Note: Descriptions are shown in the official language in which they were submitted.
1 16893~
1 BACKGROUND OF ~HE INVENTION
1. FIE~D OF TH~ INVENTION
This invention relates to an optical transmission
glass fiber and a process for the production of the same
and more particularl~, it is concerned with a radiation
resistance optical transmission glass fiber which is used
in optical communication systems under radiations such as
X-ra~s and ~-rays, image transmission s~stems or illumina-
tion systems, and a process for the production of the same.
~he range of use of optical transmission glass
fibers is increasing in the fields of the control lines of
air planes, the control lines of ships, the wirings of com-
puters and the control or communication lines of works or
buildings in addition to the fields of telegraphs and tele-
phones in the prior art, since they have various advantages
that signals of large capacity can be made with a small
space and they are non-inductive due to electrical insula-
tion and show a light weight as well as an excellent flexi-
bility because of narrow glass fibers. Under the situation,
much endeavor has been made to improve the optical transmi-
ssion glass fibers and their properties are thus elevated
in transmission loss, broad band transmission and practical
strength. Of late, therefore, the optical transmission
glass fibers have been put to practical use.
2. DESCRIPTION OF TH~ PRIOR ART
Up to the present time, the following glass fibers
have been known as an optical transmission glass fiber:
(1) Fiber consisting of a core of SiO2 glass and a
cladding of silicone resin,
(2) Quartz glass fiber consisting of a core of
P2O5-GeO2-SiO2 or P2O5-B2O~-GeO2 and a cladding of B2O3-SiO2
--1-- ,!,~lr
1 ~8938
l or B2o3-p2o5-sio2~
(3) Quartz glass fiber consisting of a core of SiO2
glass and a cladding of B203 and/or ~-doped SiO2 glass,
(4) Multicomponent glass fiber in which both of a
core and cladding consist of a borosilicate glass or a soda
lime glass and
(5) Eigh silicate glass fiber consisting of a core
of Cs2-B203-SiO2 glass and a cladding of B203-SiO2 glass.
~ atel~, it has strongl~ been required to use these
optical glass fibers, in particular, under radiation of
X-rays in medical or indu~trial fields or r-ra~s in the
fields of handling nuclear reactors or radioactive element
so as to make the best use of the electrical insulation and
flexibility of the optical glass fiber. In the presence of
such a radiation, howe~er, glass meets with its structural
defects to result in a very large transmission loss. In
particular, the abo~e described glass fibers of the types
(2), (4) and (5) or plastics fibers meet with a largel~
increased transmission loss and those of the types (1~ and
(3) also meet with a considerably increased transmission
109s. Increase of the transmission loss in these fibers is
discussed b~, for example, E. J. Friebele et al in "~aser
Focus" Sept., 1978, page 50-56.
Therefore, fibers which have hitherto been proposed
or developed cannot be used in the presence of radiations
because of their largely increased transmission loss. In
the s~nthesis of the prior art glass fibers, halogen co~-
pounds such as SiCl4 with a high cohesive strength are used
as a raw material and OH groups are intended to be decreased
for the purpose o~ lowering the transmission loss, but the
hydrolysis or thermal oxidation is carried out at a hightempe-
rat~re such as higher than 1650 ~, which tends to cause structural
--2--
~ 168938
l defects such as oxygen defect. Thus, the quantity of defects
produced by radiation i8 large while the diminishing speed
of the defects is tos low considering for the quantit~ of
the defects produced by radiation, resulting in increase of
the transmission loss.
On the other hand, as a window glass under radia-
tion, there is used a glass doped with CeO2 or Sb203 whereb~
electrons or positive holes produced b~ radiation damage are
trapped b~ the electron capture centers of Ce4+ and the posi-
tive hole capture centers of Ce3 and not trapped by lattice
defects$ thus the structural defects being held as it is and
suppressing coloration of the glass. However, the composi-
tion of such a window glass is not suitable for an optical
transmission fiber since hardly purified compounds are used
as a starting material and the length of transmission of
light is inferior b~ the order of 102 _ 105sO that the loss
due to radiation be too large (~ 10 dB/km at 10 R-y ).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide
an optical transmission glass fiber and a method of produ-
cing the same, which overcome the heretofore noted disadvan-
tages.
It is another object of the present invention to
provide an optical transmission glass fiber in which light
advances concentrically in a part consisting of a high purity
silica glass free from structural defects so as to minimize
the influence of the structural defects.
It is a further object of the present invention to
provide an optical transmission glass fiber in which OH
groups or OD groups are somewhat incorporated to promote
diminishing of defects produced and excited by radiation and
- - ,
1 168938
1 to decrease further the transmission loss.
It is a still further object of the present inven-
tion to produce an optical wave guide with a decreased radi-
ation damage by the use of a glass with deoreased structural
defects, which is synthesized at a relatively low tempera-
ture, without using as a raw material compounds decomposable
at a high temperature auch as chlorides.
It is a still further obJect of the present inven-
tion to provide a process for the production of an optical
fiber having an SiO2-Sb203 glass b~ lowering the synthesis
temperature of the glass to suppress formation of structural
defects and to decrease radiation damages.
It is a still further object of the present inven-
tion to provide a process for the production of an optical
transmission glass fiber by using as a core a fiber consis-
ting of an SiO2 glass containing Ce2O3 + CeO2.
