DCT

3:24-cv-08165

Applied Optoelectronics Inc v. Eoptolink Technology USA Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 5:24-cv-08165, N.D. Cal., 03/07/2025
  • Venue Allegations: Plaintiff alleges venue is proper in the Northern District of California because Defendant Eoptolink has a regular and established place of business in the district, specifically a physical office in Fremont, and has allegedly committed acts of infringement within the district.
  • Core Dispute: Plaintiff alleges that Defendant’s optical transceiver products infringe six patents related to the mechanical and electrical design, component arrangement, and assembly of multi-channel optical transceivers.
  • Technical Context: The technology at issue involves high-speed, pluggable fiber-optic transceivers, which are critical components for the infrastructure of internet data centers, telecommunications networks, and cable television broadband.
  • Key Procedural History: The operative pleading is a First Amended Complaint, indicating this filing supersedes an original complaint in the action. The complaint alleges Defendant has had notice of the asserted patents and their infringement since the filing of the original complaint.

Case Timeline

Date Event
2012-12-10 ’367 Patent Priority Date
2013-05-14 ’433 Patent Priority Date
2016-09-20 ’367 Patent Issue Date
2016-11-29 ’433 Patent Issue Date
2017-03-30 ’470 Patent Priority Date
2018-10-05 ’818 Patent Priority Date
2019-02-06 ’890 Patent Priority Date
2019-03-12 ’470 Patent Issue Date
2020-01-08 ’887 Patent Priority Date
2020-03-03 ’818 Patent Issue Date
2020-07-14 ’890 Patent Issue Date
2021-11-16 ’887 Patent Issue Date
2025-03-07 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 9,448,367 - “Multi-Channel Optical Transceiver Module Including Dual Fiber Type Direct Link Adapter for Optically Coupling Optical Subassemblies in the Transceiver Module”

The Invention Explained

  • Problem Addressed: The patent’s background describes the challenge of fitting multi-channel transmitter optical subassemblies (TOSAs) and receiver optical subassemblies (ROSAs) into the relatively small form factors of modern optical line terminal (OLT) modules, noting that conventional optical connectors may not fit within the limited space (Compl., Ex. A, ’367 Patent, col. 1:56-65).
  • The Patented Solution: The invention proposes a "dual fiber type direct link adapter" which is directly linked with optical fibers to the internal TOSA and ROSA, while also being configured to receive standard pluggable external optical connectors, such as LC connectors. This integrated design aims to provide the necessary optical input and output for the transceiver in a space-efficient manner (’367 Patent, Abstract; col. 2:40-52).
  • Technical Importance: This approach allows for the construction of high-density, multi-channel transceivers that can be accommodated within standardized small form-factor modules essential for wavelength division multiplexing (WDM) passive optical networks (PONs) (’367 Patent, col. 1:47-55).

Key Claims at a Glance

  • The complaint asserts at least independent Claim 1 (Compl. ¶23).
  • The essential elements of Claim 1 include:
    • An adapter body portion defining connector receiving regions at a pluggable end and slots at a direct link end.
    • First and second direct link connector assemblies configured to be received in the slots, each defining an LC connector receptacle.
    • An adapter cover portion configured to cover the slots and retain the connector assemblies.
  • The complaint alleges infringement of "one or more claims" of the patent, reserving the right to assert other claims (Compl. ¶22).

U.S. Patent No. 9,509,433 - “Aligning and Directly Optically Coupling Photodetectors to Optical Demultiplexer Outputs in a Multichannel Receiver Optical Subassembly”

The Invention Explained

  • Problem Addressed: The patent addresses the difficulty of achieving high optical coupling efficiency between an optical demultiplexer (which separates different wavelengths of light) and an array of photodetectors within a compact receiver optical subassembly (ROSA). The background notes that limited space may preclude the use of fiber arrays or lenses, and that active alignment techniques can be expensive (’433 Patent, col. 1:65-col. 2:10).
  • The Patented Solution: The invention describes a ROSA where the outputs of the optical demultiplexer are "directly optically coupled" to the photodetectors without intermediate components like lenses or fiber arrays. This is achieved by designing the components, including the wire bonding points on the photodetectors, to avoid physical interference with this close coupling, and by using a passive alignment method to position the components accurately (’433 Patent, Abstract; col. 2:48-67).
  • Technical Importance: This design enables the creation of smaller, more sensitive ROSAs by maximizing coupling efficiency without the space requirements and manufacturing costs associated with traditional optical coupling and alignment methods (’433 Patent, col. 1:57-64).

