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: Optical Data Transmission System
• Brief Description: The ’952 patent discloses a fiber optic data transmission system using phase-shift modulation, specifically differential phase shift keying (DPSK), to improve security against eavesdropping. The system includes a transmitter that encodes data by shifting the phase of a light signal and a receiver with an interferometer to decode the data by detecting these phase shifts.

3. Grounds for Unpatentability

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

• Prior Art Relied Upon: Kaneda (Japanese Unexamined Patent Application Publication No. S61-127236) and Schneider (Patent 6,700,907).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Kaneda discloses a fundamental DPSK optical transmission system, including a transmitter with a laser, a "finite sum logic conversion circuit" (an exclusive-OR gate with a time delay) for differential encoding, and a phase modulator. The receiver in Kaneda uses a free-space interferometer with two arms of different lengths to decode the signal. However, Petitioner asserted Kaneda lacks specific implementation details for its phase modulator and its control circuit. Schneider was argued to supply these missing details by disclosing a Mach-Zehnder (MZ) modulator with a sophisticated control circuit, including a microcontroller, feedback loop, and digital-to-analog converters (DACs). This circuit in Schneider adjusts the modulator's bias to compensate for environmental noise, temperature changes, and component aging to ensure stable operation. The combination of Kaneda's overall DPSK architecture with Schneider's specific, stable modulator implementation was alleged to render the system of claim 1 obvious. Dependent claims 2, 3, and 5 were argued to be obvious for reciting features explicitly taught or suggested by Kaneda, such as the use of an exclusive-OR gate in a feedback loop (claim 2), a 180-degree phase difference in the receiver (claim 3), and a phase compensation circuit (claim 5), which is taught by Schneider's bias control.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) designing the DPSK system in Kaneda would have sought to ensure its long-term, stable operation. Petitioner contended that Schneider addresses this exact problem by providing a detailed implementation of an MZ modulator with control circuitry to maintain stability against real-world factors. A POSITA would combine Kaneda's system with Schneider's modulator technology as a known solution to a known problem, substituting a known, stable component (Schneider's modulator) into a known system (Kaneda) to achieve the predictable result of a reliable DPSK system.
  • Expectation of Success: Because Schneider provided a well-understood method for stabilizing an optical modulator, a POSITA would have had a high expectation of success in applying this technology to Kaneda's DPSK transmitter to achieve improved operational stability.

Ground 2: Claim 4 is obvious over Kaneda in view of Schneider and Heflinger under §103.

• Prior Art Relied Upon: Kaneda (Japanese Application # S61-127236), Schneider (Patent 6,700,907), and Heflinger (Patent 6,396,605).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground built upon the combination of Kaneda and Schneider from Ground 1 and added Heflinger to address claim 4. Claim 4 adds the limitation that the receiver's interferometer includes an "additional phase modulator" in one of its arms. Petitioner argued that while the Kaneda/Schneider combination discloses the system of claim 3, it does not explicitly disclose this additional modulator in the receiver. Heflinger was argued to cure this deficiency by teaching an interferometer for a DPSK receiver that includes a mechanism, such as a piezoelectric transducer (PZT), to tune one of the optical paths. This PZT acts as an additional phase modulator, altering the optical path length to compensate for environmental variations, particularly temperature changes.
  • Motivation to Combine: A POSITA implementing the receiver interferometer from Kaneda would have recognized its susceptibility to temperature variations, a known issue for such components. Heflinger explicitly addresses this problem by teaching the use of a tuning mechanism (the "additional phase modulator") to improve thermal stability. Petitioner argued a POSITA would be motivated to incorporate Heflinger's tuning solution into the Kaneda/Schneider receiver to make it more robust and reliable, which represents a simple substitution of a known element (a tunable interferometer for a non-tunable one) to obtain a predictable benefit.
  • Expectation of Success: A POSITA would have reasonably expected that adding a known tuning mechanism as taught by Heflinger to the receiver's interferometer would successfully compensate for thermal drift and improve the overall performance and stability of the DPSK system.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that the grounds presented in this petition, which rely on Kaneda as §102(b) prior art, are not redundant with grounds in a concurrently filed petition against the same claims that rely on Bauch (Patent 6,826,371) as §102(e) prior art. Because a Patent Owner may attempt to "swear behind" §102(e) art like Bauch but cannot do so for §102(b) art like Kaneda, Petitioner requested that the Board institute review on both sets of grounds to prevent procedural gamesmanship and ensure a complete review on the merits.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-5 of Patent 6,476,952 as unpatentable.