Optical: systems and elements – Optical amplifier – Optical fiber
Patent
1997-02-26
1999-08-10
Moskowitz, Nelson
Optical: systems and elements
Optical amplifier
Optical fiber
359342, 359343, 372 6, 372 40, H01S 317, H01S 306
Patent
active
059367628
DESCRIPTION:
BRIEF SUMMARY
This invention relates to doped optical waveguide amplifiers.
Optical waveguide amplifiers, and in particular optical fibre amplifiers, are used widely in the telecommunications industry.
An example of an optical fibre amplifier is the erbium doped fibre amplifier (EDFA) which operates in the so-called third telecoms window (wavelengths around 1500 nanometres (nm)). These devices are characterised by their high gain (around 30 decibels (dB)) achieved with limited pump power (less than 50 milliwatts (mW)), which means that pumping can be performed using a single laser diode unit.
However, in the important second telecoms window (wavelengths around 1300 nm), known optical fibre amplifiers operate with a much lower efficiency. The best performance reported so far has been obtained using trivalent Praseodymium (Pr.sup.3+) doped fluoride fibre amplifiers (PDFFAs), which achieve a small signal gain of about 23 dB with about 120 mW of pump from a single semiconductor laser diode unit. Operating the pump diode at high drive current to achieve this pump power can severely curtail the lifetime of the diode. This problem has limited the application of this amplifier unit.
Application of PDFFAs as high output power amplifiers using solid state neodymium-yttrium-lanthanum-fluoride (Nd:YLF) lasers as the pump source have achieved a higher operating efficiency than the diode pumped device. However, the use of an expensive solid state laser for pumping the fibre amplifier is far from ideal for many applications such as in-line optical fibre amplifiers.
It has been proposed to use dysprosium as a dopant in optical waveguide amplifiers. In EP-A-0570743, fluoride or silica (SiO.sub.2) glass fibres are doped with dysprosium (Dy.sup.3+) ions to provide a 1300 nm optical amplifier.
This invention provides an optical waveguide amplifier comprising a glass optical waveguide doped with dysprosium ions, the highest frequency phonon mode of the glass having an energy of less than 450 cm.sup.-1, in which the glass waveguide is doped with at least one rare earth co-dopant to decrease the lifetime of the .sup.6 H.sub.11/2 and/or .sup.6 H.sub.13/2 energy levels of the dysprosium ion. (cm is an abbreviation for centimetre.)
This invention also provides an optical waveguide amplifier comprising a glass optical waveguide doped with dysprosium ions, the glass not being a fluoride or silica glass, in which the glass waveguide is doped with at least one rare earth co-dopant to decrease the lifetime of the .sup.6 H.sub.11/2 and/or .sup.6 H.sub.13/2 energy levels of the dysprosium ion.
The invention recognises that the nature of the glasses previously proposed in dysprosium doped optical waveguide amplifiers can dramatically limit the performance of those amplifiers. By using glasses having either a low phonon energy or glasses having a high quantum efficiency (a quantity related to the phonon energy and/or type of glass), the efficiency of the Dy.sup.3+ dopant can be greatly improved.
The performance of the amplifier is improved by the inclusion of at least one rare earth co-dopant to decrease the lifetime of the .sup.6 H.sub.11/2 and/or .sup.6 H.sub.13/2 energy levels of the dysprosium ion. This can improve the efficiency of the amplifier.
Preferably the or a co-dopant is europium. Also, preferably the or a co-dopant is terbium.
Embodiments of amplifiers according to the invention can operate in the second telecoms window between 1280 and 1350 nm and can be easily pumped by a single semiconductor laser diode unit with a typical small signal gain in excess of 20 dB for 50 mW of pump power. Further embodiments involve the incorporation of another trivalent rare earth ion (example Ytterbium) as a sensitising agent, allowing the possibility of efficient 980 nm pumping.
Although the invention is applicable to bulk optical or planar waveguides, it is preferred that the waveguide is an optical fibre. This can improve the spatial overlap between the dopant, the signal to be amplified and the pump signal. In particular, it is preferred that the optica
REFERENCES:
patent: 3866142 (1975-02-01), Clive et al.
patent: 5240885 (1993-08-01), Aitken et al.
patent: 5295146 (1994-03-01), Gavrilovic et al.
patent: 5346865 (1994-09-01), Aitken et al.
Samson et al, Optics Letters, vol. 22, #10, pp. 703-705, May, 15, 1997; Abst. only herewith.
Hewak Daniel William
Ian Laming Richard
Payne David Neil
Samson Bryce Neilson
Moskowitz Nelson
University of Southhamton
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