DCT

5:24-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 because Defendant has a regular and established place of business in the district, specifically a physical office in Fremont, California, and has allegedly committed acts of infringement within the district by designing, selling, and offering for sale the accused products.
  • Core Dispute: Plaintiff alleges that Defendant’s high-speed optical transceiver products infringe six patents related to the mechanical and electrical design, component arrangement, and assembly of such devices.
  • Technical Context: The technology concerns compact, high-performance optical transceivers, which are critical components for converting electrical data signals to optical signals for transmission over fiber optic networks in data centers, telecommunications, and cable television broadband infrastructure.
  • Key Procedural History: This First Amended Complaint follows an original complaint, the filing of which Plaintiff alleges established Defendant's knowledge of the asserted patents for purposes of post-filing infringement.

Case Timeline

Date Event
2012-12-10 ’367 Patent Priority Date
2013-05-14 ’433 Patent Priority Date
2016-09-20 ’367 Patent Issued
2016-11-29 ’433 Patent Issued
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 Issued
2020-01-08 ’887 Patent Priority Date
2020-03-03 ’818 Patent Issued
2020-07-14 ’890 Patent Issued
2021-11-16 ’887 Patent Issued
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 and receiver optical subassemblies (TOSA and ROSA) and their necessary optical connections into the small form factor required for modern transceiver modules used in passive optical networks (PONs) (Compl., Ex. A, ’367 Patent, col. 1:56-65).
  • The Patented Solution: The invention is a compact "dual fiber type direct link adapter" designed to solve this space constraint. This adapter provides a standard external interface for pluggable connectors (like LC connectors) while using a non-pluggable, direct fiber link internally to connect to the TOSA and ROSA. By eliminating the need for internal pluggable connectors, the design saves space within the transceiver housing (Compl., Ex. A, ’367 Patent, Abstract; col. 2:47-58).
  • Technical Importance: This design enables the construction of smaller and more densely packed multi-channel optical transceivers, a key factor in scaling the capacity of data centers and telecommunications infrastructure (Compl., Ex. A, ’367 Patent, col. 1:33-40).

Key Claims at a Glance

  • The complaint asserts independent claim 1 (Compl. ¶23).
  • Claim 1 of the ’367 Patent includes the following essential elements:
    • 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;
    • first and second direct link connector assemblies configured to be received in the slots, each defining an LC connector receptacle at one end that extends into a respective receiving region and is configured to be mechanically coupled to an optical fiber at another end; and
    • an adapter cover portion configured to cover the slots for retaining the direct link connector assemblies.
  • The complaint alleges infringement of "one or more claims," thereby reserving the right to assert dependent 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 efficient optical coupling between the multiple outputs of an optical demultiplexer and an array of photodetectors within a compact receiver optical subassembly (ROSA) housing. The use of intermediate components like fiber arrays or lenses to aid alignment consumes valuable space and can be costly (Compl., Ex. B, ’433 Patent, col. 2:1-9).
  • The Patented Solution: The invention proposes a ROSA design where the array of photodetectors is "directly optically coupled" to the demultiplexer outputs without intervening lenses or fiber arrays. The solution involves configuring the photodetectors and demultiplexer to avoid physical interference from elements like wire bonding pads, allowing for the close spacing (e.g., 10-40 microns) needed for efficient direct coupling (Compl., Ex. B, ’433 Patent, Abstract; col. 8:27-35, 54-58).
  • Technical Importance: This approach facilitates the creation of smaller, more sensitive, and more manufacturable multi-channel optical receivers, which is essential for high-density optical networking equipment (Compl., Ex. B, ’433 Patent, col. 1:56-65).

Key Claims at a Glance

  • The complaint asserts independent claims 1 and 13 (Compl. ¶32).
  • Claim 1 of the ’433 Patent includes the following essential elements:
    • A multi-channel receiver optical subassembly (ROSA) comprising:
    • a ROSA housing;
    • an optical demultiplexer located in the housing with multiple optical outputs; and
    • an array of photodetectors in the housing, spaced from the demultiplexer, and aligned with and directly optically coupled to the demultiplexer's outputs.
  • Claim 13 recites a multi-channel optical transceiver module that incorporates the ROSA of claim 1, along with a transceiver housing, a circuit board, and a transmitter optical subassembly (TOSA).
  • The complaint alleges infringement of "one or more claims," reserving the right to assert additional 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: The patent describes a multi-layer flexible printed circuit (FPC) that routes both high-frequency RF (data) signals and DC (power/control) signals on separate, isolated layers. This design aims to prevent electrical interference between the different signal types within the confined space of an optical transceiver, eliminating the need for multiple separate FPCs (Compl., Ex. C, ’470 Patent, Abstract).
  • Asserted Claims: Independent claims 1, 10, and 17 are asserted (Compl. ¶41).
  • Accused Features: The FPCs within the Eoptolink 100G QSFP LR4 transceivers are accused of infringement (Compl. ¶42).

