Abstract

The erbium doped silica fiber amplifier for the 1.55μm telecommunications has now become a well established research laboratory tool. It offers high gain, high efficiency, low noise, low cross-talk, and high saturation power. It has been used in both land and under-sea systems demonstrations, and is commercially available from a number of manufacturers. In distribution experiments splits of up to 39 million ways have been demonstrated for only two stages of amplification [1]. In short it has revolutionised thinking on future optical fibre networks. Unfortunately the vast majority of current operational systems are deployed in the 1.3μm window, and some fiber designs may prohibit upgrading to 1.55μm. A similar amplifier for 1.3μm has been much more elusive. Examination of the observed energy levels of the trivalent rare-earth ions reveals three principal candidates; neodymium with a known laser transition around 1.32μm, praseodymium with known laser transitions but not until very recently at 1.3μm, and promethium with known laser transitions at 0.933μm and 1.098μm, but not around 1.3μm. Promethium is radioactive and has not been studied in fibers, leaving two practical possibilities for fiber amplifiers for 1.3μm.

© 1991 Optical Society of America