Optical Isolator

What Does Optical Isolator Mean?

An optical isolator is a passive magneto-optic device that makes travel of light unidirectionally. The operation of the device is based on the Faraday effect. It is used in applications to avoid unwanted feedback to the system using the optical isolator.


Optical isolators are also known as optoisolators, optocouplers and photocouplers.

Techopedia Explains Optical Isolator

An optical isolator is comprised of a Faraday rotator with magnet, input polarizer and output polarizer. The input polarizer is arranged to act as a filter and only allows linearly polarized light into the rotator. The rotator then rotates the polarization of the input light by 45 degrees and is allowed to exit through the output polarizer. In this manner, energy is either absorbed or reflected depending on the polarizer type. Optical isolators are available with high power and low-power polarizers.

Optical isolators can also be categorized into polarization-dependent isolators and polarization-independent isolators. Polarization-dependent isolators use input and output polarizers along with a Faraday rotator, whereas polarization-independent isolators use input and output birefringent wedges along with a Faraday rotator.

Optical isolators are used in many applications, such as laser applications where they are used to prevent unwanted feedback into the laser source. This helps in not affecting the coherence of the laser affecting any damage to the diode itself as feedback is capable of frequency shift, noise, mode hopping or amplitude fluctuation. It is thus a key device in order to achieve stable laser diode operation. In high-speed optical fiber transmittance amplifiers and routes, they are considered indispensable devices due to their capability of eliminating the adverse effect of return beams.


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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.