JPH07245436A - Two wavelength band amplifier and multiple wavelength transmission apparatus - Google Patents

Abstract

PURPOSE:To provide a two wavelength band amplifier capable of transmitting two optical signals of different wavelength bands a long distance by a simple structure, and capable of diminishing the influence of the crosstalk between the two optical signals extremely. CONSTITUTION:Concerning a two wavelength band light amplifier which receives two optical signals of different wavelength bands at its input end 23 as inputs, separates the two signals and amplifies them respectively, and combines these waves after that and outputs it from an output end 28, the input and output ends 23 and 28 are connected to one side of a main optical branching fitter 20, and to each the- other-side wave separating end 20ab, 20bb of the main optical branching filter 20, subsidiary light wave separator 21 and 22 and light-amplifying rare-earth doped optical fibers 26 nd 27 are successively connected respectively to form a light amplifier. And the emitting ends of the rare-earth doped optical fibers 26 and 27 are connected so as to return the separated optical signals amplified by the light-amplifying rare-earth doped optical fibers 26 and 27 of respective light amplifiers, to the other side of the main optical branching filter 20 through subsidiary light wave separators 22(21) being on the opposite sides respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier for amplifying an optical signal and a wavelength division multiplexing transmission device using the same, and more particularly to a dual wavelength band amplifier for amplifying two optical signals used in the wavelength division multiplexing transmission device and having different wavelengths. And a wavelength division multiplexing transmission apparatus using the same.

[0002]

2. Description of the Related Art Attention has been paid to a wavelength division multiplex transmission apparatus which connects two terminal devices with one optical fiber and propagates optical signals of two different wavelengths.

FIG. 6 is a schematic diagram of a conventional wavelength division multiplexing transmission apparatus.

As shown in FIG. 6, the two terminal devices A and B are connected by one optical fiber 1. An optical signal having a wavelength of 1.3 μm is transmitted from the light source 2 on the terminal device A side, which includes the light source (semiconductor laser) 2, the light receiver 3 and the optical demultiplexer 4, to the terminal device B side via the optical fiber 1. In the terminal device B including the light source (semiconductor laser) 5, the light receiver 6 and the optical demultiplexer 7, the optical signal from the light source 2 on the terminal device A side passes through the optical demultiplexer 7 and is received by the light receiver 6. To be done. On the contrary, from the terminal device B side, an optical signal having a wavelength of 1.55 μm is demultiplexed by the optical demultiplexer 7 from the light source 5, transmitted to the terminal device A side through the optical fiber 1, and then demultiplexed by the optical demultiplexer 4. The light is demultiplexed and received by the light receiver 3.

By the way, the device shown in FIG. 6 has a transmission distance limitation which depends on the losses of the optical demultiplexers 4 and 7 and the optical fiber 1, the outputs of the light sources 2 and 5, and the light receiving sensitivities of the light receiving devices 3 and 6.
The effect of crosstalk becomes extremely large. As a device for reducing the influence of crosstalk and solving the transmission distance limitation problem, a device for inserting an optical fiber amplifier as shown in FIG. 7 in the middle of a transmission line has been proposed.

In FIG. 7, a system C for transmitting an optical signal having a wavelength of 1.3 μm and a system D for transmitting an optical signal having a wavelength of 1.55 μm are separately provided, and an optical system is provided in the middle of each of the systems C and D. A Pr (praseodymium) -doped optical fiber 8 and an Er (erbium) -doped optical fiber 9 for a fiber amplifier are inserted. Pumping semiconductor laser 10 on optical fiber 8
The pumping light from is injected through the optical demultiplexer to be excited. Similarly, the pumping light from the pumping semiconductor laser 12 is injected into the optical fiber 9 through the optical demultiplexer 13 to be pumped. When an optical signal with a wavelength of 1.3 μm is generated by the light source 14, the optical signal passes through the optical demultiplexer 11 and is amplified by the Pr-doped optical fiber 8, passes through the optical demultiplexer 15, and is received by the photodetector 16. It Light source 17 has wavelength of 1.55
When a μm optical signal is generated, the optical signal passes through the optical demultiplexer 13 and is amplified by the Er-doped optical fiber 9, and the optical demultiplexer 18
Is received by the light receiver 19. Optical demultiplexer 1
Reference numerals 5 and 18 are for removing the residual components of the excitation light that could not contribute to the amplification.

