| Summary: | 碩士 === 國立東華大學 === 電機工程學系 === 97 === In optic fiber transmission systems, the higher bit rate or farther transmission distance, the heavier dispersion broadens the pulse width. High dispersion degrades the transmission performance and cannot be used in Wavelength Division Multiplexer (WDM) systems. However, zero or too small dispersion induces Four Wave Mixing (FWM) easily such that part of signal power will be transported to noise and increase the bit error rate. Dispersion management system is good management technique. the paper will study on dispersion compensation systems to suppress the effect of FWM and find the optimum parameters of systems.
Therefore, we used the 10Gb/s transmission system to discus the noise produced in different channel spacing and used dispersion compensation systems to suppress the interference of FWM. We used numerical simulation to observe the variation of pulse shape and calculated the power variation ratio to record the soliton power. For different β2 value of fiber, we found the optimum enhance factor and optimum dispersion compensation unit. We tried to take amplifier spontaneous emission noise into our simulation dispersion compensation systems and calculated timing jitter to compare with the performance of systems that with and without dispersion compensation.
In our numerical simulation, under different channel spacing and different β2 values, we found the optimum dispersion spacing is around two to three times of the fiber length. The optimum enhance factor for 160GHz β2=-0.2ps2/km and 80GHz β2=-0.5ps2/km are 1.404 and 1.865, respectively. Under 10 Gb/s transmission rate, without dispersion compensation, the allowed transmission distances with 10-9 bit-error rate for 80GHz β2=-0.5ps2/km and 160GHz β2=-0.2ps2/km are 5550 and 7500 km, respectively。With dispersion compensation, the allowed transmission distances with 10-9 bit-error rate for 80GHz β2=-0.5ps2/km and 160GHz β2=-0.2ps2/km are 12800 and 11600 km, respectively.
It can decrease the timing jitter and suppress FWM interference by switching the dispersion value periodically to do dispersion compensation. The dispersion compensation technique can be used in realizing long-haul distance and high-capacity fiber communication systems.
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