Abstract: A fiber-optic switch uses a single optical fiber for two-way communication with light. A switching mechanism has no electrical part and is thus appropriate for placement in an area having explosive or combustible material. The optical fiber can be cut to length in the field and can be installed without special tools or training. The fiber is held in place by a clip that is constrained to compress the fiber and grip it securely. A snap-action mirror reflects light back into the fiber in one position and does not reflect it in another position. An electronic circuit provides pulsed light and determines coincidence of sent and received pulses to discriminate against operation of the switch by ambient light or other spurious signals.