U.S. patent application number 10/701175 was filed with the patent office on 2005-05-05 for method of fabricating optical fiber or optical device doped with reduced metal ion and/or rare earth ion.
Invention is credited to Ahn, Tae-Jung, Han, Won-Taek, Kim, Yune-Hyoun.
Application Number | 20050092029 10/701175 |
Document ID | / |
Family ID | 33418894 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050092029 |
Kind Code |
A1 |
Han, Won-Taek ; et
al. |
May 5, 2005 |
Method of fabricating optical fiber or optical device doped with
reduced metal ion and/or rare earth ion
Abstract
Disclosed is a method of fabricating an optical fiber or an
optical device doped with reduced metal ion and/or rare earth ion,
comprising steps of: forming a partially-sintered fine structure in
a base material for fabricating the optical fiber or the optical
device; soaking the fine structure into a doping solution
containing a reducing agent together with metal ion and rare earth
ion during a selected time; drying the fine structure in which the
metal ion and/or rare ion are/is soaked; and heating the fine
structure such that the fine structure is sintered.
Inventors: |
Han, Won-Taek; (Gwangju
Metropolitan City, KR) ; Kim, Yune-Hyoun; (Daejon
Metropolitan City, KR) ; Ahn, Tae-Jung; (Gwangju
Metropolitan City, KR) |
Correspondence
Address: |
Jonathan P. Osha
ROSENTHAL & OSHA L.L.P.
Suite 2800
1221 McKinney Street
Houston
TX
77010
US
|
Family ID: |
33418894 |
Appl. No.: |
10/701175 |
Filed: |
November 4, 2003 |
Current U.S.
Class: |
65/390 ; 65/399;
65/413; 65/414; 65/417; 65/421 |
Current CPC
Class: |
C03C 13/046 20130101;
C03B 37/01838 20130101; C03B 37/01433 20130101; C03B 2201/34
20130101; C03C 25/601 20130101; C03B 2201/42 20130101; C03B 2201/28
20130101; C03B 2201/10 20130101; C03B 2201/31 20130101 |
Class at
Publication: |
065/390 ;
065/413; 065/414; 065/417; 065/421; 065/399 |
International
Class: |
C03B 037/018 |
Claims
What is claimed is:
1. A method of fabricating an optical fiber or an optical device
doped with reduced metal ion and/or rare earth ion, comprising
steps of: forming a partially-sintered fine structure in a base
material for fabricating the optical fiber or the optical device;
soaking the fine structure into a doping solution containing a
reducing agent together with metal ion and rare earth ion during a
selected time; drying the fine structure in which the metal ion
and/or rare ion are/is soaked; and heating the fine structure such
that the fine structure is sintered.
2. The method of claim 1, wherein the reducing agent is hydrocarbon
compounds.
3. The method of claim 2, wherein the hydrocarbon compound is any
one selected from the group consisting of glucose, sucrose,
glycerine, dextrin, benzene, phenol, hexane, toluene, stylene, and
naphthalene.
4. The method of claim 1, where the reducing agent is alkoxide
compounds.
5. The method of claim 4, wherein the alkoxide compound is any one
selected from the group consisting of TEOS (tetraethyl
orthosilicate), TMOS (tetramethyl orthosilicate), TEOC (tetraethyl
orthocarbonate), and TMOC (tetramethyl orthocarbonate).
6. The method of claim 1, wherein the metal ion and/or rare earth
ion is at least one selected from the group consisting of Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Sc, Ti, V, Cr,
Mu, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In,
Sn, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi and a mixture
thereof.
7. The method of claim 1, wherein a base material for fabricating
the optical fiber or the optical device has a basic composition
comprising a silicon oxide or a composite oxide of a silicone oxide
and an oxide; in which the oxide is at least one selected from the
group consisting of germanium oxide (GeO.sub.2), boron oxide
(B.sub.2O.sub.3), phosphorous oxide (P.sub.2O.sub.5), and titanium
oxide (TiO.sub.2).
