| 摘要 |
PROBLEM TO BE SOLVED: To maintain a resonance mode which can stably exist in an optical path to be monitored to automatically measure a breaking point in the optical path with high accuracy.SOLUTION: An optical path monitoring device includes: a semiconductor laser 1; a polarization controller 2 which controls a polarization state of output light of the semiconductor laser; a first photoelectric transducer 5 which converts propagation light of an optical path into an electric signal; an operation part 8 which detects spectrum intensity in an arbitrary frequency section of a frequency spectrum of the electric signal obtained by the first photoelectric transducer, determines whether or not the spectrum intensity becomes predetermined spectrum intensity showing that the polarization state is the optimal polarization state, and generates a control signal based on the result; and a polarization controller driving part 10 which performs drive control of the polarization controller based on the control signal generated by the operation part to vary the polarization state of the output light of the semiconductor laser. The operation part calculates a position of a breaking point based on a spectrum interval of the calculated frequency spectrum when it is determined that the spectrum intensity becomes the predetermined spectrum intensity. |
