We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

Fiber grating sensors

Review of the present status of optical fiber sensors

In-fibre Bragg grating (FBG) sensors are one of the most exciting developments in the field of optical fibre sensors in recent years. Compared with conventional fibre-optic sensors, FBG sensors have a number of distinguishing advantages. Significant progress has been made in applications to strain and temperature measurements. FBG sensors prove to be one of the most promising candidates for fibre-optic smart structures. This article presents a comprehensive and systematic overview of FBG sensor technology regarding many aspects including sensing principles, properties, fabrication, interrogation and multiplexing of FBG sensors. It is anticipated that FBG sensor systems will be commercialized and widely applied in practice in the near future due to the maturity of economical production of FBGs and the availability of cost effective interrogation and multiplexing techniques.

https://iopscience.iop.org/article/10.1088/0957-0233/8/4/002/pdf

In-fibre Bragg grating sensors

In-service structural health monitoring (SHM) of engineering structures has assumed a significant role in assessing their safety and integrity. Fibre Bragg grating (FBG) sensors have emerged as a reliable, in situ, non-destructive tool for monitoring, diagnostics and control in civil structures. The versatility of FBG sensors represents a key advantage over other technologies in the structural sensing field. In this article, the recent research and development activities in structural health monitoring using FBG sensors have been critically reviewed, highlighting the areas where further work is needed. A few packaging schemes for FBG strain sensors are also discussed. Finally a few limitations and market barriers associated with the use of these sensors have been addressed.

Fibre Bragg gratings in structural health monitoring—Present status and applications

This work presents an overview of progress and developments in the field of fiber optic sensor technology, highlighting the major issues underpinning recent research and illustrating a number of important applications and key areas of effective fiber optic sensor development.

http://snake.persiangig.com/document/sensor1.pdf

Fiber optic sensor technology: an overview

A simple all optical fibre wavelength shift detection scheme, for use with fibre Bragg grating sensing systems, is described. The system is based on the use of a wavelength division coupler designed to exhibit a monotonic dependence of the splitting ratio on wavelength over a 50 nm range.

All-fibre Bragg grating strain-sensor demodulation technique using a wavelength division coupler

A polarisation-insensitive fibre optic Michelson interferometric sensor configuration is demonstrated. The approach is based on the use of birefringence compensation in a retraced fibre path using Faraday rotator mirror elements.<
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Polarisation-insensitive fibre optic Michelson interferometer

A technique for the demodulation of fibre Bragg grating (FBG) sensor arrays that uses a matched grating array to optically filter and track wavelength shifts from the FBG sensors is demonstrated. The use of matched grating arrays in the serial configuration represents an efficient and potentially low-cost interrogation technique for FBG sensors.

Matched-filter interrogation technique for fibre Bragg grating arrays

The behaviour of three types of high-birefringence fibre subjected to low temperature is investigated. From room temperature to -150°C the birefnngence increases over 20% in a linear fashion and exhibits no thermal hysteresis. After thermal cycling to -196°C no changes in polarisation beat length or attenuation are observed.

Low-temperature behaviour of high-birefringence fibres

Cracking behaviors within perovskite thin films were modeled through finite element analysis. Coupons of polyethylene terephthalate or PET, Indium Tin Oxide or ITO, and perovskite layers were placed in a three-point bend set-up and deformed. Modeling gave insight into ranges for physical properties of each layer, when absent or greatly varied in literature. The model proved the relationship between perovskite crystal size and its mechanical tolerance. Models with smaller crystals withstood more than 30% further displacement than those with crystals twice its size. A material replacement of ITO, the driving force causing cracking in films, was also modeled and cracking within the perovskite layer occurred significantly later, showing an improved resilience to bending.

M.A. Davis

Papers

All-fibre Bragg grating strain-sensor demodulation technique using a wavelength division coupler

Polarisation-insensitive fibre optic Michelson interferometer

Matched-filter interrogation technique for fibre Bragg grating arrays

Low-temperature behaviour of high-birefringence fibres

Predictive Modeling of Cracks within Flexible Perovskite Thin Films