JPH07248423A - Optical fiber connecting method - Google Patents

Abstract

PURPOSE:To provide an optical fiber connecting method capable of connecting optical fibers varying in MFD to each other with low loss. CONSTITUTION:The MFD is locally expanded by heating the end face part of the optical fiber after the optical fiber 1 and the optical fiber 2 are connected. The output power of first wavelength light and the output power of second wavelength light which are changed by heating the end face part of the optical fiber 2 and are transmitted from the optical fiber 1 to the optical fiber 2 are measured. The heating is stopped where the loss of the first wavelength light and the second wavelength in the juncture of the first wavelength light and the second wavelength light attains an arbitrarily set value. As a result, the optical fiber 1 and the optical fiber 2 are connected with the low loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting optical fibers having different mode field diameters in an erbium-doped optical fiber (hereinafter referred to as EDF) amplifier or the like.

[0002]

2. Description of the Related Art In recent years, the operation of an erbium-doped optical fiber amplifier (hereinafter referred to as EDFA) in a system has been actively studied, and the system has been put into practical use. When designing a system using various optical amplifiers including this EDFA, several types of optical fibers are used as the optical fibers used in the optical amplifier. An optical amplifier is constructed by connecting these optical fibers to each other. When these optical fibers are connected to each other, it is necessary to reduce the loss of light in this connection.

At this time, as shown in FIG. 10, an optical fiber 101 having a mode field diameter (hereinafter referred to as MFD) 101a, which will be described later, and an M larger than the MFD 101a.
If an optical fiber having an FD 102a is butted and connected, the spot sizes of both optical fibers 101 and 102 become discontinuous at the connection point. Therefore, when the optical fibers 101 and 102 are butted and connected to each other, a large connection loss occurs. In this way, connecting optical fibers having different MFDs causes a large loss in principle. Further, the connection loss between optical fibers having different MFDs as shown in FIG. 10 is 20log ₁₀ {(2w ₁ w ₂ ) / (w ₁ ² + when the MFDs of the respective optical fibers are w ₁ and w _2. w ₂ ² )} [dB]. (D.Marcuse "Loss Analysis of Single-Mode F
iber Splices "BSTJ pp703-717, 1977) Then, for example, the splice loss due to the matching of a single mode optical fiber (hereinafter referred to as SMF) having an MFD of 10 μm and an EDF having an MFD of 5 μm is
It becomes 1.94 dB.

Usually, among the optical components constituting the EDFA,
Optical isolators other than EDF and wavelength multiplexers (hereinafter WD)
An SMF optical fiber having a larger MFD than the EDF is used as the optical fiber connected to (M). Also, S
Since the connection loss between the MF and the EDF causes the deterioration of the noise characteristics of the EDFA and the decrease of the gain efficiency, it is generally 0.2 dB.
The following is desirable. Therefore, in order to connect the optical fibers to each other with low loss, for example, the method shown in FIG. 11 has been adopted.

FIG. 11 is a configuration diagram in which one core is enlarged to connect optical fibers having different MFDs. As shown in FIG. 11, the core 112a of the optical fiber 112 is larger than the core 111a of the optical fiber 111. Therefore, by heating the end face portion of the optical fiber 111, the core 111a of the optical fiber 111 is enlarged, and the optical fiber 111
Expand the MFD of. As described above, in the core 111a of the optical fiber 111, the MFD of the optical fiber 111 is expanded in the axial direction of the optical fiber 111 by heating the end face portion of the optical fiber 111.
It is almost the same size as D. This way, the MFD
Even when optical fibers of different types are connected, they can be connected with low loss.

FIG. 12 shows a conventional forward excitation EDFA constructed by the above connection method. The signal light in the 1.55 μm band, which is the first wavelength, is a wavelength multiplexer (hereinafter, WDM
Input) 123. The pumping light in the 1.48 μm band, which is the second wavelength, is also input to the WDM 123. The WDM 123 combines the light of the first wavelength and the light of the second wavelength. These lights combined by the WDM 123 are transmitted through the optical fiber 121.

Here, the MFD is the length between the points where the electric field strength is 1 / e in the plane perpendicular to the light propagation direction as shown in FIG. Between the points where the electric field intensity is 1 / e, the light intensity distribution has a maximum value. Then, the optical fiber 121 is connected to the optical fiber 122 by using the above-described method of connecting optical fibers having different MFDs. In this way, optical fibers having different MFDs can be fusion-spliced with low loss.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The wavelengths used in the FA are the pumping light wavelength in the 1.48 μm band and the signal light wavelength in the 1.55 μm band. EDF
In A120, since the signal light wavelength and the pumping light wavelength are close to each other, both the pumping light wavelength and the signal light wavelength can be fusion-spliced with low loss.

However, the values at which the fusion splicing loss between the pumping light wavelength 0.98 μm band and the signal light wavelength 1.55 μm band are different are different. As a result, the excitation light wavelength is 0.98 μm
In the case of a band, it is considered that the above-mentioned connection method causes a large light loss in the connection between the optical fibers. Further, the excitation light wavelengths are 0.8 μm band, 0.65 μm band, 0.
In the case of the 5 μm band, in the above-mentioned connection method, the values at which the fusion splicing loss between the pumping light wavelength band and the signal light wavelength 1.55 μm band becomes the minimum are much different.

The present invention has been made in consideration of the above points, and uses the first wavelength and the second wavelength having different wavelength bands to connect optical fibers having different MFDs to each other.
It is an object of the present invention to provide an optical fiber connection method capable of connecting with low loss.

[0011]

In order to solve the above problems, the invention of claim 1 is an optical fiber having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands. 1. An optical fiber connection method for connecting 1 and an optical fiber 2 having a second MFD smaller than the first MFD, wherein an output end of the optical fiber 2 has a first wavelength light and a second wavelength light. An optical power meter 16 for measuring the output power of the first wavelength light separated by the distributor, and a light for measuring the output power of the second wavelength light separated by the distributor. After connecting the power meter 17 and connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 2, the MFD is locally enlarged and the end face portion of the optical fiber 2 is heated. The light flux that changes Driver transmitted from 1 to the optical fiber 2, an optical power meter 1 the output power of the first wavelength light
The output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which is changed by heating the end face portion of the optical fiber, is measured by the optical power meter 2, and When the loss in the wavelength light and the loss in the second wavelength light reach an arbitrarily set value, heating is stopped.

According to a second aspect of the present invention, the first wavelength band is different.
Optical fiber 1 having a first MFD for transmitting a second wavelength light and a second M, and a second M larger than the first MFD.
An optical fiber connection method for connecting an optical fiber 2 having an FD, in which a distributor for separating a first wavelength light and a second wavelength light is connected to an output end of the optical fiber 2, The optical power meter 16 for measuring the output power of the separated first wavelength light and the optical power meter 17 for measuring the output power of the second wavelength light separated by the distributor are connected to each other, and After connecting with the optical fiber 2,
By heating the end face portion of the optical fiber 1, the MFD
Is locally expanded, and the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 1 is measured by the optical power meter 1. The output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 1 is measured by the optical power meter 2 to obtain the first wavelength light. When the loss in the second wavelength light and the loss in the second wavelength light reach an arbitrarily set value, heating is stopped.

