Fiber Bragg grating (FBG) characterization and shaping by local pressure

The spatial distribution of the chirp profile of a 4-cm-long nonuniform fib er Bragg grating (FBG) was studied with the exertion of local pressure on t he fiber through the application of transverse force to a small grating sec tion (similar to 0.3 nm). The technique was also used for spectrally shapin g a previously unchirped, 18-cm-long Bragg grating, generating a narrow tra nsmission window (similar to 400 MHz) inside its reflective band. A physica l model was developed in order to estimate the phase shifts induced by pres sure. A numerical simulation based on the piecewise-uniform approach was al so used to calculate the consequent changes in reflected spectrum. Experime ntal and theoretical data show good agreement and the pressure technique pr oved to be adequate for grating characterization and spectral shaping.