PRIVILEGED & CONFIDENTIAL — ATTORNEY WORK PRODUCT EXPERT ENGAGEMENT COMMUNICATION
CALDERWOOD & HARKNESS LLP intellectual Property Group One Embarcadero Center, 34th Floor San Francisco, California 94111
August 18, 2022
MEMORANDUM
TO: Dr. Harold Whitfield Whitfield Technical Consulting Group, Inc. 530 Lytton Avenue, Suite 210 Palo Alto, California 94301
FROM: Alan Ngo, Partner, and Omar Siddiqui, Senior Associate Intellectual Property Group Calderwood & Harkness LLP
RE: Scope of Technical Expert Engagement — Optiwave Semiconductor Corp. v. Lumos Photonics, Inc., Case No. 5:22-cv-03417-EJD (N.D. Cal.)
C&H MATTER NO.: 1014-00003
CONFIDENTIALITY NOTICE: This memorandum is protected by attorney-client privilege and the work product doctrine. It is furnished to Dr. Harold Whitfield in connection with his retention as a consulting and testifying expert and is subject to the terms of the Expert Retention Agreement dated August 2022. This memorandum and its attachments contain confidential information and may not be disclosed, reproduced, or distributed to any person or entity other than Dr. Whitfield and his designated support personnel without the prior written consent of Calderwood & Harkness LLP.
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I. PURPOSE
This memorandum outlines the scope, objectives, and parameters of Dr. Harold Whitfield's engagement as a technical expert on behalf of Optiwave Semiconductor Corp. ("OWS" or "Optiwave") in patent infringement litigation captioned Optiwave Semiconductor Corp. v. Lumos Photonics, Inc., Case No. 5:22-cv-03417-EJD, currently pending before the Honorable Edward J. Torvelis in the United States District Court for the Northern District of California, San Jose Division. The defendant in this action is Lumos Photonics, Inc. ("Lumos" or "LPI").
The purpose of this memorandum is to identify, with specificity, the four United States patents asserted in this litigation (the "Patents-in-Suit"), the accused products manufactured and sold by Lumos, the key claim terms that we anticipate will be the subject of dispute during the forthcoming claim construction proceedings, the expected timeline and key deadlines, and the comprehensive set of background materials being provided to Dr. Whitfield to enable him to commence his review and analysis.
Dr. Whitfield's engagement encompasses two primary phases:
(1) Phase 1 — Claim Construction Support. This phase encompasses Dr. Whitfield's review and analysis of the intrinsic record for each Patent-in-Suit, the formulation of opinions regarding the understanding of a person of ordinary skill in the art ("POSITA") with respect to the disputed claim terms, the preparation and submission of a declaration in support of OWS's Opening Claim Construction Brief, and the preparation and delivery of a technical tutorial presentation for the Court at the Markman hearing scheduled for January 30, 2023. Phase 1 also includes consulting with the Calderwood & Harkness litigation team in analyzing and rebutting Lumos's claim construction positions.
(2) Phase 2 — Infringement Analysis Support. This phase, which is contingent upon the outcome of the Markman hearing and the resulting claim constructions, will involve element-by-element infringement analysis of the accused Lumos products, preparation of an expert report under Federal Rule of Civil Procedure 26(a)(2)(B), and availability for deposition and trial testimony.
Each of these phases is described in greater detail in Section VI of this memorandum. We turn first to the factual and procedural background of the litigation.
II. BACKGROUND OF THE LITIGATION
A. The Parties
1. Plaintiff — Optiwave Semiconductor Corp. ("OWS")
Optiwave Semiconductor Corp. is a Delaware corporation headquartered at 2775 Augustine Drive, Suite 400, San Jose, California 95054. OWS is a fabless semiconductor design company specializing in the design and development of silicon photonics integrated circuits for high-speed data center interconnect and telecommunications applications. The company was founded in 2014 by Dr. Priya Ramanathan and Dr. Kevin Fong, and it has grown rapidly in the intervening years, reporting fiscal year 2022 revenue of approximately $187.4 million and employing approximately 620 individuals.
OWS's key commercial products include the OWS-400ZR and OWS-800LR coherent optical transceiver chipsets, as well as integrated silicon photonics engines designed for co-packaged optics architectures increasingly demanded by hyperscale data center operators. These chipsets are fabricated by Pinnacle Semiconductor Foundry Co., Ltd., a major overseas foundry, on a 45nm silicon-on-insulator ("SOI") process. OWS does not operate its own fabrication facilities; it is a "fabless" design house that contracts the manufacturing of its chips to third-party foundries.
OWS has developed a significant intellectual property portfolio comprising eighty-seven (87) issued United States utility patents and fourteen (14) pending patent applications. The portfolio is concentrated in several core technology areas, including waveguide coupling architectures, germanium-on-silicon photodetector design, modulator driver circuit architectures, and related aspects of silicon photonics integrated circuit design and fabrication.
OWS is majority-owned, with an approximately sixty-two percent (62%) equity stake, by Vantage Point Capital Partners Fund IV, LP, a venture capital fund based in Menlo Park, California. The remaining equity is held by the founders, employees, and other institutional investors.
The key personnel relevant to this engagement are as follows:
• Chief Executive Officer: Dr. Priya Ramanathan, co-founder, who holds a Ph.D. in Electrical Engineering with a specialization in photonics from Stanford University.
• Chief Technology Officer: Dr. Kevin Fong, co-founder, who previously served as a principal engineer at a major semiconductor foundry before co-founding OWS. Dr. Fong is a named inventor on three of the four Patents-in-Suit.
• General Counsel: Sandra Ellison.
• Vice President of intellectual Property: Theodore "Ted" Marchetti, a registered patent attorney (USPTO Reg. No. 58,304) and former patent examiner at the United States Patent and Trademark Office, where he served in Art Unit 2828 (optoelectronics and photonics technologies).
