JPH09243854A - Production of optical fiber coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to execute monitoring at the time of coupler production at a prescribed wavelength and to facilitate the setting of production conditions by using a wavelength variable light source for monitoring at the time of production of the optical fiber coupler. SOLUTION: Two pieces of optical fibers 1 are heated and fused by a burner 4, by which an optical fiber fused part 2 is formed. The monitor light from the wavelength variable light source 5 is made incident on the one optical fiber 1. This monitor light is coherent light of a narrow half-value width and reflects between the fibers and between the coupler coupling part and a photodetector 8 and the fiber 3, thereby inducing the interface of the reflected light with each other. A frequency modulator 6 is disposed in order to control this light. Further, a depolarizer 7 is disposed in order to more approximately the state of the polarized light made incident on the coupler coupling part to non- polarized light. The wavelength variable light source 5 may be internally provided with either or both functions of the frequency modulator 6 and the depolarizer 7.

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 fiber coupler, and more particularly to a method for manufacturing an optical fiber coupler which can monitor a coupler at a desired wavelength.

[0002]

2. Description of the Related Art Optical fiber couplers are used in optical communication for branching an optical signal incident on an optical fiber into a plurality of optical fibers or for coupling optical signals incident on a plurality of optical fibers. As shown in FIG. 3, for example, the optical fiber coupler is manufactured by heating two optical fibers 11, heating and fusing them with a fusing burner 14, and stretching them. A method in which a light emitting diode (LED) or a laser diode (LD) is connected, a photodetector 16 is provided in an optical fiber 13 that branches monitor light, the intensity of emitted light is detected, and extension is stopped at a desired branching ratio. Is generally practiced.

[0003]

The monitor light used in manufacturing the coupler is generally a monitor method using an LD or LED having a wavelength of 1,310 nm or 1,550 nm.
60th IEICE General Conference 971 ”
An example using a 1.3 μm LD is disclosed, and in recent years, WD for EDFA (erbium-doped fiber amplifier)
In many cases, in M couplers, the demultiplexing wavelength is around 1,560 nm, and there are cases where the target wavelength is changed by several nm around it, so it is highly necessary to use a variable wavelength monitor light source. Is coherent and has a high degree of polarization, so care must be taken when using it.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing an optical fiber coupler which solves the above problems, and it is intended to use a variable wavelength light source as a monitor for manufacturing the optical fiber coupler. It also features a tunable light source, a frequency modulator and / or
Alternatively, it is equipped with a devolatizer.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for manufacturing an optical fiber coupler, which uses a variable wavelength light source as a monitor light source when manufacturing the optical fiber coupler in order to stably manufacture the optical fiber coupler. Is.
For example, when manufacturing a WDM coupler that multiplexes and demultiplexes light with a wavelength of 1,550 nm, the monitor light source is a general-purpose L with a wavelength of 1,550 nm.
An ED light source may be used, but when manufacturing a WDM coupler that multiplexes and demultiplexes 1,560 nm light, a general-purpose light source with a wavelength of 1,550 nm is not suitable, so a wavelength tunable light source that can change the output light wavelength as a monitor light source ( Tunable laser) to adjust to the target wavelength of 1,560 nm
This problem can be solved easily. However, the variable wavelength light source has a problem that it is coherent and has a high degree of polarization. In the present invention, a variable wavelength light source is used as a monitor light source, and a frequency modulator and a debolaizer are attached to this to solve this problem.

Regarding the method of manufacturing an optical fiber coupler according to the present invention, FIG. 1 shows a schematic diagram of an optical system at the time of manufacturing an optical fiber coupler.
And an optical fiber fusion section 2 in which they are heated and fused by a burner 4 for heating, fusing and stretching them, and a branched optical fiber 3. The monitor light from the variable wavelength light source 5 is incident on one of the optical fibers 1. This monitor light is coherent light with a narrow half-value width,
Since the reflected light is reflected between the coupler coupling portion, the photodetector 8 and the fiber, the reflected light interferes with each other. Therefore, the frequency modulator 6 is provided to control this, and further, the characteristics of the coupler differ depending on the polarization state. In some cases, this is provided with a depolarizer 7 in order to bring the polarization state incident on the coupler coupling section closer to non-polarization.