[0007]

However, if the device shown in FIG. 7 is realized, the terminal device A
Two optical fibers must be installed side by side between _C (A _D ) and B _C (B _D ), which increases the cost. Especially in this device, the optical fiber 8 (9) and the pumping light source 10 (12)
By inserting an optical amplifier composed of the optical demultiplexer 15 (18), the terminal device A _C (A _D ) and the terminal device B _C (B
_Since the distance to _D ) becomes very long, arranging the optical fibers in parallel will further increase the cost.

Therefore, an object of the present invention is to solve the above-mentioned problems, to transmit optical signals in two different wavelength bands over a long distance with a simple structure, and to reduce the influence of crosstalk between the two optical signals. It is an object of the present invention to provide a two-wavelength band amplifier having a very small number and a wavelength division multiplexing transmission apparatus using the same.

[0009]

In order to achieve the above object, in a dual wavelength band amplifier of the present invention, a main optical demultiplexer and a sub optical demultiplexer have a passing side through which an optical signal of one wavelength band passes. A two-input, two-output directional coupler type optical demultiplexer having an optical waveguide and a demultiplexing-side optical waveguide through which an optical signal in the other wavelength band passes, and is used as a pass-side optical waveguide of the main optical demultiplexer. The pass-side optical waveguide of the first sub optical demultiplexer is connected to the second demultiplexing side optical waveguide of the main optical demultiplexer.
And the rare earth-doped optical fiber of the first sub-optical demultiplexer is connected to the optical waveguides of both the sub-optical demultiplexers. Is connected to the passage side optical waveguide of the second sub optical demultiplexer, and the emission end of the rare earth-doped optical fiber of the second sub optical demultiplexer is connected to the passage side optical waveguide of the first sub optical demultiplexer. It is connected to the waveguide.

The two-wavelength band amplifier according to the present invention comprises the first and second amplifiers.
The excitation light source may be connected to another optical waveguide of the sub optical demultiplexer.

In the two-wavelength band amplifier of the present invention, one of the two optical signals has a wavelength of 1.3 μm and the other has a wavelength of 1.
In the 55 μm band, the first rare earth-doped optical fiber may be a praseodymium-doped optical fiber, and the second rare earth-doped optical fiber may be an erbium-doped optical fiber.

In the dual wavelength band amplifier of the present invention, the input and output ends of the main optical demultiplexer may be inserted in the middle of an optical fiber for bidirectional communication.

In the dual wavelength band amplifier of the present invention, the input and output ends of the main optical demultiplexer may be inserted in the middle of an optical fiber for wavelength division multiplexing communication.

The two-wavelength band amplifier of the present invention inputs two optical signals having different wavelength bands to the input terminal, demultiplexes the two signals and amplifies them respectively, and then multiplexes these signals and outputs them. In the two-wavelength band optical amplifier that outputs from the, the input / output terminal is connected to one side of the main optical demultiplexer, and the sub optical demultiplexer is connected to each demultiplexing terminal on the other side of the main optical demultiplexer. And a rare-earth-doped optical fiber for optical amplification are sequentially connected to form an optical amplifier, and the demultiplexed optical signals amplified by the rare-earth-doped optical fiber for optical amplification of the respective optical amplifiers are sub-optical demultiplexers on opposite sides. The emission end of the rare earth-doped optical fiber is connected so as to be returned to the other side of the main optical demultiplexer via.

In the two-wavelength band amplifier of the present invention, the main optical demultiplexer and the sub optical demultiplexer pass the optical waveguide of the passing side through which the optical signal of one wavelength band passes and the optical signal of the other wavelength band pass. A two-input two-output directional coupler type optical demultiplexer having a demultiplexing side optical waveguide, and a passing side optical waveguide of the first sub optical demultiplexer in a passing side optical waveguide of the main optical demultiplexer. However, the optical waveguides of the main optical demultiplexer are connected to the optical waveguides of the second sub optical demultiplexer, and the optical waveguides of the sub optical demultiplexers have rare earth doped optical fibers. And the emission end of the rare-earth-doped optical fiber of the first sub-optical demultiplexer is connected to the passage-side optical waveguide of the second sub-optical demultiplexer, and the rare-earth-doped optical fiber of the second sub-optical demultiplexer is connected. May be connected to the passage side optical waveguide of the first sub optical demultiplexer.

