Recently there is increasing interest to apply the concepts of Optical Signal Processing (OSP) to advanced photonic structures to gain more sophisticated results. This thesis addresses OSP in Photonic Crystal (PhC)-based Microring Resonators (MRRs). The periodic reflections, refractions, and interference in the periodic structure of the PhC material can be used to guide and trap the light in novel ways. A detailed theoretical analysis is presented to characterize wave propagation at 1550nm-wavelength region inside a glass (SiO2) MRR implemented using PhC technology. A PhC reflection is used at each MRR corner to enhance the bending efficiency. The characteristics of both PhC Beam Splitter (BS) and MRR bending losses are analyzed and investigated using two approaches. The first technique is an analytical one based on Effective Refractive Index (ERI) approach which gives approximated results in relative short computational time. The other approach is more accurate and based on Finite Difference Time Domain (FDTD) numerical technique which spends more computational time than the first one. Analytical expressions are also derived to describe the field enhancement inside the MRR, the transfer function of the MRR, and the main parameters characterizing the resonator such as quality factor and Free Spectral Range (FSR). The analysis is also extended to characterize a drop filter implemented using PhC-based MRR. The numerical results presented here are obtained using MATLAB7 while the FDTD simulation is obtained using F2P software. The results indicate clearly that the ERI technique can give accurate results if one starts the calculations with FDTD-estimated BS parameters. Further, bending efficiency as high as 99% can be obtained using a ten-spot layer PhC mirror at each MRR corner.