Bragg grating laser sensing systems for smart structures

A number of major challenges face the practical implementation of Smart Structure technology. One of the most important is concerned with the communication link between the structure´s resident fiber optic sensing system and the support structure. In general this optical interface must be robust, have minimal structural perturbation, low cost, be easy to fabricate and integrate with the structure. If multiplexing is not undertaken within the structure, then each sensor would have its own input/output and would have to ingress/egress the structure. This represents a severe challenge, since the most suitable sensors are based on single mode optical fibers and this interconnect must be very user-friendly. We have embedded 20 Bragg grating sensors within 5 large concrete (65 ft long) girders that support the deck of a new two span road bridge in Calgary, and have developed a 4 - channel fiber laser Bragg grating sensor demodulation system that can interrogate any four of these Bragg grating sensors at one time. This Bragg grating demodulation system involves 4 independent erbium doped optical fiber lasers, each of which is tuned by a connectorized Bragg grating that is embedded within a concrete girder