Differential mode delay measuring device and method

Abstract

An object is to provide a differential mode delay measurement device and a method thereof capable of measuring a DMD with a simple configuration even when an FMF to be measured is a long distance. A differential mode delay measurement device 301 according to the present invention includes a light source 11 configured to output a coherent light beam having an optical frequency changed with a predetermined modulation period, a branching element 12 configured to bifurcate the light beam; a light incidence unit 13 configured to excite one of the light beams in a plurality of modes, cause the one of the light beams to enter one end of an optical fiber to be measured 51 that is a few-mode optical fiber, and input the other of the light beams into one end of a reference optical fiber 52 in a single mode; an image sensor 15 configured to observe an interference light beam between a measurement light beam emitted from the other end of the optical fiber to be measured 51 and a reference light beam emitted from the other end of the reference optical fiber 52; and an arithmetic unit 16 configured to detect a peak of the interference light beam appearing when the modulation period is changed, and measure a differential mode delay based on a period of the peak and an electric field distribution of the interference light beam at the peak.

Dependencies are inferred from the claim text.