1014-00003 · Optiwave Semiconductor Corp · Pre-Suit Investigation & Strategy

pre-suit-infringement-analysis-567-patent.docx DOCUMENT Litigation

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PRIVILEGED AND CONFIDENTIAL — ATTORNEY WORK PRODUCT

This memorandum is protected by the attorney-client privilege and the work product doctrine. It has been prepared at the direction of counsel in anticipation of litigation. It is not to be disclosed to any person outside of Calderwood & Harkness LLP without the express written authorization of the Responsible Partner. Distribution to the client requires prior Partner approval.

MEMORANDUM

April 18, 2022

TO: Alan Ngo, Responsible Partner, intellectual Property Group, Calderwood & Harkness LLP

FROM: Omar Siddiqui, Lead Associate, and Christy Bauer, Associate, intellectual Property Group, Calderwood & Harkness LLP

RE: Pre-Suit Infringement Analysis — U.S. Patent No. 10,234,567 ("the '567 Patent") — Optiwave Semiconductor Corp. v. Lumos Photonics, Inc.

MATTER NO.: 1014-00003

CLIENT: Optiwave Semiconductor Corp. ("OWS")

STATUS: DRAFT — For Internal Review Only; Not for Distribution to Client Without Partner Approval

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I. Executive Summary

The purpose of this memorandum is to assess whether Lumos Photonics, Inc. ("Lumos" or "LPI") infringes the asserted Claims 1, 4, 7, 12, and 15 of U.S. Patent No. 10,234,567 ("the '567 Patent") through its LumosBridge™ 800G Optical Engine and LumosEdge™ 400ZR+ Pluggable Transceiver products. This analysis has been prepared at the direction of Alan Ngo in anticipation of the potential filing of a patent infringement action by OWS against Lumos in the United States District Court for the Western District of Texas (Waco Division) or, alternatively, the Northern District of California. This memorandum addresses the '567 Patent only; separate memoranda have been prepared for the '234, '678, and '890 Patents, and a consolidated Validity Risk Assessment Memorandum is forthcoming.

Overall Assessment. Based on our review of the '567 Patent, its prosecution history, and the publicly available technical information regarding the accused Lumos products, we conclude that there is a reasonable basis for asserting literal infringement of most claim limitations in the asserted claims. All of the structural and dimensional limitations of the asserted claims appear to be satisfied by the accused LumosBridge™ 800G Optical Engine and LumosEdge™ 400ZR+ Pluggable Transceiver products. However, the "adiabatically coupled" limitation recited in independent Claim 1 (and incorporated by reference in dependent Claims 4 and 7, and effectively restated in independent Claim 12 and dependent Claim 15) presents a significant vulnerability. Specifically, Lumos's accused products appear to employ a segmented (non-continuous) taper design with discrete coupling sections rather than a single continuous adiabatic taper. Whether this design falls within the scope of the "adiabatically coupled" limitation will depend critically on the claim construction adopted by the Court.

Doctrine of Equivalents. The doctrine of equivalents ("DOE") provides a secondary, but materially weaker, fallback theory for the "adiabatically coupled" limitation. However, prosecution history estoppel may substantially limit or foreclose DOE analysis with respect to this limitation. During prosecution of the '567 Patent, the applicants added the "adiabatically coupled" language by amendment in direct response to the examiner's rejection over the Tanaka prior art reference (U.S. Patent No. 9,456,012). Under Festo Corp. v. Fenmore & Co., 535 U.S. 722 (2002), a presumption arises that the patentee surrendered all equivalents between the original broad claim scope and the narrower amended scope. Because segmented taper couplers were well-known at the time of prosecution — indeed, the Chen & Liu (2016) reference describing such couplers was cited by the examiner during the second office action — a foreseeability-based rebuttal of the Festo presumption would be difficult to sustain.

Recommendation. The '567 Patent provides a viable but not risk-free basis for suit against Lumos. The claim construction risk on the "adiabatically coupled" term is the primary concern and represents the most significant point of vulnerability in the infringement theory. We recommend that this risk be weighed alongside the strength of the infringement theories under the other three patents-in-suit (the '234, '678, and '890 Patents) as part of the overall litigation strategy assessment. We further recommend early engagement of a technical expert, specifically Dr. Harold Whitfield of UC Santa Barbara, to support OWS's proposed claim construction and to prepare a declaration addressing the understanding of a person of ordinary skill in the art ("POSITA") regarding the term "adiabatically coupled."

II. Background

A. The '567 Patent

The patent at issue in this analysis is U.S. Patent No. 10,234,567, titled "Integrated Waveguide Coupler with Tapered Mode Converter for Silicon Photonics Platforms" (hereinafter, "the '567 Patent"). The relevant bibliographic data for the '567 Patent is as follows:

The '567 Patent is directed to the field of silicon photonics, and more specifically to integrated optical coupler architectures designed for efficient fiber-to-chip light coupling on silicon photonics platforms. The core innovation disclosed and claimed in the patent is a tapered silicon waveguide that couples light from an optical fiber into a silicon nitride (SiN) waveguide layer through an adiabatic mode transition. This architecture enables low-loss fiber-to-chip coupling, which is a critical performance parameter for high-speed transceiver applications used in data center interconnects and telecommunications networks.

