JPS6067908A - Optical fiber and its manufacture - Google Patents

Abstract

PURPOSE:To make metal and semiconductor into a fiber as well as a quartz glass fiber by embedding the metal and semiconductor in an optical fiber consisting principally of quartz glass. CONSTITUTION:A material A is used as an insert base material 10a and a material A, material B, or quartz glass for stress induction is used as a base material 10b at the circumference of synthesized optical fiber base materials 8 and 9. Further, base materials, i.e. materials A for the base materials 10a and 10b, and materials A or B, or quartgz glass for stress induction for base materials 10c and 10d are inserted into a quartz glass pipe 12 and drawn. The materials A or B, or quartz glass for stress induction deforms from the circular materials into a sector shape to fill circumferential gaps because they are low in softening point or fustion point than pure quartz glass. The large difference in coefficient of thermal expansion between the metal and glass induces axial stress in the section of the core of the optical fiber, so the function of a sensor and the function for maintaining polarization are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new optical fiber structure for realizing an optical fiber array for an optical fiber sensor, and a method for manufacturing the same.

Conventionally, it has been necessary to integrate metal scraps, which are dissimilar materials, as optical fibers for optical fiber sensors. It was covered very thickly. Alternatively, when drawing the optical fiber tm, it was coated with a low melting point metal such as indium.

In the former case, there is a problem that the attachment of the metal and the optical fiber is not necessarily uniform, and it is extremely difficult to attach the metal over a long length.

On the other hand, in the latter case, it is difficult to coat the optical fiber unless it is a metal with a low melting point such as indium, and there is a drawback that it is not possible to coat the optical fiber with a metal that is compatible with the sensor, such as a high melting point metal such as a magnetic material. .

In either case, conventional methods have not been able to stably coat optical fibers with materials such as hard materials or semiconductors, so it has been thought that there is no integrated structure of optical fibers and metals.

The present invention proposes a G structure in which metals and semiconductors are embedded in an optical fiber whose main component is silica glass, and a method for using the M structure, and it shows that silica glass and metals and semiconductors, which are n-type materials, can also be made into fibers. It was used.

FIG. 1 is a cross-sectional view showing the structure of the present invention, where 1 is a core, 2 is a metal or semiconductor, 8 is a cladding, No. is an outer covering quartz glass, 5 is an intermediate quartz glass, and 6 is a metal of the same type as shown in 2. Or a semiconductor.

FIG. 1 (al indicates a case where metal or semiconductor 2 (hereinafter referred to as material A) is arranged symmetrically on both sides of core l, and material A is generally selected from a substance having a lower melting point than quartz glass. Figure 1 (b) shows the case where four pieces of material A are arranged around the core l, and when material A is continuous, Figure 1 (c
It becomes ring-shaped as shown in l. Figures 1(d) and 1(el are cases in which the shape is different from that of material A in Figure 1(al).Metals or semiconductors have a larger coefficient of thermal expansion than silica glass in most cases, so Figure 1 (a) +
(dl # (e) Stress is applied to the core shown by K. As a result, the stress causes one-sided refractive index anisotropy, resulting in a stress-applied polarization-maintaining optical fiber. Since the wavefront is actively used, fa), (, il, and tel in Fig. 1 are suitable for polarization-maintaining optical fibers. Fig. 1 (f) is a further developed form of Fig. 1 (cl), and material A is used. This is the case of double layering.Figure 1 (bl
, (c), and (f) are used for polarization maintenance by adding screws to the sunlight 7 eyeper.

Figure 2 shows a case where a metal or semiconductor different from material A (this is called material B) is placed, 2a is material A, 2b
corresponds to material B. In the case of FIG. 2(b), the four metals or semiconductors may be of different types.

FIG. 8 is a cross-sectional view showing another structure of the present invention, and 2c is a stress imparting glass, which is a quartz glass to which various dopants are added so as to have a thermal expansion coefficient different from that of impurity-free quartz glass. Glass, 7 is a buffer layer. It is essential that an optical fiber for a sensor maintains its polarization plane, and FIG. 8 shows an example of a structure for realizing a stress-applied polarization-maintaining optical fiber. Figure 1 (al, (al
+ As shown in tel, it is possible to create a stress-applied polarization-maintaining optical fiber using a metal or semiconductor 2, but if the area of the metal or semiconductor 2 is small,
.

