Design of SOA-based dual-loop optical buffer with a 3 × 3 collinear coupler: guideline and optimizations

In this paper, theoretical and experimental analyses of the semiconductor optical amplifier (SOA)-based dual-loop all optical buffer (DLOB) with a 3 × 3 collinear coupler are presented. Two kinds of DLOB configurations and their choices of nonlinear elements are compared. After that, a novel SOA-based DLOB with Sagnac configuration is proposed. The proposed DLOB is simple, compact, and inherently stable. The required control signal power of this optical buffer (OB) is on the order of 1 mW, and no extra optical amplifier is needed to compensate the power loss. How the linewidth enhancement factor of SOA, the asymmetry power ratio, and the polarization characteristic of 3 × 3 collinear coupler, as well as SOA directional gain difference, may hamper the performance is examined systematically. Finally, the loading and reading operations with DLOB for packet data at the bit rate of 150 Mb/s and 2.5 Gb/s are demonstrated.