Optical circulator

An optical circulator is a special kind of optical device with three or four ports, or openings, for light to pass through. It works by letting light enter one port and leave from the next port in line. For example, if light goes into port 1, it leaves from port 2. If some light bounces back, it leaves from the next port after that, like port 3. This helps control light direction in useful ways.

Optical circulators are very important in fiber-optic technology. They help separate light signals going in opposite directions on a single optical fiber. This lets two-way communication happen on one strand of fiber, saving space and materials. They work well with strong isolation between incoming and reflected light and very little insertion loss. They are used in many advanced fiber-optic communications and fiber-optic sensor systems.

These devices are special because they are non-reciprocal. This means that when light passes through them one way, some changes to the light don’t reverse when the light goes the opposite way. This can only happen when something, like an external magnetic field, breaks the normal symmetry. Another device that works this way is a Faraday rotator.

History

In 1965, a person named Ribbens made an early version of an optical circulator using special tools called a Nicol prism and a Faraday rotator. Later, with new technologies like fiber and guided-wave optics, better optical circulators were created. In 2016, scientists showed a new type of circulator that uses a single atom to control light.

In 2013, two researchers suggested a tiny device made with special materials to guide light in one direction.