JPH05127042A - Production of optical multiplexer/demultiplexer - Google Patents

Abstract

PURPOSE:To easily obtain required wavelength characteristics. CONSTITUTION:This process for production of the optical multiplexer- demultiplexer consists in obtaining an optical directional coupling part 6 by heating, welding and drawing two or more pieces of optical fibers in the state of bringing the side faces into contact with each other. The above-mentioned process is constituted by adding a step for applying a modified alkyl silicate soln. around the optical directional coupling part 6, a step for heating and vitrifying the soln. and a step for heating and annealing this glass film 12 and adjusting the dependency of the coupling coefft. in the optical directional coupling part on wavelengths.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical multiplexer / demultiplexer. In recent years, research and development for applying an optical communication system to a subscriber system have been carried out at a practical level. In order to realize bidirectional optical communication using wavelength division multiplexing in the subscriber system, an optical multiplexer / demultiplexer for branching or joining optical signals of different wavelengths is indispensable. Establishing mass-production technology is one of the key technologies for the practical application of subscriber optical communication systems.

An optical multiplexer / demultiplexer can be realized, for example, by constructing an optical directional coupling portion by fusing and extending a flat optical waveguide or an optical fiber. When manufacturing an optical multiplexer / demultiplexer, structural parameters such as the inter-core distance in the optical directional coupler directly affect the wavelength characteristics (wavelength dependence of the coupling coefficient (corresponding to the branching ratio) in the optical directional coupler). Therefore, it is desired to optimize the manufacturing method of the optical multiplexer / demultiplexer so that the required wavelength characteristics can be obtained.

[0003]

2. Description of the Related Art One of the conventional methods for manufacturing an optical multiplexer / demultiplexer is
The optical directional coupling portion is obtained by heating, fusing and stretching two or more optical fibers in a state where the side surfaces are in contact with each other.

Another conventional method of manufacturing an optical multiplexer / demultiplexer is such that at least a pair of cores are partially close to each other to form an optical directional coupling portion on an underclad having a relatively low refractive index. The method includes a step of forming the core and a step of forming an outer clad having the same refractive index as the under clad on the under clad so as to cover the core.

[0005]

According to the former manufacturing method of the related art, the structural parameters of the optical directional coupling portion are fused and
Since it was adjusted by the drawing speed and the heating temperature in the drawing work, it is difficult to make the inter-core distance, diameter or shape of the optical directional coupling portion a predetermined one, and obtain the required wavelength characteristics. There was a problem that it was not easy.

Also in the case of the latter conventional manufacturing method, since the core and the like are formed by, for example, the flame deposition method, there is a problem that it is not easy to obtain the required wavelength characteristics.
The present invention was created in view of such circumstances, and an object thereof is to provide a method for manufacturing an optical multiplexer / demultiplexer that can easily obtain a required wavelength characteristic.

[0007]

According to the method of manufacturing an optical multiplexer / demultiplexer of the present invention, the optical directivity is obtained by heating, fusing and stretching two or more optical fibers in a state where their side surfaces are in contact with each other. In a method for manufacturing an optical multiplexer / demultiplexer configured to obtain a coupling portion, a step of applying a modified alkyl silicate solution around the light-directional coupling portion, a step of heating the solution to vitrify, and this vitrification And annealing the heated product to adjust the wavelength dependence of the coupling coefficient in the light directional coupling portion.

Another method of manufacturing an optical multiplexer / demultiplexer according to the present invention comprises the step of forming the above-mentioned cores so that at least a pair of cores are partially close to each other on the underclad to form an optical directional coupling portion, The step of applying a modified alkyl silicate solution onto the underclad so as to cover the core, the step of heating the solution to vitrify, and the annealing of the vitrified material by heating to obtain the above optical directional coupling. Adjusting the wavelength dependence of the coupling coefficient in the section.

