Abstract: A system for measuring turbine bucket temperature in a gas turbine engine includes a plurality of optical detectors, such as a pyrometer and a spectrometer, and an optical switch for selectively directing radiation from turbine engine sight glass to any one of the optical detectors along a common line of sight. The optical switch preferably includes first and second blocks, with the optical detectors being disposed in the second block. A rotor is mounted between the first and second blocks for rotation about a rotational axis, and a fiber optic cable is provided having a first end located on the rotational axis and a second end offset from the rotational axis. Rotation of the rotor selectively positions the second end of the fiber optic cable adjacent to any one of the optical detectors.