Abstract: A fiber optic multiplexer comprises a stationary frame to which primary and secondary optical fibers are attached, a rotary frame to which both ends of a transfer optical fiber are attached, and a means of rotating the rotary frame through a predetermined angle relative to the stationary frame. The primary end of the transfer optical fiber is coaxial with the primary optical fiber and the rotary frame axis of rotation. The secondary end of the transfer optical fiber is initially coaxial with a first secondary optical fiber. The multiplexer is switched by rotating the rotary frame through the predetermined angle to coaxially align the secondary end of the transfer optical fiber with a second secondary optical fiber.