A fiber Bragg grating is embedded into a beam of polyethylene terephthalate glycol (PETG). Through
bending, the Bragg wavelength could be continuously tuned over a range of 60 nm, with maintained reflectivity and 3-dB linewidth.
This image shows a three-point bending set-up, with an arrow pointing at the FBG location. See Liu et al. Optical Materials Express 9, 4409-4417 (2019).