Thermal effects on the photoelastic coefficient of polymer optical fibers

Abstract

We measure the radial profile of the photoelastic coefficient C(r) in single-mode polymer optical fibers (POFs), and we determine the evolution of C(r) after annealing the fibers at temperatures from 40°C to 80°C. We demonstrate that C(r) in the fibers drawn from a preform without specific thermal pre-treatment changes and converges to values between 1.2 and 1.6×10^-12 Pa^-1 following annealing at 80°C. The annealed fibers display a smoothened radial profile of C(r) and a lowered residual birefringence. In contrast, the mean value of C(r) of the fiber drawn from a preform that has been pre-annealed remains constant after our annealing process and is significantly higher, i.e., 4×10^-12 Pa^-1. The annealing process decreases the residual birefringence to a lower extent as well. These measurements indicate the impact of annealing on the thermal stability of the photoelastic coefficient of POFs, which is an essential characteristic in view of developing POF-based thermo-mechanical sensors.

Fast Bragg Grating Inscription in PMMA Polymer Optical Fibres: Impact of Thermal Pre-Treatment of Preforms

“…The obtained temperature sensitivities were similar to the values already reported for POFBGs inscribed in Fibre 1 with 325 nm laser system [26]: −74 ± 3.3 pm/°C. For Fibre 2, we achieved a temperature sensitivity of −53.1 ± 2.2 pm/°C, which is less than the value achieved for Fibre 1, as discussed in [25], suggesting that these POFs are much less sensitive to thermal treatment due to the impact of preform thermal pre-treatment before the PMMA POFs drawing.…”

“…We shall recall that the preform from each drawing process of Fibre 2 has been annealed for 2 weeks at 80 °C, giving a well-defined thermal pre-treatment when compared with Fibre 1. The effect of annealing on a POF in which the preform has been annealed prior to drawing is different as reported and discussed recently in [25], where this fibre type is far less sensitive to thermal treatment.…”

“…With this, we noticed that the strain and temperature sensitivities of Fibre 2 are not at all affected by the fibre annealing process before FBG inscription. Recall that the preform of this fibre has been annealed for 2 weeks at 80 °C in both two-step process and as reported in [25], this well-defined annealing of the preform plays a key role for the development of stable POFBG sensors, improving at the same time the inscription time of FBGs. …”

Thermal Profile Detection Through High-Sensitivity Fiber Optic Chirped Bragg Grating on Microstructured PMMA Fiber

“…This value is similar to sensitivity achieved in [32] equal to -180.0 pm/ • C. This obtained sensitivity value has been used in the following experiments, in the CMT model for spectral reconstruction. The small errors in calibration can be explained by not uniform heat distribution in the water bath, heat absorption effect, accuracy of the thermometer, and to a non-linear thermal coefficient of the PMMA fiber [33]. The sensitivity observed for this grating is similar to previously reported POF gratings operating in near-infrared [26], [27] and much larger than cyclo-olefin copolymer [34] that has lesser sensitivity to humidity.…”

Modeling and Analysis of the Influence of an Edge Filter on the Combining Efficiency and Beam Quality of a 10-kW-Class Spectral Beam-Combining System

“…Benefiting from the development of large-mode-area (LMA) fibers and high-brightness semiconductor-based pump sources, the range of the output power achieved by the fiber lasers has been obviously improved [2][3][4]. Unfortunately, as they are limited by stimulated Brillouin scattering and undesirable thermo-optics, it is difficult to scale up the output power of a single fiber laser to higher power levels, and this would hardly meet the increasing demands of modern and technologically advanced industries [5][6][7][8][9].…”