Bridge engineering offer many unique opportunities for the use of advanced optical fiber sensing technology. In this
paper, the state-of-the-art of bridge structural health monitoring system(SHMS) based on optical fiber sensing
technology are reviewed and some disadvantages in present SHMS based on optical fiber sensing technology for existing
long-span bridge are indicated. In order to overcome those disadvantages, some fiber Bragg grating (FBG) products
developed by authors and corresponding industrialization enterprise are introduced. Focusing on an existing long-span
cable-stayed bridge-Wuhan Yangtze No.2 Bridge, the operational condition of the multi-parameter bridge SHMS mainly
based on FBG sensors is presented. Some initial monitoring results show that the whole performance of the SHMS FBGbased
is reliable and measuring data are reasonable.
The photosensitivity of photosensitive fibers is studied experimentally and theoretically. In the experiment, the relationship between the diffractive index increment of photosensitive fibers and UV irradiating dose based on an unbalanced Mach-Zehnder Interferometer (MZI) is measured. The experimental results show that the photo-induced index's increment of photosensitive fibers is multi-decaying-exponentially proportional to the UV irradiating dose and the order of magnitude of the maximum value can reach 10<sup>-3</sup>. In order to explain the relationship, a new assumption is proposed, which can give a good explanation based on the "color center model" and the "Kramers-Kronig" principal.