A hybrid opto-electronic correlator for detecting defects in optical fibers is proposed. After the light from a He-Ne laser being expanded and filtered, it is not collimated but directly passes a Fourier transform lens and illuminates a fiber to be detected and a perfect fiber as reference one at the input plane. The Fourier transform spectrum of the fiber pair is obtained at the rear focal plane of the lens, where it is sampled via a CCD array connected with a computer through a frame grabber. The computer performs filter, inverse Fourier transform and setting threshold operation on classification. Under specific conditions, the system is an equivalent of joint transform correlator with a Fourier lens of long focal length. We analyze the conditions in terms of theory and show the experiment results corresponding to optical fibers having incoordinate defects. The results indicate that the system can be used for fiber defects detection, and it has the advantages of high identification, compact configuration, easy adjustment and flexible manipulation.
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