Fiber optic sensing has come a long way in the past decade. What were once university prototype instruments and sensors are now well qualified, commercial products. Much credit for this progress is due to a few pioneers who led the way, and one of those pioneers is Dr. Farhad Ansari of the University of Illinois at Chicago.

The Chicago Tribune recently highlighted one of Dr. Ansari’s applications. (See article) In this application, Ansari and his team installed an array of FBG scour sensors on a bridge at risk of damage from undermined foundations. If this application proves successful, these scour sensors will provide an important new tool for departments of transportation around the world. Thousands of bridges are at risk from scour, and there are few practical means for monitoring scour and its effects. For more on this scour sensor and how to access this technology, contact:

Mark P. Krivchenia
Technology Manager
University of Illinois at Chicago
Office of Technology Management
at krivchen[at]uic[dot]edu

Because these sensors are based on fiber optics, they can survive decades in this harsh environment. Also, because fiber optic sensing systems are so versatile, other FO sensors (e.g., strain, acceleration, temperature) can be added later without adding to the FO instrumentation.

Ansari’s work at UIC, as president of the International Society for Structural Helath Monitoring of Intelligent Infratructure, and as the founder of Structural Monitoring Services focuses on a central theme: advancement of measurement and analysis tools and their practical application in the field. Rather than maximizing the numbers of sensors on a structure, Dr. Ansari focuses on finding optimal numbers and types of sensors to deliver the data streams necessary — and no more. This keeps the data analysis work manageable and ensures that the structure’s owner gets actionable information.

For more on Dr. Ansari and his work, go to:

http://www.cme.uic.edu/CME/WebHome
http://ishmii.org

Yesterday, Micron Optics announced the release of the os4400, a fiber optic temperature sensing cable. This cable addresses a growing need for durable, low-cost temperature sensing in areas with limited access, such as tunnels, bridges, mines, downhole and other applications where distributed measurements are needed at specific points over long distances. You can read the full press release here.

Micron Optics os4400 temperature sensing cables are available immediately. For more information, please go to our sensors page on our website or contact us directly at info(at)micronoptics(dot)com.

Micron Optics produces the most reliable, capable and widely used FO instruments, sensors, and software in the world, but it’s our integrator partners who make so many successful applications possible. One good example is Sengenia, Ltd. in Northern Ireland. They’ve highlighted a recent application in their newsletter (see excerpt below) that involved embedding a network of FBG strain gages in a bridge deck and measuring them with a Micron Optics sm125 instrument.

These sensors were needed to evaluate the performance of a new “RockBar” reinforcement material for concrete decks. In quotes from the bridge owner, it was clear that Sengenia’s expertise and Micron Optics ENLIGHT software made the process of both installing the sensors and extracting and analyzing the data fast and simple.

Through their efforts, Sengenia has demonstrated to yet another group of engineers the power of fiber optic sensing technology. Successes like this one will lead to more applications, better methods, a greater variety of sensors, and a more widespread understanding for how FO sensors can enhance and improve upon traditional structural analysis and inspection practices.

For more information about Sengenia’s capabilities, and to subscribe to their newsletter, visit their website at http://www.sengenia.com.

Excerpted from Sengenia’s newsletter:
It is known that every year millions of pounds are spent, in the UK alone, on the repair and rehabilitation of concrete infrastructure. A large proportion of this is due to the corrosion of the reinforcing steel that is used and now with the introduction of fibre bars, such as those provided by MagmaTech , it is hoped that such financial waste can be prevented.

Thompson’s bridge is a replacement bridge to carry the two-way, A class road in Co. Fermanagh, Northern Ireland. The previous bridge was a pinch point and not suitable for the wide loaded vehicles that frequently use this stretch of road. The bridge is a single span, consisting of reinforced concrete abutments on piled foundations. The superstructure comprises of ‘W’ precast pre-stressed beams with a reinforced concrete slab bridge deck reinforced with RockBar.

Queen’s University Belfast (QUB), through Dr Su Taylor, were tasked with providing much of the specification details for the bridge and Sengenia worked alongside QUB for the load testing aspect of the project. Sengenia were able to use their fibre optic sensors, taking advantage of the ability to create more than one sensor along the length of a single strand of fibre, thereby reducing the cabling and therefore installation time and effort normally required. When used in tandem with the Micron Optics sm125-500 unit and Enlight software the monitoring process becomes a simplistic one, especially when taken in direct comparison with the alternative methods that were also in use through QUB.

Ben Williams, MD of MagmaTech commented ‘I was very interested to see the use of the fibre sensors actually in the field. The system used to acquire and display the data was remarkably simple to comprehend but yet clearly a highly sophisticated and powerful tool in such work. At MagmaTech we intend to pursue this further with Sengenia, looking always at how we can enhance the offering to our customers as well.’

A few years ago, Micron Optics responded to a request from the FAA to create a fiber optic (FO) version of an embedded strain sensor for asphalt pavement. They were looking for a sensor that reduces cabling runs and is not susceptible to interference from lightening or other electrical noise.

The standard asphalt strain sensor at the time was an 8-inch long H-Bar gage based on electrical resistance foil strain gages. Micron Optics modified its os3600 gage to mimic the traditional gage and worked with the FAA to install two such gages and two FBG temperature sensors.

The results were interesting. The FO gages measured strains side-by-side with the electrical resistance H-Bar gages. The FO strain measurements tracked the expected values, and they exhibited no noise in the measured signal. (Noise was an ever present problem with the electronic gages.) After a few passes of the paver, one of the fibers was broken and two of the four sensors were lost. The quick prototype did not go far enough to protect the fiber, but still the fundamental performance was promising.

Fast forward to a few weeks ago- Applied Geomechanics (AGI), a key Micron Optics integrator with both FO experience and a long history with (and provider for) the standard H-Bar strain gages, installed several types of FO gages in another FAA test. Results were very good. The new FO sensor design allowed for placement in between layers of hot mix asphalt during construction as well as surface embedment in both asphalt and concrete surfaces. All sensors survived installation compaction and rolling and were immediately used for data collection.

The bottom line is that AGI will be moving forward with their customers in using FO gages for long term pavement studies for roads, bridge decks and runways. Read the full case study “Fiber Optic Sensing Solutions for the FAA Case Study” on AGI’s website.