An optical circulator is a non reciprocal device allowing for the Routing of Light from one Fiber to another based upon the direction of the light propagation.
Nonreciprocal optical devices, such as optical isolators and optical circulators, are essential components of optical communication systems. Optical isolators pass light propagating in a forward direction while inhibiting the propagation of light in a backward direction. Optical circulators enable the routing of light from one Optical Fiber or Waveguide to another based upon the direction of light propagation. A circulator has at least three optical ports. These ports can be accessed in such order that when a light beam is caused to enter into an optical port, this light-beam after passing through the circulator to exit from a next optical port. The light enters the circulator through a first port and exits through a second port. Another light that enters the second port exits through a third port and SO on. Since the optical circulator is an inherently non-reciprocal device, the light never goes to other ports. Optical circulators have wide applications. They are used to convert an existing unidirectional fiber optic communication Link to a full Duplex communication link by installing an optical circulator at each end of the link. Optical circulators are also used ill fiber amplification systems, Wavelength division Multiplex (WDM) networks, optical time-domain reflectometers (OTDRs) and for test instruments.