Electronic Pre-Compensation of Narrow Optical Filtering for OOK, DPSK and DQPSK Modulation Formats

It is shown that electronic pre-compensation effectively reduces the degradation in system performance caused by narrow filtering that arises from the cascading of optical filters in spectrally efficient, wavelength division multiplexed systems. The pre-compensation is based on generating the appropriate electrical drive signals for an optical modulator such that the transmitted optical signal takes into consideration the subsequent optical filtering. Three modulation formats (on-off keying, differential-phase-shift keying and differential-quadrature-phase-shift keying) and two types of optical modulators (dual-drive Mach-Zehnder modulator and dual-parallel Mach-Zehnder modulator) are considered.