Polarization effects in polymer FBGs: study and use for transverse force sensing

Abstract

Bragg gratings photo-inscribed in polymer optical fibers (POFs) are more sensitive to temperature and pressure than their silica counterparts, because of their larger thermo-optic coefficient and smaller Young's modulus. Polymer optical fiber Bragg gratings (POFBGs) are most often photo-written in poly(methylmethacrylate) (PMMA) based materials using a continuous-wave 325 nm HeCd laser. In this work, we present the first study about birefringence effects in POFBGs manufactured in different types of fiber. To achieve this, highly reflective (> 90%) gratings were produced with the phase mask technique. Their spectral response was then monitored in transmission with polarized light. Polarization dependent loss (PDL) and differential group delay (DGD) were computed from the Jones matrix eigenanalysis using an optical vector analyzer. Maximum values exceeding several dB and a few picoseconds were obtained for the PDL and DGD, respectively. An inverse scattering technique applied to the experimental data provided an estimate of the photo-induced birefringence value arising from the side fabrication process. The response to lateral force was finally investigated for various incident directions using the PDL response of FBGs manufactured in step-index POFs. As the force induced birefringence adds to the photo-induced one, a force dependent evolution of the PDL maximum value was noticed, with a good temperatureinsensitivity.

Fast and stable gratings inscription in POFs made of different materials with pulsed 248 nm KrF laser

“…Although optical fiber sensors are commonly made of silica fibers, advances in polymer processing [2], characterization [3] and fiber Bragg grating (FBG) inscription [4] enable the application of polymer optical fibers (POFs) in sensing applications. POFs present additional advantages when compared with their silica counterparts, which include flexibility in bending, higher fracture toughness, and lower Young Modulus that provides higher sensitivity in strain sensing applications [5].…”

Polymer optical fiber sensors in human life safety

“…Advantages such as higher flexibility in bending, biocompatibility [2], higher failure strain [3], higher fracture toughness, and lower production cost, are significant for many sensing applications. The lower Young's modulus of POF [4] provides enhanced sensitivity to POF sensors when are used for strain [5], stress and force [6], pressure [7], and acoustic wave detection [8]. There are also some hydrophilic polymeric materials such as poly (methyl methacrylate) (PMMA) that can absorb water, enable them for humidity detection applications [9].…”

Design and Testing of a 2D Optical Fiber Sensor for Building Tilt Monitoring Based on Fiber Bragg Gratings

“…Not only silica optical fiber sensors but also polymer optical fibers (POF) sensors are widely used in different sensing applications. Several fiber sensor designs based on FBG have been reported for various applications, such as liquid level monitoring [13], transverse force sensing [14], concentration measurement [15], biomedical measurement [16,17], pressure [18][19][20], displacement [21,22], temperature [23,24], and ground vibration [25]. An FBG is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others.…”