses that the number of parallel splitters at each level of the binary tree doubles progressing from input toward output – 1, then 2, then 4. A skilled artisan scaling this architecture to handle a larger number of MMI output subgroups would recognize that when p MMI couplers each produce a distinct multiplexed subgroup, the first interleaver must contain p/2 interleavers to combined adjacent subgroup pairs, yielding three or more first stage interleavers when coupling three or more light emitters to each MMI coupler as claimed. The three-or-more first stage interleaver count is therefore a mathematically inevitable consequence of the channel count scaling already established by the first two limitations of claim 6, implemented using Horst’s disclosed cascaded binary tree architecture teaching.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 4 above under the teachings of Zhang, Morrison, and Horst to couple three or more light emitters to the MMI couplers (for greater bandwidth scaling), and to implement cascading interleaver stages that progressively combines channel subgroups stage by stage. This may be accomplished using components and placement techniques known in the art, and would predictably result in a device which benefits from greater channel combining scalability and flat passband and low insertion loss at scale, requiring merely a reuse of known components in a scaled WDM source PIC with n > 8 channels.
Regarding claim 7:
Zhang in view of Morrison discloses the PIC of claim 4, wherein:
Zhang teaches the division into two channel groups of 4 emitters each, with odd and even sections (section 3.3, pp. 11., as explained in the rejection of claim 4 above). Zhang further teaches 8 light emitters divided into two channel groups of 4 emitters each (x = 2, n/x = 4) – the odd channel subset feeding the first AMMI and the even-channel subset feeding the second AMMI (Zhang Figure 1a depicts the base structure as claimed)
Thus, the n (8) emitters are grouped into a plurality of x (2) channel groups, wherein each of the groups includes n/x (4) channels, each satisfying an expression: i+4(j) for j of 0 to x-1 for each ith group from 1 to x;
The examiner interprets this expression to define the channel indices within each group as every xth channel starting from i. For x = 2 as in Zhang, group 1 contains channels 1, 5 (odd channels), and group 2 contains 2, 6 (even channels).
The variable x is a results effective variable which facilitates the mapping between light sources, channels, and MMI components. A skilled artisan would find it obvious to modify the value of x based on the throughput requirements of any design problem, and could reasonably scale the device using the same methods and more material, without impacting the function of a device. As such, any grouping of emitters with odd and even channels and MMIs under this paradigm are known to a skilled artisan.
the first MMI couplers are each coupled to one of the channel groups with odd ones of the channels (Figure 1a, the first 1x4 AMMI is coupled to the odd channel group);
the second MMI couplers are each coupled to one of the channel groups with even ones of the channels (Figure 1b, the second 1x4 AMMI is coupled to the even channel group);
Zhang does not teach the interleaver and channel relationship as claimed.
Horst teaches that:
odd-channel interleavers are coupled to the first MMI couplers (Figure 1, “2 st A” is a second stage receiving odd channels 1, 3, 5, and 7), each of the odd-channel interleavers to output a composite of odd ones of the channels (this is clear from “3 st”, the third stage, that the composite labeled “odd λ” is output by the previous stage);
even-channel interleavers coupled to the second MMI couplers, each of even-channel interleavers to output a composite of even ones of the channels (2 st B composites channels 2, 4, 6, and 8 into “even λ”);
and odd-even interleavers coupled to one of the odd-channel interleavers and one of the even- channel interleavers and to output a composite of odd and even channels (this is explicitly shown in Figure 1).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 4 under the teachings of Horst to map the odd channels into one interleaving setup which outputs the composite odd channel signal and the even channels into another interleaving setup which outputs the composite even channel signal. This may be accomplished using ordinary design choices and machining techniques known to a skilled artisan, and would predictably result in a device which utilizes interleaving to combine WDM channels and reduce channel spacing, leading to a denser composite signal that improves compact design and lowers loss.
