JPH11133467A - Optical branching/inserting device and optical gate switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compact a wavelength light branching/inserting device. SOLUTION: Signal light of 1550 nm wavelength is inputted to an optical transmission line 110. In the case of passing the signal light of 1550 nm wavelength, the signal light is reflected by a variable reflectance mirror 50 and outputted to the line 110 again. In the case of branching the signal light, a part of the signal light inputted to the line 110 is outputted to an optical transmission line 121 connected to an optical branch 11 and then inputted and received by a light receiver 71. When a branch ratio for connecting the branch 11 to the receiving side is reduced, an optical loss by the branch 11 can be suppressed at the time of passing signal light through the circuit. In the case of inserting signal light, the reflection factor of the mirror 50 can be optionally changed from 100% to be complete reflection down to 0% to be a transmission state. When the mirror 50 is turned to the transmission state, signal light sent from the line 110 is not reflected, signal line of 1550 nm wavelength outputted from an optical transmitter 81 to an optical transmission line 120 is transmitted through the mirror 50 and outputted to the line 110.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical add / drop device used for optical communication or optical switching, and an optical gate switch suitable for use in the optical add / drop device.

[0002]

2. Description of the Related Art A wavelength multiplexing system for transmitting signal lights having different wavelengths in one fiber at a time enables a large-capacity optical transmission, and further provides a high gain represented by an EDFA (erbium-doped fiber amplifier). The emergence of high-power optical amplifiers has enabled long-distance, large-capacity optical transmission between fibers. In addition, when a signal is relay-amplified, the use of a drop-and-insert device that drops and inserts a signal at the relay station allows a denser network to be established. More and more demand is expected.

[0003] In particular, an optical add / drop multiplexer that converts a signal light into an electric signal and adds / drops the signal as it is without any notice is capable of reducing the size of a relay station and greatly contributing to cost reduction of communication. Are gathering. Currently, various types of node configurations have been proposed.
Further, in order to further reduce the size of the optical add / drop multiplexer, it is necessary to reduce the number of components and mount components with high density.

[0004] FIG. 8 shows a case where wavelength-division multiplexed light is demultiplexed in a node.
FIG. 2 is a configuration diagram illustrating a conventional wavelength division multiplexing optical add / drop device that performs processes of dropping, passing, and adding for each wavelength, and combines and outputs to a next node. 8, the wavelength division multiplexed light input via the optical transmission line 110 is demultiplexed for each wavelength by the optical demultiplexer 210, and the optical transmission lines 131 to 134 are respectively provided.
Are further multiplexed by the optical multiplexer 310 after passing through the optical gate switches 61 to 64 and output to the optical transmission line 120.

In order to perform optical branching within a node, an optical gate switch connected to the wavelength light to be branched among the optical gate switches 61 to 64 is turned off, and an optical branch 11 provided for each wavelength is set. To 14 and the corresponding optical branch among the optical receivers 71 to 74 and the corresponding wavelength light by the optical receiver. In addition, the passage is performed by the optical gate switches 61 to 61.
By turning on 64, the input wavelength light is output to the optical transmission line 120 as it is. In addition, when performing the insertion, the corresponding optical gate switch is turned off, and the optical transmitters 81 to 84 provided for each wavelength and the optical transmitters and optical branches among the optical branches 15 to 18 are connected. Then, the optical transmission line is connected to one of the optical transmission lines 131 to 134, and the output light of the corresponding optical transmitter is output to the optical transmission line 120 via the optical multiplexer 310.

[0008] In FIG. 8, since the main functions are the branching, passing, and insertion of light, the optical branching 1 for reception (branching) is performed.
1 to 14, optical gate switches 61 to 64 for passage / transmission (insertion) and optical branches 15 to 18 are required. Also,
Since the above function is required for each wavelength, the optical multiplexer / demultiplexer 210,
310 is required.