The named inventors on the '567 Patent include Dr. Kevin Fong, who serves as Chief Technology Officer and Co-Founder of OWS; Dr. Priya Ramanathan, who serves as Chief Executive Officer and Co-Founder of OWS; and Hideo Tanaka, a former OWS engineer who was employed by the company from 2016 to 2019. As discussed in greater detail in Section IV below, Mr. Tanaka's involvement as a named inventor on the '567 Patent, combined with his separate role as a co-inventor on the Tanaka prior art patent (U.S. Patent No. 9,456,012, developed before he joined OWS), introduces a factual complexity that has both prosecution history implications and potential narrative consequences at trial. The patent was assigned to Optiwave Semiconductor Corp. upon filing, and OWS remains the sole owner and assignee of record.

The technology covered by the '567 Patent addresses a well-known challenge in the silicon photonics industry: the mode-size mismatch between a standard single-mode optical fiber (with a mode field diameter of approximately 8–10 micrometers) and a silicon waveguide on a photonic integrated circuit (with a mode field diameter on the order of hundreds of nanometers). This orders-of-magnitude difference in mode size results in significant coupling losses if not properly addressed. The '567 Patent discloses a solution involving an inverse taper structure in the silicon waveguide — where the waveguide tip is narrowed to sub-200 nanometer widths — that adiabatically transfers the optical mode to a larger silicon nitride waveguide layer, which serves as an intermediate coupling element between the fiber and the silicon waveguide. This adiabatic transition is designed to minimize power loss and prevent excitation of higher-order modes during the mode conversion process.

B. The Client — Optiwave Semiconductor Corp.

Optiwave Semiconductor Corp. ("OWS" or "the Company") is a Delaware corporation headquartered at 2775 Augustine Drive, Suite 400, San Jose, California 95054. OWS was founded in 2014 and operates as a fabless semiconductor design company specializing in silicon photonics integrated circuits for data center interconnect and telecommunications applications.

OWS reported fiscal year 2022 revenue of approximately $187.4 million, reflecting year-over-year growth driven primarily by demand for its coherent optical transceiver chipsets in hyperscale data center deployments. The Company employs approximately 620 individuals, with engineering and design operations concentrated in San Jose, California and a smaller engineering office in Portland, Oregon. OWS's key products include the OWS-400ZR and OWS-800LR coherent optical transceiver chipsets, which compete directly with Lumos's accused products in the data center interconnect market.

OWS maintains a patent portfolio of 87 issued U.S. utility patents and 14 pending patent applications, spanning silicon photonics design, waveguide architectures, modulator structures, and transceiver packaging technologies. The '567 Patent is one of four patents that OWS has identified for assertion against Lumos (the others being the '234, '678, and '890 Patents). A pre-litigation patent portfolio valuation conducted by Clearpath IP Valuation Services, Inc. (Boston, Massachusetts; lead analyst Jennifer Armitage, CFA, CLP) valued the four asserted patents collectively at approximately $42.8 million and the full OWS patent portfolio at approximately $215 million.

OWS is majority-owned (approximately 62%) by Vantage Point Capital Partners Fund IV, LP, a venture capital fund based in Menlo Park, California, with approximately $2.1 billion in assets under management. The fund's Managing Partner is Douglas Fairbanks III, and the Operating Partner with responsibility for the OWS investment is Rebecca Torres. Vantage Point's majority ownership interest is a relevant consideration for litigation funding and strategic decision-making regarding the prosecution of this action.

As a fabless semiconductor company, OWS does not operate its own fabrication facilities. The Company's silicon photonic integrated circuits are fabricated by Pinnacle Semiconductor Foundry Co., Ltd., located in Hsinchu, Taiwan, using a 45nm silicon-on-insulator (SOI) process. This manufacturing arrangement is relevant to potential discovery and damages considerations, as OWS's cost structure and margin profile differ materially from those of an integrated device manufacturer such as Lumos.

C. The Accused Infringer — Lumos Photonics, Inc.

Lumos Photonics, Inc. ("Lumos" or "LPI") is a Delaware corporation headquartered at 9400 McNeil Drive, Building 7, Austin, Texas 78758. Unlike OWS, Lumos operates as an integrated device manufacturer ("IDM") of silicon photonics components, maintaining both design and fabrication capabilities. Lumos's primary fabrication facility is located at 3200 NE Shute Road, Hillsboro, Oregon 97124, where the Company operates a silicon photonics fabrication line. Lumos also maintains a sales office and engineering center at 4750 Great America Parkway, Suite 320, Santa Clara, California 95054.

Lumos was founded in 2016 and has grown rapidly to become a significant competitor in the silicon photonics market for hyperscale data center applications. The Company reported fiscal year 2022 revenue of approximately $312.8 million and employs approximately 1,450 individuals across its Austin, Hillsboro, and Santa Clara locations.

Lumos is publicly traded on the Nasdaq Stock Market under the ticker symbol "LMPH." As of early June 2022 estimates, the Company's market capitalization is approximately $1.87 billion. The largest institutional shareholder is Ridgeline Asset Management, LLC, which holds an approximately 9.2% stake in the Company. Lumos's public company status is relevant to the availability of financial data for damages analysis, as its quarterly and annual reports filed with the SEC provide revenue breakdowns and product-level disclosures that can be used to estimate accused product revenues.

