利用扫描曝光法,通过控制曝光前施加在光纤上的拉力,经过多次不同拉力状态下的光刻技术,实现了多波长光纤Bragg光栅(FBG)的制作。实验发现,多重曝光的子FBG位置和叠加程度对子FBG的谱形有很大的影响,只有当各层子FBG长度、位置完全重叠时,各波长光谱才不会受到短波振荡的影响;对载H增敏光纤,第n+1层子FBG的刻写,总会使前面n层子FBG的波长变大,反射率变强;而对掺Ge光敏光纤,多重曝光只将先制作的子FBG波长变大,而所有子FBG反射率都会变弱。通过合理设计曝光量,在载H单模光纤上制作了阻带谱形一致的四波长FBG。经实验测试,子FBG波长具有相同的温度系数和应变系数。
A fabrication method of multi-wavelength fiber Bragg grating(FBG)is introduced in this paper.Using the scan exposure method,multi-wavelength FBG can be successfully manufactured through applying different tensile forces during multiple exposures on the same fiber.Experiment results show that the position and the overlap of different sub FBGs will greatly affect the spectrum of every subFBG.The spectrum of each sub-FBG will be affected by short wave oscillation unless the lengths and positions of all sub-FBGs are fully overlapped.For hydrogen loaded fiber,the wavelength and reflectivity of the nth level FBG will increase as the(n+1)th level FBG is written.But for germanium doped photosensitive fiber,multiple exposures will increase the wavelength of previous sub-FBGs while decrease the reflectivity of all sub-FBGs.Through well distributing exposure intensity of every sub-FBG,a four-wavelength FBG with the same sub FBG′s spectrum is fabricated on a hydrogen loaded single mode fiber,and every sub-FBG has the same wavelength temperature and tensile coefficient.