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

  • Technology Synopsis: The patent discloses a mechanical fastening mechanism for pluggable optical transceivers. The mechanism features a movable fastening component with a linkage arm and extending arms that is pressed by an elastic component housed within a confined groove on the transceiver's outer surface, creating a latch to secure the transceiver in a cage (’818 Patent, Abstract).
  • Asserted Claims: Independent claims 1 and 10 are asserted (Compl. ¶50).
  • Accused Features: The mechanical latching and fastening components on various Eoptolink 100G and 400G transceivers are accused of infringement (Compl. ¶51).

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

  • Technology Synopsis: This invention addresses the challenge of placing monitor photodiodes (MPDs) in compact TOSAs without increasing the assembly's length or using long wire bonds that degrade signal quality. The solution involves mounting the MPD on a vertical surface (e.g., on a feedthrough device) above the laser diode, which frees up space to run shorter RF traces directly underneath the MPD to the laser diode (’890 Patent, Abstract).
  • Asserted Claims: Independent claim 1 is asserted (Compl. ¶59).
  • Accused Features: The TOSA component arrangement within Eoptolink's 100G QSFP LR4 transceivers is accused 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 that creates a recessed mounting surface for a TOSA module. This "countersinking" of the TOSA reduces the vertical distance to the substrate's electrical terminals, enabling the use of shorter wire bonds which improves high-speed signal integrity (’887 Patent, Abstract).
  • Asserted Claims: Independent claims 1 and 10 are asserted (Compl. ¶68).
  • Accused Features: The substrate design and TOSA mounting method in various Eoptolink 400G and 100G transceivers are accused of infringement (Compl. ¶69).

III. The Accused Instrumentality

Product Identification

  • The complaint identifies the "Accused Products" as a range of Eoptolink optical transceivers, including but not limited to the Eoptolink 400G QSFP-DD (LR4, FR4, DR4 models) and 100G QSFP (LR4, DR1+, CWDM4 models) (Compl. ¶18).

Functionality and Market Context

  • The Accused Products are pluggable modules that convert electrical data signals into optical signals for high-speed transmission over fiber optic cables. The complaint alleges these products are used in growing end-markets such as internet data centers and telecommunications (Compl. ¶16). Plaintiff alleges Defendant imports, uses, offers for sale, and sells these products in the United States (Compl. ¶18). Exhibit G, Figure 1 presents external and internal views of an accused transceiver, identifying components alleged to be the claimed adapter body and cover (Compl., Ex. G, p. 120). Exhibit J, Figure 3 provides a magnified view of an accused device's ROSA, illustrating the alleged direct optical coupling between an optical demultiplexer and an array of photodetectors (Compl., Ex. J, p. 140).

IV. Analysis of Infringement Allegations

U.S. Patent No. 9,448,367 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 include a dual fiber type direct link LC adapter with an adapter body. This body is alleged to define LC connector receiving regions on its external-facing end and slots on its internal-facing, direct link end. ¶24; Ex. G col. 5:48-54
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 ... and ... configured to be mechanically coupled to an optical fiber at another end; The accused adapter allegedly contains two direct link connector assemblies that sit in the slots. These assemblies are alleged to define an internal LC connector receptacle and connect to internal optical fibers that route to the TOSA and ROSA. ¶24; Ex. G col. 6:6-14
and 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 adapter allegedly includes a cover portion that covers the slots and retains the internal direct link connector assemblies. ¶24; Ex. G col. 6:1-3
  • Identified Points of Contention:
    • Scope Questions: A central question may be the scope of the term "direct link." The patent defines this as coupling "without using pluggable connectors at the ends of the fiber link" (Compl., Ex. A, ’367 Patent, col. 3:1-4). The dispute may focus on whether the specific internal connection structure of the accused products falls within this definition as construed in light of the patent's specification and figures.
    • Technical Questions: Claim 1 requires each internal "direct link connector assembly" to itself define an "LC connector receptacle." A key technical question will be whether the internal connection point of the accused device's adapter has a structure that meets the definition of an "LC connector receptacle," or if it is a different type of non-standard fiber interface.

