MEASURING PHASE NOISE OF NARROW-BAND LASER BASED ON THE MACH-ZEHNDER INTERFEROMETER CONSISTING OF THE RM-FIBER Russian patent published in 2018 - IPC G01R29/26 

FIELD: measuring equipment.

SUBSTANCE: invention relates to devices for measuring phase noise by the frequency discriminator method, which is a Mach-Zehnder interferometer, and can be used for attestation of narrow-band, highly stable lasers used in communication lines, hydrophones, lidar systems, and phase-sensitive reflectometry. Phase noise meter of narrow-band lasers includes: an optical coupler forming two channels: the first, recording the instantaneous values of the power of the source, and the second, recording two interference signals; a polarizer in the second channel, which forms linearly polarized radiation at the entrance to an unbalanced Mach-Zehnder fiber interferometer, made of a fiber optic splitter coupler (1×2) on the basis of a fiber with preservation of the polarization state at the input of the interferometer, additional fiber with preservation of the polarization state introducing the phase difference, and a combining fiber-optic coupler (2×1) on the basis of fiber with preservation of the polarization state at the output of the interferometer; located after the Mach-Zehnder interferometer, a polarizing beam splitter separating two interference signals from orthogonally polarized waves; three receivers of optical radiation, two of which are located after the polarizing beam splitter in the second channel, and one – in the first channel; an analog-to-digital converter that receives signals from all three receivers, and thereafter a digital signal processing unit for calculating the spectral power density of the phase noise by performing the functions in the following order: normalization of the interference signal to instantaneous values of the signal proportional to the laser power, in order to compensate for the relative noise of the laser intensity; high-frequency filtering to compensate for temperature instability; calculation of phase fluctuations and calculation of the spectral power density of phase noise.

EFFECT: minimization of the error in measuring the phase noise of a narrow-band laser.

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