According to a third aspect of the present invention, in the first aspect of the invention, an optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands; An optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the MFD, which is an optical fiber 1
And the optical fiber 2 are connected to each other, only the light of the first wavelength is input to the optical fiber 1, and the first end is output at the output end of the optical fiber 1.
After measuring the output power of the light of wavelength, the optical fiber 1 and the optical fiber 2 are connected, and then the end face portion of the optical fiber 2 is heated to locally expand the MFD, and the end face portion of the optical fiber 2 is From the optical fiber 1 to the optical fiber, the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating, is measured, and the loss is changed by heating the end face portion of the optical fiber 2. The output power of the first wavelength light transmitted to the optical power meter 1
Measured at the output end of the optical fiber 1
Output power of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2. From the above, the loss of the first wavelength in the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained, and before the optical fiber 1 and the optical fiber 2 are connected, only the light of the second wavelength is emitted. By inputting to the fiber 1, measuring the output power of the second wavelength light at the output end of the optical fiber 1, connecting the optical fiber 1 and the optical fiber 2, and then heating the end face portion of the optical fiber 2. , The MFD is locally enlarged, and the loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 2, is measured, It changes by heating the end face part, The output power of the second wavelength light transmitted from the fiber 1 to the optical fiber 2 is measured by the optical power meter 2, and the output power of the second wavelength light measured at the output end of the optical fiber 1 and the optical fiber The optical fiber 1 and the optical fiber 2 are determined from the loss of the second wavelength light at the connection portion between the optical fiber 1 and the demultiplexer and the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2. The loss of the second wavelength at the connection portion of is converted and obtained, and heating is stopped when the loss of the first wavelength light and the loss of the second wavelength light reaches an arbitrarily set value.

According to a fourth aspect of the present invention, in the first aspect of the invention, an optical fiber 1 having a first MFD for transmitting the first wavelength light and the second wavelength light having different wavelength bands, and the first optical fiber 1 are provided. An optical fiber connecting method for connecting an optical fiber 2 having a second MFD larger than the MFD, which is an optical fiber 1
And the optical fiber 2 are connected to each other, only the light of the first wavelength is input to the optical fiber 1, and the first end is output at the output end of the optical fiber 1.
After measuring the output power of the light of wavelength, the optical fiber 1 and the optical fiber 2 are connected, and then the end face portion of the optical fiber 1 is heated to locally expand the MFD, and the end face portion of the optical fiber 1 is expanded. From the optical fiber 1 to the optical fiber, the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating, is measured, and the loss is changed by heating the end face portion of the optical fiber 1. The output power of the first wavelength light transmitted to the optical power meter 1
Measured at the output end of the optical fiber 1
Output power of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2. From the above, the loss of the first wavelength in the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained, and before the optical fiber 1 and the optical fiber 2 are connected, only the light of the second wavelength is emitted. By inputting to the fiber 1, measuring the output power of the second wavelength light at the output end of the optical fiber 1, connecting the optical fiber 1 and the optical fiber 2, and then heating the end face portion of the optical fiber 1. , The MFD is locally enlarged, and the loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating the end face portion of the optical fiber 1, is measured. It changes by heating the end face part, The output power of the second wavelength light transmitted from the fiber 1 to the optical fiber 2 is measured by the optical power meter 2, and the output power of the second wavelength light measured at the output end of the optical fiber 1 and the optical fiber The optical fiber 1 and the optical fiber 2 are determined from the loss of the second wavelength light at the connection portion between the optical fiber 1 and the demultiplexer and the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2. Is calculated by converting the loss of the second wavelength at the connection part of the optical fiber 1
The second wavelength light and the second wavelength at the connection between the optical fiber 2 and the optical fiber 2.
The heating is stopped when the loss with the light of wavelength reaches the value set arbitrarily.

According to a fifth aspect of the present invention, in the first aspect of the invention, an optical fiber 1 having a first MFD for transmitting the first wavelength light and the second wavelength light having different wavelength bands, and the first optical fiber 1 are provided. An optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the MFD, which is an optical fiber 1
The first wavelength light and the second
And the optical power of the first wavelength light is measured at the output end of the optical fiber 1 through an optical filter that removes the second wavelength light. After connecting with 2, the MFD is locally enlarged by heating the end face portion of the optical fiber 2, and the MFD is changed by heating the end face portion of the optical fiber 2. The output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which is changed by measuring the loss of the first wavelength light at the connection portion and heating the end face portion of the optical fiber 2 is measured. The output power of the first wavelength light measured by the power meter 1 and measured at the output end of the optical fiber 1 through the optical filter, and the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer. , Optical fiber 1 From the output power of the first wavelength light transmitted from the optical fiber 2 to the optical fiber 2, the loss of the first wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted and obtained. Before connecting to the optical fiber 2, the first wavelength light and the second wavelength light are input to the optical fiber 1, and the output power of the second wavelength light is changed to the first wavelength at the output end of the optical fiber 1. Measurement is performed through an optical filter that removes the light having the wavelength of, and the end face portion of the optical fiber 2 is heated after connecting the optical fiber 1 and the optical fiber 2 to each other.
The loss of the second wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, which is changed by locally expanding the FD and heating the end surface portion of the optical fiber 2, is measured, and the end surface of the optical fiber 2 is measured. The output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the portion is measured by the optical power meter 2 and measured through the optical filter at the output end of the optical fiber 1. The output power of the second wavelength light, the loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2. From the output power, the loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained, and the first wavelength light and the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 are calculated. Loss with wavelength light is arbitrary Now that reaches a set value, to stop the heating.

According to a sixth aspect of the present invention, in the first aspect of the invention, an optical fiber 1 having a first MFD for transmitting the first wavelength light and the second wavelength light having different wavelength bands, and the first optical fiber 1 are provided. An optical fiber connecting method for connecting an optical fiber 2 having a second MFD larger than the MFD, which is an optical fiber 1
The first wavelength light and the second
And the optical power of the first wavelength light is measured at the output end of the optical fiber 1 through an optical filter that removes the second wavelength light. After connecting with 2, the MFD is locally enlarged by heating the end face portion of the optical fiber 1, and the MFD is changed by heating the end face portion of the optical fiber 1. The loss of the first wavelength light at the connection portion is measured, and the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which is changed by heating the end face portion of the optical fiber 1 is measured. The output power of the first wavelength light measured by the power meter 1 and measured at the output end of the optical fiber 1 through the optical filter, and the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer. , Optical fiber 1 From the output power of the first wavelength light transmitted from the optical fiber 2 to the optical fiber 2, the loss of the first wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted and obtained. Before connecting to the optical fiber 2, the first wavelength light and the second wavelength light are input to the optical fiber 1, and the output power of the second wavelength light is changed to the first wavelength at the output end of the optical fiber 1. Measurement through an optical filter that removes the light having the wavelength of, and after connecting the optical fiber 1 and the optical fiber 2 to each other, by heating the end face portion of the optical fiber 1,
The loss of the second wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, which is changed by locally expanding the FD and heating the end surface portion of the optical fiber 1, is measured, and the end surface of the optical fiber 1 is measured. The output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the portion is measured by the optical power meter 2 and measured through the optical filter at the output end of the optical fiber 1. The output power of the second wavelength light, the loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2. From the output power, the loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained, and the first wavelength light and the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 are calculated. Loss with wavelength light is arbitrary Now that reaches a set value, to stop the heating.

