Theoretical and Experimental Study on the Fabrication of Double Fiber Bragg Gratings

A new method for fabricating double fiber Bragg gratings at the same location on a fiber is described. Two series of refractive index change in a fiber, not similar to the normal fiber grating, have been realized by a Fresnel prism interferometer. As a result, the transmission spectrum of the fiber grating is widened, which is attributed to the chirp of the grating. If the exposure condition is controlled properly, then there are two obvious loss peaks in the transmission spectrum observed, which shows that the double fiber Bragg gratings exist in the fiber core. At the same time, a potential application—simultaneous measurement of strain and temperature using this kind of gratings—is analyzed.