Key personnel at Lumos relevant to this matter include:

• James "Jim" Harrelson — Chief Executive Officer

• Dr. Mei-Lin Chen — Chief Technology Officer (Dr. Chen has published extensively on silicon photonics coupler designs and has presented at industry conferences including OFC and ECOC, making her publications and presentations a significant source of publicly available technical information regarding the accused products)

• Richard Talbot — General Counsel

• Dr. Nikolai Petrov — Vice President of Engineering, Photonics Division (Dr. Petrov oversees the design and development of the silicon photonic integrated circuits used in the accused products)

Lumos has retained Brannick Howell & Stein LLP as litigation counsel. The firm's Austin, Texas office serves as lead counsel, with additional support from its San Francisco office located at 555 California Street, Suite 2800, San Francisco, California 94104. The lead partner on the matter is Victoria "Tori" Ashworth, a well-regarded patent litigator with significant experience in semiconductor and photonics patent disputes.

D. Accused Products

This analysis identifies two Lumos products as accused of infringing the '567 Patent:

1. LumosBridge™ 800G Optical Engine. The LumosBridge™ 800G is a co-packaged optics ("CPO") engine designed for integration with hyperscale data center network switches. Co-packaged optics represents an emerging architecture in which optical transceivers are integrated directly onto the switch package rather than being deployed as separate pluggable modules. The LumosBridge™ 800G incorporates a silicon photonic integrated circuit (PIC) that includes, among other components, a fiber-to-chip waveguide coupler, optical modulators, photodetectors, and wavelength multiplexing/demultiplexing structures. The LumosBridge™ 800G was first shipped commercially in Q1 2022. Based on publicly available pricing data and industry reports, the unit price of the LumosBridge™ 800G ranges from approximately $1,200 to $1,800, depending on configuration and volume.

2. LumosEdge™ 400ZR+ Pluggable Transceiver. The LumosEdge™ 400ZR+ is a pluggable optical transceiver module in the QSFP-DD (Quad Small Form Factor Pluggable – Double Density) form factor, designed for metro and data center interconnect ("DCI") applications. The LumosEdge™ 400ZR+ implements the OIF (Optical Internetworking Forum) 400ZR+ specification and incorporates a silicon photonic integrated circuit with coherent optical engine functionality. Like the LumosBridge™ 800G, the LumosEdge™ 400ZR+ incorporates a fiber-to-chip waveguide coupler as a core functional component. The LumosEdge™ 400ZR+ has been in production since Q3 2021 and carries a unit price in the range of approximately $600 to $900.

Both accused products incorporate silicon photonic integrated circuits with fiber-to-chip waveguide couplers that include tapered silicon waveguides and silicon nitride waveguide layers. The waveguide coupler is a necessary component of both products, as it provides the optical interface between the external fiber connections and the on-chip photonic circuitry.

Based on Lumos's public filings with the SEC and available market data, the combined accused product revenue for calendar year 2022 is estimated at approximately $148.6 million. For the pre-suit damages period (Q1–Q2 2022, estimated from the date of Lumos's first notice of the '567 Patent through the anticipated filing date), the combined accused product revenue is estimated at approximately $62.3 million.

E. Pre-Suit Correspondence

On March 15, 2022, OWS, through outside counsel at Calderwood & Harkness LLP, sent a cease-and-desist letter to Lumos Photonics, Inc. (addressed to Richard Talbot, General Counsel) regarding the '567 Patent and the '234 Patent. The letter identified the LumosBridge™ 800G Optical Engine and LumosEdge™ 400ZR+ Pluggable Transceiver as accused infringing products, provided OWS's preliminary infringement contentions, and demanded that Lumos immediately cease all infringing activities and enter into licensing negotiations with OWS. The letter also notified Lumos that OWS was prepared to file suit if Lumos did not respond within thirty (30) days and take meaningful steps toward resolution.

On April 4, 2022, Lumos responded through its litigation counsel, Victoria Ashworth of Brannick Howell & Stein LLP. The response letter denied infringement of both the '567 Patent and the '234 Patent on the grounds that Lumos's products do not practice the asserted claims and further asserted that both patents are invalid in view of the prior art. The letter did not identify specific invalidity grounds but reserved Lumos's right to raise all available defenses. The letter also stated that Lumos considered OWS's allegations to be "without merit" and that Lumos would "vigorously defend any action brought by OWS."

These pre-suit communications are significant for several reasons. First, the March 15, 2022 cease-and-desist letter establishes the date on which Lumos received actual notice of the '567 Patent and OWS's infringement allegations, which is relevant to the calculation of pre-suit damages and the potential availability of willfulness enhancements under 35 U.S.C. § 284. Second, Lumos's continued manufacture and sale of the accused products after receiving notice — without any apparent design-around or licensing effort — may support an allegation of willful infringement under Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. 93 (2016). Third, the exchange of correspondence demonstrates that the parties have been unable to reach a pre-litigation resolution, which will be relevant to the Court's assessment of the parties' conduct and any future mediation or settlement discussions.

III. Claim Language — Asserted Claims

This section sets forth the full text of each of the five asserted claims of the '567 Patent. Each claim is presented verbatim as it appears in the issued patent, with individual limitations identified and numbered for purposes of the element-by-element infringement analysis in Section V below.