In the case of a circular shape as shown in Tfl, the effect of applying stress is small or almost absent. Therefore, as shown in Fig. 8, the stress-applying part should be made to face the material A [Fig. 8 (a)]
+ (cl * (di), the stress-applying glasses 2c are arranged symmetrically with respect to the core and on a - straight line [Fig. 8 (
bl , (el , (fl , (g) ”l) Therefore, it is possible to apply stress in one direction to the core. Alternatively, as shown in Fig. 8 (h), stress can be applied in an elliptical shape. A polarization-maintaining optical fiber of the form is realized.

FIG. 8 (fl, (gl, (hl) shows a structure in which metal or semiconductor 2a is arranged in a ring shape.

An implementation method according to the present invention will be described below. Figure 4 is similar to Figure 1 (al, (b), Figure 2 (a) I (bl, 8th
The figure shows a method for realizing at + (bl + (e), where 8 is the core part, 9 is the clad part, l Oa , l O
b is the insertion base material. First, an optical fiber base material is prepared.

That is, an optical fiber base material synthesized by MOVD or VAD, or a base material that is jacketed by placing the base material in a quartz glass pipe and heating it at high temperature, is subjected to ultrasonic processing to make holes, and its inner wall is polished or flame polished. . The number of holes should be two or more depending on the design, and should be chosen as symmetrically as possible with respect to the core. Next, material A is prepared for the insertion base material 10a, material A or material B, or quartz glass for applying stress is prepared for the insertion base material 10b, and the materials are inserted into the hole as shown in FIG. 4 in accordance with the hole diameter.

The next step, drawing, will be described later with reference to FIG.

Fig. 5 shows a method for realizing Fig. 1 fa), Fig. 2 (al), Fig. 8 (cl), where 8 is a core part, 9 is a clad part, 1
0a, Rob, 10c, 10d are material A or material B
11 is impurity-free quartz glass; and 12 is impurity-free quartz glass pipe. As shown in FIG. 5, around the optical fiber base material 8.9 synthesized by MOVD'P VAD etc., lOa is coated with material A, l0bK material A or material B, or quartz glass for applying stress, 1, Oc, 1Od is the same quartz glass as 11, or 10a r l ob is material A, loc
, lOd is a base material of material A or material B or quartz glass for applying stress, and a quartz glass pipe 12
and draw a line using the method shown in Figure 7. During this wire drawing, since material A or material B* or the quartz glass for applying stress has a lower softening point or melting point than pure silica glass, the circular matrix is deformed into a fan shape in order to fill the surrounding voids.

Figure 6 shows Figure 1 (c), (fl, Figure 2 fcl s
18 is material A, and 14 is a quartz glass pipe. As shown in FIG. Insert material A and draw a line.Figure 1(f),
In the case of the double 4111 structure shown in FIG. 2 (fl), it is sufficient to prepare a material A or material B pipe and an intermediate quartz glass pipe according to the structure.

In order to realize the shapes shown in Figures 1(e), 2(el), and 8(d), the optical fiber base material, material A or material B, or the quartz glass base material for applying stress must be shaped. , all you have to do is paste them together and draw a line. According to this method,
The shape shown in 2 can be changed freely.

Fig. 8 (fl, g) can be realized by a method combining Fig. 4 and Fig. 6. This is realized by the sixth manufacturing method, in which a fiber matrix is continuously formed.

Figure 7 is an explanatory diagram showing the method of wire drawing, and 15° and 16 are quartz glass plates inserted into the optical fiber base material to prevent material A, material B, and quartz glass for applying stress from protruding during wire drawing. Both have glass lids that are fused together. Reference numeral 17 is a quartz glass pipe that is continuous with or fused to the Hikari 7 Eyepa base material, 18 is a cap for evacuation, 19 is an O-ring, and 20 is a heater.

