Double inscribing method with CO2 laser for suitable spectrum of LPFG used in multipoint temperature sensor

摘要

A new method, the double inscribing method using a CO2 laser, is proposed to make the loss spectrum of LPFGs more suitable when constructing a multipoint temperature sensor using several LPFGs. The method makes the main peak in the spectrum larger and suppresses associated sub peaks without greatly affecting the resonant wavelength of the LPFG in the range where the grating pitch of the LPFG is longer than 0.52 mm. Finally, the relationship between the grating pitch and a parameter of the method is clarified to obtain suitable spectrum for the multipoint sensor.