These objects can be attained by a radiation resi-
stant optical glass fiber comprising a higher refractive
index part and a lower refractive index part, the higher
.
refractive index part consisting predominantly of a silica
glass synthe~ized by oxidation reaction of a hydride such as
SiH4 or an organic compound such as 9i(0C ~ 5)4 and a process
for the production of a radiation resistant optical trans-
mission glass fiber which comprises feeding an organic
compound such as Si(OC2H5)4 or a hydride such as SiH4 into
an oxyhydrogen flame consisting of H2 and/or D2 and 2 to
synthesize glass particles, depositing the glass particles
on a starting member to form a high refractive index part of
silica glass and combining the higher refractive index part
with a lower refractive index part to form one body as a
fiber, or which comprises oxidizing SbH3 gas and SiH4 gas or
Si(OC2H5)4 to form an Sb2O3_SiO2 glass, depositing this glass
.
1 16893~
1 and an SiO2 glass obtained b~ oxidizing SiH4 gas or Si(OC ~ 5)4
and subjecting to melt spining.
BRI~F D~SCRIP~ION OF THE DRAWING
~ he accompanying drawings are to illustrate the
present invention in more detail.
Fig. 1 (A), (B) and (C) are cross-sectional views
of embodiments of the optical transmission fiber accoraing
to the present invention;
Fig. 2 is a cross-sectional view of the optical
glass fiber of th0 present invention to illustrate the pri-
mar~ coating and secondary coating;
Fig. 3 (a) is a graph showing the relationship
between the increased quantity of transmission loss and the
~-rays irradiation time for comparison of the optical fiber
of the present invention with the prior art;
Fig. 3 (b) is a graph showing the same relationship
as that of Fig. 3(a) but in the case of an intermittent
irradiation;
Fig. 4 (a) is a graph showing the relationship
between the increased quantity of transmission 105s and the
~-ra~s irradiation time for comparision of the optical fiber
of the present invention with the prior art in a case where
the cladding and jacket consist of glass;
Fig. 4 (b) is a graph showing the same relationship
as that of Fig. 4(a) but in the case of using other optical
fibers;
Fig. 5 and ~ig. 6 are cross-sectional views of o~her
embodiments of the optical transmission glass fibers accor-
ding to the present invention;
Fig. 7 is a schematic view of an apparatus suita-
ble for the production of the optical fiber according to the
~ ~8938
l present invention b~ VAD method;
DE~AILED D~SCRIP~ION OF THE INV~N~ION
In accordance with the present invention, there is
provided a radiation resistant optical glass fiber compri-
sing a higher refractive index part and a lower refractive
index part, the higher refractive index part consisting pre-
dominantl~ of a silica glass synthesized by oxidation reac-
tion of a hydride such as SiH4 or an organic compound such
as Si(OC2H5)4 at a relatively low temperature such as less
than 1550 C, preferably less than 1400 a and a process for
the production of a radiation resistant optical transmission
glass flber, which comprises feeding an organic compound
such as Si(OC2H5)4 or a hydride such as SiH4 into an
ox~hydrogen flame consisting of H2 and/or D2 and 2 to syn-
thesize glass particles, dipositing or accumulating the glass
particles on a starting member to form a higher refractive
index part of silica glass and combining the higher refrac-
tive index part with a lower refractive index part to form
one body as a fiber.
In the present invention, a glass with a decreased
structural defect by lowering the synthesis temperature
thereof is used without using a compound decomposable at a
high temperature such as chlorides thus obtaining a glass
fiber with a decreased radiation damage and, if necessary,
OH groups or OD groups are incorporated in the glass to some
extent so that the diminishing speed of defects produced and
excited by radiation is promoted and the transmission loss
is further decreased.
Furthermore, the present invention provides a process
of producing a radiation resistant optical fiber which com-
prise oxidizing SbH3 gas with SiH4 gas or/and Si(OC2H5)4
1 ~893~
1 gas to form an Sb2O3-SiO2 glass, depositing the resulting
glass and another SiO2 glass obtained by oxidizing SiH4 gas
or/and Si~oC2H5)4 gas, and then subjecting the accumulate
: to melt spinning.
In the present invention, the synthesis temperature
of the glass is lowered for example, to lower than 1600C,
preferably lower than 1400C, in an optical fiber having
an SiO2-Sb2O3 glass and the structural defects are thereby
suppressed to decrease the radiation damage. In this glass
?O composition, O~ groups or OD groups are optionally incor-
porated to increase the diminishing speed of defects produced
and excited by radiation and to suppress increase of the
transmission loss. The transmission loss due to structural
defects may be minimized by doping a silica glass with
Sb2O3 only as a dopant so that light advances concentrically
in a part consisting of a high purity silica glass free from
other impurities than OH group or OD group.
In addition, the present invention provides a radia-
tion resistant optical transmission fiber comprising a higher
~0 refractive index part and lower refractive index part, the
higher refractive index part consisting predominantly of a
Ce-doped SiO2 glass synthesized by oxidizing or decomposing
a hydride such as SiH4 or an organic compound such as
Si~O2 ~5)4 with a Ce-containing compound at a relatively low
temperature such as lower than 1600C, preferably 1100 to
1550C. That is to say, a SiO2 glass containing preferably
0.001 to 1~ of Ce2O3 and CeO2 is prepared whereby electrons
and positive holes are trapped by the electron capture center
of Ce and the positive hole capture center of Ce3 with
holding the effect of suppressing increase of the transmi-
ssion loss. Using this glass as a core, an optical trans-
mission fiber is produced wherein increase of the transmi-
-- 7 --
1 16893~
.
l ssion loss is suppresed even under radiation.
