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A new measurement system for fault location in optical waveguide devices is presented. The system consists of a fiber-optic Mach-Zehnder and a bulk-type Michelson interferometers. The spatial resolution of the scatter distribution is <380 microm, which is limited by the averaging time. The minimum detectable backscattered power is -116 dB relative to the light power propagating in the waveguides. Preliminary experimental results using single-mode fibers <10 cm long are demonstrated.

Optical propagation losses and coupling losses in Ti-diffused strip waveguides, fabricated in y-plate and z-plate LiNbO(3), have been examined at 1.15-,microm wavelength. Propagation losses for y-plate and z-plate waveguides are ~0.5 dB/cm. Coupling losses in the y-plate and z-plate waveguides for a single-mode fiber are 2.5 and 1 dB, respectively. This difference is due to the large surface diffusion anisotropy; it is expressed by near-field pattern overlap calculations.

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Modal birefringence of highly birefringent fibers can be measured nondestructively by the elastooptic modulation method. Based on this modulation method, a new method for precisely measuring the wavelength dependence of modal birefringence in highly birefringent fibers is presented using an incoherent light source such as a fiber Raman laser.