Patent ID: 7649619

Claim:
An optical time domain reflectometer (OTDR) comprising: a pulse light source which emits a light pulse to one end side of an optical fiber as a target object to be tested; an optical receiver which receives the light returning to the one end side of the optical fiber in response to the emitted optical pulse; an A/D converter which receives a signal from the optical receiver and converts the signal into an N+A bit digital signal so as to output the digital signal, the N being a predetermined number of bit(s) to be finally obtained and the A being a predetermined additional number of bit(s) and the A being an integer greater than “0”; data compression means for compressing the N+A bit digital signal output from the A/D converter to N bit data; and a controller which implements a process for the digital signal compressed to the N bit data so as to measure transmission characteristics of the optical fiber as the target object to be tested, wherein the A/D converter is a pipeline A/D converter, and the data compression means outputs, of the N+A bit digital signal output from the A/D converter, an arbitrary series of N bit data, when there is no bit of “1” in higher-order bits than a most significant bit of the arbitrary series of N bit data, and outputs N bit data all of whose bits are “1”, when there is at least one bit of “1” in the higher-order bits.