A. Independent Claim 1

Claim 1 of the '567 Patent recites:

1. An integrated optical coupler comprising:

a tapered silicon waveguide having a tip width of less than 200 nanometers, the tapered silicon waveguide being disposed on a substrate and having a longitudinal axis extending from a first end to a second end, the tip width being measured at the first end;

a silicon nitride waveguide layer disposed adjacent to the tapered silicon waveguide and vertically separated therefrom by a cladding layer having a thickness of between 50 nanometers and 500 nanometers;

wherein the tapered silicon waveguide is adiabatically coupled to the silicon nitride waveguide layer such that an optical mode propagating in the silicon nitride waveguide layer is gradually transferred to the tapered silicon waveguide through evanescent field interaction along the longitudinal axis, and

wherein the integrated optical coupler is configured to receive light from an optical fiber and couple the received light into the tapered silicon waveguide with an insertion loss of less than 1.5 dB per facet.

For purposes of the infringement analysis, the limitations of Claim 1 are identified and numbered as follows:

• [1a] — "An integrated optical coupler" (preamble)

• [1b] — "comprising a tapered silicon waveguide having a tip width of less than 200 nanometers"

• [1c] — "the tapered silicon waveguide being disposed on a substrate and having a longitudinal axis extending from a first end to a second end, the tip width being measured at the first end"

• [1d] — "a silicon nitride waveguide layer disposed adjacent to the tapered silicon waveguide and vertically separated therefrom by a cladding layer having a thickness of between 50 nanometers and 500 nanometers"

• [1e] — "wherein the tapered silicon waveguide is adiabatically coupled to the silicon nitride waveguide layer such that an optical mode propagating in the silicon nitride waveguide layer is gradually transferred to the tapered silicon waveguide through evanescent field interaction along the longitudinal axis"

• [1f] — "wherein the integrated optical coupler is configured to receive light from an optical fiber and couple the received light into the tapered silicon waveguide with an insertion loss of less than 1.5 dB per facet"

B. Dependent Claim 4

Claim 4 of the '567 Patent recites:

4. The integrated optical coupler of claim 1, wherein the tapered silicon waveguide has a taper length of between 100 micrometers and 500 micrometers, and wherein the tapered silicon waveguide has a cross-sectional height of between 150 nanometers and 340 nanometers along the longitudinal axis.

Claim 4 depends from Claim 1 and adds the following additional limitations:

• [4a] — "the tapered silicon waveguide has a taper length of between 100 micrometers and 500 micrometers"

• [4b] — "the tapered silicon waveguide has a cross-sectional height of between 150 nanometers and 340 nanometers along the longitudinal axis"

C. Dependent Claim 7

Claim 7 of the '567 Patent recites:

7. The integrated optical coupler of claim 1, wherein the silicon nitride waveguide layer has a width of between 2 micrometers and 12 micrometers at an input facet and is configured such that the coupling efficiency between the silicon nitride waveguide layer and the tapered silicon waveguide exceeds 90% over a wavelength range of 1260 nm to 1360 nm.

Claim 7 depends from Claim 1 and adds the following additional limitations:

• [7a] — "the silicon nitride waveguide layer has a width of between 2 micrometers and 12 micrometers at an input facet"

• [7b] — "configured such that the coupling efficiency between the silicon nitride waveguide layer and the tapered silicon waveguide exceeds 90% over a wavelength range of 1260 nm to 1360 nm"

D. Independent Claim 12

Claim 12 of the '567 Patent recites:

12. An optical transceiver system comprising:

a silicon photonic integrated circuit disposed on a silicon-on-insulator substrate, the silicon photonic integrated circuit comprising:

an integrated waveguide coupler including a tapered silicon waveguide having a tip width of less than 200 nanometers adiabatically coupled to a silicon nitride waveguide layer through evanescent field interaction, the integrated waveguide coupler being configured to receive light from an external optical fiber;

at least one optical modulator optically connected to the tapered silicon waveguide; and

at least one photodetector optically connected to the tapered silicon waveguide;

a driver circuit electrically connected to the at least one optical modulator; and

a transimpedance amplifier electrically connected to the at least one photodetector,

wherein the optical transceiver system is configured to transmit and receive optical signals at a data rate of at least 100 Gbps per lane.

For purposes of the infringement analysis, the limitations of Claim 12 are identified and numbered as follows:

• [12a] — "An optical transceiver system" (preamble)

• [12b] — "a silicon photonic integrated circuit disposed on a silicon-on-insulator substrate"

• [12c] — "an integrated waveguide coupler including a tapered silicon waveguide having a tip width of less than 200 nanometers adiabatically coupled to a silicon nitride waveguide layer through evanescent field interaction"

• [12d] — "the integrated waveguide coupler being configured to receive light from an external optical fiber"

• [12e] — "at least one optical modulator optically connected to the tapered silicon waveguide"

• [12f] — "at least one photodetector optically connected to the tapered silicon waveguide"

• [12g] — "a driver circuit electrically connected to the at least one optical modulator"

• [12h] — "a transimpedance amplifier electrically connected to the at least one photodetector"

• [12i] — "wherein the optical transceiver system is configured to transmit and receive optical signals at a data rate of at least 100 Gbps per lane"

E. Dependent Claim 15

Claim 15 of the '567 Patent recites:

15. The optical transceiver system of claim 12, wherein the silicon nitride waveguide layer has a refractive index of between 1.9 and 2.1 at a wavelength of 1310 nm, and wherein the cladding layer separating the tapered silicon waveguide from the silicon nitride waveguide layer comprises silicon dioxide having a thickness of between 100 nanometers and 300 nanometers.

