HIGH-ISOLATION POLARIZATION-INDEPENDENT QUASI-OPTICAL CIRCULATOR

This paper reports a polarization-independent quasi-optical circulator having high isolation over a wide wavelength range. The proposed quasi-circulator is composed of two polarizing beam splitters, two pentagonal prisms, two nonreciprocal rotators, and two walkoff polarizing beam splitters; its structure is very simple. A 3-port quasi-circulator has been fabricated with single-mode fibers. Its insertion loss and isolation have been measured to be less-than-or-equal-to 1.7 and greater-than-or-equal-to 48.6 dB, respectively, at the nominal wavelength of 1.3 mum. Loss ratio over 47.0 dB has been realized. The wavelength range over a 50 dB isolation of Fiber 1 from Fiber 2 was measured to be about 50 nm.