Interleaved Bidirectional Transmission of 16 $\times$ 10-Gb/s DWDM Signals Using DPSK Modulation Format and In-line Semiconductor Optical Amplifiers

We have performed both experimental and numerical analyses of interleaved bidirectional transmission of 16 times 10-Gb/s dense-wavelength-division-multiplexed (DWDM) signals using differential-phase-shift-keying (DPSK) modulation format and in-line semiconductor optical amplifiers (SOAs). The constant intensity of DPSK-modulated DWDM signals enabled us to mitigate the crosstalk effects in the bidirectional SOA. We have demonstrated error-free bidirectional transmission of 16 channels over an 80-km single-mode fiber (SMF) with matching dispersion-compensating fiber and in-line amplification provided by an SOA. SOAs can be used for bidirectional transmission if the facet reflections can be controlled. In order to understand further the effect of the SOA facet reflectivity on transmission results, we developed a simulation model for our system. Based on the good agreement between our simulation and experimental results, we have found out that the system reflections can be minimized by careful optimization of the bias current and reflectivity of the SOA