ABSTRACT
Optical filters perform important signal processing functions in optical communication systems, providing bandwidth management for wavelength division multiplexed (WDM) channels and signal conditioning, such as gain equalization and dispersion compensation for highbitrate, long-distance transmission. This chapter focuses on linear, interference filters characterized in the frequency domain by their magnitude and phase response. The inverse Fourier transform of the frequency response yields the time domain behavior, which is called the impulse response. There are many types of optical interference filters. The two most general filter types are finite impulse response (FIR) and infinite impulse response (IIR). The chapter discusses the simplest implementation of FIR and IIR optical filters, so-called single-stage filters. It examines their magnitude and phase response, including dispersion, using lumped elements and Z transforms. The chapter then investigates the filter architectures and synthesis techniques for higher-order filter responses separately for the two general filter types along with practical issues relevant to planar waveguide implementations and applications in WDM systems.
