PTAB

IPR2018-01157

NEC Corp v. Neptune Subsea IP Ltd

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1. Case Identification

2. Patent Overview

  • Title: Phase Shift Keyed High Speed Signalling
  • Brief Description: The ’798 patent relates to fiber optic transmission systems for high-speed data signaling (e.g., 20 Gb/s per channel) in a wavelength-division multiplexing (WDM) environment. The technology employs pre-compensation of chromatic dispersion to ensure that most channels achieve a minimum absolute accumulated dispersion near the midpoint of the optical fiber link.

3. Grounds for Unpatentability

Ground 1: Claims 13-20 are obvious over Yamamoto in view of Nishimoto

  • Prior Art Relied Upon: Yamamoto (Patent 6,021,235) and Nishimoto (Patent 6,871,024).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Yamamoto disclosed the foundational WDM optical transmission system recited in claim 13. Yamamoto taught a system with a transmitter, receiver, and optical link that used adjustable dispersion compensation fibers (DCOFs) for pre-compensation. This pre-compensation was adjusted to achieve reduced or minimum accumulated dispersion within a central distance of the optical fiber link. However, Yamamoto’s adjustment mechanism was not explicitly feedback-controlled. Nishimoto was argued to supply this missing element, as it taught an automatic dispersion compensation system that used a closed feedback loop. This loop measured the bit error rate (BER) at the receiver and sent control signals back to a variable dispersion compensator at the transmitter to optimize the signal and reduce bit errors.
    • Motivation to Combine: Petitioner contended a person of ordinary skill in the art (POSITA) would combine these references to improve the system in Yamamoto. A POSITA would have been motivated to incorporate Nishimoto’s BER-based feedback control to automate the adjustment of Yamamoto’s pre-compensation, thereby creating an improved WDM system capable of automatic compensation for waveform degradation. This combination would achieve the claimed "tunable pre-compensation mechanism" that is adjusted using a closed control loop until an acceptable BER is reached, resulting in a more robust system with reduced size and cost. The dependent claims (14-20), which recite specific percentage ranges for the central region of minimum dispersion, were argued to be disclosed by the dispersion maps in Yamamoto.

Ground 2: Claims 13-20 are obvious over Chowdhury in view of Webb, and Tanaka162

  • Prior Art Relied Upon: Chowdhury (Application # 2004/0234272), Webb (UK Patent Application Publication GB 2 423 900), and Tanaka162 (Application # 2002/0012162).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground presented two primary combinations. For claim 13, Petitioner argued that Chowdhury in view of Webb rendered the claim obvious. Chowdhury taught a long-haul optical communication system using pre-transmission dispersion compensation (CPRE) to create a symmetrical dispersion map. This symmetry was designed to suppress nonlinear signal distortions by ensuring minimum accumulated dispersion occurred at the approximate midpoint of the fiber link. Webb was asserted to provide the claimed closed-loop control functionality. Webb disclosed a robust method for estimating BER at the receiver and using that data in a feedback loop to control transmitter parameters, explicitly including an "adjustable dispersion element" for pre-dispersion. For dependent claims 14-20, Tanaka162 was added to the combination. Petitioner argued that to the extent Chowdhury lacked express scale information for the claimed numerical ranges of the central region, Tanaka162 provided a concrete example of a long-haul system with a dispersion map over 10,000 km from which the claimed percentage ranges (e.g., 30-70%) could be directly derived.
    • Motivation to Combine: A POSITA seeking to implement Chowdhury's system would be focused on improving the BER at the receiver. Petitioner argued it would have been obvious to look to a reference like Webb, which provided rich detail on a closed control loop specifically designed to optimize BER by adjusting transmitter-side parameters like pre-dispersion. Combining Webb’s robust feedback control with Chowdhury’s dispersion mapping would fully realize a dynamic, optimized system. Furthermore, a POSITA would consult a reference like Tanaka162 for established design parameters and scale information, making the selection of the claimed numerical ranges an obvious matter of design choice rather than invention.

4. Key Claim Construction Positions

  • "pre-compensation mechanism" (Claim 13): Petitioner argued this term should be given its plain and ordinary meaning. However, they noted that to the extent the Patent Owner might argue the term invokes 35 U.S.C. § 112, ¶6 (means-plus-function), the petition’s element-by-element analysis mapped the prior art to the specific structures and algorithms disclosed in the ’798 patent’s specification. Therefore, Petitioner contended the claims were unpatentable regardless of whether the term was treated as a means-plus-function limitation.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under § 325(d) would be inappropriate. They asserted that each of the grounds advanced in the petition was based in significant measure on new prior art and arguments that were not before the Examiner during the original prosecution of the ’798 patent.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 13-20 of the ’798 patent as unpatentable under 35 U.S.C. §103.