2. Defendant — Lumos Photonics, Inc. ("Lumos" or "LPI")
Lumos Photonics, Inc. is a Delaware corporation headquartered at 9400 McNeil Drive, Building 7, Austin, Texas 78758. Unlike OWS, Lumos is an integrated device manufacturer ("IDM") — meaning it designs, fabricates, and packages its own silicon photonics components. Lumos operates a fabrication facility located at 3200 NE Shute Road, Hillsboro, Oregon 97124, and maintains a local sales office and engineering center at 4750 Great America Parkway, Suite 320, Santa Clara, California 95054, which provides the basis for personal jurisdiction in this district.
Lumos was founded in 2016 and focuses on the design, manufacturing, and sale of silicon photonics components for hyperscale data center applications. The company has experienced rapid revenue growth, reporting fiscal year 2022 revenue of approximately $312.8 million and employing approximately 1,450 individuals across its operations. Lumos became a publicly traded company in 2021 when it completed an initial public offering on the Nasdaq stock exchange under the ticker symbol "LMPH." As of the filing of OWS's complaint on June 3, 2022, Lumos's market capitalization was approximately $1.87 billion.
The key personnel at Lumos relevant to this engagement are as follows:
• Chief Executive Officer: James "Jim" Harrelson.
• Chief Technology Officer: Dr. Mei-Lin Chen, who holds a Ph.D. in Applied Physics from the Massachusetts Institute of Technology and is a named inventor on fourteen (14) patents in her own name relating to photonics technologies.
• General Counsel: Richard Talbot.
• Vice President of Engineering, Photonics Division: Dr. Nikolai Petrov.
Lumos is represented in this litigation by the law firm of Brannick Howell & Stein LLP. We understand that Lumos has retained Dr. Raymond Ng, a former professor of photonics at the University of Colorado Boulder and currently serving as Of Counsel to Brannick Howell & Stein LLP, as its technical consultant for claim construction purposes.
B. Procedural Posture
The procedural history of this case to date is as follows:
OWS filed its Complaint for Patent Infringement on June 3, 2022, in the United States District Court for the Northern District of California, San Jose Division. The case was assigned to the Honorable Edward J. Torvelis and designated as Case No. 5:22-cv-03417-EJD. The Complaint asserts infringement of four United States patents: U.S. Patent Nos. 10,234,567; 10,891,234; 11,045,678; and 11,312,890 (collectively, the "Patents-in-Suit"), as described in detail in Section III below.
Lumos was served with the Complaint on June 28, 2022, via its registered agent, Ashgrove Services Inc.. Lumos timely filed its Answer and Counterclaims on July 29, 2022. In its Answer, Lumos denied each substantive allegation of infringement and raised numerous affirmative defenses. Lumos's Counterclaims seek declaratory judgments of non-infringement and invalidity under 35 U.S.C. §§ 102 (anticipation), 103 (obviousness), and 112 (written description and enablement). The invalidity counterclaims signal a potentially aggressive defense strategy, and we anticipate that Lumos will pursue invalidity contentions in parallel with its non-infringement positions as the case progresses.
The Court held the Initial Case Management Conference on August 15, 2022, and issued a Case Management Order establishing the following schedule for claim construction proceedings:
• September 12, 2022: OWS's Preliminary Claim Construction Contentions due under Patent Local Rule 4-1.
• October 3, 2022: Responsive Claim Construction Contentions due under Patent Local Rule 4-2.
• October 14, 2022: Joint Claim Construction and Prehearing Statement due under Patent Local Rule 4-3.
• October 31, 2022: Close of claim-construction-related discovery.
• December 5, 2022: Opening Claim Construction Brief due.
• December 19, 2022: Responsive Claim Construction Brief due.
• January 9, 2023: Reply Brief due.
• January 30, 2023: Markman Hearing before the Honorable Edward J. Torvelis.
Initial disclosures under Federal Rule of Civil Procedure 26(a)(1) are being exchanged on August 22, 2022. A Stipulated Protective Order is currently being negotiated between the parties and is expected to be entered by the Court in early September 2022. A copy of the Protective Order will be provided to Dr. Whitfield once entered.
C. Pre-Suit History
Prior to the filing of this action, OWS undertook the following steps:
On March 15, 2022, OWS, through its Vice President of intellectual Property, Theodore Marchetti, sent a detailed cease-and-desist letter to Lumos's General Counsel, Richard Talbot, identifying U.S. Patent Nos. 10,234,567 (the '567 Patent) and 10,891,234 (the '234 Patent) and providing a preliminary claim chart mapping the claims of those two patents to Lumos's publicly available product documentation for the LumosBridge™ 800G Optical Engine and the LumosEdge™ 400ZR+ Pluggable Transceiver. The letter demanded that Lumos cease manufacturing and selling the accused products and invited Lumos to enter into licensing discussions.
Lumos, through its outside counsel at Brannick Howell & Stein LLP, responded on April 4, 2022, categorically denying infringement of either identified patent and affirmatively asserting that OWS's patents are invalid in view of the prior art. Lumos declined to enter into licensing negotiations and did not alter its course of conduct with respect to the accused products.
Following receipt of Lumos's response, OWS's General Counsel, Sandra Ellison, and VP of IP, Ted Marchetti, in consultation with Calderwood & Harkness, presented the matter to the OWS Board of Directors. The Board authorized the filing of a patent infringement action against Lumos on April 28, 2022. Vantage Point Capital Partners, as the majority equity holder, concurred in the decision to proceed with litigation.
Calderwood & Harkness's engagement letter was executed by OWS on May 12, 2022, and the firm commenced its pre-filing investigation and preparation of the Complaint, which was filed on June 3, 2022.
III. THE PATENTS-IN-SUIT
OWS's Complaint asserts infringement of four United States patents, each of which is described below. For each patent, we provide the title, filing and issuance dates, named inventors, the specific claims asserted, the key claim terms anticipated to be disputed during claim construction, and relevant highlights of the prosecution history.
