One of Micron Optics’ largest market segments for optical sensing systems is for monitoring of bridges. Hundreds of bridges today are monitored using FBG based sensors, but >98% of these are in Asia and Europe. But, only a few structures in North America use this technology. Why?

I think one answer is resistance to change. Owners are more comfortable using their 35 year old visual inspection protocols than adopting better technology. And, there has been no FHWA mandate in the US that all bridges of certain classes or deteriorated condition must use objective measurements to support the visual bridge inspection process, unlike China.

An Atlanta company, LifeSpan Technologies, on behalf of our industry, is promoting the use of advanced technologies that are more precise and objective to help owners and funding agencies make better decisions. In brief, they conclude that deployment of advanced condition assessment technologies will lower both the risk and life cycle costs for bridge owners and taxpayers. I agree.

LifeSpan makes a solid case for their argument in their October 2008 white paper, A Better Way to Fix our National Bridge Problem. Find it here: www.lifespantechnologies.com.

This proposed solution is independent of the assessment technology choice. And since there are number of competent technology suppliers in this business, finding what you need isn’t that difficult. Most technologies have unique features, so it pays to do your homework and compare both technical approaches and costs.

I believe that it’s only a matter of time before FHWA and the state DOTs will begin to use these advanced technologies routinely. Proposed solutions like this one from LifeSpan are sure to help accelerate the process.

Tom Graver
Director, Optical Sensing Group

Most commercialized fiber optic sensors operate at temperatures between -40 and 150 C. Higher temperatures can degrade polyimide fiber coatings (above 250 C) and erase FBGs from the fiber core (above 400 C).

Some industrial applications (e.g., oil refining, steel production and chemical formulation) require much higher temperatures, and often conventional thermocouples do not last long enough or do not operate reliably due to high EMI or cumbersome cabling.

Several research organizations and commercial companies are working to develop high temperature optical sensors that are both accurate and reliable in high temperature environments. One such company is Chiral Photonics, Inc. in Pine Brook, New Jersey. They recently announced a novel optical sensor that uses twisted fibers to create a thermally sensitive spectral response. The sensor appears to be stable, accurate and repeatable at temperatures up to 1000 C.

Find details at: www.chiralphotonics.com/

Now that the optical core is nicely characterized, Chiral is working on ruggedized packaging for large-scale field deployments. Sensor readings are made simple with self-contained laser instrumentation and software from Micron Optics — so the user does not need optical systems expertise to use these sensors. They are as easy to use as conventional sensors.