In order to carry out the present invention, it is necessary to take measures to prevent the oxidation of the metal or semiconductor from proceeding when drawing the metal or semiconductor. To do this, as shown in FIG. 7, first, a lid 15 is placed on one side of the base material 9 in which holes have been made for setting materials A, B or quartz glass for applying stress, and a quartz glass pipe 17 is placed at high temperature on the other end. After setting the attachment material A, material B, or quartz glass for applying stress, the quartz glass lid 16 is dropped. Next, the inside of the pipe 17 is heated to 10-2 to 1O-5 tor.
Either the optical fiber base material is heated to a high temperature while being held in a high vacuum of r to integrate it, or the material A, material B or the quartz glass for applying stress and the optical fiber base material are gradually separated from the quartz glass lid 15. After the quartz glass lid 16 was fused and integrated with the optical fiber base material, air was introduced into the quartz glass pipe and the IMF 15 was heated again at high temperature from the fused side. draw a line What should be noted is that the optical fiber base material and material A, material B, or quartz glass for applying stress be sealed to prevent air from entering.

Example Figure 8 (A fabrication example of al is shown below. An optical fiber base material obtained by the VAD method was vitrified to obtain an optical fiber base material of 50 nφ. The core part of this optical fiber base material was Diameter is 1.4m, relative refractive index difference between core and cladding is 0.6
%. Hole for 5 mat diameter nickel rod and B2O
A hole (diameter 1) in quartz glass for applying stress containing about 15 mo1% of 2 was cut by ultrasonic processing, and the inner wall was polished to a mirror surface. The pipe 17 is fused at high temperature, a nickel rod and a quartz glass rod for applying stress are inserted into the hole in the optical fiber base material as shown in FIG. vacuum degree 1
A high vacuum is applied to 0' torr, and a nickel rod and a quartz glass rod for applying stress are integrated in a drawing furnace. The degree of vacuum inside the quartz glass pipe during heating deteriorates to 5 X l O""-'torr due to gas generation from the nickel rod and the like. After the quartz glass lid 16 was also fused and integrated with the optical fiber base material, air was introduced into the quartz glass pipe, and the optical fiber base material was drawn by heating at a high temperature from the bottom again.

The characteristics of the obtained optical fiber are that the wavelength is 1.8 μm, and the loss of light that vibrates parallel to the direction connecting the center line of the nickel part, the core, and the quartz glass part for applying stress (this is called HEly1 mode light) is as follows. 100 dB/m.

The loss of light vibrating in a direction perpendicular to the center line (this is referred to as HE blue mode light) was 2 ab/m.

Therefore, when circularly polarized light was introduced into the 1 m long optical fiber of the present invention, the output light exhibited polarization characteristics with an extinction ratio close to 100 dB.

According to the present invention, for example, conventionally, in the case of magnetic sensors, a nickel film with a large magnetostrictive effect was coated around the optical fiber by vapor deposition or sputtering, but since it can be directly embedded into the optical fiber, it is extremely useful for mobile applications. It can be a good fiber-type magnetic sensor. This is suitable for weak detection of magnetism, temperature, pressure, rotation, etc. Since a fiber sensor detects changes in interference light at its output end, a polarization-maintaining optical fiber is essential. In the present invention, the large difference in coefficient of thermal expansion between metal and glass applies uniaxial stress to the core of the optical fiber within the cross section, so there is an advantage that two functions can be obtained: one for sensor use and one for maintaining polarization. The optical fiber polarizer realized in this example can be connected very well to ordinary single-seven-band optical fibers (because fusion splicing is possible) and has low connection loss, so it can be used for fiber sensors and optical communications. Widely applicable as an isolator element.

As a semiconductor, silicon is the most promising material because of its good compatibility with silica glass. However, when these metals and semiconductors are used, since pure silica glass has an extremely high glass softening point, the matching temperature range is extremely narrow, and metals and semiconductors may not be used.

In such cases, B, 08 or 0 may be used during silica glass synthesis.
It is necessary to add a large amount of impurities such as 802 to lower the melting point of the drawn glass base material, and the degree of impurity addition is determined so that the drawing temperature is between the melting point and boiling point of the metal or semiconductor.

