CN1654981A - Method for amplifying light input signal in broadened optical bandwidth and optical amplifier - Google Patents

Abstract

A light input signal is input into a light wave-guide made of non-crystal material doped with rare earth elements in a method of amplifying light input signals on a wide bandwidth, said signal includes the wavelength sphere of at least 80nm and 160nm for the optimum. The pump light is provided to the light wave-guide to provide gain of light to the input signal to be amplified in the wave-guide and provides amplified light signals in the widened 80-160nm sphere, especially including light signals of one end and the other wavelengths.

Description

The method and the image intensifer of amplifying light input signal on the light belt of widening is wide

The application is one and divides an application that the application number of its original bill application is 00819894.2, and this original bill application lies in the International Application PCT/US00/20578 that entered country's stage on March 14th, 2003, and its international filing date is on July 28th, 2000.

Technical field

The present invention relates to the image intensifer field, more specifically, the present invention relates to comprise the image intensifer field of the light guide optical fiber of certain-length, wherein optical fiber has the response pump light and sends the active adulterant of fluorescence.

Background technology

The fiber amplifier (EDFA) that is mixed with erbium is widely used in commercial optical communication system, both as full optical repeater, also as prime amplifier.Coded information signal is being weakened by fibre loss afterwards greatly by very long telecommunication optical fiber (tens of kilometers are arranged usually), and the effect that is mixed with the fiber amplifier (EDFA) of erbium is amplified to rational power level with these signals exactly.The efficiency of EDFA has reached the best now, has reduced the requirement to pump power (very expensive).The noise performance of EDFA has further obtained optimization, so that the noise number now can be near theoretical limit 3dB.The gain flatness of best EDFA surpasses the wide tens of dB of tens of nano belt now.EDFA is designed to be able to make their gain seldom to rely on the polarization of input signal now.

The also very active field of EDFA is a gain bandwidth (GB).This gain bandwidth (GB) parameter is extremely important, because it finally determines the number of signals of the different wave length that can be amplified by given EDFA.Bandwidth is wide more, and the individual signal number that then can be exaggerated is big more, therefore can be big more by the bandwidth (signal bit of unit interval) that strict single fiber carries.Because matrix influence the spectrum of erbium ion, therefore a direct join will continue to study several host materials, comprise silica, and fluorphosphate glass and chalkogenide are attempted definitely a kind ofly can be Er ^{3+ 4}I _13/2→ ⁴I _15/2Change the matrix of the gain bandwidth (GB) that provides bigger.In silicon-based glass, bandwidth is divided into C band and L band usually.In approaching term, the C band is the spectra part that is lower than about 1565 nanometers, and so-called L band is the spectra part that is higher than about 1565 nanometers.The combination total bandwidth of C band and L band is near 80 nanometers, although should numeral be to obtain by two EDFA of series connection up to now.(for example referring to Y.Sun, et al., 80nm ultra-wideband erbium-doped silica fibre amplifier, Electronics Letters, Vol.33, No.23, November 1997, pp.1965-1967).Situation and fluozirconate matrix phase are together.(for example see S.Kawai, et al., Wide bandwidth andlong distance WDM transmission using highly gain-flattened hybridamplifier, Proceedings of Optical Fiber Communication OFC ' 99, PaperFC3, February 1999, pp.56-58).In tellurite optical fiber, total bandwidth approximately also is 80 nanometers, but can realize with a single fiber.(for example see Y.Ohishi, et al., Opticalfiber amplifiers for WDM transmission, NTT R ﹠amp; D, Vol.46, No.7, pp.693-698,1997; Y.Ohishi, et al., Gain characteristics of tellurite-basederbium-doped fiber amplifiers for 1.5 μ m broadband amplification, OpticsLetters, Vol.23, No.4, February 1998, pp.274-276.)

Fig. 1 represents a kind of example with standard EDFA structure 100 of an Er-doped fiber (EDFA) 110.Light signal is in one first optical isolator 120 and a wavelength-division multiplex (WDM) coupling mechanism 122 input Er-doped fibers 110.The optical pump signal that optical pumping source 124 sends is also in this WDM coupling mechanism is input to this Er-doped fiber 110.The amplification output signal that Er-doped fiber 110 sends is by 126 outputs of one second optoisolator.Optoisolator 126,120 is used for eliminating respectively from delivery outlet and enters reflection backward in the Er-doped fiber 110 and the reflection backward from Er-doped fiber 110 to the input port.As shown in Figure 1, can go out Er-doped fiber 110 towards the place ahead pumping, perhaps pumping goes out towards the rear, perhaps goes out towards the both direction pumping.Because the popularity of fiber gain medium, the gain that the structure of Fig. 1 produces surpasses big bandwidth.For example, the tellurite fiber of er-doped and the chalkogenide optical fiber of er-doped in the structure of Fig. 1, have been used.As Y.Ohishi, et al., Gain characteristics of tellurite-based erbium-dopedfiber amplifiers for 1.5m broadband amplification, Optics Letters, Vol.23, No.4, February 1998, pp.274-276 is described, uses tellurite fiber to produce the gain bandwidth (GB) of about 80 nanometers.

When this fibre-optical substrate is silicon-based glass, can not provide the gain that surpasses whole bandwidth (about 1525 nanometers are to 1610 nanometers) with a single fiber.As an alternative, need between two adjacent SPECTRAL REGION, produce gain, then will combine from the output that this attention obtains.A kind of conventional method that obtains the broad gain bandwidth (GB) is to use the amplifier of mixing, and wherein two or more amplifiers of being made up of different substrates couple together.These Amplifier Design become the gain spectral that complements each other can be provided, and therefore produce overall gain-bandwidth bigger than only with any one time.By connect a fluorine-based EDFA behind a silica-based EDFA, this method has successfully obtained confirmation, and this method has produced the 0.5-dB-bandwidth of 17 nanometers.(see P.E.Wysocki, etal., Dual-stage erbium-doped, erbium/ytterbium-codoped fiber amplifierwith up to+26-dBm output power and a 17-nm fiat spectrum, OpticsLetters, Vol.21, November 1996, pp.1744-1746.).Recently, two fluorine-based EDFA have been adopted identical notion.(see Y.Sun, et al., 80nm ultrawidebanderbium-doped silica fibre amplifier, Electronics Letters, Vol.33, No.23, November 1997, pp.1965-1967.)

Fig. 2 represents to have an example structure 200 of two EDFA 210 and 220.An EDFA is used to amplify C bandwidth (approximately 1525-1565 nanometer), and another EDFA (going up EDFA) is used to amplify L bandwidth (approximately 1565-1620 nanometer).These two EDFA 210,220 comprise pumping source (not shown) separately, and they use separately WDM coupling mechanism and Er-doped fiber coupling, as shown in Figure 1.The input signal of spaced apart a certain amount of different wave length is with WDM coupling mechanism 230 separated into two parts, amplified output signal combination in an output coupler 232.An input optoisolator 240 and an output optoisolator 242 are worked as described above.Because WDM coupling mechanism 230, the short signal of wavelength ratio 1565 nanometers is coupled in the following branch, propagates into C band EDFA 210, and the signal that wavelength ratio 1565 nanometers are big is coupled in the branch of top, propagates into L band EDFA 22.(in fact, between C band and L band, the narrow boundary belt of avoiding signal overlap in the both sides being arranged).For example, silica-based EDFA can be designed to have the L band of gain spectral smoothness in 0.5dB in the scope of 1568-1602 nanometer.This gain flatness can be partly by selecting suitable fiber lengths or adopting filtrator to obtain.These two kinds of methods all are known in this field.

C band EDFA 210 can perhaps be made of different optical fiber identical Er-doped fiber with L band EDFA 220, perhaps is made of different host materials.Difference, especially pumping wavelength, pumping structure are different with fiber lengths separately in design for C band and L band EDFA 210,220.

The upper limit of L band EDFA 220 is approximately 1610 nanometers.Some research institutions have done a large amount of effort and have come to increase this upper limit by adjusting host material.The difficulty that further increases this upper limit is exist the signal excitation state to absorb (ESA) about 1620 nanometers and for silex glass about 1610 nanometers for tellurium glass.This ESA constitutes undesirable loss of signal mechanism.According to these results, present silica-based (above-cited Y.Sun etc.) and the bandwidth of fluorine-based EDFA (above-cited S.Kawai etc.) record be approximately the 80-85 nanometer (that is, with the article of above-cited Y.Ohishi etc. in disclosed telluro EDFA bandwidth write down identical).

Summary of the invention

One aspect of the present invention be to provide a kind of on a light belt of widening is wide the method for amplifying light input signal.This method comprises the amorphous Y that is mixed with rare earth ₂SiO ₅These light input signals comprise first light signal and second light signal with second wavelength that at least one has first wavelength, and wherein second wavelength is greater than first wavelength.This method comprises optical waveguide is applied pump light, makes described waveguide provide the gain of light to light input signal, so that amplify described first light signal and second light signal at least.

In an embodiment of this method, non-crystalline material is the Y that is mixed with erbium ₂SiO ₅, second wavelength is approximately than long 160 nanometers of first wavelength.Perhaps, amorphous Y ₂SiO ₅Material also can be mixed with erbium and ytterbium.

In second embodiment of this method, this non-crystalline material is Lu ₃Al ₅O ₁₂, second wavelength is approximately than long 160 nanometers of first wavelength.

In the 3rd embodiment of this method, this non-crystalline material is Y ₃Ga ₅O ₁₂, second wavelength is approximately than long 140 nanometers of first wavelength.

In the 4th embodiment of this method, this non-crystalline material is Ca ₂Al ₂SiO ₇, second wavelength is approximately than long 130 nanometers of first wavelength.

In the 5th embodiment of this method, this non-crystalline material is Y ₃Sc ₂Ga ₃O ₁₂, second wavelength is approximately than long 130 nanometers of first wavelength.Perhaps, this amorphous Y ₃Sc ₂Ga ₃O ₁₂Material also can be mixed with erbium and ytterbium.Also or, this amorphous Y ₃Sc ₂Ga ₃O ₁₂Material also can be mixed with erbium and chromium.

In the 6th embodiment of this method, this non-crystalline material is Bi ₄Ge ₃O ₁₂, second wavelength is approximately than long 125 nanometers of first wavelength.

In the 7th embodiment of this method, this non-crystalline material is GdAlO ₃, second wavelength is approximately than long 125 nanometers of first wavelength.

In the 8th embodiment of this method, this non-crystalline material is SrY ₄(SiO ₄) ₃O, second wavelength are approximately than long 125 nanometers of first wavelength.

In the 9th embodiment of this method, this non-crystalline material is LiYF ₄, second wavelength is approximately than long 110 nanometers of first wavelength.

In the tenth embodiment of this method, this non-crystalline material is CaF ₂-YF ₃, second wavelength is approximately than long 110 nanometers of first wavelength.

In the 11 embodiment of this method, this non-crystalline material is YVO ₄, second wavelength is approximately than long 90 nanometers of first wavelength.

In the 12 embodiment of this method, this non-crystalline material is LiErYP ₄O ₁₂, second wavelength is approximately than long 80 nanometers of first wavelength.

Another method of the present invention be a kind of can be on the light belt of an expansion be wide the image intensifer of amplifying light input signal.This image intensifer comprises that an optical pumping source that optical pumping light is provided and one comprise a kind of optical waveguide that is mixed with the non-crystalline material of rare earth.This optical waveguide optical coupling receives the optical pumping light from optical pumping source.This optical waveguide receives the light input signal with a plurality of wavelength.These light input signals comprise that at least one first light signal with first wavelength and at least one have second light signal than second wavelength of the bigger wavelength of first wavelength.This pump light has a pumping wavelength and intensity in the pumping wave strong point, makes optical waveguide that the gain of light is provided, so that amplify described first light signal and second light signal at least.

In an embodiment of this device, non-crystalline material is the Y that is mixed with erbium ₂SiO ₅, second wavelength is approximately than long 160 nanometers of first wavelength.Perhaps, amorphous Y ₂SiO ₅Material also can be mixed with erbium and ytterbium.

In second embodiment of this device, this non-crystalline material is Lu ₃Al ₅O ₁₂, second wavelength is approximately than long 160 nanometers of first wavelength.

In the 3rd embodiment of this device, this non-crystalline material is Y ₃Ga ₅O ₁₂, second wavelength is approximately than long 140 nanometers of first wavelength.

In the 4th embodiment of this device, this non-crystalline material is Ca2Al ₂SiO ₇, second wavelength is approximately than long 130 nanometers of first wavelength.

