Analysis of Gaussian Optical Receivers

We present some analytical methods for Gaussian optical receivers whose impulse responses of optical and electrical filters are Gaussian. We obtain the Gaussian optical receiver´s eigenmodes exactly in frequency domain. Their eigenfunctions are Hermite functions multiplied by a common phase factor. Using these eigenmodes, we investigate the probability distribution functions of the electrical filter´s output before the decision circuit. We derive a bit-error rate (BER) expression in a closed form using the lowest-order eigenmode. It is valid when the optical filter bandwidth is comparable to the modulation bandwidth as in conventional high capacity optical wavelength-division multiplexing transmission systems. The BER expression can be applied also to non-Gaussian optical receivers.