8. The method of claim 1, wherein a base material for fabricating
the optical fiber or the optical device has a basic composition
selected from silica (SiO.sub.2), germanosilicate
(SiO.sub.2--GeO.sub.2), phosphorosilicate
(SiO.sub.2--P.sub.2O.sub.5), phosphoroger anosilicate
(SiO.sub.2--GeO.sub.2--P.sub.2O.sub.5), borosilicate
(SiO.sub.2--B.sub.2O.sub.3), borophosphorosilicate
(SiO.sub.2--P.sub.2O--B.sub.2O.sub.3), borogermanosilicate
(SiO.sub.2--GeO.sub.2--B.sub.2O.sub.3), titanosilicate
(SiO.sub.2--TiO.sub.2), phosphorotitanosilicate
(SiO.sub.2--TiO.sub.2--P.- sub.2O.sub.5), or borotitanosilicate
(SiO.sub.2--TiO.sub.2--B.sub.2O.sub.3- ).
9. The method of claim 1, wherein, the step of forming the
partially-sintered fine structure in the base material is performed
by a process selected from the group consisting of MCVD (modified
chemical vapor deposition), VAD (vapor-phase axial deposition), VOD
(outside vapor deposition), and FHD (flame hydrolysis
deposition).
10. A method of fabricating an optical fiber or an optical device
doped with reduced metal particle and/or rare earth element,
comprising steps of: forming a partially-sintered fine structure in
a base material for fabricating the optical fiber or the optical
device; soaking the fine structure into a doping solution
containing a reducing agent having strong reduction potential
together with metal ion and rare earth ion during a selected time,
drying the fine structure in which the metal ion and/or the rare
earth ion is/are soaked; and heating the fine structure such that
the fine structure is sintered, thereby forming the metal particle
and/or the rare earth elements.
11. The method of claim 10, wherein the reducing agent is
hydrocarbon compounds.
12. The method of claim 10, where the reducing agent is alkoxide
compounds.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to a technology for
fabricating an optical fiber or an optical device, and more
particularly to a method of fabricating an optical fiber or an
optical device doped with reduced metal ion(s) and/or rare earth
ion(s).
[0003] 2. Description of the Related Art
[0004] An optical fiber containing metal ion and/or rare earth ion
is brought under a special optical fiber, since it can be variously
applied to an optical amplifier or an optical switching device etc.
Therefore, much of the research in this area has been
performed.
[0005] One of the research projects is a technique of reducing
doped metal ion and/or rare earth ion, Generally, an atom has a
different energy level distribution depending on its valence, and
therefore has different spectroscopic characteristics such as light
absorption and light emission. Accordingly, a little more diverse
light absorption and light emission can be obtained by utilizing
the change of valence and thereby the optical fiber and the optical
device having various optical amplification and optical switching
characteristics can be obtained.
[0006] As an example, let us consider rare earth ions, when a rare
earth ion has the valence of 3+, the light absorption
characteristic due to electronic transition between 4.function.
electron orbit and 5d electron orbit occurs only in an ultraviolet
wavelength region, whereas when the valence of the rare earth ion
changes to 2+ ion, such an light absorption characteristic occurs
in both visible and infrared wavelength regions. For this reason, a
technique of making doped metal ion and rare earth ion with desired
valences, respectively is required. Furthermore, every atom has its
own valence states in which the atom is mainly existed in nature
and thus a specific process is required in order to transfer the
valence into another valences.
[0007] For example, most of the rare earth ions have the valence of
3+. In order to stably transfer the valence of 3+ into the valence
of 2+, 1+ or 0, it is necessary to reduce the rare earth ions.
There have been proposed various reduction treatment methods as
described below.
[0008] Firstly, there is a method of applying gamma rays to the
rare earth metal ion having the valence of 3+. For example, it is
reported that Tm.sup.2+ can be obtained, if the gamma rays is
applied to a CaF.sub.2 crystal containing Tm.sup.3+.
[0009] However, in this method, there is a problem that a gamma ray
source is dangerous to handle and the cost required in handling it
safely is thus expensive.
