Time-of-flight fiber optic sensors for strain and temperature measurement

The base of time-of-flight fiber optic sensors using short laser pulses was presented. This kind of sensors can work in the transmission mode or in the reflection mode. Because attenuation of these sensors is small, they may be operated in sensor networks having tens or hundreds measuring points. The example of a time-of-flight fiber optic sensor is a segment of a singlemode optical fiber that is affected by temperature or longitudinal stress. The changes of temperature or strain applied to the fiber change the propagation time of light in the fiber. In the paper a time-of-flight sensor is presented. Using a picosecond semiconductor laser source and a photon avalanche photodiode detector, the system iscapable of measuring of temperature and force acting on the fiber. The performance of such sensor was tested for temperature in 20÷110 °C range or stress force in 0÷8 N range.