Patent ID: 8913235

Claim:
A fiber measurement device, comprising: a light detector adapted to detect feedback light of laser light output to a fiber from the fiber, and convert the feedback light into an electrical signal; a narrowband measuring circuit; a wideband measuring circuit adapted to amplify the feedback light from the fiber, and measure characteristics of the fiber based on loss of the feedback light; and a switch adapted to switch between the narrowband measuring circuit and the wideband measuring circuit to input the electrical signal from the light detector, wherein the narrowband measuring circuit includes: a band limiting circuit adapted to extract, from the electrical signal from the light detector, a signal having a component corresponding to a frequency of the laser light, wherein the signal extracted by the band limiting circuit is a first differentiation target signal; and a waveform equalizing circuit comprising a differentiating and adding circuit, including a first differentiating circuit and adding circuit, wherein the first differentiating circuit is adapted to calculate the differential of the first differentiation target signal from the band limiting circuit to generate a first differentiation result signal, and the adding circuit is adapted to add the first differentiation target signal and the first differentiation result signal generated in the first differentiating circuit together.