Regarding claim 13:
Morrison teaches a laser comb photonic integrated circuit (PIC) (paragraph 28 discloses the comb source, found in various embodiments throughout, i.e. Figure 11’s comb/narrowband reflectors 1104), comprising:
a silicon substrate (paragraph 30, “For example, the PIC may be fabricated on a silicon photonic platform while the optical sources may be fabricated on a platform comprising III-V semiconductor material”);
a plurality of hybrid silicon lasers arrayed over a first dimension of the substrate (laser sources comprising group III-V semiconductor materials are heterogeneously integrated onto a silicon photonics platform, the standard for hybrid silicon laser architectures), the lasers to output optical signals at consecutive wavelength channels (Table 4, ranges from 1540 nm to 1575 nm in increments of 5 nm);
Morrison does not teach the first, second, or third pluralities as claimed.
Zhang teaches:
Planar optical waveguides on SOI substrate coupling the light emitter inputs to the two 1x4 AMMIs, with the emitters divided into two channel groups – odd and even – each coupled to a corresponding AMMI (Figure 1a shows this layout). Thus, Zhang discloses a first plurality of planar optical waveguides coupling each of the lasers (light emitters) in two or more channel groups (odd and even) to corresponding multi-mode interference (MMI) couplers, the MMI couplers to multiplex optical signals received from one of the channel groups and to output multiplexed signals power split across each of a number of output ports equal to the number of channels in the channel group (Zhang shows that each 1x4 AMMI multiplexes 4 input channels and outputs 4 multiplexed signals power split across 4 output ports – the number of output ports equals the number of channels in the channel group);
Horst discloses a cascaded binary tree structure (Figure 1) with dedicated first stage interleavers coupled to the output ports of individual channel group splitters – one first interleaver per channel group – before combining at subsequent stages.
A skilled artisan would have found it obvious to implement a second plurality of planar optical waveguides coupling each of the output ports of each of the MMI couplers to first interleavers of the channels of one channel group, under the teachings of Horst. Horst provides a structure through which the waveguide on SOI architecture of Zhang can be applied in a manner that increases channel density for greater throughput and smaller channel spacing. ;
Horst teaches that in a cascaded binary tree (Figure 1), the second stage interleavers receive inputs from two firs-stage interleavers – one from the odd-channel path and one from the even-channel path – via dedicated planar waveguide connections, and combine the outputs of two channel groups into a composite signal. As such, a skilled artisan would find it obvious to implement a third plurality of planar optical waveguides coupling each of the first interleavers to a corresponding ones of second interleavers of the channels of two of the channel groups, as this would complete the interleaving of odd and even channels into fewer channels with greater throughput and minimal loss.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the invention of Morrison under the teachings of Zhang and Horst to include planar optical waveguides on a SOI substrate in multiple channel groups leading to an MMI, with 3 pluralities of optical waveguides that are configured in a cascaded binary tree architecture which composites the odd and even channel signals into the output region. This may be accomplished using design architecture and components known in the art, and would predictably result in a device which leads odd and even channels into MMI outputs while compositing the signal for greater channel density and compact design.
Regarding claim 17:
Zhang discloses a photonic system (WDM silicon photonic transmitter system on an SOI substrate), comprising:
a plurality of optical fibers (Figure 1a, the WDM source circuit is optically interfaces with external single-mode fibers via bidirectional grating couplers [BCG], Abstract, Section 1, Section 2.4);
A single WDM source bank (the WDM transmitter with 8 laser inputs, two 1x4 AMMIs, and interleaver, and BGC output coupling on a single SOI substrate is a functional unit that a skilled artisan recognizes to be a “bank of WDM source circuitry”)
lasers physically grouped over the substrate into odd channel sets and even channel sets (Zhang discloses odd channels 1, 3, 5, and 7, and even channels 2, 4, 6, and 8, see section 3.3)
Morrison adds that the laser sources are physically arrayed on the carrier chip, as in Figure 4B.