[0010] Secondly, there is another method in which an aerosol type
material is utilized. In this method, a MCVD (modified chemical
vapor deposition) process is indispensable. In other words, this
method includes the MCVD process in which a glass layer containing
rare earth ions is deposited in a quartz glass tube, using material
having aerosol formulation which generates carbon, together with a
powder which generates rare earth ion and glass when fired. Then,
processes of removing the carbon and OH radical, sintering the
glass and collapsing the glass tube are, in turn, performed to thus
obtain an optical fiber preform. For example, in a glass optical
fiber having SiO.sub.2--Al.sub.2O.sub.3 components, Eu.sup.2+ and
SM.sup.2+ are reduced from Eu.sup.3+ and Sm.sup.3+,
respectively.
[0011] To date, this method which utilizes the material having
aerosol formulation is performed through only the MCVD process. A
desired rare earth ion material having aerosol formulation and an
additional apparatus for supplying material having aerosol
formulation are needed.
[0012] Further, there is a method of injecting a mixture of H.sub.2
and Ar gases and obtaining the reduced rare earth ion during
melting of glass. For example, in a glass having
SiO.sub.2--Al.sub.2O.sub.3 components or SiO.sub.2--B.sub.2O.sub.3
components, Sm.sup.2+ is reduced from Sm.sup.3+.
[0013] In this method, there is a problem that processes of
fabricating the optical fiber preform are complicated in comparison
with the conventional processes and are not yet commercialized.
SUMMARY OF THE INVENTION
[0014] Therefore, it is an object of the present invention to
provide a method of fabricating an optical fiber or an optical
device, in which metal ion and/or rare earth ion safely and
facilely reduced, in comparison with the prior art methods,
together with the utilization of the prior art processes of
fabricating the optical fiber and/or the optical device.
[0015] To achieve the aforementioned object of the present
invention, a method according to the present invention is
characterized by forming a partially-sintered fine structure in a
base material for fabricating an optical fiber or an optical device
and soaking the fine structure into a doping solution containing a
reducing agent together with metal ion and/or rare earth ion during
a selected time, thus doping the fine structure with the metal ion
and/or rare earth ion together with the reducing agent. Therefore,
reduced metal ion and/or rare earth ion through the reducing agent
is obtained.
[0016] One method according to the present invention of fabricating
an optical fiber or an optical device doped with reduced metal ion
and/or rare earth ion comprising the steps of: forming a
partially-sintered fine structure in a base material for
fabricating the optical fiber or the optical device; soaking the
fine structure into a doping solution containing a reducing agent
together with metal ion and rare earth ion during a selected time;
drying the fine structure in which the metal ion and rare ion is
soaked; and heating the fine structure such that the fine structure
is sintered.
[0017] Another method of fabricating an optical fiber or an optical
device doped with reduced metal particle and/or rare earth element,
comprising steps of: forming a partially-sintered fine structure in
a base material for fabricating the optical fiber or the optical
device; soaking the fine structure into a doping solution
containing a reducing agent having strong reduction potential
together with metal ion and rare earth ion during a selected time;
drying the fine structure in which the metal ion and/or the rare
earth ion is/are soaked; and heating the fine structure such that
the fine structure is sintered, thereby forming the metal particle
and/or the rare earth elements.
[0018] Preferably, the reducing agent is hydrocarbon compounds.
Glucose, sucrose, glycerine, dextrin, benzene, phenol, hexane,
toluene, stylene, naphthalene, and the like are exemplified.
[0019] In addition, the reducing agent is alkoxide compounds. TEOS
(tetraethyl orthosilicate), TMOS (tetramethyl orthosilicate), TEOC
(tetraethyl orthocarbonate), TMOC (tetamethyl orthocarbonate) and
the like are exemplified.
[0020] Preferably, the metal ion and/or rare earth ion is at least
one ion selected from the group consisting of Ce, Pr, Nd, Pm, Sm,
Eu, Gd, Th, Dy, Ho, Br, Tm, Yb, Lu, Al, Sc, Ti, V, Cr, Mn, Fe, Co,
Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Hf, Ta,
W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi and a mixture thereof.
