Fiber Dispersion Phase Shift Method For Monitoring

With the informationization of the society, the demands for information aregreater and greater, which has directly promoted the development of fibercommunication towards high speed, large capacity and long distance rapidly for theoptic-fiber is the main transmission means of communication network. Since theappearance of optic-fiber amplifier, the attenuation is no longer the main factorrestrains the optic-fiber communication system from long distance transmission, thechromatic dispersion caused people's attention gradually. The chromatic dispersionbroaden the wide of digital optical pulse as it transmits through the optic-fiber, causesthe inter-symbol interference, deteriorates the bit error rate, which limits thecommunication capacity and further growth of the communication distance.Especially in dense wavelength division multiplexing system with the channel bit-rateabove 40Gbit/s, it is very important to carry on accurate dynamic compensation forchromatic dispersion to every channel. The chromatic dispersion monitoringtechnology as foundation of dynamic compensation, it is the most important thing tolaunch more research in this field in an effective manner.Based on the deep research on the characteristic of chromatic dispersion, thispaper has proposed an initial chromatic dispersion monitoring method thoughdetecting the phase drift between the two sideband of pilot tone, and has finished thetheory calculation of the monitoring formula by oneself. Then has analyzed theinfluence between the pilot tone and the digital signal and has optimized thefrequency and amplitude of the pilot tone. In the latter segment of the third chapter,the influence of some factor such as the bandwidth of optical filter, chirp of themodulator, self phase modulation, cross-phase modulation, polarization modedispersion, amplified spontaneous emission and four wave mixing has been calculatedwith theory and simulated in emulator. The result indicates, the main disadvantage ofthis monitoring method is its limited range, the influence of amplified spontaneousemission and four wave mixing is negligible, the influence of optical filters'bandwidth, chirp of the modulator, self phase modulation is more regular, can beimproved by revising the monitoring formula, but the influence of cross-phasemodulation, polarization mode dispersion is relatively complicated.To overcome the main disadvantage of the monitoring method using a single pilot...