Optical fiber characteristic measuring device

An optical fiber characteristic measuring device for measuring characteristics of an optical fiber, comprising:

• a coherent light source for emitting coherent light having a narrow spectral linewidth;
• a first optical directional coupler for sending said coherent light to a main route while splitting off a portion to send to a subsidiary route;
• a second optical directional coupler for sending coherent light exiting said subsidiary route of said first optical directional coupler to said main route while splitting off a portion to send from said subsidiary route to a first end surface of an optical fiber;
• an optical frequency converter for repeatedly changing the optical frequency of the coherent light exiting said main route of said first optical directional coupler in steps of a designated frequency at a designated periodicity;
• pulsing means for pulsing an optical signal having a desired wavelength among optical signals outputted by said optical frequency converter and outputting the pulsed optical signal;
• a third optical directional coupler for sending said pulsed optical signal outputted by said pulsing means from said main route to a second end surface of said optical fiber, while sending an signal light exiting said second end surface, or back-scattered signal light, to said subsidiary route;
• and
• a light receiving circuit for coherently receiving signal light exiting said subsidiary route of said third optical directional coupler and coherent light exiting said main route of said second optical directional coupler, then processing the received signals to measure characteristics of said optical fiber.