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

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Abstract
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-mutiplexed system in a LAN/MAN environment which requires narrow-band filters to suppress crosstalk from adjacent channels. In this paper, a simulation approach is used to determine the channel capacity in the presence of chirp and crosstalk. Our 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. We also show that the system performance can be optimized through adjusting various parameters of the laser and the filter.