BIT-ERROR RATE OF LIGHTWAVE SYSTEMS AT THE ZERO-DISPERSION WAVELENGTH

The bit-error rate of very long lightwave systems with optical amplifiers is usually computed under the assumption that a linear superposition of signal light and amplified spontaneous emission noise enters the receiver. However, in very long lightwave systems operating at or very near the zero-dispersion wavelength, the power in the light signal acts as a pump which causes amplification of the spontaneous emission noise so that the signal becomes almost completely converted to noise by the process of nonlinear four-wave mixing. For this reason it seems more appropriate to consider the signal as noise-like and derive the bit-error rate under the assumption that the (residual) optical power representing a logical ZERO as well as the optical power representing a logical ONE can both be regarded as random Gaussian noise. We derive mathematical expressions for the bit error rate under this assumption.