Claim 15 depends from Claim 12 and adds the following additional limitations:

• [15a] — "the silicon nitride waveguide layer has a refractive index of between 1.9 and 2.1 at a wavelength of 1310 nm"

• [15b] — "the cladding layer separating the tapered silicon waveguide from the silicon nitride waveguide layer comprises silicon dioxide having a thickness of between 100 nanometers and 300 nanometers"

The full text of all asserted claims is also reproduced in Appendix A for ease of reference.

IV. Prosecution History Summary

A thorough review of the prosecution history of the '567 Patent is essential to the infringement analysis because (1) the prosecution history directly informs the construction of the critical "adiabatically coupled" limitation, and (2) the amendments and arguments made during prosecution give rise to potential prosecution history estoppel that may foreclose or limit application of the doctrine of equivalents. The '567 Patent was prosecuted before Art Unit 2828 of the United States Patent and Trademark Office ("USPTO").

First Office Action (Non-Final Rejection). On July 12, 2017, the examiner issued a non-final office action rejecting all pending claims under 35 U.S.C. § 102(a)(1) as anticipated by Tanaka et al., U.S. Patent No. 9,456,012 (issued September 6, 2016) ("the Tanaka Reference"). The Tanaka Reference discloses an integrated optical coupler for silicon photonics platforms that includes a tapered silicon waveguide coupled to a secondary waveguide layer. Notably, Hideo Tanaka — who is a named inventor on both the Tanaka Reference and the '567 Patent — developed the Tanaka Reference prior to joining OWS. Mr. Tanaka was employed at Solvus Photonics (now defunct) when the Tanaka Reference was filed, and he subsequently joined OWS in 2016, where he contributed to the development of the technology claimed in the '567 Patent. The examiner found that the Tanaka Reference disclosed all of the then-pending claim limitations, including a tapered silicon waveguide and a secondary waveguide layer, and that the claims were therefore anticipated.

Amendment After First Office Action. On October 18, 2017, the applicants filed a response to the first office action that included amendments to the independent claims and accompanying remarks. Critically, the applicants narrowed the independent claims by adding the "adiabatically coupled" limitation to distinguish the claimed coupler structure from the Tanaka Reference. Specifically, the applicants amended independent Claim 1 to require that "the tapered silicon waveguide is adiabatically coupled to the silicon nitride waveguide layer such that an optical mode propagating in the silicon nitride waveguide layer is gradually transferred to the tapered silicon waveguide through evanescent field interaction along the longitudinal axis." Independent Claim 12 was similarly amended to include "adiabatically coupled" language.

In the accompanying remarks, the applicants argued that the Tanaka Reference does not disclose or suggest an adiabatic coupling mechanism. The applicants stated that the Tanaka Reference instead discloses a "butt-coupling" or "direct-coupling" configuration in which the optical mode transitions abruptly from one waveguide to another at a coupling interface, rather than being gradually transferred through a continuous adiabatic taper. The applicants further stated that the claimed adiabatic coupling mechanism provides superior performance in terms of coupling loss and modal purity compared to the direct-coupling approach of the Tanaka Reference.

Second Office Action (Non-Final Rejection). On January 30, 2018, the examiner issued a second non-final office action. In this action, the examiner withdrew the § 102(a)(1) rejection based on the Tanaka Reference alone but entered a new rejection under 35 U.S.C. § 103 based on a combination of the Tanaka Reference with Chen & Liu, "Segmented Taper Coupler Design for Low-Loss Fiber-to-Chip Coupling," Journal of Photonic Integration, Vol. 14, No. 3, pp. 217–229 (2016) ("the Chen & Liu Reference"). The examiner reasoned that it would have been obvious to a person of ordinary skill in the art to modify the coupler disclosed in the Tanaka Reference by incorporating a taper coupling structure as taught by Chen & Liu in order to improve coupling efficiency.

Response to Second Office Action. On April 25, 2018, the applicants filed a response to the second office action. In this response, the applicants argued that the combination of Tanaka and Chen & Liu does not render the amended claims obvious because the Chen & Liu Reference describes a segmented taper coupler — a fundamentally different coupling approach from the adiabatic coupling recited in the claims. The applicants' remarks included the following key statements:

"The claimed integrated optical coupler requires that the silicon waveguide is adiabatically coupled to the silicon nitride waveguide layer. Adiabatic coupling, as understood by those of ordinary skill in the art, requires a gradual, continuous taper that transitions the optical mode from one waveguide to another without exciting higher-order modes. The Chen & Liu reference, by contrast, describes a segmented taper coupler that uses multiple discrete taper sections separated by transition regions. This segmented design introduces discontinuities in the taper geometry that fundamentally distinguish it from the continuous adiabatic taper required by the claims. The claimed adiabatic coupling mechanism cannot be achieved by combining the Tanaka coupler with the Chen & Liu segmented taper, because the resulting structure would not provide the gradual, continuous mode transition required by the claims." (Emphasis in original.)

These prosecution history statements are significant because they arguably constitute a clear and unmistakable disavowal of segmented taper designs. Lumos is expected to rely heavily on these statements in opposing OWS's proposed claim construction and in asserting prosecution history estoppel against any doctrine of equivalents argument.

