Abstract: A high resolution optical fault locator for single mode applications uses a high power, short wavelength laser for generating narrow optical pulses that are launched into a single mode fiber under test. The laser output is coupled to a multimode coupler whose output is coupled to a multimode output fiber. The multimode output fiber is fusion spliced with a single mode fiber, which is coupled to a front panel connector for connecting the fiber under test to the fault locator. An optical detector that is compatible with the output laser is coupled to the multimode coupler to receive the reflected light from the fiber under test. The high resolution fault locator is useful in examining single mode local area networks where many closely spaced fiber connections exist.