In the 5th embodiment of this device, this non-crystalline material is Y ₃Sc ₂Ga ₃O ₁₂, second wavelength is approximately than long 130 nanometers of first wavelength.Perhaps, this amorphous Y ₃Sc ₂Ga ₃O ₁₂Material also can be mixed with erbium and ytterbium.Also or, this amorphous Y ₃Sc ₂Ga ₃O ₁₂Material also can be mixed with erbium and chromium.

In the 6th embodiment of this device, this non-crystalline material is Bi ₄Ge ₃O ₁₂, second wavelength is approximately than long 125 nanometers of first wavelength.

In the 7th embodiment of this device, this non-crystalline material is GdAlO ₃, second wavelength is approximately than long 125 nanometers of first wavelength.

In the 8th embodiment of this device, this non-crystalline material is SrY ₄(SiO ₄) ₃O, second wavelength are approximately than long 125 nanometers of first wavelength.

In the 9th embodiment of this device, this non-crystalline material is LiYF ₄, second wavelength is approximately than long 110 nanometers of first wavelength.

In the tenth embodiment of this device, this non-crystalline material is CaF ₂-YF ₃, second wavelength is approximately than long 110 nanometers of first wavelength.

In the 11 embodiment of this device, this non-crystalline material is YVO ₄, second wavelength is approximately than long 90 nanometers of first wavelength.

In the 12 embodiment of this device, this non-crystalline material is LiErYP ₄O ₁₂, second wavelength is approximately than long 80 nanometers of first wavelength.

Description of drawings

Below in conjunction with accompanying drawing these and other aspect of the present invention is described.

Fig. 1 represents that an example comprises the standard EDFA structure of an Er-doped fiber;

Fig. 2 represents that an example has the structure of two EDFA, and one of them EDFA amplifies the C band, and another EDFA amplifies the L band;

Fig. 3 represents amorphous YAG optical fiber and substitutes YAG optical fiber at the erbium that is mixed with various concentration with under 980 nanometers with about 45 amorphous lanthanums of going out of milli pumpings;

Fig. 4 represents that this amorphous YAG optical fiber and this amorphous lanthanum substitute the measurement of the fluorescence Spectra backward spectrum of YAG optical fiber;

Fig. 5 represent the erbium volumetric molar concentration increase to er-doped amorphous YAG and er-doped amorphous lanthanum substitute YAG forward and the influence of bandwidth backward;

Fig. 6 A represents the temporary transient decay (tension and relaxation) of fluorescence of the amorphous YAG optical fiber radiation of er-doped 1%;

Fig. 6 B represents the temporary transient decay (tension and relaxation) of fluorescence of the amorphous YAG optical fiber radiation of er-doped 5%;

Fig. 7 represents the influence of erbium concentration to the fast light (square marks in the lower curve) and the slower rays (the circular mark in the upper curve) of er-doped amorphous YAG optical fiber fluorescence;

Fig. 8 represents to be used to realize a kind of first structure of amplifier of first embodiment of method of the present invention;

Fig. 9 represents to be used to realize a kind of second structure of amplifier of second embodiment of method of the present invention;

Figure 10 represents a preceding L band amplifier that comprises the er-doped amorphous YAG optical fiber of single length;

Figure 11 representation class still but has a kind of amplifier architecture of the longer er-doped amorphous YAG optical fiber that is used as L band amplifier like the structure of Fig. 8;

Figure 12 represents a kind of structure of L band amplifier, and one of them er-doped amorphous YAG optical fiber is between two WDM coupling mechanisms, and these coupling mechanisms receive each pump signal, and both direction pumping forwards, backwards goes out the amorphous YAG optical fiber of er-doped;

Figure 13 represents a kind of structure that comprises the L band amplifier of two er-doped amorphous YAG optical fiber that are connected in series by a WDM coupling mechanism, wherein has the pump light of pumping second optical fiber before guiding into;

Figure 14 represents a kind of first er-doped amorphous YAG optical fiber that is connected in series by a WDM multiplexer and amplifier architecture of the second er-doped amorphous YAG optical fiber of comprising, wherein has the pump light of guiding back pumping second optical fiber into;

Figure 15 represents the 1/e fall time constant with the power efficiency of fluorescence of identical fluorescence decay curve measurement shown in the 6B from Fig. 6 A, and wherein the 1/e time constant is represented the mean value of fast and slow time constant;

Figure 16-the 23rd, the reproduction of accompanying drawing among International Patent Application PCT/US97/00466, the applying date of this patented claim is on January 9th, 1997, be disclosed on July 17th, 1997, international publication number is WO97/25284, its drawing and description are incorporated herein and are used to illustrate a kind of method of making a kind of optical fiber, be used to finish the present invention, wherein:

Figure 16 represents that a kind of optical fiber tubular stinger of making the method for optical fiber draws the synoptic diagram of an embodiment of system;

Figure 17 represents the principle according to WO97/25284, along an embodiment of opposite direction a kind of method of drawing optical fiber from cross the floating thawing thing of cold-peace;

Figure 18 represents the principle according to WO97/25284, an embodiment of a kind of method of drawing optical fiber in the cold thawing thing of the mistake from remain on the conical nozzle levitron;

Figure 19 represents floating and is melted in the typical cooling chart of 0.3cm diameter mullite (mullite) sample in the aeroacoustics levitron;

Figure 20 represents typical aluminium-silicon phasor;

Figure 21 represents an embodiment of a kind of method of drawing optical fiber the cold thawing thing of the mistake in remaining on the non-isothermal container;

Figure 22 represents a part unusual aluminium-silicon phasor of mullite near the behavior of melt temperature; And

Figure 23 represents to contain the typical tension test figure as a result of the glass optical fiber of mullite composition;

Figure 24 represents the fluorescence Spectra of er-doped crystalline aluminium garnet (LuAG).

Embodiment

The present invention relates to a kind of on the gain bandwidth (GB) of broad the method for amplifying optical signals.This method partial dependency uses a kind of optical fiber with broad fluorescence (fluorescent) bandwidth.More specifically, Containerless Research company (CRI) has developed a kind of by forming the method for almost not having the made of slime body optical fiber and small amount of sample under the balanced melting point of solid recently.(see J.K.R.Weber, et al., Glass fibers of pure and erbium orneodymium-doped yttria-alumina compositions, Nature, Vol.393,1998, PP.769-771; And Paul C.Nordine, er al., Fiber Drawing fromUndercooled Molten Materials, its international publication number is WO97/25284, is disclosed on July 17th, 1997).This international patent application is hereby incorporated by.The detailed description of this international patent application provides as the part of present specification.

This method comprises melts a kind of solid fully, forms the uniform liquid of a kind of composition being in or being higher than the balanced melting point of crystalline material place a little.In order to obtain to support the desired viscosity of fibre-optical drawing, cold excessively this liquid (it is following promptly to be cooled to its balanced melting point).Using the cold viscosity that increases is a key step in the method.Follow drawn glass fiber from the supercooled liquid of this viscosity.

An embodiment of this optical fiber synthetic method uses no container treatment technology, can avoid contacting the complex phase nucleation that the solids container wall produces, and allows deep cooling to the temperature that is lower than crystallization tendency material melting point.No container treatment technology has been eliminated contact exterior object (for example crucible bring liquid contamination).They can also be used for from the glass spheres of the synthetic diameter 2-3 millimeter of various oxidation materials.(for example see J.K.R.Weber, et al., Enhanced Formation of Calcia-GalliaGlass by Containerless Processing, J.Am.Geram.Soc.Vol.76, No.9,1993, pp.2139-2141; And J.K.R.Weber, et al., Aeroacoustic lebitation-Amethod forcontainerless liquid-phase processing at high temperatures, Rev.Sci.Instrumen., Vol.65,1994, pp.456-465).New optic fibre manufacture process has been applied to a variety of silicon dioxide (silica) that neither contain and has not also contained any other " network " formation thing by the typical glass optical fiber composition of traditional fiber manufacturing technology manufacturing.This method allows to generate and typically has a diameter from the optical fiber that the 10-30 micron reaches 1 meter.

A kind of can be Y by the prototype material of this method manufacturing ₃Al ₅O ₁₂Composition.These materials of discussing among the application are by using lanthanum (La), ytterbium (Yb) and/or erbium (Er) to substitute the remodeling of the component of yttrium (Y) atom formation in material.The potpourri that these materials are pressed constant weight by pure-oxide is synthetic, and these oxides are Y ₂O ₃, Al ₂O ₃, La ₂O ₃, Yb ₂O ₃, Er ₂O ₃, the weighting error of every kind of component accounts for 0.5 milligram of gross mass 0.5 gram greatly.The purity of pure-oxide is 99.999%, and is littler than 325 powder, can be from Cerac, and of Milwaukee, Wisconsin obtains.For containing Er ₂O ₃0.5 a kind of composition of mole % uses Yb ₂O ₃: Er ₂O ₃Equal " foundry alloy " weighing adulterant easily of 9: 1.The potpourri of these oxide components is melted in the Laser stove melter, at first melts and stir evenly the sample of 0.5 gram, obtains about 3 millimeters spheroid by the fragment that melts once more in the object then.(for example see J.K.R.Weber, et al., Laserhearth melt processing of ceramic materials, Rev.Sci.Instrum., Vol.67,1996, pp.522-524).These spheroids then by laser beam at an aeroacoustics suspension device (for example as J.K.R.Weber, et al., Aero-acoustic levitation-A method forcontainerless liquidphase processing at high temperatures, Rev.Sci.Instrumen., Vol.65,1994, described in the pp.456-465) or at a conical nozzle suspension device (as J.P.Coutures, et al., Contactless Treatments of Liquids in a LargeTemperature Range by an Aerodynamic Levitation Debice under LaserHeating, Proc.6 ^ThEuropean Symposium on Materials under MicrogravityConditions, Bordeaux, France, December 2-5,1986, pp.427-30; J.K.R.Weber, et al., Containerless LiquidPhase Processing of Ceramic Materials, Microgravity Sci.Technol., Vol.7,1995, pp.279-282; S.Krishnan, et al., Levitation apparatus for structural studies of high temperature liquids usingsynchrotron radiation, Rev.Sci.Instrum., Vol.68,1997, pp.3512-3518 is described) in be heated and obtain suspending and melt.

Under no container condition, the power supply that cuts off the heating laser beam makes the rapid cool to room temperature of fluid sample can prepare glass bead.Can be that 1600 ° of-1700 ° of K prepare glass optical fiber up to fluid temperature by the power that reduces the heating laser instrument, wherein liquid viscosity be enough to carry out the optical fiber traction.Then the tungsten filament tubular stinger is inserted rapidly and melt in the thing, and with the constant speed that the is approximately 100 cels traction optical fiber from this thawing thing of releasing.Above-mentioned part process prescription is at Paul C.Nordine, et al., among the Fiber Drawing from Undercooled Molten Materials, it is that publication number is the international patent application of WO97/25284, be disclosed in 1997NA July 17, disclose a part wherein at this.

Pure Y ₃Al ₅O ₁₂Crystal habit be well known that yttrium aluminum garnet or abbreviate YAG as." YAG " described here refers to crystalline material.Be mixed with neodymium ion (Nd ³⁺) be will prove the earliest and the most successful laser material.Neodymium-YAG (Nd:YAG) laser instrument can be bought 25 years more than, and they remain the most effective in the high and the most widely used laser instrument of power now.On the contrary, the Y that discusses here ₃Al ₅O ₁₂The amorphous optical fiber of composition will be known as amorphous YAG, by the alternative Y of lanthanum ₃Al ₅O ₁₂Optical fiber will be called as the YAG optical fiber that is substituted (or alternative by La) by the amorphous lanthanum.

YAG and the material of discussing here have two main difference.At first, material difference described herein is the glass material of amorphous because they are compared with YAG, and it is a kind of crystalline material.Secondly, the material of Lun Shuing contains lanthanum (La) atom here, ytterbium (Yb) atom, and/or erbium (Er) atom replaces Y ₃Al ₅O ₁₂Some yttriums (Y) atom in the composition.Material discussed here will be called as er-doped amorphous YAG, mix ytterbium amorphous YAG, and the amorphous lanthanum substitutes YAG or amorphous YAG.This term comes from different purposes, is used for the erbium atom, and ytterbium atom and lanthanum atom substitute yttrium atom.Erbium atom and ytterbium atom substitute the optical activity adulterant in the host glass material.

