Patent US 5,488,600

An optical information storage apparatus includes a differential type optical switch element, and an optical fiber. The optical switch element shifts from a non-emission state to an emission state upon reception of an optical input. The optical fiber constitutes a first optical path. The optical fiber receives an optical output emitted from the optical switch element through at least one end face, guides the optical output, and causes an output beam to be incident, as the optical input, onto the optical switch element.