Fig. 1. Device diagram of long-distance sensing system based on uwFBG array

Fig. 2. Segmented acquisition process

Fig. 3. Power distribution of signal optical at various locations on a 50 km fiber optic cable. (a) Input optical power is 35 dBm; (b) Raman pump optical power is 600 mW

Fig. 4. Changes in GR and distribution of signal optical power when the input optical power is different. (a) Changes in GR values; (b) distribution of signal optical power

Fig. 5. Long-distance sensing system experimental platform

Fig. 6. Reflected optical intensity of uwFBG in each place corresponds to the output voltage at different input optical powers. (a) RFA configuration at 0 km; (b) RFA configuration at 10 km

Fig. 7. Reflected optical intensity of uwFBG everywhere in the optical fiber. (a) RFA configuration at 0 km, input optical power of 43 dBm; (b) RFA configuration at 10 km, input optical power of 41.3 dBm

Fig. 8. Reflected optical intensity of uwFBG array within 50 km after segmented gain

Fig. 9. Demodulation effect of the system on the center wavelength of uwFBG at different positions of the optical fiber. (a) 0 km; (b) 50 km

Fig. 10. Relation between uwFBG center wavelength and various variables. (a) Temperature variation curve; (b) strain variation curve