MEASUREMENT METHOD OF THE BRILLOUIN SCATTERING FREQUENCY SHIFT ON THE OPTICAL FIBER LENGTH Russian patent published in 2017 - IPC G01N21/63 G01M11/00 

FIELD: measuring equipment.

SUBSTANCE: when implementing the measuring method of the Brillouin scattering frequency shift on the optical fiber length, the continuous optical radiation of the master laser is divided into two parts. The first part is modulated by the impulse chain, then amplified and injected into the test optical fiber. The supporting optical signal of one polarization is formed from the second part, which is fed to one balanced photodetector input. The backscattering signal coming back from the tested optical fiber is fed to the other balanced photodetector input. The measurements are performed at two orthogonal polarization states of the supporting optical signal. The electric signal from the balanced photodetector output is fed to one input of the mixer, the radio-frequency signal is fed to its other input. The low-frequency beat signal is extracted from the complex signal at the mixer output and fed to the control and processing unit input, where the measurement results are stored for each step at each frequency value. Then the polarization state of one polarization supporting optical signal is changed to orthogonal and the measurements are repeated. The Brillouin scattering frequency shift is defined as the sum of the Brillouin scattering frequency shift in the optical fiber in the absence of temperature and mechanical influences and the frequency of the modulating radio frequency signal, at which the amplitudes sum value of the beat signals at the control and processing unit input, measured with two orthogonal states of the supporting signal, exceeds the specified threshold value.

EFFECT: application field expansion.

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