Optical Current and Magnetic Field Sensor Using Multimodal Interference in Fiber Optics With Carbon Steel

This work proposes an experimental configuration for a magnetic field and electric current sensor using an optical fiber in a single-mode-multimode (SM-MM) structure. The method applied is based on multimodal interference effects, where the MM fiber was coated with carbon steel. A continuous-wave laser with a 1550 nm wavelength was used to feed the sensor. The signal at the MM fiber output is captured by a photodiode in order to measure the signal in terms of voltage using a digital multimeter. The alternating magnetic field causes the carbon steel coated optical fiber to oscillate, changing its light propagation characteristics and therefore the output of the transmitted light. An increase in the signal was observed at the sensor output with increases in the magnetic field. The sensitivity of the sensor was tested by placing the coil at 2 cm and 4 cm from the fiber, reaching values of 78.13 mV/mT and 79.80 mV/mT, respectively. The relationship between the optical transmission variation and the magnetic field intensity reached a linearity of 98.297%. Notably, the method proposed in this experiment is less complex than most state-of-the-art methods. Furthermore, it presents excellent characteristics of cost, compactness and structure, with potential applications for the measurement of alternating magnetic fields and electric currents.