The two-wavelength band amplifier of the present invention comprises the first and second amplifiers.
The excitation light source may be connected to another optical waveguide of the sub optical demultiplexer.

In the dual wavelength band amplifier of the present invention, one of the two optical signals has a wavelength of 1.3 μm and the other has a wavelength of 1.
In the 55 μm band, the first rare earth-doped optical fiber may be a praseodymium-doped optical fiber, and the second rare earth-doped optical fiber may be an erbium-doped optical fiber.

In the dual wavelength band amplifier of the present invention, the input and output ends of the main optical demultiplexer may be inserted in the middle of an optical fiber for bidirectional communication.

In the dual wavelength band amplifier of the present invention, the input and output ends of the main optical demultiplexer may be inserted in the middle of an optical fiber for wavelength multiplexing communication.

A wavelength division multiplex transmission device using a two-wavelength band amplifier of the present invention inputs two optical signals having different wavelength bands to an input end, demultiplexes the two signals and amplifies them respectively. Two-wavelength band optical amplifier that multiplexes and outputs from the output end, and an optical fiber and a different wavelength band at the input end
It is provided with a terminal connected via an optical demultiplexer for multiplexing and demultiplexing two optical signals, and a terminal connected to the output end via an optical fiber and an optical demultiplexer.

In the wavelength division multiplex transmission apparatus using the two-wavelength band amplifier of the present invention, the terminal on the input end side is composed of two optical transmitters which respectively generate two optical signals having different wavelength bands, and the terminal on the output end side. The terminal may be composed of two optical transmitters that respectively receive two optical signals having different wavelength bands.

In the wavelength division multiplexing transmission apparatus using the dual wavelength band amplifier of the present invention, the terminal on the input end side receives the optical transmitter for generating the optical signal of one wavelength band and the optical signal of the other wavelength band. The terminal on the output end side may include an optical receiver and an optical transmitter that generates an optical signal in the other wavelength band and an optical receiver that receives an optical signal in one wavelength band.

[0023]

According to the above structure, two optical signals having different wavelength bands input to the main optical demultiplexer are independently amplified in the optical amplification rare earth-doped optical fiber connected to the sub optical demultiplexer. After that, each main optical demultiplexer functions as two optical demultiplexers because it is returned to the main optical demultiplexer via the sub optical demultiplexers on the opposite sides and output. By reducing the number of parts of the optical demultiplexer by that amount, the cost and the loss are reduced, and the spectral reception signal is increased.

If the two-wavelength band optical amplifier is inserted into an optical fiber connecting two terminal devices, unidirectional or bidirectional multiplex communication becomes possible. Since the optical signal in the desired wavelength band input to each optical receiver is amplified to a sufficient size, the optical signal in the undesired wavelength band leaking from the optical transmitter side is negligibly small, Even an optical demultiplexer with a small isolation can obtain sufficient crosstalk.

[0025]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of an embodiment of a dual wavelength band amplifier according to the present invention. In the present embodiment, description will be made on the case of amplifying an optical signal of two wavelength bands of an optical signal having a wavelength λ _S1 of 1.3 μm and an optical signal having a wavelength λ _S2 of 1.55 μm.

Each of 20 to 22 has a two-input, two-output directivity having a passage-side optical waveguide through which an optical signal in one wavelength band passes and a demultiplexing-side optical waveguide through which an optical signal in the other wavelength band passes. A coupler type optical demultiplexer, for example, Imoto et al .: “Waveguide type optical demultiplexer / demultiplexer”, Institute of Electronics, Information and Communication Engineers, Optical Quantum Electronics Research Group OQE87-7, pp. 47-pp.
53, April 20, 1987, can be formed by the method described in detail.

The main optical demultiplexer 20 includes a passage side optical waveguide 20a.
The wavelength λ _{S1 is} added to the demultiplexing end 20aa on one side (the left side in the figure).
When the optical signal of wavelength λ _S2 and the optical signal of wavelength λ _S2 are input,
The optical signal of _S1 is output from the demultiplexing end 20ab on the other side of the passing side optical waveguide 20a, and the optical signal of the wavelength λ _S2 passes through the demultiplexing side optical waveguide 20b from the middle (proximity portion) of the other side. The output is made from the demultiplexing end 20bb. The demultiplexing end 20 on one side of the passage-side optical waveguide 20a of the main optical demultiplexer 20
aa is extended, and optical signals of wavelength λ _S1 and wavelength λ _S2 are input to the input end 23 thereof.

