US 9448367

US Patent 9448367, titled "Multi-channel optical transceiver module including dual fiber type direct link adapter for optically coupling optical subassemblies in the transceiver module," was issued to Applied Optoelectronics Inc. on September 20, 2016. The inventors are I-Lung Ho, Stefan J. Murry, and Che-Shou (Richard) YEH. The application for this patent was filed on October 15, 2015, under application number US14/883,970.

Abstract:
The patent describes a multi-channel optical transceiver that includes a multi-channel transmitter optical subassembly (TOSA), a multi-channel receiver optical subassembly (ROSA), and a dual fiber type direct link adapter. This adapter is directly connected to the TOSA and ROSA using optical fibers and is also designed to accept pluggable optical connectors, such as LC connectors, from external fiber-optic cables. The adapter thus serves as the optical input and output for the transceiver. This multi-channel optical transceiver can be utilized in wavelength division multiplexed (WDM) optical systems, for instance, in an optical line terminal (OLT) within a WDM passive optical network (PON).

Independent Claims Overview:

• Independent Claim 1: This claim describes a dual fiber type direct link LC adapter. It features an adapter body with two LC connector receiving areas at one end (the pluggable connector end) and two slots at the other end (the direct link end). The adapter includes two direct link connector assemblies, each designed to fit into one of these slots. Each assembly has an LC connector receptacle that extends into one of the LC connector receiving areas to allow optical coupling with an external LC connector. The other end of each direct link connector assembly is configured for mechanical coupling to an optical fiber. An adapter cover portion is provided to secure these direct link connector assemblies within their respective slots.

Legal Status and Dockets:
US Patent 9448367 is currently active. Litigation records associated with this patent indicate that a PTAB case, IPR2026-00019, was filed (and not instituted for procedural reasons). Additionally, multiple US cases related to this patent have been filed in the California Northern District Court, specifically 5:24-cv-08165, 4:24-cv-09041, 3:24-cv-09041, and 3:24-cv-08165. As of the current date (April 26, 2026), no specific dockets for US Patent 9448367 were found in the CAFC 2026 dockets via direct search.

Known litigation involving US patent 9448367 as of April 26, 2026, is detailed below:

1. Inter Partes Review (IPR) Proceeding

• Plaintiff(s) (Petitioner): Eoptolink Technology USA Inc.
• Defendant(s) (Patent Owner): Applied Optoelectronics, Inc. ("AOI")
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Case Number: IPR2026-00019
• Filing Date: October 10, 2025
• Outcome or Current Status: Not Instituted - Procedural. The PTAB decided not to initiate a full inter partes review.

2. US District Court Case

• Plaintiff(s): Applied Optoelectronics, Inc. ("AOI")
• Defendant(s): Eoptolink Technology USA Inc. ("Eoptolink")
• Jurisdiction: United States District Court, Northern District of California, San Jose Division
• Case Number: 5:24-cv-08165-NW
• Filing Date: The case number indicates a 2024 filing year. The exact filing date is not explicitly provided in the available snippets, but document 46 was filed on January 13, 2026.
• Outcome or Current Status: The case is currently stayed. A joint administrative motion to stay pending IPR institution decisions (including IPR2026-00019 concerning US9448367B2) was filed by both parties and granted by the court. US patent 9448367B2 is one of six patents asserted by AOI against Eoptolink in this action.

Proceedings overview

There is one AIA trial proceeding on US patent 9448367, which resulted in a discretionary denial. This outcome means the patent claims were not reviewed on the merits and remain in their original form, providing less certainty for a defendant.

IPR2026-00019 — Accelight Technologies, Inc. et al. v. I-Lung HO et al

• Type: Inter Partes Review
• Filed: 2025-10-10
• Status: Discretionary Denial
• Judge panel: Not publicly available yet for this procedural stage.
• Petition grounds: Not publicly available in the provided information.
• Institution decision: Denied (Discretionary Denial) — 2026-03-06. The PTAB exercised its discretion to deny institution of the IPR. The specific reasoning for the discretionary denial is not provided in the prompt but typically relates to factors such as parallel district court litigation, settlement negotiations, or other considerations under 35 U.S.C. § 314(a).
• Final Written Decision: Not issued, as institution was denied.
• Settlement / termination: Not applicable, as institution was denied.
• Appeal: No Federal Circuit appeal on an institution denial is indicated in the provided information.
• Defensive value: The patent owner prevailed at the institution stage, meaning all claims challenged in this IPR remain presumptively valid. An IPR-based defense on the same grounds may be more challenging in the future, as the PTAB has already exercised its discretion against review.

