Abstract
We present a novel investigation on the enhancement of phase noise in coherent optical transmission system due to electronic chromatic dispersion compensation. Two types of equalizers, including a time domain fiber dispersion finite impulse response (FD-FIR) filter and a frequency domain blind look-up (BLU) filter are applied to mitigate the chromatic dispersion in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying (PDM-QPSK) transmission system. The bit-error-rate (BER) floor in phase estimation using an optimized one-tap normalized least-mean-square (NLMS) filter, and considering the equalization enhanced phase noise (EEPN) is evaluated analytically including the correlation effects. The numerical simulations are implemented and compared with the performance of differential QPSK demodulation system.
Highlights
The performance of high speed optical fiber transmission systems is severely affected by chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise (PN) and nonlinear effects [1,2,3,4]
We present a detailed analysis on the impact of the dispersion equalization enhanced phase noise in the coherent transmission system using two electronic dispersion equalizers: a time domain fiber dispersion finite impulse response (FD-FIR) filter and a frequency domain blind look-up (BLU) filter [22,23,24,25]
Simulation results 5.1 Phase estimation considering enhanced phase noise (EEPN) with different CD equalization In Fig. 6, the FD-FIR equalization performance in the coherent transmission system with different fiber length is compared with the adaptive LMS dispersion equalization, where the results are processed by further using a one-tap normalized least-mean-square (NLMS) filter for carrier phase estimation
Summary
The performance of high speed optical fiber transmission systems is severely affected by chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise (PN) and nonlinear effects [1,2,3,4]. Lau et al have provided the theoretical assessment and analysis to evaluate the equalization enhanced phase noise (EEPN) from the interaction between the LO phase fluctuation and the fiber dispersion in coherent transmission system [14,15,16,17]. J. Savory have studied the influence of the equalization enhanced phase noise in QPSK, 16-level quadrature amplitude modulation (16-QAM) and 64-QAM coherent transmission systems by employing the time-domain CD equalization [20]. It would be of interest to investigate in more detail the bit-error-rate (BER) performance of the equalization enhanced phase noise in the coherent optical communication system employing electronic chromatic dispersion compensation. The CPE performance of the one-tap NLMS digital filter and the differential phase demodulation are comparatively analyzed
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