Design Of Asymmetric Optical Interleaver

The technique of symmetric interleaver has developed more and more quickly as an important component in Dense Wavelength Division Multiplexing system, however, it will be a great waste of bandwidth if symmetric interleaver is used to transmit optical signal of 40Gb/s. Asymmetric interleaver has become the new focus because it can help to rebuild the communication system and enlarge its capacity more effectively. It can also enhance the utilization of the bandwidth and reduce the cost of building the system. Based on the model of Mach-Zehnder Interferometer, this thesis studies the process of designing the asymmetric interleaver. The simulation results and the experiment work demonstrate the design theory exactly.Two novel asymmetric interleavers are presented for the first time: two-cascaded MZI asymmetric interleaver and three-cascaded MZI asymmetric interleaver.Firstly, the common method of analyzing fiber interleaver is discussed based on the traditional Mach-Zehnder Interferometer. Some important concepts including dispersion and its effect on communication system are explained in detail.Secondly, the work principle of the Gires-Tournois etalon with three mirrors indicates how to choose the parameters of the GTE. According to the theoretical analysis with Jones Matrix, when there is no GTE, it needs three couplers at least to achieve asymmetric output, no matter from the dispersion point or the energy point. Matlab program simulates the output of the interleavers, the flat-top performance of the three-cascaded interleavers with three mirrors GTE, and the influence from the change of parameters. Furthermore, group velocity delay and dispersion characteristic are studied to explain the importance of dispersion compensation.At last, the three-cascaded MZI asymmetric interleaver is fabricated with the technique of path-length difference emendation, which helps to enhance the performance of the interleaver. Although the experiment results detected by the Optical Spectrum Analysis are not exactly the same with the simulation results, they can still demonstrate the theory wok, for the ripple is introduced by the deviation of the two path-length differences, which can be reduced by more accurate experiment apparatus.