High-isolation polarization-independent quasi-optical circulator

A polarization-independent quasi-optical circulator having high isolation over a wide wavelength range is reported. The proposed quasi-circulator is composed of two polarization beam splitters, two pentagonal prisms, two nonreciprocal rotators, and two walkoff polarizing beam splitters. Its structure is very simple. A three-port quasi-circulator has been fabricated with single-mode fibers. Its insertion loss and isolation have been measured to beor=48.6 dB, respectively, at the nominal wavelength of 1.3 mu m. A loss ratio of over 47.0 dB has been realized. The wavelength range over a 50-dB isolation between two fibers was measured to be about 50 nm.>