Strategic summary

All claims of US9448367 are currently SUSTAINED, as the single IPR filed against it was denied institution. There have been no claims invalidated or narrowed through PTAB proceedings.

Regarding the estoppel landscape, since institution was denied in IPR2026-00019, the petitioner (Accelight Technologies, Inc. et al.) and its privies may be estopped under 35 U.S.C. § 315(e)(2) from asserting in future district court or ITC proceedings any ground that was raised or reasonably could have been raised in the petition. However, without the specifics of the petition grounds, it is difficult to determine precisely which prior-art grounds are still available to a potential defendant.

There is no discernible pattern of multiple IPRs filed by the same petitioner, nor aggressive PTAB appeals by the patent owner based on the single proceeding. Unified Patents is not indicated as being in the chain for this proceeding.

Recommended next steps

Since IPR2026-00019 resulted in a discretionary denial, all claims of US9448367 remain in force. A defendant facing assertion of this patent should be aware that the PTAB has opted not to review the claims on the merits in the single challenge filed to date. The decision for the discretionary denial of IPR2026-00019 was issued on 2026-03-06. More details on the PTAB's reasoning would be available in the institution decision, which can be found on the USPTO PTAB Decisions portal (https://ptab.uspto.gov/#/search/decisions).

Inventors

• I-Lung Ho (Applied Optoelectronics Inc.)
• Stefan J. Murry (Applied Optoelectronics Inc.)
• Che-Shou (Richard) YEH (Applied Optoelectronics Inc.)

Original assignee

Applied Optoelectronics Inc. is the original assignee. They ship products embodying the claims, specifically multi-channel optical transceivers and components for fiber-optic communication. Their primary line of business is the design, manufacture, and marketing of fiber-optic access network products, including optical components, modules, and equipment. Applied Optoelectronics Inc. is currently an operating company.

Assignment timeline

The USPTO Assignment Center (https://assignmentcenter.uspto.gov/) and Google Patents legal events provide the following assignment record for US Patent 9448367:

• 2017-09-28 (executed) / recorded 2017-09-29 — Reel 044061/0812

  • Conveyance: Security Interest
  • Assignor: APPLIED OPTOELECTRONICS, INC.
  • Assignee: BRANCH BANKING AND TRUST COMPANY, TEXAS
  • Correspondent: R. Andrew Patty II, Fulbright & Jaworski LLP, 98 San Jacinto Blvd., Suite 1100, Austin, TX 78701. This correspondent may recur in securitization contexts.
  • Context: Securitization (patent used as collateral for a loan)

• 2022-11-16 (executed) / recorded 2022-11-16 — Reel 061952/0344

  • Conveyance: Release by Secured Party
  • Assignor: TRUIST BANK (FORMERLY KNOWN AS BRANCH BANKING AND TRUST COMPANY)
  • Assignee: APPLIED OPTOELECTRONICS, INC.
  • Correspondent: R. Andrew Patty II, Norton Rose Fulbright US LLP, 98 San Jacinto Blvd., Suite 1100, Austin, TX 78701. This correspondent is a repeat player in this chain.
  • Context: Release of security interest (loan repaid or restructured)

• 2022-11-16 (executed) / recorded 2022-11-28 — Reel 062003/0523

  • Conveyance: Patent Security Agreement
  • Assignor: APPLIED OPTOELECTRONICS, INC.
  • Assignee: CIT NORTHBRIDGE CREDIT LLC, NEW YORK
  • Correspondent: David C. Miller, Blank Rome LLP, One Logan Square, 130 N. 18th Street, Philadelphia, PA 19103.
  • Context: Securitization (new patent used as collateral for a loan)

• 2023-11-17 (executed) / recorded 2023-11-20 — Reel 065630/0906

  • Conveyance: Termination and Release of Security Interest in Patents
  • Assignor: CIT NORTHBRIDGE CREDIT LLC
  • Assignee: APPLIED OPTOELECTRONICS, INC.
  • Correspondent: David C. Miller, Blank Rome LLP, One Logan Square, 130 N. 18th Street, Philadelphia, PA 19103. This correspondent is a repeat player in this chain.
  • Context: Release of security interest (loan repaid or restructured)

