Ring resonator with an internal Sagnac loop for dispersion compensation in DWDM backbone networks

In this paper, the dispersive properties of the optical ring resonator (RR) with an internal Sagnac (SG) loop filter are studied for chromatic dispersion managing in digital transmission systems over amplified single-mode fiber (SMF) spans in DWDM backbone networks. Design issues for the architecture as regards quadratic dispersion and magnitude distortion are provided. The RR+SG compound filter provides frequency tunability of the dispersion peaks by adjusting a coupling coefficient of an optical coupler, with no need for using integrated thermo-optic nor current-injection based phase shifters. The configuration can be employed as an additional structure for a general RR-based design and synthesis architecture, allowing bandwidth increase of dispersion compensators. The performance of a compound filter consisting of a two RR in series stage and a RR+SG filter has been simulated over a 200 km amplified SMF span model, obtaining a power penalty enhancement >3 dB for a 5 Gb/s NRZ transmission with a bit error rate (BER) of 10^-9. Comparative simulations with regards to a dispersion compensating fiber span show that the compound filter is a much more compact and effective solution for existing multi-channel SMF backbone links operating at high bit rates.