Receivers implementing APDs can easily meet the sensitivity requirements but at a high cost. Avalanche photodiodes are expensive, require high-voltage biasing, and they also 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 solution. However, some design challenges and consequently increased complexity and cost are often overlooked when designing a GPON compatible FEC receiver.
This article describes briefly how FEC works and then illustrates the impact of jitter on a receiver's sensitivity when using FEC. The article also presents actual test data to show the expected performance when using two different types of receiver circuits. This highlights important issues that we should consider when selecting the ONT receiver components of a GPON system that uses FEC.