FIG. 9 is a block diagram showing a conventional wavelength add / drop multiplexer in which the functions of the optical demultiplexer and the multiplexer shown in FIG. In this configuration, the number of components for demultiplexing can be reduced by one, so that cost reduction and downsizing can be achieved. As the optical gate switches 61 to 64 in the configuration of FIG. 9, EDFs as shown in FIG.
An A gate switch is used. This EDFA gate switch is a low crosstalk and low loss optical switch, and can have a gain.

[0008] That is, in FIG.
The signal light input to 0 passes through the optical isolator 91 and is input to the EDF 41 excited by the excitation light source 31 and amplified. The amplified signal light is transmitted to the light reflection mirror 2
The light is reflected at 1 and input to the EDF 41 again and amplified,
The light is output to the optical transmission line 120 via the optical branch 11. Further, by using the folded configuration as shown in FIG. 9, operation with a higher extinction ratio and a lower drive current becomes possible.

[0009]

However, the optical add / drop multiplexer having the folded structure shown in FIG. 9 and the gate switch for the folded structure shown in FIG. 10 have the following problems.
First, when an optical add / drop circuit as shown in FIG. 9 is manufactured by using a folded gate switch, the optical branch for connecting to the optical receiver and the optical branch for connecting to the optical transmitter are each passed twice. Will be. From the viewpoint of preventing the S / N ratio from deteriorating, it is necessary that the entire wavelength optical add / drop is reduced in loss.

In the optical branch shown in FIG. 8, the insertion loss of the optical add / drop circuit can be reduced by reducing the branching ratio connected to the receiver, but in the optical branch shown in FIG. 9, the output optical power of the transmitter is reduced. Because of the balance between the optical add / drop multiplexer and the optical add / drop multiplexer of FIG. 8, the drop ratio connected to the transmitter cannot be reduced as in the optical add / drop multiplexer of FIG. Become.

Further, as a folded gate switch,
When an EDFA gate switch having a configuration as shown in FIG. 10 is used, it is necessary to provide an optical branch for inputting the excitation light source 31 to the EDF 41. However, providing such an optical branch increases the switch size and cost. Not only do
There are several problems such as causing light loss and reflection points.

An object of the present invention is to reduce the loss, reduce the size, and reduce the cost of an optical add / drop device of this kind and an optical gate switch used in the optical add / drop device in view of the above-mentioned problems in the prior art. That is.

[0013]

An optical add / drop circuit according to the present invention comprises: an optical transmission line; an optical branch connected to the optical transmission line;
An optical receiver connected to one of the optical branches and receiving the signal light from the optical transmission line, and a reflectance variable mirror connected to the other of the optical branches and capable of arbitrarily controlling the reflection and transmission of light; and An optical transmitter for transmitting signal light to the optical transmission line via a variable reflectance mirror.

In another embodiment of the optical add / drop circuit of the present invention, an optical transmission line and a first optical branch for splitting a signal light input to the optical transmission line and inputting the signal light to an optical receiver. A second optical branch that outputs an optical signal from an optical transmitter to the optical transmission line, and an optical gate that reflects the signal light input from the transmission line and sends it back to the optical transmission line or absorbs it again A switch, and as the optical gate switch, an impurity-doped fiber having one input / output connected to the optical transmission line, and connected to the other input / output of the impurity-doped fiber to reflect only the wavelength of the signal light. And a wavelength-selective reflection mirror that transmits the wavelength of the excitation light and an excitation light source connected to the wavelength-selection reflection mirror.

Further, the optical gate switch of the present invention comprises an optical transmission line, an impurity-doped fiber having one input / output connected to the optical transmission line, and a signal light connected to the other input / output of the impurity-doped fiber. And a pumping light source connected to the wavelength-selective reflecting mirror, the reflecting mirror being capable of reflecting only the wavelength and transmitting the wavelength of the pumping light.

The optical gate array according to the present invention is characterized in that at least two optical gate switches are mounted on the same substrate and integrated.

