The current state of the art in infrared Bi-doped fiber laser research is reviewed. The relevant fiber glass compositions and fiber technologies are introduced. Lasers operating on transitions ranging from 1.15 to 1.55 μm occurring in the bismuth active centers and their energy level schemes are discussed on the basis of the spectroscopic properties of these centers. Continuous-wave fundamental-mode power levels ranging from a few mW near 1.55 μm up to 16 W near 1.16 μm and 22 W near 1.46 μm have been demonstrated in recent years.

For the first time, 3-dimensional luminescence spectra (luminescence intensity as a function of the excitation and emission wavelengths) have been obtained for bismuth-doped optical fibers of various compositions in a wide spectral range (450-1700 nm). The bismuth-doped fibers investigated have the following core compositions: SiO₂, GeO₂, Al-doped SiO₂, and P-doped SiO₂. The measurements are performed at room and liquid nitrogen temperatures. Based on the experimental results, the positions of the low-lying energy-levels of the IR bismuth active centers in SiO₂- and GeO₂-core fibers have been determined. Similarity of the energy-level schemes for the two core compositions has been revealed.

It is now almost twenty-five years since the first Erbium-Doped Fiber Amplifier (EDFA) was demonstrated. Currently, the EDFA is one of the most important elements widely used in different kinds of fiber-optic communication systems. However, driven by a constantly increasing demand, the network traffic, growing exponentially over decades, will lead to the overload of these systems (“capacity crunch”) because the operation of the EDFA is limited to a spectral region of 1530–1610 nm. It will require a search for new technologies and, in this respect, the development of optical amplifiers for new spectral regions can be a promising approach. Most of fiber-optic amplifiers are created using rare-earth-doped materials. As a result, wide bands in shorter (1150–1530 nm) and longer wavelength (1600–1750 nm) regions with respect to the gain band of Er-doped fibers are still uncovered. Here we report on the development of a novel fiber amplifier operating in a spectral region of 1640–1770 nm pumped by commercially available laser diodes at 1550 nm. This amplifier was realized using bismuth-doped high-germania silicate fibers fabricated by MCVD technique.

Bismuth-doped optical fibers and fiber lasers operating in 1625–1775 nm range have been developed for the first time to the best of our knowledge. Now the existing bismuth-doped lasers, including the result presented in this Letter, can cover O, E, S, C, L, and U telecommunication bands. In addition, new data on the nature of the bismuth-related active center were obtained and discussed.

The light sources operating in the spectral range 1600-1800 nm are of great interest because of a number of potential scientific and practical applications. This stimulates a search for effective laser media for this wavelength region. Recent progress in the studying of bismuth (Bi)-doped fibers is related to the development of Bi-doped high-germania-core fibers for the mentioned wavelength region. This paper is concerned with the current state of the art in the research field of this kind of the laser-active fibers. The fabrication and spectroscopic properties of the Bi-doped high-germania-core fibers are described. The photo-induced bleaching and recovery stimulated by thermal treatment of luminescent centers in these fibers are presented. The review also includes the description of the basic parameters of the optical devices (continuous wave (CW) and pulsed lasers, amplifiers, superluminescent sources) developed using Bi-doped high-germania-core fibers.

Bismuth-doped fiber lasers operating in the range $1300–1470\mathrm{nm}$ have been demonstrated for the first time, to our knowledge. It has been shown that Bi-doped alumina-free phosphogermanosilicate fibers reveal optical gain in a wavelength range of $1240–1485\mathrm{nm}$ with pumping at 1205, 1230, or $808\mathrm{nm}$.