Examples of the other hydrides which can be used inthe present invention are SiH2Cl2, SiHC13, Si2H6, Si~H8 and
the like~ Examples of the other organic compounds which can
be used in the present invention are CH~C13Si, CH3Cl2SiH,
CH3ClSiH2, aH3SiH~ C2H5Cl3Si. C2H5~l2Si~ 2 5 2
C2H5~iH3' C3H7C13~i~ C3~7Cl2SiH, C3H7clSiH2,
3 7 3~ 4 9 l2SiH~ C4HgSiH3~ C5H11Cl2SiH, C5H11SiH
C6H13SiH3~ C7~15SiH3, CgH17SiH3~ (CH30)4Si, and the like.
Fig. 1 ~A) shows one embodiment of the optical
fiber of the present invention~ in which core 11A is of a
high purity silica glass containing some OH groups or OD
groups and synthesized at a low temperature and cladding 12
is of a silicone resin or fluorine resin. Fig. 1 (B) shows
another embodiment of the optical fiber of the present inven-
tion in which core 11~ is of a high purity silica glass con-
taining some OH groups or OD groups and synthesized at a low
temperature and cladding 12B is of a high purity silica
glass containing any one of ~23~ F~ B203-F and P205-~ and
synthesized at a low temperature, which may contain some OH
groups or OD groups~ Fig~ 1 (C) shows a further embodiment
of the optical fiber of the present invention, in which 11C
is the same as 11B, 12C is the same as 12B and jacket 13~ is
of, for example, a silica glass. ~hese glass fibers are
radiation resistant, but in order to prevent from deteriora-
tion of the mechanical strength thereof, it is desirable to
provide the outside of glass fiber 21 as shown in ~ig. 2 with
a primary coating 22 of a thermosetting resin such as polyi-
mide resin or epoxy resin (which should be coated directlyafter forming the glass fiber) and further with a thermo-
plastic resin 23 such as ethylene propylene rubber or brid-
ged polyethylene by extrusion.
9 3 8
1 Methods of making a glass rod or preporm as a raw
material of glass fiber, and a glass fiber will now be illu-
strated. In one example, H2 and/or D2 as a combustion gas
and 2 as a combustion aid are fed to a burner consisting
of a quartz glass tube to form a flame, into which an orga-
nic compound such as ~i(OC2H5)4 or hydride such as SiH4 that
is decomposable at a relatively low temperature is introduced
by the aid of a suitable carrier gas to effect a flame oxida-
tion reaction and to form a fine powder of silica glass con-
taining some OH groups and/or OD groups, and the resulting
powder is blown against and deposited in the state of fused
glass on a revolving target by O-CVD (Outside Chemical Vapor
Deposition) method or VAD (Vapor-phase Axial Deposition)
method. Depending on the deposition method, any form of round
bars or cylinders can be obtained as well known in the art.
In another example, a gaseous Si-containing compound such
as Si(OC2~5)4 or SiH4 and 2 gas are introduced into the
above described oxyhydrogen flame and a glass fine powder
mass is prepared by OLCVD method of VAD method, which is then
subjected to sintering and clear vitrification in an atmos-
phere containing some H2O and/or D2O, or some H2 and/or D2,
thus obtaining a high purit~ silica glass bar containing
large amounts of OH groups and/or OD groups. ~hen, the sur-
face of this glass bar is subjected to cylinder grinding or
polishing and further to HF polishing, CO2 laser polishing
or flame polishing to obtain a clean and smooth glass bar.
~his glass bar is subjected -to melt spinning in a furnace at
a high temperature and coated with a silicone resin or fluo-
rine resin before taking up the fiber on a reel, followed by
baking, to thus obtain a glass fiber of the present invention.
In a further exmple, a gaseous raw material containing at
least one of F, B and P and a gaseous raw material containing
~ 168938
l silicon such as Si(OC2~5)4 or SiH4 with 2 a
ced into a plasma flame of high freguency plasma torch by
the aid of a suitable carrier gas and a silica glass doped
with any one of F, B203, B203-F and P205-F is deposited on
the outer surface of a rotating glass rod synthesized as
described above. During the same time, if necessary, a com-
pound containing H or D such as H20 or D20 can be added to
synthesize a glass containing OH groups or OD groups, from
which a glass fiber of the present invention can be obtained
through melt spinning. In this case, compounds such as SiH4,
SiF4, BF3, B2H6, PF3 and the like are introduced into an
oxyhydrogen flame made up of H2 and/or D2 and 2 to synthesize
silica glass fine particles doped with any one of F, B20~,
B203-F and P205-F and deposited in fused state on a glass
rod as a core described above. Of course, the above described
glass fine particles can be deposited as a powder soot, follo-
wed by sintering in an atmosphere containing H20 or D20, thus
obtaining a transparent glass. Subsequently, on the outer
surface of this synthesized glass rod is deposited a silica
glass by introduc:ing a gaseous raw material containing Si such
as SiCl4 with 2 by the aid of a carrier gas into a flame or
plasma flame. During the same time, if necessary, ~iCl4,
AlCl3 or ZrCl4 can be added to deposit a glass doped with ~iO2,
Al203 or ZrO2. In spite of depositing a synthesized glass
on the outside thereof, the above described synthesized glass
rod with the cladding can be inserted in a suitable vycor
-glass or quartz glass tube, collapsed to form a rod and then
sub3ected to spinning, or the glass tube can be spun with
collapsing as it is. In a still further example ? a silica
glass doped with any one of B203, F, B203 F or P20s-F is
0 synthesized at a low temperature and deposited on the inside
M-CVD
of a quartz glass or vycor glass tube by the prior art/(Modi-
fied Chemical Vapor Deposition) method or P-CVD (Plasma-activated
-10-
1 16893~
l CVD) method using a hydride such as SiH4, an organic compo-
und such as Si(OC2H5)4 and/or other compounds such as Si~4,
~F3, B2~6 and PF3 as a gaseous raw material. A silica glass
rod synthesized at a low temperature and containing some OH
groups or OD groups is inserted in the inside of this tube
and subjected to melt spinning after collapsed tG be a rod
or with collapsing, thus obtaining a glass fiber of the pre-
sent invention. In this M-CVD method, a glass fiber can
further be prepared by synthesizing and depositing at a low
temperature a silica glass doped with B2O3 and/or F, synthe-
sizing and depositing at a low temperature using a hydride
such as SiH4 or an organic compound suCh as Si(OC2H5)4 as a
gaseous raw material and then subaecting the resulting com-
posite tube to melt spinning directly or after collapsed to
be a rod.
