A large gain bandwidth (> 200 nm) for near-infrared light signals Cr4+-doped dielectric fiber amplifiers are expected to amplify laser light in the spectral region from 1.1 to 1.7 μm. This spectral range includes two key wavelengths centered at 1.3 μm and 1.55 μm currently used in fiber optical communication systems.
Current optical fiber amplifier technology is based on erbium (Er) and praseodymium (Pr)-doped fibers with gain bandwidth of ~ 20 nm. Newer experimental versions at Lucent Technologies and NTT have achieved 80 nm bandwidth for erbium systems. The proposed fiber amplifier shown in Figure 1 consists of a Cr4+-doped optical fiber amplifying medium and a light source capable of pumping the fiber in such a way as to excite chromium ions. The gain bandwidth of Cr4+-based laser systems is larger than 200 nm. The amplifying medium of the fiber comprises a plurality of Cr4+-doped crystalline particles capable of lasing at 1.3 μm and/or 1.55 μm, and having diameters of approximately 0.05 μm to 500 μm. Crystalline particles are dispersed within a medium which has an index of refraction which matches that of the crystalline particles. The fiber can be pumped by a fiber laser, a Nd:YAG solid-state laser, or a semiconductor laser.