The Research Of Optical Waveguide Interleaver With Tunable Arbitrary Bandwidth Ratio

With the rapid growth of network traffic, global optical communication network isfacing with growing demand for higher bandwidth capacity. Dense wavelength divisionmultiplexing (DWDM) is one of the most economical technologies for increasing theinformation capacity of optical fiber communication. However, this would placestringent demands on all the filtering components used in the system. In order to relaxsuch a stringent requirement, optical interleavers, which can separate a high-channeldensity stream into two complimentary low-channel density streams, are usuallyintroduced by researchers. At the same time, a high data rate transmission technologyhas always attracted significant research interest. As a result, the capacity of commercialoptical transmission system has been moving from10Gbit/s to40Gbit/s. Furthermore,data transfer rates will be further improved in the next few years, real-time100Gbit/stransmission field trials has already reported. In fact, it is maintained to keep thenetwork upgrade capital expense low, DWDM system with hybrid transmission rate is asuitable scheme. However, Different modulation schemes and baud rates would be usedfor different data transfer rates, resulting in different requirements and desiredcharacteristics for the filter passbands. Therefore, it is very essential to research anddesign an asymmetric interleaver for the different transmission rates in hybrid opticalfiber transmission system.In order to solve above problems, an optical waveguide interleaver with tunablearbitrary passband width ratio based on hybrid structure of microring andMach-Zehnder interferometer (MZI) is proposed. Not only can the device achieve asymmetrical output spectrum, but the asymmetrical output spectrum can be obtained bycontrolling some key parameters. Thus, different demands are satisfied in the DWDMsystem.First, the basic structure of the optical waveguide interleaver with tunable arbitrarybandwidth ratio is proposed. Then, some basic structure parameters of the single-modewaveguide and two-mode interferometer which involved in the device are designedaccording to select the suitable waveguide material, and different power distribution ratio can be obtained by selecting different lengths of the two-mode zone.Second, the symmetrical output characteristics of the device are investigated intheory. The structural parameters of the device which can achieve symmetric outputspectral are also analyzed. The results show that symmetrical output spectrum can beobtained by selecting suitable power distribution ratios of three two-modeinterferometers. Then the chromatic dispersion characteristics of the device areinvestigated for the symmetrical output case. Compared with the single-stage MZIinterleaver, the interleaver with hybrid structure is more compact. It also has a betterflat-top passband, and its bandwidth of-1dB is more than6GHz than single-stage MZIinterleaver when free spectral range of interleaver is100GHz.Finally, the asymmetrical output characteristics of the device are investigated. For thecase of the passband width ratio of1:2, the change of output spectra are analyzed whenthe power splitting ratios of the three two-mode interferometer are changed.Furthermore, by analyzing the effect of the three two-mode interferometers on theoutput spectrum bandwidth ratio, the design method of asymmetrical interleaver witharbitrary bandwidth ratios is given. In addition, the impact which caused by some otherfactors such as circumference of the microring, transmission loss on the transmissioncharacteristics is also analyzed. And the method to realize tunable passband width ratiois presented simply at last.