Fig. 5 shows a cross-sectional view of an optical
fiber consisting of core 51 of Sb2O3-SiO2 glass, cladding
52 of SiO2~ B23-si2' F-SiO2 or F-~2O3-SiO2 glass and
aacket 53 of a quartz or vycor glass. These glass fibers
are radiation resistant, but in order to prevent from dete-
rioration of the mechanical strength thereof, it is desira-
ble to provide the outside of glass fiber 61 as shown in
Fig. 6 with a primary coating 62 of a thermoplastic resin
such as polyimide resin, epoxy resin or silicone resin
(which should be coated directly after forming the glass
fiber) and further with a thermoplastic resin 63 such as
ethylene propylene rubber or bridged polyethylene by ext-
rusion.
The Sb2O3-SiO2 glass used herein is excellent in
30 radiation resistance as well known in the art and is ordi-
narily synthesized by ~-CVD method or by flame hydrolysis
as follows:
1 ~893~
1 SiC14 + 2 = Si2 + 2Cl
2SbC15 + 3/2O2 = Sb23 + 5Cl2
SiC14 + 2H2 + 2 = Si2 +
2SbC15 + 5~2 + 3/202 = Sb23 +
In M-CVD method, however, the oxidation decomposition of
chlorides is carried out at a high temperature and Cl remains
in a large amount, thus resulting in many oxygen defects and
increasing the loss in the presence of radiation. In the
method of flame hydrolysis, the reaction temperature is so
bigh due to use of chlorides that there remain a number of
structural defects such as oxygen defect and the transmission
loss increases in the presence of radiation.
~ he above described problem can be solved by selec-
ting, as a raw material, hydrides such that can be oxidized
at a lower temperature and have a high radiation resistance
as well as a relatively low vitrification temperature as the
oxides thereof, according to the present invention.
Up to the present time, the use of such hydrides
as a raw material has not taken into consideration since
they cause to increase the transmission loss in a longer
wavelength zone.
Methods of making really the above described optical
fiber will now be illustrated. In one example, H2 and/or D2
as a combustion gas and 2 as a combustion aid are fed to a
burner consisting of a quarts glass tube to form a flame,
into ~hich gaseous hydrides of SiH4 and SbH3 as raw material
gases are introduced by the aid of a suitable carrier gas to
effect a flame oxidation reaction to form a fine powder of
silica glass doped with Sb2O3 containing some OH groups
and/or OD groups, and the resulting powder is blown against
and deposited in the state of fused glass on a rotating
-12-
~L 16~938
l target by O-CVD method or VAD method. Depending on the
deposition method, any form of round rods or cylinders can
be obtained. In another example, a fine powder of the above
described Sb2O3-SiO2 glass can be prepared in the form of a
powder mass by O-CVD method or VAD method and sintered to
be a transparent glass. Then, the surface of this glass rod
is subjected to cylinder grinding or polishing and ~urther
to HF polishing, CO2 laser polishing or flame polishing to
obtain a cleaned and smooth glass rod. ~2 and/or D2 as a
combustion gas and 2 gas as a combustion aid are fed to a
burner consisting of a quart~ glass tube to form a flame,
into which a gaseous hydride of SiH4 as a raw material is
introduced by the aid of a suitable carrier gas to effect
a flame oxidation reaction and to form a fine powder of SiO2
containing some OH groups and/or OD groups, and the resul-
ting powder is blown against and deposited in the state of
fused glass on the above described glass rod.- This glass
rod is subjected to melt spinning in a furnace at a high
temperature and coated with a thermoplastic resin before
taking up the fiber on a reel, followed by baking7 to thus
obtain a glass fiber of the present invention. In a further
example, a gaseous raw material containing F or B and a
gaseous raw material containing Si such as SiCl4 with 2
are introduced into a plasma flame of high frequency plasma
torch by the aid of a suitable carrier gas and a silica
glass doped with F and/or B2O3 is deposited on the outer
surface of a rotating glass rod synthesized as described
above. During the same time, if necessary, a compound con-
taining H or D such as H2O or D2O can be added to synthesize
a glass containing OH groups or OD groups, from which a
glass fiber of the present invention can be obtained through
melt spinning. In this case, compounds such as SiH4, SiF4,
BF3 and the like are introduced into an oxyhydrogen flame
-13-
1 1~893~
.
