Elimination of polarization effect in a fiber-optic gyro by using polarization elements

Abstract

This paper proposes the theoretical design of a polarized interferometric fiber-optic gyroscope (IFOG). The polarized IFOG utilizes a coherent light source and polarization elements (Faraday rotators and polarizing beam splitter) to obtain maximum visibility of an interference signal and to compensate for the birefringent effect of a single-mode fiber coil in an IFOG.

Appendix

The intensity signal in previous method (Lin and Yu 2014) and the proposed method are respectively expressed as

$$ I_{sig1} = \frac{{I_{0} }}{16}\sin^{2} \theta \left[ {1 + \cos \left( {\omega t + \varphi_{sag} } \right)} \right], $$

(34)

$$ I_{sig2} = \frac{{I_{0} }}{2}\left( {\sin^{2} \theta \cos^{2} \frac{\varphi }{2} + \cos^{2} \theta \sin^{2} \frac{\xi }{2}} \right)\left[ {1 - \cos \left( {\varphi_{sag} + \varGamma } \right)} \right]. $$

(35)

Recall that I₀ in Eqs. (34) and (35) is the intensity of the incident beam. The transmittance is defined as

$$ T_{n} = \frac{{\hbox{max} \left( {I_{\text{sign}} } \right)}}{{I_{0} }},\quad n = 1,2. $$

(36)

where $\hbox{max} \left( {I_{sign} } \right)$ is the maximum intensity signal that the system can be operated under an optimum condition, and the subscript n = 1 and 2 indicates the method in reference (Lin and Yu 2014) and the proposed method, respectively. In Eq. (34), the maximum intensity signal is obtained for the birefringent parameter of an SMF $\theta = 0$ and interference term $\cos \left( {\omega t + \varphi_{sag} } \right) = 1$. Under this condition, the transmittance is equal to $T_{1} = {1 /8}$. In Eq. (35), the maximum intensity signal occurs at the birefringent parameters of an SMF, $\varphi = 0{\text{ or 2}}\pi$ and $\xi = \pm \pi$, and interference term $\cos \left( {\varphi_{sag} + \varGamma } \right) = - 1$, in this condition, the transmittance is equal to $T_{2} = 1$.