In the integrated optical add / drop circuit of the present invention, at least two of the optical add / drop circuits are mounted in parallel on the same substrate and integrated, and light input and output to the optical drop are provided. Are arranged in the same direction to perform high-density mounting.

Further, the wavelength division multiplexing optical add / drop multiplexer of the present invention has a function of demultiplexing wavelength-division multiplexed light input from an optical transmission line for each wavelength and a wavelength multiplexing of the demultiplexed light to an optical transmission line. An optical multiplexer / demultiplexer having a function of outputting, wavelength-division multiplexed light input from one of the optical transmission lines, output to the optical multiplexer / demultiplexer,
An optical circulator for inputting the wavelength multiplexed light output from the optical multiplexer / demultiplexer and outputting the multiplexed light to the other optical transmission line; and an optical circulator connected to the optical multiplexer / demultiplexer for transmitting light separated for each wavelength. A plurality of optical transmission lines and optical add / drop circuits respectively connected to the plurality of optical transmission lines are provided, and the optical add / drop circuit is used as the optical add / drop circuit.

In the present invention, it is not necessary to provide separate optical branches for the optical receiver and the optical transmitter by using a variable reflectivity mirror between the optical branch and the optical transmitter. Can be reduced. Switching between optical branching and insertion is performed by controlling the variable reflectance mirror to total reflection and transmission. Further, the optical gate switch used in another embodiment of the present invention uses a light splitter for inputting the excitation light source by attaching a reflection mirror having a wavelength selectivity that reflects only the signal light to the output port of the excitation light source. An EDFA gate switch with no folded configuration can be realized.

[0020]

FIG. 1 is a block diagram showing an embodiment of an optical add / drop circuit of the present invention. In FIG. 1, a signal light having a wavelength of 1550 nm is input to the optical transmission line 110. The passage, branching, and insertion of the optical add / drop circuit will be described.

Regarding the passage, the signal light of 1550 nm input to the optical transmission line 110 is reflected by the reflectivity variable mirror 50 and output to the optical transmission line 110 again. Regarding the branch, the signal light of 1550 nm input to the transmission line 110 is partially output to the optical transmission line 121 connected to the optical branch 11 and then input to the optical receiver 71 to be received. In the optical branch 11, the branch ratio connected to the receiving side can be reduced, so that when the signal light passes through the circuit, the optical loss due to the optical branch can be suppressed.

As for insertion, the variable reflectivity mirror 50 can freely change the reflectivity from 100% of the perfect reflection to 0% of the transmissive state. The signal light transmitted from the optical transmission line 110 is not reflected, and the signal light having a wavelength of 1550 nm output from the optical transmitter 81 to the optical transmission line 120 passes through the variable reflectance mirror 50 and passes through the optical transmission line 110. Is output to In this circuit configuration, the number of optical branches for insertion can be reduced, so that low loss can be realized.

FIG. 2 is a configuration diagram showing an embodiment of the optical gate switch of the present invention. In FIG. 2, the optical transmission line 1
10, a signal light having a wavelength of 1550 nm is input.
The signal light passes through the optical isolator 91 and is input to the EDF 41. The wavelength selective light reflecting mirror 25 represented by a fiber Bragg grating or the like can select a wavelength band to be reflected. The wavelength-selective light reflecting mirror 25 used here has a wavelength of 1
The excitation light of 480 nm is transmitted, and the wavelength of the signal light is 1550 n.
m has the characteristic of total reflection.

When the pumping light is input to the EDF 41, the signal light is optically amplified by the EDF 41, then is totally reflected by the wavelength-selective light reflecting mirror 25, and is again subjected to the ED.
The optical signal is amplified by F41 and is optically output to the optical transmission line 120 connected to the optical branch 11 (optical gate switch ON state). When no pumping light is input to the EDF 41, the signal light is absorbed by the EDF 41 and is not optically output (optical gate switch off state).

