Optical Quasi-Circulator Using Power Couplers and Optical Amplifiers

A new concept for an optical quasi-circulator operating in the 1550-nm band is proposed and experimentally demonstrated in this letter. The quasi-circulator consists of two power couplers, two optical amplifiers, and a pair of attenuators. The power splitters are connected back-to-back and have a high split ratio of 98 : 2. The amplifiers are used as directional devices to block reverse energy flow from Port 2 to Port 1 as well as from Port 3 to Port 2 in the quasi-circulator. The attenuators are used for overall system gain control. Measurements show an insertion loss close to 0 dB in the forward directions from Port 1 to Port 2 and from Port 2 to Port 3.