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

Sensitive optical biosensors for unlabeled targets: a review.

Review of the present status of optical fiber sensors

Recent research on fibre optic long-period gratings (LPGs) is reviewed with emphasis placed upon the characteristics of LPGs that make them attractive for applications in sensing strain, temperature, bend radius and external index of refraction. The prospect of the development of multi-parameter sensors, capable of simultaneously monitoring a number of these measurands will be discussed.

https://iopscience.iop.org/article/10.1088/0957-0233/14/5/201/pdf

Optical fibre long-period grating sensors: characteristics and application

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

A fibre Bragg grating based laser sensor system with an RMS strain resolution of 5.6*10/sup 14// square root Hz at 7 kHz is reported. An interferometric readout technique is used to determine strain induced wavelength shifts in the laser with high resolution.

Fibre laser sensor with ultrahigh strain resolution using interferometric interrogation

An interferometric fiber-optic magnetometer capable of measuring dc magnetic fields is demonstrated. Sensitivity on the order of 10-6Oe per meter of sensor fiber at 1-Hz bandwidth has been achieved.

A fiber-optic DC magnetometer

Using a cylindrical, DC field biased magnetostrictive transducer in a fibre-optic magnetometer we demonstrate 70 fT/√(Hz) resolution near 34 kHz. This represents 30 dB improvement over previous results. Resolution is limited by interferometric phase noise and is free from upconverted lowfrequency noise and residual signal effects.

High-frequency fibre-optic magnetometer with 70 fT/ square root (Hz) resolution

A correlation is presented between experimental data obtained under various operating conditions and a modified coherent rotation model which predicts the behavior of the residual signal and the sideband noise. The authors identify an operating regime that eliminates the residual signal and gives rise to a reduction in noise levels by a factor of five over previously reported results. Minimum detectable fields of 11+or-2pT/ square root Hz at 1 Hz and 38+or-8 pT/ square root Hz at 0.2 Hz are achieved. >

K.P. Koo

Papers

Fiber grating sensors

Fibre laser sensor with ultrahigh strain resolution using interferometric interrogation

A fiber-optic DC magnetometer

High-frequency fibre-optic magnetometer with 70 fT/ square root (Hz) resolution

Detection of low-frequency magnetic signals in a magnetostrictive fiber-optic sensor with suppressed residual signal