JPS59156931A - Manufacture of glass optical fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to processes employed in the manufacture of glass optical fibers.

(Prior Art) In the production of optical fibers, glass preforms are glass tubes that are selectively doped with impurities, and are manufactured by MCVD (Modified Chemical Vapor Deposition) or MC performed by plasma.
VD, or Journal of the Electrochemical Society published in 1976 (Jo
Urnal of the Electrochemi
Cal Society, No. 423, page 1079, by a process such as PCVD, as described by D. Kuppers. The preform is collapsed or sealed at one end into the interior of the solid substrate, and the optical fiber is pulled from the solid substrate simultaneously with or subsequent to the collapse. The OH components trapped within the preform, and the resulting fiber, are absorbed in the wavelength range typically employed in optical communication systems, effectively increasing signal loss in such systems. I'm letting you do it. Thus,
During the formation of the preform, the OH content, e.g. Si
Care is taken to ensure that virtually no OH is mixed into the preform. Generally, the primary source of OH components will be those containing hydrogen-containing components that are typically converted to water at the tube collapse temperature. The water repeatedly reacts with the preform to produce bound OH components. In order to preserve the quality of the fiber thus ultimately produced, virtual measurements are taken while crushing the preform to remove hydrogen-containing components.

One major method is to use O during crushing the preform.
This is adopted to prevent the H component from being mixed in. 1981
Proceedings of the 3rd International Conference on Integrated Optics and Fiber Optic Communications held in San Francisco, California, April 27-29, 2008, W.N. 4, 86-. Published by the Institute of Electrical and Electronics Engineers, New York, on page 88,
Presented at the above conference by K. El Warka et al.
In a process described in the paper entitled "Reducing Hydroxyl Contamination in Optical Fiber Preforms," molecular chlorine is introduced during the tube crushing process. (K.
L. Walker, et al. ,”Reduct
ionof Hydroxyl Contaminants
ion In Optical Fiber Prefo
rms, ”Third International
alConference On Integrate
dOptics and Optical Fiber
Communications, San Fran
-cisco, california, apri
l 2 7-29, 1 98 ].

(New York: IEEE, 1981)
WA4. 86-88 (1981)) Chlorine generally reacts with water, for example water formed from hydrogen-containing components, producing hydrogen chloride through the reaction.

H2O + (J!24; 2H(y!+ MO2(+
) The HCl obtained is not mixed inside the preform,
removed in the effluent. In the process of crushing this molecular chlorine tube, there is a relatively low loss (1,
At the OH absorption peak wavelength of 39 μm, typically 03-2
It has been found that fibers with losses in the range of dB/Km) can be produced. However, it is certainly advantageous to effectively reduce the losses further to a desired level, even though the losses are already at an acceptable level.

SUMMARY OF THE INVENTION Carbon tetrahalide compounds, such as carbon tetrachloride, are modified for use in glass substrate environments, such as crushed preform environments, for ultimate use in manufacturing glass optical fibers. By introducing the OH component, the losses produced by the contamination of the OH component are substantially less than with other techniques. In particular, at 139 μm, 0.05
OH absorption losses as low as dB/Kin have been achieved. Thus, with the use of the present invention it is possible to greatly improve the quality of the ultimately produced fiber compared to that obtained using gases such as polymolecular chlorine.

DETAILED DESCRIPTION Compounds based on carbon tetrahalides, such as carbon tetrachloride, CBr C13, CBr2α2. Alternatively, if a mixture of these compounds is introduced into the physically or chemically altered environment of the glass substrate, the losses generated by the OH component in the optical fiber are significantly reduced.

In particular, the addition of carbon tetrahalides according to the present invention is useful for reducing OH contamination during various process steps involving glass substrate changes, e.g. Useful for shape changes as well as chemical feminization such as during the preform manufacturing process. In either case, the presence of the carbon tetrahalide during the transformation of the glass substrate results in very low loss levels in the fiber ultimately produced from this substrate. Although the technique according to the present invention is generally applicable to processes that involve the formation of glass substrates in the process leading to fiber manufacturing, it is important to note that the preform The process of crushing is adopted. However, the same parameters can be applied to other glass substrate forming processes.