Key Claims at a Glance

  • The complaint asserts at least independent Claims 1 and 13 (Compl. ¶33).
  • The essential elements of Claim 1 include:
    • A ROSA housing.
    • An optical demultiplexer located in the housing with multiple optical outputs.
    • An array of photodetectors located in the housing, spaced from the demultiplexer, and aligned with and "directly optically coupled" to the multiple optical outputs.
  • The complaint alleges infringement of "one or more claims" of the patent, reserving the right to assert other claims (Compl. ¶31).

U.S. Patent No. 10,230,470 - “Multilayered Flexible Printed Circuit with Both Radio Frequency (RF) and DC Transmission Lines Electrically Isolated from Each Other and an Optical Transceiver Using Same”

  • Technology Synopsis: This patent describes a multi-layered flexible printed circuit (FPC) designed to manage both high-frequency radio frequency (RF) data signals and direct current (DC) power/control signals within an optical transceiver (Compl. ¶4; ’470 Patent, Abstract). The invention uses separate insulating layers to route the RF and DC conductive traces, electrically isolating them to prevent interference, which reduces the need for multiple separate FPCs and saves space within the transceiver housing (’470 Patent, col. 3:15-29).
  • Asserted Claims: The complaint asserts at least Claims 1, 10, and 17 (Compl. ¶41).
  • Accused Features: The complaint alleges that the internal circuitry of the Eoptolink Technology USA Inc 100G QSFP LR4 products incorporates the claimed multi-layered FPC structure (Compl. ¶42).

U.S. Patent No. 10,578,818 - “Optical Transceiver”

  • Technology Synopsis: The patent discloses a mechanical design for an optical transceiver, focusing on the fastening mechanism used to secure it within a cage (Compl. ¶4; ’818 Patent, Abstract). The invention includes a main body with a confined groove, an elastic component (e.g., a spring) within the groove, and a movable fastening component with a linkage arm that presses on the elastic component to secure or release the transceiver (’818 Patent, col. 2:32-47).
  • Asserted Claims: The complaint asserts at least Claims 1 and 10 (Compl. ¶50).
  • Accused Features: The complaint alleges that the housing and fastening mechanisms of numerous Eoptolink 100G and 400G transceiver models infringe this patent (Compl. ¶51).

U.S. Patent No. 10,714,890 - “Transmitter Optical Subassembly Arrangement with Vertically-Mounted Monitor Photodiodes”

  • Technology Synopsis: This patent addresses the challenge of reducing the size of transmitter optical subassemblies (TOSAs) while maintaining signal quality (Compl. ¶4; ’890 Patent, Abstract). The solution involves a TOSA housing with a vertical mounting surface for a monitor photodiode (MPD), positioning the MPD above its associated laser diode (LD). This vertical arrangement frees up space adjacent to the LD, allowing conductive RF traces to be routed closer to the LD for shorter, higher-quality wire bond connections (’890 Patent, col. 3:1-15).
  • Asserted Claims: The complaint asserts at least Claim 1 (Compl. ¶59).
  • Accused Features: The complaint accuses the TOSA designs within the Eoptolink 100G QSFP LR4 products of infringement (Compl. ¶60).

U.S. Patent No. 11,177,887 - “Substrate with Stepped Profile for Mounting Transmitter Optical Subassemblies and an Optical Transmitter or Transceiver Implementing Same”

  • Technology Synopsis: The patent describes a substrate (e.g., a printed circuit board) with a "stepped profile" for mounting TOSA modules in an "on board" configuration (Compl. ¶4; ’887 Patent, Abstract). This profile creates a recessed mounting surface for the TOSA, which reduces the vertical distance between the TOSA's internal components (like a laser diode driver) and the RF terminals on the substrate. This design enables shorter electrical interconnects, such as wire bonds, which is critical for maintaining signal integrity at high data rates (’887 Patent, col. 3:20-46).
  • Asserted Claims: The complaint asserts at least Claims 1 and 10 (Compl. ¶68).
  • Accused Features: The complaint alleges that various Eoptolink 100G and 400G products utilize a substrate with the claimed stepped profile for mounting their optical components (Compl. ¶69).

