The aim was to demonstrate an efficient optical fibre amplifier operating in the second transmission window based on novel halide glasses. The project proposes to achieve a Pr3+-doped and Nd3+-doped amplifier by translating the best halide glass and fluoride glass compositions into optical quality preforms which will then be fabricated into single-mode Pr3+-doped and Nd3+-doped fibre.
The principal objective of the research was to demonstrate a 1.3 um optical fibre amplifier based on engineered halide glasses exhibiting lower phonon energies than can be achieved with conventional material systems such as zirconiumbarium lanthanum aluminium sodium fluoride glass (ZBLAN). Such glasses will be developed within the time domain of the project and translated into active fibre geometries for device realization. The key issues in the research are the realization of a radically new generation of low phonon energy glasses and the engineering of these systems for enhanced stability of the amorphous phase. The translation of these glass systems into optimized fibre geometries is of paramount significance for optical generation and regeneration devices.
The research has produced the following results:
novel materials systems with peak phonon energies lower than ZBLAN have been realized;
rare earth incorporation in bulk form has yielded spectroscopic data within a new low phonon energy environment for use in the development of the 1.3 um amplifier;
translation of these new glass systems into fibre geometries has been carried out.
- Design of novel halide and chalco-halide glass hosts for Pr3+ ions as dopant, which will exhibit good glass stability combined with reduced multiphonon relaxation rates and exhibit good potential for use in fibres.
- Design of stable, low refractive-index glass hosts for Nd3+ion as dopant, which will be optimised to produce gain within the second window.
- Preparation of bulk glass samples for spectroscopic characterisation. In Pr3+-doped glasses particular attention will be given to fluorescence lifetimes, phonon sidebands and Raman spectroscopy to evaluate and model non-radiative decay process. In Nd3+-doped glasses attention will be focused on the position, width and shape of the emission and ESA curves being of utmost importance in realising an amplifier. Methods of suppressing the 1.06 um amplified spontaneous emission (ASE) will also be examined.
- Production of a matched glass pair for use as core and cladding in fibre geometry, with specific reference to the refractive index, viscosity and expansion coefficients.
- Optimisation of preform fabrication and fibre drawing methods so as to reduce losses in the Pr3+-doped fibres.
- Spectroscopic characterisation of Nd3+- and Pr3+-doped fibres; evaluation of the devices with respect to their gain curve and the available gain and efficiency in both small-signal and power amplifier regimes.
The key issue is the achievement of the next generation of second window optical fibre amplifiers which will form the basis for high performance commercial devices. Two routes have been adopted to realise this objective. New low phonon-energy halide glasses are being developed as hosts for Pr3+ which will increase the quantum efficiency and gain of the amplifier. At the same time, low refractive index glasses are being optimised as hosts for Nd3+ aimed at achieving high gain within the second window.
The success of this project in providing fibre amplification in the second transmission window of silica telecommunication fibres has clear commercial implications for the European communications industry. Furthermore, the development of a new generation of fluoride and halide glass will give the Community a lead in this key technology, which impinges on a range of important devices.
BH15 1TD Poole