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AU712728B2 - Amplifying optical fibre - Google Patents
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AU712728B2 - Amplifying optical fibre - Google Patents

Amplifying optical fibre Download PDF

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AU712728B2
AU712728B2 AU56170/96A AU5617096A AU712728B2 AU 712728 B2 AU712728 B2 AU 712728B2 AU 56170/96 A AU56170/96 A AU 56170/96A AU 5617096 A AU5617096 A AU 5617096A AU 712728 B2 AU712728 B2 AU 712728B2
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Australia
Prior art keywords
fibre
amplifying
transmission material
species
light
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AU56170/96A
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AU5617096A (en
Inventor
Christian Le Sergent
Dieter Weber
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Alcatel Lucent NV
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Alcatel NV
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Description

'Ki:-i l P/00/011 28/5/91 Regulation 3.2
AUSTRALIA
Patents Act 1990 4 a.
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "AMPLIFYING OPTICAL FIBRE" The following statement is a full description of this invention, including the best method of performing it known to us:- 2 This invention relates to an amplifying optical fibre.
Such a fibre can be used to constitute an optical amplifier or an optical transmitter. It is conventionally constituted by a vitreous transmission material such as silica or a fluorinated glass. This medium is chosen so as to have a very low absorption coefficient for a light to be amplified as it is guided through the fibre. The approximate wavelength of the light is typically 1,300 or 1,550 nm. An amplifying species is incorporated in the core so as to constitute therein active centers in which the amplification process takes place. It is conventionally constituted by erbium ions or praseodymium ions dissolved in the transmission material.
It has been proposed to associate with this amplifying species an auxiliary species capable of enhancing the performance of an amplifier implemented using such a fibre. The amplifier performance then depends upon both the nature of the transmission material and the chosen concentrations of the amplifying and auxiliary 15 species. It includes in particular an efficiency spectral range, a pump light operating radiation efficiency, and a net amplifier gain which results not only from the intrinsic amplifying capabilities of the amplifying species but also from complex phenomena such as light absorption and deexcitation of the material through interaction with the surrounding materials constituted by the transmission material and the amplifying 20 species.
Furthermore, the transmission material must allow the industrial manufacture of the fibre.
,o More particularly, it has been proposed to enhance the performance of the amplifier using the following auxiliary species: A1 2 0 3 La 2 0 3 Yb 2 03 and P 2 Dieter Weber proposed an auxiliary species constituted by aluminium fluoride
AIF
3 and forming a complex with an amplifying species constituted by neodymium fluoride NdF 3 or praseodymium fluoride PrF 3 For more information on this topic, the following documents may be consulted: C.C Larsen -Al-La-Doped Amplifier fiber for extremely low Hydrogen Sensitivity- Proceedings of the 1 9th European Conference on Optical Communication ECOC 93 Montreux 1993.
CA991670121: 3 Laser Focus December 92 p. 13 German patent application no. 43 06 933.9 M. Nakazawa et al. Lanthanum codoped Erbium fiber amplifier Electronics Letters 6th June 1991 V27 N12.
According to the invention there is provided an amplifying optical fibre comprising a core surrounded by an optical cladding, a main constituent of the core being a transmission material having low losses for a light to be amplified as it is guided through the fibre, other constituents of the core being: an amplifying species forming active centers distributed in the transmission material and having fluorescent properties for amplifying said light; and an auxiliary species distributed in the transmission material and forming bonds with said active centres so as to optimise the fluorescent properties of said amplifying species, for amplifying said light; wherein said auxiliary species are bonded and surround said active centers to thereby form host particles constituting a distinct phase composition dispersed in said transmission material.
roeO :The invention is further described, by way of example only, with reference to the accompanying figure.
This figure shows an amplifying optical fibre according to the invention.
0: Referring to the figure, the fibre comprises as a core 1 surrounded by an optical cladding 2. Said transmission material constitutes the core. A material having the same basic composition but using different dopants constitutes the cladding.
The host particles are shown in 3.
The fibre can be manufactured from known materials using known techniques.
According to a first manufacturing possibility, the particles can be manufactured S beforehand. The amplifying species and the auxiliary species are for this purpose dissolved together and the glass or solid compound thus obtained is ground so as to obtain particles of appropriate size. The particles are incorporated and dispersed in the transmission material during one of its manufacturing stages.
CA99167012.2 4 According to a second manufacturing possibility, the amplifying species and the auxiliary species are incorporated in the transmission material at a temperature that is sufficient to allow a dissolution of the two species. The composition of the transmission material and/or the concentration of the auxiliary species are chosen so that a cooling stage, optionally associated with an intermediate-temperature heat treatment, produces a distinct phase constituted by submicronic particles comprising both the amplifying species and the auxiliary species.
Common processes are then used to obtain a preform from the transmission material containing the particles and the material which is to constitute the cladding. Finally, the fibre is formed by drawing said preform.
In one embodiment of the invention, said particles have dimensions lying the range 3 to 500 nm and, for instance, diameters lying in the range 10 to 100 nm. The indicate dimensions are measured along transverse directions to the length of the fibre.
These dimensions are chosen much lower than the wavelength of the light to be amplified so that the particles that are dispersed in the core of the fibre may not significantly diffuse said light.
In a second embodiment of the invention, said particles have dimensions lying in the approximate range 600 to 1,100 nm. The difference between the refractive index of the host particles and that of the transmission material is then small enough not to produce scattering losses greater than 1 dB/m at the wavelength of said light. The difference in refractive indices typically lies in the vicinity of 0.04.
