A Single-Ended, Polarization Insensitive, Fiber Pigtailed Optical Isolator

This paper will describe the design and performance of an optical isolator for fiber optics application having adjacent input and output fibers. The fibers enter at one end of the device. A mirror at the other end images the input fiber into the output fiber. The isolator uses a birefringent walkoff plate, a half-wave plate and a Faraday rotator to produce asymmetric transmission. In the forward direction the two orthogonal polarizations of the laser beam are separated during their first transit through the walkoff plate and are recombined by the second transit, thus providing high transmission. In the reverse (isolation) direction separation of the two polarizations occurs in both transits through the walkoff plate, displacing the focal point of the laser far enough from the input fiber to achieve high loss.