The desired composition of carbon tetrahalide is a glass substrate environment,
That is, during the period of crushing the tube, the internal void 1 of the preform tube
It has been introduced in o.

(In the process of collapsing the photon tube, the internal gap is advantageously chosen because the internal glass region forms the waveguide region 2 and is the most stringent for limiting the OH content.) Most preferably, carbon tetrachloride (generally, but not necessarily, used with a carrier gas) is used as a carbon tetrahalide-based compound. Hopeful v! ] The tetrahalogenated carbon compound haflform can be prepared by conventional methods such as passing a carrier gas through a bubbler containing the halocarbon compound and flowing the carrier gas along with the tetrahalogenated carbon compound into the preform environment. Easily introduced into the environment.

(c7., CBr (i3. and/or C
If a combination of Br2C1!2 is desired, a mixture is produced by combining the waste streams of the individual bubblers or by using bubblers containing all of the compositions. In the former case, the molar proportion of each introduced composition is
It depends on each waste flow rate through each bubbler and on the bubbler temperature.

In the latter case, the molar proportions of each material in the gas phase depend on the corresponding molar proportions in the bubbler and the bubbler temperature, but are not equivalent. At either location, control samples are easily employed to determine the appropriate conditions to obtain the desired ratio in the final waste stream. ) CBrα3 and CBr2Q! Although it is not impossible to use z individually or in combination, at least those carbon tetrahalides can be combined with CQ! 4 is more desirable.

A possible explanation for this result is that T4Br (the product of the reaction of a bromine-containing compound with water) is less stable than H(y!).
Because of the relative instability of , it is necessary to use a somewhat higher concentration of halogen contributing to the sample in order to achieve equiconstrained results.

The concentration of the carbon tetrahalide compound employed to collect hydrogen-containing components during the preform crushing process has an impact on other processes used during the preform crushing process. For example, it is always desirable to introduce additive compensators such as germanium tetrachloride along with oxygen into the preform environment during tube collapse. The oxygen reacts with Geα4 to maintain the desired Geo2 concentration on the inner surface of the preform. When this process is adopted, the halogen liberated from germanium tetrahalide and carbon tetrahalide influences the concentration of GeO2 through the chemical equilibrium of the action expressed by the following equation.

Ge X4 + 02”: Ge 02 + 2
2 (2) Here, X is halogen. Therefore, if the additive concentration should be used in relation to the carbon tetrahalide, the resulting shift in equilibrium should be overcome by an increase corresponding to the amount of germanium tetrahalide compound employed. Must.

Similarly, the process of producing de facto halogen 1 from sources other than carbon tetrahalide and oxygen 2 in the preform environment has a substantial effect on the equilibrium shown in equation (1), This then affects the amount of carbon tetrahalide to remove the desired amount of water. For example, if oxygen is introduced as a carrier gas, the equilibrium of equation (1) shifts to the left. Thus, the minimum amount of carbon tetrahalide (for a given amount of halogen content) required to avoid the effective presence of OH in the fiber decreases as the amount of oxygen present increases. increases. (In contrast, scum such as helium or other inert gases has little effect.) If halogens from sources other than carbon tetrahalides are also present, There is almost no need for carbon dioxide. Although temperature often influences equilibrium considerations, the temperature employed during preform crushing, for example 2000-2200°C, has virtually no effect on the amount of carbon tetrahalide at the desired level. and thus has virtually no effect on the level of OH absorption in fibers formed from preforms produced using carbon tetrahalides.