According to a seventh aspect of the present invention, in the second aspect, the optical fiber 1 having the first MFD for transmitting the first wavelength light and the second wavelength light having different wavelength bands, and the first optical fiber 1 are provided. An optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the MFD, which is an optical fiber 1
When a rare earth element-doped optical fiber having an optical amplification action is used as the optical wavelength, both the first wavelength light, the second wavelength light, and either wavelength light are wavelength lights outside the optical amplification wavelength band.

According to an eighth aspect of the present invention, in the second aspect, the optical fiber 1 having the first MFD for transmitting the first wavelength light and the second wavelength light having different wavelength bands, and the first optical fiber 1 An optical fiber connecting method for connecting an optical fiber 2 having a second MFD larger than the MFD, which is an optical fiber 1
When a rare earth element-doped optical fiber having an optical amplification action is used as the optical wavelength, both the first wavelength light, the second wavelength light, and either wavelength light are wavelength lights outside the optical amplification wavelength band.

[0019]

According to the invention of claim 1, a distributor for separating the first wavelength light and the second wavelength light is connected to the output end of the optical fiber 2, and the first wavelength light separated by the distributor is connected. The optical power meter 16 for measuring the output power of the above is connected to the optical power meter 17 for measuring the output power of the second wavelength light separated by the distributor. Then, after connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 2, the MFD is locally enlarged. It is changed by heating the end face portion of the optical fiber 2,
First transmitted from the optical fiber 1 to the optical fiber 2,
Output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which is changed by measuring the output power of the light of the wavelength of 2 with the optical power meter 1 and heating the end face portion of the optical fiber 2. Is measured by the optical power meter 2. When the loss in the first wavelength light and the loss in the second wavelength light reach an arbitrarily set value, heating is stopped to connect the optical fiber 1 and the optical fiber 2.

According to the second aspect of the present invention, a distributor for separating the first wavelength light and the second wavelength light is connected to the output end of the optical fiber 2, and the first wavelength light separated by the distributor is connected. The optical power meter 16 for measuring the output power of the above is connected to the optical power meter 17 for measuring the output power of the second wavelength light separated by the distributor. Then, after connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 1, the MFD is locally enlarged.
The light is transmitted from the optical fiber 1 to the optical fiber 2, which is changed by heating the end face portion of the optical fiber 1.
The output power of the first wavelength light is measured by the optical power meter 1, and the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 is changed by heating the end face portion of the optical fiber 1. The output power is measured by the optical power meter 2. When the loss in the first wavelength light and the loss in the second wavelength light reach an arbitrarily set value, heating is stopped to connect the optical fiber 1 and the optical fiber 2.

In the invention of claim 3, before connecting the optical fibers 1 and 2 to each other, only the light of the first wavelength is input to the optical fiber 1 and the first wavelength is output at the output end of the optical fiber 1. Measure the output power of the light. After the optical fiber 1 and the optical fiber 2 are connected, the end face portion of the optical fiber 2 is heated to locally expand the MFD. The loss of the first wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 2, is measured. The optical fiber 1 to the optical fiber 2 are changed by heating the end face portion of the optical fiber 2.
The output power of the first wavelength light transmitted to the optical power meter 1 is measured. The output power of the first wavelength light measured at the output end of the optical fiber 1, the loss of the first wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 The loss of the first wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted and obtained from the output power of the first wavelength light transmitted to the optical fiber 1. On the other hand, before connecting the optical fibers 1 and 2, only the second wavelength light is input to the optical fiber 1 and the output power of the second wavelength light is measured at the output end of the optical fiber 1. After connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 2,
Expand the FD locally. The loss of the second wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 2, is measured. Then, the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 2 is measured by the optical power meter 2. The output power of the second wavelength light measured at the output end of the optical fiber 1, the loss of the second wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 The loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained from the output power of the second wavelength light transmitted to the optical fiber 1. When the loss between the first wavelength light and the second wavelength light at the connecting portion between the optical fiber 1 and the optical fiber 2 reaches an arbitrarily set value, heating is stopped to stop the optical fiber 1 and the optical fiber 2. And 2 are connected.

In the invention of claim 4, before connecting the optical fibers 1 and 2 to each other, only the light of the first wavelength is input to the optical fiber 1 and the first wavelength is output at the output end of the optical fiber 1. Measure the output power of the light. After the optical fiber 1 and the optical fiber 2 are connected, the end face portion of the optical fiber 1 is heated to locally expand the MFD. The loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 1, is measured. The optical fiber 1 to the optical fiber 2 are changed by heating the end face portion of the optical fiber 1.
The output power of the first wavelength light transmitted to the optical power meter 1 is measured. The output power of the first wavelength light measured at the output end of the optical fiber 1, the loss of the first wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 The loss of the first wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted and obtained from the output power of the first wavelength light transmitted to the optical fiber 1. On the other hand, before connecting the optical fibers 1 and 2, only the second wavelength light is input to the optical fiber 1 and the output power of the second wavelength light is measured at the output end of the optical fiber 1. After connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 1, M
Expand the FD locally. The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 1, is measured. Then, the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 1 is measured by the optical power meter 2. The output power of the second wavelength light measured at the output end of the optical fiber 1, the loss of the second wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 The loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained from the output power of the second wavelength light transmitted to the optical fiber 1. When the loss between the first wavelength light and the second wavelength light at the connecting portion between the optical fiber 1 and the optical fiber 2 reaches an arbitrarily set value, heating is stopped to stop the optical fiber 1 and the optical fiber 2. And 2 are connected.

In the invention of claim 5, before connecting the optical fibers 1 and 2, the first wavelength light and the second wavelength light are input to the optical fiber 1 and the output end of the optical fiber 1 is input. At, the output power of the first wavelength light is measured through an optical filter that removes the second wavelength light. After the optical fiber 1 and the optical fiber 2 are connected, the end face portion of the optical fiber 2 is heated to locally expand the MFD. The loss of the first wavelength light at the connecting portion between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 2, is measured. Then, the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the optical fiber 2, is measured by the optical power meter 1. The output power of the first wavelength light measured through the optical filter at the output end of the optical fiber 1, the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 From the output power of the first wavelength light transmitted to the optical fiber 2,
The loss of the first wavelength at the connection between the optical fibers 1 and 2 is converted and obtained. On the other hand, before connecting the optical fiber 1 and the optical fiber 2, the first wavelength light and the second wavelength light are input to the optical fiber 1, and the second wavelength light of the second wavelength light is output at the output end of the optical fiber 1. The output power is measured through an optical filter that removes the first wavelength light. After the optical fiber 1 and the optical fiber 2 are connected, the end face portion of the optical fiber 2 is heated to locally expand the MFD. It is changed by heating the end face portion of the optical fiber 2,
The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer is measured. Then, the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 2 is measured by the optical power meter 2. These optical fibers 1
Output power of the second wavelength light measured through the optical filter at the output end of the optical fiber, loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and transmission from the optical fiber 1 to the optical fiber 2. The loss of the second wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted and obtained from the output power of the second wavelength light thus received. When the loss between the first wavelength light and the second wavelength light at the connecting portion between the optical fiber 1 and the optical fiber 2 reaches an arbitrarily set value, heating is stopped to stop the optical fiber 1 and the optical fiber 2. And 2 are connected.