Yt, lanthanum, erbium and ytterbium are " rare earth " family elements, and promptly these Atom of Elements are 21,39,57 to 71.These rare earth element have+3 atomicity, although some rare earth element especially ytterbium also have+2 atomicity.The general chemical formula of synthetic all material can be written as RE in this instructions ₃Al ₅O ₁₂, wherein the subscript of " RE " " 3 " is represented the total amount of Y, La, Er, Yb.These glass beads and optical fiber contain lanthanum and or erbium, and in air, pure argon or purity oxygen, make.Although be described, be appreciated that also and can use other rare earth materials at the rare earth element of front at this.

The chemical constitution that substitutes the material of the synthetic amorphous YAG composition of yttrium atom with lanthanum atom, erbium atom and ytterbium atom is provided by Table I:

Chemical constitution, mole percentage					The glass material that forms
							Al 2O 3	?? Y 2 O 3	???La 2O 3	???Er 2O 3	???Yb 2O 3	Optical fiber	Spheroid
62.5	??37.5	???0	???0	???0	??X	????X
							62.5	??37.49	???0	???0.01	???0	??X
62.5	??37.45	???0	???0.05	???0	??X	????X
							62.5	??37.4	???0	???0.1	???0	??X	????X
62.5	??37.2	???0	???0.3	???0	??X	????X
							62.5	??37.0	???0	???0.5	???0	??X	????X

??62.5	??36.5	????0	????1.0	????0	????X	????X
							??62.5	??35.5	????0	????2.0	????0	????X	????X
??62.5	??32.5	????0	????5.0	????0	????X	????X
							??62.5	??29.5	????0	????8.0	????0	????X	????X
??62.5	??12.5	????12.5	????12.5	????0	????X	????X
							??62.5	??17.75	????17.75	????2.0	????0	????X	????X
??62.5	??17.75	????11.75	????8.0	????0	????X	????X
							??62.5	??32.0	????0	????0.5	????0.5		????X

Characteristics the most attracting of that mix and alternative amorphous YAG material are that they can be mixed with the very Er of high concentration ³⁺, Yb ³⁺Or other rare earth ions.The Cmax that can obtain in glass depends on Er ₂O ₃Dissolution rate in glass.If rare earth oxide is too high in the concentration that glass melts in the thing, the crystalline oxides particle precipitation in the substrate so.These crystalline particles are normally harmful to laser instrument with this material and amplifier performance.Limit some materials especially in the silicon-based glass second factor of concentration of dopant be the formation of the dopant ions bunch of dissolving in the host material, this formation occurs under the concentration of concentration less than harm oxide particle normal concentration.

Do not resemble and be evenly distributed in the matrix the erbium ion, the erbium ion of cluster is subjected to a kind of harmful process of known cross-relaxation.(for example see J.L.Wagener, et al., modeling ofion pairs in erbium-doped fiber amplifiers, optics Letters, Vol.19, March1994, pp.347-349).By this process, when two ions are subjected to optical excitation and become metastable fixed (laser instrument) state, one of them ion has lost its energy rapidly, has given the another one ion energy, has caused not wishing the population inversion loss that occurs and the huge minimizing of the gain of light.In silicon-based glass, before this effect became significantly, operable maximum erbium concentration was approximately 100/1000000ths (ppm) mole Er ₂O ₃For fear of this influence, most silica-based optical fibers laser instruments and amplifier use the Er that is less than the 500ppm mole ₂O ₃Than higher, wherein the concentration of several thousand ppm is acceptable to this numeral in fluorine-based optical fiber.(for example see J.S.Sanghera, et al., Rare earth doped heavy-metal fluoride glass fiber, inRare Earth Doped Fiber lasers and Amplifiers, M.J.F.Digonnet, Ed., MarcelDekker, Inc., N.Y., 1993).In tellurite fiber, this numeral is several thousand ppm, and promptly a molar percentage is a few tenths of.(see Y.Ohishi, et al., Gain characteristics oftellurite-based erbium-doped fiber amplifiers for 1.5-μ m broadbandamplification, Optics Letters, Vol.23, No.4, Febreary 1198, pp.274-276).The main consequence of these concentration limit is that ion so many on the unit length can both be combined in the optical fiber, and long optical fibers is used to make useful device, and cost height, volume are big like this.For example, a kind of typical silica-based EDFA requires the doped fiber of tens of meters length.

People are to being mixed with Er ³⁺The early stage experimental study of spectrum property of new glass material.A purpose of these researchs is to add new several optical properties to these materials, or spheroid or optical fiber form.Especially, this research is to guide the absorption of material and radiation cross section into whether to have bunch (cross-relaxation) and in such concentration, the bandwidth of fluorescence spectrum (it reflects the gain bandwidth (GB) of this material).

For the purpose of optical signature, the er-doped amorphous YAG optical fiber that length is short inserts in the kapillary, then combines with UV slaking epoxy resin, then polishing.Four to five optical fiber with same matrix and erbium concentration are installed in identical kapillary usually.Prepare several kapillaries, wherein each all has several concentration (percent 0.5, Er of 1,2,5,8 moles ₂O ₃).These optical fiber expose.The external diameter of these optical fiber is approximately 30-15 micron or littler, and the length of optical fiber is about 5 millimeters or be approximately 10 millimeters after polishing.Two kinds of new oxide glass matrix components are tested, just amorphous YAG (Y ₃Al ₅O ₁₂, substitute Y with erbium) and the alternative YAG optical fiber of amorphous lanthanum, wherein 50% yttrium substitutes (La with lanthanum _1.5Y _1.5Al ₅O ₁₂, substitute La and Y with erbium).Measure for all, the pigtail shape fiber laser diode pumping that these optical fiber can be bought from the market with the luminous power of 980 nanometers, 50 milliwatts goes out.

By measuring the ratio of output and input pump power, suppose then that pumping is gone into to be coupled as 100% in the optical fiber, and, can measuring optical fiber absorb in each optical fiber end correction Fresnel (Fresnel) reflection (about 8.3%).Fresnel reflection is to calculate under the refraction coefficient of the supposition material situation identical with the refraction coefficient of crystal YAG, and this coefficient is approximately 1.8 under these wavelength.Can push over out absorption coefficient from these data _a, and absorb cross section σ _a=α _a/ N ₀, N wherein ₀Be the erbium concentration in the optical fiber.Observed mean value is σ in having several samples of two kinds of variable concentrations _a=2.4*10 ^-21Cm ²It can be 2.2*10 with standard value ^-21Cm ²The er-doped silicon optical fiber compare.

Fig. 3 is illustrated in the amorphous YAG optical fiber and the amorphous lanthanum substitutes the fluorescence Spectra of measuring in the YAG optical fiber, and wherein fiber lengths is 0.5-1.0 centimetre, and diameter is 30 microns, is mixed with the erbium of various concentration, goes out with about 45 milliwatt pumpings in 980 nanometers.These spectrums are measured from the place ahead, i.e. the fluorescence that this spectrum representative gives off according to the direction identical with the pumping outgoing direction of optical fiber.All spectrum all are wide, and are not subjected to the influence of the transformation line of er-doped crystal.This observation has confirmed the result that X-ray diffraction is analyzed, and it shows that the optical fiber that draws is amorphous from the supercooled liquid of YAG composition.(for example see J.K.R.Weber, et al., Glass fibers of pure and erbium orneodymium-doped yttria-alumina compositions, Nature, Vol.393,1998, pp.769-771).In the low optical fiber of erbium concentration, the characteristic that this stave reveals is: have lower powered Er in other oxide glasses usually ³⁺Fluorescence Spectra, promptly peak value is about 1530 nanometers, and flat flank is approximately 1550 nanometers.Under higher concentration, these characteristics become not obvious, and spectrum moves towards the long wavelength, because pump power is not enough to excite all erbium ions, ground state absorbs and filters out 1530-1550 nanometer bandwidth (C band).In these optical fiber, L band (wavelength is greater than 1565 nanometers) is more outstanding.The L band of this material is extremely wide.In 1 centimetre and 8% the optical fiber of mixing, the L band is widened 1653 nanometers.People have observed 3dB fluorescence bandwidth and reached 116 nanometers in 1 centimetre and doping 5%YAG optical fiber.Any intramatrical erbium of report changed bandwidth before this was higher than far away.As a comparison point, in the standard er-doped silica-based optical fibers of 1650 nanometers, power efficiency of fluorescence is usually from 1530 nanometer decline 50dB.On the contrary, in amorphous YAG optical fiber of the present invention, power efficiency of fluorescence only reduces about 12dB (see figure 3).This can be construed to a kind of fluorescence spectrum, and this spectrum is further widened the wavelength longer than er-doped silica-based optical fibers from the 20-40 nanometer.

Back fluorescence spectrum is illustrated among Fig. 4, has wherein represented the characteristics of C band, as expectation, but the also non-constant width of spectrum here.In 0.5 centimetre of YAG optical fiber of 8% of mixing, be 121 nanometers for the bandwidth of the observed the highest 3-dB of back spectrum.

Preceding and back fluorescence bandwidth all increases with the increase of concentration usually, as shown in Figure 5.Diamond is represented er-doped amorphous YAG, and circle represents that er-doped amorphous lanthanum substitutes YAG.Preceding and back fluorescence is represented by solid and open symbols respectively.In experimental error, these two kinds of materials all have identical substantially performance.

By in input pumping beam path, placing the acousto-optic modulator (acousto-optic modulator) of a 80MHz, pump intensity is modulated into the interim relaxation that about 20 milliseconds long square pulses with die-away time short (about 5 milliseconds) can be measured fluorescence.Follow interim decay with quick photodetectors register fluorescence of optical fiber radiation after each pumping pulse.For low concentration, the relaxation curve table reveals single index decay, as among Fig. 6 A for shown in the 1% er-doped amorphous YAG optical fiber.For higher erbium concentration, the relaxation curve no longer is a single index, but the exponential damping with time constant that increases in time.For 5% er-doped amorphous YAG optical fiber, this is illustrated among Fig. 6 B.This curve is constant τ in time ₁Begin decay.Change in time, this constant increases (attenuation slope), up to reaching asymptotic value τ in the lower end of die-away curve time constant ₂(compare τ ₁Greatly).

Another significant important results is that these optical fiber bunch are not influenced by erbium substantially among Fig. 6 A and the 6B, even under maximum concentration.If these bunches, the relaxation curve table reveals at first because cluster ion and very fast relaxation composition so, then because the slow component of non-one-tenth cluster ion.(for example see P.F.Wysocki, et al., Evidence and modeling of paired ions and otherloss mechanisms in erbiim-doped silica fibers, in SPIE Proceedings onFiber Laser Sources and Amplifiers IV, Vii.1789,1993, pp.66-79).In other materials, quick composition is the littler 2-3 numbers of poles (expecting that promptly it is that 100 microseconds are following) than the radiation lifetime usually.Each has the fact of observing this composition to show to exist in these two new matrix insignificant erbium ion bunch, its concentration to reach in amorphous YAG 80%, and this is approximately than there not being the high 600 times of bunch concentration in the silicon-based glass.

The life-span τ that from die-away curve, derives to all measurement of concetrations ₁And τ ₂Be plotted among Fig. 7.Quick composition (the τ of square representative ₁) life-span, circle is represented composition (τ at a slow speed ₂) life-span, on behalf of amorphous YAG matrix optical fiber and amorphous lanthanum, solid and open symbols substitute YAG matrix optical fiber respectively.Two all dull minimizings with the increase of erbium concentration of life-span are as usually observed in other matrix.Slow component τ ₂It is radiation lifetime.Approximately be 4 milliseconds the minimum radiation lifetime of measuring in 5% and 8% YAG optical fiber, and short life is 0.6-1.0 millisecond (also being in these materials).By contrast, be several milliseconds in present life-span, and in silicon-based glass, be generally the 8-10 millisecond as the erbium in the tellurium glass of commercial EDFA.

In order to estimate the relative performance of two kinds of materials better, Figure 15 has represented the 1/e damping time constant of the power efficiency of fluorescence measured from the fluorescence decay curve identical with 6B with Fig. 6 A.The 1/e time constant is represented the mean value of fast time constant and slow time constant, and in some sense, it provides the measurement mean lifetime (this mean lifetime is the dynamics and the saturated performance of part control amplifier especially) of erbium ion excited state.Figure 15 represents the 1/e life-span with the dull minimizing of erbium concentration increase, and the erbium in the lanthanum equivalent material has the life-span of weak point, although the difference of these two kinds of materials is in experimental error.Conclusion is that the erbium in two kinds of materials shows roughly the same bandwidth and identical life-span, and is more favourable a little than amorphous YAG.

