Theoretical Study On Microring Resonators Based All Optical Buffers

Optical packet switching (OPS) is recognized as an ideal technique in optical switching configuration for its potentials to match the switching capabilities of OPS network with the transmission capabilities of wavelength division multiplexing system. As a key component in OPS's processing node, all-optical buffer has attracted lots of researchers'attentions recently. Among the reported buffer techniques, buffer based on microring resonators is particularly appealing for its compatibility with CMOS processing technique, delay adjustability, low cost, small size, and so on. This thesis studies the microring resonator-based all optical buffer techniques theoretically and numerically.The main contents and conclusions are as follows.(1) The thesis introduces two kinds of simulation and design methods of microring, including finite difference time domain method (FDTD) and transfer matrix method. Based on these two methods, intensity and phase characteristics of optical field at output of add-drop microring and all-pass microring are derived and discussed. Definitions and expressions of parameters denoting microring's properties are also given.(2) Based on transfer matrix method, theoretical expressions of intensity and delay in all-pass microring are derived. Analysis shows that only under over-coupling condition, can slow light be observed, and that maximum of delay-bandwidth product is 2/π. Moreover, optical signal is piped into micoring and the relation between neighboring bits' crosstalk and delay time is discussed.(3) Circular double-ring resonators (CDRRs) are proposed to cascade rings in a novel manner. Theoretical model of CDRRs is developed based on transfer matrix method. Analysis shows that When the double rings are identical, typical spectra of CDRRs exhibit optical analog to electromagnetically-induced-transparency (OA-EIT) and double ultra-high Q transmission peaks, and that when the double rings are detuned, slow light effect in CDRRs will be greatly enhanced than in DRRs, and there's no need to control the detuning accuracy. Effects of coupling coefficients and loss are also discussed in details.(4) A reflector assisted microring resonator (RAMRR) is proposed to exhibit a spectrum of EIT lineshape. Theoretical model of RAMRR is developed based on transfer matrix method. Firstly, relations between splitting of resonance and structures'' parameters are derived using a simple model of reflectors. Then, based on multi-layer method, model of waveguide bragg gratings is developed and grating assisted microrings are simulated and discussed. Finally, after designing the waveguide parameters, FDTD method is applied to validate the theoretical simulation results.