The Polarization Maintaining Optical Circulator is a compact, high performance light wave component that routes incoming signals from Port 1 to Port 2, and incoming Port 2 signals to Port 3.So fiber optic circulators act as signal routers, transmitting light from an input fiber to an output fiber, but directing light that returns along that output fiber to a third port. They perform a similar function as an isolator, protecting the input fiber from return power, but also allowing the rejected light to be employed. DK Photonics offers a large selection of polarization insensitive or polarization maintaining 3-port/4-port optical circulator. These devices can handle powers rang from 300mW to 20W, and have center operating wavelengths ranging from 850nm to 1650nm.