In the sixth aspect of the present invention, before connecting the optical fibers 1 and 2, the first wavelength light and the second wavelength light are input to the optical fiber 1 and the output end of the optical fiber 1 is input. At, the output power of the first wavelength light is measured through an optical filter that removes the second wavelength light. After the optical fiber 1 and the optical fiber 2 are connected, the end face portion of the optical fiber 1 is heated to locally expand the MFD. The loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which changes by heating the end face portion of the optical fiber 1, is measured. Then, the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 1 is measured by the optical power meter 1. The output power of the first wavelength light measured through the optical filter at the output end of the optical fiber 1, the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 From the output power of the first wavelength light transmitted to the optical fiber 2,
The loss of the first wavelength at the connection between the optical fibers 1 and 2 is converted and obtained. On the other hand, before connecting the optical fiber 1 and the optical fiber 2, the first wavelength light and the second wavelength light are input to the optical fiber 1, and the second wavelength light of the second wavelength light is output at the output end of the optical fiber 1. The output power is measured through an optical filter that removes the first wavelength light. After the optical fiber 1 and the optical fiber 2 are connected, the end face portion of the optical fiber 1 is heated to locally expand the MFD. It is changed by heating the end face portion of the optical fiber 1,
The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer is measured. Then, the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which changes by heating the end face portion of the optical fiber 1 is measured by the optical power meter 2. These optical fibers 1
Output power of the second wavelength light measured through the optical filter at the output end of the optical fiber, loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and transmission from the optical fiber 1 to the optical fiber 2. The loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained from the output power of the second wavelength light thus received. When the loss between the first wavelength light and the second wavelength light at the connection between the optical fiber 1 and the optical fiber 2 reaches an arbitrarily set value, the heating is stopped to stop the optical fiber 1 and the optical fiber 2. And 2 are connected.

In the inventions of claims 7 and 8, when a rare earth element-doped optical fiber having an optical amplifying action is used as the optical fiber 1, both the first wavelength light and the second wavelength light,
Alternatively, one of the wavelength lights is a wavelength light outside the optical amplification wavelength band. As a result, the signal light having the first wavelength light is not amplified by the pumping light having the second wavelength light.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical fiber connecting method according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. The first wavelength light is input to the multiplexer 11 such as a wavelength multiplexer or an optical coupler. The second wavelength light is also input to the multiplexer 11. The power of each wavelength light input to the multiplexer 11 is constant. The multiplexer 11 combines the first wavelength light and the second wavelength light. A combiner port 12 is connected to the combiner 11 for transmitting and connecting the first wavelength light and the second wavelength light combined by the combiner 11 to an optical fiber. The combining port 12 is connected to the optical fiber 1 for transmitting the first wavelength light and the second wavelength light combined by the multiplexer 11. Here, as a method of connecting the composite port 12 and the optical fiber 1, since the composite port 12 and the optical fiber 1 are not attached and detached, fusion splicing by arc discharge or the like can be mentioned. The optical fiber 1 is connected to the optical fiber 2 at the connection point A.
Connected with. As a result, the first wavelength light and the second wavelength light combined by the multiplexer 11 are
From the optical fiber 2 to the optical fiber 2. The optical fiber 1 and the optical fiber 2 at the connection point A are fused by arc discharge or the like for a long time or a short time, and the optical fiber 1 and the optical fiber 2 are fusion-spliced. After the fusion splicing, as shown in FIG. 11, the optical fiber having the smaller MFD is heated for a long time to expand the MFD.

As a method of connecting the optical fibers 1 and 2 at the connection point A and a heating method, only the optical fiber fusion machine is used to perform both the fusion of the optical fibers and the expansion of the MFD. Alternatively, there is a method of expanding the MFD by using another heating device such as a micro torch after fusing with an optical fiber fusion machine. Any of these methods may be used.

The optical fiber 2 is connected to the combining port 14. Here, as a method of connecting the optical fiber 2 and the synthetic port 14, a connector connection such as a ferrule-type connector can be mentioned because the optical fiber 2 and the synthetic port 14 are attached and detached as described later. Then, the combining port 14 that is connector-connected to the optical fiber 2 is connected to the demultiplexer 15. From the above, the first wavelength light and the second wavelength light are combined by the multiplexer 11, and the wavelength multiplexed light combined by this multiplexer 11 is combined by the combining port 12 of the multiplexer 11.
The light propagates through the optical fiber 1, the optical fiber 2, and the combining port 14, and is input to the demultiplexer 15.

It is also conceivable to transmit the first wavelength light and the second wavelength light combined by the multiplexer 11 to the demultiplexer 15 without using the above-mentioned combining port 12. That is, the multiplexer 11 configures the multiplexer 11 by using the optical fiber 1 instead of the combining port 12. From this, the first wavelength light and the second wavelength light are combined by the multiplexer 11, and the wavelength multiplexed light combined by this multiplexer 11 is combined with the optical fiber 1, the optical fiber 2, and the combining port 14. To be input to the demultiplexer 15.

The demultiplexer 15 demultiplexes the wavelength multiplexed light of the first wavelength light and the second wavelength light propagated from the optical fiber 2. The demultiplexer 15 outputs the first wavelength light from the demultiplexed first wavelength light and second wavelength light using an optical power meter (hereinafter, referred to as an optical power meter).
Output to 16). In addition, the demultiplexer 15 is
The second wavelength light is output from the demultiplexed first wavelength light and second wavelength light to the OPM 17. OPM16 is this OP
This is a device for measuring the output power of the first wavelength light input to M16. The OPM 17 is a device that measures the power of the second wavelength light input to the OPM 17. By measuring the output power of the first wavelength light and the power of the second wavelength light using the OPM 16 and OPM 17, the loss change at the connection point A between the optical fiber 1 and the optical fiber 2 is monitored.

A method of connecting an optical fiber in an EDFA excited by 0.98 μm based on the configuration of FIG. 1 will be described with reference to FIG. The signal light in the 1.55 μm band that is the first wavelength light is transmitted through the optical fiber 1 and input to the WDM 31. Further, the pumping light in the 0.98 μm band which is the second wavelength light is also transmitted through the optical fiber 1 and input to the WDM 31. At this time, from the input point of the first wavelength light to the WDM3
An optical isolator 30 is provided between the optical fibers 1 and 1 in order to prevent light returning to the input side, which is generated in the optical fiber 1 or the optical fiber 2.

The WDM 31 is a 0.98 μm / 1.55 μm WDM since the 1.55 μm band signal light and the 0.98 μm band pump light are input to the WDM 31. The wavelength-multiplexed light composed of the signal light in the 1.55 μm band and the pump light in the 0.98 μm band, which is combined by the WDM 31, propagates from the WDM 31 through the optical fiber 1, the optical fiber 2, and the combining port 34, and then the demultiplexer 35 Entered in. The wavelength demultiplexer 35 is 0.98 μm / 1.55 μm WDM because the wavelength division multiplexed light including the signal light in the 1.55 μm band and the excitation light in the 0.98 μm band is input to the demultiplexer 35.

The demultiplexer 35 demultiplexes the propagated wavelength multiplexed light into signal light in the 1.55 μm band which is the first wavelength and pumping light in the 0.98 μm band which is the second wavelength. To do. The demultiplexer 35 has a demultiplexed first wavelength of 1.55.
Signal light in the μm band, light, and second wavelength light of 0.98 μm
From the pumping light of the band, the signal light of the band of 1.55 μm
Output to. In addition, the demultiplexer 35 pumps the 0.98 μm band from the demultiplexed first wavelength 1.55 μm band signal light and light and the second wavelength light 0.98 band μm pump light. Outputs light to OPM17.