1 made up of H2 and/or D2 and 2 to synthesize silica glass
fine particles and subse~uently a silica glass doped with
B2O3 and/or F is deposited in fused state. At this time, in
particular, glass fine particles are synthesized at a low
temperature, deposited as powder and subsequently sintered
in an atmosphere containing H2O or D2O, thus obtaining a
transparent glass. Subsequently, on the outer surface of
this synthesized glass rod is deposited a silica glass by
introducing a gaseous raw material containing Si such as
SiC14 with 2 by the aid of a carrier gas into a flame or
plasma flame. During the same time, if necessary, TiC14,
AlC13 or ZrC14 can be added to deposit a glass doped with
~iO2, A12O3 or ZrO2. Melt spinning of these glass rods
result in glass fibers of the present invention.
In spite of depositing a synthesized glass on the
outside thereof, the above described synthesized glass rod
with the cladding can be inserted in a suitable vycor glass
or quartz glass tube, collapsed to form a rod and then sub-
jected to spinning, or the glass tube can be spun with
collapsing as it is.
In a further example, a silica glass consisting of
pure SiO2 or doped with B2O3 and/or F is synthesized at a
low temperature and deposited on the inside of a quartz
glass or vycor glass tube by the prior art M-CVD method or
P-CVD method using a hydride such as SiH4, an organic com-
pound such as Si(OC2H5)49 SiF4 and/or BF3 as a gaseous raw
material. A silica glass rod synthesized at a low tempera-
ture and containing some OH groups and/or OD groups is inter-
ted in the inside of this tube and subjected to melt spinning
30 after collapsed to be a rod or with collapsing, thus obtain-
ing a glass fiber of the present invention.
Furthermore, a method by P-CVD or M-CVD is available. SiH4
-14-
1 16893~
l gas optionally diluted with N2 and an oxidation gas such as
C2 or 2 are fed in a quartz glass tube or vycor tube the
outside of which is heated, and SiO2 glass synthesized and
deposited on the inner wall of the tube. Then, if necessary,
SbH3 and SiE4 gas diluted with Ar and an oxidation gas such
as C02 or 2 are fed therein, an S~203 SiO2 glass is synthe-
siæed and deposited on the inner wall of the tube. ~here-
after, the tube is heated at a high temperature to laminate
the synthesized glass layer, collapsed to form a rod and
subjected to melt spinning to form a fiber. In some cases,
another fiber can be prepared by synthesizing and depositing
at a low temperature a silica glass doped with B203 and/or
F by M-CVD method, further synthesizing and depositing at a
low temperature a silica glass using SiH4 as a raw material
and then sub~ecting this composite tube to melt spinning
directly or after collapsed to a rod.
In the present invention, an SiO2 glas~ containing
0.001 to 1 % of Ce203 + CeO2 is used as a glass through which
light advances concentrically, since if the amount of Ce203
+ CeO2 is less than 0.001 %, the centers of Ce 4~ and Ce 3+
are so dilute that electrons or positive holes are trapped
by the structural defects to increase the transmission loss,
while if more than 1 %9 the loss increases due to ultraviolet
absorption by Ce3 and Ce4+. When using a wavelength of
10 ~m or more, however, the sum total can be allowed to at
most 2 % because the effect of ultraviolet absorption is
decreased.
5ince such a core glass has a refractive index
similar to, although somewhat higher than, that of quartz
glass, the cladding is to be of plastics such as silicone
resin and fluorine resin, or of a glass having a refractive
index lower than that of quartz glass, such as ~203-F-SiO2,
2 5 F Si2~ F-si2 or ~2o~-P2os-F-sio2 glass. In the latter
-15-
1 168938
l case, SiO2 or an SiO2 glass doped with TiO2, ZrO2, Al2O3 or
~f2 can further be provided on the outside thereof in order
to increase the water resisting property ~nd strength~
Onto the glass fiber is applied, as a primary coa-
ting, a thermosetting resin such as polyimide or epoxy
resins that are resistant to radiations directly after melt
spinning the preform. In the case of preparing a plastic
cladding fiber, of course, a silicone resin or fluorine
resin is coated and baked directl~ after spinning. Onto
this primary coating is further applied, as a secondary coa-
ting, a thermoplastic resin such as ethylene propylene rubber
or bridged polyethylene for the purpose of reinforcing.
When the transmission loss is increased after irradiation of
electron ray, the fiber can be subjected to a heat treatment
at a suitable temperature.
The present invention will now be illustrated by
the use of SiH4 as a starting material without limiting the
same~ Of course, other organic compounds such as Si(OC2H5)4
or dopants such as B ~ 6, P~I3, SbH3, etc. which do not so
increase the transmission loss under radiation can be used.
Referring to Fig. 7~ ~2 gas and 2 gas, as a com-
bustion gas, are fed to oxyhydrogen burner 71 to make flame
72, into which SiH4 gas diluted with, for example, He gas is
introduced via burner 71, and SiO2 glass fine particles are
obtained through the reaction of ~iH4 + 202 = SiO2 + 2H20.