The demultiplexing end 20ab on the other side of the passing side optical waveguide 20a of the main optical demultiplexer 20 is a demultiplexing end 21aa on one side of the passing side optical waveguide 21a of the first sub optical demultiplexer 21. It is connected to the. At the demultiplexing end 21ba on one side of the demultiplexing side optical waveguide 21b of the first sub optical demultiplexer 21, the wavelength λ
Excitation light source 2 for generating _P1 (1.017 μm) excitation light
4 is connected. The first sub optical demultiplexer 21 is a demultiplexing end (left side in the figure) 21a on one side of the passage side optical waveguide 21a.
When the optical signal of wavelength λ _{S1 and} the optical signal of wavelength λ _S2 are input to a, the optical signal of wavelength λ _S1 is output from the demultiplexing end 21bb on the other side of the demultiplexing side optical waveguide 21b and the wavelength λ _S2 Is output from the demultiplexing end 21ab on the other side of the passing side optical waveguide 21a.

The demultiplexing end 20bb on the other side of the demultiplexing side optical waveguide 20b of the main optical demultiplexer 20 is a demultiplexing end 22aa on one side of the passing side optical waveguide 22a of the second sub optical demultiplexer 22. It is connected to the. Demultiplexing side optical waveguide 2 of the second sub optical demultiplexer 22
2b has a wavelength λ _P2 (0.
An excitation light source 25 for generating excitation light of 98 μm) is connected. The second sub optical demultiplexer 22 has the same function as the main optical demultiplexer 20.

Demultiplexing side optical waveguide 2 of the first sub optical demultiplexer 21
1b and the demultiplexing end 21bb on the other side of the passing side optical waveguide 22a of the second sub optical demultiplexer 22.
b is connected by a Pr (praseodymium) -doped optical fiber 26, and the demultiplexing end 21ab on the other side of the passage side optical waveguide 21a of the first sub optical demultiplexer 21 and the second sub optical demultiplexer 22 are connected. The demultiplexing side optical waveguide 22b is connected to the demultiplexing end 22bb on the other side by an Er (erbium) -doped optical fiber 27.

The demultiplexing end 20ba on one side of the demultiplexing side optical waveguide 20b of the main optical demultiplexer 20 is extended, and the optical signal of the amplified wavelength λ _S1 and the amplified wavelength are output from the output end 28 thereof. The optical signal of λ _S2 is output. The main optical demultiplexer 20, the sub optical demultiplexers 21 and 22, the pumping light sources 24 and 25, the Pr-doped optical fiber 26, and the Er-doped optical fiber 27 constitute a two-wavelength band optical amplifier 30. The pumping light source 24, the sub optical demultiplexer 21 and the Pr-doped optical fiber 26 constitute an optical amplifier, and the pumping light source 25, the sub optical demultiplexer 22 and the Er-doped optical fiber 27 constitute an optical amplifier.

Next, the operation of the embodiment will be described.

When the optical signal of wavelength λ _{S1 and} the optical signal of wavelength λ _S2 are input to the input end 23, the optical signal of wavelength λ _S1 passes through the passage side optical waveguide 20a of the main optical demultiplexer 20, It is input to the demultiplexing end 21aa on one side of the passing side optical waveguide 21a of the first sub optical demultiplexer 21. The optical signal of wavelength λ _S1 is demultiplexed and is transmitted through the Pr-doped optical fiber 26 from the demultiplexing end 21bb on the other side of the demultiplexing side optical waveguide 21b. The demultiplexing end 21 on one side of the demultiplexing side optical waveguide 21b of the first sub demultiplexer 21.
Excitation light of wavelength λ _P1 is input to ba from the excitation light source 24. The pumping light of the wavelength λ _P1 passes through the demultiplexing side optical waveguide 21b of the first sub optical demultiplexer 21 as it is and is input into the Pr-doped optical fiber 26. The optical signal having the wavelength λ _S1 input into the Pr-doped optical fiber 26 is amplified by the pumping light having the wavelength λ _P1 , and the amplified optical signal is passed to the passing side optical waveguide 22a of the second sub optical demultiplexer 22 and Input from the demultiplexing end 22ab of the main optical demultiplexer 20 and the other demultiplexing end 20 of the demultiplexing side optical waveguide 20b of the main optical demultiplexer 20.
Input from bb, passes through the demultiplexing side optical waveguide 20b as it is, and is output from the output end 28.

