Optical fiber sensor based on the intensity jump of a linear laser with two Bragg gratings

In this work we propose a new configuration for an optical fiber temperatur e sensor, based on a linear type Er-doped fiber laser. The laser cavity con sists of an Er-doped fiber and two identical Bragg gratings at the fiber en ds (working as reflectors). Temperature changes are detected by measuring, through one of the gratings, the intensity variations at the system's outpu t. When the temperature of one of the Bragg gratings is modified, a wavelen gth shift of its spectral reflectivity is observed. Hence, the laser emissi on intensity of the system is modified. We present experimental results of the intensity switch observed when the temperature difference between the g ratings detunes their spectral reflectances. Making use of this effect it i s possible to develop limit comparators to bound the temperature range for the object under supervision. This limiting work can be performed with a hi gh sensitivity using a very simple interrogation procedure.