SIGNAL PROCESSING METHOD IN PHASE OTDR
A signal processing device and a signal processing method of the present disclosure are a signal processing device and a signal processing method for performing signal processing of measurement data of scattered light, which is brought by scattering of a plurality of light pulses having different optical frequencies, in an optical fiber, and include calculating a scattered light vector r i with each of the optical frequencies of scattered light, falling within a predetermined time range in which measurement is allowed at any point of the optical fiber, averaging scattered light vectors r i with each of the optical frequencies in terms of the time range, calculating a rotation angle α i for correcting a phase with each of the optical frequencies using a time average vector r i_avet obtained by the averaging, and correcting the phase of the scattered light vector r i with each of the optical frequencies by rotating the phase of the scattered light vector r i of each of the optical frequencies by the rotation angle α i .
1 . A signal processing device configured to:
acquire measurement data of scattered light, which is brought by scattering of a plurality of light pulses having different optical frequencies, in an optical fiber;
calculate a scattered light vector r i with each of the optical frequencies of scattered light, falling within a predetermined time range in which measurement is allowed at any point of the optical fiber;
average scattered light vectors r i with each of the optical frequencies in terms of the time range;
calculate a rotation angle α i for correcting a phase with each of the optical frequencies using a time average vector r i_avet obtained by the averaging; and
correct the phase of the scattered light vector r i with each of the optical frequencies by rotating the phase of the scattered light vector r i with each of the optical frequencies by the rotation angle α i .
2 . The signal processing device according to claim 1 ,
wherein the time range is a time range of one discretional block out of a plurality of blocks into which an acquisition time of measurement data is divided, and
the signal processing device is configured to correct the phase of the scattered light vector r i with each of the optical frequencies, per block.
3 . The signal processing device according to claim 2 configured to
correct the phase of the scattered light vector r i using the calculated rotation angle α i falling into a previous block.
4 . The signal processing device according to claim 1 comprising:
an AD conversion function element configured to individually convert an in-phase component and a quadrature component of scattered light into digital signals;
an optical frequency separation unit configured to separate an in-phase component I digital and a quadrature component Q digital of the digital signals output from the AD conversion function element into a signal I i and a signal Q i with each of the optical frequencies;
a rotation angle calculation unit configured to calculate the scattered light vector r i using the signal I i and the signal Q i output from the optical frequency separation unit, average the calculated scattered light vectors r i in terms of the time range, and calculate the rotation angle α i using the time average vector r i_avet obtained by the averaging; and
a phase correction unit configured to correct the phase of the scattered light vector r i , calculated by the rotation angle calculation unit, using the rotation angle α i calculated by the rotation angle calculation unit,
wherein processing in the AD conversion function element, the optical frequency separation unit, and the rotation angle calculation unit are executable independently and in parallel.
5 . The signal processing device according to claim 1 configured to:
frequency-average vectors R i obtained by rotation by the rotation angle α i ,
calculate an angle θ avef of a frequency average vector R avef after frequency-averaging, and
calculate a vibration waveform using the angle θ avef .
6 . A measurement system comprising:
a measurement device configured to measure scattered light, which is brought by scattering of a plurality of light pulses having different optical frequencies, in an optical fiber; and
the signal processing device according to claim 1 configured to acquire measurement data of scattered light measured by the measurement device, calculate a scattered light vector r i of scattered light at a discretional point of the optical fiber, and calculate a phase change of the calculated scattered light vector r i .
7 . A signal processing method for performing signal processing of measurement data of scattered light, which is brought by scattering of a plurality of light pulses having different optical frequencies, in an optical fiber, the signal processing method comprising:
calculating a scattered light vector r i with each of the optical frequencies of scattered light, falling within a predetermined time range in which measurement is allowed at any point of the optical fiber;
averaging scattered light vectors r i with each of the optical frequencies in terms of the time range;
calculating a rotation angle α i for correcting a phase with each of the optical frequencies using a time average vector r i_avet obtained by the averaging; and
correcting the phase of the scattered light vector r i with each of the optical frequencies by rotating the phase of the scattered light vector r i with each of the optical frequencies by the rotation angle α i .