Notice of Allowance. On August 14, 2018, the examiner issued a notice of allowance for the amended claims. The examiner's reasons for allowance referenced the "adiabatically coupled" limitation as a distinguishing feature over the prior art, stating that the prior art of record did not disclose or suggest a tapered silicon waveguide "adiabatically coupled" to a silicon nitride waveguide layer in the manner recited in the claims.

Key Estoppel Risk. The addition of the "adiabatically coupled" limitation was a narrowing amendment made during prosecution for the specific purpose of overcoming prior art. Under Festo Corp. v. Fenmore & Co., 535 U.S. 722 (2002), this amendment gives rise to a rebuttable presumption that the patentee surrendered all equivalents that fall between the original broad claim scope (which encompassed any type of coupling, including segmented taper coupling) and the narrower amended claim scope (which requires "adiabatic" coupling). Any argument under the doctrine of equivalents to extend the "adiabatically coupled" limitation to encompass segmented or non-continuous taper designs will face a significant estoppel barrier, as discussed further in Section VI below.

A detailed timeline of the prosecution history is provided in Appendix D.

V. Literal Infringement Analysis — Element-by-Element

This section presents an element-by-element analysis of each asserted claim against the two accused Lumos products. Under well-established patent law, literal infringement requires that each and every limitation of a claim be met by the accused product. Pemberton Partners LLC v. F. Hoffmann-La Roche Ltd., 580 F.3d 1340, 1374 (Fed. Cir. 2009). If even one limitation is not literally met, literal infringement of the claim cannot be established (though infringement under the doctrine of equivalents may still be available for the unmet limitation, subject to applicable limitations). The analysis below addresses Claims 1, 4, 7, 12, and 15 in order.

A. Claim 1 Analysis

Limitation [1a]: "An integrated optical coupler" (Preamble)

The preamble of Claim 1 recites "[a]n integrated optical coupler." As an initial matter, we note that whether a preamble is limiting depends on whether it "recites essential structure or steps, or . . . is 'necessary to give life, meaning, and vitality' to the claim." Severin Holdings v. Quillon Corporation, 289 F.3d 801, 808 (Fed. Cir. 2002). In this case, the preamble provides context for the claimed invention as an "integrated optical coupler," and the body of the claim references and builds upon this structure. We therefore treat the preamble as limiting for purposes of this analysis.

Both the LumosBridge™ 800G Optical Engine and the LumosEdge™ 400ZR+ Pluggable Transceiver incorporate integrated optical couplers as part of their respective silicon photonic integrated circuits. These couplers provide the fiber-to-chip optical interface necessary for the products to receive and transmit optical signals through external fiber connections. Publicly available product datasheets for both products describe integrated coupler architectures, and Lumos technical white papers and conference presentations by Dr. Mei-Lin Chen and Dr. Nikolai Petrov confirm the use of on-chip integrated optical couplers in both product lines.

Assessment: Met by both accused products. Confidence: High.

Limitation [1b]: "comprising a tapered silicon waveguide having a tip width of less than 200 nanometers"

Claim 1 requires a "tapered silicon waveguide having a tip width of less than 200 nanometers." This limitation specifies that the optical coupler includes a waveguide made of silicon with a taper structure — that is, a waveguide whose width varies along its length — and that the narrowest point (the "tip") has a width of less than 200 nanometers.

Both accused products utilize silicon waveguides with tapering structures for mode conversion, which is a standard design approach in silicon photonics fiber-to-chip coupling. Lumos's published design descriptions for its silicon photonic integrated circuits reference the use of "inverse taper" or "spot-size converter" structures, both of which involve tapered silicon waveguides. An inverse taper narrows the silicon waveguide from its standard width down to a very narrow tip, which expands the optical mode to better match the mode profile of the input fiber or an intermediate waveguide layer. This is precisely the type of structure described in the '567 Patent.

Assessment: Met by both accused products. Confidence: High.

Limitation [1c]: "the tapered silicon waveguide being disposed on a substrate and having a longitudinal axis extending from a first end to a second end, the tip width being measured at the first end"

This limitation requires that the tapered silicon waveguide is disposed on a substrate (consistent with standard silicon photonics fabrication on silicon-on-insulator substrates), has a longitudinal axis extending from a first end to a second end, and that the tip width (less than 200 nanometers per Limitation [1b]) is measured at the first end.

Both accused products are fabricated on silicon-on-insulator (SOI) substrates, as disclosed in Lumos's published fabrication process descriptions and confirmed by publicly available teardown analyses of comparable silicon photonic integrated circuits. The tapered silicon waveguide in each product necessarily extends along a longitudinal axis from a narrow tip end (adjacent to the input coupling region) to a wider end (where it transitions to the standard on-chip waveguide dimensions). This structural arrangement is inherent to the inverse taper coupler design employed in both products.

Assessment: Met by both accused products. Confidence: High.

Limitation [1d]: "a silicon nitride waveguide layer disposed adjacent to the tapered silicon waveguide and vertically separated therefrom by a cladding layer having a thickness of between 50 nanometers and 500 nanometers"

This limitation requires the presence of a silicon nitride (SiN) waveguide layer that is positioned adjacent to (but vertically separated from) the tapered silicon waveguide, with a cladding layer between them having a thickness in the specified range of 50 to 500 nanometers.

