Experimental Characterization of Turbo-Coded 20 Gbps Fiber-Wireless-Fiber Optical Links

Fiber-wireless-Fiber links require alignment between the transmitter and receiver to a high degree of precision (typically ~ 0.01° for a link of a few meters), and channel coding can be used for mitigating the link margin reduction caused by the limited precision of the beam-steering and tracking system. This paper reports results from an experimental study of the misalignment tolerance attained by channel coding. Explicitly, the received power penalties imposed by misalignment are characterized, and then forward error correction techniques are adopted for mitigating the performance degradation inflicted, which is quantified experimentally. Our results characterize trade-offs between coding rate, decoding complexity and the degree of misalignment. Overall, an improvement of the tolerance to misalignment up to ~50% was attained for coded links compared with the uncoded counterpart.