the lasers to output optical signals at a number of consecutive wavelength channels (Table 4, ranges from 1540 nm to 1575 nm in increments of 5 nm);
a plurality of multi-mode interference (MMI) couplers (Figure 1a, AMMI 1 and 2) adjacent to, and optically coupled to, one of the odd and even channeled sets of the lasers (1, 3, 5, and 7 go to AMMI 1, while 2, 4, 6 and 8 go to AMMI 2), the MMI couplers to multiplex optical signals into a plurality of odd or even channeled multiplexed signals (Section 3.3, the sets are multiplexed into a multiplexed output);
a plurality of optical interleavers optically coupled to the MMI couplers the interleavers to combine the odd channeled multiplexed signals with the even channeled multiplexed signals into composite output signals (Figure 1a, Section 3.3, 2.4, the MZI combined odd and even channel groups – “the MZI functions as a comb filter with two complementary outputs that divides the optical signals into two groups with odd and even channel numbers”, as operated in the mux direction);
and a plurality of output couplers interfacing with the optical fibers to convey the output signals off the silicon substrate (Zhang discloses BGCs serving as output couplers that interface with external single-mode optical fibers to couple composite WDM output signals off the silicon substrate via surface normal coupling, Section 2.4, 3.1, Figure 1a).
Zhang does not disclose the hybrid silicon laser source as claimed, or multiple WDM source banks, or that the laser sources or interleavers are adjacent to the MMIs/PICs which contain them.
Morrison further teaches that:
each of the light emitters comprise a hybrid silicon laser (paragraph 30, “the optical sources may be fabricated on a platform comprising III-V semiconductor material”, laser sources comprising group III-V semiconductor materials are heterogeneously integrated onto a silicon photonics platform, the standard for hybrid silicon laser architectures);
Thus, Morrison teaches a hybrid silicon laser source coupled to the plurality of optical fibers, wherein the laser source comprises a plurality of banks of wave division multiplexing (WDM) source circuitry over a silicon substrate, wherein each of the banks further comprises:
The MMI couplers (Figure 8, found on the PICs 802) are physically adjacent to the laser sources (708)
a plurality of hybrid Si-Group III-V lasers over a substrate comprising silicon (paragraph 30, as shown above),
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the invention of Zhang under the teachings of Morrison and Horst. Zhang’s hybrid laser sources would be replaced with Morrison’s III-V group silicon hybrid DFB laser array (708 in Figure 8 of Morrison), as both reference target silicon photonic WDM transmitters for interconnect applications and Morrison explicitly provides the on chip laser source that Zhang does not contain on its platform. The laser array of Morrison would be grouped into odd and even channel sets on the substrate, as this is the direct and natural layout consequence of Zhang’s odd/even channel assignment, minimizing waveguide routing length and insertion loss. The WDM source bank of Zhang would be replicated into a plurality of banks, requiring no more than a mere duplication of parts, guided by the cascading tree architecture of Horst to ensure stability and performance. The motivation for performing these changes is to create an architecture which can reliably scale for application with high bandwidth/throughput, and would predictably result in a device that requires minimal geometric footprint and exhibits low functional loss.
Regarding claim 18:
Zhang in view of Morrison and Horst discloses the photonic system of claim 17.
Zhang does not explicitly teach an optical isolator, but the use of optical isolators at fiber interfaces (such as those in claim 17) in WDM laser transmitter systems is explicitly described as a standard and well known practice. Critically, a cursory search states that most systems of this kind have some form of optical isolator protecting the laser from back reflections, in the context of silicon photonic WDM transmitters (i.e. Jacques et al, “23-dB average isolation using a silicon photonic Mach-Zehnder modulator”, Optics Express, 2020).
As such, a skilled artisan would have found it obvious to implement optical isolators to reduce back reflection and preserve signal integrity, requiring known components with predictable effects, and without altering the function of the claimed device.
Regarding claim 20:
Zhang in view of Morrison and Horst discloses the photonic system of claim 17.
