Single-frequency bismuth-doped fiber power amplifier at 1651 nm

Erbium doped fiber amplifiers play an important role in various applications, spanning from fiber communication to optical sensing. Unfortunately, their gain bandwidth is limited to telecom C- and L-bands (from 1530–1625 nm). The application of bismuth-doped fibers is a promising approach for optical signal amplification at longer wavelengths. In this paper, a bismuth-doped fiber power amplifier seeded with a 1651 nm single-frequency laser diode is presented and its performance is experimentally analyzed. This amplifier may be used to improve performance of systems for methane detection, e.g. those based on photoacoustic spectroscopy or in remote/stand-off configuration (methane has a molecular absorption line near to 1651 nm). Two configurations of the amplifier are demonstrated and in both cases an output power of more than 80 mW is obtained. Limitations of current design are discussed. The obtained results give good a perspective for simple and compact fiber amplifiers with output powers exceeding 100 mW in the spectral region of ∼1630–1750 nm. (letter)