Glass optical fiber is mixed with more than one rare earth ion, has utilized the interactional advantage of two or more doping machine matter sample material.For example, Er-doped fiber is mixed with Yb ³⁺, can pumping go out erbium ion near 1.06 microns.(for example, see J.E.Townsend, et al., Yb ³⁺Sensitised Er ³⁺Doped silica optical fibre with ultrahigh transfer efficiencyand gain, Electronics Letters, Vol.10, No.21,1991, pp.1958-1959).Reason is in some aspects pumping to be gone out about 1.06 microns EDFA (other Er-doped fiber devices), a kind of can be in more high-power down available optical maser wavelength cheaply, it is more favourable than the laser diode of 980 nanometers that are used as pumping source now and 1480 nanometers from the neodymium-doped fiber laser of commercial Nd:YAG laser or coating.Er ³⁺Can not show 1.06 microns absorption band, but Yb ³⁺Can.Be mixed with Er ³⁺And Yb ³⁺With pumping go out near in 1.06 micron fiber, pump energy is by Yb ³⁺Ionic absorption.Because Yb ³⁺( ²F _5/2) the excited state energy and the Er that have ^{3+ 4}I _11/2(level) is close for energy level, the Yb that this excites ³⁺Energy of ions is transferred to contiguous Er rapidly ³⁺Ion ⁴I _11/2Energy level.From this ⁴I _11/2The next relaxation of energy level with erbium ion take to potential excited state ( ⁴I _13/2Energy level).In fact, ytterbium ion is given erbium ion by absorptive pumping with required NE BY ENERGY TRANSFER and as intermediary.The amorphous YAG optical fiber of representing in the last project in the application target of this principle in optical fiber and the above-mentioned Table I of mixing ytterbium/erbium identical.

Also be proved potential commercial significance with other optical fiber and waveguide assembly at the glass optical fiber that is mixed with other rare earth ion outside the erbium.Especially, the fiber laser of continuous wave (CW), Q-switch and mode locking is operated in from the ultraviolet light direct to the far red light and all has been proved.(for example seeing Rare Earth Doped Fiber Lasers and Amplifiers, M.J.F.Digonnet, Ed., Marcel Dekker, Inc., New York, 1993).Above-mentioned these experimental results have been used Er ^{3+ 4}I _13/2→ ⁴I _15/2Conversion is collected in together, but their ubiquity should not be left in the basket.

The characteristics of er-doped amorphous YAG optical fiber described herein be can provide a kind of on the wideer bandwidth of the bandwidth that provides than existing apparatus and method the method for amplification input signal.By substituting silica-based Er-doped fiber with er-doped amorphous YAG optical fiber, to compare with the upper limit that existing known amplifier is approximately 1620 nanometers, same amplifier architecture provides amplification on the bandwidth that approximately expands to 1650 nanometers.

Adopt first structure 800 of method of the present invention to be illustrated among Fig. 8.Fig. 8 is similar to Fig. 1, but in Fig. 8, traditional Er-doped fiber 110 is replaced by er-doped amorphous YAG optical fiber 810.For being associated, also comprise 822, one second optoisolators 824 of 820, one Wave division multiplexings of one first optoisolator (WDM) coupling mechanism and an optical pumping source 830 with above-mentioned Fig. 1.

The operation of EDFA 100 among the operation of the method for the present invention among Fig. 8 and Fig. 1 is similar.But, contrast with the method for operating of structure among Fig. 1, put on the wavelength in the L band upper extent that the light signal of embodiment among Fig. 8 comprises about 1610 nanometers-1653 nanometer.Because the bandwidth of er-doped amorphous YAG optical fiber 810 is widened, wavelength is that the light signal of 1610-1653 obtains amplifying in er-doped amorphous YAG optical fiber 10.Therefore, compare with the method for operating with front construction, the method for operating of the structure of Fig. 8 provides a gain bandwidth (GB) of widening.In other words, import backwards except pumping or towards the input of former and later two directions, can adopt the scheme identical with Fig. 8.

Fig. 3 represents that the C band of amorphous YAG material and the alternative YAG material of amorphous lanthanum is all extremely wide, and this C band is widened to about 1481 nanometers (3-dB point).For example, in the amorphous YAG optical fiber of 0.5 centimetre and er-doped 8%, ⁴I _13/2→ ⁴I _15/2Mainly also be to contain more that the back fluorescence Spectra of short wavelength's part approximately expands to 1603 nanometers (3dB point) from 1482 nanometers in the conversion spectrum.Another aspect of the present invention is that a kind of C band amplifier of operating the structure that adopts Fig. 8 amplifies wavelength and is approximately 1480 nanometers or is higher than 1480 nanometers to 1565 nanometers or be lower than the method for a plurality of signals of 1565 nanometers.Lower promptly about 1480 nanometers of wavelength are lower than the value of same transitions Er3+ report in other known matrix substantially in this scope.

Fig. 9 represents to use another structure 900 of method of the present invention.The structure 900 of Fig. 9 is identical with the structure 200 of Fig. 2, and comprises low C band EDFA 910 and a higher L band EDFA 920.These input optical signals are by a WDM coupling mechanism 930 and EDFA910 and 920 couplings.EDFA 910 and output combination in coupling mechanism WDM 932 of 920, these array outputs offer a delivery outlet.Each EDFA 910 and 920 enough has one or more pumping source (not shown) separately.In Fig. 9, higher (L band) EDFA 920 comprises an above-mentioned er-doped amorphous YAG optical fiber 940.Lower (C band) EDFA 910 also comprises the amorphous YAG optical fiber 950 of an er-doped, and still, low EDFA 910 and higher EDFA 920 can also be a kind of traditional E DFA that uses silica-based or other glass-based optical fiber of tradition.Back reflection in first optoisolator 60 prevents from EDFA 910,920 to the input port.Second optoisolator 962 prevents from the delivery outlet to EDFA910 and the back reflection in 920.

By to apply wavelength be about 1481 nanometers or be lower than 1481 nanometers to about 1653 nanometers or be higher than the input optical signal of 1653 nanometers, adopt structure 900 operations among Fig. 9.This WDM coupling mechanism 930 is input optical signal separately, makes the input optical signal and low EDFA 910 couplings of wavelength less than about 1565 nanometers, and wavelength is coupled with higher EDFA920 greater than about 1565 input optical signal.Low EDFA 910 amplification ranges are approximately the signal of 1481 nanometers-1565 nanometer, provide output signal after the amplification by coupling mechanism 932 to delivery outlet.Higher EDFA920 amplifies the signal in about 1565 nanometers-1653 nanometer range, provides amplifying signal by coupling mechanism 932 to delivery outlet.Persons of ordinary skill in the art may appreciate that the dead band in the light input signal can provide, and gets rid of by EDFA 910 and 920 amplifying signal under this wavelength near 1565 nanometers.As previously mentioned, in higher EDFA 920 or low EDFA 920 or this two EDFA, use er-doped amorphous YAG on than bigger in the past bandwidth, to provide amplification.

Higher (L band) EDFA 920 among Fig. 9 also can constitute as one of embodiment described in Figure 19-14.

Figure 10 represents to have as described above the preceding L band amplifier 1000 of the er-doped amorphous YAG optical fiber of a single length 1010.This optical fiber 1010 is by the input pumping of an optical pumping source 1020 by one the one WDM coupling mechanism 1022.The input optical signal of input port 1030 offers delivery outlet 1034 by second input of one first optoisolator 1032 and one the one WDM coupling mechanism 1022.The output of optical fiber 1010 offers delivery outlet 1034 by one second optoisolator 1036.The last delivery outlet coupling of the input port 1030 of the amplifier 1000 among Figure 10 and the WDM coupling mechanism 930 among Fig. 9, the above-mentioned inlet coupling of the coupling mechanism 932 among delivery outlet 1034 and Fig. 9.In Figure 10, optical pumping source 1020 comprises one in the first optical pumping wavelength X _P1First optical pumping 1050 and the second optical pumping wavelength X of pump light are provided down _P2Second optical pumping 1052 of optical pumping wavelength is provided.The output of two pumpings 1050,1052 is coupled in the 2nd WDM coupling mechanism 1054.The output of the 2nd WDM coupling mechanism 1054 offers first input of a WDM coupling mechanism 1022 as compound pump signal.These two pump signal can be by other known method multipath transmission.In a kind of optimum manipulation method, first pump wavelength _P1Be that 980 nanometers or 1480 nanometers are not (or for preferably being subjected to another Er that the pump excitation state absorbs ³⁺Pumping wavelength), this second pump wavelength _P2Be approximately 1555 nanometers.These pump signal can produce with semiconductor laser or with other solid-state laser.These two wavelength X _P1, λ _P2Enter in the optical fiber 1010 from a WDM coupling mechanism 1022.First pump wavelength _P1Identical with the effect of pumping wavelength in the C band EDFA.Especially, first pump wavelength _P1In optical fiber 1010, produced population inversion, therefore gain is provided.But this gain spectral is maximum in C band, in L is with a little less than.The result, radiation has simultaneously been amplified widely in the C band, has produced a very strong C and has been with radiation (amplified spontaneousemission, i.e. ASE) when amplifying, it makes gain reduction on the whole gain bandwidth (GB) of optical fiber 1010, comprise the gain in the L band.Therefore, the gain in the L band reduces, and the gain in the L band is too low and do not have actual use value usually.In order to improve the gain of L band, C band ASE is reduced.In the method for operating that adopts Figure 10 structure, C band ASE is by wavelength X _P2Second pumping reduce.The wavelength of second pumping is chosen as about 1555 nanometers, and the high gain region interior with the C band is consistent.Wavelength X in entering optical fiber 1010 _P2Pumping obtain amplifying very doughtily, cause the interior gain reduction of C band and L band.The wavelength λ that is at that time _P2Pumping has also reduced power significantly and (has for example seen J.F.Massicott in C band ASE, et al., Low noise operation of Er3+dopedsilica fibre amplifier around 1.6 μ m, Electronics Letters, Vol.28, No.20, Sept.1992, pp.1924-1925).The power that reduces in C band ASE causes gain increase in two bands.In these two opposed effects, the latter is dominant, so L band gain increase, even is better than the gain of C band.This type L band amplifier has good (low) feature of noise, but its gain efficiency low (it needs a high pumping power to produce certain gain).

Figure 11 represents a similar structure 1100 of the structure with Fig. 8.This structure 1100 comprises the er-doped amorphous YAG optical fiber 1110 of a preceding pumping.This optical fiber 1110 can 980 nanometers or 1480 nanometers (the erbium wavelength of another no ESA pumping) go out from optical pumping source 1120 pumpings by a WDM coupling mechanism 1130.First and second optoisolators 1140 and 142 are operated as described above.

The structure of representing among Figure 11 is preceding pumping structure.Back pumping and two directional pump also are possible.Erbium shows very strong ground state and absorbs (GSA) in C band, but in the L band seldom or do not have a GSA.GSA reduces along with the increase of wavelength in the L band.Then, along with the increase of optical fiber 1110, at some some place, it is so big that the GSA of C bandgap wavelength becomes, so that for the not gain of given pump power, be loss on the contrary in the C band.On the other hand, in the L band, have only GSA seldom, can obtain gain.Therefore, a kind of conventional Amplifier Design method that has sizable gain in L band is to select sufficiently long optical fiber, for example, is the twice that the C band amplifier of same type optical fiber requires.This method has been destroyed the gain of C band, has greatly reduced ASE in the C band.Therefore, the structure of Figure 11 has become a L band amplifier that can combine with the top of constructing among Fig. 9.

Figure 12 represents another structure of L band amplifier, and this structure is similar to the structure of amplifier shown in Figure 11.This structure 1200 comprises an er-doped amorphous YAG optical fiber 1210 that is positioned between the WDM coupling mechanism 1220,1222.The one WDM coupling mechanism 1222 is by one first optoisolator 1232 and delivery outlet 1240 couplings.The 2nd WDM coupling mechanism 1222 is by one second optoisolator 1242 and delivery outlet 1240 couplings.One first optical pumping source 1250 is by a WDM coupling mechanism 1220 and this optical fiber 1210 couplings, optical fiber 1210 in along the propagation of the direction towards the 2nd WDM coupling mechanism 1222 pump light from a WDM coupling mechanism 1220.One second optical pumping edge 1252 is by the 2nd WDM coupling mechanism 1222 and this optical fiber 1210 couplings, optical fiber 1210 in along the propagation of the direction towards a WDM coupling mechanism 1220 pump light from the 2nd WDM coupling mechanism 1222.Therefore, propagate from pump light twocouese in this optical fiber 1210 in these two sources.Use a kind of same twocouese structure of traditional Er-doped fiber for example to be disclosed in H.Ono, et al., Gain-flattened Er3+-doped fiber amplifier for a WDM signal inthe 1.57-1.60-m wavelength region, IEEE Photonics Technology Letters, Vol.9, No.5, May 1997, among the pp.596-598, its represented a kind of use conventional er-doped silicon optical fiber similar embodiment.Figure 12 structure identical with the constructor mode of Figure 11.Backwards to providing pump light second pumping source 1252 to be used to regulate gain spectral.Especially, this gain spectral can be passed through suitably to regulate the back pump power and is with on the bandwidth by steady at very big L.

