A novel optical fibre sensing system has been developed using fibre Bragg gratings embedded in a SmartRod structure based on pultruded composite rods. A thorough investigation of the mechanical reliability of the fibres, gratings and whole SmartRod structure was made. Techniques used included tensile testing, static fatigue in bend and dynamic fatigue in bend, in a variety of environments. The strength and interface properties of the whole structure were also tested. The mechanical reliability of the system was found to be very adequate for the proposed tunnel applications.