Theoreitcal Research And Application Of Chirp Fiber Bragg Grating In Communication System

With the rapid development of optical communication, fiber Bragg grating is one of theoptical passive components with the rapid development in recent years. Chirp fiber bragggrating is widely applied in the field of optical communication with great dispersioncompensation, small nonlinearity, good compatibility, low insertion loss, compact structure.Therefore, gradually solving the key problems of fiber grating in the theory and application ofoptical communication will bring great changes to the optical communication field. In thepaper, the paper elaborates the optical characteristics of fiber Bragg grating and dispersioncompensation of high speed transmission system in detail.First of all, the paper introduces in detail the classification of the fiber Bragggrating(FBG) and the basic theory. Based on the coupled-mode theory and the transfer matrixmethod, the paper analyze the optical characteristics of uniform fiber Bragg grating(UFBG),apodization fiber Bragg grating and chirp fiber Bragg grating(CFBG) under differentparameters. The paper can analyze the influence law of reflectivity and side-mode suppressionratio along with length, refractive index modulation and chirp coefficient of fiber Bragggrating. Compared with length and chirp coefficient, refractive index modulation has a greatinfluence on the3dB bandwidth. In addition, chirp fiber grating gets the apodized processing.The ideal optical properties are achieved by using the two common apodization function, anda new apodization function is formulated. The optical properties with a new apodizationfunction are better than the optical properties with the two common apodization function.Second, the paper analyze the dispersion in single mode fiber in detail, the total of thefiber is made up of material dispersion and waveguide dispersion and refractive indexdistribution dispersion. The paper designs dispersion compensation simulation experiments ofhigh speed transmission system by using Optisystem software, there are some comparisonsamong pre-compensation, post-compensation and symmetric-compensation in the dispersioncompensation for the high speed transmission system, at the same time, the paper analyze therelationship between the incident power and bit error ratio. When incident power is small,signal-to-noise ratio is poor and bit error ratio is high; With the increase of incident power,noise signal trails off, so the signal-to-noise ratio of the system increased, as the bit error ratiotrails off; But with the increase of incident power constantly, nonlinear effect has a greatinfluence on the system, the bit error ratio becomes larger.Finally, the paper designs a40/100/160Gb/s optical transmission system. The paperanalyze the third-order diepersion of optical transmission system, which is caused by differentrates, transmission distance, duty cycle, pulse shape and transfer mode. It is concluded thatthe third-order dispersion makes pulse broadening and pulse edge shocking, in addition, pulsecenter develop time-domain migration. With the increase of speed, the time-domain migrationof pulse center also get larger, and the time-domain migration of pulse center is caused by theduty cycle and pulse shape and fiber type.