International Journal of Advanced Research in Computer Engineering & Technology (IJARCET) Volume 7, Issue 9, September 2018, ISSN: 2278 – 1323 www.ijarcet.org 722 Abstract— Magnetic field was been studied through so many processes from decades. In this paper, we have aimed to report about the magnetic fluid to fill into the cavity tube based on Fabre-Perot interferometer to find the magnetic field. The magnetic fluid is filled into the cavity tube by using the syringe injection. This magnetic fluid sensor has the properties to detect the weak magnetic field. When an external magnetic field is applied on this sensor’ the refractive index would be changed accordingly. By the outcome of experiment, the result illustrates the magnetic field sensitivity with the ratio percentage of 0.00113nm/Gs, where the filling cavity tube has 0.3 mm in size and BBL method has range of 1520 nm to 1610 nm. The sensor has the advantage of simple structure, compact size and easy fabrication. Index Terms— Optical fiber Coupler; magnetic fluid; cavity tube sensor; Fabre-Perot interferometer; magnetic field. I. INTRODUCTION The measurement of the magnetic field is of great importance in many applications, such as military, industrial, health, and energy (1). Special emphasis in the electric power field where new technologies capable to characterize in real time the energy flow in the grid are needed to better understand its operation and to enable the development of sustainable energy management systems (2). Fiber magnetic field sensors have been proposed for over 30 years (3) and have always been widely studied because of their advantages such as lightweight, resistance to electromagnetic interference, small size and capability of remote operation (4). In these sensors, a magnetic functional material is an important element since it interacts with light parameters such as intensity, phase or polarization (5). In recent years, magnetic fluids (MF) as a kind of promising magneto optical (6) and Nano materials (7) have attracted extensive attention for serving as crucial sensing elements of optical fiber magnetometer due to their advantages of fiber compatibility (8), fluidity (4), and high sensitivity (9). So far, Manuscript received September 2018. Musavir Bilal. Department of Information Sciences and Technology. Yanshan University, China. [Email: musavir@stumail.ysu.edu.cn] B. Weihong. Department of Information Sciences and Technology. Yanshan University, China. [Email: bwhong@ysu.edu.cn] M.N. Sohail. Department of Information Sciences and Technology. Yanshan University, China. [Email: mn.sohail@stumail.ysu.edu.cn] M. Irshad. Department of Information Sciences and Technology. Yanshan University, China. [Email: ibrahim@stumail.ysu.edu.cn] S.M. Zaheer. Department of Information Sciences and Technology. Yanshan University, China. [Email: Zaheer.6311@gmail.com] M.M. Uba. Department of Information Sciences and Technology. Yanshan University, China. [Email: musaubamuhammad@gmail.com] various of efforts on MF-based fiber-optic magnetometers designing with different structures have been demonstrated by utilizing the excellent magneto-optical effects of MF (10), such as birefringence (11), tunable refractive index (12), tunable transmission loss (7) and so on. Among previously reported magnetometers, there were two kinds of the most popular structures, which can be categorized into MF coating based and MF filling based ones (3). The combination of magnetic fluid and the optical fiber is one important direction (6). The fiber Fabry–Pérot interferometers (13), which is widely used as a sensor for the measurements of many physical and chemical parameters is a good choice to combine with MF (14). Various structures have been employed to realize the sensing function, for example, fiber structures with up-tapered joints (11). Dai et al. reported an MF infiltrated fiber Bragg grating magnetic field sensor (15). Sagnac interferometer and Mach-Zehnder interferometer were employed to enhance the acutance of the spectra and the magnetic field sensitivity (16). In 2006, the magnetic field sensor base on magnetic fluid-filled photonic crystal fibers (17). In 2010, a hollow-core photonic crystal fiber Fabry–Pérot (13) sensor for magnetic field measurement based on magnetic fluid was proposed by Candiani et.al (18) and it adopted the coating technology and reflection mirror to increase the reflectivity of the two interfaces to enhance the power of the signal. But it was not easy to fabricate and also very expensive (19). In this paper, a fiber optic F–P magnetic field sensor (20) has proposed, based on the tunable refractive index property of MF (21), and a fiber cavity tube (16) was used to effect on the sensor. Magnetic fluid is a kind of sensitive medium (11), was filled into the cavity tube of the Fabry–Pérot (13) sensor by using the injection syringe method based on the magneto-optical characteristics of MF (22). The structure and measuring principle of the sensing system has introduced. Preliminary experiments such as the relations between wavelength and magnetic field were done. Compared with other magnetic field sensors, the sensor proposed in this letter has many features, such as simple structure, compact, easy fabrication, low cost, high sensitivity, and stability (23). The remaining part of the paper is analyzed in three parts. First part will talk about the „operations of sensor‟ (24) with properties and principles, second part will present the „proposed results of conducted experiment‟ and the last part will discuss about the „conclusion and future work‟. Magnetic fluid filled to detect the magnetic field based on Fabre-Perot cavity tube Musavir Bilal, B. Weihong, M.N. Sohail, M. Irshad, S.M. Zaheer, M.M. Uba