A Burst-Mode Photon-Counting Receiver with Automatic Channel Estimation and Bit Rate Detection
MIT Lincoln Laboratory Lexington United States
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We demonstrate a multi-rate burst-mode photon-counting receiver for undersea communication at data rates up to10.416 Mbs over a 30-foot water channel. To the best of our knowledge, this is the first demonstration of burst-mode photon-counting communication. With added attenuation, the maximum link loss is 97.1 dB at lambda517 nm. In clear ocean water, this equates to link distances up to 148 meters. For lambda470 nm, the achievable link distance in clear ocean water is 450 meters. The receiver incorporates soft-decision forward error correction FEC based on a product code of an inner LDPC code and an outer BCH code. The FEC supports multiple code rates to achieve error-free performance. We have selected a burst-mode receiver architecture to provide robust performance with respect to unpredictable channel obstructions. The receiver is capable of on-the-fly data rate detection and adapts to changing levels of signal and background light. The receiver updates its phase alignment and channel estimates every 1.6 ms, allowing for rapid changes in water quality as well as motion between transmitter and receiver. We demonstrate on-the-fly rate detection, channel BER within 0.2 dB of theory across all data rates, and error-free performance within 1.82 dB of soft-decision capacity across all tested code rates. All signal processing is done in FPGAs and runs continuously in real time.
- Non-Radio Communications