Patent ID: 9749123
Date: 2017-08-29
CPC Classifications: H04B,H04L

Claim:
1. A method comprising: receiving, at a first communication terminal, an optical signal containing an incoming stream of data from a second communication terminal through a free space optical link, the first communication terminal having a clock and data recovery circuit operable in a normal mode to synchronize a recovered clock with the incoming data stream for recovering data from the optical signal; determining, by control hardware of the first communication terminal, a receiving power for the optical link based on the optical signal, the control hardware implementing the clock and data recovery circuit; comparing, by the control hardware, the receiving power to a first receiving power threshold; when the receiving power for the optical link is less than the first receiving power threshold, transitioning, by the control hardware, the clock and data recovery circuit from the normal mode to a holdover mode, the clock and data recovery circuit, when operating in the holdover mode, configured to hold the recovered clock to a known-good clock frequency when optical fading over the optical link is absent; comparing, by the control hardware, the receiving power to a second receiving power threshold; and when the receiving power for the optical link is greater than the second receiving power threshold: