The binary symmetric logic function (BSLF), because of its invariance under the permutation of its input variables, is an important class of Boolean logic functions. The diversified BSLF applications include the synthesis of a full adder and subtractor, a text comparator, a median filter, a parity checker, and various threshold elements. The classic BSLF realization uses an array of triangularly interconnected slow-speed electric contact switches. Optical switches, because of their fast switching capability, are excellent candidates for an optical BSLF (OBSLF) implementation. In this paper, various OBSLF architectures are described, together with their applications to optical digital and symbolic computing, data communication, image processing, and neural networks.