Optical filters are critical components in optical communication, sensors and signal processing. The performance and applicability of optical filters is enhanced considerably through dynamic, post fabrication reconfiguration of their response. This work examines several aspects regarding the synthesis, characterization, implementation and application of dynamic, fiber-optic filters. One category of devices under study is that of linear optical filters, with particular emphasis on multiple-stage, moving average lattice filters. A second category is that of nonlinear filters, in which a stimulated Brillouin scattering pump wave imposes a highly reconfigurable transfer function on a counter-propagating probe wave. Specific examples include broadband, variable-delay “slow light” elements, highly selective spectral windows, high resolution spectro-polarimeters, polarization mode dispersion mitigators and many more. The methods and results included in this book extend the versatility of optical filters, and should be of much interest to professionals in the areas of optical communication and microwave photonics.