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.