• 2012-12-05 to 2012-12-10 (signing dates) / recorded 2024-11-12 — Reel 069236/0614

  • Conveyance: Assignment of Assignors Interest
  • Assignor: MURRY, STEFAN J.; YEH, RICHARD; HO, I-LUNG (Inventors)
  • Assignee: APPLIED OPTOELECTRONICS, INC.
  • Correspondent: R. Andrew Patty II, Norton Rose Fulbright US LLP, 98 San Jacinto Blvd., Suite 1100, Austin, TX 78701. This correspondent is a repeat player in this chain.
  • Context: Formal recordation of original assignment from inventors to the initial assignee. This is often done later, sometimes in response to a diligence request or litigation.

• 2025-07-31 (executed) / recorded 2025-08-01 — Reel 072338/0695

  • Conveyance: Security Interest
  • Assignor: APPLIED OPTOELECTRONICS, INC.
  • Assignee: BOKF, NA D/B/A BOK FINANCIAL, COLORADO
  • Correspondent: Jeffrey M. Smith, Baker, Donelson, Bearman, Caldwell & Berkowitz, PC, 165 Madison Avenue, Suite 2000, Memphis, TN 38103.
  • Context: Securitization (new patent used as collateral for a loan)

Timeline diagram

timeline
    title Ownership of US 9448367
    2015 : Filed by Applied Optoelectronics Inc
    2016 : Issued
    2017 : Security interest to Branch Banking
    2022 : Release by Truist Bank
         : Security interest to CIT Northbridge
    2023 : Release by CIT Northbridge
    2024 : Inventors assign to Applied Opto
    2025 : Security interest to BOKF

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The assignees are financial institutions involved in securitization or the original operating company, Applied Optoelectronics Inc.
2. Known asserter in the chain — not present. None of the named assignees appear on public NPE lists.
3. Repeat correspondent across the chain — present. R. Andrew Patty II of Fulbright & Jaworski LLP (later Norton Rose Fulbright US LLP) appears as correspondent for the 2017-09-29 security interest and the 2022-11-16 release, and again for the 2024-11-12 inventor assignment. David C. Miller of Blank Rome LLP also appears for both the 2022-11-28 security agreement and the 2023-11-20 release.
4. Cascading transfers — not present. The transfers primarily relate to security interests and their releases, not consecutive ownership changes.
5. Pre-litigation transfer — unclear. While litigation has been filed (5:24-cv-08165, 4:24-cv-09041, 3:24-cv-09041, and 3:24-cv-08165), the specific filing dates of these suits are not precisely aligned with the transfers in a way that clearly indicates pre-litigation transfer for assertion purposes. The 2024-11-12 inventor assignment, although recorded late, relates to the initial ownership.
6. Bankruptcy fire-sale — not present. Applied Optoelectronics Inc. is an active operating company.
7. Privateering — not present. No evidence suggests a transfer to an NPE asserting on behalf of Applied Optoelectronics Inc.
8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at a defensive aggregator.

Verdict

Operating-company assertion
The assignment timeline clearly shows Applied Optoelectronics Inc. as the consistent owner, with intervening security interests from various financial institutions that were subsequently released. The late recording of the inventor assignment to Applied Optoelectronics Inc. in 2024 is a common practice and reinforces their original ownership. The company actively designs, manufactures, and sells products embodying the claims, indicating an operating company actively protecting its intellectual property.

Verification link: https://assignmentcenter.uspto.gov/

To identify the most relevant prior art for US Patent 9448367, I will examine the "Citations" section of the patent on Google Patents, which lists documents cited by the examiner and/or third parties. The USPTO's Patent Public Search tool is a robust resource for patent searching and identifying prior art.

Here is an analysis of the patent citations for US Patent 9448367:

Prior Art Cited by US9448367B2:

1. US5363460A

   • Full Citation: US5363460A (Diamond Sa)
   • Publication Date: 1994-11-08
   • Filing Date: 1992-11-26
   • Brief Description: This patent describes a sleeve portion for an optical fiber plug connector.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Potentially relevant to elements of Claim 2, which mentions a "sleeve around the fiber ferrule for defining at least a portion of the LC connector receptacle." The concept of a sleeve in an optical connector could be anticipated.