On the other hand, the optical signal of wavelength λ _S2 is sent to the main optical demultiplexer 20.
From the demultiplexing end 20bb on the other side of the demultiplexing side optical waveguide 20b to the passage side optical waveguide 2 of the second sub optical demultiplexer 22.
It is input to the demultiplexing end 22aa on one side of 2a. Excitation light of wavelength λ _P2 is input from the excitation light source 25 to the demultiplexing end 22ba on one side of the demultiplexing side optical waveguide 22b of the second sub demultiplexer 22. The pumping light having the wavelength λ _P2 is supplied to the second optical sub demultiplexer 22.
The light is passed through the demultiplexing side optical waveguide 22b as it is and input to the Er-doped optical fiber 27. The optical signal of wavelength λ _S2 input into the Er-doped optical fiber 27 is amplified by the pumping light of wavelength λ _P2 , and the amplified optical signal is passed to the passage side optical waveguide 21a of the first sub optical demultiplexer 21 and Is input to the demultiplexing end 21ab on the side of, and is passed through the passing side optical waveguide 21a as it is and is input into the passing side optical waveguide 20a of the main optical demultiplexer 20. It is output from the output end 28 together with the amplified optical signal of the wavelength λ _S1 which enters the waveguide 20b.

In the above, according to the present embodiment, two optical signals input to the main optical demultiplexer 20 having different wavelength bands are added to the optical auxiliary demultiplexers 21 and 22, respectively, to add rare earth for optical amplification. After being independently amplified by the optical fibers 26 and 27, they are returned to the main optical demultiplexer 20 via the sub optical demultiplexers 21 and 22 on the opposite sides to be output, so that one main optical demultiplexer is provided. Bowl 2
Since 0 functions as two optical demultiplexers, the configuration is simplified and the number of optical demultiplexer parts is reduced by that much, so that cost and loss are reduced, and the optical reception signal is reduced by that amount. Grows larger.

In this embodiment, the main optical demultiplexer and the sub optical demultiplexer have been described as having a waveguide type structure, but the present invention is not limited to this, and a fiber type structure or an interference film filter and a lens are combined. It may be an individual component combination structure. Also,
The wavelength λ _{S1 of the} optical signal is 1.28 μm in addition to 1.3 μm.
At least one wavelength in the wavelength band of 1.34 μm can be used. Furthermore, the wavelength λ _S2 of the optical signal is 1.
Other than 55 μm, at least one wavelength in the wavelength band of 1.53 μm to 1.57 μm can be used. The wavelength λ _P2 of the excitation light source is 0.88 μm in addition to 0.98 μm, 0.8
The μm band may be used.

FIG. 2 is a diagram showing the concept of a bidirectional wavelength division multiplexing transmission apparatus using the dual wavelength band optical amplifier shown in FIG.

Reference numeral 31 denotes a semiconductor laser which generates an optical signal having a wavelength of 1.3 μm, 32 denotes a photodetector (photodiode) for the optical signal having a wavelength of 1.55 μm, and 33 denotes an optical signal having a wavelength of 1.3 μm. An optical demultiplexer for demultiplexing an optical signal of 1.55 μm, which includes a semiconductor laser 31 and a photodetector 32.
The optical demultiplexer 33 constitutes a terminal 34.

Reference numeral 35 denotes a semiconductor laser which generates an optical signal having a wavelength of 1.55 μm, 36 denotes a photodetector (photodiode) for an optical signal having a wavelength of 1.3 μm, and 37 denotes an optical signal having a wavelength of 1.55 μm. It is an optical demultiplexer that demultiplexes an optical signal of 1.3 μm, and the semiconductor laser 35, the light receiver 36, and the optical demultiplexer 37 constitute a terminal 38.

Pass-side optical waveguide 3 of both optical demultiplexers 33 and 37
Optical fibers 39 and 40 are connected to 3a and 37a, respectively, and input / output ends 23 and 2 of the two-wavelength band optical amplifier 30 are connected.
8 are connected respectively.

That is, the input and output ends of the main optical demultiplexer 20 of the two-wavelength band optical amplifier 30 are inserted in the optical fibers 39 and 40 for bidirectional communication.