According to the present invention, it is possible to reduce the insertion loss, which is a problem in the case of using the optical branch, and further to reduce the optical branch which causes the reflection point. Further, the excitation light source and the light reflecting mirror can be easily integrated, and integration can be easily realized.

FIG. 3 is a block diagram showing an embodiment in which the optical gate switch of the present invention described in FIG. 2 is applied to an optical add / drop circuit. In FIG. 3, a signal light having a wavelength of 1550 nm is input from the optical transmission line 110 through the optical isolator 91. The operation of passing, dropping, and inserting signal light in the optical add / drop circuit of the present embodiment will be described below.

At the time of passage, the excitation light from the excitation light source 31 passes through the wavelength-selective light reflection mirror 25 and passes through the EDF 41.
Has been entered. 155 input to the optical transmission line 110
The signal light of 0 nm is transmitted through the isolator 91 to the EDF 4
1 and optically amplified by the EDF 41. The amplified signal light is totally reflected by the wavelength-selective light reflection mirror 25, is again optically amplified by the EDF 41, and is optically output to the optical transmission line 120 connected to the optical branch 11.

At the time of branching, the 1550 nm signal light input to the transmission line 110 is input to the optical receiver 71 connected to the optical branch 12 and received. In the optical branch 12, since the branch ratio connected to the receiving side can be reduced, the optical loss due to the optical branch 12 can be suppressed when the signal light passes through the circuit.

At the time of insertion, the pump light source 31 is in an inactive state, no pump light is input to the EDF 41, and the signal light input to the optical transmission line 110 is absorbed by the EDF 41. No light is output to the transmission line 120.
On the other hand, the signal light having a wavelength of 1550 nm output from the optical transmitter 81 is output to the optical transmission line 120 via the optical branch 13.

In the circuit configuration according to this embodiment, the number of optical branches for inserting the pump light can be reduced, so that a low loss can be realized. In other words, there is no insertion loss or reflection in the gate switch, which is a problem when optical branching is used. Further, the excitation light source and the light reflection mirror can be easily integrated, and integration can be realized.

FIG. 4 is a configuration diagram showing an embodiment in which the optical gate switch of the present invention described in FIG. 2 is integrated.
In FIG. 4, eight optical gate switches including an excitation light source 31, a wavelength-selective light reflecting mirror 25, an EDF 41, and an optical transmission line 100 are integrated in an EDFA gate array 300. As described above, what has conventionally been connected using the optical branching is reduced in the present invention by omitting the optical branching, so that a plurality of optical gate switches can be easily integrated and integrated. It becomes possible.

FIG. 5 shows an EDFA gate module 202 mounted on a communication device package 201 by mounting the EDFA gate array 300 described in FIG. The gate switch configuration according to the present invention makes it possible to form an array of optical gate switches, and a small EDFA
Since a gate array can be realized and the input / output ports in the folded configuration can be directed in the same direction, higher-density mounting can be realized.

FIG. 6 shows an embodiment in which a wavelength division multiplexing optical add / drop device is realized using the optical add / drop circuit of the present invention described in FIG. In FIG. 6, the optical transmission line 11
0 has wavelengths of 1548 nm, 1550 nm, 1552n
The signal light of m, 1554 nm is wavelength multiplexed and transmitted. These signal lights pass through an optical circulator 60 and are transmitted to an optical multiplexer / demultiplexer 41 represented by an arrayed waveguide diffraction grating.
0, which are different from each other.
Is output to In other words, each of the optical transmission lines 131 to 134 has only one wavelength of light.

Next, the operation of the wavelength division multiplexing optical add / drop device (passing, dropping and adding of wavelength light) will be described below.
Regarding the passage, the wavelength light input from the optical transmission line 110 is input to the optical demultiplexer / demultiplexer 410 via the circulator 60, and for example, 1548n output to the optical transmission line 131.
The signal light of m is reflected by the reflectivity variable mirror 50, output to the optical transmission line 131 again, and input to the optical demultiplexer / demultiplexer 410. Then, the signal light recombined by the optical demultiplexer 410 is output to the optical transmission line 121 via the circulator 60.

