## 1 Introduction  
A digital and intelligent substation is the key part of the new generation power network for improving the voltage level of a high voltage power system, for which the photoelectric sensor is now expected (as a highly precise and safe detection technology) to be a prospective candidate for monitoring high voltage and large current. The photoelectric current sensors are mainly classified into optical glass current sensor, photoelectric hybrid current sensor and full fiber current sensor. The optical glass current sensor uses an optical glass bulk material with high Verdet constant as the detection probe, the sensitivity of which is apt to be affected by ambient temperature and mechanical vibration. For a full fiber current sensor, the optical fiber body is cooperatively exploited as the detecting element so that the sensitivity is also simultaneously influenced by ambient temperature, fiber birefringence and incident polarization. Inheriting from the traditional current sensor,the sensor head is completely composed of electronic circuits and a power supply in the photoelectric hybrid current sensor with an optical fiber as the signal transmission channel. The fiber Bragg grating (FBG) sensor is a passive high-sensitivity device with high electrical insulation, strong resistance to electromagnetic interference, small size and mass, heat and corrosion resistance [1]. Especially, the wavelength modulation of an FBG is utilized for indirectly measuring physical quantities to realize complete electrical isolation in live detection [2]. Giant magnetostrictive material (GMM) represents the sensing and driving functions of conversion between electromagnetic and mechanical energies in high energetic density and coupling coefficients [3; 4; 5]. Therefore, the combination of FBG and GMM constituting sensors is a preferable scheme for the online detection of strong electromagnetic equipment with a broad prospective applications in power systems. The GMM-FBG system for sensing electrical current has been extensively considered ever since it was proposed in the end of last century by a fiber-optic M-Z magnetic field sensor with a nickel coating as the magnetic conductive material to achieve successful current measurements [6; 7; 8]. The GMM-FBG demodulated with a linear edge filter shows a good linearity for detecting a 250-700 A alternative current of 60 Hz frequency [9]. The GMM-FBG sensing system has been applied to high-voltage transmission in simulation tests and achieved consistent results with theoretically predicted values [10]. It was found by means of a spectrum analyzer that the magnetostrictive caused by a DC current can be exploited to regulate the central wavelength of an FBG [11; 12; 13]. A geometrically optimized structure of the GMM-FBG current sensor has acquired the maximum input current of 186 A and a global accuracy of 4.3% in the linear working region without any harmonic output signal [14]. Temperature drift poses a significant challenge in optical fiber current sensors, where precise measurements are vital for applications in high-voltage power systems and plasma current monitoring. The integration of giant magnetostrictive material (GMM) with fiber Bragg grating (FBG) sensing principles offers promise for high-current detection but requires a thorough understanding of temperature drift characteristics to ensure accuracy and reliability. Recent researchers have explored innovative solutions, including a temperature-compensated method using FBG-GMM sensors and simultaneous temperature and Faraday rotation extraction in polarimetric fiber-optic sensors [15; 16]. Additionally, performance assessments of fiber-optic current sensors have underscored the importance of addressing mechanical perturbations and optimizing sensor reliability [17]. In particular, [PERSON] et al. presented a mathematical model of temperature compensation for a GMM-FBG current sensing system, leading to a significant improvement in the accuracy of measuring 60 A current at 40 \({}^{\circ}\)C [18].