A novel method to tune the chirp ratio of fiber grating without the central wavelength shift is proposed using a two-fixed-end compressive bar which induces a linear strain distribution along the grating.The chirp ratio tuning principle is analyzed according to material mechanics,and the reflection and time delay characteristics of the grating during the tuning process are simulated as well.The bandwidth tuning range is from 6.52 nm to 12.78 nm when the grating is tuned in the broadening way,meanwhile,the b...