With respect to the branch, for example, the signal light of 1548 nm input to the transmission line 131 is partially output to the optical transmission line 135 connected to the optical branch 11, and then the optical receiver 71
Is input and received. In the optical branch 11, the branch ratio connected to the receiving side is set to be small, so that the optical loss due to the optical branch when the signal light passes through the circuit is suppressed to be small.

As for the insertion, the variable reflectance mirror 51 can freely change the reflectance from 100% of the complete reflection to 0% of the transmission state. The transmitted signal light is not reflected, and the signal light with a wavelength of 1548 nm output from the optical transmitter 81 passes through the reflectance variable mirror 51 and is output to the optical transmission line 131.

The signal lights of different wavelengths propagating through the other optical transmission lines 132 to 134 are also input to the optical multiplexer / demultiplexer 410 through the same configuration. And the optical multiplexer / demultiplexer 41
After being wavelength-multiplexed at 0, the signal is output to the optical transmission line 121 via the optical circulator 60.

In the circuit configuration of this embodiment, since the number of optical branches for insertion can be reduced, low loss can be realized.
In addition, the reduction in the number of components and the folded configuration enable high-density mounting, and the size of the device can be reduced.

FIG. 7 shows another embodiment of the present invention in which a wavelength division multiplexing optical add / drop multiplexer is configured by partially changing the optical add / drop circuit described in FIG. In FIG. 7, wavelengths of 1548 nm, 1550 nm, 1
Signal lights of 552 nm and 1554 nm are wavelength-multiplexed and transmitted. These signal lights are transmitted to the optical circulator 6.
0, which are input to an optical multiplexer / demultiplexer 410 represented by an arrayed waveguide diffraction grating, and are respectively different from the optical transmission lines 131.
To 134. That is, the optical transmission lines 131 to 1
There is only one wavelength of light in each of the 34.

The wavelength-selective light reflecting mirrors 25 to 28 typified by fiber Bragg gratings connected to the optical transmission lines 131 to 134 can select the wavelength band to be reflected. That is, these wavelength-selective light reflecting mirrors 25 to 28 have a characteristic that the excitation light having a wavelength of 1480 nm output from the excitation light source 31 is transmitted, and the signal light having a wavelength of 1548 nm to 1554 nm is totally reflected. ing.

Next, the operation (passage, dropping, and insertion of signal light) of this wavelength light add / drop device will be described with reference to 1548 nm.
This will be described using an optical add / drop circuit connected to the transmission line 131 to which the signal light is input.

At the time of passage, the excitation light from the excitation light source 31 passes through the wavelength-selective light reflection mirror 25 and passes through the EDF 41.
Has been entered. 154 input to the optical transmission line 131
The 8 nm signal light is optically amplified by the EDF 41, totally reflected by the wavelength-selective light reflection mirror 25, and then again transmitted to the EDF 4.
1 and is input to the optical multiplexer / demultiplexer 410.

At the time of splitting, the 1548 nm signal light output to the transmission line 131 is split by the optical splitter 11, input to the optical receiver 71, and received. In the optical branch 11, the branch ratio connected to the receiving side can be reduced, so that when the signal light passes through the circuit, the optical loss due to the optical branch 11 can be reduced.

At the time of insertion, the excitation light source 31 is inactive, and no excitation light is input to the EDF 41. Since the signal light input from the optical transmission line 131 is optically absorbed by the EDF 41, the signal light is not output to the optical transmission line 131. On the other hand, the signal light having a wavelength of 1548 nm output from the optical transmitter 81 is input to the optical transmission line 131 via the optical branch 15.

