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Optical Link Wavelength Adaptor

Table of Contents

Optical Link Interface PCB Design #

Overview #

This project involved designing a purely analog PCB to interface two optical links running the same digital protocol but operating at different wavelengths. The adapter converted signals between an 820 nm Avago HCS fiber link and a modern 1310 nm SFP link. By maintaining an analog approach, the design ensured the lowest possible latency while enabling seamless bidirectional communication.

Key Features and Achievements #

  • Analog Signal Conversion:
    • Adapted PECL output from the Avago HCS fiber link to the LVDS input of the SFP module.
    • Designed a fully analog, bidirectional interface to minimize latency for both upstream and downstream data flow.
  • Schematic Design:
    • Developed precise analog schematics using Cadence OrCAD.
    • Provided layout guidance for critical design elements, ensuring signal integrity and power efficiency.
  • Manufacturing Coordination:
    • Collaborated with the PCB manufacturing facility to ensure proper delivery of all components and design specifications.
    • Verified manufacturing accuracy for controlled impedance and signal isolation.
  • Power Management:
    • Integrated a low-noise, efficient power supply to support the optical modules and analog circuitry.
  • Design Considerations:
    • Focused on analog components and techniques to achieve low-latency signal adaptation.
    • Implemented controlled impedance traces and isolation for high-speed signaling.

Technical Details #

  • Hardware Specifications:
    • Input Link: 820 nm Avago HCS fiber with PECL signaling.
    • Output Link: 1310 nm SFP module with LVDS signaling.
    • Fully analog, bidirectional data flow for upstream and downstream communication.
  • Design Tools:
    • Cadence OrCAD for schematic design.
    • Layout performed externally with guidance on critical analog design aspects.
  • PCB Design Features:
    • Controlled impedance traces to ensure high-speed signal integrity.
    • Signal isolation techniques to minimize crosstalk and noise.
    • Low-latency analog signal path to meet stringent timing requirements.
  • Manufacturing:
    • Collaborated with the PCB factory to ensure accurate production.
    • Delivered comprehensive manufacturing files and verified production processes.

Challenges and Solutions #

  • Latency Reduction: Chose a purely analog design approach to eliminate delays associated with digital processing.
  • Signal Integrity: Maintained robust signal integrity through controlled impedance and optimized layout for high-speed communication.
  • Precision Manufacturing: Ensured accurate PCB fabrication by working closely with the manufacturer, particularly for analog circuit specifications.
  • Compatibility: Bridged the gap between legacy Avago HCS fiber systems and modern SFP technology through analog signal adaptation.

Outcome #

The analog PCB design provided a high-performance interface between two optical link technologies, achieving the lowest possible latency while ensuring reliable bidirectional communication. The project successfully balanced legacy and modern technologies with precision analog design, robust signal adaptation, and efficient power management, meeting all functional and performance requirements.