Where the WDM source circuitry comprises one bank, wherein the bank comprises 8 lasers (Table 4, Zhang discloses 8 lasers in a single ‘bank’ as defined in the rejection of claim 17).
Zhang does not teach multiple banks.
Morrison discloses WDM source architectures scalable to different channel counts with explicitly numerated spacings (paragraph 27, channel spacings of 12.5, 25, 33, 50, 100, and 200 GHz are disclosed and present many possible channel spacings for such a device).
Critically, these source architectures are applied to multiple banks (2), as in Figures 7 and 8 the PICs 802 contain the WDM banks.
Horst discloses a cascaded binary tree interleaver architecture that scales to handle different channel counts by adjusting the number of cascade levels (Figure 1, “1 st A” to “1 st D”, “2 st”, “3 st”, all refer to stages with different channel counts and can easily be scaled).
It is a known design objective to scale the architecture to allow for more channels, and thus greater signal throughput. While Horst does not explicitly cite 12, 16, or 32 lasers, a skilled artisan could reliably scale the tree architecture disclosed such that each of the banks comprises 12, 16 (duplication of the existing architecture), or 32 lasers (a duplication beyond that), with only routine adjustments to the chip size, and without requiring an inventive step, without altering the function of the claimed device.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 17 under the teachings of Morrison and Horst, to include multiple banks that incorporate more channels, ranging from 8, 12, 16, and 32 channels. This change is motivated by the goal to increase device throughput, and guided by the architecture as taught in Horst. Crucially, the modification could be accomplished using known design principles, components, and methods (etching, deposition), and would predictably result in a WDM architecture that is easily scalable for greater bandwidth/throughput with minimal loss.
Claim(s) 19 is/are rejected under 35 U.S.C. 103 as being unpatentable over Zhang (Zhang et al., "Numerical Demonstration of 800 Gbps WDM Silicon Photonic Transmitter with Sub-decibel surface-normal optical interfaces", Micromachines, 2022) in view of Morrison (US20230072926A1) and further in view of Horst (“Cascaded Mach-Zehnder wavelength filters in silicon photonics for low loss and flat pass-band WDM (de-)multiplexing”, Optics Express, 2013) and Chiang (WO 03032021 A2).
Regarding claim 19:
Zhang in view of Morrison and Horst discloses the photonic system of claim 17.
Zhang does not teach an optical amplifier, but discloses a WDM transmitter PIC in which on-chip optical amplification is not present, noting that “on chip optical amplification function is not currently available,” on Zhang’s specific silicon photonic chip platform (section 1). However, Zhang does not criticize, discourage, or teach away from the use of optical amplification in WDM PIC architectures, Zhang’s statement reflects a platform fabrication constraint, not a design preference.
Chiang explicitly discloses a WDM transmitter PIC comprising laser sources (Title, Abstract) further comprising a semiconductor optical amplifier (pp. 9, “In addition, a semiconductor optical amplifier [SOA] array may be included in various points on the chip, for example…”) between any coupled pairing of:
the lasers and the MMI couplers (“…the laser array and the modulator array”), the MMI couplers and the interleavers (“…between the modulator array and the optical combiner…””), or the interleavers and the output couplers (“Also, an SOA may be provided in the output waveguide…”).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 17 above under the teachings of Chiang to include an optical amplifier between any of the MMI couplers, the interleavers, and the output couplers. This may be accomplished using components and placement techniques known in the art, and would predictably result in a device which contains amplifiers that compensate for any loss producing element or process by amplifying the signal.
Claim(s) 16 is/are rejected under 35 U.S.C. 103 as being unpatentable over Zhang (Zhang et al., "Numerical Demonstration of 800 Gbps WDM Silicon Photonic Transmitter with Sub-decibel surface-normal optical interfaces", Micromachines, 2022) in view of Morrison (US20230072926A1) and further in view of Horst (“Cascaded Mach-Zehnder wavelength filters in silicon photonics for low loss and flat pass-band WDM (de-)multiplexing”, Optics Express, 2013) and Heck (US 11906777 B2).
