| 摘要 |
PURPOSE:To detect the mode variation by a miniature and inexpensive device of a simple constitution by converting a mode variation to an intensity variation by a multi-mode fiber, a mode scrambler and a star coupler. CONSTITUTION:A light beam 19 which is emitted from a semiconductor laser 1 is made incident on an isolator 2, propagated in a multi-mode through the inside of a multi-mode fiber 3, a higher order mode is eliminated by a mode scrambler 4, and several fundamental modes are selected. Subsequently, said light beam is further allowed to branch by a star coupler 5, and its output is detected by a photodetector 6. In such a state, for instance, when the wavelength of the laser 1 is fluctuated, a propagation mode excited in the fiber 3 is varied, and a mode propagation loss in the scrambler 4 and a branching ratio in the star coupler 5 are varied, therefore, a variation of the light intensity can be detected by the detector 6. |