During the same time, an aqueous solution of Ce compound is
spouted in the form of a spray 75 from exhaust nozzle 74 and
glass fine particles having Ce2O3 and CeQ2 in or on the glass
fine particles are deposited on target 77' to form a glass
soot or transparent glass body 77. If necessar~, carrier
gas 78 is fed to exhaust nozzle 74 and compressed gas 79 is
added to vessel 79' to forward the aqueous solution 79" via
-16-
Jl 168938
l pipe 79"' and to form a flow of the aqueous solution 75 with
the form of a spray. As the aqueous solution, there are pre-
ferably used aqueous solutions of cerium nitrate Ce(NO3)3 -
xH2O and cerium ammonium nitrate Ce(NO3)3 . NH4NO3 . ~H2O or
(NH4)3 Ce(NO3)6 zH2O. Of course, other Ce salts can also
be used. When the temperatures of target 77', the surface
of glass body 77 and glass fine particles73, 76 are sufficiently
high, a transparent glass body 77 is obtained, but when the
temperatures are low, glass body 77 is deposited as powder.
In the latter case, the powder can thereafter be sintered in
a furnace at a high temperature to give a transparent glass
bod~.
The above described embodiment is carried out by
VAD method, but is not always limited thereto. Modifications
of the embodiment shown in Fig. 7 are of course possible and
O-CVD method can also be adapted thereto.
The transparent glass rod obtained in this wa~ is
stretched to give a glass rod with a suitable diameter on
which a cladding glass of B2O3-SiO2, P2O5-F-SiO2, ~-SiO2
or B203-F-SiO2 is deposited by O-CVD method. If necessary,
for the protective purpose, SiO2 or ZrO2-, ~iO2-, Al2O3_or
HfO2-doped SiO2 can be deposited on the outside thereof b~
O-CVD method. In some cases, a cladding glass of B203-SiO2,
P2Os-F-SiO2,F_SiO2 or B2O3-~-SiO2 can be provided inside a
quartz tube, from which a preform can be obtained as
"rod-in-tube".
A glass fiber with a number of OH groups meets
with a great loss under radiation at wavelengths correspon-
ding to the vidration absorption of OH group or the vibra-
tion absorption of OH group and SiO4 , i.e. 2.7~U~n, 1.3JU~ ,
O.95 ~, etc., which has some influences on the other wave-
length rane. Even in the presence of O~ groups, however,
-17-
1 1 ~893~
l increase of the loss caused thereby is not so large at the
loss of light source wavelengths of ~ED (Light Emitting
Diode) or ~D (Laser Diode) in the range of ~ = 0.82-0.87 ~m.
In a glass with OD groups rather than OH groups, the wave-
lengths at which the absorption loss is great are shifted to
wavelength ~ times9 resulting in decreased effect. OD group
has the similar effect of promoting to diminish the defects
to OH group.
The content of OE groups and/or OD groups in the
glass fiber of the present invention will hereinafter be
illustrated. In the prior art optical transmission fiber,
the loss due to OH groups is 1.25 dB/km per 1 ppm wt of OH
groups at A = 0.945 ~m, i.e. 50 dB/km in the presence of
40 ppm of OH groups, and is increased by 2 to 20 d3/km in the
range of ~ = 0.80-0.90 ~m. ~hus, such a fiber i5 not con-
sidered to be used for optical communication systems. In the
presence of radiations such as X-rays and ~-rays, however,
there can be used a fiber whose transmission loss is high
but is not so increased in the presence of radiations, since
the distance of optical transmission is short, i.e. 100 m or
less. For example, an optical fiber consisting of a silica
core and a silicone resin clad, containing 40 ppm of OH groups,
meets with only a loss of 0.2 to 2 dB in 100 m. If less than
40 ppm, recovery of the loss due to structural defects is too
late to be put to practical use, while if more than 40 ppm,
the more, the better.
Methods of making a glass rod containing OH groups
and/or OD groups and a glass fiber will now be illustrated
without limiting the present invention. In particular, it
is important herein to prepare a silica glass containing
OH groups or OD groups. In one example, H2 and/or D2 as a
combustion gas and 2 gas as a combustion aid are fed to a
burner consisting of a quartz glass tube to form a flame,
-18-
: - 1 168~38
into which an organic compound such as Si(OC2H5)4 or a
hydride such as SiH4, as a raw material, is introduced by
the aid of a suitable carrier gas to effect a flame hydro-
-~ lysis or falme oxidation reaction and to form a fine powder of silica glass containing OH groups and/or OD groups, and
the resulting powder is blown against and deposited in the
state Or fused glass on a rotating target by O-CVD method
or VAD method. Depending upon the deposition method, any
form of round rods or cylinders can be obtained as well
known in tbe art. In another example, a gaseous Si-containing
compound and 2 gas are introduced into the above described
oxyhydrogen flame or plasma flame and a glass fine powder
mass is prepared by O-CVD method VAD method, which is then
sub~ected to sintering and clear vitrification in an atmos-
phere containing H2O and/or D2O, or H2 and/or D2, thus
,~
obtaining a high purity silica glass containing large amounts
of OH groups and/or OD group~. Then, the surface of this
., ~
glass rod is subaected to cylinder grinding or polishing
and further to HF polishing, C02 laser polishihg or flame
polishing to obtain a clean and smooth glass rod. ~his
glass rod is subJected to melt spinning in a furnace at a
high temperature and coated with a silicone resin or fluo-
rine resin before taking up the fiber on a reel, followed by
; baking, to thus obtain a glass fiber of the present inven-
- tion. In a further example, a gaseous raw material contai-
ning at least one of F and B and gaseous raw material con-
taining Si such as SiC14 with 2 are introduced into a plasma
flame of high freguency plasma torch by the aid of a suitable
carrier gas and a silica glass doped with F and/or B2O3 is
deposited on the outer surface of a rotating glass rod synthe-
sized as above. During the same time, if necessary, a com-
pound containing H or D such as H2O or D2O can be added to
-19-
1 ~893~
1 synthesize a glass containing OH groups or OD groups, from
which a glass fiber of the present invention can be obtained
through melt spinning. Subsequently, on the outer surface
of this synthesized glass rod is further deposited a silica
glass by introducing a gaseous raw material containing Si
such as SiC14 with 2 by the aid of a carrier gas into a
flame or plasma flame. During the same time, if necessary,
~iC14, AlC13 or ZrC14 can be added to deposit a glass doped
with TiO2, A12O3 or ZrO2. In spite of depositing a synthe-
sized glass rod on the outside thereof, the above describedsynthesized glass rod with the cladding can be inserted in
a suitable vycor glass or quartz glass tube, collapsed toa-rod and
then subjected to spinning, or the glass tube can be spun
with collapsing as it is. In a still further example, a
silica glass doped with B2O3 and/or F is deposited on the
inside of a quartz glass or vycor glass tube by the prior
art M-CVD method or P-CVD method. A silica glass rod con-
taining OH groups and/or OD groups1 as described above, is
inserted in the inside of this tube and subjected to melt
spinning after or during collapsing. If a compound of H
or D is added to the gaseous raw material when this silica
glass doped with ~23 and/or F is deposited, a clad glass
containing a number of OH groups or OD groups can be prepared.
