Recently, there have been many efforts to utilize the high-speed channels operating at beyond 10 Gb/s in the wavelength-division-multiplexed (WDM) network. For the proper operation of these networks, it is essential to compensate the fiber dispersion accurately. Previously, the dispersion compensation has been mostly achieved by using the dispersion-compensating fiber (DCF). However, as the operating speed is increased, it becomes more and more difficult to match the dispersion of transmission fiber precisely. In addition, the use of DCF could increase the deleterious nonlinear effects due to its small effective area. The fiber dispersion could also be compensated by using the optical phase conjugation (OPC). Although this technique is yet to be practical, it is attractive since the dispersion compensation for every WDM channel could be achieved by using only one OPC module placed in the middle of the transmission link. This technique could also compensate various nonlinear effects such as self-phase modulation and stimulated Raman scattering. Thus, in principle, it would be possible to make the transmission link distortionless using OPC.
In this thesis, we investigated the possibility of using OPC in WDM networks. We first compared the performances of the OPC technologies based on semiconductor optical amplifier (SOA) and dispersion-shifted fiber (DSF). The results showed that the DSF-based OPC performed better than the SOA-based one for the use in WDM networks due to its wide bandwidth and low degradation in optical signal-to-noise ratio. Accordingly, we have implemented a DSF-based OPC module and successfully performed a transmission experiment for 5 x 10 Gb/s WDM signals over 640 km of conventional single-mode fiber. These results were used to identify the fiber parameters required for the design of a wide-bandwidth and high-efficiency OPC.