The signal light propagating through the other optical transmission lines 132 to 134 is also input to the optical demultiplexer 410 via the same configuration. Each signal light is wavelength-multiplexed by the optical multiplexer / demultiplexer 410, and then passes through the optical circulator 60 to the optical transmission line 121.
Is output to In the circuit configuration of this embodiment, there is no insertion loss in the optical gate switch, which is a problem when optical branching is used, and further, there is no reflection caused by such optical branching. Further, integration can be realized by integrating the excitation light source and the light reflection mirror.

In the present invention, the form of input / output to the optical add / drop circuit is not particularly limited. That is, it is possible to appropriately change the input and output to the same port according to the user's request, such as separating the input and output ports using an optical branch and an isolator or a circulator.

The reflectivity variable mirror 5 described with reference to FIG.
“0” can be substituted with any value as long as an equivalent function can be expected. For example, a reflection / transmission switch by switching an optical path can be used instead. Also,
The reflectivity is not limited to a variable variable in an analog manner, and an object in which only a reflectivity of 0 or 100% can be selected can be used instead. However, it is necessary to have a transmission function when the reflectance is 0%.

Also, the installation position of the optical branch for optical branching and insertion shown in FIG. 3 can be freely changed within a range that does not hinder the functions of branching, inserting and passing. Further, the number of integrated EDFA gate arrays shown in FIG. 4 is not limited to eight, but can be changed to an arbitrary value such as 16, 32 or the like. Regarding the mounting form, for example, ED
F in the same array, incorporating a reflection mirror inside the EDFA gate module, or PL
The mounting form can be appropriately changed as necessary, such as mounting all of them on the C board.

The number of multiplexed wavelengths in each optical transmission line shown in FIGS. 6 and 7 is not limited to four.
It can be changed to any number of wavelengths such as 6, 32, 64. The wavelength of the signal light is not limited to the 1550 nm band.
It can be set freely, such as in the 00 nm band. Also, the signal speed is not particularly limited, and is 2.5 Gbps, 5 Gbps.
It is possible to set a bit rate free such as s and 10 Gbps.

Although the optical demultiplexing, the multiplexing, and the multiplexer / demultiplexer have been described in this specification using an arrayed waveguide diffraction grating as an example, a wavelength router having a grating structure having the same function, As long as they have the same function, such as a wavelength MUX coupler, the same effects can be expected. Further, the optical demultiplexing represented by an arrayed waveguide diffraction grating, an optical multiplexing,
Since the optical multiplexer / demultiplexer has different insertion loss depending on each wavelength, an optical attenuator can be appropriately inserted into each waveguide to equalize the optical level. Further, it is also possible to control the gain of each EDFA gate, or control the reflectance of the light reflecting mirror described with reference to FIG. 6 to equalize the light level for each wavelength.

The configuration of the EDFA gate switch is particularly
The fiber is not limited to DF (erbium-doped fiber), but may be appropriately substituted as long as aluminum, tellurium, or the like is added to the fiber as an impurity, and the fiber is excited by a pump light source to perform optical amplification. Further, the wavelength of the excitation light is not limited to 1480 nm, but is 98%.
0 nm or the like can be substituted. The length of the impurity-doped fiber can also be set to any value depending on the doping amount, the intensity of the excitation light, the required extinction ratio as a switch, and the insertion loss. It is possible to

[0052]

According to the present invention, since the number of optical branches is reduced as much as possible, it is possible to realize an optical add / drop multiplexer and an optical gate switch which can realize low-loss and high-density mounting. It is possible to reduce the size of the add / drop device.

[0053]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an optical add / drop circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing an optical gate switch configuration according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an optical add / drop circuit according to one embodiment of the present invention;

FIG. 4 is a diagram showing an array configuration according to an embodiment of the present invention.

FIG. 5 is a diagram showing an array configuration according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an optical add / drop multiplexer according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of an optical add / drop multiplexer according to an embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a conventional optical add / drop multiplexer.

FIG. 9 is a diagram showing a configuration of a conventional optical add / drop multiplexer.

FIG. 10 is a diagram showing a configuration of a conventional optical gate switch.

