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This paper reports on transient processes and cross talk (cross modulation) in an O-band (1260 – 1360 nm) bismuth-doped phosphosilicate fibre amplifier. Times characterising dynamic parameters of the amplifier at a pump wavelength of 1.23 μm have been determined experimentally. Data have been obtained on the effect of the modulation frequency Ω of one of the channels in the range 10 Hz to 1 MHz on the cross-talk intensity in another channel. The data, in combination with numerical calculation results, show that the cross talk in the Bi-doped fibre amplifier is insignificant at modulation frequencies Ω above 100 kHz. Our results demonstrate that O-band Bi-doped fibre amplifiers are potentially attractive for practical application in multichannel high-speed data transmission systems.

We have studied polarised luminescence of bismuth active centres in germanosilicate glasses. The 1.4-μm luminescence components with orthogonal polarisation states under excitation with linearly polarised light at λ = 1.26 μm have been shown to differ in intensity. The degree of polarisation reaches ∼0.12. Increasing the concentration of bismuth active centres leads to a decrease in the degree of polarisation of luminescence in the range studied.

This paper presents a study of anti-Stokes luminescence in optical fibres with a bismuth-doped ~50%GeO2 – 50%SiO2 glass core under IR excitation. The anti-Stokes luminescence intensity has been measured as a function of temperature in the range 77 – 300 K. From these data, we have evaluated the activation energy for the thermal quenching of anti-Stokes luminescence in the visible and IR spectral regions. A mechanism of anti-Stokes luminescence in this type of optical fibre has been proposed.

Using a bismuth-doped aluminosilicate fibre laser tunable in the range 1130–1210 nm, we have examined the effect of pump wavelength on the gain spectrum of bismuth-doped phosphosilicate fibres in the range 1220–1400 nm. At a pump wavelength of 1195 nm, we obtained a peak gain wavelength of 1300 nm, which is near the centre of the standard range for O-band transmission (1270–1320 nm) in fibre-optic communication links, in particular between data centres. Using a bismuth-doped phosphosilicate fibre amplifier pumped at 1195 nm, we have demonstrated that the transmission distance for a signal from a semiconductor laser diode directly modulated at 25 Gb s−1 [on – off keying (OOK) modulation] can be increased for G.652 fibre from the standard 10 to 80 km or even more.

A single-mode fibre based on bismuth-doped germanosilicate glass with a high germanium concentration is considered as an active medium of a laser continuously tunable within the range 1.65 – 1.8 μm. The laser scheme included a broadband ring cavity, and the laser wavelength was controlled by an external plane diffraction grating in the Littrow configuration. For a pump power of 300 mW at a wavelength of 1.564 μm, the maximum output laser power was 15 mW in the zero diffraction order and 6 mW at the fibre output.

We have studied the luminescence properties of optical fibres with a bismuth-doped alumino- and phosphosilicate glass core under two-step excitation and obtained new experimental data on the properties of luminescence centres in such fibres.

We have studied UV excitation spectra of IR luminescence in bismuth-doped glasses of various compositions and obtained energy level diagrams of IR-emitting bismuth-related active centres (BACs) associated with silicon and germanium atoms up to ~5.2 eV over the ground level. A possible energy level diagram of the BACs in phosphosilicate glass has been proposed. The UV excitation peaks for the IR luminescence of the BACs in the glasses have been shown to considerably overlap with absorption bands of the Bi3+ ion, suggesting that Bi3+ may participate in BAC formation.

Using bismuth/erbium-doped optical fibre, we have fabricated the first optical amplifier with a gain of in a wide spectral range , which covers the C-, L- and U-bands.

We have demonstrated the first superluminescent IR source based on bismuth-doped high-germania fibre. Its main output characteristics are as follows: centre wavelength, ; emission bandwidth, at an output power of ; optical efficiency, .

We report the first bismuth-doped fibre amplifier operating between 1600 and 1800 nm, which utilises bidirectional pumping (co-propagating and counter-propagating pump beams) by laser diodes at a wavelength of 1550 nm. The largest gain coefficient of the amplifier is 23 dB, at a wavelength of 1710 nm. It has a noise figure of 7 dB, 3-dB gain bandwidth of 40 nm and gain efficiency of 0.1 dB mW-1.

This paper compares the optical properties of bulk bismuth-doped Mg ? Al silicate glasses prepared in an iridium crucible to those of optical fibres prepared by the powder-in-tube method and having a core identical in composition to the glasses. The bulk glasses and fibres are shown to be similar in luminescence properties. The optical loss in the fibres in their IR luminescence band is about one order of magnitude lower than that in the crucible-melted glasses. The level of losses in the fibres and their luminescence properties suggest that such fibres can be made to lase near 1.15 ?m.

The first fibre preforms with a Pb-doped silica core, free of other dopants, have been produced using chemical vapour deposi- tion. The preforms have been used to fabricate holey optical fibres. The spectroscopic properties of the fibres have been studied in detail in the range 400 - 1700 nm: we have measured the optical loss, constructed a three-dimensional luminescence excita- tion - emission graph and determined the decay time for the major luminescence peaks.

We have demonstrated the first superfluorescent fibre source emitting in the 1.34 ?m range. In a double-pass configuration with an amplifier, its output power is 48 mW under pumping at ? = 1240 nm. Its emission spectrum has a nearly Gaussian shape, with a full width at half maximum of 26 nm at the highest pump power.

