NEC Corporation v. Neptune Subsea IP Limited

1. Case Identification

• Case #: IPR2018-01160
• Patent #: 8,406,637
• Filed: May 25, 2018
• Petitioner(s): NEC Corporation, Nokia Corporation, and Alcatel Submarine Networks
• Patent Owner(s): Xtera Communications, Inc.
• Challenged Claims: 1-7, 9-13

2. Patent Overview

• Title: AUTOMATIC PRE-EMPHASIS
• Brief Description: The ’637 patent is directed to controlling pre-emphasis applied to optical signals in a wavelength division multiplexed (WDM) optical communication system. The patent describes a distributed control architecture where a central rack control processor (RCP) sets a target bit-error-rate (BER) for individual transponders, which then manage their own output powers based on feedback from associated receivers.

3. Grounds for Unpatentability

Ground 1: Claims 1-7, 9-13 are obvious over Sakamoto in view of Hachiya, Mori, and Weiske.

• Prior Art Relied Upon: Sakamoto (Patent 6,934,479), Hachiya (Application # 2004/0042793), Mori (Application # 2004/0081421), and Weiske (Patent 7,020,092).
• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that the combination of references taught every element of the challenged claims. Sakamoto was asserted as the primary reference, disclosing a WDM optical communication system with a distributed control architecture similar to that claimed. Sakamoto’s system included a supervisory control section (the "control processor") that receives performance information (e.g., optical signal-to-noise ratio (OSNR), BER) from receivers and distributes it to local controllers within each optical transmitter. These local controllers then autonomously adjust pre-emphasis to meet a pre-set "target value."

    To supply missing elements, Petitioner combined Sakamoto with three secondary references:

    • Hachiya was argued to teach using a control processor to calculate a target quality metric (e.g., an average Q value) for pre-emphasis, addressing how Sakamoto’s "target value" could be determined. Hachiya also disclosed a dithering process—monitoring changes in a quality metric as power is increased and decreased—to determine if a channel is in a linear or non-linear operating region and adjust power accordingly. This was asserted to teach the dithering limitation added to claim 7 during prosecution.
    • Weiske was argued to teach a method for managing the dynamic range of transmitted signals to prevent overloading receivers. This was accomplished by calculating a compression factor based on the mean power and applying it equally to all transmitters in a band. Petitioner contended this compression factor is the claimed "centralization signal" used to maintain an average drive power, a limitation added to the independent claims during prosecution.
    • Mori was cited to explicitly teach using a "serial interface" for communication between a central controller and local controllers in a distributed WDM system. Petitioner argued that to the extent Sakamoto was silent on the specific interface, Mori demonstrated this was a well-known implementation detail.

  • Motivation to Combine: Petitioner asserted a person of ordinary skill in the art (POSITA) would combine the references for predictable results. A POSITA would have been motivated to implement Hachiya’s method for calculating a target value in Sakamoto’s system to provide a specific, known mechanism for a function Sakamoto left generic. Similarly, a POSITA would have incorporated Weiske’s dynamic range compression to solve the known problem of potential receiver overload in pre-emphasis systems like Sakamoto’s, thereby improving system reliability. The combination with Mori was presented as merely using a standard interface (serial) to implement the known communication pathways in Sakamoto’s distributed architecture.

  • Expectation of Success: Petitioner argued a POSITA would have had a reasonable expectation of success because all references are from the same technical field of WDM optical communications and address interrelated problems. The proposed combinations involved applying known solutions (from Hachiya, Weiske, Mori) to a known system type (Sakamoto) to achieve predictable improvements in performance and reliability.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §325(d) would be inappropriate. Although the Hachiya reference was considered during prosecution, it was applied only as an anticipatory reference against different claims. Petitioner asserted that the current petition presented Hachiya in a new light, as part of an obviousness combination with three other references (Sakamoto, Mori, Weiske) that were never considered by the Examiner. The petition, therefore, raised a new combination and new arguments, warranting consideration by the Board.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-7 and 9-13 of the ’637 patent as unpatentable.