Simple Phase Control System in Bidirectional Ring Laser

Abstract

Optical sensors are commonly used and most of them detect the variation of light intensity and then if there is the uctuation of light source intensity or change in propagation loss it causes measurement errors. A ring laser sensor is one of the potential candidates which are insensitive to such uctuation, but it has mainly two problems. One is lock-in effect and the other is insensitiveness to detect the sign (polarity) of the sensing signal. To solve these problems a new phase control system has been proposed. It consists of two polarizers, two quarter-wave plates, and one Faraday rotator. Using this system the phase is controlled by the simultaneous rotation of two quarter-wave plates.

Intensity Equalization of Bidirectional Fiber Laser Based on a Non-Reciprocal Optical Attenuator

“…For example, based on the principle that the Faraday optical rotation angles of different wavelengths are different, isolators with different conduction directions for different wavelengths can be made [15][16][17][18]. Combining the Faraday rotator and quarter-wave plate, phase controllers with different phase delays in different directions can be made [19][20][21], and the Faraday optical rotation effect can also be used to make bidirectional multi-port circulators [22].…”