Here, as the optical fiber 1, SMF which is an optical fiber for WDM is used. Further, an EDF is used for the optical fiber 2. As described above, this is usually due to the fact that, among the optical components constituting the EDFA, the optical fibers connected to the optical isolator other than the EDF, the WDM, etc.
An SMF optical fiber having a larger MFD than the EDF is used. Therefore, at the connection point A, S which is the optical fiber 1
The MF and the EDF which is the optical fiber 2 are connected. From this fact, the SMF which is the optical fiber 1 and the EDF which is the optical fiber 2 have a signal light of 1.55 μm band and 0.98 μm.
Excitation light in the m band is propagated. In EDF,
The signal light in the 1.55 μm band is amplified by the excitation light in the 0.98 μm band.

As described above, the optical fiber 1 and the optical fiber 2 are connected at the connection point A. This connection point A
The connection loss between the optical fiber 1 and the optical fiber 2 in 1 changes depending on the heating time by the heating device. Further, the loss with respect to the heating time depends on the wavelength.

FIG. 2 is a diagram showing the ratio of wavelength to loss with respect to heating time. The wavelength in the 1.55 μm band has a heating time of 20 to 30 seconds, and the loss is the smallest. 0.
The wavelength in the 98 μm band has the smallest loss when the heating time is 8 seconds to 10 seconds. Thus, depending on the wavelength, the point where the loss is the smallest changes. Therefore, for example, when it is desired to minimize the loss at the first wavelength, the heating is stopped when the power of the OPM 1 becomes maximum.
On the other hand, when it is desired to minimize the loss at the second wavelength, the heating is stopped when the power of the OPM 2 becomes maximum. In this way, by measuring the power of the first wavelength light and the power of the second wavelength light by using the OPM 16 and OPM 17, the loss change at the connection point A between the optical fiber 1 and the optical fiber 2 is monitored.

Here, in general, when the connection loss between the optical fibers in the optical amplifier is large, the optical noise characteristic is deteriorated and the output signal light power after amplification is also reduced.

The relationship between the optical noise characteristic or the optical noise characteristic of the output signal light power and the loss at the connection point A will be described below. Noise figure of EDFA: NF is noise figure of EDF NFE
From DF [dB] and the loss Lin [dB] from the input point of the EDFA to the EDF, NF = NFEDF [dB] + Lin [dB]. Lin is an optical isolator or WDM for oscillation prevention
And the loss at the signal light wavelength at the connection point A also have an effect. Therefore, in order to reduce the noise figure of the EDFA of FIG. 3, it is necessary to reduce the loss of signal light in the 1.55 μm band at the connection point A.

On the other hand, the relation between the noise characteristic of light or the output signal light power after amplification and the loss at the connection point A of the output signal light power will be described below with reference to FIG.
Let Psin be the power of the first wavelength light input to the connection point A, and Ppin be the power of the second wavelength light input to the connection point A.
And the loss in the first wavelength light at the connection point A is L1,
It is assumed that the loss in the second wavelength light at the connection point A is L2, and that the larger the values of L1 and L2 are, the larger the loss is.
The transmittance of the loss L1 is T1, the transmittance of the loss L2 is T2, and when the loss L = 0, the transmittance T = 1 and the loss
The transmittance T decreases as L increases. Also, loss L = ∞
Is the transmittance T = 0. The power of the first wavelength light input to the optical fiber 2 is Ps, the power of the second wavelength light input to the optical fiber 2 is Pp, and the power of the first wavelength light output from the optical fiber 2 is Let Psout be Ps = Psin × T1 (1) Pp = Ppin × T2 (2). Further, when the conversion efficiency from the excitation light that is the second wavelength light in the optical fiber 2 to the signal light that is the first wavelength light is η, Psout = Ps + ηPp (3). By substituting the equations (1) and (2) into the equation (3), Psout = Psin × T1 + ηPpin × T2 (4) Now, consider the following two states. First, when the transmittance T2 of the loss L2 is improved from the transmittance T1 of the loss L1,
In other words, T1 <T2 In this case, T1 and T2 are set to T11 and T21, respectively, and the power of the first wavelength light output from the optical fiber 2 is set to Psout.
Set to 1. Next, when the transmittance T1 of the loss L1 is improved from the transmittance T2 of the loss L2, that is, T1> T2, T1 and T2 in this case are set to T12 and T22, respectively, and the first output from the optical fiber 2 is performed. Psout the power of wavelength light
Set to 2. That is, T11 <T12, T21> T22. From equation (4), Psout1-Psout2 = Psin × T11 + ηPpin × T21- (Ps
in × T12 + ηPpin × T22) = Psin (T11−T12) + ηPpin (T21−T22) Here, Psin <1mw and ηPpin> 50mw, so that Psin << ηPpin. Also, the above-mentioned T11 <T1
2. From T21> T22, T11-T12 <0, T21-T2
2> 0, but | T11-T12 | ≈ | T21-T22 |
Then, Psout1-Psout2> 0, and Psout1> Pso
It becomes ut2.

From this point, in order to obtain a larger amplified output signal light power, it is necessary to reduce the loss of the pumping light in the 0.98 μm band of the connection point A. The relationship between the optical noise characteristics and the loss at the connection point A, and the relationship between the output signal light power after amplification and the loss at the connection point A are 0.98 described above.
Excitation light at μm, 0.8, 0.65, 0.5
Similar results are obtained with excitation light at μm.

Further, the noise figure of the forward excitation EDFA,
In order to satisfy both the output signal light power after amplification, referring to FIG. 2, the heating in the heating device is performed at a predetermined time when the loss values of both of them satisfy the arbitrarily set values. Just stop.

After the optical fiber 1 and the optical fiber 2 are connected with low loss by using the method described above, the optical fiber 2 and the synthetic port 34 which are connected to the connector are removed at the connection point B. Then, light can be transmitted by connecting the optical fiber 2 to another optical fiber by a connector. Here, at the connection point B, the optical fiber 2 may be fusion-spliced with another optical fiber or the like. When fusion-splicing the optical fiber 2 and another optical fiber or the like, the end face portion of the optical fiber 2 is cut and the cut end face portion of the optical fiber 2 is abutted with another optical fiber for optical transmission.

As described above, according to the first embodiment, when the optical fiber 2 and the other optical fiber 1 having a different MFD are fusion-spliced, by monitoring the loss at each wavelength, It is possible to perform fusion splicing after confirming that the desired loss has been achieved, such as the lowest loss at any wavelength.

4 and 5 are block diagrams showing a second embodiment of the present invention. 4 and 5, those having the same structure as that shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In the configuration of the second embodiment, as shown in FIG. 4, first, an OPM 16 for measuring the output power of the first wavelength light is provided at the output end of the optical fiber 1. Then, only the first wavelength light is input to the multiplexer 41. The first wavelength light is transmitted from the multiplexer 41 through the optical fiber 1 and input to the OPM 16. The OPM 16 measures the output power of the first wavelength light input from the optical fiber 1.

Next, as shown in FIG. 5, the OPM 1 for measuring the output power of the second wavelength light at the output end of the optical fiber 1
7 is provided. Then, only the second wavelength light is input to the multiplexer 41. The first wavelength light is transmitted from the multiplexer 41 through the optical fiber 1 and input to the OPM 17. OPM17
Measures the output power of the second wavelength light input from the optical fiber 1. After measuring the output power of the first wavelength light and the output power of the second wavelength light by the OPM 16 and OPM 17, the OPM is removed and the optical fiber 1 and the optical fiber 2 are connected as shown in FIG. .

