Analysis Of The Noise For DPSK Receiver With MZI Balanced Direct Detection

Recently differential phase-shift keying (DPSK) has been suggested for dense wavelength-division multiplexing (DWDM) systems because of higher robustness in the case of fiber nonlinearities.Up to now, two main solutions for detection optical DPSK are known. The first is based on a well-known scheme directly taken from coherent communications, which requires a laser field used a local oscillator. But this leads to complex and expensive receiver design.Another scheme is based on a Mach-Zehnder interferometer with one bit delay in one arm, this scheme can be used to convert the DPSK signal to an IM signal, which is then received by means of a usual direct detection receiver. In this paper, a theoretical analysis of noise statistics in optically pre-amplified DPSK receivers with optical MZI demodulation is presented. The detailed derivation of the noise statistic is considered both the linearly additive noise and nonlinear phase noise. And then, the numerical results of probability density functions and BER with the noise statistics are in good agreement with the published experimental results. The studies not only can improve the performance of the system, but also can provide a significant reference for design and analysis of DPSK receivers system.