The Bi-doped fiber lasers operating at wavelengths of 1280 nm, 1330 nm, 1480 nm, and 1500 nm with a maximal output power of up to 2 W and a slope efficiency of 14 – 25% have been demonstrated for the first time. We have also investigated the influence of the doping concentration (GeO2 and P2O5) on the optical and laser generation properties of Bi-doped phosphogermanosilicate fibers.

We have studied the optical properties of lightly bismuth doped (≤0.002 mol %) germanate glasses prepared in an alumina crucible. The glasses are shown to contain bismuth-related active centres that have been identified previously only in bismuth-doped fibres produced by MCVD. With increasing bismuth concentration in the glasses, their luminescence spectra change markedly, which is attributable to interaction between individual bismuth centres.

Bi- and Er-codoped germanosilicate optical fibers have been fabricated and studied as a potential gain medium for fiber-based devices operating in the near infrared region. A broadband optical amplifier operating in the wavelength range from 1515 to 1775 nm has been realized using the developed bismuth- and erbium-codoped fibers. The 15 dB small-signal gain band covers 260 nm when pumped by a laser diode at 1460 nm with an output power of 350 mW.

We report the first cw bismuth — germanium codoped silica fibre laser with an output power above 20 W at 1460 nm and 50% optical efficiency. The laser operates on a transition between energy levels of bismuth-related active centres associated with silicon. The incorporation of a small amount (~5 mol %) of germanium into the core of bismuth-doped silica fibre has little effect on its luminescence spectrum but reduces optical losses, which limit the laser efficiency.

Optical fibre preforms and fibres with a bismuth-doped silica core containing no other dopants have been fabricated by the powder-in-tube technique. The optical loss has been measured for the first time in such fibres in a wide spectral range, from 190 to 1700 nm. We have studied the luminescence of active bismuth centres and the luminescence lifetime for some of their bands in both the preforms and the fibres drawn out from them.

We demonstrate the first bismuth-doped fibre amplifier operating in the second transmission window of silica-based fibres. At a pump power of 460 mW and pump wavelength of 1230 nm, its gain reaches 24.5 dB at 1320 nm, with a gain bandwidth of 37 nm, saturation power near 10 mW, and noise figure of 5 dB.

A new process for bismuth doping of optical fibres is proposed in which the dopant is introduced into a thin layer surrounding the fibre core. This enables bismuth stabilisation in the silica glass, with no limitations on the core composition. In particular, the GeO2 content of the fibre core in this study is 16 mol %. Spectroscopic characterisation of such fibres and optical gain measurements suggest that the proposed approach has considerable potential for laser applications.

Lasing in bismuth-doped optical fibres in the range 1470–1550 nm has been demonstrated for the first time. The gain media were Bi-doped phosphogermanosilicate and, for the first time, germanosilicate glass fibres. The gain spectrum of the phosphogermanosilicate fibres extends from 1300 to 1550 nm, the range which can be used in next-generation optical fibre communication systems.

Structural and spectroscopic properties of the pristine and γ-irradiated Bi-doped KCl and SrF2 crystals grown by the Bridgman technique were studied. New emission bands in the visible and near IR regions from the irradiated crystals were observed. An origin of optical centers responsible for near IR luminescence is discussed.

The effect of annealing temperature on the luminescent properties of bismuth-doped fibers bleached by 532 nm laser radiation was investigated. The photoluminescence (PL) measurements were performed in pristine and photobleached samples which were thermally annealed at various temperatures ranging from 100 to 900 °C and slowly cooled. We observed that the intensity of the PL band at 1700 nm in the photobleached fibers recovered its pre-bleached level. Moreover, it was shown that a significant increase of the PL level could be achieved using the special annealing regime. Thereby, we obtained the experimental evidence of a thermally activated recovery process of the PL intensity showing that photoinduced changes of PL in bismuth-doped fibers are completely reversible. The mechanism of the thermal recovery of the PL is discussed.

CW lasing of a Bi-doped germanosilicate fibre in a wavelength range that covers the spectral region between the emission bands of Er and Tm fibre lasers has been demonstrated for the first time.

Bismuth-containing quartz-like glasses (BCQGs) were synthesized by an impregnation of the silica porous glasses (PGs) with Bi(NO3)3 aqueous solution. Then the samples were sintered at the temperatures T from 700 °C to ≥ 1500 °C up to closing the pores. Characterization of BCQGs was carried out using the UV-VIS-NIR spectroscopy and IR spectroscopy. The absorption and luminescence properties of the BCQGs are discussed. It is shown that the growth of absorption in the short-wave region is characteristic for BCQGs. IR spectra confirmed the presence [BiO3] and [BiO6] units and α – Bi2O3 phase in BCQGs. The spectral dependences of the luminescence and excitation of the luminescence of the synthesized glass depending on their thermal prehistory were investigated. For the first time, 3dimensional luminescence spectra have been obtained for BCQG.

A meaningful increase in the number of NIR emission centers was experimentally observed in bismuth-doped multicomponent silicate glasses additionally doped with germanium dioxide. The emission and excitation spectra of the glass sets were monitored and compared with the spectra of radiative oxygen-deficient centers in vitreous silica and germania.