Applied To The Doped Erbium Fiber Source Of Long Period Fiber Grating Filter

Broadband light sources have been a topic because of their wide range of applications with the development of photoelectric technology. In particular, erbium-doped superfluorescent fiber sources (EDSFS) have been considered to be the optimum candidate for use in fiber optic gyros (FOG). The typical erbium-doped fiber gain spectrum is a combination of a high-intensity region and a flat part spectrum, and the power difference has limited the bandwidth of EDSFS. The output power, bandwidth and the flatness degree are represented the capability of EDSFS. However, the recent demand for immediate expansion of the fiber-optic communication window has been an area of significant interest. The addition of a filter to induce higher spectral losses in the high-intensity region in EDSFS is the primary choice recently.The long period fiber gratings (LPFG) have been chosen to be the filters finally after comparing several filters. The specific loss could be achieved by the coupling between two co-propagating modes in LPFG. The long period fiber gratings have been the best choice owing to their simple structure, low insertion loss, broad bandwidth, small reflection, low cost and easier manufacture technology.The main purposes and contributions of this thesis are following:1. After choosing the pump laser, the optical isolator, the wavelength division multiplexing (WDM), the erbium-doped fiber and the EDSFS structure, the original EDSFS spectrum could be measured.2. The designing of LPFG filter has been given in detail. The transmission spectrum of LPFG could be achieved based on the original EDSFS spectrum. How the high-intensity region in the original EDSFS spectrum was flatted by the LPFG filter has been shown.3. The coupled-mode theory and matrix theory of LPFG have been studied. Based on the erbium-doped fiber which has been chosen for EDSFS, SMF-28 of Corning Corporation and photosensitive fiber of CorActive Corporation, the optimum fiber grating period, length, the maximum cross transmission wavelength and the relation...