In such a transmission device, when an optical signal is generated on the side of the terminal 34 from a semiconductor laser having a wavelength of 1.3 μm, the optical signal passes through the optical demultiplexer 33 and is transmitted through the optical fiber 39 to generate two wavelengths. After being amplified by the optical amplifier 30, the light is transmitted through the optical fiber 40, passes through the optical demultiplexer 37, and is received by the light receiver 36.

On the other hand, when an optical signal is generated from the semiconductor laser 35 having a wavelength of 1.55 μm on the side of the terminal 38, the optical signal is demultiplexed by the optical demultiplexer 37 and transmitted through the optical fiber 40, and the two wavelength band optical amplifier. After being amplified by 30, the signal is transmitted through the optical fiber 39, demultiplexed by the optical demultiplexer 33, and received by the photodetector 32, whereby bidirectional communication is performed. Since the 2-wavelength band optical amplifier 30 can obtain a high gain of about 20 dB to 40 dB, long-distance transmission can be performed in both of the two wavelength bands.

FIG. 3 shows another embodiment of the embodiment shown in FIG.

The difference from the embodiment shown in FIG. 2 is that an optical isolator is inserted between the optical fiber and the semiconductor laser and the light receiver.

With this configuration, the optical isolator 41 removes the reflected return light to the semiconductor laser 31, and the optical isolator 42 removes the reflected return light to the semiconductor laser 35.
The oscillation of 35 is stabilized, and good bidirectional communication can be performed.

FIG. 4 is a diagram showing the concept of a wavelength division multiplexing transmission apparatus using the dual wavelength band amplifier shown in FIG.

Reference numeral 43 denotes a semiconductor laser 31 for generating an optical signal having a wavelength of 1.3 μm, a semiconductor laser 35 for generating an optical signal having a wavelength of 1.55 μm, and an optical signal having a wavelength of 1.3 μm, and a light having a wavelength of 1.55 μm. Optical demultiplexer 3 for demultiplexing signals
3 is a terminal. Reference numeral 44 denotes an optical isolator 45, an optical demultiplexer 37 for passing an optical signal of wavelength 1.3 μm and demultiplexing an optical signal of wavelength 1.55 μm, a light receiver 36 for wavelength 1.3 μm, and a light receiver for wavelength 1.55 μm. This is a terminal including a light receiver 32.

When both semiconductor lasers 31 and 35 are operated on the side of the terminal 34, the optical signals from both semiconductor lasers 31 and 35 are combined by the optical demultiplexer 33 and transmitted together in the optical fiber 39. After being independently amplified by the wavelength band optical amplifier 30, they are combined, transmitted through the optical fiber 40, transmitted through the optical isolator, and demultiplexed by the optical demultiplexer 37 to receive an optical signal of wavelength 1.3 μm. The light is received by the device 36 and the wavelength 1.
An optical signal of 55 μm is received by the light receiver 32.

FIG. 5 is a conceptual diagram of another embodiment of FIG.

The difference from the embodiment shown in FIG. 4 is that the optical isolator 4 is provided between the optical demultiplexer 33 and the dual wavelength band amplifier 30.
6 is inserted.

With this structure, fluctuations in the wavelengths and outputs of the semiconductor lasers 31 and 35 due to reflected return light can be prevented, and good multiplex communication can be performed.

[0054]

In summary, according to the present invention, the following excellent effects are exhibited.

(1) Since one main optical demultiplexer functions as two optical demultiplexers, the structure is simple.

(2) By individually amplifying the optical signals in the two wavelength bands transmitted in one transmission line to obtain a large output optical signal and then combining them to transmit in one transmission line, Distance transmission can be performed.

(3) It is possible to realize a dual wavelength band amplifier in which the influence of crosstalk between two optical signals is extremely small.

(4) Since it can be inserted into an optical fiber connecting two terminals, unidirectional communication or bidirectional communication can be performed.

(5) Since it can be inserted into an optical fiber connecting terminals capable of transmitting and receiving optical signals of a plurality of wavelengths,
Multiplex communication can be performed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an embodiment of a dual wavelength band amplifier of the present invention.

FIG. 2 is a diagram showing the concept of a bidirectional wavelength division multiplexing transmission apparatus using the dual wavelength band optical amplifier shown in FIG.

FIG. 3 is another embodiment of the embodiment shown in FIG.

FIG. 4 is a diagram showing a concept of a wavelength division multiplexing transmission device using the dual wavelength band amplifier shown in FIG.

