CO2-laser induced LPFG torsion characteristics depending on length of twisted fibre

The unique torsion characteristics of the CO2-laser-induced LPFG depend strongly on the length of the twisted fibre. While the LPFG is much shorter than the twisted fibre, its resonant wavelength and amplitude change wavelike with the twist-rate applied. In addition, the shift of the resonant wavelength is dependent on the twist direction.