Monoflow Measurement with Polarization Controlled Effect in SMS and SMSMS Optical Fiber Sensors

This paper describes an experimental analysis of optical fiber sensors based on multimodal interference phenomenon using the core diameter mismatch technique, acting as a Mach-Zehnder interferometer. The sensor is composed of single-mode and multimode fibers that are spliced together and is used to measure monoflow fluids in pipeline systems. The research presents a comparison of two different sensors, one singlemode-multimode-singlemode (SMS) fibers structure and another singlemode-multimode-singlemode-multimode-singlemode (SMSMS) fibers structure applied to measure water flow, and there is also the control of the polarization effect in the sensing environment. The obtained results showed that the sensitivities values are affected by the influence of the polarizer device along the sensors path, with significant increase in the sensitivity from -2.206 dB.h/m(3) to 0.782 dB.h/m(3) with acceptable good linearity of 0.98 and 0.97 for the SMS sensor; for the SMSMS sensor, the sensitivity values changed from 0.862 dB.h/m(3) to 1.122 dB.h/m(3), with R-2 = 0.99. The behavior and results proved that the use of a polarizer device keeps the polarization mode by inducing a uniform birefringence along the entire fiber and sensor which maintains and controls the optical power, thereby preventing random power coupling between polarization modes.