Implementation requirements for Gbit/s optical receivers with Turbo detection and LDPC decoding

Abstract:
In this paper, we investigate realization aspects of Turbo detection and LDPC decoding for an intensity modulated and direct detected optical transmission link. Target is to find dedicated LDPC codes with overhead of 6.7 % to 14.3 %. Furthermore the influence of quantization is examined. The BER analysis is based on a sophisticated channel model using analytical computation of the branch metrics. It turns out, that an LDPC code of code rate Rc = 0.889 and codeword length N in the range of 9000 bits is most suitable. Sampling of the electrial receive signal requires a resolution of the ADC of 5 to 6 bit. In combination with word lengths of 8 bit at the receiver a performance close to the ideal receiver without any quantization can be achieved.