III. The Accused Instrumentality

Product Identification

  • The accused products are a series of Eoptolink optical transceivers, including the 400G QSFP-DD LR4, 400G QSFP-DD FR4, 400G QSFP-DD DR4, 100G QSFP LR4, 100G QSFP-DD LR4, 100G QSFP DR1+, and 100G CWDM4 models (Compl. ¶18).

Functionality and Market Context

  • The accused products are pluggable optical modules designed for high-speed data communication, converting electrical data signals into optical signals for transmission over fiber optic cables, and vice versa (Compl. ¶16). These modules are used in high-growth markets such as internet data centers and telecommunications infrastructure (Compl. ¶16). The complaint provides detailed photographic evidence in Exhibits G through AA, which purport to show the internal components and construction of the accused products, identifying specific features alleged to map to the patent claims (Compl. ¶18, Exs. G-AA). For example, Exhibit G includes an annotated photograph of the Eoptolink 100G CWDM4 product, identifying the "dual fiber type direct link LC adapter" that is alleged to infringe the ’367 Patent (Compl., Ex. G, p. 120).

IV. Analysis of Infringement Allegations

’367 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A dual fiber type direct link LC adapter comprising: an adapter body portion defining first and second LC connector receiving regions at a pluggable connector end and defining first and second slots at a direct link end; The accused products allegedly contain a dual fiber type direct link LC adapter with an adapter body that defines LC connector receiving regions and first and second slots. ¶24; Ex. G, p. 124 col. 5:46-54
first and second direct link connector assemblies configured to be received in the first and second slots, respectively, each of the direct link connector assemblies defining an LC connector receptacle at one end... The accused products allegedly have first and second direct link connector assemblies located in the slots, which define an LC connector receptacle for optical coupling. ¶24; Ex. G, p. 124 col. 6:55-65
an adapter cover portion configured to cover the first and second slots for retaining the direct link connector assemblies in the respective slots. The accused products allegedly include an adapter cover portion that covers the slots to retain the connector assemblies. ¶24; Ex. G, p. 124 col. 6:50-53
  • Identified Points of Contention:
    • Scope Questions: A central issue may be the construction of the term "direct link." The patent defines this term as an optical coupling "without using pluggable connectors at the ends of the fiber link" (’367 Patent, col. 3:1-4). The dispute may turn on whether the internal connection between the connector assemblies and the optical fibers leading to the TOSA/ROSA in the accused product meets this definition. The complaint's visual evidence identifies internal "optical fiber" connecting to the "direct link connector assembly" (Compl., Ex. G, p. 123).
    • Technical Questions: The analysis may focus on the precise mechanical structure of the accused adapter. The question will be whether the combination of its "adapter body portion," "direct link connector assemblies," and "adapter cover portion," as identified in the complaint's exhibits, performs the functions in the same way as described and claimed in the patent.

