| 摘要 |
PROBLEM TO BE SOLVED: To reduce influences of a linearity error of an AD converter, in a temperature distribution measuring instrument.SOLUTION: A temperature distribution measuring instrument comprises a light source which emits a light pulse to an optical fiber, a light-receiving section which receives Raman scattered light from the optical fiber and converts the received light into an electric signal, an offset voltage generating section which generates an offset voltage to be added to the electric signal, an AD converter which converts an analog signal corresponding to the electric signal to which the offset voltage has been added into a digital signal, an averaging circuit which averages a plurality of digital signals converted by the AD converter, and a computing section which computes a temperature distribution of the optical fiber on the basis of the averaged signal. In the temperature distribution measuring instrument, the light pulses emitted by the light source form a light pulse train including N kinds of code strings as one unit, the N kinds of code strings being code-modulated by using Golay codes, and the offset voltage generating section changes the offset voltage synchronously to the unit of the code string. |