A. U.S. Patent No. 10,234,567 (the "'567 Patent")
Title: "Integrated Waveguide Coupler with Tapered Mode Converter for Silicon Photonics Platforms"
Filing Date: March 14, 2017
Issue Date: March 19, 2019
Named Inventors: Dr. Kevin Fong; Dr. Priya Ramanathan; Hideo Tanaka
Assignment: Assigned to Optiwave Semiconductor Corp.
The '567 Patent is directed to an integrated optical coupler designed for use in silicon photonics platforms. The patented coupler employs a tapered mode converter architecture that facilitates efficient optical coupling between a silicon waveguide and a silicon nitride waveguide layer. The tapered silicon waveguide has a tip width engineered to be less than 200 nanometers, and the coupling between the silicon and silicon nitride waveguide layers is achieved through an adiabatic transition — a gradual, low-loss transfer of the optical mode from one waveguide to the other.
Asserted Claims. OWS asserts Claims 1, 4, 7, 12, and 15 of the '567 Patent. Independent Claim 1 is directed to an integrated optical coupler comprising a tapered silicon waveguide having a tip width of less than 200 nanometers adiabatically coupled to a silicon nitride waveguide layer. Claims 4, 7, 12, and 15 are dependent claims that add further structural and functional limitations to the coupler architecture.
Key Anticipated Disputed Term. The term "adiabatically coupled" is anticipated to be the central term in dispute during claim construction of the '567 Patent. This term was added during prosecution to overcome a prior art rejection. The prior art reference at issue was U.S. Patent No. 9,456,012, issued September 6, 2016, to Tanaka et al. (the "Tanaka '012 Patent"). Notably, the Tanaka '012 Patent was co-invented by Hideo Tanaka, who is also a named inventor on the '567 Patent. Hideo Tanaka was employed by OWS from 2016 to 2019, but the Tanaka '012 Patent was filed and issued prior to his joining OWS, based on work performed at his prior employer. The circumstances surrounding Mr. Tanaka's involvement in both inventions may be a point of interest during discovery.
Prosecution History Highlights. The '567 Patent was the subject of two Office Action rejections during prosecution before the USPTO. In the first Office Action, the examiner rejected the claims as anticipated by and/or obvious over the Tanaka '012 Patent, as well as over the Chen & Liu reference ("Segmented Taper Coupler Design for Low-Loss Fiber-to-Chip Coupling," Journal of Photonic Integration, Vol. 14, No. 3, pp. 217–229 (2016)). The claims were amended during prosecution to include the "adiabatically coupled" limitation, and the applicant argued that this limitation distinguished the claimed invention from the segmented-taper approach disclosed in the prior art. The claims were allowed after the second Office Action. Given the claim amendments and arguments made during prosecution, we anticipate that Lumos will raise prosecution history estoppel arguments to limit the scope of "adiabatically coupled" and to argue that it excludes the segmented taper design employed in Lumos's accused products. This will be a critical issue for Dr. Whitfield's claim construction analysis.
B. U.S. Patent No. 10,891,234 (the "'234 Patent")
Title: "Germanium-on-Silicon Photodetector with Graded Buffer Layer for Enhanced Responsivity"
Filing Date: September 8, 2017
Issue Date: January 14, 2021
Named Inventors: Dr. Kevin Fong; Dr. Amara Osei
Assignment: Assigned to Optiwave Semiconductor Corp.
The '234 Patent is directed to a germanium-on-silicon photodetector structure that employs a graded buffer layer between the silicon substrate and the germanium active region. The graded buffer layer is engineered to reduce threading dislocation density at the germanium/silicon interface, which in turn enhances the responsivity and performance of the photodetector. The patent specification describes the buffer layer as having a "continuously varying germanium concentration" that transitions from the silicon substrate composition to the pure germanium (or high-germanium-fraction) active region.
Asserted Claims. OWS asserts Claims 1, 3, 5, 8, and 11 of the '234 Patent. The asserted claims are directed to the photodetector structure and specifically recite the "graded buffer layer having a continuously varying germanium concentration."
Key Anticipated Disputed Term. The term "graded buffer layer having a continuously varying germanium concentration" is anticipated to be the principal term in dispute for the '234 Patent. The core question will be whether "continuously varying" encompasses step-graded buffer layer designs — in which the germanium concentration is increased in discrete, incremental steps rather than in a smooth, continuous gradient — or whether the term is limited to truly continuous (smooth) compositional gradients. The specification of the '234 Patent contains embodiments describing both "continuously graded" and "step-graded" buffer layers, but the claim language recites only "continuously varying." This discrepancy between the claims and the specification will be a focal point of the claim construction dispute.
Prosecution History Highlights. Unlike the '567 Patent, the '234 Patent has a relatively clean prosecution history. The claims were allowed on the first Office Action following an examiner interview conducted with the applicant's counsel and the named inventors. No substantive amendments were made to the claims during prosecution, and the prosecution history does not contain the type of narrowing statements or disclaimer language that would create prosecution history estoppel issues. This clean prosecution history will be advantageous to OWS in arguing for a broader construction of the disputed term.
C. U.S. Patent No. 11,045,678 (the "'678 Patent")
Title: "Multi-Channel Optical Transceiver with Integrated Wavelength-Division Multiplexing on Silicon"
Filing Date: June 22, 2018
Issue Date: June 29, 2021
Named Inventors: Dr. Priya Ramanathan; Dr. Amara Osei; Liwei Zhang
Assignment: Assigned to Optiwave Semiconductor Corp.
The '678 Patent is directed to a multi-channel optical transceiver architecture that integrates a wavelength-division multiplexing ("WDM") element monolithically on a single silicon die. The patent teaches an approach in which all of the key optical components — including lasers, modulators, multiplexers/demultiplexers, and photodetectors — are fabricated as part of a unified semiconductor process on a common silicon substrate, avoiding the need for hybrid integration techniques in which separately fabricated optical components are assembled onto a silicon interposer or substrate.
Asserted Claims. OWS asserts Claims 1, 2, 6, 9, and 14 of the '678 Patent. Independent Claim 1 recites an "integrated wavelength-division multiplexing element monolithically formed on a single silicon die."
