Interrogation of 5000 ultraweak fiber Bragg grating sensors using optical frequency domain reflectometry

We demonstrate a sensing network with 5000 identical ultraweak fiber Bragg gratings (uwFBGs) at equal separations of 100 mm based on optical frequency domain reflectometry. The fiber is 510-m long and includes 5000 uwFBGs with a reflectivity of 0.02% and with identical peak reflection wavelengths of ∼1553.9  nm. With an applied strain from 0 to 600  μϵ on the uwFBGs, this system can unambiguously distinguish the shifts in the wavelengths and the locations of the uwFBGs. Compared with a traditional FBG interrogation method, this technique achieves a high-spatial resolution and a large number of multiplexed uwFBGs. The distinct advantages of the proposed sensor network make it an excellent candidate for distributed strain sensing measurements.