The OC-L-1550 from Thorlabs Inc is a Fiber Optic Circulator with Directivity Greater than 50 dB, Insertion Loss 0.9 to 1.3 dB, Isolation 32 dB, Operating Temperature 10 to 50 Degree C, Optical Power 5000 mW. More details for OC-L-1550 can be seen below.