[0021] Further, the base material for fabricating the optical fiber
or the optical device has a basic composition comprising a silicon
oxide or a composite oxide of a silicone oxide and an oxide; in
which the oxide is at least one selected from the group consisting
of germanium oxide (GeO.sub.2), boron oxide (B.sub.2O.sub.3),
phosphorous oxide P.sub.2O.sub.5), and titanium oxide
(TiO.sub.2).
[0022] Preferably, the base material for fabricating the optical
fiber or the optical device has a basic composition selected from
silica (SiO.sub.2), germa osilicate (SiO.sub.2--GeO.sub.2),
phosphorosilicate (SiO.sub.2--P.sub.2O.sub.5),
phosphorogermanosilicate (SiO.sub.2--GeO.sub.2--P.sub.2O.sub.5),
borosilicate (SiO.sub.2--B.sub.2O.sub.3), borophosphorosilicate
(SiO.sub.2--P.sub.2O.sub.5--B.sub.2O.sub.3), borogermanosilicate
(SiO.sub.2--GeO.sub.2--B.sub.2O.sub.3), titanosilicate
(SiO.sub.2--TiO.sub.2), phosphorotitanosilicate
(SiO.sub.2--TiO.sub.2--P.- sub.2O.sub.5), or borotitanosilicate
(SiO.sub.2--TiO.sub.2--B.sub.2O.sub.3- ).
[0023] Preferably, the step of forming the partially-sintered fine
structure in the base material for fabricating the optical fiber or
the optical device is performed by a process selected from MCVD
(modified chemical vapor deposition), VAD (vapor-phase axial
deposition), VOD (outside vapor deposition), FHD (flame hydrolysis
deposition), etc.
[0024] The optical device in the present invention includes a
planar optical amplifier, an optical communication laser, and a
planar optical switch device, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above objects and another advantages of the present
invention will become more apparent by describing in detail
preferred embodiments thereof with reference to the attached
drawings in which:
[0026] FIG. 1 is a schematic view showing an apparatus for
performing processes of the present invention;
[0027] FIG. 2 is graph showing a light absorption spectrum of an
optical fiber doped with reduced rare earth ion(Tm.sup.+2)
fabricated by a first embodiment of the present invention;
[0028] FIG. 3 is a graph showing a light absorption spectrum of an
optical fiber fabricated by a comparative example 1 without using
the reducing agent;
[0029] FIG. 4 is a graph showing a light absorption spectrum of an
optical fiber doped with reduced rare earth ion (Eu.sup.+2)
fabricated by a second embodiment of the present invention;
[0030] FIG. 5 is a graph showing a light absorption spectrum of an
optical fiber fabricated by a comparative example 2 without using
the reducing agent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Now, preferred embodiments of the present invention will be
described in detail with reference to the annexed drawings.
[0032] A method of the present invention comprises a step of
forming a partially-sintered fine structure in a base material for
fabricating an optical fiber or an optical device, and a step of
soaking the fine structure in a doping solution containing a
hydrocarbon compound as a reducing agent together with metal ion
and/or rare earth ion for 1 to 1.5 hours. That is, the fine
structure of the base material is doped with the reducing agent
together with metal ion and/or rare earth ion and the metal ion
and/or rare earth ion reduced by the doped reducing agent is
thereby obtained.
[0033] The method of the present invention is a modification of a
solution doping technique for adding the rare earth ion and/or
metal ion to the optical fiber or the optical device. This solution
doping technique is a method of doping the metal ion or the rare
earth ion in an optical fiber core, which can be utilized with any
of conventional methods of fabricating an optical fiber preform,
such as MCVD (modified chemical vapor deposition), VAD (vapor-phase
axial deposition), OVD (outside vapor deposition), etc. The
solution doping technique is also used as the technique which may
dope all of the rare earth ion and/or the metal ion, capable of
being formed into a solution type, even in a method of fabricating
a plane glass optical device through a FHD (flame hydrolysis
deposition) process.
