Broad band optical strain sensing systems for a wind turbine. The strain sensing system includes an optical fiber with an input at one end and an output at the opposite end. The optical fiber is provided with Bragg sensors between the input and the output. By injecting light at the input of the fiber, measuring the spectral intensity distribution of at the output of the fiber and determining spectral locations of intensity notches in the spectral intensity distribution, it is possible to determine strain values at the locations of the Bragg sensors from the transmitted light.