1.3 μm Raman fiber amplifiers

The majority of installed terrestrial fiber optic communications systems currently operated in the second communications window at wavelengths near 1.3 μm. A low-noise fiber optical amplifier is a strongly desired component for many of these systems. We have investigated two configurations for Raman amplification in silica fibers at 1.3 μm. The first is to generate the third Stokes order at 1240 nm in a cascaded Raman laser pumping with a Nd³⁺ fiber laser at 1060 nm, and then pumping a separate length of silica fiber to achieve amplification at 1.3 μm. This has the advantages of separated optimization of the Raman laser and amplifier sections, choosing between co- and counter-propagating amplification, and the ability to achieve distributed Raman amplification in a standard silica transmission fiber. The second configuration is to write highly reflective Bragg fiber gratings in a section of silica fiber through the first three orders, thereby increasing the circulating power at the third Stokes frequency, and then inject a 1.3 μm signal (4th Stokes) through this resonant structure