Curvature and Vibration Sensing Based on Core Diameter Mismatch Structures

Abstract

Core diameter mismatch structures are proposed and experimentally investigated for curvature and vibration sensing. Two configurations are suggested, one approach uses a structure formed by splicing an uncoated short section of multimode fiber between two standard single-mode fibers (SMFs) single-mode-multimode-single-mode (SMS), combined to a fiber optical mirror at its end, and the other approach uses a structure made by splicing a section of SMF between two multimode fibers (SMSMS). In the curvature analysis, the proposed SMS sensor generates the destructive interference patterns when it is bent, varying only the attenuation of the optical signal without wavelength shifts. The SMSMS vibration sensor proved to be suitable to monitor very low frequencies such as 0.1 Hz. The configuration of the proposed sensors presents several interesting features, such as easy fabrication, low cost, high efficiency, and high sensitivity. These advantages make such sensors very useful in a wide range of applications, for instance, structural health monitoring.

Strain sensing based on a core diameter mismatch structure

“…Therefore, to interrogate this sensor, it is not needed a complex and expensive equipment. For the proposed sensor, a temperature compensation technique is not required, as well, since its sensitivity to temperature is around ‑0.015 dB/ o C …”

“…Therefore, to interrogate this sensor, it is not needed a complex and expensive equipment. For the proposed sensor, a temperature compensation technique is not required, as well, since its sensitivity to temperature is around -0.015 dB/ o C. 32 The sensor used a simple optical power meter interrogation system. The results of the applied loads (from ε ≈ 20 με to ε ≈ 200 με) to the SMS sensor showed linear behavior with slopes of ≈0.0014 dB/με.…”

“…This coupling is not wavelength selective, that is, it is independent in terms of the wavelength. Thus, the proposed SMS strain sensor does not behave as a common MMI and simply presents a variation in the optical power, which turns it attractive for many applications . As the sensing structure is subjected to a load, the sensor structure coupling coefficient is varied, changing the optical power of the transmitted signal.…”

“…This work proposes an SMS fiber strain sensor and a simple power meter‐based interrogation technique, since only the optical power changes as strain is applied in this sensor. The SMS sensor has already been described for vibration and curvature measurements . The viability of this sensor is expanded to evaluate strain.…”

“…The SMS sensor has already been described for vibration and curvature measurements. 32 The viability of this sensor is expanded to evaluate strain. The proposed experimental scheme uses information from optical power change to measure the SMS fiber strain sensor response.…”