The spatial distribution of the chirp profile of a 4-cm-long nonuniform fiber Bragg grating (FBG) was studied with the exertion of local pressure on the fiber through the application of transverse force to a small grating section (0.3 mm). The technique was also used for spectrally shaping a previously unchirped, 18-cm-long Bragg grating, generating a narrow transmission window ( 400 MHz) inside its reflective band. A physical model was developed in order to estimate the phase shifts induced by pressure. A numerical simulation based on the piecewise-uniform approach was also used to calculate the consequent changes in reflected spectrum. Experimental and theoretical data show good agreement and the pressure technique proved to be adequate for grating characterization and spectral shaping.
C. J. S. de Matos, P. Torres, L. C. G. Valente, W. Margulis, and R. Stubbe, "Fiber Bragg Grating (FBG) Characterization and Shaping by Local Pressure," J. Lightwave Technol. 19, 1206- (2001)