FWM impairment in multi-wavelength optical code-division multiplexing systems

This paper comprehensively analyzes the impact of four wave mixing (FWM) on the performance of multiwavelength optical code-division multiplexing (MW-OCDM) systems. The impact of FWM on various aspects of MW-OCDM system performance, including bit error rate (BER), the number of users, and power penalty, is quantitatively discussed with several types of optical fibers such as single mode fiber (SMF), dispersion-shifted fiber (DSF), and non-zero DSF considering different frequency spacings. We find that the operational range of optical power is strictly limited under the impact of FMW. For example, it is about 6 dB in the case of spectral amplitude encoding OCDM systems using MQC code (132, 12, 1) and SMF. Also, the impact of FWM can be relieved so as to extend the operational power range by using two dimensional (2-D) codes (especially when different time-spreading patterns are used) or increasing the frequency spacing.