Key Anticipated Disputed Term. The term "integrated wavelength-division multiplexing element monolithically formed on a single silicon die" — and particularly the word "monolithically formed" — is anticipated to be the central term in dispute for the '678 Patent. The dispute will center on whether "monolithically formed" encompasses heterogeneous integration techniques, such as micro-transfer printing or wafer bonding of III-V gain materials onto a silicon photonic integrated circuit, or whether it is limited to components fabricated entirely through a single, unified semiconductor process on a single silicon die.
Prosecution History Highlights. The '678 Patent was the subject of three Office Actions during prosecution. The examiner initially rejected the claims over prior art references disclosing hybrid integration approaches for WDM-on-silicon architectures. In response, the applicant amended the claims to add the "monolithically formed" limitation and argued that the present invention is "distinguished from heterogeneous integration approaches" in which separately fabricated III-V components are bonded or transferred onto a silicon substrate. Specifically, the applicant's remarks stated: "the present invention is distinguished from heterogeneous integration approaches." This amendment and the accompanying remarks present a significant prosecution history estoppel issue for OWS. We anticipate that Lumos will argue that the applicant disclaimed heterogeneous integration during prosecution, and that the term "monolithically formed" must therefore be construed to exclude Lumos's accused products, which employ micro-transfer-printed III-V gain elements bonded to the silicon photonic integrated circuit. Dr. Whitfield's analysis of the technical distinction between monolithic integration and heterogeneous integration will be critical to this claim construction dispute.
D. U.S. Patent No. 11,312,890 (the "'890 Patent")
Title: "Driver Circuit Architecture for High-Speed Silicon Photonic Mach-Zehnder Modulators"
Filing Date: November 15, 2018
Issue Date: April 26, 2022
Named Inventors: Dr. Kevin Fong; Rajesh Iyer
Assignment: Assigned to Optiwave Semiconductor Corp.
The '890 Patent is directed to a driver circuit architecture specifically designed for high-speed silicon photonic Mach-Zehnder modulators. The patent teaches a pre-emphasis equalization stage that is electrically co-integrated with the Mach-Zehnder modulator on a common substrate, enabling high-bandwidth signal conditioning without the parasitic losses associated with off-chip or separately bonded driver circuits.
Asserted Claims. OWS asserts Claims 1, 5, 8, and 13 of the '890 Patent. Independent Claim 1 recites a "pre-emphasis equalization stage electrically co-integrated with the modulator on a common substrate."
Key Anticipated Disputed Term. The term "pre-emphasis equalization stage electrically co-integrated with the modulator on a common substrate" — and specifically the phrase "co-integrated" — is anticipated to be the central term in dispute for the '890 Patent. The dispute will focus on whether "co-integrated" merely requires that the driver circuit and modulator be located on the same substrate (i.e., physically co-located, potentially via flip-chip bonding or other assembly techniques), or whether it requires that the driver circuit and modulator be fabricated in the same semiconductor process (i.e., sharing doping profiles, process layers, and fabrication steps, without bond wires, interposers, or flip-chip bonding).
Prosecution History Highlights. The '890 Patent was the subject of two Office Actions during prosecution. The "co-integrated" limitation was added by amendment to distinguish the claimed invention from prior art disclosing driver circuits that are separately fabricated and then bonded to the modulator die. The applicant argued that co-integration provides superior performance due to the elimination of parasitic inductance and capacitance associated with bonded interconnections. As with the '567 and '678 Patents, we anticipate prosecution history estoppel arguments from Lumos regarding the scope of this limitation, particularly given that Lumos's accused products employ a separate CMOS driver die that is flip-chip bonded to the silicon photonic modulator die via copper pillar micro-bumps.
IV. ACCUSED PRODUCTS
OWS accuses two Lumos product families of infringing the Patents-in-Suit. Both are described below, along with the specific technical features relevant to the infringement analysis for each asserted patent.
A. LumosBridge™ 800G Optical Engine
The LumosBridge™ 800G Optical Engine is a co-packaged optics engine designed for use in hyperscale data center switch architectures. The product provides 800 Gbps of aggregate optical bandwidth through multiple optical channels integrated into a compact, energy-efficient optical engine module that is designed to be co-packaged directly with switch ASICs on a common substrate or interposer.
The LumosBridge 800G was first shipped to customers in Q1 2022 and is currently Lumos's flagship product offering. It is sold at a unit price range of approximately $1,200 to $1,800, depending on the specific configuration and customer volume commitments.
The following technical features of the LumosBridge 800G are relevant to the infringement analysis for each of the four Patents-in-Suit:
• Waveguide Coupling Architecture (relevant to '567 Patent, "adiabatically coupled" term): The LumosBridge 800G uses a segmented (non-continuous) taper design with discrete coupling sections, rather than a smooth, continuously tapered waveguide structure. Based on publicly available product documentation and technical presentations, the coupling architecture employs multiple distinct taper segments with abrupt dimensional transitions between segments. This design is directly implicated by the claim construction dispute over the term "adiabatically coupled" — if the term is construed broadly (OWS's position) to encompass any coupling that achieves low-loss optical mode transition regardless of taper geometry, Lumos's segmented taper may infringe; if construed narrowly (anticipated defense position) to require a continuous taper throughout the entire transition region, Lumos's segmented taper may be excluded.
• Photodetector Buffer Layer (relevant to '234 Patent, "continuously varying germanium concentration" term): The LumosBridge 800G uses a step-graded SiGe buffer layer between the silicon substrate and the germanium active region. The buffer consists of four discrete composition steps at germanium fractions of approximately 0.25, 0.50, 0.75, and 1.0. This step-graded architecture, as opposed to a continuously graded (smooth gradient) buffer, is the central technical feature implicated by the claim construction dispute over "continuously varying germanium concentration."
