Electronic signal processing for cancelation of optical systems impairments

Abstract EN

In this paper 40 Gb / s DP-QPSK system with coherent reception and DSP unit for optical fiber impairments compensation is proposed.

The DSP unit processes the detected coherent DP-QPSK signal.

The Chromatic Dispersion (CD) is compensated using a simple transversal digital filter and Polarization Mode Dispersion (PMD) is compensated using adaptive butterfly equalizer which is realized by applying the constant-modulus algorithm (CMA).

A nonlinear compensator (NLC) is used for compensating the nonlinear effects based on the technique of multi-span back propagation.

A modified Viterbi -and- Viterbi phase estimation algorithm (working jointly on both polarizations) is then used to compensate for phase and frequency mismatch between the transmitter and local oscillator (LO).

After the digital signal processing is complete, the signal is sent to the detector and decoder, and then to the BER test set for direct-error-counting.

The presented system is designed and simulated using OptiSystem (2011) software interfaced with MATLAB software R2011a for implementing the DSP unit algorithms.

The performance of each part of the system is analyzed by showing the optical spectrum, RF spectrum, electrical constellation diagrams, eye diagram and BER performance for different sampling rates and different bit rates.