A comparison of the spectral properties of high temperature annealed long period gratings inscribed by fs laser, UV and fusion-arc

Long period gratings have been inscribed in standard single mode fibre using a fs laser system, a fusion arc and a UV laser and a comparative study carried out of their thermal behaviour. The fs laser induced gratings can survive temperatures in excess of 800 degrees C, however the inscription process can induce considerable birefringence within the device. Annealing studies have been carried out showing that below 600 degrees C, all three grating types show a blue shift in their room temperature resonance wavelengths following cyclic heating, while above 600 degrees C, the UV and are induced LPGs exhibit a red shift, with the fs LPG showing an even stronger blue shift. High temperature annealing is also shown to considerably reduce the birefringence induced by the fs inscription process.