Abstract: An overview of microwave photonic filters which are implemented in both incoherent and coherent operational regimes has been provided. For microwave photonic filters implemented in the incoherent regime, an incoherence light source usually a broadband light source such as a light-emitting diode source, an amplified spontaneous emission source, or a laser array is needed. Importance of negative coefficients and complex coefficients in photonic FIR filters is discussed in detail. In this paper various technique reported in the last few year for both incoherent and coherent regime microwave photonic filter are reviewed with significance on the system architecture of microwave photonic filters , photonic generation , processing of time-delay microwave photonic signals, tunable and reconfigurable microwave photonic filters. Complexity and challenges in system implementation for widespread use for practical application and possibilities of newer research in microwave photonic were also discussed.

Keywords: Photonic Filters, Microwave Photonics, Optical Source Generation, FIR, IIR, Laser Array.