Effects Of The Linear Birefringence And Its Wavelength Accumulation Upon An Optical Glass Current Sensor

Linear birefringence (LB) is one of the prominent parameters limiting the practical applications of optical current sensors (OCSs). Two formulae describing the relation between the LB and the output of the Faraday mirror-typed OCS and that of the reflection-typed OCS are derived, respectively. Furthermore, the two formulae are compared with that of the OCS with polarization-preserving total reflection layers. The results show that, when the polarizing angle of the input light beam is 0°,45°,90°..., compared with the unidirectional sensing plan of the OCS with polarization-preserving total reflection layers on hand, the bidirectional sensing plan of the Faraday mirror-typed OCS will rise the system sensitivity with respect to 2 times, in the premise of not increasing the effects of the LB; while the bidirectional sensing plan of the reflection-typed OCS will increase the effects of the LB along with the rising of the system sensitivity. It can be seen from these results that the bidirectional sensing plans can influent the system sensitivity to some extent, but cannot restrain the effects of the LB thoroughly. These results provide an important theoretical reference to the colleagues who are thinking of restraining the effects of the LB further by improving the design of the sensing head.Considering the LB is the function of the wavelength and has dispersion features, there will be wavelength accumulation effects in the systems employing broadband optical sources. The dispersion formula for the LB inside the ZF-7 glass is given first, and then, its wavelength accumulation effects upon an OCS are theoretically analyzed and digitally simulated. The results show that the wavelength accumulation effect of the LB inside the ZF-7 glass is less enough and the treatment of using monochromatic model to describe the broadband OCS system is reasonable and feasible, if the wavelength accumulation effects of the other optical parameters of the sensing head are not considered.These results not only supply an important reference to the further studying of the OCSs, especially to the studying of improving the sensing head to restrain the LB, but also a theoretical guide to the design of the sensing head.