ULTRAVIOLET-LIGHT PHOTOSENSITIVITY IN GE-DOPED SILICA FIBERS - WAVELENGTH DEPENDENCE OF THE LIGHT-INDUCED INDEX CHANGE

A novel technique is reported for detecting permanent and transient light-induced refractive-index changes (photosensitivity) in optical fibers. The index change is detected by irradiating one arm of an unbalanced Mach-Zehnder fiber interferometer with UV light, thereby changing its optical path length. From a measurement of the change in the spectral response of the Mach-Zehnder interferometer, the change in the fiber core index as a function of wavelength can be determined. The equilibrium change in the core index is found to have an almost constant value of approximately 2.3 × 10−5 over the measured wavelength range of 700 to 1400 nm. © 1990 Optical Society of America.