[0034] For example, the solution doping technique please refer to
J. E. Townsend, et al. "Solution for fabrication of rare earth
doped optical fibers", Electron, Lett., Vol. 23, p.p. 329-331,
1987) through the MCVD process is as follows. Herein, in order to
obtain reduced rare earth ion, an aqueous solution in which sucrose
as a strong reducing agent is dissolved together with rare earth
chloride is used as a doping solution. First, a core layer
partially sintered and then having a plurality of pores is formed
in a silica tube using the conventional MCVD process (please refer
to MacChesney et. al., "Optical fiber fabrication and resulting
product", U.S. Patent, 1997). Then, the silica tube is filled with
the aqueous solution in which the sucrose is dissolved together
with the rare earth chloride. The aqueous solution is hold for 1 to
1.5 hours in order for the solution to be sufficiently permeated
into the pores of the core layer and is then discharged. As a
result, the doping solution remains in the pores. The core layer
doped with the aqueous solution is dried while the silica tube is
hold at a temperature of 100 to 250.degree. C. with the passage of
an inert gas such as helium gas only, using the MCVD process. At
this time, ethanol and moisture is removed. Sequentially, using
hydrogen-oxygen flames, the core layer is heated at a high
temperature of 2000.degree. C. until carbon generated from the
sucrose is removed and the core layer is then completely sintered
(referring to M. F. Yan, et al., "Sintering of optical wave-guide
glasses", J. of Mater. Sci., p.p. 1371-1378, 1980). After that, the
optical fiber preform is fabricated through a collapsing step in
which the tube is heated to more than 2200.degree. C. with the
continuous purging of the inert gas, using the hydrogen-oxygen
flames. The optical fiber preform is drawn to produce the optical
fiber doped with the reduced rare earth ion.
[0035] The sucrose contained in the doping solution is composed of
C, H and O components. During the above drying step, most of the H
and O components among the above components are removed and only
the carbon (C) is remained. The carbon (C) is combined with Oxygen
(O.sub.2) remained at the high temperature of about 2000.degree. C.
to form carbon monoxide (CO), and thus carbon monoxide reduces the
doped rare earth ion. At this time, the reaction temperature at
which the carbon monoxide (CO) is formed is decided within the
possible range of reduction of the rare earth ion, using an
Ellingham Diagram. At the same time, a strong reduction atmosphere
is created by injecting only the inert gas into the silica glass
tube, so that the carbon (C) can be fully participated in the
reduction reaction of rare earth ion. Further, preferably, the
inert gas only is also passed through during the collapsing step
for fabricating the optical fiber preform, thereby creating a
reduction atmosphere at its maximum.
Embodiment 1
[0036] First, thulium chloride hexahydrate (TmCl.sub.3.6H.sub.2O)
of 0.04M and sucrose (C.sub.12H.sub.22O.sub.11) of 2.17M are
dissolved in deionized water to prepare a doping solution
containing rare earth ion (Tm.sup.3+) and the sucrose as a reducing
agent. Herein, a hydrocarbon compound or an alkoxide compound is
used as the reducing agent.
[0037] As shown in FIG. 1, a porous fine structure is formed
through an MCVD process at an inner wall of a silica glass tube
having an inner diameter of 19 mm and an outer diameter of 25 mm so
that the portion thereof to form an optical fiber core has a basic
glass composition of SiO.sub.2--GeO.sub.2. The doping solution
fabricated is injected into the above glass tube and then
discharged after 1 hour. Then, the core layer is dried by heating
the glass tube again at a temperature of 100 to 250.degree. C.
using the MCVD apparatus with the purge of only helium gas through
the glass tube.
[0038] Then, the above sintering step and collapsing step are
repeatedly performed 8 times and 15 times, respectively, at a
temperature of 2000.degree. C., thereby obtaining the optical fiber
preform doped with Tm.sup.2+ ion. The optical fiber preform is
drawn to fabricate the optical fiber. Herein, even when a sintering
step is carried out at a temperature of 1600 to 2200.degree. C.,
the same result is also obtained.
[0039] A light absorption spectrum of the optical fiber fabricated
using the doping solution containing the sucrose as a reducing
agent is shown in FIG. 2. Light absorption spectrum of FIG. 2 shows
that light absorption spectrum shown at 465 nm, 680 nm, 785 nm,
1210 nm, and 1600 nm is formed by Tm.sup.3+ ion, and light
absorption spectrum distributed in the broad range of 400 nm and
900 nm is formed by Tm.sup.2+ ion.
