Fig. 1. Schematic for the inscription of MLPGs via point-by-point ultraviolet exposure. A supercontinuum source (SCS) is used for illumination and the transmission spectrum is displayed on an optical spectrum analyzer (OSA) in real time.

Fig. 2. (a) Transmission spectrum of a 25-period MLPG. The grating pitch is 80 μm and the diameter of the optical microfiber is 5.4 μm. (b) The calculated grating pitches for different resonant dip wavelengths in optical microfiber with a diameter of 5.4 μm.

Fig. 3. (a) Spectral responses of the MLPG to strain. The applied strain ranged from 0 to 7533 μϵ. (b) The measured resonant dip wavelengths (square scatters) and the linear fitting result (red line). The corresponding applied axial force is shown as the top axis.

Fig. 4. Spectral responses of (a) unsealed and (b) sealed MLPGs to temperature change. (c) The measured resonant wavelengths of sealed (square scatters) and unsealed (circle scatters) MLPGs at different temperatures. The linear fitting results are shown as red lines.