Silicon-based photonic ring resonators for optical OFDM demultiplexing

Abstract

Abstract:We propose a compact integrated OOFDM demultiplexer based on silicon-based photonic ring resonators, providing cost-effective solution and low energy consumption. 160-Gb/s OOFDM demultiplexing operation is validated, showing excellent BER performance with error-free operation. IntroductionSilicon photonics is a technology platform that enables high density photonic integrated circuits, allows high-bandwidth data processing, and offers low manufacturing cost given by the high compatibility with the already established micro-electronics industry. These features make silicon-based photonic devices a promising candidate to carry out signal processing tasks in future high capacity communication systems.Optical orthogonal frequency division multiplexing (OOFDM) is receiving much attention as a potential technology for increasing transport capacities beyond 100 Gb/s due to its high spectral efficiency and advanced robustness against chromatic dispersion and polarization mode dispersion [1]. The concept underlying OOFDM is the generation of an analog symbol signal (OFDM channel) whose spectral components include multiple subcarriers modulated in parallel by independent data streams with relatively low rates. All the subcarriers are orthogonal to each other so that their spectra overlap, which makes subchannel extraction by means of conventional optical bandpass filtering impossible. As a result, conventional OFDM signal reception is based on discrete fast Fourier transform (FFT) processing [2]. To deal with bit rates beyond 100 Gb/s, the FFT must be done at the optical domain, thus allowing the electrical speed requirements to be relaxed and the energy consumption reduced. In the literature, some all-optical FFT implementations have been proposed [3][4]. Such all-optical FFT circuits can be applied to demultiplex the optical OFDM channel and are usually comprised of several stages, each of which contains appropriate temporal delays and phase shifts. Following this concept, the aim of this work is to exploit the advantages of silicon-based photonic ring resonators (RR) for designing a compact integrated OOFDM demultiplexer. The principle of operation of such a device based on silicon ring resonators is explained and successful simultaneous demultiplexing of four OFDM subchannels consisting of 40-Gb/s-per subchannel NRZ-OOK signals is demonstrated. Simulation results show excellent BER performance for each demultiplexed OFDM subchannel and error free operation is obtained.