JPS60103049A - Structure of optical glass - 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 optical glass structures, and more particularly to optical waveguides.

Light waveguides are used to transmit electromagnetic energy (i.e., in the form of light) at wavelengths in or near the visible spectrum and include an inner core of transparent material and a surrounding core. The cladding has a refractive index and serves to prevent light from escaping from the core. It is important to minimize damping in the core, and a wide variety of core and cladding materials have been proposed for this purpose.

As used herein, optical glass structures refer to cladding rods for optical fibers and optical fibers, as described below. This preform rod is a relatively thick piece made by crushing a tube manufactured according to the method described below, and K, the manufacturer of the light waveguide, stretches this rod many times to reduce its diameter. It is necessary.

The light waveguide of the present invention is an optical glass structure having a glass core formed from phosphorous pentoxide and silica and optionally additional components, and a glass cladding having a lower refractive index than the core. And it appears that the reduction in refractive index relative to the core of the cladding is obtained, at least in part, by the concentration of phosphorus pentoxide in the cladding being zero or less than the concentration in the core. This is a structure of the optical glass. Part of this index reduction may also be achieved by reducing the concentration of any additional components that may be present in the core.

Preferably, the core is a phosphosilicate glass formed from phosphorus pentoxide and silica.

This cladding can consist of pure silica, high silica content glass or silica containing a lower proportion of phosphorus pentoxide (than the phosphorus pentoxide content in the core).

As an alternative to using pure silica as a cladding or a phosphorus silicate glass having a lower concentration of phosphorus pentoxide than the core, a borosilicate glass can be used.

The gradual change in refractive index from the core to the cluttering is
This can be achieved by providing stepwise changes in the concentration of phosphorus pentoxide.

In addition to the phosphorus pentoxide and silica contained in the core, additional components can be added, such as dalmania, or a trivalent oxide selected from the oxides of boron, aluminum and antimony.

The method of fabricating the light waveguide of the present invention is as follows: 1. Passing a mixture of oxygen and vapors of a suitable silicon compound and optionally a suitable phosphorus compound into a tube; heating the tube to oxidize the compound l; and repeating these steps using a mixture of oxygen and vapors of said compounds of both silicon and phosphorous, such that the proportion of said phosphorus compounds is equal to that in the first step. This also includes high-level processes.

In order to reduce the impact of impurities in the glass, the starting materials are preferably liquid and easily purified, for example by distillation. Suitable compounds are silicon tetrachloride and phosphorus trichloride or phosphorus oxychloride.

Oxygen is bubbled through this yuzu liquid and the oxygen streams carrying silicon tetrachloride vapor and phosphorus oxychloride vapor are mixed in a ratio that provides the desired relative concentrations of phosphorus pentoxide and silica in the glass. Add 5 more oxygen to. The mixed vapor is then oxidized at a suitably elevated temperature and simultaneously deposited as a fused M layer of phosphosilicate glass on the inner surface of the silica tube. This internally coated tube is then crushed to form a rod, and the rod is stretched to form a fiber.

In order that the invention may be more fully understood, reference will now be made to the accompanying drawings.

FIG. 1 shows the apparatus used to fabricate the light waveguide of the invention.

Figure 1 shows a light waveguide of the invention.

Referring to FIG. 1, an apparatus is shown for depositing vapor of a suitable feed chemical into a silica tube. - The starting material for this deposition process is a volatile compound containing the required components. Conveniently phosphorus oxychloride and silicon tetrachloride are used, which are contained in containers 1 and 2. If borosilicate glass is to be combined as a cladding, a similar additional container containing boron trichloride is provided. The phosphorus oxychloride in the phosphorus oxychloride container can be distilled to partially improve its purity. Oxygen from source 3 passes through each line 4.5 and 6 at a rate controlled by flow meters 7.8 and 9 installed in these lines. The oxygen passing through vessels l and 2 carries vapors of phosphorous oxychloride and silicon tetrachloride, respectively, and these two vapor streams are mixed and diluted with additional oxygen from line 6 if necessary, and the glass It passes through the deposition tube 10.

The short furnace 11 is moved relative to the tube 10 to oxidize the chloride and produce the appropriate oxide. Alternatively, the furnace 11 may be fixed and the silica tube 10 moved across the furnace.

