Prototype of TOF (time of flight) fibre optic sensor: Sustainable Bridges Background Document 5.9

This report describes the prototype of a bridge monitoring system based on pulsed TOF (Time-Of-Flight) laser radar technology. The TOF method is based on measuring the time delay between optical pulses reflected from the optical reflectors in a single mode optical fiber. The TOF system has been classically used for measuring long distances in open space, but it has been also shown lately to be applicable for measuring accurately fiber strain by increasing the pulsing frequency and utilizing high speed logic circuits for averaging a large number of measurement results in a short time.