• WDM Integration Approach (relevant to '678 Patent, "monolithically formed" term): The LumosBridge 800G uses micro-transfer-printed III-V gain elements (e.g., InP-based laser sources) that are bonded to the silicon photonic integrated circuit ("PIC"). The III-V materials are fabricated on a separate donor wafer and then micro-transfer-printed onto the silicon PIC using an elastomeric stamp process. This approach is classified in the industry as a form of heterogeneous integration, as opposed to monolithic integration. The claim construction of "monolithically formed" will determine whether this heterogeneous integration approach falls within the scope of the asserted claims.
• Driver Circuit Architecture (relevant to '890 Patent, "co-integrated" term): The LumosBridge 800G uses a separate CMOS driver die that is flip-chip bonded to the silicon photonic modulator die via copper pillar micro-bumps. The driver circuit is not fabricated on the same substrate as the Mach-Zehnder modulator; rather, it is manufactured as a discrete CMOS chip and then assembled onto the modulator die through a flip-chip bonding process. The claim construction of "co-integrated" will determine whether this flip-chip bonded architecture satisfies the claim limitation.
B. LumosEdge™ 400ZR+ Pluggable Transceiver
The LumosEdge™ 400ZR+ Pluggable Transceiver is a QSFP-DD form factor pluggable optical transceiver module designed for metro and data center interconnect ("DCI") applications. The product has been in production since Q3 2021, making it the earlier of the two accused products to enter the market. It is sold at a unit price range of approximately $600 to $900, depending on configuration and customer volume.
The LumosEdge 400ZR+ shares relevant architectural features with the LumosBridge platform for purposes of the asserted patents. Specifically, both products employ the same or substantially similar waveguide coupling design, photodetector buffer layer architecture, WDM integration approach, and driver circuit configuration. The key technical differences between the two products relate primarily to channel count, aggregate bandwidth, and form factor — not to the underlying photonic integration architecture implicated by the Patents-in-Suit. Accordingly, for claim construction purposes, the analysis of the disputed terms will apply equally to both accused products.
C. Revenue Data
Based on Lumos's publicly filed Form 10-K for fiscal year 2022 and information obtained from Lumos's discovery responses, the combined revenue attributable to the two accused product families is as follows:
• Calendar Year 2022 (full year, estimated): Approximately $148.6 million in combined revenue from sales of the LumosBridge 800G and LumosEdge 400ZR+ products.
• Q1–Q2 2022 (pre-suit damages period, January 1 through June 2, 2022): Approximately $62.3 million in combined revenue from sales of the accused products.
These revenue figures will be relevant to the damages analysis, which is being conducted by Dr. Lawrence Kessler of Apex Claim Analytics LLC (Chicago, Illinois), who has been separately retained as OWS's damages expert. Dr. Whitfield's engagement does not extend to damages analysis or opinions, as discussed further in Section VI.C below.
V. KEY CLAIM TERMS ANTICIPATED TO BE DISPUTED
Based on our analysis of the Patents-in-Suit, the prosecution histories, the accused products, and Lumos's Answer and Counterclaims, we anticipate that the following claim terms will be the subject of dispute during claim construction proceedings. For each term, we set forth OWS's proposed construction, the construction we anticipate Lumos will advance, and a brief discussion of the nature of the dispute.
We note that the total number of disputed terms across all four patents is expected to reach approximately eleven (11), to be finalized in the Joint Claim Construction and Prehearing Statement under Patent Local Rule 4-3, due October 14, 2022. The terms identified below represent the primary disputed terms that we expect to be most consequential to the outcome of this litigation.
A. '567 Patent — Key Disputed Terms
Term 1: "adiabatically coupled" (Claims 1, 4, 7, 12, and 15)
OWS's Proposed Construction: Coupled such that optical mode transitions between the silicon waveguide and the silicon nitride waveguide layer occur without significant optical power loss — i.e., coupling in which the fundamental optical mode is transferred from one waveguide to the other with minimal scattering, radiation, or excitation of higher-order modes, regardless of the specific taper geometry employed.
Anticipated Defense Construction: Coupling achieved through a continuous, gradual taper that prevents excitation of higher-order modes throughout the entire transition region — i.e., a construction requiring a smooth, monotonically varying waveguide cross-section with no discrete steps or abrupt dimensional changes at any point in the transition region.
Nature of Dispute: The core dispute will center on whether the term "adiabatically coupled" is a functional descriptor referring to the performance characteristic of the coupling (low-loss mode transfer) or a structural descriptor requiring a specific taper geometry (continuous, gradual taper). If the term is construed broadly as a functional limitation, Lumos's segmented taper design — which may achieve low-loss coupling despite employing discrete coupling sections — could fall within the scope of the claims. If the term is construed narrowly as a structural limitation requiring a continuous taper, Lumos's segmented design may be excluded from literal infringement, though a doctrine-of-equivalents argument may remain available.
The prosecution history will be central to this dispute. The "adiabatically coupled" limitation was added during prosecution to overcome prior art that disclosed segmented taper designs. Lumos will likely argue that prosecution history estoppel prevents OWS from asserting a construction broad enough to encompass the very type of design that the applicant distinguished during prosecution. OWS will counter that the amendment was made to distinguish the prior art based on the coupling performance, not on the specific taper geometry, and that the prosecution history does not contain a clear disclaimer of segmented taper designs per se.
Additional Terms: We also anticipate that Lumos may seek construction of additional terms in Claims 1, 4, 7, 12, and 15, including "tip width of less than 200 nanometers" (potential dispute as to whether the measurement is taken at the narrowest point of the taper or at a designated measurement plane) and "silicon nitride waveguide layer" (potential dispute as to whether the term is limited to stoichiometric Si₃N₄ or encompasses silicon-rich silicon nitride and other compositional variants). These secondary terms are less likely to be outcome-determinative but should be addressed in Dr. Whitfield's analysis.
B. '234 Patent — Key Disputed Terms
Term 2: "graded buffer layer having a continuously varying germanium concentration" (Claims 1, 3, 5, 8, and 11)
OWS's Proposed Construction: A buffer layer interposed between the silicon substrate and the germanium active region in which the germanium concentration changes across the thickness of the layer — i.e., a buffer layer in which the atomic fraction of germanium varies from one value to a different value as a function of position within the layer, encompassing both continuously graded (smooth gradient) and step-graded (discrete incremental) architectures.
