Probability density function of noise statistics for optically pre-amplified DPSK receivers with optical Mach–Zehnder interferometer demodulation

We present explicitly semi-analytical probability density functions (pdf’s) of noise statistics in DPSK receivers with Mach–Zehnder interferometer (MZI) demodulation with considering the phase noise for the first time. Error performance of DPSK receivers with MZI demodulation is evaluated by using the calculated pdf’s. It is found that DPSK receivers with MZI demodulation and balanced detection are less sensitive to phase noise impact than those with the single-port detection to some extent. Moreover, it is found that ASE–ASE beat noise induced pdf difference in balanced detection compared to single-port detection may result in ∼3 dB improvement in receiver sensitivity mainly depending on optical filtering, ASE-amplified spontaneous emission. Therefore, the measured receiver sensitivity improvement by using balanced detection consist of the improvements due to signal energy difference and ASE–ASE beat noise induced pdf difference compared to single-port detection.