PTAB

IPR2016-01618

Fujitsu Network Communications Inc v. Core Optical Technologies LLC

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1. Case Identification

2. Patent Overview

  • Title: Cross Polarization Interface Canceler
  • Brief Description: The ’211 patent relates to coherent optical communication systems that use a cross-polarization interference canceller (XPIC) to mitigate or eliminate cross-polarization interference that occurs when optical signals are transmitted over an optical fiber.

3. Grounds for Unpatentability

Ground 1: Obviousness over Cusani - Claims 15-18, 23, 25, 30, 32-33, 35, and 37 are obvious over Cusani.

  • Prior Art Relied Upon: Cusani ("An Efficient Multilevel Coherent Optical System: M-4Q-QAM," Journal of Lightwave Technology, June 1992).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Cusani, a single prior art reference, taught all elements of the challenged claims. Cusani described a coherent optical system where the receiver’s baseband section compensates for fiber-induced polarization fluctuations. This compensation was achieved by multiplying a received signal vector by an inverse Jones matrix (J-1), a process Petitioner contended was functionally equivalent to the claimed XPIC. Cusani’s receiver was shown to include necessary components like a polarization beam splitter (PBS) to separate the optical signal, optical receivers to convert optical signals to electrical signals, and demodulators (an electrical phase-locked loop or PLL) to process the signals before cancellation. Petitioner asserted that this baseband processor, which applies the inverse Jones matrix to undo the effects of "coupling between polarization modes," inherently met the limitations of the claimed XPIC.
    • Motivation to Combine (for §103 grounds): As a single-reference ground, the argument was that all claimed elements were present in Cusani. Petitioner contended that to the extent any element was not explicitly disclosed, it would have been obvious for a person of ordinary skill in the art (POSITA) to implement it in Cusani's system, as XPICs and their constituent components were well-known for canceling crosstalk.

Ground 2: Obviousness over Cusani in view of Chikama - Claims 16-18 are obvious over Cusani in view of Chikama.

  • Prior Art Relied Upon: Cusani and Chikama ("Modulation and Demodulation Techniques in Optical Heterodyne PSK Transmission Systems," Journal of Lightwave Technology, March 1990).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground specifically addressed dependent claims 16-18, which require the receivers to be "double balanced optical receivers" (DBORs). While Cusani disclosed balanced optical hybrids and photodiodes that function as optical receivers, Chikama was cited for its explicit teaching of a dual-balanced polarization-diversity receiver that used DBORs. Petitioner argued that adding Chikama's DBORs to Cusani's system would satisfy the limitations of claims 16-18.
    • Motivation to Combine (for §103 grounds): A POSITA would combine Cusani and Chikama because both references were in the same field of coherent optical systems and addressed similar problems. Chikama expressly taught that DBORs were "promising as a highly sensitive coherent receiver" with several known merits, including effective use of local laser power and suppression of noise. Petitioner argued it would have been an obvious design choice to incorporate the known, superior DBORs from Chikama into Cusani's receiver architecture to achieve these predictable benefits.
    • Expectation of Success (for §103 grounds): A POSITA would have had a high expectation of success because it involved implementing a well-understood component (DBOR) with known advantages into a conventional optical receiver system to improve performance.

  • Additional Grounds: Petitioner asserted additional obviousness challenges based on Cusani in view of other references to meet specific dependent claim limitations. These included:

    • Cusani in view of Foschini (Patent 4,631,734): Argued that Foschini taught using complex matrix coefficients for amplitude and phase shifting in an XPIC, rendering claim 33 obvious.
    • Cusani in view of Kavehrad (a 1984 technical journal): Argued that Kavehrad taught a minimum mean-square error (MMSE) based canceler, rendering claim 35 obvious.
    • Cusani in view of Hsieh (a 1991 technical journal): Argued that Hsieh taught a "diagonalizer" network to eliminate crosstalk by applying an inverse of the transmission matrix, rendering claim 37 obvious.

4. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 15-18, 23, 25, 30, 32-33, 35, and 37 of the ’211 patent as unpatentable under 35 U.S.C. §103.