The present techniques provide systems and methods for decoding an optical data signal in an optical system to retrieve source information while decreasing errors resulting from optical and electronic noise in the optical system. The techniques involve using decoding algorithms to estimate the a posteriori state probabilities and the a posteriori transition probabilities of the data encoding, and estimating bit state probabilities. The probability density function used to estimate bit states is parameterized by the expected optical and electronic noise in the optical system. Different optical and electronic noise variances, or different probability densities, may be stored in registers or look-up tables to be accessed by a decoder while decoding the optical data signal.