FIG. 2 is a schematic view of an optical system in the production of an optical fiber coupler according to another example of the present invention, in which the order of the frequency modulator 6 and the deborizer 7 in FIG. 1 is exchanged. Therefore, also in this case, the same effect as that of FIG. 1 can be obtained. For these, one or both of the functions of the frequency modulator 6 and the debolizer 7 are used for the variable wavelength light source 5.
May be provided. The wavelength tunable light source (tunable laser), the frequency modulator, and the debolizer may be known ones.

By doing so, it is possible to monitor the coupler at a desired wavelength at the time of manufacturing, it becomes easy to set the manufacturing conditions of the coupler, and it is possible to perform stable monitoring in a non-polarized state by using coherent light and influence of reflection. Since it is hard to receive, the characteristics of the manufactured coupler have excellent reproducibility.

[0009]

EXAMPLES Examples of the present invention and comparative examples will now be described.
These do not limit the invention. Example Two identical optical fibers with a diameter of 125 μm were prepared, the coating material covering these fibers was partially removed, and the bare fiber portions were kept in contact with each other and the contact portions were exposed to an oxyhydrogen flame. The fiber was drawn while heating. The monitor light was the output light from the wavelength tunable light source that passed through the frequency modulator and the debolizer, and was incident from one end of the first fiber.
It was set to 1,562 nm.

Stretching was carried out while monitoring the output light from the two optical fibers at the other end, and was adjusted so that the optical branching ratio was maximized. However, since there was no influence of reflection, the optical output from the coupler in the manufacturing process was adjusted. Almost no noise was observed in the intensity, and the coupler was stably manufactured. In this way the wavelength is 1.48 μm
And WDM coupler that combines and demultiplexes the light of 1.562 μm
When the optical characteristics were measured, the following results were obtained with respect to the insertion loss measurement value at 1,562 nm of the continuously manufactured coupler, but the variation was small. Experiment No. Insertion loss (dB) 1 0.38 2 0.28 3 0.30 4 0.34 5 0.33

Comparative Example Two identical optical fibers with a diameter of 125 μm were prepared, the coating material covering them was partially removed, and while leaving the bare fibers in contact with each other, this part was heated with an oxyhydrogen flame. It was stretched. In this case, the monitor light system was the method shown in FIG. 3, and the monitor light was the output light from the LD with a wavelength of 1.55 μm from one end of the first fiber, but the branching ratio was maximized at 1.55 μm. So 1.5
Since the branching ratio of 1.55 μm when the branching ratio reached the maximum at 62 μm was experimentally estimated by preliminarily making 5 WDM couplers and the target branching ratio was determined to be 92%, the extension of the monitor light was branched. When the ratio reached 92%, the production was stopped and a coupler was manufactured.

With a wavelength of 1.48 μm manufactured in this way
The WDM coupler that multiplexes and demultiplexes the light of 1.562 μm is produced by using polarized light with high coherency as the monitor light. The characteristics of the manufactured couplers also vary greatly, and the wavelengths of couplers manufactured continuously are 1,5.
The measured insertion loss values at 62 nm are as follows. Experiment No. Insertion loss (dB) 1 0.66 2 0.30 3 0.49 4 0.57 5 0.29

[0013]

According to the present invention, since it is possible to monitor at the time of manufacturing a coupler at a predetermined wavelength, it is possible to easily set the manufacturing conditions, and it is possible to monitor coherent light in a non-polarized state in a stable manner. It is difficult to receive, and the characteristics of the manufactured coupler have excellent reproducibility.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing optical system in a method for manufacturing an optical fiber coupler according to the present invention.

FIG. 2 is a schematic view showing another embodiment of the manufacturing optical system in the method for manufacturing an optical fiber coupler according to the present invention.

FIG. 3 is a schematic view of a manufacturing optical system in a conventionally known manufacturing method of an optical fiber coupler.

[Explanation of symbols]

 1, 3, 11, 13 ... Optical fiber 2, 12 ... Optical fiber fusion part 4, 14 ... Burner for fiber heating and fusion 5 ... Wavelength variable light source 6 ... Frequency modulator 7 ... Debolaizer 8, 16 ... Photodetector 15 ... Fixed wavelength light source (LD)

Claims (2)

[Claims] 1. A method of manufacturing an optical fiber coupler, wherein a variable wavelength light source is used as a monitor for manufacturing the optical fiber coupler. 2. The method for manufacturing an optical fiber coupler according to claim 1, wherein the variable wavelength light source is provided with a frequency modulator and / or a debolizer.