The PMOCIR-4-B from COMCORE Technologies is a Fiber Optic Circulator with Directivity 50 dB, Insertion Loss 2.4 to 2.8 dB, Isolation 20 to 30 dB, Operating Temperature -5 to 50 Degree C, Optical Power 300 mW. More details for PMOCIR-4-B can be seen below.