The causes of FOG measurement errors also include:
a. Faraday effect. For example, the typical value of the measurement error caused by the earth’s magnetic field is l0 / 1. The use of electromagnetic shielding and the use of polarization-maintaining fiber can eliminate the distortion error of every cycle in the loop.
b. Optical Kerr effect. The optical Kerr effect is a third-order nonlinear optical effect, and the use of low-coherence light sources may be an effective solution.
c. Fresnel reflection at the end of the fiber. The method of eliminating backscattering (such as the use of low-coherent light sources such as super light-emitting diodes or pulse modulation of the light source, etc.) or the method of refractive index matching fluid can reduce Fresnel reflection.
d. The birefringence characteristic of optical fiber. Setting a polarization controller in the optical path, using diversity reception technology and polarization-maintaining fiber technology can reduce the FOG measurement error caused by the birefringence characteristics of the fiber.
e. Polarization change. It can be solved by using polarization maintaining fiber or polarization plane compensation device and depolarizer.
f. The optical path difference between the two beams. Intensity compensation can be performed, and the effect of returning light can be eliminated with an optical isolator.
g. Time-varying temperature disturbance (S1upe). The four-pole method can be used to wind the fiber coil and make compensation in the signal processing circuit.
h. Acoustic noise and vibration. Acoustic noise and vibration can cause large non-reciprocal parasitic effects, which can be overcome by symmetrically winding fiber coils and ensuring the stability of the coils.
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