[Explanation of symbols]

100, 110, 120, 121, 131-138
Optical transmission paths 11 to 18, 141 to 144 Optical branches 21 to 24 Optical reflection mirrors 25 to 28 Wavelength selective light reflection mirrors 31 to 34 Excitation light sources 41 to 44 EDF 50 to 54 Variable reflection mirrors 60 Optical circulators 61 to 64 Optical gates Switch 71-74 Optical receiver 81-84 Optical transmitter 91 Optical isolator 201 Communication package 202 EDFA gate module 300 EDFA gate array 210 Optical demultiplexer 310 Optical multiplexer 410 Optical multiplexer / demultiplexer

Claims (8)

[Claims] 1. An optical transmission line, an optical branch connected to the optical transmission line, an optical receiver connected to one of the optical branches and receiving signal light from the optical transmission line, and the optical branch A variable reflectance mirror that can arbitrarily control the reflection and transmission of light, and an optical transmitter that transmits signal light to the optical transmission path via the variable reflectance mirror. Optical add / drop circuit. 2. The optical add / drop circuit according to claim 1, wherein a plurality of the optical add / drop circuits are mounted on the same substrate in parallel. 3. An optical multiplexer / demultiplexer having a function of demultiplexing wavelength-division multiplexed light input from an optical transmission line for each wavelength and a function of wavelength-multiplexing the demultiplexed light and outputting the resultant to the optical transmission line. And outputs the wavelength multiplexed light input from one optical transmission line to the optical multiplexer / demultiplexer, inputs the wavelength multiplexed light output from the optical multiplexer / demultiplexer, and outputs the wavelength multiplexed light to the other optical transmission line. An optical circulator, a plurality of optical transmission lines connected to the optical multiplexer / demultiplexer for transmitting light separated for each wavelength, and an optical add / drop circuit connected to the plurality of optical transmission lines, respectively. A wavelength division multiplexing optical add / drop device, comprising: the optical add / drop circuit according to claim 1 or 2 as the optical drop / add circuit. 4. An optical transmission line, an impurity-doped fiber having one input / output connected to the optical transmission line, and connected to the other input / output of the impurity-doped fiber, reflecting only the wavelength of the signal light; An optical gate switch comprising: a wavelength-selective reflection mirror that transmits a wavelength of excitation light; and an excitation light source connected to the wavelength-selection reflection mirror. 5. An optical gate switch array, wherein a plurality of optical gate switches according to claim 4 are mounted in parallel on the same substrate. 6. An optical transmission line, a first optical branch for splitting a signal light input to the optical transmission line and inputting the split signal light to an optical receiver.
A second optical branch for outputting an optical signal from an optical transmitter to the optical transmission line, and an optical gate switch for reflecting the signal light input from the transmission line and transmitting or absorbing the signal light to the optical transmission line again An optical add / drop circuit comprising: the optical gate switch according to claim 4 as the optical gate switch. 7. An optical add / drop multiplexer circuit according to claim 6, wherein a plurality of the optical add / drop multiplexer circuits are mounted on the same substrate in parallel. 8. An optical multiplexer / demultiplexer having a function of demultiplexing wavelength-division multiplexed light input from an optical transmission line for each wavelength and a function of wavelength-multiplexing the demultiplexed light and outputting it to the optical transmission line. And outputs the wavelength multiplexed light input from one optical transmission line to the optical multiplexer / demultiplexer, inputs the wavelength multiplexed light output from the optical multiplexer / demultiplexer, and outputs the wavelength multiplexed light to the other optical transmission line. An optical circulator, a plurality of optical transmission lines connected to the optical multiplexer / demultiplexer for transmitting light separated for each wavelength, and an optical add / drop circuit connected to the plurality of optical transmission lines, respectively. A wavelength division multiplexing optical add / drop device, comprising: the optical add / drop circuit of claim 6 or 7 as the optical drop / add circuit.