Abstract: The apparatus of this invention includes a macrobend/microbend unit which imposes first and second macrobends, and microbends between the first and second macrobends, on an optical fiber under analysis. If light is travelling in one direction on the optical fiber, the bending of the optical fiber is such that some light will escape from the core of the optical fiber at the first macrobend. A first photodetector is arranged to receive light emitted from the first macrobend, and generates a signal indicative of whether light is present at the first macrobend. If light is travelling in the optical fiber in the other direction, the second macrobend causes some light to be emitted. A second photodetector arranged to receive light from the second macrobend, generates a signal indicative of whether light is present at the second macrobend.

Abstract: During the heating of a moving wire (21) such as when the wire is being aaled, the wire is heated in such a manner that the energy applied to each successive increment of length of the wire is substantially constant. This is accomplished by causing an integral number of half cycles of alternating curent to be applied to each successive increment of length of the wire as the increments are moved from one sheave to another in an annealer (20). In one embodiment, the integral number of half cycles is achieved by adjusting the speed at which the wire is being advanced between two sheaves of the annealer in a manufacturing line. This also may be accomlished by adjusting the distance between the sheaves in an annealing leg of the annealer, or by adjusting the frequency of the applied power source.