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The present paper describes the system calculation of an optical ASK heterodyne receiver with envelope detection in detail. In particular the intermediate frequency signal and the envelope signal are derived taking account of laser phase noise, additive Gaussian noise, influence of the intermediate frequency filter on both noise terms and intersymbol interferences. Based on the derived envelope the probability density function and the bit error rate are calculated exactly and by useful approximations. In regard of a minimum bit error rate the optimum intermediate filter bandwidth is evaluated as a function of the laser linewidths of the transmitter and the local laser. To highlight typical features of incoherent ASK heterodyne systems simulated eye pattern are presented.

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In the present paper coherent optical transmission systems (ASK and PSK) with homodyne detection will be optimized in regard to a minimum bit-error-rate (BER). By calculating the BER the laser phase noise, the additive Gaussian noise, the influence of the baseband filter on both noise terms and the intersymbol interferences are accounted for. The optimizable system parameters are identified as the PLL bandwidth, the bandwidth of the baseband filter and the decision threshold. It will be shown that the optimal filter bandwidth and the optimal threshold in ASK systems, in contrast to PSK systems, are dependent on the laser phase noise. The calculation of the optimal system parameters will be done exactly and by useful approximations.

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