Fujikura Limited

Shin-ichi Nikaido

Takeshi Togura

Tetsu Takashima

Shin-ichi Niimi

A phase difference calculation method, a device ( ), and a system ( ) are disclosed. In an optical fiber ring interference sensor ( ) using a 3&times;3 optical splitting coupler ( ) and an optical splitting coupler ( ), linear sections are determined in advance, where a relationship between a phase difference &thgr; of propagation lights and an intensity Ppdn (n&equals;1, 2, 3) outputted from each photo detector ( ) becomes approximately linear. The intensity Ppdn of an interference light, between propagation lights in CW and CCW directions in an optical fiber loop ( ), having a difference non-reciprocal phase bias is measured not less than two times. A phase difference &thgr; is then calculated based on the intensity Ppdn in the linear sections.

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Chiba, Japan

Shin-ichi Nikaido