Temperature and strain sensing utilizing fluorescence in erbium doped photonic crystal fiber

Abstract

This thesis reports a research on the development of erbium-doped photonics crystal fiber (PCF) for simultaneous strain and temperature measurement. Particular focus is given to overcome the existing issue in conventional optical fiber sensor constructed with single mode fiber (SMF) which is dependent on the surrounding temperature. This behavior apparently will result in the incapability of distinguishing strain and temperature measurement. A new sensing scheme is proposed as an alternative technique that allows discrimination of strain and temperature measurement by utilizing the fluorescence of erbium-doped PCF. The erbium-doped PCF structure is modeled and simulated using COMSOL Multiphysics software to determine the main characteristics of the PCF in terms of the effective refractive index and confinement loss. The erbium-doped PCF sensor is developed based on a manual splicing recipe which consists of a short fusion time of 0.4 s, low power electric arc of 70 a.u, gap between PCF and SMF of 14.2 ^m and an axial offset position of 12.1 ^m. The proposed sensor scheme is developed based on two different interrogations which are the intensity-based interrogation and combination of intensity and wavelength-based incorporating FBG interrogation. Fluorescence ratio techniques are studied over a temperature range of 30-150 °C while the intensity/wavelength changes are studied over a strain range of 200-850 ^e. Both interrogations results are analyzed using matrix method for strain-temperature de-convolution. Intensity and wavelength-based interrogation shows further significant improvement in average temperature error of 0.0087 °C and average strain error of -14.7402 as compared to the conventional erbium-doped fiber. Thus, this sensor is capable of measuring a range of parameters and has potential in implementing discriminative strain and temperature sensing systems in the future.