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The role of Optical Fiber Sensors In Internet of Things :A review

Paul Stone Brown MACHESO

Euromed Research Center, Euromed University of Fes (UEMF)�BP 51, Route Nationale de Meknès (Rondpoint Ben souda)

30 070 Fès, Maroc

Email: pmacheso@unima.ac.mw

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Biography

Paul Stone Brown MACHESO is a Ph.D. student in Engineering Sciences (Optical Fiber Sensors) with Euromed University of Fes. He is also Lecturer in Electronics in the Department of Physics and Electronics, University of Malawi.
Paul holds a Master of Science in Internet of Things Wireless Intelligent Sensor Networking from University of Rwanda, College of Science and Technology and a Bachelor of Education Science with a major in Physics & Electronics from University of Malawi.
His research interests extend from Internet of Things, Wireless Sensor Networks Embedded Systems to Photonics, Optic fiber sensors and Fiber Bragg Grating (FBG).

Introduction

In IoT technology, multiple sensor nodes are put inside or around an object and connected to the internet for data and communication exchange, sensing, monitoring, location, tracking, and intelligent sensing object administration [1].
Because of the prospective applications, such as remote monitoring of transformer substation subsidence, intelligent power grid sensing, and mine safety monitoring, the use of fiber Bragg grating (FBG) Optical sensors in the Internet of Things (IoT) has sparked a lot of academic interest [2].
In Optical fiber a sensing device is used in made of grating structures. These sensors detect various physical parameters like temperature, pressure, vibrations, displacements, rotations, and chemical species concentration [1-2].��

Problem Statement

Conventional sensors which are not immune to Electromagnetic�Interference , are prone to corrosion and have no capacity to perform distributed sensing over a large area hence leading to be expensive to deploy [2].
Further to that convectional sensors are resource constrained require battery power and do not offer non-contact perturbation free means of monitoring physical parameters [3].
These convection sensors do not have high accuracy, are not compact in size do not require a lot of maintenance in the measurement of physical parameters[2-3].
This is the reason why Optical Fiber Sensors based on (Fiber Bragg Grating) is the novel proposition to be used in Internet of Things to address the aforementioned problems�

Theory of Optical Fiber Sensors (OFS) Based on Fiber Bragg Grating (FBG).

Fiber Bragg Gratings are created by exposing a single-mode fiber's core to a periodic pattern of strong laser light from the side.
The exposure causes a permanent rise in the refractive index of the core of the fiber, resulting in a fixed index modulation based on the exposure pattern. A grating is a type of fixed index modulation.
Every reflected portion of light combines to form one reflected beam of light, but this is possible only if Bragg condition is met. The Bragg condition is given as:

(1)

where Λ is the grating period that forms the distance between two adjacent grating planes, n_eff is the effective core refractive index, and λ_Bis the Bragg wavelength [4]��

Fiber Bragg Gratings

Figure 1. Schematic diagram of fiber Bragg grating [5]��

Applications of Optical Fiber Sensors in Internet of Things

Optical fiber FBG based Sensors have a wide range of applications in the field of remote sensing because they do not require electrical power at the remote location and are tiny [3-4] which makes them easier to proliferate even in surface health monitoring of structures hence usable in civil engineering in monitoring e.g dams,
Further applications of Optical Fiber FBG based Sensors include monitoring the health of composite materials, determining different chemical characteristics, biological and biometric applications, such as blood flow measurement and also industrial applications e.g electric power industry, gas and oil exploration [4].
These applications of FBG based sensors can play a major role in IoT as they are immune to Electromagnetic interference , compact in size, lightweight are able to perfom distributed sensing do not require electric power.��

Example of a Deployed FBG Optical Fiber Sensor monitoring Strain

Figure 2. Deployed FBG Optical Fiber Sensor monitoring Strain

Challenges of Using FBG Based Optical Fiber Sensors in IoT

Despite being tiny and capable of monitoring practically all physical parameters such as pressure, temperature, vibration, and multifunctional sensing, FBG sensors are prone to challenges.
Due to detector sensitivity, efficiency of the light sources with respect to parameters such as temperature, the FBG sensors are also subject to fluctuations in the transmission properties of the optical fiber cables. sensors (OFS) have numerous hurdles and constraints [5].
They require much expertise in deployment and fabrication and expensive and complex industrial equipment is needed e.g Optical Spectrums Oscilloscopes.

Future Scope of the Study and Conclusion

The future scope of the study include simulations of FBG based optical sensors in ANSYS lumerical for Pressure, Temperature, Humidity, and Strain for a start and fabricating them into prototypes which would be deployed in IoT environments.
In conclusion to this review a recommendation of using Optical Fiber Sensors in the domain of Internet of things should be considered as they are immune to electromagnetic interference, Do not require electric power and are compact with also a priviledge of distributed sensing.

References

Cui, C., Gao, L., Dai, N., & Xu, Q. (2021). Fiber Bragg Grating Inclinometer-enabled IoT Sensing System with Low Power Consumption and Small Size. Sensors and Materials, 33(7), 2321-2331.
Santos, J. L. (2021). Optical sensors for industry 4.0. IEEE Journal of Selected Topics in Quantum Electronics, 27(6), 1-11.
Aleksic, Slavisa. "A survey on optical technologies for IoT, smart industry, and smart infrastructures." Journal of Sensor and Actuator networks 8.3 (2019): 47.
Sahota, Jasjot K., Neena Gupta, and Divya Dhawan. ”Fiber Bragg grating sensors for monitoring of physical parameters: A comprehensive review.” Optical Engineering 59.6 (2020): 060901
Barrias, Antonio, Joan R. Casas, and Sergi Villalba. ”A review of distributed optical fiber sensors for civil engineering applications.” Sensors ´ 16.5 (2016): 748

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