35.88 attenuation lengths and 3.32 bits/photon underwater optical wireless communication based on photon-counting receiver with 256-PPM.

We designed a photon-counting receiver system for long-distance underwater wireless laser communication at different code rate Reed-Solomon (RS) and low-density parity check (LDPC) codes. The symbol error rate (SER) performance of the LDPC and RS codes with different signal-to-noise ratios was analyzed. The effects of the background noise, pulse stretching, and frame synchronization were considered in our receiver system. A water tank experiment confirmed that the 1/2-code-rate RS (255,127) is an excellent coding strategy for communication distances in the range of 90-130 m in Jerlov II water. We constructed a communication link with a SER of 6.31 × 10 in a distance of 120-m distance in Jerlov II water for RS (255,127) with 256-pulse-position modulation (PPM) at bandwidth of 13.7 MHz. The maximum link loss was -136.8 dB at λ = 532 nm. The attenuation lengths Natt were 35.88, which were equal at link distances up to 249.2 m in clear ocean water (Jerlov IB water type). The photon counting receiver system can achieve a receiving performance of 3.32 bits/photon. To the best of our knowledge, this is the longest communication attenuation length ever reported under 1 mJ single pulse energy for a narrow field-of-view photon-counting receiver system.