Measurement of displacement in the micrometer range using speckle pattern correlation in multimode fibers

Abstract

The displacement measurement in the micrometer range using the speckle pattern correlation in optical fibers is described. The high sensitivity of a multimode fiber when propagating a coherent light causes any variation in the distribution of the speckle pattern is proportional to the disturbance which it originates. The speckle pattern is caused by interference between modes and the shift mechanism is due to coupling between modes and micro-induced redistribution curvature applied to the fiber externally. The movement is produced by a transducer containing microbends pressure induced on the fiber. Experimental results are presented using three types of multimode plastic optical fiber. In the signal generated from the change in the speckle pattern observed with relatively good reproducibility, so that sensor systems could be used.