In general, the process according to the invention is not intended to significantly remove hydrogen-containing components. Other considerations, such as high purity of reactive materials, are considered to virtually limit the level of hydrogen-containing components. For this reason,
Even in the presence of oxygen, sufficient carbon tetrachloride is readily introduced to prevent losses associated with hydrogen-containing component levels that are present even after these precautions. (Typically, there is between 1 and ] Oppm by weight of contaminated hydrogen, albeit bound.) Nevertheless, as discussed above,
Oxygen influences the minimum amount of carbon tetrachloride required in the hydrogen-containing component of the recovered level. During the tube collapse period, oxygen is generally at a level below 0.1 atmospheres, even if it is not purposefully introduced. For such oxygen levels, 0.
Desired results are obtained for typical hydrogen content levels when carbon tetrachloride partial pressures of 0.15 atm or higher are introduced into the glass substrate environment. When oxygen is purposefully introduced so that the oxygen level exceeds 0.1 atm, it is typically It's promising. (Po2
and Pcc14 are the partial pressure of 02 and the introduced Cα4, respectively. ) less than ippm,
If lower than normal levels of hydrogen components are present or can be tolerated without virtually all removal, a correspondingly small amount of carbon tetrahalide, i.e. Po2%/pc
c14 will be adopted. (In processes other than crushing preforms by MCVD, it is possible to have a backpressure of oxygen below 0.1 atm. In such cases, a correspondingly small amount of carbon tetrahalide may be introduced. A control sample is used to determine the amount of carbon tetrahalide required to produce the desired OH attenuation.

The presence of an oxygen source, as well as a halogen source other than carbon tetrahalide, are the main effects introduced by processes not directly related to the process of the present invention. However, the present invention does not affect the reaction equilibrium between water, the compound obtained from the hydrogen-containing component, and the tetrahalogenated carbon component, thus requiring adjustment to the parameters employed in the present invention. It is possible to introduce other materials for use in other processes. Control samples are easily employed to determine the appropriate calibration for each particular location.

Notwithstanding the above considerations, certain precautions must be taken. When using Cα4, it is generally desirable to limit the chlorine concentration, expressed as molecular chlorine, in the preform environment below 0.3 atmospheres.

Above these levels, high concentrations of chlorine tend to form bubbles in the preform, leading to unacceptably high losses.

Furthermore, oxygen in the presence of carbon tetrahalides has a tendency to avoid carbon deposition, and carbon dioxide, -carbon oxide,
Conditions in which this occurs also result in the formation of gases such as phosgene.

The carbon tetrahalide material should not contain excess hydrogen-containing impurities greater than 40 ppm, for example expressed as a weight percentage of H. Thus, 40 ppm
The composition of carbon tetrahalides with hydrogen levels greater than It is preferable to High purity containing less than 6 ppm is preferred. (If necessary to obtain the desired purity level, photochlorination of CBrα3 as well as CBr2C/!2 may be extended to remove some α
It can be converted to . However, the resulting 4) decagenide carbon is acceptable for use in the process of the present invention, as described above. ) The following example illustrates the invention graphically.

(Example 1) MCV published by Niss R. Nagel et al. in 1982, Institute of Electrical and Electronics Engineers, Journal of Quantum Engineering, Volume QE-1, Volume 8, No. 4, Pages 459-476.
A preform produced by the D process was employed.

(S, R, Nage 1 et al, IEEEJ
internal of Quantum Electro
nics.

QE-18(4), 459-4.76 (1982)
) These preforms were first sealed at one end and 2000
The tube was crushed by repeated longitudinal movements with a torch 20 while maintaining the temperature between -2200<0>C. 9 carbon tetrachloride held at 40°C with oxygen at a sludge flow rate of 330 parts per minute before sealing one end of the preform! <Put your bra on
I passed it. Cα4 including the waste flow is 1/min of the second
Combined with an oxygen flow of 000 CC. The combined gas stream was introduced 7 into one end of preform 25 and held for a sufficient time to purge the tube. The end of the preform opposite the point of waste introduction was then sealed. The gas flow during the containment period was gradually reduced to prevent pressure from building up in the preform. This gradual reduction resulted in an oxygen flow rate through the bubbler of 25 CC per minute and a second oxygen flow rate of 75 CC per minute. The torch was moved across the length of the preform at a speed varying from 6 to 10 cm per minute. During each pass, the pressure in the tube was controlled by controlling the escape port 15 of the gas being introduced from the preform or by controlling the rate of introduction of the combined gas stream. The pressure through these methods was controlled to avoid too rapid collapse of the tube and to allow collapse of the entire tube to occur after 5 to 7 passes. Next, in 1980, Elle
The fibers were drawn from the preforms using standard techniques such as those published by El. (L, L.