From this, after measuring the output power of the first wavelength light and the output power of the second wavelength light by OPM16 and OPM17, OPM16 and OPM17 are removed and optical fiber 1 and optical fiber 2 are separated. By connecting, the configuration is the same as in FIG. That is, in the second embodiment, before connecting the optical fiber 1 and the optical fiber 2,
The optical fiber 1 is connected to OPM16 and OPM17. Then, the output power of the first wavelength light and the output power of the second wavelength light at the connection point A are measured by the OPM 16 and OPM 17, respectively.

After that, as in the first embodiment, the first wavelength light and the second wavelength light are input to the multiplexer 41. Multiplexer 41
Combines the first wavelength light and the second wavelength light. The wavelength multiplexed light composed of the first wavelength light and the second wavelength light is transmitted from the multiplexer 41 through the optical fiber 1, the optical fiber 2, and the combining port 14, and is input to the demultiplexer 15. . The wavelength division multiplexed light is separated by the demultiplexer 15 into the first wavelength light and the second wavelength light. The separated first wavelength light is input to the OPM 16 and the output power is measured.
In addition, the separated second wavelength light is input to the OPM 17, and the output power is measured.

Although not shown, the loss of the first wavelength light at the connection point B between the demultiplexer 15 and the optical fiber 2 and the demultiplexer 15 and the optical fiber 2 are measured by using a measuring device. The loss of the second wavelength light at the connection point B is also measured.

From the above, the loss of the first wavelength light at the connection point A between the optical fiber 1 and the optical fiber 2 is caused by the optical fiber 1 before connecting the optical fiber 1 and the optical fiber 2.
And the OPM 16 are connected to each other, and the output power of the first wavelength light obtained by measuring the first wavelength light with the OPM 16 and the optical fiber 1 and the optical fiber 2 are connected to each other, and then the first demultiplexer 15 separates them. Output power of the first wavelength light measured by the OPM 16 and the connection point between the demultiplexer 15 and the optical fiber 2 measured using a measuring device not shown.
It is calculated by converting the loss of the first wavelength light in B.

Regarding the loss of the second wavelength light at the connection point A between the optical fiber 1 and the optical fiber 2, the loss in the second wavelength light is converted in the same manner as the above-described conversion method of the loss of the first wavelength light. Ask for.

A method of obtaining the loss value at the connection point A based on the above-mentioned elements will be described below. In FIG. 4, before connecting the optical fiber 1 and the optical fiber 2, the OPM is connected to the optical fiber 1, and the OPM 16 and the OPM 17 are connected.
The output power of the first wavelength light and the output power of the second wavelength light measured by are set to Pref1 and Pref2, respectively. In FIG. 1, after the optical fiber 1 and the optical fiber 2 are connected, the loss of the first wavelength light at the connection point B between the demultiplexer 15 and the optical fiber 2 measured by the measuring device is LWD.
M1 and the optical fiber 1 and the optical fiber 2 are connected, and then the demultiplexer 15 and the optical fiber 2 are measured by a measuring device.
Let LWDM2 be the loss of the second wavelength light at the connection point B with. In FIG. 1, after the optical fiber 1 and the optical fiber 2 are connected, the output power of the first wavelength light measured by the OPM 16 for the first wavelength light separated by the demultiplexer 15 is defined as Pout1, and the optical fiber 1 After connecting the optical fiber 2 and the optical fiber 2, the output power of the second wavelength light separated by the demultiplexer 15 and measured by the OPM 17 is Pout2. If the loss at the connection point A at the first wavelength is Loss1 and the loss at the connection point A at the second wavelength is Loss2, then Loss1 = | Pout1-Pref1 + LWDM1 | Loss2 = | Pout2-Pref2 + LWDM2 |. However, the units of the output power level and the loss at this time are [dBm] and [dB], respectively. Regarding the loss, the code is 0 dB or more.

As described above, according to the second embodiment, the first
Other than the embodiment, the connection point between the optical fiber 1 and the optical fiber 2
The loss in A can be monitored. In addition, according to the second embodiment, it is possible to find an increase in the loss at the connection point due to a defective fusion splicing such as a stain or scratch on the connection end face of the optical fiber, a misalignment between the optical fibers 1 and 2. Therefore, in the second embodiment, the first
A highly accurate connection loss can be obtained from the loss at the connection point A between the optical fiber 1 and the optical fiber 2 obtained in the embodiment.

A rare earth element-doped optical fiber such as EDF is
Since the absorption loss is large, it may be considered to use an optical fiber 1 doped with a rare earth element such as EDF.

FIGS. 6 and 7 are block diagrams showing a third embodiment of the present invention. 6 and 7, those having the same structure as that shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The configuration of the third embodiment is shown in FIG.
As shown in FIG. 1, first, the OPM 16 for measuring the output power of the first wavelength light is provided at the output end of the optical fiber 1. Then, in the third embodiment, both wavelengths of the first wavelength light and the second wavelength light are input to the multiplexer 41. The wavelength-multiplexed light combined by the multiplexer 41 is transmitted from the multiplexer 61 to the optical fiber 1
Transmitted to. From this, the optical fiber 1 has a first
Wavelength-multiplexed light composed of the second wavelength light and the second wavelength light is transmitted. Here, an optical filter 62 for removing the second wavelength light is provided on the optical fiber 1. By this, O
Only the first wavelength light is input to the PM 16. OPM
16 measures the output power of the first wavelength light input from the optical filter 62.

Next, as shown in FIG. 7, the OPM 1 for measuring the output power of the second wavelength light at the output end of the optical fiber 1
7 is provided. Then, both wavelengths of the first wavelength light and the second wavelength light are input to the multiplexer 41. The wavelength-multiplexed light combined by the multiplexer 71 is sent from the multiplexer 41 to the optical fiber 1
Transmitted to. Here, an optical filter 72 that removes the first wavelength light is provided on the optical fiber 1. As a result, only the second wavelength light is input to the OPM 17.
The OPM 17 measures the output power of the first wavelength light input from the optical filter 72. OPM16, OPM17
The output power of the first wavelength light and the second
After measuring the output power of the
6, the OPM 17 is removed and the optical fiber 1 and the optical fiber 2 are connected to obtain the same configuration as in FIG.

The loss of the first wavelength light at the connection point A between the optical fiber 1 and the optical fiber 2 is caused by the optical fiber 1 and the OPM before connecting the optical fiber 1 and the optical fiber 2.
16 is connected, and the output power of the first wavelength light measured by the OPM 16 for the first wavelength light by the optical filter 61 and the optical fiber 1 and the optical fiber 2 are connected,
The first wavelength light separated by the demultiplexer 15 is supplied to the OPM 1
The output power of the first wavelength light measured by 6 and the optical fiber 1 and the optical fiber 2 are connected and then measured by using a measuring device (not shown).
The loss of the first wavelength light at the connection point B with and is calculated. Connection point A between optical fiber 1 and optical fiber 2
As for the loss of the second wavelength light in
The loss in the second wavelength light is converted and obtained in the same manner as the method of converting the loss in the wavelength light.