Anticipated Defense Construction: A buffer layer in which the germanium atomic fraction increases monotonically and without step changes — i.e., a smooth, continuous compositional gradient with no discrete transitions in germanium concentration at any point within the layer — thereby excluding step-graded buffer designs in which the germanium fraction changes abruptly at the boundaries between discrete composition layers.
Nature of Dispute: This dispute hinges on the meaning of the phrase "continuously varying." OWS will argue that "continuously varying" describes a concentration profile that changes (varies) throughout the layer (continuously, i.e., without interruption), which encompasses both smooth gradients and step-graded profiles with a sufficient number of steps. Lumos will argue that "continuously" modifies "varying" to require a smooth, uninterrupted gradient — akin to the mathematical concept of a continuous function — which excludes step-graded profiles with discrete concentration jumps.
The specification of the '234 Patent will be important here because it describes embodiments of both "continuously graded" and "step-graded" buffer layers. OWS will argue that the specification's disclosure of step-graded embodiments supports a broad construction that encompasses step-graded designs. Lumos will counter that the claim language specifically recites "continuously varying" rather than merely "varying" or "graded," and that the doctrine of claim differentiation and the applicant's deliberate choice of the word "continuously" limits the claim to smooth gradients. The relatively clean prosecution history of the '234 Patent (allowed on first Office Action after examiner interview) may favor OWS, as there are no narrowing amendments or disclaimer statements that would support a restrictive construction.
Additional Terms: We anticipate that Lumos may also dispute additional terms in Claims 1, 3, 5, 8, and 11, including terms relating to the specific structural parameters of the photodetector and the buffer layer. These additional disputed terms will be identified during the claim construction briefing process and will be addressed as they arise.
C. '678 Patent — Key Disputed Terms
Term 3: "integrated wavelength-division multiplexing element monolithically formed on a single silicon die" (Claims 1, 2, 6, 9, and 14)
OWS's Proposed Construction: A wavelength-division multiplexing component that is fabricated as part of the semiconductor fabrication process on a single silicon die — i.e., a WDM element that is produced during the wafer-level fabrication of the silicon photonic integrated circuit, regardless of whether heterogeneous integration techniques (such as wafer bonding or micro-transfer printing of III-V materials) are used during the fabrication process, provided that the resulting component is integral to and inseparable from the silicon die.
Anticipated Defense Construction: A WDM element fabricated entirely through a single, unified semiconductor process on a single silicon die, without the use of hybrid integration, flip-chip bonding, micro-transfer printing, wafer bonding, or any other heterogeneous integration technique — i.e., a construction that excludes any integration approach in which materials or components fabricated on a separate substrate are transferred to or bonded onto the silicon die.
Nature of Dispute: This is among the most consequential claim construction disputes in this case. The outcome will depend largely on the construction of the term "monolithically formed." In the semiconductor and photonics industry, "monolithic integration" is frequently understood to refer to fabrication using a single, unified process on a common substrate, as distinguished from "hybrid" or "heterogeneous" integration, in which separately fabricated components are assembled onto a common substrate. However, the boundaries between these concepts have become increasingly blurred as advanced integration techniques — such as micro-transfer printing and direct wafer bonding — have evolved to produce integrated structures that are functionally indistinguishable from monolithically fabricated devices.
The prosecution history presents a challenge for OWS on this term. The applicant added "monolithically formed" during prosecution specifically to distinguish from hybrid integration references, and the applicant's remarks stated that "the present invention is distinguished from heterogeneous integration approaches." Lumos will argue that this constitutes a clear disclaimer of heterogeneous integration, which would exclude Lumos's micro-transfer-printed III-V gain elements from the scope of the claims. OWS will need to argue either that the applicant's remarks were directed at a specific type of hybrid integration disclosed in the prior art (not all heterogeneous integration techniques) or that "monolithically formed" has a broader technical meaning than the applicant's prosecuting attorney may have appreciated.
Dr. Whitfield's testimony regarding the technical understanding of "monolithically formed" in the silicon photonics community will be critical to this dispute.
Additional Terms: Additional terms in Claims 1, 2, 6, 9, and 14 may also be disputed, including terms relating to the number and configuration of optical channels, the specific WDM architecture (e.g., arrayed waveguide grating vs. ring resonator-based multiplexer), and the definition of a "single silicon die." These additional terms will be finalized during the claim construction process.
D. '890 Patent — Key Disputed Terms
Term 4: "pre-emphasis equalization stage electrically co-integrated with the modulator on a common substrate" (Claims 1, 5, 8, and 13)
OWS's Proposed Construction: A pre-emphasis equalization circuit that is located on the same substrate as the Mach-Zehnder modulator — i.e., a driver circuit that resides on a common substrate with the modulator, whether fabricated as part of the same process or assembled onto the substrate through flip-chip bonding, interposer integration, or other co-packaging techniques.
Anticipated Defense Construction: A pre-emphasis equalization circuit that is fabricated in the same semiconductor process as the modulator, sharing common doping profiles and process layers, on the same substrate — i.e., a construction requiring same-process fabrication and excluding driver circuits that are separately manufactured and then bonded, wire-bonded, or otherwise assembled onto the modulator substrate.
Nature of Dispute: This dispute is analogous in structure to the "monolithically formed" dispute for the '678 Patent. The key question is whether "co-integrated" is a term of proximity (requiring only co-location on the same substrate) or a term of process (requiring fabrication using the same semiconductor process). The prosecution history, in which the "co-integrated" limitation was added to distinguish from separately fabricated driver circuits that are bonded to the modulator, will again raise prosecution history estoppel issues.
Lumos's accused products employ a separate CMOS driver die that is flip-chip bonded to the silicon photonic modulator die via copper pillar micro-bumps. Under OWS's proposed construction, this flip-chip bonded arrangement would satisfy the "co-integrated" limitation because the driver and modulator reside on a common substrate after assembly. Under Lumos's anticipated construction, the separately fabricated driver die would not meet the "co-integrated" requirement because it is not fabricated in the same process as the modulator.