The oxidation reaction of silicon and phosphorus chlorides is approximately 13
It occurs spontaneously in the gas phase at a relatively low temperature of θOOC, producing a dense mist of fine glass particles. Note that if enough phosphorus pentoxide (or other suitable ingredient) is added to substantially reduce the viscosity of the glass, the glass particles will adhere to the walls of the container and form a clear, uniform, and homogeneous phosphorous silica. Form a layer of cade glass. In this way, high deposition rates can be obtained as there is no need for gas diluents to slow down the reaction, and the deposition of glass occurs directly on the walls of the silica tube, and due to the relatively low temperature, deformation occurs. There is no problem.

Typical operating conditions are as follows. The flow rates of heavy oxygen and silicon tetrachloride vapor in a 10 tun pore silica tube were maintained at 6 o θ and 33 ml 1 min, respectively, while the phosphorus oxychloride flow rate was varied in the range Vi/−/3 ml 1 min. /2 left. .

A layer of phosphoosilicate glass was deposited on the inner surface of the tube as it passed through the furnace, at a furnace temperature of between -/tat θ0C.

The tube 10 was passed through the furnace 11 a number of times, each time a layer of glass was deposited on the inside surface of the tube 1o. The proportions of each component were varied after the appropriate layers were deposited to produce the glass needed for the shaving and core. To create a light waveguide with graded refractive index, the proportions of each component are gradually varied between the appropriate layers.

The deposition time for each layer is approximately 3 minutes for a typical 50 cm length of tube, and the phosphorus pentoxide strength is approximately 400 kg.
θ weight@%, which varies depending on the flow rate of phosphorus oxychloride. For a flow t'' as described above; The refractive index can be precisely adjusted, and a cross section that varies over a wide range can be created with a refractive index that is stepped from a uniform one.

? To form a tarading of rosilicate glass, an apparatus similar to that shown in FIG. 1 is used, but with an additional source of boron trichloride gas. The flow rates of boron trichloride and silicon tetrachloride are typically g and 35 ml/min, respectively, and 4t5θml 7
of oxygen is used with this. The first three layers are of constant composition, while the next three layers are formed by decreasing the flow rate of boron trichloride stepwise to zero. The amount of phosphorus oxychloride is gradually increased from zero to 9-7 minutes over the next lt layer, forming 2ON in total. The stacked deposited layers of phosphosilicate glass in each layer of the first tube formed in this way are clearly different, but the subsequent 8 degrees of collapsing and drawing of the tube into fibres. Diffusion occurs and the 9 degree slope becomes smooth. Fibers with a graded refractive index core during the borosilicate polymerization are thus fabricated.

Collapsing of the layered support tube 10 into a rod can be carried out by rotating and carefully heating the tube 1o in a hydrogen oxide flame.

An oxyhydrogen flame is moved along the length of the tube and heated to a high enough temperature to cause the tube to bulge.

When crushing the tube, it is important to maintain the circularity of its cross section. This is because, if the circle is distorted to some extent, it will eventually be stretched and a circle of fc, 7 eyes will be planted, which will have an adverse effect on the optical energy transfer characteristics. To maintain a circle when collapsing the tube, keep a slight excess of pressure in the tube. The magnitude of this 1E force, iqt, is a function of the diameter of the central hole. In addition, after this central hole is closed, the circular shape is Mf.
In a crushed tube to hold it? 1) Heat 'I'
Pass through the cooling zone immediately after j and 7.

The tube can be conveniently pressurized by venting the gas through a restricted orifice into the air. This gas stream can consist of the initial reactants, silicon tetrachloride and phosphorous oxychloride vapor, and oxygen. A stream with a high content of phosphorus oxychloride prevents the loss of the more volatile phosphorus pentoxide. Connect one end of the tube to the inlet side of the orifice and seal the other end. This method has the advantage that the internal pressure does not change by A'=1 even when the gas in the tube is heated and expanded. The heating zone described in MiJ is moved along the tube from the sealed end at a suitable speed. The cooling zone consists of a row of nozzles located immediately after the gas burner and is supplied with pressurized air which is used as an air blast to blow onto the heated collapsed tube. By using air blast, the tube runout can be adjusted to some extent.
This air blast can be conveniently adjusted so that the point of collapse is very close to the quenching air blast area. By this means, internal pressurization can be carried out until the last possible moment, at which point the central hole is closed. The glass is immediately quenched until it has a completely circular shape. The heating and cooling zones may be moved several times along the tube to cause it to collapse in stages.