In the configuration of the second embodiment, as shown in FIGS. 4 and 5, an OPM for measuring the output power of wavelength light is provided in advance at the output end of the optical fiber 1. Then, only the other wavelength light is input to the multiplexer 41, and the output power of the other input to the multiplexer 41 is measured by the OPM. However, actually, when the optical fiber 1 described in the second embodiment is a rare earth element-doped optical fiber such as EDF, the signal light having the first wavelength at the connection point A is as shown in FIG. After the optical fiber 1 and the optical fiber 2 are connected, the first wavelength light and the second wavelength light are input to the combiner 11, so that they are amplified by the excitation light that is the second wavelength light.
Therefore, the conversion of the loss of the signal light amplified by the pump light at the connection point A uses the output power of the unamplified signal light measured by the OPM before connecting the optical fiber 1 and the optical fiber 2. It will be. Therefore,
The loss of the signal light amplified by the pumping light at the connection point A cannot be accurately converted. Therefore, in the configuration of the third embodiment, both wavelengths of light are input to the multiplexer 41 in advance,
By measuring the other output power by the OPM, the loss of the signal light amplified by the pumping light at the connection point A can be converted.

The configuration of the fourth embodiment will be described below. In the fourth embodiment, either one of the signal light having the first wavelength and the pumping light having the second wavelength is set to a wavelength outside the optical amplification wavelength band.

Here, in the case of a 0.98 μm pumped EDFA, the optical amplification characteristics of the signal light of the first wavelength light and the pump light of the second wavelength light are as shown in FIGS. 8 and 9, respectively. Is. From FIG. 8, in the case of the 0.98 μm pumped EDFA, the loss in the optical amplification characteristic is reduced by using the signal light in the 1.55 μm band with a wavelength smaller than the 1.50 μm band or a wavelength larger than the 1.60 μm band. To do. The signal light having a wavelength smaller than the 1.50 μm band or the signal light having a wavelength larger than the 1.60 μm band is a wavelength outside the optical amplification wavelength band.

On the other hand, from FIG. 9, 0.98 μm excitation EDF
In the case of A, the signal light in the 0.98 μm band is changed to 0.94 μm.
By using a wavelength smaller than the band or a wavelength larger than the 1.02 μm band, the loss in the optical amplification characteristic is reduced. That is, the signal light having a wavelength smaller than the 0.94 μm band or the signal light having a wavelength larger than the 1.02 μm band is a wavelength outside the optical amplification wavelength band.

From this, the signal light having the first wavelength is the signal light in the 1.50 μm band or the 1.60 μm band or the second wavelength as the first wavelength light used in the 0.98 μm pumped EDFA. By setting the wavelength light to pump light in the 0.94 μm band or 1.02 μm band, this signal light is not amplified by the pump light.

In the fourth embodiment, the above-mentioned wavelength light is used to constitute the second embodiment. As a result, in the case where the optical fiber 1 is a rare earth element-doped optical fiber such as EDF, and after connecting the optical fiber 1 and the optical fiber 2, the signal light having the first wavelength shown in FIG. Even if the light of the pumping light having the wavelength is input to the multiplexer 11 at the same time, the signal light of the first wavelength is not amplified by the pumping light of the second wavelength. From the above, by constructing the second embodiment using the wavelength light described in the fourth embodiment, the connection point
The loss of signal light at A can be converted.

[0063]

As described above, according to the present invention, the MF is obtained by using the first wavelength and the second wavelength having different wavelength bands.
Optical fibers of different D can be fusion spliced with low loss. Therefore, it is possible to realize an optical amplifier having good noise characteristics or high output signal light power.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of a first embodiment.

FIG. 2 is an explanatory diagram of loss with respect to heating time for each wavelength band.

FIG. 3 is a configuration diagram of a 0.98 μm excitation EDFA of the first embodiment.

FIG. 4 is a configuration diagram of an EDFA in which only a first wavelength light according to a second embodiment is input to a multiplexer.

FIG. 5 is a configuration diagram of an EDFA in which only the second wavelength light of the second embodiment is input to the multiplexer.

FIG. 6 is a configuration diagram of an EDFA in which only a first wavelength light of a third embodiment is input to a multiplexer.

FIG. 7 is a configuration diagram of an EDFA in which only the second wavelength light of the third embodiment is input to a multiplexer.

FIG. 8 is an explanatory diagram showing optical amplification characteristics in the 1.55 μm band.

FIG. 9 is an explanatory diagram showing optical amplification characteristics in a 0.98 μm band.

FIG. 10 is a configuration diagram of an optical fiber connection having different MFDs according to a conventional method.

FIG. 11 is a configuration diagram of an optical fiber connection with different MFDs using core expansion according to a conventional method.

FIG. 12 is a configuration diagram of a 1.48 μm excitation EDFA of a conventional method.

FIG. 13 is an explanatory diagram showing a configuration of an MFD.

[Explanation of symbols]

 1, 2 Optical fiber 11, 31, 41, 51, 61, 71 Multiplexer 15, 35 Splitter 16, 17 Optical power meter 62, 72 Optical filter

Claims (8)