In some cases, a silica glass core containing a number of
OH groups or OD groups can simultaneously be prepared by
M-CVD method.
According to the present invention, there is provi-
ded an optical transmission glass fiber whose increase of the
loss is small even in the presence of radiations. ~hat is
to say, the use of fibers consisting of a silica glass synthe-
sized at a low temperature and containing some OH groups or
OD groups, a silica glass synthesized at a low temperature
and containing some OH groups or OD groups in addition to
--~0--
`-` 116893~
l Sb2O3 or a silica glass containing a number of OH groups
or OD groups according to the present invention makes possi-
ble optical communications, illuminations and image trans-
missions in high radiation ranges, because increases of the
transmission loss is thereby suppressed in the presence of
radiations such as X-rays and ~-rays.
~ he follosing examples are given in order to illu-
strate the present invention in more detail without limiting
the same.
Example
Various glass fibers were prepared by the conditions
as shown in Table 1 and subjected to examination of the change
of the transmission loss under irradiation of ~-rays.
Table
Sample Core
No. Material Making Method
1CeO2-P2O5_SiOM-CVD, high temperature
2 SiO2P-CVD, high temperature
3 P205-SiO2P-CVD, lower than Sample No. 2
A SiO2Flame Oxidation (SiH~ SiO2)
B SiO2Plasma Synthesis (SiCl4~SiO2)
C SiO2 Bernoulli Method
Cladding Jacket
P2o5-B2o3-sio2M-CVD, high temperature Quartz Glass
F-doped SiO2P-CVD, high temperature Quartz Glass
F-doped SiO2 P-CVD, hiæh temperature Quartz Glass
Silicone Resin Coating and Baking
Silicone Resin Coating and Baking
Silicone Resin Coating a~d Baking
-21-
1 168938
l These glass fibers were reinforced by a primary coating of
silicone resin and a secondary coating of polyethylene or
nylon, wound round an aluminum reel of 280 mm in diameter
with a length of 5 to 30 m and subjected to irradiation of
~-rays at a dose rate of 1.2 x 106 R/H from 60Co placed at
the center thereof. Change of the transmission loss during
irradiation is examined by monitoring the intensity of the
transmission light of IED ( ~ = 0.83JUm) and change of the
transmission loss after irradiation is examined in the range
of 0.8 to 1.6J~m.
When the various fibers were subjected to irradi-
ation of ~-rays, the output of the transmission light inten-
sity of ~ED was varied as shown in Fig. 3-(a) and Fig. 4-(a).
~ig. 3 (a) is a graph showing the relationship between the
increased quantity of transmission loss and the ~-rays
irradiation time when the cladding is of a plastics, in
which Curve A shows that of an optical fiber according to
the present invention consisting of a core glass of SiO2
synthesized at a low temperature from SiH4 while Curves B
and C show respectively that of the prior art optical fibers,
the former consisting of a core glass of SiO2 synthesized
by the plasma synthesis of SiGl4 and the latter consis-tng
of a core glass of SiO2 obtained by heating and melting natural
quartz crystal at a high temperature by the Bernoulli method
(H2 + 2 flame). In the case of C, the transmission loss is
larger because of the higher synthesis temperature and larger
amounts of impurities. In comparison of the cases A and B,
on the other hand, there is a large difference in the quantity
of loss in spite of that there is not such a large difference
in purity between them. This is possible due to the diffe-
rence of synthetic temperatures of glass. That is, in the
fiber A of the present invention, the glass is synthesized
1 168938
l at a relativel~ low temperature because of using ~iH4 as a
raw material, thus resulting in decreased structural defects
as well as high radiation resistance. ~his tendenc~ can also
be seen in a case where the cladding and jacket consist of
glass, as shown in Fig. 4 (a). ~he optical fiber of Sample
No. 3 acccrding to the present invention, containing additio-
nally P205, can be synthesized at a lower temperature than
the optical fiber of Sample No. 2, containing SiO2 only.
Therefore, even if core glasses are prepared by the same
P-CVD method, there are few str~ctural defects resulting in
decrease of the transmission loss in a case where the core
glass is synthesized at a lower temperature. In addition,
even in the case of doping P205, increase of the transmission
loss cannot be so suppressed as Sample No. 3 of the present
invention according to circumstances, i.e. when the core
glass is synthesized by M-CVD method with codoping GeO2.