9These dimensions are chosen so that the light to be amplified and/or the pump light may i: be inwardly reflected several times in such a particle when the light penetrates therein.
More precisely and in relation t the scattering losses, the main parameters are as follows: the radius a, the refractive index n, the concentration in active species, the spatial frequency of the particle deemed to be spherical, the radius r and the refractive index no of the core, and the length of the fibre.
These parameters are generally adjusted so that the light scattering losses do not exceed a level of around 1 dB for the length used.
The losses are defined by a coefficient a acd/m =10 Q.M.a 2 .r 2 /L(10) (1) where Q is the scattering coefficient Q x ((m2 1 (2) is the Naperian logarithm of ten, with M number of particles per km of fibre x 2 n a n 0 o/ A, wavelength of the light used.
m no/n, The formula can only be strictly applied when x 1; it is given here as an approximation.
Some examples of preparation modes for a preform, from which an optical 15 fibre according to the invention can be obtained by hot drawing, will now be given.
Example 1.
Production of praseodymium-doped silica fibers for amplification at 1,300 nm.
It is known that, in a silica medium, multiphonic deexcitation does not allow a sufficient lifetime for the active level 1 G 4 This lifetime however reaches 258 ,ts in a o.20 LaF 3 medium (lanthanum fluoride).
An example of preparation is thus as follows: a) production of a lanthanum fluoride powder doped with Spraseodymium fluoride using the common techniques of coprecipitation of an aqueous chloride solution by hydrofluoric acid.
calcination in neutral gas atmosphere at around 950C.
grinding by ultragrinder so as to obtain particles having a diameter in the vicinity of 50 nm.
b) mixing 2% of said powder, measured in weight, with synthetic silica powder of 50 nm average particle size doped with 5 to 30% of germanium or 2 to 7% of aluminium. A silica commercially known as "fumed silica" and prepared by oxidation or flame-hydrolysis of SiCI may for instance be used.
c) precompaction in the form of a porous cylinder followed by drying and densification by progressive heating at temperatures lying in the range 1,000-1,400C under an atmosphere constituted by an oxygen-helium-chlorine mixture under commonly applied conditions for the production of porous preforms for optical fibers.
d) the transparent rod obtained, having an approximate diameter of 8 mm and an approximate length of 10 cm is ground and polished, and then associated with tubes of commercial synthetic silica by successive sleeving-drawing-sleeving operations so as to achieve the desired core diameter and the desired outer diameter.
A preform having an approximate diameter of 30 mm is thus obtained. During the final fibering operation, the preform is drawn under conventional conditions to produce a fibre having a diameter of 125 us and a core radius of around 3 A low fibering temperature is preferentially chosen.
In this example 1, the transmission material is silica and the auxiliary species is lanthanum fluoride. The auxiliary species is doped with praseodymium as the 15 amplifying species to constitute the material of the host particles.
Example 2.
Production of erbium-doped silica fibers for amplification at 1,550 nm.
When implementing wavelength-division multiplexing, it is desirable to use a fa amplifying fibers having amplifying properties that are little dependent upon the exact wavelength used in the window centered at 1,550 nm.
An example of preparation is as follows: a) production of a submicronic amorphous lanthanum fluoride powder doped with about 3% erbium fluoride.
b) production of a gel by addition of 2 g of said powder and vigorous agitation in a suspension at 40C comprising: 150 cm 3 of water cm 3 of ethanol g of aluminium chloride g of submicronic synthetic silica commercially known as "fumed silica".
The gel is poured into polymer tubes as it sets so as to prevent it from clinging to the walls.
c) drying with all the usual precautions for this type of material, in particular in relation to the very progressive temperature rises (around 0,2C per minute) and the length of the plateaux (around ten hours).
d) additional drying and densification in the temperature range of 900-1,400C under an atmosphere constituted by a mixture of chlorine oxygen and helium e) grinding-polishing of the glass cylinder obtained in d f) production of a preform ready for fibering through successive sleeving and drawing operations using silica tubes having a 1-2% fluorine concentration, sufficient to guarantee proper guiding of the light.
In this example 2, the transmission material is silica and the host particle material is erbium-doped lanthanum fluoride.
SExample 3.
Production of chalcogenide glass fibers for amplification at 1,300 nm.
Glasses composed of La 2
S
3 -Ga 2
S
3 mixtures can be doped with the chemical o: elements Pr 3 1 or Dy 3 which in this type of matrix have an extraordinary fluorescence quantum efficiency, close to ten times greater than values measured in fluorinated compositions of the ZBLAN type.
Such glasses are unfortunately very sensitive to crystallisation and very difficult to fibre.
A solution to this problem consists in: a) preparing a La 2
S
3 -Ga 2
S
3 glass doped with 30,000 ppm of praseodymium or dysprosium.
b) reducing the glass to submicronic particle size c) putting the glass in suspension with a concentration close to 3% in a core composition based on arsenic disulfide at a temperature of 800C in a sealed funnel.
d) letting it cool so as to obtain a core rod having the same size as in the previous examples.
e) performing sleeving and drawing operations as in the previous examples.
In this example 3, the transmission material is arsenic disulfide and the host 8 particle material is lanthanum-gallium sulfide doped with praseodymium or dysprosium.
In view of the proportions and other indications given in relation to examples 1 to 3, two other examples can now be described more succinctly.
Example 4.
A host particle material constituted by lanthanum sulfide La 2
S
3 and doped with praseodymium sulfide Pr2S3, and a transmission material constituted by gallium and lanthanum (Ga x La 2 .)S3 are prepared. These materials are reduced to particles having a diameter of around 50 nm, and then mixed. The mixture is sintered at a temperature that is approximately 1 OC greater than the glass transition temperature Tg of the transmission material. The core rod of the preform is thus formed.
Example A host particle material constituted by lanthanum fluoride LaF 3 and doped with 15 praseodymium fluoride PrF 3 and a transmission material constituted by a fluorinated glass known as ZBLAN (zirconium, barium, lanthanum, aluminium and sodium fluoride) are prepared. These materials are reduced to particles having a diameter of around 50 nm, and then mixed. The mixture is sintered at a temperature that is approximately 10C greater than the glass transition temperature Tg of the 20 transmission material. The core rod of the preform is thus formed.