Figure 13 represents a kind of another kind structure 1300 of L band amplifier.This structure 1300 comprises the amorphous YAG optical fiber 13 10,1312 of two er-dopeds, and they are connected in series by a WDM coupling mechanism 1320.Especially, input port 1330 is coupled by the end of one first optoisolator 1332 with first optical fiber 1310.The other end of first optical fiber 1310 is connected with an input of WDM coupling mechanism 1320.A pumping source 1340 is connected with second input of WDM coupling mechanism 1320.The output of WDM coupling mechanism 1320 is connected with an end of second optical fiber 1312.The other end of second optical fiber 1312 is connected with delivery outlet 1350 by one second optoisolator 1352.The pumping light wavelength that pumping source 1340 provides is preferably about 980 nanometers or about 1480 nanometers.Pumping source 1340 pumpings second optical fiber 1312 produces gain in second optical fiber 1312.Second optical fiber 1312 is in back radiation (ASE) when producing amplification, promptly towards 1320 radiation of WDM coupling mechanism.ASE from second optical fiber 1312 is coupling in first optical fiber 1310 by WDM coupling mechanism 1320.This ASE center is approximately 1550 nanometers (C band), and this ASE is absorbed by first optical fiber 1310.This first optical fiber 1310 is therefore optically pumped to be gone out, and produces gain in the L region.For example see J.Lee, et al., Enhancement of the powerconversion efficiency for an L-band EDFA with a secondary pumpingeffect in the unpumped EDF section, IEEE Photonics Technology Letters, Vol.11, No.1, Jan.1999, pp.42-44 has wherein represented a similar embodiment of using traditional er-doped silicon optical fiber.

Figure 14 represents a similar structure 1400 of the structure with Figure 13.This structure 1400 comprises one first er-doped amorphous YAG optical fiber 1410 and one the second er-doped amorphous YAG optical fiber 14112 by WDM multiplexer 1420 series connections.Especially, input port 1430 is coupled by the end of one first optoisolator 1432 with first optical fiber 1410.The other end of first optical fiber 1410 is connected in the input of WDM coupling mechanism 1420.Pumping source 1440 is connected in second input of WDM coupling mechanism 1420; But not as Figure 13, pumping source 1440 connects in second input of WDM coupling mechanism 1420, and is relative with first output of WDM coupling mechanism 1420.The output of WDM coupling mechanism 1420 connects an end of second optical fiber 1412.The other end of second optical fiber 1412 is connected to a delivery outlet 1450 by one second optoisolator 1452.In structure 1400, directly to first optical fiber 1410, first optical fiber 1410 ASE around 1555 nanometers provide pump light for second optical fiber 1412 from the pump light of pumping source 1440.Among Figure 14 backward the dual EDFA that goes out of pumping than the dual EDMA effect that goes out of pumping is weaker a little forward among Figure 13.For example see J.Lee, et al., Enhancement of thepower conversion efficiency for an L-band EDFA with a secondarypumping effect in the unpumped EDF section, IEEE Photonics TechnologyLetters, Vol.11, No.1, Jan.1999, pp.42-44 has wherein represented a similar embodiment of using traditional er-doped silicon optical fiber.

Obviously, in the art, these different structures provide certain advantage, as efficient and noise properties, also have the repeatability of size, complicacy, cost, production etc. in addition.In addition, can preferably a kind of specific structure in the application of certain type, preferably another kind is constructed in another kind is used.

Compare as the method that comprises formation amplifiers such as silicon, fluozirconate, tellurite with other optical fiber of known use or waveguide, method of the present invention has many good qualities.For example, advantage is that the bandwidth of the erbium in other well known materials of bandwidth ratio of C band is wide.Observed little about 1481 nanometers (3-dB point) that arrive of fluorescence in some material compositions, bandwidth strengthens on the expression C band short wavelength afterbody.Therefore, in the material of these amorphous YAG component, gain bandwidth (GB) has all been widened at short wavelength's afterbody of C band substantially.

Second characteristic of this method are that the bandwidth of erbium is wideer in other known broadband materials of bandwidth ratio of L band.Observed in some materials are formed, fluorescence reaches about 1653 nanometers (3dB point), and this shows that bandwidth increases on the L belt length wavelength afterbody.L band bandwidth is wideer by 60% than the bandwidth of the erbium in any other known fiber optic materials approximately.

The 3rd characteristics of this method are by being with amplifier in conjunction with above-mentioned L band amplifier and above-mentioned C, use circuit common shown in Figure 9, or use circuit shown in Figure 8, the C band that the amplifier that obtains is given on a bandwidth to add L and be with the gain of erbium in the material of any known broadband of the ratio of gains wideer.For example, use the circuit of Fig. 9, can observe and be approximately the fluorescence of 1481 nanometers to 1653 nanometers, the perhaps three dB bandwidth of about 172 nanometers, it approximately is the twice with the interior erbium the wideest observed fluorescence bandwidth of other known broadband materials.

The 4th characteristics of this method are to use very short L band and the realization of C band fiber amplifier, and characteristics are that several benefits is arranged, and are for example compacter and reduced cost.The important benefit of technically another is that this method can reduce harmful nonlinear effect, and they are problems that known L band amplifier is paid close attention to.In any optical fiber, when the result of transmission signal strength on the transmission length at transmission signals is too big, begin to produce some nonlinear effects, the Brillouin scattering that for example is stimulated (stimulated Brillouin scattered, SBS) modulate mutually with friendship (cross-phase modulation, XPM).Two kinds of effects are all harmful to the operation of EDFA.The flashlight that SBS will transmit forward converts the flashlight of transmission backward to, wherein has a relevant frequency displacement.The generation that back kick is lost with frequency displacement all is harmful to.The XPM effect can cause with being coded in a message part on the signal passes to another signal, causes unnecessary cross-talk.This SBS effect takes place in the communications portion that optical fiber is connected and in the EDFA itself with the XPM effect.This telecommunication optical fiber is grown (tens kilometers) very much, but the mode field of telecommunication optical fiber bigger (promptly low) for given pump power intensity, and this has just reduced XPM and SBS effect in the telecommunication optical fiber.On the other hand, an EDFA relates to the optical fiber that length is shorter, but its mode field quite little usually (being the higher of the signal intensity ratio telecommunication optical fiber that carries of Er-doped fiber).Therefore, the XPM effect may be stronger in an EDFA, and especially in traditional L band EDFA, they relate to one than the longer Er-doped fiber of traditional C band EDFA.Avoided these problems with in the method for the invention er-doped amorphous YAG material by in erbium concentration ratio, reducing fiber lengths substantially, it normally 100 or more a plurality of factor in one.Therefore, the efficient of XPM effect and SBS effect also is reduced owing to fiber lengths reduces in these optical fiber.

For each structure described here, the length of various Er-doped fibers, power in the various pumpings, and other parameters also can use theoretical model and the experimental technique of describing in document and the known technology, assess by theoretical and experiment, optimize certain EDFA parameter, for example gain, gain trace, noise properties, pumping efficiency etc.

Although described method of the present invention in conjunction with er-doped amorphous YAG optical fiber above, be to be understood that this method can also utilize the slab guide technology to realize.Especially, when this waveguide used er-doped amorphous YAG material to constitute, this method also can realize with the plane channel waveguide.

Method of the present invention partly comes from this discovery, i.e. Er in amorphous YAG ^{3+ 4}I _13/2→ ⁴I _15/2Changing provides extremely wide fluorescence bandwidth, promptly is about 121 nanometers when the erbium that is mixed with 8%, and part comes from this discovery, the i.e. Er of higher concentration ³⁺(perhaps being other rare earth oxide ions) causes wideer fluorescence bandwidth and wideer gain of light spectrum.

The applicant has described a kind of amplification method of L band Erbium-Doped Fiber Amplifier (EDFA), has wherein used gang's new material to produce for Er ^{3+ 4}I _13/2→ ⁴I _15/2Change the L band spectrum wideer than other any well known materials.The applicant has described a kind of amplification method of C band Erbium-Doped Fiber Amplifier (EDFA), has wherein used gang's new material to produce for Er ^{3+ 4}I _13/2→ ⁴I _15/2Change the C band spectrum wideer than other any well known materials.

The description of international public publication WO97/25284

Paul C.Nordine, et al., in Fiber Drawing from Undercooled MoltenMaterials, WIPO International Publication No.WO97/25284 is disclosed on July 17th, 1997, wherein disclose the method for an example manufacturing optical fiber, can well be used to finish the present invention.Its instructions all is incorporated herein by reference at this.Detailed description for it provides below in conjunction with Figure 16-23, and they are corresponding to Fig. 1-8 of WO97/25284.

According to International Patent Application WO 97/25284, Paul C.Nordine etc. has been surprisingly found out that under state of a control certain liquid is melted thing to be crossed cold energy and enough form and have viscous enough thawing thing, can not have big quantity of fluid crystallization ground drawing optical fiber again, comprise the thawing thing that fusing point viscosity is too low and allow so to operate.Described herein is several routine optical fiber that draws from the cold thawing thing of the mistake of several oxidation materials, and optical fiber can be under fusing point or is higher than under the situation of fusing point and draws from melt thing for this reason.Utilize the method for WO97/25284, can be under the supercooling temperature state and be lower than balanced melt temperature and surpass under 20% the state from this thawing thing drawing optical fiber rapidly.Also surprisingly, glass optical fiber also can draw from the cold thawing thing of the mistake of chemical constitution, and its adjuvant that contains is higher than the additive concentration of prior art optical fiber.In addition, can notice that the optical fiber that draws according to the method for WO97/25284 has high tensile strength, suppose it is because the surface ratio of WO97/25284 optical fiber is more flawless.

The method of WO97/25284 utilizes one " tubular stinger " to begin to draw.The ability of growth optical fiber is subjected to the tubular stinger physical property, use several conditions of tubular stinger such as material, size, surface finish and interior insertion the insertion tip insertion depth and begin to draw before the material impact of the residence time of tubular stinger in the liquid.The control of these performances and process influences moistened surface and adhesion, allows to carry out in fiber draw process significant control.

Briefly, method among the WO97/25284 comprises step: (1) melts the sample of selecting material under no container condition, produce hanging drop, perhaps having under the state of container as in a crucible, (2) with liquid cooling below melt temperature, even this liquid is cold excessively, and (3) make supercooled liquid contact with the tubular stinger probe, under the state that requires, pull out probe, drawing optical fiber from liquid.

In all cases, can be by control (1) liquid viscosity (by changing melt temperature and/or gaseous environment), (2) the fibre-optical drawing rate of reaching reaches the control of fibre diameter.The gas that uses in the following test comprises for example oxygen, air and argon gas, although also can use other gas such as nitrogen, helium, carbon monoxide, carbon dioxide, hydrogen and water vapor.Fast draw rate and/or slow draw rate help small diameter fiber usually.But the fibre diameter upper limit is by using the minimum draw rate decision that can not cause crystallization in the cold thawing thing of a large amount of mistakes.The lower limit of fibre diameter is by can not the fracture optical fiber or the maximum draw rate decision of drawing optical fiber from melt thing that can obtain.

In addition, the optical fiber that draws according to the method for WO97/25284 can change crystallization optical fiber into by glass optical fiber being heated to the temperature that special glass crystallization occurs.