Lumos's silicon photonic integrated circuit platform incorporates silicon nitride waveguide layers, as confirmed by multiple publicly available sources. Dr. Mei-Lin Chen's keynote presentation at the 2021 Optical Fiber Communication Conference (OFC 2021), titled "Advanced Silicon Photonics Platforms for Next-Generation Data Center Interconnects," explicitly describes Lumos's use of a multi-layer silicon photonics platform that includes both silicon and silicon nitride waveguide layers. Dr. Nikolai Petrov's co-authored paper in IEEE Photonics Technology Letters (Vol. 33, No. 18, September 2021) similarly describes a silicon photonics platform with a SiN waveguide layer integrated above the silicon waveguide layer, separated by a silicon dioxide cladding interlayer.

The specific cladding thickness between the silicon and silicon nitride layers in Lumos's products has not been publicly disclosed with sufficient precision to confirm whether it falls within the 50 to 500 nanometer range. However, industry-standard silicon photonics fabrication processes typically employ cladding interlayer thicknesses in the range of approximately 100 to 300 nanometers for coupled waveguide structures, which falls comfortably within the claimed range. Confirmation of the precise cladding thickness will require discovery of Lumos's process-of-record (POR) documents from the Hillsboro fabrication facility.

Assessment: Likely met by both accused products. Confidence: Moderate (pending confirmation through discovery of precise cladding layer thickness).

Limitation [1e]: "wherein the tapered silicon waveguide is adiabatically coupled to the silicon nitride waveguide layer such that an optical mode propagating in the silicon nitride waveguide layer is gradually transferred to the tapered silicon waveguide through evanescent field interaction along the longitudinal axis"

This is the critical disputed limitation in the infringement analysis. The construction and application of the term "adiabatically coupled" will likely determine the outcome of the entire '567 Patent infringement theory.

The Claim Requirement. The '567 Patent claims require that the tapered silicon waveguide is "adiabatically coupled" to the silicon nitride waveguide layer, meaning that the optical mode transitions gradually from the silicon nitride waveguide to the silicon waveguide without significant power loss and without exciting higher-order modes. The claim further specifies that this transfer occurs "through evanescent field interaction along the longitudinal axis," indicating that the coupling is mediated by the evanescent field extending between the two waveguide layers over the length of the taper.

Lumos's Design. Based on the available technical literature, conference presentations by Dr. Mei-Lin Chen and Dr. Nikolai Petrov, and preliminary reverse-engineering analysis of the LumosBridge™ platform conducted by our technical consultant (Dr. Harold Whitfield, discussed further in Section X), Lumos appears to employ a segmented (non-continuous) taper design with discrete coupling sections rather than a single gradual continuous taper. Specifically:

• Lumos's coupler design uses multiple discrete taper segments, each with its own geometric profile, separated by transition regions where the taper width exhibits step-like discontinuities or abrupt changes in taper slope.

• This multi-segment architecture creates a stepped or segmented coupling geometry in which the optical mode transitions through a series of discrete coupling stages rather than through a single smooth, continuous taper.

• This approach is sometimes referred to in the silicon photonics literature as a "multi-section coupler" or "segmented taper coupler." The Chen & Liu (2016) reference — which was cited during prosecution of the '567 Patent — is a representative description of this type of design.

• Dr. Mei-Lin Chen's presentation at the 2022 Photonics West conference (SPIE Proceedings, Vol. 12007, Paper 12007-24, February 2022) describes Lumos's coupler architecture as utilizing "optimized multi-segment taper profiles" to achieve "broadband low-loss coupling," language that is consistent with a segmented rather than continuously adiabatic design approach.

Claim Construction Risk. Whether Lumos's segmented taper design satisfies the "adiabatically coupled" limitation depends entirely on how the Court construes that term. The parties are expected to advance competing constructions:

Lumos's Expected Proposed Construction: "Coupled through a gradual, continuous taper that prevents excitation of higher-order modes throughout the entire transition region." Under this narrow, structurally focused construction, Lumos's segmented taper design — which introduces discrete discontinuities between taper sections — would likely fall outside the scope of the claim. The presence of step-like transitions between segments means the taper is not "continuous" in the structural sense, and the discontinuities between segments could theoretically excite higher-order modes at the transition points (even if the overall coupling efficiency remains high).

OWS's Proposed Construction: "Coupled such that optical mode transitions occur without significant power loss." Under this broader, functionally focused construction, the inquiry would center on whether the coupling achieves the functional result of low-loss mode transition, regardless of whether the taper geometry is continuous or segmented. If Lumos's segmented taper achieves coupling with minimal power loss (which publicly available data suggests it does), the limitation would be met under this construction.

Assessment: Under OWS's proposed broader construction — likely met by both accused products. Under a narrow construction requiring a continuous, gradual taper without structural discontinuities — likely NOT met by either accused product. Risk Level: HIGH. This limitation is the principal vulnerability of the '567 Patent infringement theory and the single most important issue for the litigation team to address in claim construction preparation.

Limitation [1f]: "wherein the integrated optical coupler is configured to receive light from an optical fiber and couple the received light into the tapered silicon waveguide with an insertion loss of less than 1.5 dB per facet"

This limitation requires that the integrated optical coupler is configured for fiber-to-chip coupling with an insertion loss of less than 1.5 dB per coupling facet. This performance specification reflects the low-loss coupling capability that is a key advantage of the claimed adiabatic coupler architecture.