[0009]

According to the method of the present invention, the modified alkyl silicate solution is applied to the periphery of the light-directing binding portion or the core constituting the light-directing binding portion, the solution is heated to vitrify, and then vitrified. Since the annealed material (glass coating) is heated and annealed, by adjusting the degree of annealing by the heating temperature and the heating time,
The wavelength characteristic can be adjusted, and thus the required wavelength characteristic can be easily obtained. The annealing can be performed while monitoring the wavelength characteristics.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 (A) is a diagram for explaining the configuration and function of a fiber fusion-type optical multiplexer / demultiplexer, and FIG. 1 (B) is FIG.
It is a BB sectional view in (A). This fiber fusion splicing type optical coupler includes input ends 2 and 4, an optical directional coupler 6,
Output terminals 8 and 10 are provided.

In the optical directional coupler 6, the diameters of the core portions 6a and 6b corresponding to the cores of the respective fibers are sufficiently smaller than the original core diameter, and the core portions 6a and 6b are sufficiently close to each other. Therefore, mode coupling occurs, and a required branching ratio according to the structural parameters (length, diameter, core-to-core distance, relative refractive index difference, shape, etc.) of the optical directional coupling section 6 and the wavelength of propagating light is obtained. You can do it.

Specifically, when a signal light having a wavelength of P ₀ is input from the input end 2 or 4, the optical power P ₁ and P are output from the output ends 8 and 10 at predetermined branching ratios.
The optical signal of ₂ is output.

According to this structure, the optical transmission line can be directly connected by fusion splicing or the like, so that the loss of optical power is small, and since the main constituent parts are silica optical fibers, temperature and humidity can be used. It can be said that it has high reliability with respect to environmental conditions.

The branching ratio of this optical coupler (corresponding to the coupling ratio in the optical directional coupler) is P ₁ / (P ₁ + P ₂ ) or P ₂ / (P ₁ ) using the input / output optical power. + P ₂ )
It is represented by.

When such an optical directional coupling portion is formed, for example, two optical fibers arranged side by side so as to be in close contact with each other are partially heated by a burner or the like while these optical fibers are partially heated. A tensile force may be applied to the side surface to cause the side surface fusion and the stretching.

In this embodiment, as shown in FIG. 2, a glass coating 12 is formed around the light-directional coupling portion 6, and the glass coating 12 is heated by light from a high-intensity halogen lamp 14 for annealing. Then, the branching ratio in the optical directional coupler 6 is finely adjusted.

Specifically, it is as follows. As a parameter indicating the wavelength dependence of the branching ratio, the wavelength at which the branching ratio is highest at one output end and the wavelength at which the branching ratio is highest at the other output end are used. That is, the wavelength with the highest branching ratio at one output end is λ ₁ (μm)
If the wavelength at which the branching ratio at the other output end is the highest is λ ₂ (μm), the parameter is set to λ
Expressed as ₁ / λ ₂ .

First, the optical directional coupling portion 6 was prepared in consideration of the change in the branching ratio of the optical directional coupling portion 6 due to the formation of the glass film 12. The parameters at this time were 1.31 / 1.48.

Next, a modified alkyl silicate solution was applied to the light-directionally connecting portion 6 and heated at 150 ° C. for 1.5 hours to vitrify, thereby forming a glass coating 12. The refractive index of the glass film 12 is about 1.4.
4 and the parameter at this time is 1.32 / 1.57.
Became.

The glass coating 12 was annealed at 170 ° C. while actually measuring the branching ratio, and the annealing was stopped when the required parameters (1.31 / 1.55) were obtained. The heating time was about 3 hours, and the refractive index of the glass coating after annealing was about 1.43.

As described above, according to this embodiment, since the wavelength characteristics can be finely adjusted by annealing, the desired wavelength characteristics can be easily obtained. FIG. 3 shows the wavelength dependence of the branching ratio. In this graph, the vertical axis represents the branching ratio (dB) and the horizontal axis represents the wavelength (μm). A is the wavelength dependence of the branching ratio at one output end,
Shown by B is the wavelength dependence of the branching ratio at the other output end. Further, the solid line shows the characteristics before annealing, and the broken line shows the characteristics after annealing.

