Performance Analysis of Coherent Optical Fiber Systems Using

• Main Authors: Ja-Nan Wang, 王家男
• Other Authors: 賀嘉律
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/70544887160729825946

博士 === 國立中央大學 === 電機工程研究所 === 89 === The BERs of CPFSK and FSK receivers are numerical computed efficiently. The effects of shot and laser phase noise are taken into account. For a particular realizations of laser phase noises, the BER is expressed as a Laplace inversion integral. It is then averaged with respect to the distribution of the phase noise. The method of changes of variable is used twice in the computation, and the results converge rapidly. Gaussian approximation of outputs of CPFSK receivers is derived. However, for ideal and Gaussian frequency shapes, Gaussian approximation methods are shown to be not so accurate for the case of low BER. We have established the models of noises and FSK signals in coherent communication systems. These simulations can be implemented systematically to compute the BER of the receivers and histograms of probability distributions of outputs. They can also be applied to checking the validity of performance analyzation. By using importance sampling method we computed the low BER without consuming much computer CPU time. So we can use these simulation methods to assistant the practical system design, which is considered for very low BER. In fact, it is so efficient that we only utilized common personal computers as simulation platforms. Furthermore, a random number generator with a very long period is no longer necessary for the shorter convergent time. From the results of computer simulation, we found that Gaussian approximation overestimate the system performance. One reason is that shot noises in coherent frequency modulation systems may not obey any type of large number theory well enough to utilize Gaussian approximation.