Another way to collapse the tube is to pass it through a heated die. The dimensions of the die are such that either the tube hole is completely closed to form a rod, or a small hole is left in the center of the tube. This hole is removed during the fiber stretching operation. One way to crush the tube is to pass a high temperature along the tube,
The tube is rotated and a graphite tool is placed against the side of the tube and the tool is moved slowly along the tube after the heat is applied.

Once the rod is formed from the collapsed tube, it is then fi/wire drawn in a fiber drawing machine.

A rod of corresponding length obtained from a tube 10 of length Sθ can be drawn to a length of 8.2' Km.

The addition of phosphorus pentoxide to silica has a significant effect on some of the physical properties of the resulting phosphosilicate glasses, so a concentration as high as possible is desirable to obtain the desired optical properties; There is a limit to the Nt of phosphorus pentoxide that can be denominated in gold. One physical property that is affected is the coefficient of expansion. Since the coefficient of expansion of pure silica is much lower than that of phosphorus pentoxide, a higher density of phosphorus pentoxide in the phosphosilicate glass results in a corresponding increase in the coefficient of expansion, leading to the cluttering of the silica. and the 7-osulfocrylate core increases. In conjunction with the somewhat lower strength of phosphosilicate glasses, if the proportion of phosphorus pentoxide is too high, spontaneous fracture of the core can occur. Other physical properties that are affected are viscosity and volatility, which present fabrication problems for light waveguides.

To improve the physical fit between the core and the clutsding, Germania, ′! An additional component consisting of a trivalent oxide selected from one or more of the oxides of , bamboo boron, aluminum, antimony, arsenic and bismuth can be added.

This additional component adds vapors of volatile compounds of the selected elements to a gaseous stream carrying vapors of appropriate volatile compounds of silicon and phosphorus, and transfers the vapors inside the silica tube as described above. By submerging it onto the surface,
It can be integrated into the glass core.

Alternatively, a layer of two-component phosphoosilicate glass is formed on the inner surface of the hollow tube as described above;
A third component can also be diffused into the seven layers from inside the tube at high temperatures. The source of diffusion may be vapor, liquid, or solid, and the diffusion process may be performed either before collapsing the tube or after partially collapsing it by making a small hole in the center. But it can be done. A separate diffusion step may be necessary if the tube is exposed to high ionic acid fc.

Alternatively, is it expensive? 1. If the resulting low viscosity of 1 degree and 7 is sufficient to allow stretching and diffusion to occur simultaneously, then diffusion can be caused by tube collapse. This can be done when the rod is drawn into a core shape.

FIG. 2 shows the IUT of a typical fiber manufactured by the method described above. This fiber has a central core 31 consisting of phosphorus silicide glass, and if the flow rate of the oxygen, S ring in the phosphorus oxysilk vessel 1 is gradually changed, the core 31 will gradually change. should have different refractive indices. Core 31σ) Circumference 171j f'J: 7I; a Covered with silicate glass cladding. The outer annular ring 33 of Jυ also consists of the warping force support tube collar used at the beginning, and although it does not play any role in terms of optical properties, it serves as a resourceful support and protection. . According to the results of measuring the degree of attenuation in the type of optical fiber shown in Figure 1, it is 0.75-/, 2
! ; only 7 dB/loss over micron wavelength;
Km is low and is constant within the above range. The content of hydroxyl impurities in the fibers is very low, which is believed to be due to the strong hygroscopicity of phosphorus pentoxide. That is, water remaining in the deposition apparatus is converted into non-volatile phosphoric acid upon contact and is not transported to the deposition zone.

[Brief explanation of drawings]

Figure WJ1 is a conceptual diagram of an apparatus for manufacturing the structure of the present invention. FIG. 2 is an enlarged sectional view of the light waveguide (optical fiber) of the present invention. 1... Phosphorus oxychloride container 2...
...Silicon tetrachloride container 3...Oxygen supply source 4.5.6...Line 7.8.9... Flow meter 10...
...River/Tube 11...Furnace 31, Core - 32...Tallarding 33...
... Annular ring (protection) Continuation of page 1 Priority claim 01974 August 7th [Phase] Igi■ Group 197 December 30th [Phase] Igi

Claims (1)

[Claims] (1) An optical glass structure having a core of glass formed from phosphorus pentoxide and silica and optionally additional components, and a cladding of silica glass having a lower refractive index than the core; of the optical glass, wherein the reduction in refractive index relative to the core is obtained at least in part by the concentration of phosphorus pentoxide in the cladding being zero or less than the concentration in the core. Structure.