Optical fiber characteristics measuring device and optical fiber characteristics measuring method

An optical fiber characteristics measuring device comprising:

• a pulse driving circuit for supplying a pulse driving current to a laser diode;
• a first optical directional coupler for branching the light output from the laser diode into a signal light and a reference light;
• a second optical directional coupler for sending the signal light to an optical fiber to be measured and for branching a returned light from the optical fiber into a backward scattered light and the signal light;
• a third optical directional coupler for incorporating the reference light output from the first optical directional coupler and the backward scattered light output from the second optical directional coupler and coupling backward scattered light onto the reference light;
• a photoelectric transducer for converting an optical signal output from the third optical directional coupler into an electric signal and for outputting the electric signal;
• and
• a bias circuit for supplying a continuous driving current to the laser diode at all times,
• wherein the frequency of the backward scattered light is detected based on the electric signal.