Internally bandwidth efficient channel coding for fiber-optic CDMA communication systems with soft-input decoding

We consider using a soft-input decoder for internally bandwidth efficient convolutionally coded fiber-optic code division multiple access (CDMA) communication systems using optical orthogonal codes (OOC). The convolution codes that are used for demonstrating the capabilities of the soft-input decoder are super orthogonal codes (SOC). These codes are near optimal and have a relatively low complexity. We evaluate the upper bounds on the bit error probability of the internally coded fiber-optic CDMA system using soft-input and hard-input decoders, assuming both on-off keying (OOK) and binary pulse position modulation (BPPM) schemes. It is shown that the soft-input decoder significantly outperforms the hard-input decoder.