PTAB

IPR2018-01158

NEC Corp v. Neptune Subsea IP Ltd

Log In
Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Distinct Dispersion Compensation for Coherent Channels
  • Brief Description: The ’068 patent discloses an optical assembly for use in fiber optic communication networks. The assembly receives a mixed optical signal containing both coherent and non-coherent wavelength channels, demultiplexes them into separate optical paths, applies different amounts of dispersion compensation to each path, and then multiplexes them back together.

3. Grounds for Unpatentability

Ground 1-A: Obviousness over Tanaka and Ip - Claims 1-9, 11-13, and 15 are obvious over Tanaka in view of Ip.

  • Prior Art Relied Upon: Tanaka (Patent 8,625,996) and Ip (a 2008 article in Optics Express titled "Coherent detection in optical fiber systems").
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Tanaka taught the core structure of the claimed invention. Tanaka disclosed an optical transmitter that receives a multiplexed signal containing both intensity-modulated and phase-modulated optical channels. It then splits these channels into separate paths, applies chromatic dispersion compensation to only one of the paths (e.g., the phase-modulated path), and then recombines the signals. Petitioner contended that a person of ordinary skill in the art (POSITA) would have understood that Tanaka's phase modulation techniques (DPSK and DQPSK) are examples of coherent modulation, and its intensity modulation technique (on-off keying) is an example of non-coherent modulation. Ip was cited to explicitly teach this distinction, stating that on-off keying is an example of non-coherent detection and that methods like those used by Tanaka for phase modulation are forms of coherent detection, where the full electric field (amplitude and phase) is measured.
    • Motivation to Combine: Petitioner asserted a POSITA would combine the teachings of Ip with Tanaka’s system to achieve predictable benefits. Ip described coherent detection as the "most advanced detection method" for achieving higher performance, greater spectral efficiency, and better compensation for transmission impairments. A POSITA would have been motivated to apply these known benefits to Tanaka's system, which was designed for upgrading existing transmission networks. Combining the systems was argued to be a straightforward application of a known technique (coherent detection) to a known system (Tanaka's optical architecture) to yield predictable improvements. The motivation was further strengthened by Tanaka’s own disclosure that combining modulation types is necessary when upgrading transmission systems efficiently.
    • Expectation of Success: Petitioner asserted a high expectation of success because applying Ip's known detection principles to Tanaka's well-defined system architecture involved combining compatible and well-understood optical communication technologies.

Ground 1-B: Obviousness over Tanaka, Ip, and Okuno - Claims 2-5 and 14 are obvious over Tanaka in view of Ip and Okuno.

  • Prior Art Relied Upon: Tanaka (Patent 8,625,996), Ip (an Optics Express article), and Okuno (Patent 6,611,637).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon the Tanaka and Ip combination by adding Okuno to teach the limitation in dependent claim 2 requiring "one or more optical elements... configured to approximately equalize the optical gain or loss" of the separate coherent and non-coherent paths. Okuno disclosed a dispersion-compensating module that explicitly used "optical attenuators... in each respective optical path to equalize the loss across each path." Petitioner argued that Okuno’s disclosure of using optical attenuators for loss equalization directly met this claim limitation.
    • Motivation to Combine: A POSITA would combine Okuno's teachings with the Tanaka/Ip system to solve the known problem of non-uniform signal quality caused by wavelength-dependent loss deviations in dispersion-compensating systems. Okuno taught that including loss-equalizing elements like optical attenuators provides uniform signal quality and prevents waveform deterioration. Petitioner argued it would have been obvious to incorporate this known solution from Okuno into the Tanaka/Ip system to improve its overall performance and signal integrity, a predictable improvement.

Ground 1-D: Obviousness over Tanaka, Ip, and Evans - Claim 10 is obvious over Tanaka in view of Ip and Evans.

  • Prior Art Relied Upon: Tanaka (Patent 8,625,996), Ip (an Optics Express article), and Evans (Patent 6,310,716).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground added Evans to teach the specific limitation of claim 10, which depends from claim 7 and requires an optical amplifier in the non-coherent path with sufficient gain to compensate for 50-150% of the loss from other elements in that path. Evans disclosed an amplifier system where dispersion compensating fiber, which introduces signal loss, is pumped with light "just enough to provide no net gain or loss," making it a "loss-less compensator." Petitioner argued this amounted to 100% loss compensation, falling squarely within the claimed range.
    • Motivation to Combine: A POSITA would have been motivated to apply the teachings of Evans to the Tanaka/Ip system to solve the known problem of signal loss introduced by dispersion compensating elements. Evans provided an explicit solution: add an amplifier to offset this loss. A POSITA would apply this solution to the dispersion compensating element in the non-coherent path of the Tanaka/Ip system to achieve lossless dispersion compensation, thereby improving signal integrity and reducing data error rates without significantly altering the system.
  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combinations incorporating Tsukitani (Patent 7,292,748) for its teachings on amplifier placement and Charlet (Application # 2007/0189775) for its teachings on interspersing different types of repeaters in a transmission line.

4. Key Claim Construction Positions

  • "coherent optical wavelength channels" (Claims 1, 13): Petitioner proposed this term be construed as "optical wavelength channels having the ability to measure the electric field of the transmitted channel during detection (both amplitude and phase)." This construction was argued to be consistent with the patent specification and crucial for mapping the teachings of Ip (which defines coherent detection similarly) onto the system disclosed in Tanaka.
  • "dispersive element" / "optical element" (Claims 1-4, 7-8, 10-11, 13): Petitioner argued that these terms should be given their plain meaning and not be treated as means-plus-function limitations under 35 U.S.C. §112, ¶6. Petitioner noted that while the terms lack the word "means," they would still map the prior art to the structural elements disclosed in the ’068 patent’s specification if such a construction were applied.

5. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-15 of the ’068 patent as unpatentable.