A tutorial on microwave photonic filters

Abstract

We report a simple technique in microwave photonic (MWP) signal processing that allows the use of an optical filter with a shallow notch to exhibit a microwave notch filter with anomalously high rejection level. We implement this technique using a low-loss, tunable Si 3 N 4 optical ring resonator as the optical filter, and achieved an MWP notch filter with an ultra-high peak rejection > 60 dB, a tunable high resolution bandwidth of 247-840 MHz, and notch frequency tuning of 2-8 GHz. To our knowledge, this is a record combined peak rejection and resolution for an integrated MWP filter.

Importance of Intrinsic-$Q$ in Microring-Based Optical Filters and Dispersion-Compensation Devices

“…Photonic counterparts of the well-known RF filter 1041-1135/$25.00 © 2007 IEEE for three values of Q in a third-order Butterworth filter. The intrinsic-Qs are chosen based on available microring technologies: semiconductor and polymers (10 ) [8], [9], Hydex (10 ) [2], and silica microtoroids (10 ) [7].…”

“…One of the challenging tasks for photonic filter design is building a narrow bandwidth box-like (large slope) filter with low insertion loss. These three characteristics are essential in many optical communication and RF-photonic signal processing systems where narrowband, low loss, and high rejection of closely spaced frequency components is required [10], [11]. Although the exact -dependence of insertion loss and roleoff varies in different filter designs, it is useful to define a figure-of-merit that highlights the role of quality factor in the overall performance of a filter.…”

Experimental transmission in a fiber-radio system using a microwave photonic filter at 2.8GHz

“…Another interesting application that attracts interest in research is the filtering of microwave signals by using photonic techniques. The main feature of a photonic filter is that microwave signals are directly processed in the optical domain exploiting advantages inherent to photonics such as low loss, high bandwidth, immunity to electromagnetic interference, and tunability [2]. On the other hand, network architectures such as FTTx, where x can stand for home (H), building (B), neighborhood (N), or curb (C), are a communication architecture in which the final connection to the subscribers is optical fiber [3].…”

Opto-VLSI-based reconfigurable photonic RF filter

“…These advantages open new opportunities in a wide range of potential applications where high selectivity, resolution, wide tunability, and fast reconfigurability characteristics are required [1].…”

“…Several tunable photonic RF filter structures have been proposed and demonstrated [1][2][3][4][5][6]. In these demonstrations, filter reconfigurability is achieved by adjusting the tap weights through optical attenuation via MEMS switches [2], using variable optical attenuators (VOAs) [4], or employing Fiber Bragg Gratings (FBG) [5] that can be tuned either thermally or mechanically.…”