Dr. Whitfield's opinion regarding the understanding of "co-integrated" in the electrical engineering and photonics communities — and specifically whether a person of ordinary skill in the art would understand the term to require same-process fabrication or merely co-location — will be central to the resolution of this dispute.
Additional Terms: Additional terms in Claims 1, 5, 8, and 13 may be disputed, including terms relating to the specific architecture and operating parameters of the pre-emphasis equalization stage (e.g., "pre-emphasis equalization," "common substrate," "electrically co-integrated"). These terms will be identified and addressed through the claim construction process.
Summary. As noted above, we anticipate that the total number of disputed terms across all four patents will reach approximately eleven (11). The four primary disputed terms identified above — "adiabatically coupled," "graded buffer layer having a continuously varying germanium concentration," "integrated wavelength-division multiplexing element monolithically formed on a single silicon die," and "pre-emphasis equalization stage electrically co-integrated with the modulator on a common substrate" — are expected to be the most consequential terms for the outcome of the claim construction proceedings. The final list of disputed terms will be set forth in the Joint Claim Construction and Prehearing Statement under Patent Local Rule 4-3, due October 14, 2022.
VI. SCOPE OF DR. WHITFIELD'S ENGAGEMENT
A. Phase 1: Claim Construction Support
Dr. Whitfield's engagement during Phase 1 encompasses the following tasks and deliverables:
1. Review of the Intrinsic Record
Dr. Whitfield will conduct a thorough review of the intrinsic record for all four Patents-in-Suit. The intrinsic record comprises the patent specifications (including the written descriptions, drawings, and abstracts), all claims (including both asserted and unasserted claims, as well as dependent claims), and the complete prosecution histories (file wrappers) for each of the four patents.
In addition, Dr. Whitfield will review all prior art of record cited during prosecution of the Patents-in-Suit. The prior art references of particular significance include:
(a) U.S. Patent No. 9,456,012 (Tanaka et al., issued September 6, 2016) — cited during prosecution of the '567 Patent as the basis for an anticipation and/or obviousness rejection. This reference is of particular importance because it was co-invented by Hideo Tanaka, who is also a named inventor on the '567 Patent.
(b) 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) — a journal article cited during prosecution of the '567 Patent that discloses a segmented taper coupling design relevant to the construction of "adiabatically coupled."
(c) European Patent Application EP 3,234,567 A1 (Nordlicht Photonische GmbH, published August 2, 2017) — a prior art reference cited during prosecution of the '678 Patent, relevant to the construction of "monolithically formed."
(d) Iyer & Patel, "Co-Design of Modulator Drivers and Silicon Photonic Mach-Zehnder Structures," IEEE Transactions on Circuits and Systems, Vol. 65, No. 8, pp. 2701–2713 (2018) — a journal article relevant to the construction of "co-integrated" in the '890 Patent.
Dr. Whitfield should also identify and review any additional prior art references that he considers relevant to the understanding of the disputed claim terms, whether cited in the prosecution histories or not. Such additional references may be used to establish the state of the art and the understanding of a person of ordinary skill in the art at the relevant time periods.
2. Definition of the Person of Ordinary Skill in the Art (POSITA)
Dr. Whitfield will formulate the definition of a person of ordinary skill in the art ("POSITA") for each of the four Patents-in-Suit, or a common definition across all four patents if Dr. Whitfield determines that the same definition is appropriate for the technologies at issue. The POSITA definition is a foundational element of claim construction, as the claims of a patent are construed from the perspective of a person of ordinary skill in the relevant art.
Based on our preliminary analysis, we expect that the POSITA for each of the four patents would be an individual holding a Ph.D. or M.S. degree in Electrical Engineering, Applied Physics, Materials Science, or a related field, with a specialization in silicon photonics or photonic integrated circuit design, and with approximately two to five (2–5) years of industry or postdoctoral experience in the design, fabrication, or characterization of photonic integrated circuits. However, Dr. Whitfield should apply his own independent judgment in formulating the POSITA definition, and we welcome his input on whether the definition should be adjusted to reflect the specific technology areas of each patent.
3. Declaration in Support of OWS's Opening Claim Construction Brief
Dr. Whitfield will prepare and provide a declaration opining on the understanding of a person of ordinary skill in the art with respect to each disputed claim term. The declaration will be submitted in support of OWS's Opening Claim Construction Brief, which is due on December 5, 2022.
The declaration should:
(a) Set forth Dr. Whitfield's qualifications, including his education, professional experience, publications, patents, and other credentials that qualify him to opine on the technologies at issue.
(b) Define the POSITA for the relevant technology area.
(c) For each disputed claim term, explain the technical background and context relevant to the term, describe how a POSITA would have understood the term at the time of the patent filing, and opine that OWS's proposed construction is consistent with the plain and ordinary meaning of the term as understood by practitioners in the field of integrated silicon photonics.
(d) Address relevant intrinsic evidence — including the patent specifications, claims, and prosecution histories — as they bear on the proper construction of each disputed term.
(e) Where appropriate, cite extrinsic evidence — including technical literature, industry standards, and the ordinary usage of the term in the field — to support the proposed construction.
We will work closely with Dr. Whitfield on the preparation of the declaration to ensure that it meets the legal requirements for expert declarations under Federal Rule of Civil Procedure and is consistent with the legal framework established by Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc), and its progeny.
4. Technical Tutorial Presentation
Dr. Whitfield will prepare a technical tutorial presentation designed to educate the Court on the underlying technology at the Markman hearing, currently scheduled for January 30, 2023, before the Honorable Edward J. Torvelis. The Northern District of California's Patent Local Rules and Judge Torvelis's standing order on patent cases contemplate the use of a technical tutorial at the Markman hearing to provide the Court with the technical background necessary to construe the disputed claim terms.