’433 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A multi-channel receiver optical subassembly (ROSA) comprising: a ROSA housing; The accused products allegedly contain a multi-channel ROSA with a ROSA housing. ¶33; Ex. J, p. 143 col. 7:43-45
an optical demultiplexer located in the ROSA housing, the optical demultiplexer including multiple optical outputs corresponding to multiple channels... The accused ROSA allegedly includes an optical demultiplexer with multiple optical outputs corresponding to different signal channels. ¶33; Ex. J, p. 143 col. 8:14-24
an array of photodetectors located in the ROSA housing and spaced from the optical demultiplexer, the array of photodetectors aligned with and directly optically coupled to the multiple optical outputs... The accused ROSA allegedly has an array of photodetectors that are aligned with and directly optically coupled to the demultiplexer's outputs. The complaint includes a photograph purporting to show this direct coupling (Compl., Ex. J, p. 140). ¶33; Ex. J, p. 143 col. 8:25-30
  • Identified Points of Contention:
    • Scope Questions: The construction of "directly optically coupled" will be dispositive. The patent defines this term as "an optical coupling without any intermediate optical components such as lenses or fiber arrays" (’433 Patent, col. 3:12-15). The infringement analysis will question whether the interface between the demultiplexer and the photodetectors in the accused products meets this specific negative limitation.
    • Technical Questions: An evidentiary question will be the actual physical spacing and alignment between the demultiplexer and photodetectors in the accused products. The complaint alleges the components are spaced and aligned as required by the claim (Compl., Ex. J, p. 143), but this will be a point of factual dispute, potentially requiring expert analysis of the physical hardware to determine if the coupling efficiency and alignment tolerances described in the patent are met (’433 Patent, col. 8:47-57).

V. Key Claim Terms for Construction

  • Patent: U.S. Patent No. 9,448,367

    • The Term: "direct link"
    • Context and Importance: This term is central to the claimed invention, which distinguishes itself from prior art by using a "direct link adapter" to save space. The outcome of the infringement analysis depends on whether the accused device's internal connection architecture constitutes a "direct link."
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The abstract describes the adapter as being "directly linked to the multi-channel TOSA and the multi-channel ROSA with optical fibers," which could suggest that a dedicated fiber connection, as opposed to a pluggable one, is the key feature (’367 Patent, Abstract).
      • Evidence for a Narrower Interpretation: The specification provides an explicit definition: "'direct link' refers to optically coupling with a single optical fiber mechanically coupled between two components without using pluggable connectors at the ends of the fiber link" (’367 Patent, col. 3:1-4). This definition appears to be a deliberate limitation, which a defendant may argue narrowly defines the scope of the claim.

  • Patent: U.S. Patent No. 9,509,433

    • The Term: "directly optically coupled"
    • Context and Importance: This term captures the core technical contribution of the patent—achieving high-efficiency coupling in a compact ROSA without traditional intermediate optics. Whether the accused products infringe will depend almost entirely on the construction of this term.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: A party might argue that the term should be given its plain and ordinary meaning, suggesting any non-mediated light path from the demultiplexer output to the photodetector surface.
      • Evidence for a Narrower Interpretation: The specification provides an explicit definition: "The term 'directly optically coupled' refers to an optical coupling without any intermediate optical components such as lenses or fiber arrays" (’433 Patent, col. 3:12-15). The patent further emphasizes that the design avoids components like a "glass rail" used to couple to a fiber array, reinforcing a narrow interpretation that excludes any intervening optical element, however small (’433 Patent, col. 8:36-40).

VI. Other Allegations

  • Indirect Infringement: The complaint's specific counts for infringement for each patent allege direct infringement under 35 U.S.C. § 271(a) (Compl. ¶¶ 22, 31, 40, 49, 58, 67). No specific facts are alleged to support claims for induced or contributory infringement.
  • Willful Infringement: For each asserted patent, the complaint alleges that the Defendant has had "knowledge and notice" of the patent and its infringement "since the filing of the original complaint in this action" (Compl. ¶¶ 26, 35, 44, 53, 62, 71). These allegations appear to form the basis for a claim of willful infringement based on post-filing conduct rather than pre-suit knowledge.

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of definitional scope: can the term "direct link" ('367 Patent), which the patent defines as lacking pluggable connectors at its ends, be construed to read on the internal fiber connections within the accused transceivers? Similarly, will the term "directly optically coupled" ('433 Patent), defined as lacking "lenses or fiber arrays," be construed to cover the specific interface between the demultiplexer and photodetectors in the accused products?
  • A key evidentiary question will be one of technical equivalence and implementation: does the physical construction of the accused products, as depicted in the complaint's photographic exhibits, match the specific structural limitations of the claims? This will involve a detailed, fact-intensive comparison of the accused device's adapter mechanics, component spacing, and electrical circuit layouts against the descriptions and claims of the six asserted patents.