When the fiber of Sample No. A is subjected to
intermittent irradiation of r -rays, the increased quantity
of transmission loss is changed as shown in Figo 3 (b) in
which the hatched portions under the axis of abscissa mean
irradiation time (hour).
Moreover, the similar data were measured as to the
following samples to obtain results shown in Fig. 4 (b).
Sample No. 4 GeO2-SiO2 core/SiO2 clad fiber
No. 5 Ge02-B203-siO2 cre/B23-si2
clad fiber
No. 6 Ge02-P2os-sio2 Cre/P205 Si2
clad fiber
No. 7 Geo2-p2o5-B2o~-sio2 core/B2o~-p2o5-sio2
clad fiber
No. 8 P205-SiO2 core/F-SiO2 clad fiber
No. 9 SiO2 core/F-SiO2 clad fiber
(Core was s~nthesized by plasma oxidation
and decomposition of SiCl4)
No.10 Cs20-B203-SiO2 cre/B23-si2
clad fiber
-2~-
1 ~893~
l In this figure, T on the axis of abscissa means "20 minutespast after removal of 60Co".
Example 2
A guartz tube of 8 mm~ x 10 mm~ was placed in an electric
furnace moved reciprocatedly at a rate of 50 cm/hr and
heated at 1400 C~ Into this tube were flowed 5 % Si~4 - 95
N2 gas at a rate of 100 cm3/min and 40 % 2 - 60 % ~e gas
at a rate of 2000 cm3/min for 10 hours to synthesize and
deposit an SiO2 glass on the inner wall thereof. ~hen, 5 %
SbH3 - 95 % N2 gas at a rate of 50 cm3/min, 5 % SiH4 - 95
N2 at a rate of 100 cm3/min and 40 % 2 ~ 60 ~ He gas at a
rate of 3000 cm3/min were flowed therein for 5 hours to syn-
thesize and deposit an Sb203-SiO2 glass on the deposited
inner wall. The thus resulting tube was subjected to glass
lathe , heated at 1800 C in an ~2/2 flame and collapsed
to give a glass rod (D) with an outer diametex of 8 mm~, a
clad diameter of 5 mm~ and a core diameter of 3 mm~.
In the similar manner, another glass rod (E) having
an outer diameter of 8 mm~, a clad diameter of 5 mm~ and a
core diameter of 3 mm~ was prepared using a quartz tube of
the same dimension, i.e. 8 mm~ x 10 mm~ and using SiC14 and
2 as a raw material for cladding and SbC15,SiCl4 and 2 as
a raw material for core which were subjected to M-CVD method.
These glass rods were charged in an electric furnace,
heated at 1800 C to form a fiber of 150 ~m~ and then coated
with a primary coating of epoxy resin and further with a
secondary coating of ethylene propylene rubber thus obtaining
optical fibers. When the thus obtained optical fibers were
subjected to irradiation of ~-rays at a rate of 1 x 106 R/h
for 5 hours, the transmission losses measured were increased
by 150 dB/Km in the case of Fiber D and by 1500 dB/Km in the
case of Fiber E
-24-
1 l6ss3a
1 Example 3
~sing a system as shown in Fig. 7, 10 wt ~ aqueous
solution of Ce(N03)~ was fed at a rate of 3 x 10 5 mol/min
as Ce(N03)3 to form a spray-like aqueous solution 75 while
H2 at a rate of 2000 ml/min, 2 at a rate of 4QOO ml/min
and SiH4 at a rate of 112 ml/min were simultaneously
fed to burner 71, thus obtaining a glass rod 77 with a diame-
ter of 15 mm~. This glass rod was stretched to a diameter
of 10 mm~, inserted into a quartz pipe of 12 mm~ x 14 mm~
on the inner wall of which B203-F-SiO2 glass had been pre-
viously deposited by M-CVD method to give a thickness of
1 mm~, and collapsed to form a preform of 14 mm~ in diameter.
The thus resulting preform was charged in a resistance fur-
nace of carbon, melt spun in a fiber of 140 ~m~ and coated
with an epoxy resin. When this fiber was subjected to irra-
diation of ~-rays at a dose rate of 1 x 106 R/h for 1 hour,
increase of the transmission loss was small, i.e. 50 dB/km
at ~ m.
Example 4
SiH4 gas with a carrier gas of D2 were introduced
into an oxyhydrogen flame by a quartz tube burner, subjected
to flame oxidation to form glass fine particles and deposited
or accumulated in fused state by VAD method to form a glass
r d of 12 mm~ x 200 mml containing 900 ppm of OH groups
and 100 ppm of OD groups. ~his glass rod was then subjected
to grinding and polishing to a diameter of 10 mm~.
The thus resulting glass rod and another glass rod
containing less than 10 ppm of OH groups, synthesized by high
frequency plasma flame, were melt spun to form glass fibers
of 150 ~m~ and immediately coated two times with a silicone
resin to give a thickness of 50 ~m + 50 ~m. ~hese fibers
with a length of 100 m was subjected to irradiation of X-rays
-25-
1 16893~
1 of 2000 R. ~he fiber of the present invention showed no
increase of loss while the comparative fiber containing less
than 10 ppm of OH groups showed a considerable increase of
loss.
On the other hand, in a Ge-doped fiber prepared by
the prior art M-CVD method, the increase of loss was too
large to allow light to be passed therethrough.
-26-