U.S. Patent No. 9,509,433 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, which includes a ROSA housing. ¶33; Ex. J col. 6:23-28
an optical demultiplexer located in the ROSA housing, the optical demultiplexer including multiple optical outputs corresponding to multiple channels...; The ROSA allegedly contains an optical demultiplexer with multiple outputs to separate the different wavelengths of an incoming optical signal. ¶33; Ex. J col. 8:14-16
and 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, respectively, of the optical demultiplexer. An array of photodetectors is allegedly located in the ROSA and positioned to be "directly optically coupled" to the outputs of the demultiplexer, without intervening lenses or fiber arrays, to convert the separated optical signals back into electrical signals. ¶33; Ex. J col. 8:27-35
  • Identified Points of Contention:
    • Scope Questions: The primary point of contention will likely be the meaning of "directly optically coupled." The patent defines this as coupling "without any intermediate optical components such as lenses or fiber arrays" (Compl., Ex. B, ’433 Patent, col. 3:13-16). The key legal question is how broadly "intermediate optical components" is construed.
    • Technical Questions: An evidentiary question will be what, if anything, exists in the space between the demultiplexer output and the photodetector active area in the accused products. The analysis will require determining whether any material present (e.g., air, encapsulant, index-matching gel) qualifies as an "intermediate optical component" that would defeat the claim of direct coupling.

V. Key Claim Terms for Construction

The Term: "direct link" (’367 Patent)

  • Context and Importance: This term appears in the preamble of claim 1 and is fundamental to the patent's asserted novelty over prior art that may have used internal pluggable connectors. Its construction will determine the scope of the adapter structure covered by the patent.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent 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" (Compl., Ex. A, ’367 Patent, col. 3:1-4). This definition focuses on the absence of pluggable connectors, which may support a broader reading covering various non-pluggable internal connection types.
    • Evidence for a Narrower Interpretation: The specification describes the "direct link connector assemblies" in detail, including specific flanges and grooves that secure them within the adapter body (Compl., Ex. A, ’367 Patent, col. 6:4-10). A party could argue that "direct link" should be limited to the specific structural arrangements disclosed in the preferred embodiments.

The Term: "directly optically coupled" (’433 Patent)

  • Context and Importance: This is the core limitation of claim 1, distinguishing the invention from prior art ROSAs that used lenses or fiber arrays for alignment. The viability of the infringement claim hinges entirely on whether the accused products meet this limitation.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent defines the term as "an optical coupling without any intermediate optical components such as lenses or fiber arrays" (Compl., Ex. B, ’433 Patent, col. 3:13-16). This language explicitly excludes only two types of components, suggesting that the presence of other materials (like air or adhesive) in the light path does not negate a "direct" coupling.
    • Evidence for a Narrower Interpretation: The specification states that in an exemplary embodiment, "the light exits the waveguides of the AWG and enters the photodetectors 236 without passing through any medium other than air" (Compl., Ex. B, ’433 Patent, col. 8:36-39). This passage may be used to argue that the term requires an air gap and precludes the presence of any other medium, such as an index-matching gel or epoxy, in the optical path.

VI. Other Allegations

  • 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" (e.g., Compl. ¶26, ¶35, ¶44, ¶53, ¶62, ¶71). These allegations appear to form the basis for a claim of willful infringement based on conduct occurring after the lawsuit was initiated. The prayer for relief requests a finding that the case is "exceptional" under 35 U.S.C. § 285 (Compl., Prayer for Relief ¶T).

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

  • A core issue will be one of definitional scope: The case will likely turn on the construction of key phrases such as "direct link" (’367 Patent) and "directly optically coupled" (’433 Patent). The court's interpretation of whether these terms are limited to the specific embodiments shown in the patents or encompass any design that omits conventional pluggable connectors, lenses, or fiber arrays will be a central point of dispute.
  • A second key question will be one of structural correspondence: Across the portfolio of asserted patents, which claim specific mechanical and electrical configurations for improving density and performance (e.g., the vertical MPD mount of the ’890 Patent, the stepped substrate of the ’887 Patent), the central evidentiary question will be whether the accused Eoptolink products achieve similar results through fundamentally different designs or by practicing the specific structural solutions claimed by AOI.