Physical Review A
Photoelectron statistics of solitons corrupted by amplified spontaneous emission
Takayuki Yoshino, Govind Prasad Agrawal
Abstract
The probability density function (PDF) of photoelectron counts is investigated theoretically for a fundamental soliton corrupted by the spontaneous-emission noise that is generated by optical amplifiers employed along a fiber-optic transmission line. An analysis based on the orthogonal expansion of the light amplitude makes it possible to find the exact PDF that includes the influence of the soliton width, the hyperbolic-secant pulse shape, and a Lorentzian bandpass optical filter. The derived PDF is applicable to any cascaded chain of amplifiers and, as a practical example, is calculated for a receiver equipped with an optical preamplifier. The pulse width significantly affects photoelectron statistics when the product of the filter bandwidth and the counting interval is small. By comparing our exact PDF with the commonly used approximate Gaussian and Laguerre PDFs, we find that such approximations introduce large errors (by several orders of magnitude) in the tail of the PDF that is relevant for calculation of bit error rates in soliton communication systems.