The technical tutorial should cover the following topics, at a level of detail accessible to a non-specialist federal judge:
(a) Silicon Photonics Fundamentals: An overview of the field of silicon photonics, including the advantages of using silicon as a platform for photonic integration, the basic components of a silicon photonic integrated circuit (waveguides, modulators, photodetectors, lasers), and the commercial applications of silicon photonics technology in data center interconnects and telecommunications.
(b) Waveguide Coupling Physics: An explanation of the physics of optical waveguide coupling, with particular emphasis on the distinction between adiabatic and non-adiabatic transitions. This section should explain the concept of an adiabatic mode transition (gradual transfer of optical mode without excitation of higher-order modes), the role of taper geometry in achieving adiabatic coupling, and the differences between continuous taper designs and segmented (non-continuous) taper designs.
(c) Germanium-on-Silicon Photodetector Architectures: An explanation of the use of germanium-on-silicon photodetectors in silicon photonic integrated circuits, including the challenges posed by the lattice mismatch between germanium and silicon, the role of buffer layers in managing threading dislocation density, and the distinction between continuously graded and step-graded buffer layer architectures.
(d) Monolithic vs. Heterogeneous Integration Techniques: An explanation of the different approaches to integrating optical components on a silicon photonic platform, including monolithic integration (fabrication of all components in a single, unified process), heterogeneous integration (bonding or transfer of III-V materials onto silicon), and hybrid integration (assembly of separately fabricated components onto a common substrate). This section should address recent developments in micro-transfer printing and wafer bonding technologies.
(e) Mach-Zehnder Modulator Driver Co-Integration Approaches: An explanation of the challenges of driver circuit design for high-speed silicon photonic Mach-Zehnder modulators, including the role of pre-emphasis equalization, the impact of parasitic inductance and capacitance on modulator performance, and the distinction between co-integrated driver architectures (fabricated on the same substrate as the modulator) and separately fabricated driver circuits that are assembled onto the modulator substrate through flip-chip bonding or other techniques.
The tutorial should be in the form of a Northgate Services Inc. (or equivalent) presentation, comprising approximately 40 to 60 slides. The presentation should be visually rich, with diagrams, cross-sectional illustrations, and annotated photographs where appropriate. It should be designed to be presented in approximately 60 to 90 minutes, allowing time for questions from the Court.
Dr. Whitfield will testify as OWS's technical tutorial witness at the Markman hearing. We will coordinate with Dr. Whitfield to schedule one or more rehearsal sessions in advance of the hearing to ensure a polished and effective presentation.
5. Consultation on Rebuttal
Dr. Whitfield will assist Calderwood & Harkness in analyzing and rebutting Lumos's claim construction positions, including any declaration or testimony submitted by Lumos's technical consultant, Dr. Raymond Ng. Dr. Ng is a former professor of photonics at the University of Colorado Boulder and is currently serving as Of Counsel to Brannick Howell & Stein LLP, Lumos's outside counsel. We expect Dr. Ng to submit a declaration in support of Lumos's Responsive Claim Construction Brief (due December 19, 2022) and potentially to serve as Lumos's technical tutorial witness at the Markman hearing.
Dr. Whitfield will review Dr. Ng's declaration and any other expert submissions from Lumos, provide his analysis and critique of Dr. Ng's opinions, and assist the Calderwood & Harkness team in preparing OWS's Reply Claim Construction Brief (due January 9, 2023). If Dr. Ng's declaration or testimony raises new technical issues or prior art references, Dr. Whitfield will be asked to address those issues as well.
B. Phase 2: Infringement Analysis (Contingent)
Phase 2 of Dr. Whitfield's engagement is contingent upon the outcome of the Markman hearing and the Court's claim construction order. The scope, timing, and deliverables for Phase 2 will be refined following the Markman hearing.
If the Court's claim constructions are favorable to OWS — i.e., if the constructions adopted are consistent with or close to OWS's proposed constructions, such that the accused Lumos products are not excluded by the constructions — Dr. Whitfield will be asked to undertake the following:
(a) Element-by-Element Infringement Analysis. Dr. Whitfield will provide a detailed element-by-element infringement analysis for all asserted claims of the four Patents-in-Suit against both the LumosBridge™ 800G Optical Engine and the LumosEdge™ 400ZR+ Pluggable Transceiver. The analysis will address both literal infringement and the doctrine of equivalents, as appropriate for each claim element.
(b) Review of discovery Materials. Dr. Whitfield will review Lumos's technical documentation produced during discovery, including design specifications, process flow documents, fabrication records, device characterization data, testing data, and any other technical materials relevant to the infringement analysis.
(c) Expert Report. Dr. Whitfield will prepare an expert report on infringement in compliance with Federal Rule of Civil Procedure 26(a)(2)(B). The report will set forth Dr. Whitfield's opinions, the bases and reasons for those opinions, the data and other information considered in forming the opinions, any exhibits to be used in support of or to summarize the opinions, Dr. Whitfield's qualifications and publications, a list of all cases in which Dr. Whitfield has testified as an expert (trial or deposition) within the preceding four years, and a statement of the compensation to be paid for the study and testimony.
(d) Deposition and Trial Testimony. Dr. Whitfield will be available for deposition by Lumos's counsel and for trial testimony on behalf of OWS, as required by the Court's scheduling order.
We will provide additional information regarding Phase 2 scope, timeline, and deliverables as they become clearer following the Markman hearing.
C. Exclusions
For clarity, the following matters are excluded from the scope of Dr. Whitfield's engagement:
(a) Invalidity Analysis. Dr. Whitfield's engagement does not include analysis or opinions regarding the validity or invalidity of any of the Patents-in-Suit. If invalidity issues require expert testimony, Calderwood & Harkness will retain a separate expert for that purpose or expand Dr. Whitfield's engagement by mutual agreement.
(b) Damages Analysis. Dr. Whitfield's engagement does not include analysis or opinions regarding damages, reasonable royalty rates, lost profits, or any other financial or economic matters. The damages analysis for this case is being conducted by Dr. Lawrence Kessler of Apex Claim Analytics LLC, located in Chicago, Illinois, who has been separately retained as OWS's damages expert.