Channel capacity optimization of chirp-limited dense WDM/WDMA systems using OOK/FSK modulation and optical filters

Frequency chirp in semiconductor lasers that are directly modulated through carrier injection not only induces dispersion in long-haul single-mode fiber communication systems, but also causes energy loss and signal distortion when frequency selective elements such as Fabry-Perot filters are present. This effect is significant for high-bit-rate channels in a dense wavelength-division-multiplexed system in a LAN/MAN environment which requires narrow-band filters to suppress crosstalk from adjacent channels. A simulation approach is used to determine the channel capacity in the presence of chirp and crosstalk. The results show that a minimal channel spacing of less than 37 and 10 GHz with each channel operating at 2 Gb/s using OOK and FSK, respectively, can be achieved by a dense wavelength division multiple access system. It is also shown that this system performance can be optimized through adjusting various parameters of the laser and the filter.>