Design and analysis of fluorescence fiber gratings

Abstract

Rare-earth-element-doped fibers are wildly used in fiber amplifiers, fiber lasers and fiber sensors. Fiber Bragg Gratings (FBGs) are very important optical components in optical communication and sensing. Combining these two types of fiber products can give us a new type of fiber components, which is called fluorescence fiber grating here. The fluorescence fiber grating consists of fiber amplifiers and fiber gratings. It has serials of special characters. The method to fabricate the fluorescence fiber grating is writing the grating configuration to a rare-earth-elements-doped fiber. Normally, these fibers need pretreatment, for example, loading hydrogen. Differing to a fiber laser, the fluorescence fiber grating has a whole-length grating configuration along the rare-earth-elements-doped fiber. The emission of the fluorescence signal will occur along the whole components. There are no a clear fluorescence light source and clear reflection areas. When the pump light goes through the fluorescence fiber grating, the fluorescence light emits as incoherent signal. The intensity of the output light from the ends of the grating is the sum of the light intensity from the all parts of the fluorescence fiber grating. The coupling mode theory is used to explain the character of the fluorescence fiber gratings. The fluorescence light emitting from a part of the fluorescence fiber grating will be reflected by double sides of the grating. Then the sum of light intensity from the every part will give the spectrum of the output light. The shape of the spectrum of the output light depends on both the length and the modulation depth of the grating.