2. US5909526A

   • Full Citation: US5909526A (Molex Incorporated)
   • Publication Date: 1999-06-01
   • Filing Date: 1998-04-08
   • Brief Description: This patent describes a fiber optic connector assembly.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: This could broadly anticipate aspects of Claim 1 related to direct link connector assemblies and their mechanical coupling to optical fibers, and Claim 4 which describes an outer housing for the fiber ferrule and sleeve, as it deals with fiber optic connector assemblies in general.

3. US6247849B1

   • Full Citation: US6247849B1 (Alliance Fiber Optics Products, Inc.)
   • Publication Date: 2001-06-19
   • Filing Date: 1997-09-13
   • Brief Description: This patent describes a protection cap for a fiber coupler.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Less directly relevant to the core elements of US9448367's claims, which focus on the adapter's internal structure and direct link, rather than protective caps. However, the general field of fiber couplers is related.

4. US20020090177A1

   • Full Citation: US20020090177A1 (Anderson Jerry Max)
   • Publication Date: 2002-07-11
   • Filing Date: 2001-01-10
   • Brief Description: This patent application describes a duplex optical connector.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Given that Claim 1 of US9448367 describes a "dual fiber type direct link LC adapter," a prior art duplex optical connector could potentially anticipate the concept of coupling two fibers, though not necessarily with the "direct link" and specific LC adapter features.

5. US7029322B2

   • Full Citation: US7029322B2 (Molex Incorporated)
   • Publication Date: 2006-04-18
   • Filing Date: 2003-02-27
   • Brief Description: This patent describes a connector panel mount system.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Could be relevant to the mechanical mounting of the adapter, specifically Claim 1's "adapter body portion" and its integration within a larger system, though the specific "direct link" aspect might differ.

6. US20060204200A1

   • Full Citation: US20060204200A1 (Yazaki Corporation)
   • Publication Date: 2006-09-14
   • Filing Date: 2005-03-10
   • Brief Description: This patent application describes a dust shutter for an optical adapter.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Not directly anticipating the structural elements of Claim 1, 2, 3, or 4 of US9448367, as it focuses on an accessory (dust shutter) rather than the core adapter functionality.

7. US20060215970A1

   • Full Citation: US20060215970A1 (Toshio Mizue)
   • Publication Date: 2006-09-28
   • Filing Date: 2005-03-15
   • Brief Description: This patent application describes an optical transceiver with optical subassemblies optionally fixed to housing.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Highly relevant to the overall multi-channel transceiver module described in the summary and general description of US9448367, especially regarding TOSA/ROSA within a housing. However, it may not detail the specific "dual fiber type direct link adapter" of Claim 1.

8. US20090074359A1

   • Full Citation: US20090074359A1 (Case Richard L)
   • Publication Date: 2009-03-19
   • Filing Date: 2007-09-19
   • Brief Description: This patent application describes a shuttered adapter.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Similar to US20060204200A1, this focuses on a shutter mechanism for an adapter, which is not a defining feature of the independent claims of US9448367.

9. US20090226141A1

   • Full Citation: US20090226141A1 (Protai Photonic Co. Ltd.)
   • Publication Date: 2009-09-10
   • Filing Date: 2009-01-21
   • Brief Description: This patent application describes an optical fiber adapter with shutter member.
   • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Another reference focusing on shutter mechanisms, not directly anticipating the unique "direct link" or structural features of US9448367's adapter.

10. US20110038581A1

    • Full Citation: US20110038581A1 (Ronald Mudd)
    • Publication Date: 2011-02-17
    • Filing Date: 2009-08-13
    • Brief Description: This patent application describes a shutter for a fiber optic component and a fiber optic component including the shutter.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Yet another shutter-related patent application, not directly addressing the specific adapter structure of US9448367.

11. US20110103797A1

    • Full Citation: US20110103797A1 (Sumitomo Electric Industries, Ltd.)
    • Publication Date: 2011-05-05
    • Filing Date: 2009-10-29
    • Brief Description: This patent application describes a pluggable optical transceiver and method for manufacturing the same.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Highly relevant to the broader context of pluggable optical transceivers, similar to US20060215970A1. It might anticipate the general concept of a pluggable optical connector interface for a transceiver, but the specific "dual fiber type direct link adapter" with its internal direct fiber connection as claimed in US9448367 might be distinguishable.