5 is a conceptual diagram of another embodiment of FIG. 4. FIG.

FIG. 6 is a schematic diagram of a conventional wavelength division multiplexing transmission device.

FIG. 7 is a schematic diagram of a conventional wavelength division multiplexing transmission device.

[Explanation of symbols]

20 Main Optical Demultiplexer 21 and 22 Sub Optical Demultiplexer 23 Input End 26 Rare Earth Doped Optical Fiber for Optical Amplification (Pr Doped Optical Fiber) 27 Rare Earth Doped Optical Fiber for Optical Amplification (Er Doped Optical Fiber) 28 Output End

Claims (9)

[Claims] 1. A two-wavelength band optical signal which inputs two optical signals having different wavelength bands to an input end, demultiplexes the two signals, amplifies the two signals respectively, and then multiplexes them to output from an output end. In the amplifier, the input / output terminal is connected to one side of the main optical demultiplexer, and the sub-optical demultiplexer and the rare earth for optical amplification are respectively connected to the demultiplexing terminals on the other side of the main optical demultiplexer. Optical fibers are sequentially connected to form an optical amplifier, and the demultiplexed optical signals amplified by the rare-earth doped optical fibers for optical amplification of each optical amplifier are demultiplexed by the main optical demultiplexers via the sub optical demultiplexers on the opposite side. A two-wavelength band amplifier characterized in that an output end of a rare earth-doped optical fiber is connected so as to return to the other side of the wave device. 2. A main optical demultiplexer and a sub optical demultiplexer are provided with a pass-side optical waveguide through which an optical signal in one wavelength band passes and a demultiplexing-side optical waveguide through which an optical signal in the other wavelength band passes. Have 2 inputs 2
The output side directional coupler type optical demultiplexer is used, and the passing side optical waveguide of the first optical demultiplexer is connected to the passing side optical waveguide of the main optical demultiplexer. The pass-side optical waveguides of the second sub optical demultiplexers are connected to the optical waveguides, and the rare earth-doped optical fibers are connected to the optical waveguides of the sub optical demultiplexers. The emission end of the rare-earth-doped optical fiber is connected to the passage-side optical waveguide of the second sub-optical demultiplexer, and the emission end of the rare-earth-doped optical fiber of the second sub-optical demultiplexer is the first
2. The dual wavelength band amplifier according to claim 1, which is connected to the pass-side optical waveguide of the sub optical demultiplexer. 3. The dual wavelength band amplifier according to claim 2, wherein a pumping light source is connected to another optical waveguide of each of the first and second sub optical demultiplexers. 4. The wavelength of one of the two optical signals is 1.3.
The first rare-earth-doped optical fiber is a praseodymium-doped optical fiber, and the second rare-earth-doped optical fiber is an erbium-doped optical fiber. 3. The dual wavelength band amplifier according to any one of 3 above. 5. An input / output terminal of the main optical demultiplexer is inserted in the middle of an optical fiber for bidirectional communication.
The two-wavelength band amplifier according to any one of the above. 6. An input / output terminal of the main optical demultiplexer is inserted in the middle of an optical fiber for wavelength division multiplexing communication.
The two-wavelength band amplifier according to any one of the above. 7. A two-wavelength band optical signal which inputs two optical signals having different wavelength bands to an input end, demultiplexes the two signals, amplifies each of them, and then multiplexes them to output from an output end. An amplifier, a terminal connected to the input end through an optical fiber and an optical demultiplexer that multiplexes and demultiplexes two optical signals having different wavelength bands, and an output end through the optical fiber and the optical demultiplexer. A wavelength division multiplex transmission device using a dual wavelength band amplifier, comprising: a connected terminal. 8. The terminal on the input end side comprises two optical transmitters that respectively generate two optical signals having different wavelength bands, and the terminal on the output end side outputs two optical signals having different wavelength bands. 8. An optical transmitter comprising two optical transmitters for receiving light respectively.
A wavelength division multiplex transmission device using the two-wavelength band amplifier described. 9. The terminal on the input end side comprises an optical transmitter for generating an optical signal in one wavelength band and an optical receiver for receiving an optical signal in the other wavelength band, and the terminal on the output end side is 8. A wavelength division multiplexing transmission apparatus using a dual wavelength band amplifier according to claim 7, comprising an optical transmitter for generating an optical signal in the other wavelength band and an optical receiver for receiving an optical signal in one wavelength band.