The method of in WO97/25284, describing can be from several materials production high-purity optical fiber, people all know the component intensity height that at high temperature has these compound substances, hard, creep speed is slow, oxidation resistance is strong or chemical compatibility is good.Can allow optical fiber to constitute, for example still be not limited to the material that field of telecommunications is used by the low material of absorption of electromagnetic radiation performance.Disclosed method can also be synthesized homogeneous glass optical fiber among the WO97/25284, comprises the high concentration domination element that for example uses fiber laser and fiber laser amplifier region but be not limited to these fields.According to WO97/25284, these optical fiber can promptly draw out, and can reduce production costs, can be by crystallization, form stable material, can be used in the anti-oxidant combination materials with field of high-temperature structure very, for example in turbine firing chamber liner and the thrust deflector.The optical fiber that the method for WO97/25284 can allow the tensile strength used in the synthesized polymer parent combination materials field and hardness to improve.In addition, the method for WO97/25284 allows to be made of the biocompatible material that use in organic live body field.Therefore, the method for WO97/25284 has been expanded the material ranges that can utilize liquid to melt the optical fiber of thing drawing widely.

Example 1-optical fiber drawing apparatus

Figure 16 represents a kind ofly container is being arranged or do not having under the thaw condition of container, utilizes disclosed principle among the WO97/25284, the preferred plan of drawing optical fiber from cross cold thawing thing.It should be noted among the WO97/25284 a kind of new important feature of tubular stinger be optical fiber be not by a mould or similarly shaped device draw.In this example, described a kind of no container state,, included the thawing thing of container although these principles and method for drawing optical fibers can use any thawing thing to draw required optical fiber.

The drop that the described no container state of Figure 16 also can utilize aeroacoustics tubular stinger (AAL) to insert from drawing optical fiber obtains.This method is used to 32 aerodynamic force from gas ejector, stablizes from the acoustic effect of three acoustic positioning systems 33 by using.According to WO97/25284, this device that inserts sample is devices of description of the Prior Art with other devices, and the use of any method of inserting cold sample is all in the scope of WO97/25284.These methods comprise as electromagnetic suspension and electrostatic suspension.These methods relate under high vacuum state the suspension and the maintenance of melting thing, and it can easily be applied to metal, alloy with the method for drawing optical fibers of WO97/25284, and to the air environment in the material of the gas reaction sensitivity that occurs.

A kind of hanging drop is by the light beam heating that utilizes carbon dioxide laser and send and melt sample and form, although can think any heating means all in the scope of WO97/25284, for example incandescent lamp or arc lamp, microwave heating, induction heating, stove and accessory or be suspended in the thermal current.In addition, anyly can provide the laser beam of enough heats to may be used to the method for WO97/25284 to sample.In this concrete example, the carbon dioxide laser light beam is divided into two bundles 34, and they focus on the opposition side of suspended sample, and sample is melted.Melt thing and keep at high temperature, up to all being melted, then the heating power that provides by cut-out or minimizing makes molten melt drop cross cold and keeps it cold excessively.

Tubular stinger (stinger) and optical fiber drawing apparatus 31 are that the tungsten filament tubular stinger of 0.01cm constitutes by the diameter that is connected to a bar 3, are handled by solenoid actuator 4, are positioned to make when solenoid is excited that the tungsten filament tubular stinger is most advanced and sophisticated inserts in the hanging drop 1.Tungsten filament tubular stinger and the contact of crossing between the cold thawing thing must conscientiously be controlled, and occur the out-phase nucleus owing to contact tubular stinger to avoid in crossing cold thawing thing.Though this nuclear is not to operate by the fibre-optical drawing of WO97/25284 to cause usually, if the glass optical fiber that forms was as the tubular stinger material in the past, can alleviate the problem of heterogeneous nucleus so.Although tungsten filament is used as the tubular stinger of present embodiment, expectation utilizes the tubular stinger of various materials and size will depend on the optic fibre characteristic of viscosity and requirement, and such other tubular stinger is also included within the scope of WO97/25284.

In this example, spring-operated drawing mechanism 5 provides drawing power for the fibre-optical drawing of determining length, although the method for any drawing optical fiber all is included in the scope of WO97/25284.Drawing power that can regulating spring is so that its force constant is in the scope of k+0.1-0.25lb/in.Fibre-optical drawing speed is subjected to the further control of frcition damper 6.Electronic control circuit 7 is used for the initialization solenoid actuator, in the schedule time when carrying out the fibre-optical drawing operation in solenoid actuator release tubular stinger is remained in the drop.High-speed and high-temperature meter 35 is used to monitor the temperature of suspended sample, and this temperature can be presented on the computer screen in real time, as the image of temperature and time.Exposure intensity by increasing or reduce laser beam and the time temperature that will melt drop remains on the supercooling temperature of requirement.

Certainly, in order to obtain to require the optical fiber of size, the draw rate of the force constant of regulating spring and optical fiber as required.In addition, optical fiber drawing apparatus can be any proper device, for example motor and wheel assembly, and drawing power can be regulated according to the physical property and the method for drawing optical fibers of required optical fiber.

When the temperature of the drop that stops laser beam heats and detection cooling for the first time, start fibre-optical drawing (on computer screen, being shown as temperature and time figure).When temperature reached preset value, solenoid actuator was by manually booting, and preset value is preferably in the best draws temperature range.In this specific embodiment, solenoid design becomes and can cut off automatically after inserting sample.Then inserter is extracted out drawing optical fiber from drop by the action that draws mechanism.The control of drop temperature is the key component of the method among the WO97/25284.When temperature is higher than the optimum temperature range of drawing optical fiber, tubular stinger can be pulled out from drop and drawing optical fiber not.When temperature is lower than the optimum temperature range of drawing optical fiber, the viscosity of liquid is very high, so that the power that tubular stinger must be put on the drop is increased to above the levitation device restoring force, and the motion of tubular stinger is used for promoting or pulling out drop from levitation position, rather than from drop drawing optical fiber.In addition, if melt temperature is too low, the optical fiber that obtains so will be than the weak point of needs.Under middle supercooling temperature, can form the optical fiber of all lengths, diameter is to arrive above 60 millimeters less than 1 millimeter.

Though reported the fiber size of certain limit in this example, also being appreciated that can the very wide optical fiber of production range of size, and this depends on draw conditions.The diameter of optical fiber is bigger when low speed draws.The diameter of optical fiber is smaller when high speed pulling.The window degree of optical fiber is subjected to the restriction of two effects.At first, under lower temperature, the power on the drop is the most at last from its position traction drop that suspends.Secondly, under higher temperature, fibre diameter increases with haulage speed, so that tension force no longer can overcome surface tension, and traction optical fiber is interrupted from liquid.In suitable drawing temperature range, can draw extremely long optical fiber.For example, the optical fiber that draws 10 mm dias reduces to 0.25 centimetre diameter up to the drop of 0.35 cm diameter, can produce than 18000 centimetres of also long optical fiber.

Figure 17 represents a best approach according to the principle of WO97/25284, wherein can be along more than one direction drawing optical fiber from the hanging drop that is in no container condition.In the method, hanging drop 15 begins in suspension nozzle 16 or uses another kind of suspension thawing technology to form.Can control the drawing device of tubular stinger operation and fibre-optical drawing speed by motor and wheel 18 or other, optical fiber 17 draws along opposite direction from the drop opposition side simultaneously.Drawing power relatively also can be controlled, and makes them almost equal or relative, thereby the power that produces on the drop is reduced, and drop can not draw out from its initial position.This figure also represents to be focused on the hanging drop top surface by lens 20 by the heating of laser beam 19 or other radiant heat source.Temperature in the heat affected zone is kept above melting point, and this temperature will descend in other zones of drop, and can allow drawing optical fiber in the drop side by sufficiently cold excessively.The fiber optic materials of pulling out from drop can replenish by increase and melt solid material 21 in the radiation heat affected zone, and these materials can be increased in the suspension liquid with powder stream and the one or more little bar of controlled speed with solid material.By control fibre-optical drawing speed, increase and melted material in the radiation heat affected zone, the cool region of crossing that keeps drawing optical fiber, can obtain a kind of continuous processing of producing long and continuous optical fiber, disclosed this method imagination of WO97/25284 never draws a plurality of optical fiber with respect to the position that remarkable displacement takes place levitation position along a plurality of directions.

Tubular stinger state and operation comprise by starting this tubular stinger contact the thawing thing with the temperature that is higher than melting point before cross cold thawing thing drawing optical fiber, and the time (being generally the 1-50 millisecond) that allows the tubular stinger contact to melt drop, although can melt the composition of thing and the viscosity change of melting thing according to this tubular stinger, appearance start-up time., tubular stinger insert to melt the insertion of distance in the thing and tubular stinger and from melting the speed of extracting of thing.If temperature is too high, can and extract tubular stinger and avoid by quick insertion by the nucleation of tubular stinger, but the speed of extracting needn't be too high and drawing optical fiber from melt thing not.Under suitable supercooling temperature, melt the supercooling temperature of thing, the viscosity of melting thing increases, and optical fiber can be drawn, and crystallization rate reduces, the speed of observing when being lower than near the material melting point.

Example 2 uses conical nozzle suspension device drawing optical fiber

Figure 18 represents to use the scheme of motor and wheel assembly and a conical nozzle suspension device (CNL) drawing optical fiber, and the diameter that can draw and suspend is 0.25-0.40 centimetre a optical fiber, although the suspension large sample depends on their surface tension and density.A kind of suspension air-flow 8 is by a plenum chamber 9, by this nozzle 10 with on suspended sample 11.This suspended sample is used by ZnSe lens 13 carbon dioxide laser beam is focused on heating and thawing on the sample top surface.The temperature of this sample is controlled by utilizing any signal retention device and stopping the LASER HEATING light beam and change laser power.Use a tungsten filament tubular stinger 77 that drives by nozzle input with by a reversible stepper motor and wheel assembly 14 from crossing cold thawing thing basal surface drawing optical fiber.This tubular stinger comprises that connects this long tungsten filament of taking turns, when traction optical fiber duration tungsten filament volume is had mercy on wheel.Certainly, also can expect using other laser instrument heated sample, for example Nd-Yttrium-Aluminium-Garnet (Nd-YAG) laser instrument of continuous wave.Certainly, except laser instrument, also can use and effectively to melt these materials and not disturb any heating means that draw operation.Except the tubular stinger method and stepper motor and wheel assembly of above-mentioned example 1, it will also be appreciated that utilization can provide any device of electric power to drawing process.

Can the computerized control direction and the acceleration of motor and wheel assembly 14 are handled tubular stinger, change the acceleration of optical fiber haulage speed, obtain constant optical fiber haulage speed.The high-speed and high-temperature meter is used to monitor sample temperature and observes the cooling behavior.Tubular stinger is wrapped on the wheel that is connected motor 14 with the optical fiber that obtains, and does not carry out further mechanical treatment, for example draws by mould.In this embodiment, fibre-optical drawing speed reaches 120 cels, although fibre-optical drawing speed depends on the individual device (being motor and wheel) that is used for providing power to drawing here.The acceleration of tubular stinger is by computer control, and an acceleration of use equals 1200 cels ²Although the WO97/25284 imagination can be used other acceleration according to concrete drawing material and required optic fibre characteristic.Can draw with this device that to reach 60 centimetres and same diameter be the optical fiber of 5-20 millimeter, although use different draw conditions also can obtain the optical fiber of other length and diameter.Insert the operation of operation and fibre-optical drawing and normally finish being less than in cycle of 0.6 second, although this time can be according to the speed and the crystallization rate variation of the viscosity of melting thing, traction optical fiber.Must begin traction optical fiber with certain traction optical fiber speed.

Begin speed with continuous drawing optical fiber with the CNL device and can be lower than speed with AAL device drawing optical fiber in the above-mentioned example 1 because when drawing power is big fluid sample and can't help fibre-optical drawing and open.At low temperatures, when thawing thing viscosity is big and when the big draw rate of fibre-optical drawing power is very fast, drawing power is enough to make melts the thing displacement, melts thing contact suspension nozzle side thereby make.Melt the thing crystallization by making, but fibre-optical drawing lasts till that always melting the thing crystallization reaches the fibre-optical drawing point in the nozzle contact.Make under the temperature of melting the thing contact nozzle in big being enough to of drawing power, the vigilant speed of growth is very low usually, is enough to make in the cycle regular hour sample center to remain liquid state, is enough to continuous drawing length greater than 60 centimetres optical fiber.

For example, be under the speed of 120 cps during contact nozzle in draw rate, under the temperature that the drop composition of mullite or yttrium-aluminium garnet (YAG) composition is subjected to displacement, rate of crystalline growth is usually less than 1 cel.Contact point between liquid and the nozzle is put about 0.2 centimetre apart from fibre-optical drawing.Therefore, fibre-optical drawing continued greater than 0.2 second after contacting with nozzle, and drawing length is 24-60 centimetre a optical fiber.As the result of fibre-optical drawing power displacement, permission contacts the method for mechanical restrictive device so can be used to draw the optical fiber of useful length with supercooled liquid.It is shocking, propagate with the speed that limits, do not disturb the continuous drawing of optical fiber, reach the drawing point that county Party committee draws from liquid up to these crystal by the crystal nucleation of contact mechanical restrictive device.

