Reduction of intrachannel four-wave mixing using the alternate-phase RZ modulation format

The authors propose a modulation format in which the phase of the signal pulses alternates, in order to reduce the intrachannel four-wave mixing. They demonstrate numerically that the performance of a 40-Gb/s transmission link can be substantially improved.     

Asynchronous Phase Modulation for the Suppression of IFWM

Intrachannel four-wave mixing (IFWM) represents main source of impairments in fiber transmission at 40 Gb/s. A number of phase modulation techniques have been proposed to suppress the IFWM. In this paper, we study a cost-effective way of increasing the nonlinear tolerance of a 40-Gb/s wavelength division multiplexing transmission system by asynchronous phase modulation (APM). This can be achieved with one phase modulator placed after the wavelength multiplexer so that cost is shared by all channels. We show, by means of numerical simulations and laboratory experiments, that APM greatly improves the performance of ON-OFF-keying transmission.     

Performance analysis of single-MZM APRZ transmitters

In this paper, an efficient single Mach-Zender modulator (MZM) implementation of alternate-phase return to zero (APRZ), which combines carrier-suppressed return to zero (CSRZ)'s ease of implementation with APRZ's nonlinear tolerance, is analyzed. In particular, the first numerical study of 67%-duty-cycle single-MZM APRZ over a 40-Gb/s 5 /spl times/ 100-km link, in terms of nonlinear, dispersion, and filtering tolerance, comparing it with 33% RZ, 33% APRZ, and standard 67% CSRZ, is presented. The results show that APRZ with phase shift close to /spl pi//2 is the optimum choice, independent of specific transmitter implementation. A new mechanism is also discovered, based on the interference of ghost pulses with the original pulse train, which improves the nonlinear tolerance of CSRZ in a 40-Gb/s transmission.