JPH01230445A - Light transmitter - Google Patents

Abstract

PURPOSE:To contrive improvement of manufacturing yield rate, by providing a interface layer having smoothly varying refractive index between core and mold and gradually increasing fluorine content to outward, in a light transmitter of single mode type. CONSTITUTION:A quartz fine particles aggregate (suite 4) is formed through hydrolysis reaction in an oxygen-hydrogen flame in VAD method, dehydrated and vitrified to transparent glass in a heating furnace 5 and a rod is obtained. Next, the suite is accumulated on a clad part of the rod by OVD method. At the time, SiCl4 and POCl3 are cast from a central nozzle of tetralayer tube 10 and Si, H2 and Ar, O2 are respectively fed from other nozzles. Thus, an interface layer 3 is smoothly formed between core 1 and clad 2 and fluorine content in the interface layer 3 is gradually increased to outward. A generation of interface defect at line drawing, thus a manufacturing yield rate is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a single mode optical transmission body containing fluorine.

[Prior art]

In recent years, transmission systems using optical transmission bodies have been applied not only to public communications but also to many other fields such as LAN (Local Area Network) and computer network. Furthermore, with the increasing demand for international communications, the installation of optical submarine cables is also progressing.

By the way, optical transmission bodies used in optical submarine cables are required to have lower loss and larger capacity than optical transmission bodies for ordinary public communication transmission. Therefore, efforts have been made to develop a single-mode optical transmission body having a refractive index distribution as shown in FIG. 4, and an ultra-low loss optical transmission body.

However, in the optical transmission body shown in FIG. 4, the refractive index between the core 1 and the cladding 2 is steep. Because of this change, when an optical transmitter is drawn from the base material, defects are likely to occur at the interface between the two, making it difficult to obtain an ultra-low loss product with good yield.

[Purpose of the invention]

In view of the above problems, it is an object of the present invention to provide an ultra-low loss single mode optical transmission body that can be manufactured with good yield, that is, stably.

[Structure of the invention]

In order to achieve the above object, the present invention provides a single mode optical transmission body in which at least one of the core and the cladding contains fluorine, in which the refractive index smoothly decreases between the core and the cladding. The interface layer is characterized in that the fluorine content in the interface layer gradually increases from the inside to the outside.

(Embodiments of the invention) Embodiments of the present invention will be described in detail below with reference to the drawings.

An embodiment of the single mode optical transmission body of the present invention is shown in FIG. As shown in this figure, the optical transmission body of the present invention has a core 1
Since an interface layer 3 whose refractive index smoothly changes from the refractive index value of the core 1 to the refractive index value of the clad 2 is provided between the core 1 and the clad 2, the refractive index distribution within the interface layer 3 is The interface layer 3 is characterized in that the fluorine content is gradually increased from the inside to the outside of the interface layer 3 so that the fluorine content decreases smoothly from the inside to the outside as described above. Furthermore, the content distribution of metal oxides used to increase the so-called refractive index, such as P2O6 and GeO□, in the interface layer 3 is gradually reduced from the inside to the outside of the interface layer 3. It is also characterized by being forced. Specific examples of the present invention are shown below.

5iC14 was introduced into a concentric quadruple tube burner, and oxygen-
A quartz fine particle aggregate is produced by a hydrolysis reaction in a hydrogen flame.
A quartz fine particle aggregate (hereinafter simply referred to as soot) was obtained by a so-called VAD method. This has an outer diameter of about 45mm and a length of 45mm.
It was 0 mm. The soot 4 thus obtained was introduced into a heating furnace 5 as shown in FIG. 2, where it was dehydrated and turned into transparent vitrification. Specifically, He was heated at 50f/min,
While flowing C1z at a rate of 1.51/min from the gas inlet 5, the soot 4 was first dehydrated by lowering the soot 4 at a rate of 200 mm/h while maintaining the maximum temperature in the furnace at approximately 1200°C. Then, the maximum temperature in the furnace was raised to 1620°C and He was increased to 50j! /mi
While flowing 1.5 E/min of C1z and C1z in the same manner as above, the soot 4 was lowered at 200 mm/h to form transparent vitrification. Next, this was stretched to produce two rods each having an outer diameter of 15 mm and a length of 200 mm. In addition, in FIG. 2, the reference numeral 7 is a gas exhaust port.

[Comparative example]

Subsequently, soot corresponding to the cladding portion 9 was deposited on one of the rods (referred to as rod A) by the so-called OVD method shown in FIG. Specifically, 5iC14 was introduced into a reciprocating concentric quadruple pipe burner 9 and subjected to a hydrolysis reaction. The deposition was stopped when the outer diameter reached 90 mm, and then dehydration and transparent vitrification were performed in a heating furnace 5 shown in FIG. Specifically, lle is 50j2
/min, while pouring C1z at 1.51/min from the gas inlet 5, the maximum temperature in the furnace was first raised to about 1200
'C, the soot containing the transparent opening and 7 doors A in the part corresponding to the core part 8 is pulled down at 200 mm/h to dehydrate it, then pulled up, and then heated to a maximum temperature of 136° in the furnace. C, and lie is 101/min.
, SiF, 0.8 ffi/min, and C1z
The soot was lowered at a rate of 200 f/h while flowing O. 1 l/min from the gas inlet 5 to convert the portion corresponding to the cladding portion 9 into transparent glass. The cladding 2 after being made into a transparent lath has a relative refractive index difference (Δ-) of 0 with respect to pure silica glass.
．． A transparent glass rod doped with fluorine corresponding to 35% and having a refractive index profile shown in FIG. 4 was obtained. Repeat this operation until the core-clad ratio is 10:
When the diameter reached 125, this glass rod was divided into three equal parts, each of which was drawn to obtain a light transmitting body with an outer diameter of 125 μm, which was coated with an ultraviolet curable resin to form a coated light transmitting body with an outer diameter of 380 μm. I got three. These were designated as Comparative Examples 1 to 3, respectively.