Both accused Lumos products are designed for fiber-to-chip light coupling in transceiver applications, and both are marketed as achieving low insertion loss at the fiber-to-chip interface. Lumos's product datasheets for the LumosBridge™ 800G and LumosEdge™ 400ZR+ report fiber-to-chip coupling losses of approximately 0.8 to 1.2 dB per facet, which falls within the claimed range. Dr. Nikolai Petrov's published paper in IEEE Photonics Technology Letters (2021) reports measured coupling losses of "less than 1.0 dB per facet" for Lumos's silicon photonics coupler design. These performance figures are consistent with the sub-1.5 dB per facet requirement of Claim 1.

Assessment: Met by both accused products. Confidence: High.

B. Claim 4 Analysis

Claim 4 depends from Claim 1 and therefore inherits all of the limitations — and associated vulnerabilities — of Claim 1, including the critical "adiabatically coupled" limitation analyzed above. The additional limitations introduced by Claim 4 are analyzed below.

Limitation [4a]: Taper length between 100 micrometers and 500 micrometers

Claim 4 requires that the tapered silicon waveguide has a taper length of between 100 micrometers and 500 micrometers. Publicly available design information for Lumos's silicon photonics coupler suggests taper lengths in the range of approximately 150 to 350 micrometers, which falls within the claimed range. This is consistent with typical industry designs, as taper lengths in this range are necessary to achieve efficient adiabatic mode conversion while maintaining a reasonable chip footprint. Exact taper length dimensions for Lumos's products are not publicly available and will require confirmation through discovery.

Assessment: Likely met. Confidence: Moderate (pending discovery confirmation).

Limitation [4b]: Cross-sectional height between 150 nanometers and 340 nanometers

Claim 4 further requires that the tapered silicon waveguide has a cross-sectional height of between 150 nanometers and 340 nanometers along the longitudinal axis. Standard silicon photonics fabrication processes on SOI substrates typically employ silicon waveguide layer thicknesses of 220 nanometers (the most common standard) or 300 nanometers, both of which fall within the claimed range. Lumos's Hillsboro fabrication facility is understood to use a SOI process with a silicon device layer thickness of approximately 220 nanometers, based on publicly available process descriptions and industry analysis reports.

Assessment: Likely met. Confidence: Moderate-to-High.

Overall Claim 4 Assessment: The viability of Claim 4 depends entirely on the construction of the "adiabatically coupled" limitation inherited from Claim 1. If that limitation is met, the additional limitations of Claim 4 are also likely met. If the "adiabatically coupled" limitation is not met under the Court's construction, Claim 4 fails regardless of the additional limitations.

C. Claim 7 Analysis

Claim 7 depends from Claim 1 and adds limitations related to the silicon nitride waveguide layer dimensions and coupling efficiency specifications.

Limitation [7a]: Silicon nitride waveguide width between 2 micrometers and 12 micrometers at input facet

The silicon nitride waveguide layer in Lumos's products is expected to have a width at the input facet that falls within this broad range. Silicon nitride waveguides used for fiber coupling in silicon photonics are typically designed with input facet widths in the range of approximately 3 to 10 micrometers, depending on the fiber mode field diameter and the desired coupling efficiency. Dr. Mei-Lin Chen's OFC 2021 presentation references SiN waveguide widths "optimized for standard single-mode fiber coupling," which is consistent with widths in the claimed range.

Assessment: Likely met. Confidence: Moderate (pending discovery).

Limitation [7b]: Coupling efficiency exceeding 90% over wavelength range of 1260 nm to 1360 nm

This limitation requires that the coupling efficiency between the silicon nitride waveguide layer and the tapered silicon waveguide exceeds 90% over the O-band wavelength range (1260 nm to 1360 nm). Lumos's products are designed for operation at O-band wavelengths (particularly 1310 nm, which is the standard wavelength for data center interconnect applications), and Lumos's published performance data indicates coupling efficiencies that are consistent with exceeding the 90% threshold. The insertion loss figures published by Lumos (0.8 to 1.2 dB per facet) correspond to coupling efficiencies of approximately 76% to 83% on a per-facet basis; however, the Claim 7 limitation refers specifically to the coupling efficiency between the SiN waveguide and the silicon waveguide (not the overall fiber-to-chip insertion loss), which is typically higher than the overall system insertion loss. Exact coupling efficiency measurements between the waveguide layers will require discovery.

Assessment: Likely met, but requires confirmation. Confidence: Moderate.

Overall Claim 7 Assessment: Same posture as Claim 4. Viability depends on the construction of the "adiabatically coupled" limitation inherited from Claim 1.

D. Claim 12 Analysis (Independent)

Claim 12 is the second independent claim and is directed to an "optical transceiver system" that incorporates the integrated waveguide coupler within a broader transceiver architecture. Each limitation is analyzed below.

Limitation [12a]: "An optical transceiver system" (Preamble)

Both the LumosBridge™ 800G Optical Engine and the LumosEdge™ 400ZR+ Pluggable Transceiver are optical transceiver systems — they transmit and receive optical signals for data communication. This preamble limitation is clearly met by both products.