It is considered that the reason why the wavelength characteristic is changed by the annealing is that the refractive index of the glass film 12 is changed by the annealing. As a modified alkyl silicate solution, an inorganic coating material ETSB-600 manufactured by TSB Development Center Co., Ltd.
0, ETSB-7000, Grasmodoki (registered trademark), or X-500PA dissolved in an alcohol solvent such as methanol can be used.

In this embodiment, the reason why the annealing is performed by irradiating the light of the halogen lamp is to prevent the measurement instability of the branching ratio from being caused by the increase in the ambient temperature. As such a partial heating method, a method using a laser device such as a CO ₂ laser can also be adopted.

FIG. 4 is an explanatory view of a manufacturing process when the method of the present invention is applied to the manufacture of a waveguide type optical multiplexer / demultiplexer. First, as shown in a plan view of FIG. 4 (A) and a cross-sectional view of FIG. 4 (B), a pair of relatively high refractive index layers are formed on the underclad 18 having a relatively low refractive index formed on the substrate 16. The cores 20 and 22 are formed so that the refractive index cores 20 and 22 partially come close to each other to form the optical directional coupling portion 24.

The underclad 18 can be formed by the flame deposition method, and the cores 20 and 22 can be formed by etching the core layer obtained by the flame deposition method. Next, a modified alkyl silicate solution is applied onto the underclad 18 so as to cover the cores 20 and 22, and the solution is vitrified by heating as shown in FIG. 4 (C).

Then, while measuring the branching ratio, the vicinity of the light directional coupling portion 24 is heated by the halogen lamp 14 and annealed to obtain the required wavelength characteristics. Also in this embodiment, it is possible to easily obtain the required wavelength characteristics by changing the refractive index of the glass film 26 by annealing.

In the embodiment described above, the annealing is performed while actually measuring the branching ratio, but the optimum annealing condition may be obtained from the wavelength characteristics before the annealing, and the annealing may be performed under this condition.

[0028]

As described above, according to the present invention,
It is possible to provide a method of manufacturing an optical multiplexer / demultiplexer that easily obtains the required wavelength characteristics.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a configuration and a function of a fiber fusion type optical multiplexer / demultiplexer.

FIG. 2 is a diagram for explaining the annealing of the optical directional coupling section of the fiber fusion type optical multiplexer / demultiplexer shown in FIG.

FIG. 3 is a graph showing wavelength characteristics of branching ratio.

FIG. 4 is a diagram showing a manufacturing process of the waveguide type optical multiplexer / demultiplexer.

[Explanation of symbols]

 6,24 Light direction coupling part 12,26 Glass coating 14 Halogen lamp

Claims (3)

[Claims] 1. A method of manufacturing an optical multiplexer / demultiplexer in which two or more optical fibers are heated in a state where their side surfaces are in contact with each other and are fused and stretched to obtain an optical directional coupler (6). In the method, a step of applying a modified alkyl silicate solution around the light-directing coupling part (6), a step of heating the solution to vitrify, and a step of heating the vitrified material to anneal it. Adjusting the wavelength dependence of the coupling coefficient in the optical directional coupler, the method of manufacturing an optical multiplexer / demultiplexer. 2. The at least one pair of cores (20, 22) are partially close to each other on the underclad (18) and the optical directional coupling portion (2
4) forming the core so as to constitute the above step, applying a modified alkyl silicate solution onto the underclad so as to cover the core, heating the solution to vitrify, and And heating the converted material to anneal it to adjust the wavelength dependence of the coupling coefficient in the optical directional coupling section, the manufacturing method of the optical multiplexer / demultiplexer. 3. The method of manufacturing an optical multiplexer / demultiplexer according to claim 1, wherein the annealing is performed by irradiating light from a CO ₂ laser or a halogen lamp.