12. US20110217008A1

    • Full Citation: US20110217008A1 (Corning Cable Systems Llc)
    • Publication Date: 2011-09-08
    • Filing Date: 2008-09-29
    • Brief Description: This patent application describes a fiber optic connector assembly employing fiber movement support and method of assembly.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Could potentially anticipate aspects of how optical fibers are secured within the direct link connector assemblies, relevant to the "mechanically coupled to an optical fiber at another end" clause in Claim 1.

13. US20120275784A1

    • Full Citation: US20120275784A1 (Soto Alexander I)
    • Publication Date: 2012-11-01
    • Filing Date: 2003-06-10
    • Brief Description: This patent application describes a system and method for optical layer management in optical modules and remote control of optical modules.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Less directly relevant, as it pertains to optical layer management and control, rather than the physical structure of the optical adapter described in Claim 1 of US9448367.

14. US20130156418A1

    • Full Citation: US20130156418A1 (Finisar Corporation)
    • Publication Date: 2013-06-20
    • Filing Date: 2011-12-14
    • Brief Description: This patent application describes a chip on flex optical subassembly.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Related to optical subassemblies (TOSA/ROSA) in general, which are components within the transceiver module of US9448367, but it does not appear to directly anticipate the "dual fiber type direct link LC adapter" of Claim 1.

15. US20130195405A1

    • Full Citation: US20130195405A1 (Panduit Corp.)
    • Publication Date: 2013-08-01
    • Filing Date: 2011-11-10
    • Brief Description: This patent application describes a shuttered LC Adapter.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: This is highly relevant as it describes a shuttered LC adapter. While US9448367 does not explicitly claim a shutter, the core "LC adapter" functionality and structure might be anticipated, particularly the "LC connector receiving regions" and the interaction with an LC connector.

16. US20140147082A1

    • Full Citation: US20140147082A1 (Alliance Fiber Optic Products, Inc.)
    • Publication Date: 2014-05-29
    • Filing Date: 2012-11-23
    • Brief Description: This patent application describes a mono-block type optical fiber adapter.
    • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Highly relevant to the overall adapter design. A "mono-block type optical fiber adapter" could anticipate the general structure of the adapter body portion and the integration of connector receiving regions, as described in Claim 1 of US9448367, though the "direct link" aspects may differ.

Key Observations on Prior Art Relevance:

• Several cited prior art documents focus on general fiber optic connectors, duplex connectors, and pluggable optical transceivers (e.g., US5909526A, US20020090177A1, US20060215970A1, US20110103797A1). These broadly establish the state of the art for optical connections and transceiver packaging.
• A notable number of citations relate to shutter mechanisms for optical adapters (e.g., US20060204200A1, US20090074359A1, US20090226141A1, US20110038581A1, US20130195405A1). While a shuttered LC adapter (US20130195405A1) is specifically relevant to the LC connector interface, the absence of a shutter in the independent claims of US9448367 could be a distinguishing feature.
• The most relevant prior art directly addressing adapter structures and LC connectors appear to be US20130195405A1 (shuttered LC adapter) and US20140147082A1 (mono-block type optical fiber adapter). These documents could potentially anticipate elements of Claim 1, particularly concerning the adapter body, LC connector receiving regions, and the general concept of an optical fiber adapter.
• The distinctive element of US9448367, as highlighted in Claim 1 and the patent summary, is the "dual fiber type direct link LC adapter" that provides a direct link between the adapter and the TOSA/ROSA via optical fibers, rather than relying solely on pluggable connections within the transceiver module. The specific combination of "first and second slots at a direct link end" and "first and second direct link connector assemblies" with their internal fiber ferrules and sleeves, coupled directly to the TOSA and ROSA, would need to be carefully compared against these prior art references to determine novelty.

To analyze the obviousness of US patent 9448367 under 35 U.S.C. § 103, we will consider combinations of prior art references that would make the claims, particularly independent Claim 1, obvious to a person having ordinary skill in the art (PHOSITA). The primary problem addressed by US9448367 is the challenge of accommodating multi-channel Transmitter Optical Subassemblies (TOSA) and Receiver Optical Subassemblies (ROSA) within the limited space of Optical Line Terminal (OLT) transceiver modules, where conventional LC adapters may not fit. The patent proposes a "dual fiber type direct link adapter" that uses optical fibers directly coupled to the TOSA and ROSA, thereby reducing the adapter's size and enabling a smaller transceiver module.

