Reconfigurable Filter-free Sinc-shaped RF Photonic Filters Based on Rectangular Optical Frequency Comb

Abstract

Abstract:We demonstrate reconfigurable sinc-shaped RF photonic filters based on rectangular optical frequency comb synthesized from cascaded modulators. Simplicity of the approach and flexibility in bandwidth for fixed free-spectral-range is shown. Phase response is also investigated.OCIS codes: (060.5625) Radio frequency photonics; (120.2440) Filters; (230.2090) Electro-optical devices IntroductionRadio frequency (RF) filters based on optical frequency comb and dispersive propagation enable RF signal processing in the photonic domain [1,2]. Compared to its electrical counterpart, this approach is favored due to the broad bandwidth and low losses rendered by optical fibers, as well as arbitrary RF filter shape empowered by lineby-line shaping of the optical frequency comb [2,3]. For instance, highly selective rectangular RF filter shape has been demonstrated using programmable pulse shapers to tailor optical frequency comb [4] or slice ASE source [5]. From a communication perspective, sinc-shaped RF photonic filters may offer great potential to high-speed orthogonal frequency division multiplexing (OFDM), optimizing the spectral efficiency among electrical, optical, and wireless applications. Given the complex features of sinc-shaped filter, direct implementation in the electrical domain is challenging. In this paper, we present reconfigurable RF photonic filters with near perfect sinc response based on a simple versatile comb source. The comb is synthesized using a cascade of Mach-Zehnder modulators (MZMs) driven by synchronized RF frequencies [6], resulting in rectangular spectra without the need for spectral shaping. The proposed RF filter scheme can be easily reconfigured by modifying the RF signals (frequency, power) and DC bias driving the comb source modulators. The flexibility of the proposed RF filter is here demonstrated by varying the number of comb lines, thereby the number of filter taps, while keeping the repetition rate constant and a near perfect sinc filter shape.

Reconfigurable Optical Frequency Comb and Nyquist Pulses Generation With Tunable Sensitivities

“…In future optical networks, it is crucial to develop all-optical signal sampling and processing to avoid the limits of electronic bottlenecks. Sinc-shaped Nyquist pulses are also considered as promising candidates for the future photonic analog-to-digital conversion [4] and microwave filtering devices [5] due to them temporal and spectral features,…”