COMPARATIVE EXAMPLE 1
[0040] Thulium chloride hexahydrate (TmCl.sub.3.6H.sub.2O) of 0.04M
and aluminum chloride hexahydrate (AlCl.sub.3.6H.sub.2O) of 0.19M
are dissolved in ethanol to prepare a doping solution without
containing the sucrose as the reducing agent.
[0041] A core layer having a porous fine structure is formed at an
inner wall of a silica glass tube in the same method as the
embodiment 1. The fabricated doping solution is injected into the
glass tube and then discharged after 1 hour. Then, the core layer
is dried together with the purge of helium, oxygen and chlorine
through the tube.
[0042] Then, the above sintering step and collapsing step are
repeatedly performed 3 times and 7 times, respectively, at a
temperature of 2000.degree. C., thereby obtaining the optical fiber
preform doped with Tm.sup.3+ ion. The optical fiber preform is
drawn to fabricate the optical fiber.
[0043] A light absorption spectrum of the optical fiber fabricated
by using the doping solution without containing the sucrose as the
reducing agent is shown in FIG. 3. Differently from the result of
the embodiment 1 using the reducing agent, FIG. 3 shows only light
absorption spectrum according to Tm.sub.3+ ion.
Embodiment 2
[0044] Europium chloride (EuCl.sub.3.xH.sub.2O) of 0.097M and
sucrose (C.sub.12H.sub.22O.sub.11) of 0.518M are dissolved in
deionized water to prepare a doping solution containing rare earth
ion (Eu.sup.3+) and the sucrose as a reducing agent.
[0045] Then, the optical fiber doped with Eu.sup.2+ ion is
fabricated by the same processes as in the embodiment 1.
[0046] A light absorption spectrum of the optical fiber fabricated
by using the doping solution containing the sucrose as the reducing
agent is shown in FIG. 4. In the light absorption spectrum of FIG.
4, the light absorption spectrum distributed in the broad range of
600 nm and 1200 nm is formed by Eu.sub.2+ ion. This spectrum is not
shown in the case of Eu.sup.3+ ion.
COMPARATIVE EXAMPLE 2
[0047] Europium chloride hydrate (EuCl.sub.3.xH.sub.2O) of 0.097M
and aluminum chloride hexahyrate (AlCl.sub.3 6H.sub.2O) of 0.518M
are dissolved in ethanol to prepare a doping solution without
containing the sucrose as the reducing agent.
[0048] Then, the optical fiber doped with Eu.sup.3+ ion is
fabricated by the same processes as in the comparative 1.
[0049] A light absorption spectrum of the optical fiber fabricated
by using the doping solution without containing the sucrose as the
reducing agent is shown in FIG. 5. Differently from the result of
the embodiment 2 using the reducing agent, FIG. 5 shows only light
absorption spectrum according to Eu.sup.3+ ion.
[0050] The above embodiments 1 and 2 illustrate that the optical
fibers perform doped with Tm.sup.2+ ion and Eu.sup.+2 ion,
respectively, by the doping solutions containing the reducing
agents are obtained. Depending on the intensity of reduction
potential which the reducing agent has, it is confirmed that metal
ion or rare earth ion having 3+ valence is changed to 2+ valence or
1+, in some cases to "0" valence. When the metal ion or rare the
earth ion is reduced to "0" valence, an optical fiber preform or an
optical device preform doped with metal particle or rare earth
element is formed.
[0051] As described above, the present invention can fabricate an
optical device doped with reduced metal ion and/or rare earth ion
having a desire valence by a facile solution doping technique.
[0052] According to the present invention, an optical fiber or an
optical device doped with metal ion and/or rare earth ion reduced
by the facile solution doping technique, with no need to change the
conventional MCVD, VAD, OVD processes, etc. may be fabricated.
[0053] While the present invention has been described in detail, it
should be understood that various changes, substitutions and
alterations can be made hereto without departing from the spirit
and scope of the invention as defined by the appended claims.
* * * * *