As explained above, the present invention has the following advantages.

■It is not subject to the material limitations of metals or semiconductors, and can be made into core metal in the same way as quartz glass core metal.

■ Since metal or semiconductor and quartz glass are simultaneously drawn, it is possible to create optical fibers made of different materials, which are much more invasive than conventional methods.

■ Since the metal or semiconductor is embedded in the silica glass core, it is not affected by the oxidation of the metal or semiconductor.

■ Drawing a metal or semiconductor has a quenching effect and a shape effect that reduces the Ii product, so it can be expected to have superior mechanical strength of 1W compared to a metal or semiconductor in the form of a wire.

■ - You can freely define the shape and area of metal or semiconductor devices.

■ Compared to conventional optical core coatings, it is easier to produce and has a large economical effect, especially in the case of long pieces.

■ It is possible to bring the metal or semiconductor closer to the core, so 1. Conversion vehicles such as sensors are extremely expensive.

■ Since the metal or semiconductor and optical fiber base material are integrated, it is not affected by oxidation due to oxygen present in the atmosphere.

[Brief explanation of drawings]

1, 2, and 8 are cross-sectional views of optical fibers obtained by the method of the present invention; FIGS. 4, 5, and 6 are schematic views showing the arrangement of materials according to the invention; FIG. 7 is an explanatory diagram showing the line drawing method according to the present invention. l...core, 2.2a16...metal or semiconductor, 2b...metal or semiconductor different from 2a, 2C
...Quartz glass containing various dopants, 8.. Cland, 4.. External quartz glass, 5.. Intermediate quartz glass, 7.. Buffer layer, 8.. Core part, 9..・Clad part, 10a, lob, 10c, 10
d, 1B - Insertion base material, 11... Impurity-free quartz glass (silica glass rod for dummy), 12, 14,
17... Impurity-free quartz glass pipe, 15, 1
6...Quartz glass lid, 18...Evacuation cap, 19...0 ring, zO...Heater. Patent Applicant Nippon Telegraph and Telephone Public Corporation 1 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] L An optical fiber characterized in that a metal or a semiconductor is embedded continuously in the longitudinal direction of the optical fiber around or near the core of the optical fiber, the main component of which is quartz glass. A penetrating hole is made near the core of an optical fiber base material whose main component is quartz glass, one longitudinal end of the base material is hermetically sealed, and a quartz glass vibrator with an outer diameter equal to that of the base material is attached to the other end. After welding, a metal or semiconductor rod with an outer diameter approximately equal to the inner diameter of the hole is inserted, a quartz glass lid is dropped onto it, and the inside of the quartz glass pipe, including the hole, is evacuated to a high vacuum. The dropped quartz glass lid and the optical fiber base material are heated at high temperature to form an airtight unit, or the base material is heated sequentially from the sealed end to bond the optical fiber base material, metal or semiconductor, and quartz glass. A method for producing an optical fiber, which is characterized in that a starting base material is produced by integrating a lid, and this starting base material is heated again at a high temperature and drawn. & A base material having a stress applying part as an optical fiber base material. A method for manufacturing an optical fiber according to claim 2, characterized in that a hole is formed through a portion other than the stressed thick portion by using an optical fiber base material containing quartz glass as a main component. , insert it into a quartz glass pipe with one end sealed, insert a metal or semiconductor, or quartz glass for stress application between the base material and the quartz vibrator, After dropping the lid, the inside of the quartz glass pipe is evacuated to a high vacuum and the quartz glass lid and the optical fiber base material are heated to high temperature to form an airtight unit, or the quartz glass lid and the optical fiber base material are heated to form an airtight unit, or the quartz glass pipe is heated sequentially from the sealed end of the quartz glass pipe. It is characterized by heating and integrating an optical fiber base material with a metal or semiconductor, quartz glass for applying stress, and a quartz glass vessel to produce a starting base material, and then heating this starting base material again at a high temperature and drawing it. A patented method for manufacturing iba.