Independent Claim 1 of US9448367 describes:
"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 first and second slots, respectively, each of the direct link connector assemblies defining an LC connector receptacle at one end, wherein the LC connector receptacle extends into a respective one of the LC connector receiving regions and is configured to receive a portion of an LC connector for optical coupling, and wherein each of the direct link connector assemblies is configured to be mechanically coupled to an optical fiber at another end; 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 term "direct link" is defined in US9448367 as "optically coupling with a single optical fiber mechanically coupled between two components without using pluggable connectors at the ends of the fiber link" (US9448367, Detailed Description).

We will combine prior art references to demonstrate how the elements of Claim 1 would have been obvious.

Obviousness Combination

A PHOSITA, seeking to overcome the space constraints in OLT transceiver modules as articulated in the background of US9448367 (US9448367, Background Information), would be motivated to combine the teachings of existing optical transceiver designs and internal fiber coupling mechanisms.

Combination: US7090509B1 (Stratos) + US20110103797A1 (Sumitomo)

1. Primary Reference: US7090509B1 to Stratos International, Inc. ("Multi-port pluggable transceiver (MPPT) with multiple LC duplex optical receptacles")

US7090509B1 describes a "multi-port pluggable transceiver (MPPT) with multiple LC duplex optical receptacles". This reference establishes the concept of a transceiver module having an adapter body portion that defines multiple LC connector receiving regions at a pluggable connector end. Such receptacles are designed to receive external LC connectors for optical communication.

2. Supporting Reference: US20110103797A1 to Sumitomo Electric Industries, Ltd. ("Pluggable optical transceiver and method for manufacturing the same")

US20110103797A1 describes a pluggable optical transceiver that includes an internal optical connection structure. Specifically, it teaches a "ferrule on which a tip end of the optical waveguide is fixed, and a sleeve which is adapted to accept another ferrule of another optical connector to be optically connected to the ferrule via the sleeve are disposed in the connector receptacle". This directly teaches a "direct link connector assembly" in which an optical fiber is mechanically coupled to a ferrule at one end, and that ferrule (within a sleeve) forms a receptacle for an external LC connector.

Motivation for Combination and Remaining Elements:

The background of US9448367 explicitly states the challenge of integrating multi-channel TOSAs and ROSAs into small form factor OLT transceiver modules because conventional LC adapters consume too much space (US9448367, Background Information). A PHOSITA, faced with this known problem of miniaturization, would be motivated to combine the multi-port LC receptacle capability of a transceiver (as shown in US7090509B1) with the compact, internal fixed-fiber ferrule arrangement (as shown in US20110103797A1). The goal would be to create a more compact optical interface.

By combining these references:

• "an adapter body portion defining first and second LC connector receiving regions at a pluggable connector end": US7090509B1 clearly provides a multi-port transceiver with multiple LC duplex optical receptacles, which inherently defines such receiving regions.
• "defining first and second slots at a direct link end": When designing a compact module to house internal, fixed-fiber connector assemblies (as per US20110103797A1's teaching of an optical fiber mechanically fixed to a ferrule), a PHOSITA would find it obvious to design the adapter body with "slots" for receiving and aligning these components. This is a common mechanical design practice for modular assembly and space optimization.
• "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, wherein the LC connector receptacle extends into a respective one of the LC connector receiving regions and is configured to receive a portion of an LC connector for optical coupling, and wherein each of the direct link connector assemblies is configured to be mechanically coupled to an optical fiber at another end": US20110103797A1 precisely describes such an assembly where an optical fiber is mechanically fixed to a ferrule, and that ferrule/sleeve combination forms a receptacle for an external LC connector. It would be obvious to a PHOSITA to replicate this structure for a dual-fiber (first and second) configuration to support the duplex nature of the LC interface provided by US7090509B1.
• "an adapter cover portion configured to cover the first and second slots for retaining the direct link connector assemblies in the respective slots": Securing internal components within a housing is a routine engineering task. The use of an adapter cover to retain assemblies within slots is a common and predictable mechanical solution for ensuring robust optical and mechanical integrity in a compact device.

Conclusion:

The combination of US7090509B1 and US20110103797A1, driven by the well-known need to miniaturize optical transceiver modules for high-density applications as highlighted in the background of US9448367, would render the subject matter of Claim 1 of US9448367 obvious to a person having ordinary skill in the art. The specific mechanical arrangements for slots, retention, and dimensions claimed in the dependent claims are routine engineering optimizations that would naturally flow from this combination in pursuit of a compact design.