Claims (7)

1. An amplifying optical fibre comprising a core surrounded by an optical cladding for guiding light, a main constituent of the core being a transmission material, other constituents of the core being: an amplifying species forming active centers distributed in the transmission material and having fluorescent properties for amplifying said light; and an auxiliary species distributed in the transmission material and forming bonds with said active centres so as to optimise the fluorescent properties of said amplifying species, for amplifying said light; wherein said auxiliary species are bonded and surround said active centers to thereby form host particles constituting a distinct phase composition dispersed in said transmission material.
2. A fibre as claimed in claim 1, wherein said host particles have dimensions transverse to the fibre that lie in the range 3 nm to 500 nm.
3. A fibre as claimed in claim 1, wherein said host particles have dimensions transverse t the fibre that lie in the approximate range 600 nm to 1,100 nm. S:
4. A fibre as claimed in claim 3, wherein the refractive indices of said host particles and of °oosaid transmission material have a mutual difference that is small enough not to produce scattering losses greater than 1 dB/m at the wavelength of said light.
5. A fibre as claimed in claim 4, wherein said difference in refractive indices lies in the vicinity of 0.04.
6. A fibre as claimed in claim 1, wherein said transmission material is silica and said 1° auxiliary material is lanthanum fluoride, said amplifying species being praseodymium or erbium in fluoride form. 25
7. A fibre substantially as hereinbefore described with reference to the figure of the accompanying drawing. DATED THIS THIRTEENTH DAY OF JUNE 1996 ALCATEL N.V (r
AU56170/96A 1995-06-29 1996-06-24 Amplifying optical fibre Ceased AU712728B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9507836 1995-06-29
FR9507836 1995-06-29

Publications (2)

Publication Number Publication Date
AU5617096A AU5617096A (en) 1997-01-09
AU712728B2 true AU712728B2 (en) 1999-11-11

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1764350A1 (en) * 2005-09-16 2007-03-21 Alcatel Method of manufacturing an optical fiber containing nanoparticles and a preform appropriate for its manufacturing

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4444844A1 (en) * 1993-12-16 1995-06-22 France Telecom New rare earth-doped glass-ceramic material

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4444844A1 (en) * 1993-12-16 1995-06-22 France Telecom New rare earth-doped glass-ceramic material

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1764350A1 (en) * 2005-09-16 2007-03-21 Alcatel Method of manufacturing an optical fiber containing nanoparticles and a preform appropriate for its manufacturing
WO2007031664A1 (en) * 2005-09-16 2007-03-22 Alcatel Lucent Method for making an optical fiber comprising nanoparticles and preform used in the manufacture of such a fiber
FR2890958A1 (en) * 2005-09-16 2007-03-23 Alcatel Sa PREFORM FOR MANUFACTURING AN OPTICAL FIBER COMPRISING NANOPARTICLES AND PROCESS FOR PRODUCING AN OPTICAL FIBER USING SUCH A PREFORM
US7657142B2 (en) 2005-09-16 2010-02-02 Alcatel Lucent Method for making an optical fiber comprising nanoparticles and preform used in the manufacture of such a fiber

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NZ286845A (en) 1997-04-24
AU5617096A (en) 1997-01-09

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