Also can assess the cooling velocity of draw line.For example, be 10 millimeters and in air, use the optical fiber of CNL device that for diameter cooling velocity can be calculated as following with the speed drawing of 100 cels

For example, the temperature of supposing liquid oxidation thing drop is 1500 degrees centigrade.The thickness of drop thermal boundary layer is significantly smaller than the sample diameter at place, suspension air-flow stationary point, and this point is the point identical with drawing optical fiber from liquid.For the draw rate that typically has a diameter from 0.3 centimetre and 100 cels, fiber optic materials draws in the time of second being less than .003 by the boundary layer.Suppose that fiber optic materials and gas keep thermal equilibrium, the order of magnitude of cooling velocity is 500000 degrees centigrade/second.If as according to the aluminium oxide thermal behavior with from the enthalpy change speed calculation of per unit surface area 10 mm dia optical fiber, the heat flux of optical fiber surface is approximately 700 watts/centimetre 2, this cooling velocity will occur so.

Supposition optical fiber keeps hotter now.Be as cold as under 1500 degrees centigrade the environmental gas temperature advection heat flow q of optical fiber " provide by following formula:

$q^{\′\′}=\frac{{\mathrm{Nu}}_h{k}_f(T_f-T_a)}{d}$

T wherein _fAnd T _aBe optical fiber and environment temperature,

k _fBe average gas " film " temperature (T _f+ T _a)/2 time gas coefficient of heat conductivity,

D is a fibre diameter, and

Nu _hIt is the nusselt number (Nusselt number) that conducts heat.

For the condition of supposition, kf is approximately 4*10 ^-4Watt/(centimetre degree centigrade), Nu _hBe approximately 1, q " be approximately 600 watts/centimetre.Therefore, optical fiber does not have the supposition of cooling to cause heat flux to compare with requiring to keep with the thermally equilibrated heat flux of environmental gas.Therefore can infer that the CNL method for drawing optical fibers has obtained the cooling velocity of the drawing optical fiber of per second hundreds of thousands degree centigrade for the optical fiber of 10 cm diameters.For the optical fiber of larger diameter, cooling velocity is less, substantially with square being directly proportional of fibre diameter.Therefore, the optical fiber for 50 centimetres of diameters will produce the cooling velocity that surpasses 4000 degrees centigrade of per seconds.

Example 3-melts drawing optical fiber the thing from mullite

Figure 19 represents the time and the temperature conditions of drawing optical fiber from the cold thawing thing of the mistake of mullite composition, wherein Al ₂O ₃: SiO ₂Mol ratio be 60: 40, use the method for drawing optical fibers of WO97/25284.

Figure 19 represents the representative temperature-time course of suspended sample in the fibre-optical drawing test, as the functional arrangement of the temperature and time of measuring with leucoscope.Before the described time cycle, melt sample with the carbon dioxide laser light beam, simultaneously it is suspended in the AAL device in argon gas stream, and remains under the steady temperature.The temperature range of drawing optical fiber is determined by using Figure 16 and example 1 described insertion and drawing device drawing optical fiber at various temperatures.In case showing with the writing time of the reduction at interval of 0-2.0 second, temperature stops the just cooling of LASER HEATING light beam liquid.The temperature range of successful drawing optical fiber is presented on the figure from supercooled liquid in the cooling cycle.In the time cycle of second, show that temperature rises to the melting point of sample at about 2.0-2.2.Occurring this temperature when having served as cold liquid spontaneous crystallization rises.The energy that crystallization discharges is enough to sample is heated to melting point, and wherein temperature keeps constant, continues crystallization simultaneously.At last, after all gas all has been consumed, because the thermal loss of solid sample descends temperature.

As shown in figure 22, the composition of crystal mullite and high-temp liquid balance are not included in the low temperature mullite phase region.The mullite that forms when therefore this figure shows with the highest temperature and during fluid balance is that thermokinetics is unsettled at low temperatures.On the contrary, the glass optical fiber component that forms according to the principle of WO97/25284 can be under the temperature of planning to use from the mullite phase region independent the selection.These glass optical fibers can be heated, and are transformed into pure crystallization mullite optical fiber, and these optical fiber are stable about the precipitation of second phase under the application of temperature.

Also can drawn glass fiber under a lot of situations of observing recalescence (recalescence) (heat that discharges by crystallization causes temperature to rise to melting point).For example, even observing under the situation of recalescence, also can obtain glass optical fiber as the described mullite composition of this example.

Example 4-uses containment system drawing optical fiber from cross cold thawing thing

Drawing optical fiber in the system of container is arranged is also imagined in description among the WO97/25284.Figure 21 represents to point out to use a most preferred embodiment of a kind of method of liquid container, and it is convenient to not have the ground of crystallization again drawing optical fiber from cross cold thawing thing.An important feature of this method is included in the container and sets up and temperature gradients, and is cold so that the part melted mass must be.In the method, the material of being concerned about 30 is placed in the open containers 2, and in a crucible, the temperature of this container is kept above the temperature of melting point.Lid 25 also remains on the temperature that is higher than melting point, and lid begins to be placed on the container, obtains thermal equilibrium at internal tank, realizes the thawing of material.Lid can be lifted or remove then, makes thermal loss and cooling melt the surface.Can control the heat transfer state that melts surface 23, it is cold that the thawing surface middle section that exposes to the open air must be, thus from supercooled liquid drawing optical fiber.The inwall of container 28 and can remain under the temperature that is higher than melt temperature near the small part liquid 27 of these inwalls of container can not appear on these walls heterogeneous nucleation.

Figure 21 represents heating crucible 22 and melted material 30, can also can utilize the opening drawing optical fiber that passes through the independent pilot device as the effect of motor and wheel 26 or other drawing devices by the big opening drawing optical fiber 24 of ratio optical fiber in the lid 25 of lifting.The fiber optic materials that takes out from melt thing can be replenished by increasing and melt solid material in the zone that surpasses melting point at melt temperature.Utilize example 1 described one or more tubular stinger (not shown), perhaps the effect by motor and wheel assembly or other drawing devices starts fibre-optical drawing.

The temperature diagram of liquid and crucible top surface is illustrated in the bottom of Figure 21, as the function of lateral attitude on crucible and the contained liquid top surface.The balance melt temperature is by T on this part coordinate of Figure 21 _mExpression.Be higher than T near that part of liquid of sidewall of crucible and the temperature of crucible _m, and drop to less than T away from the liquid surface temperature of chamber wall _mExposing the central temperature of liquid surface to the open air can estimate as following, supposes that the diameter of container is far longer than liquid depth, makes heat be delivered to the surface from the bottom.For the size of estimated temperature gradient, suppose that also the convection heat losses can ignore, heat only loses from liquid surface by radiation, and radiations heat energy no longer reflects back on the liquid surface.Temperature descends near following equation in the liquid, and wherein the right side has provided the heat flux from basal surface to the liquid top surface, and temperature remains under the crucible temperature, and wherein the left side has provided the radiation heat loss of liquid surface:

$\mathrm{\&sigma;\&epsiv;}{\mathrm{<figure-callout\; id="4"\; label="T\; S"\; filenames="A20051000234800441.png,A20051000234800451.png"\; state="\{\{state\}\}">T</figure-callout>}}_S^{}=k\frac{T_C-T_S}{h}$

σ=5.67*10 wherein ^-12Watt/(cm ²Degree K ⁴), be 0.8 to the graceful constant ε of Si Difen bohr thatch of liquid oxidation thing, the emissivity Ts of liquid surface is the temperature of liquid surface, and To is the temperature of crucible, and h is the degree of depth of liquid level.

Under the high temperature average conduction k of oxide be 0.02-0.2 watt/(centimetre degree centigrade).

Use mullite as an example, T _C=1900 degrees centigrade (being higher than melting point a little), T _S=1670 degrees centigrade (about 200 degrees centigrade degree of supercooling), the actual k value of foundations such as Nordine obtains h=0.045 centimetre.

Aforementioned calculation shows the liquid depth of estimation less than 0.5 centimetre, is enough to obtain deep cooling on the liquid surface in container that remains on more than the melting point.This degree of depth is enough little, is enough to satisfy rapidly the little a lot of supposition of liquid depth container diameter.

Example 5-gaseous environment and recalescence effect

The formation and the fibre-optical drawing condition that it has been found that degree of supercooling, glass blocks depend on gaseous environment.In this example, reported drawing optical fiber under three different gaseous environments: air, pure oxygen, and pure argon.But also can expect utilizing other gas, as nitrogen, helium, carbon monoxide, carbon dioxide, hydrogen and water vapor.

For example, Y ₃Al ₅O ₁₂The glass blocks of composition can form on no crystallization ground in argon gas.In air or oxygen, liquid Y ₃Al ₅O ₁₂Composition spontaneous crystallization when cold excessively.Second example utilizes pure alumina to provide, and before spontaneous crystallization, liquid can be cooled to the interior melting point of argon gas below 450 degrees centigrade for this reason.Can form drawing optical fiber under all situations of a large amount of glass samples, crystallization can not take place when melting the thing cooling.Usually drawn glass fiber under a lot of situations of recalescence can observed.For example, under oxygen atmosphere, the glass optical fiber of mullite composition can be obtained, wherein also recalescence can be observed.These optical fiber can be higher than crystal nucleation and take place to melt thing spontaneous crystallization temperature under draw these optical fiber.

Made with recalescence under the condition of cold thawing thing spontaneous crystallization, the cooling velocity of usually big quantity of fluid is per second 100-500 degree centigrade.Known if chilling temperature surpasses the critical cooling rate that glass forms, will form glass optical fiber by melting thing so; Therefore, the observation of recalescence shows in big quantity of fluid and can not obtain critical cooling rate.But, when fluid temperature is higher than the spontaneous crystallization temperature, can also obtain glass optical fiber by drawing optical fiber.These results show that fibre-optical drawing technology causes the cooling velocity in the optical fiber to surpass the free cooling velocity of drop.

The new optical fiber composition of example 6-

Table II has been listed some some new optical fiber compositions that can use the method for WO97/25284 to obtain.Table II is listed these optical fiber and can be used a variety of methods to draw, and comprises tubular stinger and example 1 described drawing device, and is illustrated among Figure 18 and described tubular stinger of example and motor wheel assembly.Melt thing and can use any levitation device to suspend, comprise above-mentioned AAL and CNL device, perhaps melt thing and also can be included in as in the above-mentioned example 4.Solid sample melts by the laser instrument stove and is formed by basic pure-oxide.Use neodymium or erbium and other materials as adjuvant, wherein Al ₂O ₃: SiO ₂Be 50: 50, Al ₂O ₃: Y ₂O ₃It is 63: 37.

For the temperature that is equal to or higher than melting point, observed concussion and fluid stream show that thawing thing viscosity is low in the thawing thing that suspends, and can compare with the viscosity of liquid oxidation aluminium, are significantly smaller than typical glass and form the viscosity that material such as pure silica or Silicon-rich melt thing.These low viscosity of melting things also shown under being higher than the temperature of melting point can not be from melt thing the fact of drawing optical fiber.But under the described here all situations, method that can WO97/25284 is drawn glass fiber from cross cold thawing thing.Melting the glass optical fiber that draws out the thing from these in all cases is uniform in appearance.In visual look-up table Mingguang City of microscopically fibre, there is not second sign that precipitates mutually.

The synthetic Al that can pass through of the glass optical fiber that the optically-active concentration of dopant is high at 50: 50 ₂O ₃: SiO ₂Al with 63: 37 ₂O ₃: Y ₂O ₃Add Nd in the material ₂O ₃And Er ₂O ₃The additive concentration that uses is higher by about 1% than the typical concentration of the optical fiber of prior art.The method of WO97/25284 all forms the temperature of melting liquid fully and has obtained the high optical fiber of these additive concentrations by at first material being heated to all the components.Because it is non-crystallizable to cross cold thawing thing, it remains homogeneity, can form the high glass optical fiber of additive concentration.

