Optical Strain Sensor Fundamentals

Optical strain sensors, namely those based on Fiber Bragg Grating (FBG) technology, have been gaining increased attention particularly in the field of infrastructure monitoring over the past decades. But how does an optical sensor work? How do we compensate for optical losses? How many sensors can be integrated into one single fiber? Our experts dug deep to provide their best answers for you about all the important questions regarding strain measurement using fiber optical sensors. Click an option below to direct you to the content on the page.

  1. An Introduction to Optical Strain Measurements
  2. Basics of Fiber Bragg Grating (FBG) Technology
  3. Selecting the Right Strain Sensor, Adhesive and Accessories
  4. Installation of Optical Sensors: All there is to Know
  5. Applications of Optical Strain Sensors: Looking Beyond
  6. Acquiring Data with the Right Hardware and Software 
  7. Free Training on Optical Strain Measurements

1. An Introduction to Optical Strain Measurements


Optical strain measurement glossary

You can benefit from our practical on-line glossary by looking up the most important technical terms in the field of strain measurement using optical strain sensors. 

The reference white paper on strain measurements using FBG sensors

Get a complete overview of the topic of "Strain measurements with Fiber Bragg Grating sensors" - Manfred Kreuzer's reference paper. This paper gives a short introduction to FBG sensors, points out their special strengths and weaknesses and describes a measuring system that enables strain gauges and FBGs to be measured simultaneously... You can also download the article "Sensing of Surface Strain with Flexible Fiber Bragg Strain Gauges"  that provides information on strain sensing instrumentation.

Experimental Stress Analysis (ESA) using strain gauges

The principle of Experimental Stress Analysis (ESA) consists of using strain gauges to measure the strain on a component's surface. The absolute value and direction of the mechanical stress is determined from the measured strain and known properties of the material (modulus of elasticity and Poisson’s ratio). These calculations are based on Hooke’s Law that is applicable to the elastic deformation range of linear-elastic materials. Click here to learn more .


2. Basics of Fiber Bragg Grating (FBG) Technology


What is a fiber Bragg grating

A fiber Bragg grating operates as a sensor by suffering changes in  the wavelength when  the strain is applied. Fiber Bragg gratings are just a few millimeters long, highly sensitive, and very reliable. These sensors are easy to install, immune to electromagnetic interferences, and can also be used in highly explosive atmospheres. Learn more about their properties here.

How does a fiber optical strain gauge work

“When people need to measure strain, they first think of electrical strain gauges. Optical strain gauges can come in handy, though, where electrical ones won’t work, for example due to environmental conditions” , says Cristina Barbosa, Product Manager at HBM FiberSensing. Learn more by clicking here.

Common questions on FBG technology & systems

How is strain measured? Is strain measurement sensitive to temperature? What is the maximum distance that an optical fiber line can achieve? If you are looking for quick and uncomplicated answers to these and other questions on measuring with light, check out our practical on-line FAQs page here.


3. Selecting the Right Strain Sensor, Adhesives and Accessories


How to select the right optical strain sensor

HBM offers two lines of optical strain sensors based on Fiber Bragg Grating (FBG) technology that are suitable for almost every measuring task. But how do you find the right strain sensor? Here you will get the complete information to help you find the most suitable strain gauge or sensor for your needs.

How to select the right adhesive

Optical strain sensors can be applied to the surface of the object to be measured using adhesives. Here you can learn which adhesive should be used when gluing an optical strain sensor and tips for preparing a measuring point, which ensures good bonding for strain transfer.

How to improve the optical measurements

The quality of measurement with strain sensors essentially depends on the type of installation and design of the measuring point. A thorough preparation of the installation surface, correct connection and splicing are important factors for obtaining problem-free results. Check HBM range of easy-to-set-up accessories here.


4. Installation of Optical Strain Sensors: All There is to Know


How to weld a strain gauge

Some environments are not suitable for the bonding of strain gauges owing to very low temperatures or excessive dust formation, e.g., at construction sites. Weldable strain gauges are the best choice for being used in these kinds of environments. Watch our video on the right on how to weld your strain gauge correctly.  

 

Tips for configuring an optical strain sensors' array

In order to plan an optical strain gauges' chain, several aspects must be taken into consideration. Learn here how to accurately configure an array of optical strain sensors from HBM FiberSensing for a successful installation.

How to fusion splice optical fibers?

This video shows the procedure conducted to fusion splice two optical fibers. Fusion splicing means permanently joining two optical fibers together using heat, so that the light passing through the fibers is not scattered or reflected back by the splice. Click on the video to learn more.

 

5. Applications of Optical Strain Sensors: Looking Beyond


Infrastructures monitoring with optical sensing systems

Optical technologies and sensors come across as a viable and promising option to meet the challenges of monitoring a structure's health, from design, construction, operation to rehabilitation or end of service life, specially when large sensing networks and hazardous environments are involved. Find out more here.

Gaining insight into wind turbines' health with fiber optical technology

The requirements for both on- and offshore wind power turbine designs are constantly increasing. Learning more about the behavior of the structure is a tool towards an optimized design and increased efficiency. Through continuous monitoring of the wind turbine, structural integrity can be ensured, leading to an extended and profitable life-cycle.That's when optical technologies emerge as an ideal solution for monitoring or testing the wind turbines' structure and components. Click here to learn more.

The potential of optical sensors for condition monitoring

Condition Monitoring Systems (CMS) are designed to ensure the long-term efficiency of many structures' components, such as wind power plants' components. The focus moves here from electric technology to optical sensor technology as a viable alternative for condition monitoring, such as of the wind rotor blades.

Optical fiber sensors vs. conventional electrical strain gauges for infrastructure monitoring

Get a complete overview of the topic of "Optical Fiber Sensors vs. Conventional Electrical Strain Gauges for Infrastructure Monitoring Applications".


ePaper available here


6. Acquiring Data with the Right Hardware and Software


The right data acquisition systems for reading optical fiber sensors

Optical strain sensors are easy to install, electromagnetically safe and can also be used in highly explosive atmospheres, but having the right interrogator in place is important to retrieve the most accurate static or dynamic measurements. HBM FiberSensing’s BraggMETER is a line of optical interrogators for Fiber Bragg Grating (FBG) based sensors. More info here.

How to configure optical strain sensors in BraggMONITOR SI

In this tutorial, you will learn how to acquire strain measurements from optical sensors using HBM's BraggMONITOR SI data acquisition software and FS22 BraggMETER SI (static) interrogator. The Smart Peak Detection feature allows accurate and stable detection of all FBG peak values in large/complex sensing structures.

 

Hybrid measurements with catman software

Optical interrogators from HBM FiberSensing are compatible with catman® software, which allows hybrid optical/electrical sensing to be easily managed. Watch our demo video on hybrid measurements using the HBM software.

 

7. Free Training on Optical Strain Measurements


Recorded webinars

Missed one of our live webinars? Watch our recorded webinars on optical strain measurements and sensors. Use the filter to select the ones that best suit your needs.

Successful case studies and references using optical FBG sensors

Get access to all the success stories regarding the use of optical strain sensors in a wide scope of measurement applications and monitoring projects undertaken by HBM. Just select Optical FBG Sensors in the dropdown list under Type of Sensors Used here.

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