Performance of convolutional codes in a direct-detection optical PPM channel

Several strategies for combining convolutional codes (CCs) and pulse position modulation (PPM) in a direct-detection optical channel are considered, including binary and 2ⁿ-ary PPM with rate-1/ n CCs, 2^m-ary PPM with a dual-m CC, and interleaved 2^L-ary PPM with a rate-1/n CC. In the latter case, J.L. Massey´s (1981) concept of coding of L separate component channels constituting a 2^L-ary PPM erasure channel is carried out for both the ideal photon counting and the avalanche photodetection (APD) cases, providing a comparative evaluation of the various strategies in terms of bit error probability and achievable coding gain for different code structures and decoding schemes