High resolution polarization-independent high-birefringence fiber loop mirror sensor

Abstract

In this work, two all polarization-maintaining (PM) high-birefringence (Hi-Bi) fiber loop mirrors (FLM) which are immune to external polarization perturbations are validated both theoretically and experimentally. Simplified and stable versions of classical FLMs were attained using a PM-coupler and by fusing the different Hi-Bi fiber sections with an adequate rotation angle between them. Since the polarization states are fixed along the whole fiber loop, no polarization controllers are needed. This simplifies the operation and increases the stability of the systems, which were also validated as ultra-high resolution sensors, experimentally obtaining a resolution of 6.2∙10^-4 °C without averaging.

Truly remote fiber optic sensor networks

“…This sensor was formed by two sections of Panda fiber, which were fused together with a 90°rotation angle and connected to a polarization maintainer coupler. The 90°angle fusion between the sections of Panda fiber eliminated the requirement of a polarization controller, as it was previously demonstrated in [157]. The obtained results validated this system to monitor in real time the strain applied to the interferometric sensor located 225 km away from the monitoring station.…”

High Sensitivity Fiber-optic Liquid Level Sensor Using Biconical Tapered Fibers

“…That change is generally small and almost indiscernible in a single period of the optical spectrum. It is then necessary to compare the accumulative variation in a high number of periods [8]. However this is not straightforward if the interference consists of several frequency components, as in this work.…”

All-PM Fiber Loop Mirror Interferometer Analysis and Simultaneous Measurement of Temperature and Mechanical Vibration

“…In that case, a method based on the fast Fourier transform (FFT) can be employed to identify each particular component in the spatial-frequency domain that contributes to the interference formation [5]. The FFT interrogation-based technique has been used to multiplex in a single network different interferometric sensors, such as cascaded chirped long period gratings [6], microfiber knot resonators [7], inline photonic crystal fiber (PCF) sensors [8], Fizeau strain sensors [9], graded-index multimode fiber Fabry-Pérot cavities [10], HiBi FLMs [11] and also multiple HiBi sensing fibers in a compound fiber loop mirror [11][12][13]. Additionally, this method provides more than 100 times greater resolution by monitoring the phase of the FFT instead of the spectral shift of a single fringe in the optical spectrum (the conventional solution) [13].…”

“…Firstly, the maximum number of HiBi FLM sensors that can be multiplexed in a single network is reduced. Up to date, only a few investigations have addressed this aspect [11][12][13][14][15]. The second practical limitation is related with the use of single-mode fiber (SMF) to interconnect the HiBi fiber in the loop; since a SMF optical coupler is typically employed in the conventional version of the HiBi FLM.…”

“…Consequently, a polarization controller (PC) is required to set the angle difference of the light at the ports of the optical coupler. Furthermore, this effect might become particularly bothersome in multiplexing networks, because one PC per sensing element has to be adjusted [11,13].…”