Sensing and Demodulation of Special Long-Period Fiber Gratings Induced by Scanning CO_𝟐 Laser Pulses

Figure 7

Transmission spectra of a number of R-LPFGs and the corresponding T-LPFGs fabricated with different twist rates for a grating period of Λ_𝐺=0.57 mm and a grating length of 𝐿_𝐺=28.5 mm (50 periods): (a) Λ_𝑇=100 mm (𝐿_𝐺/Λ_𝑇=0.285), (b) Λ_𝑇=75 mm (𝐿_𝐺/Λ_𝑇=0.38), (c) Λ_𝑇=60 mm (𝐿_𝐺/Λ_𝑇=0.475), (d) Λ_𝑇=50 mm (𝐿_𝐺/Λ_𝑇=0.57), (e) Λ_𝑇=37.5 mm (𝐿_𝐺/Λ_𝑇=0.76), and (f) Λ_𝑇=30 mm (𝐿_𝐺/Λ_𝑇=0.95) [5].

(a)

(b)

(c)

(d)

(e)

(f)