Optical time domain reflectometer having shortened dead zone

摘要

A driver circuit 2 generates a pulse current on the basis of an electrical pulse outputted from a timing generating portion 1. A light source 3 emits a light pulse according to the pulse current. The light pulse outputted from the light source 3 goes to a delay optical fiber 9 through an optical waveguide directional coupler 4, and then goes to a measuring optical fiber 10. A delay circuit 11 delays a digital operation of a digital operating portion 7, by a time required for said light pulse to go back and forth in the delay optical fiber 9.