Challenges mark GPON FEC receiver designs

摘要

APD or FEC in the ONT? That is the question— or, at least if not the question, it does weigh on the minds of many GPON system vendors. Receivers that implement avalanche photo-diodes (APDs) can easily meet the sensitivity requirements expected at the GPON optical network terminal (ONT), but at a high cost. APDs are expensive, require high-voltage biasing, and need to be temperature compensated. FEC adds some cost and complexity to implement the encoding and decoding but is generally believed to be much less expensive than an APD. However, some design challenges and consequently increased complexity and cost are often overlooked when designing a GPON-compatible FEC receiver.