In addition, the synthetic of the optical fiber that optical fiber that purity is very high and additive concentration are very little also is possible.Use no container condition to keep melting thing and can make thawing thing purifying, purification process is the reaction vaporization of (1) impurity evaporation and (2) impurity.For example, beginning to contain the have an appointment aluminium oxide of 0.0005 mole of % chromium (5/1000000ths chromium) can melt liquid and be heated to 2400 degrees centigrade and carry out purifying by no container ground.The chromium concn of analyzing reduces to 1,000,000 in the processing time of a few minutes/.Equally, can evaporate a lot of oxides of purifying by device utilization commonly known in the art.When handling material under the very high temperature in container, the dissolving of melting thing inner pressurd vessel material will prevent the purifying of liquid.Therefore, by purification of liquid under the condition of no container, can form the optical fiber that the impurity level that contains is less than 0.0001 mole percentage (1,000,000/).Equally, by this liquid of purifying at first, can use adjuvant that the concentration of the optical fiber inner additive that draws from liquid is controlled at and be less than 0.0001 mole percentage in the scope of 50 mole percentages.

Has chemical constitution CaAl ₂O ₄The synthetic method of glass optical fiber be under the condition of no container, to use the method for WO97/25284, make and melt thing and fully cross cold so that drawing optical fiber.The optical fiber traction method is described among Figure 18, and suspension is in oxygen.These optical fiber draw from the thawing thing of crossing the temperature be as cold as 200 degrees centigrade of melt temperatures that are less than about material greatly.In case further cold excessively, crystallization can not appear, can access a large amount of CaAl ₂O ₄The glass optical fiber sample.Wish to use other optical fiber traction methods, the tubular stinger of Figure 16 (stinger) drawing device for example, any method that can traction optical fiber is also included within the scope of WO97/25284.

Use the method for WO97/25284, can be from CaO-Al ₂O ₃Melt synthetic glass optical fiber in the thing, these optical fiber can be used as biocompatible structured material, can not cause anthraco-silicosis if they are inhaled into also, and as United States Patent (USP) 5552213 was disclosed, its whole instructionss were hereby incorporated by.

Use the method for WO97/25284, can also be formed with chemical constitution mineral forsterite Mg ₂SiO ₄Glass optical fiber.These mineral are and mineral enstatite Mg ₂Si ₂O ₆Thermokinetics is compatible, and this is known in the art, Mg ₂SiO ₄Being known in the art, is alternate weakening coating (interphase weakening coating), is used for the malleableize compound substance.Forsterite optical fiber is to use optical fiber tubular stinger device shown in Figure 16 and by suspending and cold excessively thawing thing forms in the conical nozzle levitation device.

Figure 20 shows the phase equilibrium diagram of aluminium-system on silicon, the whole components between expression pure silica and the aluminium oxide.Can see the disclosed work of WO97/25284 in Table II, obtain glass optical fiber in very large-scale composition, these compositions comprise pure mullite composition stable under the low temperature.

The crystallization of example 7-optical fiber

Also can be according to the optical fiber that the method for WO97/25284 obtains by crystallization.Table III has reported that under 1100 and 1200 degrees centigrade temperature mullite composition glass optical fiber was as 60: 40 Al ₂O ₃: SiO ₂These results show, drawn glass fiber is heated to the crystallization optical fiber that the method for medium temperature can the production chemical constitution can be controlled then from cross cold thawing thing, and these compositions are stable under medium temperature.

Fibre-optical drawing speed is controlled, and surpasses the crystallization rate of cold thawing thing usually, and the cooling velocity that obtains in optical fiber is usually greater than the critical cooling rate that forms glass in the material of drawing optical fiber.Crystallization rate that glass forms or critical cooling rate can not be strictly as the function of temperature.For mullite, the draw rate of 30 cels is enough to avoid melting the thing crystallization.The crystallization rate of mullite approximately is 3 cels under the temperature that is lower than melting point 200K.

Liquid oxidation yttrium-crystalline aluminophosphate speed is greater than the crystallization rate of liquid mullite composition.Using described motor of Figure 18 and wheel assembly in the straight argon air-flow is yttria-lead glass optical fiber of several millimeters with the speed drawing length of 30 cels, draws long 60 centimetres optical fiber with the speed of 100 cels.This liquid is cooled to below about 200 degrees centigrade of melting points.

As shown in example 2, the cooling velocity in optical fiber increases with fibre diameter and reduces.The draw rate that is used to obtain to have given diameter optical fiber also reduces with the increase of fibre diameter.Therefore, in the accompanying drawing of large-diameter fibre-optical, may appear at the cooling velocity that obtains in the optical fiber state less than the glass ware forming critical cooling rate.The optical fiber that obtains under this state comprises some crystalline materials at least.In addition, if crystallization rate surpasses fibre-optical drawing speed under the fibre-optical drawing state, the crystallization that forms in optical fiber so will be propagated in optical fiber, cause the supercooled liquid crystallization that forms optical fiber, therefore finish fiber draw process.

Table III provides from cross cold thawing thing drawn glass fiber and the tension force experimental data of the crystallization optical fiber that forms by heating drawing optical fiber in air.Should be noted that very high tensile strength behind the optical fiber of traction like this.Reach 6.4Gpa with tensile strength value in the mullite composition optical fiber that obtains according to the principle of WO97/25284 and compare, the tensile strength that can obtain in having the prior art optical fiber of identical component is limited to and is less than 3Gpa.

The chemical constitution of Table II drawn glass fiber from cross cold thawing thing

Chemical constitution, the mole fraction adjuvant

The aluminium oxide-silicon oxide material:

0.50Al ₂O ₃+0.50SiO ₂

0.50Al ₂O ₃+ 0.50SiO ₂Nd ₂O ₃, 1% to 20% weight

0.50Al ₂O ₃+ 0.50SiO ₂Er ₂O ₃, 1% to 20% weight

0.60Al ₂O ₃+0.40SiO ₂

0.67Al ₂O ₃+0.33SiO ₂

0.69Al ₂O ₃+0.31SiO ₂

0.70Al ₂O ₃+0.30SiO ₂

0.71Al ₂O ₃+0.29SiO ₂

Aluminium oxide-Yttrium oxide material

0.63Al ₂O ₃+0.37Y ₂O ₃

0.63Al ₂O ₃+ 0.37Y ₂O ₃Nd ₂O ₃, 5mol% substitutes Y ₂O ₃

Other material

0.50Al ₂O ₃+0.50CaO

0.30Al ₂O ₃+0.70CaO

0.67MgO+0.33SiO ₂(forsterite)

0.50Al ₂O ₃+0.50La ₂O ₃

0.35Al ₂O ₃+0.35LiO+SiO ₂

Table III mullite composition optic fibre characteristic

Optical fiber state fibre diameter, _ m stretch breaking strength, Gpa

As draw 32.0 6.45

As draw 20.5 4.68

As draw 32.7 5.21

As draw 30.5 6.14

As draw 33.0 5.55

In 1100 ℃ of crystallizations 19.0 0.78

1200 ℃ of crystallizations 8.0 1.00

In 1200 ℃ of crystallizations 28.0 0.66

The description of other matrix fiber optic materials

Most of crystalline oxides laser hosts are not all produced the amorphous product, therefore also do not test the optical property of an amorphousness.Therefore in present document, also there is not data about this matrix optical property.Especially, the document is not recommended the fluorescence bandwidth of amorphousness.The applicant after deliberation the fluorescence spectrum of a lot of er-doped laser crystals of report, the applicant has used fluorescence spectrum in the given crystal to begin to calculate the corresponding amorphous fluorescence bandwidth of a material as information, wishes that the amorphous crystalline material also can have wide fluorescence bandwidth.

For example, the fluorescence spectrum of er-doped crystallization Luetcium aluminum garnet (LuAG) is illustrated among Figure 24, as A.A.Kaminsky, and et al., Investigation of stimulated emission fromLu ₃Al ₅O ₁₂Crystals with Ho ³⁺, Er ³⁺And Tm ³⁺Ions, phys.stat, sol. (a), Vol.18, K3l, 1973 is described.The LuAG spectral catalogue reveals a series of incoherent peak.Because in any crystal, all corresponding Er in each peak ^{3+ 4}I _13/2Energy level and ⁴I _15/2One or more different radiation relaxations between the sub-energy level of the Stark of energy level (Stark sub-level) change.Er in the material ³⁺Total fluorescence bandwidth Delta lambda to be confirmed as be the distance between the long and the shortest wavelength of fluorescence in the fluorescence spectrum.As can be seen from Figure 24, for er-doped LuAG, these wavelength are 1520 nanometers and 1670 nanometers, and bandwidth is 150 nanometers.Then, infer the approaching crystal bandwidth Delta lambda of measuring of erbium fluorescence bandwidth in the amorphous LuAG.In other words, the discrete fluorescence spectrum of inferring about 1550 nanometers of erbium in the LuAG crystal is transformed into total continuous spectrum of amorphous LuAG, and this compares to the characteristic of er-doped amorphous YAG to characteristic with er-doped crystallization YAG and the transition regime found is similar.

Aforementioned research has been used a large amount of er-doped crystal and has been determined multiple material with potential big fluorescence bandwidth.Especially, these researchs are used for the improvement of YAG, because the little chemistry of expectation YAG matrix improves favourable bandwidth fluorescence and the gain performance that (for example replacing lutetium with yttrium) will can not change er-doped amorphous YAG basically.

Table IV has been listed the bandwidth of the maximum of determining like this.The chemical formula of matrix fiber optic materials has been listed on Table IV first hurdle, and adulterant and the codopant that is included in the matrix fiber optic materials listed on Table IV second hurdle.Third column in the Table IV has been listed the fluorescence bandwidth Delta lambda of using said method to infer from disclosed fluorescence spectrum.Table IV the 4th hurdle represents whether ESA is observed in 980 nanometers in this crystal.Table IV has been listed non-crystalline material, and these non-crystalline materials have the fluorescence bandwidth of broad about 1550 nanometers.

The potential broadband of Table IV oxide

The Er3+ doped crystal	Adulterant	The fluorescence bandwidth
			?YAG	?Er	?160nm
?Y 2SiO 5	?Er	?160nm
			?Y 2SiO 5	?Er，Yb

?Lu 3Al 5O 12	?Er	?160nm
			?Y 3Ga 5O 12	?Er	?140nm
?Ca 2Al 2SiO 7	?Er	?130nm
			?Y 3Sc 2Ga 3O 12	?Er，(Yb，Cr)	?130nm
?Bi 4Ge 3O 12	?Er	?125nm
			?GdAlO 3	?Er	?125nm
?SrY 4(SiO 4) 3O	?Er	?125nm
			?LiYF 4	?Er	?110nm
?CaF 2-YF 3	?Er	?110nm
			?YVO 4	?Er	?90nm
?LiErYP 4O 12	?Er	?90nm

Although Table IV provides the information of the pumping ESA performance of seldom relevant research now, Table IV provides starting point for research EDFA broadband amorphous matrix.

Although be described here in conjunction with fiber amplifier, but the method for amplifying optical signals of the present invention can use integrated image intensifer to realize, these amplifiers are made with amorphous YAG bulk sample by using one of known several technology of prior art.

Claims (4)

1, a kind of on the light belt of widening is wide the method for amplifying light input signal, described method comprises:

To comprising the amorphous SrY that is mixed with rare earth ₄(SiO ₄) ₃Input optical signal in the optical waveguide of O material, described light signal comprises first light signal and second light signal with second wavelength that at least one has first wavelength, wherein said second wavelength is greater than about 125 nanometers of described first wavelength; And

Optical waveguide is applied pump light, make described waveguide provide the gain of light, so that amplify described first light signal and second light signal at least to light input signal.

2, the method for claim 1, wherein said amorphous SrY ₄(SiO ₄) ₃The O material is mixed with erbium.

3, a kind of on the light belt of widening is wide the image intensifer of amplifying light input signal, described image intensifer comprises:

The optical pumping source that optical pumping light is provided; With

One comprises a kind of amorphous SrY that is mixed with rare earth ₄(SiO ₄) ₃The optical waveguide of O material, described optical waveguide optical coupling receives the optical pumping light from optical pumping source, described optical waveguide receives the light input signal with a plurality of wavelength, described light input signal comprises that at least one first light signal with first wavelength and at least one have second light signal of second wavelength, described second wavelength is greater than about 125 nanometers of described first wavelength, described pump light has a pumping wavelength and intensity in the pumping wave strong point, make optical waveguide that the gain of light is provided, so that can amplify described first light signal and second light signal at least.

4, image intensifer as claimed in claim 3, wherein said amorphous SrY ₄(SiO ₄) ₃The O material is mixed with erbium.

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