〔Example〕

On the other rod (hereinafter referred to as rod B), a third
Soot corresponding to the cladding portion 9 was deposited by the so-called OVD method shown in the figure. However, in this case, the quadruple pipe burner 1
5iCI4 (43°C, carrier gas Ar83 ml/ml) and POCl2 (0
°C, carrier gas Ar20 mi/m1n) was flowed,
5i (35°C1 carrier gas Ar 198ml/min) and H2 were flowed from the second nozzle from the inside. Further, Ar was flowed from the third nozzle, and 02 was flowed from the outermost nozzle. Under these conditions, a thickness of 1
mrrl soot was deposited. Thereafter, the POCh carrier gas flow rate was lowered to 15 mC'min, and soot with a thickness of 1 mm was deposited as a second layer. Similarly, the third layer is P.

The C13 carrier gas flow rate was 10 m/min,
Thereafter, while decreasing the amount of POCI+1 introduced by 5 mρ/min, a soot corresponding to the interface layer 3 in the present invention is formed, and from the 5th layer onwards, only 5iC14 and soot corresponding to the so-called cladding 2 are formed. did. In this way, the deposition was stopped when the outer diameter reached 90 mm, and dehydration and transparent vitrification were performed in the same manner and under the same conditions as in the case of rod A. When the refractive index distribution of the resulting transparent glass rod was examined, it was as shown in FIG. This was divided into three equal parts and drawn as in the case of the comparative example to obtain a light transmitting body with an outer diameter of 125 μm, and this was coated with an ultraviolet curable resin to obtain three coated light transmitting bodies with an outer diameter of 380 μm. .

These will be referred to as Examples 1 to 3 below.

The transmission loss of each of the above-mentioned three coated optical transmitters in the wavelength band of 1.55 μm was as shown in Table 1.

In Table 1, Ratio 1 means Comparative Example 1, and Actual 1 means Example 1. Further, the unit of cant-off wavelength and mode field diameter is μm, and the unit of transmission loss is dB/km.

Table 1 Length Kanto mode Transmission loss (km)
Wavelength - Radius ratio 113.1 1.51 10.8 0.1
97 ratio 214.5 1.49 10.7 0
．． 202 ratio 313.8 1.49 10.7
0.172 fruit 113.6 1.50 11.0
0.17B real 214.1 1.51 11.
1 0.182 actual 314.0 1.5011.0
0.175 As shown in Table 1 above, the loss of the example of the present invention obtained from rod B was lower than that of the comparative example obtained from rod A. Note that the length in Table 1 indicates the length of a good product obtained by dividing glass rods I''A and B into three equal parts and cutting them all to the same size. It is clear that a good quality optical transmission body can be obtained for a longer period of time.

In the case of the present invention, a minute amount of phosphorus exists in the interface layer 3 of the core cladding, and therefore the vitrification of the interface layer 3 proceeds faster than other parts, so the amount of fluorine doped in that part is smaller. Become. As a result, the refractive index distribution was as shown in FIG. 1, and the amount of fluorine doped gradually increased from the inside to the outside of the interface layer 3. Therefore, since the composition of the interface layer 3 does not change rapidly, defects are less likely to occur at the interface during drawing, and products with low loss can be manufactured with higher yield.

In the example, the interfacial layer 3 was doped with a small amount of phosphorus to promote transparent glass and the amount of fluorine doped was controlled. Vitrification speed can be controlled.

Furthermore, in this embodiment, only pure quartz is shown as the composition of the core 1, but it goes without saying that the present invention can also be applied to optical transmitters whose cores contain at least fluorine. In addition, germanium (specifically Ge) is added to the interface layer 3 instead of a minute amount of phosphorus (specifically P2O5).
It is also possible to use O□).

[Effects of the Invention] As described above, according to the present invention, a low-loss single-mode optical transmission body can be manufactured with high yield.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the refractive index distribution of an optical transmission body showing an embodiment of the present invention, Part 2 is a schematic diagram showing a method of dehydration and transparent vitrification, and Fig. 3 shows a method of forming a cladding part. The schematic diagram, FIG. 4, is a graph showing the refractive index distribution of a conventional single mode optical transmission body. 1~Core 2~Crat 3~Interfacial layer 4~Soot 5
~ Heating Furnace Patent Applicant Furukawa Electric Co., Ltd. Figure 1 "I L4.-. 1C14 Figure 6 5 Heating Furnace Figure 4

Claims (2)

[Claims] (1) In a single mode optical transmission body in which at least one of the core and the cladding contains fluorine, an interface layer whose refractive index smoothly decreases is provided between the core and the cladding, and the interface layer An optical transmission body characterized in that the fluorine content in the layers gradually increases from the inside to the outside. (2) The optical transmission body according to claim 1, wherein the content of metal oxide in the interface layer gradually decreases from the inside to the outside.