In order to move signal detecting point to the most sensitive position and improve the immunity of the system at the
same time, the scheme named passively demodulated all optical fiber current transformer (AOFCT) inserts a Faraday
rotator of 22.5° rotation angle between fiber λ/4retarder and leading fiber. To improve the performance of this type of all fiber current transformer, after considering the temperature features of a large proportion of Faraday crystals, the
effect of the Faraday rotator’s temperature properties on temperature stability of the passively demodulated AOFCTs are
theoretically analyzed and numerically calculated. The results show that the errors induced by the Faraday rotators are
beyond the requested values in the International Standard IEC 60044-8:2002 of International Electrotechnical
Commission (IEC) and the State Standard of P.R.China GB/T 20840.8-2007. Finally, to solve this problem, some
possible solutions are suggested.