Regarding claim 16:
Morrison in view of Zhang and Horst disclose the PIC of claim 13.
Morrison does not explicitly teach that the waveguide(s) may comprise a SiN ridge over the substrate, they teach waveguiding elements only. However, using a ridge architecture is a routine design choice.
Zhang explicitly teaches the use of silicon ridge waveguides (Section 3.3, “all the waveguides of the AMMIs are designed with a ridge waveguide structure of 220 nm in height and 150 in etch depth”), but they are silicon instead of Silicon Nitride.
Heck discloses an integrated photonic transceiver (Title), wherein a waveguide comprises a SiN (“it may be desirable to integrate one or more silicon nitride [SiN] passive optical components…”, “…the silicon waveguide may be tapered to allow the light to pass into the SiN waveguide”) ridge over the substrate (Figure 3, SiN waveguide 206 has a ridge geometry over the substrate 215).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 13 above under the teachings of Heck to include a ridge that is composed of SiN using materials and manufacturing methods (i.e. vapor deposition, etching) known in the art. Silicon Nitride is known in the art for its ability to mitigate propagation loss (when compared with silicon) and to provide greater thermal stability, which is important in high bandwidth applications.
Allowable Subject Matter
Claims 8, 9, 14 and 15 are objected to as being dependent upon a rejected base claim, but would be allowable if re-written in independent form including all of the limitations of the base claim and any intervening claims.
The following is a statement of reasons for the indication of allowable subject matter: the prior art of record, which is the most relevant prior art known, does not disclose or render obvious:
The PIC of claim 8, wherein:
three odd-channel interleavers coupled to the first pair of MMI couplers;
three even-channel interleavers coupled to the second pair of MMI couplers;
and three odd-even interleavers, each coupled to one of the odd-channel interleavers and to one of the even-channel interleavers, in combination with all of the other limitations of claims 1, 4, and 7.
The PIC of claim 9, wherein:
the first MMI couplers comprise a first pair of MMI couplers, each of the first pair coupled to four of the emitters to receive alternating odd ones of the channels and to output four multiplexed signals comprising the alternating odd ones of the channels power split across each of a first set of four ports;
the second MMI couplers comprise a second pair of MMI couplers, each of the second pair coupled to four of the emitters to receive alternating even ones of the channels and to output four multiplexed signals comprising the alternating even ones of the channels power split across each of a second set of four ports;
and the interleavers comprise:
four odd-channel interleavers coupled to the first pair of MMI couplers;
four even-channel interleavers coupled to the second pair of MMI couplers;
and four odd-even interleavers, each coupled to one of the odd-channel interleavers and to one of the even-channel interleavers, in combination with all of the other limitations of claims 1, 4, and 7.
The PIC of claim 14, wherein:
the second interleavers comprise odd-even interleavers coupled to one of the odd-channel interleavers and one of the even-channel interleavers, the odd-even interleavers to output a composite signal including the odd and even channel, in combination with all of the other limitations of claims 13.
The PIC of claim 15, as it depends on the PIC of claim 14.
The use of odd-even channel interleavers is uncommon in the art, and not found to be obvious or taught in the prior art as claimed. Additionally, the specific channel numbers and groupings as claimed are not obvious in combination with the other limitations of base claims, including odd/even channels, channel grouping connected with, and number of multiplexed signals.
Additional Prior Art
The following prior art is made available to the applicant but not used as a basis for any rejection. It is merely an indicator of the status of knowledge in the art.
Hou (US 6678476 B1) - Extra reference of relevance showing cascading stages.
23-dB average isolation using a silicon photonic Mach-Zehnder modulator, Jacques et al., Optics Express, 2022. – Optical isolators are well known to a skilled artisan.
Conclusion
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/PREET B PATEL/Examiner, Art Unit 2874
/THOMAS A HOLLWEG/Supervisory Patent Examiner, Art Unit 2874
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