Blyler Jr., et al., Pro
ceedings of IEEE.

68.11.94-1198 (1980)). The measurements were made according to the process described in Chapter 11 of . (S, E, Mj
1ler et al., 0pticalFib
er Telecommunications, Ch.
apter 11.

Academic Press (1979)) The obtained fiber has a thickness of 0.05 to 0.1 at 13 μm.
．． It shows the OH absorption loss in dB/Km.

Example 2 The same process as described in Example 1 was followed, except that the preform was not initially sealed. Example 1
The initial flow rate of oxygen through the bubbler is 330 c/min and the second oxygen flow rate is 1000 c/min, as described in
It was c. The flow rate ratio between the oxygen loaded on carbon tetrachloride and the oxygen liberated from carbon tetrachloride was kept unchanged. However, the total combined flow rate was reduced to such a rate that collapse of the entire tube could occur in 7 passes.

The resulting fiber was 0.0 at 1.39 tLm.
It showed an OH absorption loss of 5 to 0.1 dB/KIn.

Example 3 The process of Example 2 was followed, except that germanium tetrachloride was simultaneously introduced into the preform environment. Keeping the germanium tetrachloride bubbler at a temperature of 40°C, 15c/min
This introduction was carried out by flowing oxygen at a rate of c.

The flow rate through the germanium tetrachloride bubbler remained virtually unchanged throughout the entire tube collapse process. The obtained fiber has a diameter of X 0.1 d at 1.39 μm
It had a measured value of OH absorption loss of B/Km.

[Brief explanation of the drawing]

The figure is a diagram showing an embodiment of the present invention. [Explanation of symbols of main parts] Glass substrate...25゜Continued from page 1 0 Inventor Suzanne Rose Nagel 555 Mount Kemple Avenue, Morristown, New Jersey 07960

Claims (1)

[Claims] 1. A method for manufacturing a glass optical fiber from a glass substrate, comprising the step of providing the environment of the glass substrate with scum selected to limit the amount of OH present in the glass substrate. A method for manufacturing a glass optical fiber from a glass substrate, comprising: heating the glass substrate to a high temperature; and changing the glass substrate by the heating, wherein the scum is A method for producing a glass optical fiber characterized by containing carbon tetrahalide. 2. The method according to claim 1, wherein the carbon tetrahalide is carbon tetrachloride, Cα2Br2. and Cα3Br. 3. The method according to claim 1 or 2, wherein the liquid comprises carbon tetrachloride, Cα2 Br2 and Cα3
A method for manufacturing a glass optical fiber, characterized in that it contains at least one of Br. 4. A method for manufacturing a glass optical fiber according to claim 1, 2, or 3, characterized in that the carrier gas contains oxygen. 5. The method of manufacturing a glass optical fiber according to any one of claims 1 to 4, wherein the waste contains GeC&. 6. The method according to any one of claims 1 to 5, characterized in that the gas is supplied to the gap in the glass substrate by bubbling a carrier gas through the liquid. Method of manufacturing glass optical fiber. 7. A method for manufacturing a glass optical fiber according to any one of claims 1 to 6, wherein the changing step includes a step of crushing a glass preform. 8. A method for manufacturing a glass optical fiber according to any one of claims 1 to 7, comprising the step of pulling out the fiber from the crushed glass substrate. 9. A method for manufacturing a glass optical fiber according to any one of claims 1 to 8, wherein the high temperature is in a range of 2000°C to 2200°C.