Cisco Systems, Inc. v. Oyster Optics, LLC

1. Case Identification

• Case #: Unassigned
• Patent #: 6,476,952
• Filed: September 27, 2017
• Petitioner(s): Cisco Systems, Inc. and Oclaro, Inc.
• Patent Owner(s): Oyster Optics, LLC
• Challenged Claims: 1-5

2. Patent Overview

• Title: Fiber Optic Data Transmission System
• Brief Description: The ’952 patent describes a fiber optic data transmission system that uses differential phase shift keying (DPSK) to enhance security against eavesdropping. The system includes a transmitter that encodes data by phase-modulating a continuous wave light source and a receiver with a corresponding interferometer to decode the signal.

3. Grounds for Unpatentability

Ground 1: Obviousness over Bauch and Schneider - Claims 1-3 and 5 are obvious over Bauch in view of Schneider under 35 U.S.C. §103.

• Prior Art Relied Upon: Bauch (Patent 6,826,371) and Schneider (Patent 6,700,907).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Bauch discloses a complete optical DPSK communication system, including a transmitter with a DPSK encoder (using an exclusive-OR gate and a time delay) and a receiver with a corresponding interferometer. However, Bauch was said to lack specific details on how to implement and control the phase modulator for stable, long-term operation. Schneider was argued to supply this missing detail by disclosing a Mach-Zehnder (MZ) modulator with a sophisticated control circuit. This circuit uses a microcontroller, feedback from an optical detector, and digital-to-analog converters (DACs) to adjust bias and gain, thereby compensating for environmental noise and component aging. The combination of Bauch’s DPSK architecture with Schneider’s specific, stable modulator control circuit allegedly renders claim 1 obvious. Dependent claims 2, 3, and 5 were argued to be obvious as they recite features inherent to the combined system, such as Bauch's feedback loop and the 180-degree phase shift intrinsic to DPSK systems.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) designing the DPSK system in Bauch would combine it with Schneider’s teachings to achieve stable, long-term operation. Bauch teaches a generic phase modulator, and a POSITA would look to known, robust modulator designs like the MZ modulator with control circuitry taught by Schneider. The motivation was to substitute a known, stable element (Schneider's modulator) for a generic one (Bauch's modulator) to achieve the predictable result of a reliable communication system.
  • Expectation of Success: A POSITA would have a reasonable expectation of success because combining a well-known modulator control system with a standard DPSK communication architecture was a straightforward implementation. It was well-known that MZ modulators could be used for phase modulation, making the integration predictable.

Ground 2: Obviousness over Bauch, Schneider, and Heflinger - Claim 4 is obvious over Bauch, Schneider, and Heflinger under §103.

• Prior Art Relied Upon: Bauch (Patent 6,826,371), Schneider (Patent 6,700,907), and Heflinger (Patent 6,396,605).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground builds upon the combination of Bauch and Schneider from Ground 1 to address claim 4, which recites an "additional phase modulator" in one of the arms of the receiver's interferometer. While Bauch discloses the receiver interferometer, it does not explicitly teach this additional tuning component. Petitioner argued that Heflinger discloses an interferometer for a DPSK receiver that includes an integrated thermal heater in one arm. This heater functions as an additional phase modulator by altering the optical path length to tune the interferometer and compensate for temperature variations.
  • Motivation to Combine: A POSITA would be strongly motivated to incorporate Heflinger's teachings because Bauch itself explicitly references Heflinger as describing "a method for precisely controlling the optical path difference of such an interferometer." This direct citation provides a clear teaching to look to Heflinger for improving the stability of Bauch's interferometer. The motivation was to solve the known problem of interferometer instability due to environmental changes by incorporating a known tuning solution.
  • Expectation of Success: Success would be expected because incorporating a tuning mechanism like a thermal heater into an interferometer was a known technique for improving stability. The combination would predictably result in a more robust receiver, and Bauch’s reference to Heflinger confirms this was within the skill of a POSITA.

4. Key Claim Construction Positions

• Petitioner argued that the challenged claims are not entitled to the priority dates of earlier patent applications in the family (filed in January and May 2001). Specifically, it was contended that the limitation in claim 1 of "a digital-to-analog converter having an output for altering the phase of the phase modulator" was first disclosed in the application for the ’952 patent itself (filed November 26, 2001). This position is critical because it establishes Bauch and Schneider, with effective prior art dates before November 2001, as valid prior art against the challenged claims.

5. Key Technical Contentions (Beyond Claim Construction)

• A central technical contention was that although Schneider discloses an MZ modulator for modulating intensity, a POSITA would have readily understood that the same device could be used to modulate phase. It was argued to be common knowledge that MZ modulators could perform phase modulation by setting the bias at a minimum point (a null) and varying input voltages to impart a phase shift. This understanding was crucial for establishing the rationale to combine Schneider's control circuit with Bauch's phase-based DPSK system.

6. Arguments Regarding Discretionary Denial

• Petitioner argued that the grounds presented are not redundant with grounds in a concurrently filed petition against the same claims of the ’952 patent. That other petition relied on a different primary reference, Kaneda. The non-redundancy argument was based on the different prior art statuses of the references: Bauch is §102(e) prior art, which the Patent Owner might attempt to "swear behind," whereas Kaneda is §102(b) prior art, which cannot be sworn behind. Petitioner requested that the Board institute review on both sets of grounds.

7. Relief Requested

• Petitioner requested that the Board institute an inter partes review of the ’952 patent and cancel claims 1-5 as unpatentable under 35 U.S.C. §103.