[Claims] 1. An optical fiber 1 having a first MFD that transmits first wavelength light and second wavelength light having different wavelength bands.
And an optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the first MFD, the first wavelength light and the second wavelength light being provided at the output end of the optical fiber 2. An optical power meter 16 is connected to a splitter for splitting, and measures the output power of the first wavelength light split by the splitter, and an output power of the second wavelength light split by the splitter. By connecting the optical power meter 17 to be measured, connecting the optical fiber 1 and the optical fiber 2, and then heating the end face portion of the optical fiber 2, M
The output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which is changed by locally enlarging the FD and heating the end face portion of the optical fiber 2 is used as the optical power. The output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2 measured by the power meter 1 and changed by heating the end face portion of the optical fiber 2 is changed to the optical power. An optical fiber connection method characterized in that the heating is stopped when the loss in the first wavelength light and the loss in the second wavelength light reaches an arbitrarily set value measured by a meter 2. 2. An optical fiber 1 having a first MFD that transmits first wavelength light and second wavelength light having different wavelength bands.
And an optical fiber connecting method for connecting an optical fiber 2 having a second MFD larger than the first MFD, in which an output end of the optical fiber 2 is provided with a first wavelength light and a second wavelength light. An optical power meter 16 is connected to a splitter for splitting, and measures the output power of the first wavelength light split by the splitter, and an output power of the second wavelength light split by the splitter. By connecting the optical power meter 17 to be measured, connecting the optical fiber 1 and the optical fiber 2, and then heating the end face portion of the optical fiber 1, M
The output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2 which is changed by locally enlarging the FD and heating the end face portion of the optical fiber 1 is changed to the optical power. The output power of the second wavelength light, which is measured by the power meter 1 and changes by heating the end face portion of the optical fiber 1 and transmitted from the optical fiber 1 to the optical fiber 2, is the optical power. An optical fiber connection method characterized in that the heating is stopped when the loss in the first wavelength light and the loss in the second wavelength light reaches an arbitrarily set value measured by a meter 2. 3. An optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands.
And an optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the first MFD, the optical fiber 1 having the first wavelength before connecting the optical fiber 1 and the optical fiber 2. Only the optical fiber 1 is input to the optical fiber 1, the output power of the first wavelength light is measured at the output end of the optical fiber 1, the optical fiber 1 and the optical fiber 2 are connected, and then the optical fiber 2 is connected. By heating the end face part of
FD is locally enlarged, and the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating the end face portion of the optical fiber 2, is measured, The optical power meter 1 measures the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 2, and the optical fiber Output power of the first wavelength light measured at the output end of No. 1, loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 from the output power of the first wavelength light transmitted to the optical fiber 1 and the optical fiber 2
The loss of the first wavelength at the connection portion with is converted and obtained, and on the other hand, before connecting the optical fiber 1 and the optical fiber 2, only the light of the second wavelength is input to the optical fiber 1. By measuring the output power of the second wavelength light at the output end of the optical fiber 1, connecting the optical fiber 1 and the optical fiber 2, and then heating the end face portion of the optical fiber 2, M
The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by locally expanding the FD and heating the end face portion of the optical fiber 2, is measured, The optical power meter 2 measures the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 2, and the optical fiber 1 Output power of the second wavelength light measured at the output end of the optical fiber 2, loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 From the output power of the second wavelength light transmitted to the optical fiber 1 and the optical fiber 2
The loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is calculated, and the loss between the first wavelength light and the second wavelength light at the connecting portion between the optical fiber 1 and the optical fiber 2 is arbitrarily set. The optical fiber connection method according to claim 1, wherein the heating is stopped when the value is reached. 4. An optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands.
And an optical fiber connecting method for connecting an optical fiber 2 having a second MFD larger than the first MFD, wherein the first wavelength light is connected before connecting the optical fiber 1 and the optical fiber 2. Only the optical fiber 1 is input to the optical fiber 1, the output power of the first wavelength light is measured at the output end of the optical fiber 1, and the optical fiber 1 and the optical fiber 2 are connected to each other. By heating the end face part of
FD is locally enlarged, and the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating the end face portion of the optical fiber 1, is measured. The optical power meter 1 measures the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 1, and the optical fiber Output power of the first wavelength light measured at the output end of No. 1, loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 from the output power of the first wavelength light transmitted to the optical fiber 1 and the optical fiber 2
The loss of the first wavelength at the connection portion with is converted and obtained, and on the other hand, before connecting the optical fiber 1 and the optical fiber 2, only the light of the second wavelength is input to the optical fiber 1. By measuring the output power of the second wavelength light at the output end of the optical fiber 1, connecting the optical fiber 1 and the optical fiber 2, and then heating the end face portion of the optical fiber 1, M
The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which changes by locally expanding the FD and heating the end face portion of the optical fiber 1, is measured, The optical power meter 2 measures the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 1, and the optical fiber 1 Output power of the second wavelength light measured at the output end of the optical fiber 2, loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the optical fiber 2 From the output power of the second wavelength light transmitted to the optical fiber 1 and the optical fiber 2
The loss of the second wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is calculated, and the loss between the first wavelength light and the second wavelength light at the connecting portion between the optical fiber 1 and the optical fiber 2 is arbitrarily set. The optical fiber connection method according to claim 1, wherein the heating is stopped when the value is reached. 5. An optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands.
And an optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the first MFD, in which a first wavelength light is supplied before connecting the optical fiber 1 and the optical fiber 2. The second wavelength light and the optical fiber 1
And measuring the output power of the first wavelength light at the output end of the optical fiber 1 through an optical filter that removes the second wavelength light, and after connecting the optical fiber 1 and the optical fiber 2 to each other. , By heating the end face portion of the optical fiber 2,
FD is locally enlarged, and the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating the end face portion of the optical fiber 2, is measured, The optical power meter 1 measures the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 2, and the optical fiber Output power of the first wavelength light measured through the optical filter at the output end of No. 1, loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 From the output power of the light of the first wavelength transmitted to the optical fiber 2, the loss of the first wavelength at the connecting portion between the optical fiber 1 and the optical fiber 2 is converted and obtained. Before connecting the optical fiber 1 and the optical fiber 2, the first wavelength light and the second wavelength light are input to the optical fiber 1, and the output power of the second wavelength light is output at the output end of the optical fiber 1. Is measured through an optical filter that removes light of the first wavelength, and after connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 2, M
The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by locally expanding the FD and heating the end face portion of the optical fiber 2, is measured, The optical power meter 2 measures the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 2, and the optical fiber 1 Output power of the second wavelength light measured through an optical filter at the output end, loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the From the output power of the light of the second wavelength transmitted to the optical fiber 2, the loss of the second wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted to obtain the optical fiber 1 and the optical fiber. 2. The light according to claim 1, wherein the heating is stopped when the loss between the light of the first wavelength and the light of the second wavelength at the connection portion with the bar 2 reaches an arbitrarily set value. Fiber connection method. 6. An optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands.
And an optical fiber 2 having a second MFD larger than the first MFD, in the optical fiber connecting method, before connecting the optical fiber 1 and the optical fiber 2, a first wavelength light The second wavelength light and the optical fiber 1
And measuring the output power of the first wavelength light at the output end of the optical fiber 1 through an optical filter that removes the second wavelength light, and after connecting the optical fiber 1 and the optical fiber 2 to each other. , By heating the end face portion of the optical fiber 1,
FD is locally enlarged, and the loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, which is changed by heating the end face portion of the optical fiber 1, is measured. The optical power meter 1 measures the output power of the first wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 1. Output power of the first wavelength light measured through an optical filter at the output end, loss of the first wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the From the output power of the light of the first wavelength transmitted to the optical fiber 2, the loss of the first wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted and obtained. Before connecting the optical fiber 2 and the optical fiber 2, the first wavelength light and the second wavelength light are input to the optical fiber 1, and the output power of the second wavelength light is output at the output end of the optical fiber 1. , Through the optical filter that removes the light of the first wavelength, and after connecting the optical fiber 1 and the optical fiber 2, by heating the end face portion of the optical fiber 1,
The loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, which changes by locally expanding the FD and heating the end face portion of the optical fiber 1, is measured, The optical power meter 2 measures the output power of the second wavelength light transmitted from the optical fiber 1 to the optical fiber 2, which changes by heating the end face portion of the fiber 1, and the optical fiber 1 Output power of the second wavelength light measured through an optical filter at the output end, loss of the second wavelength light at the connection between the optical fiber 2 and the demultiplexer, and the optical fiber 1 to the From the output power of the light of the second wavelength transmitted to the optical fiber 2, the loss of the second wavelength at the connection between the optical fiber 1 and the optical fiber 2 is converted to obtain the optical fiber 1 and the optical fiber. 2. The light according to claim 1, wherein the heating is stopped when the loss between the light of the first wavelength and the light of the second wavelength at the connection portion with the bar 2 reaches an arbitrarily set value. Fiber connection method. 7. An optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands.
And an optical fiber connecting method for connecting an optical fiber 2 having a second MFD smaller than the first MFD, in the case of using a rare earth element-doped optical fiber having an optical amplification effect as the optical fiber 1, 3. The optical fiber splicing method according to claim 2, wherein the wavelength light of (1), the second wavelength of light, or any one of the wavelengths of light is a wavelength of light outside the optical amplification wavelength band. 8. An optical fiber 1 having a first MFD for transmitting a first wavelength light and a second wavelength light having different wavelength bands.
And an optical fiber 2 having a second MFD larger than the first MFD, in the optical fiber connecting method, when a rare earth element-doped optical fiber having an optical amplification action is used as the optical fiber 1, 3. The optical fiber splicing method according to claim 2, wherein the wavelength light of (1), the second wavelength of light, or any one of the wavelengths of light is a wavelength of light outside the optical amplification wavelength band.