JP2000224115A - Optical multiplex relay system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical multiplex relay, in which light rays system sent from optical repeaters are collectively received at one position and an optical amplifier to adjust an optical level from each optical repeater is eliminated. SOLUTION: A sender side transmission line 108 outputs a non-modulated wavelength multiplex light to a forward transmitter side transmission lien 108 from its output terminal 107, receives a return path side wavelength multiplex light 104 from a receiver side transmission line 109 via an input terminal 111 by a variable wavelength filter 112 and an optical receiver 114 receives a light 113 with a specific wavelength. First to N-th optical repeaters 1021,..., 102N are connected in a cascade manner between the output terminal 107 and the input terminal 111 of the transmitter side transmission line 108, and a wavelength multiplex optical amplifier 123 is connected to the final stage optical repeater 102N. This wavelength multiplex optical amplifier 123 amplifies light rays with each wavelength in a lot, so as to eliminate the need for providing an optical amplifier for each optical repeater 102.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplex repeater system using an optical repeater for relaying wavelength multiplexed light, and more particularly, to collectively receive light transmitted from each optical repeater at one place. The present invention relates to an optical multiplex repeater system capable of performing the above-mentioned operations.

[0002]

2. Description of the Related Art Various optical multiplex repeater systems have been proposed which transmit light having different wavelengths to respective optical repeaters and receive the light after modulation by these devices.

FIG. 4 shows an example of an optical multiplex repeater system using a conventional optical multiplex repeater. This optical multiplex communication system includes an optical transceiver 11 and first to N-th optical repeaters 12 ₁ ,..., 12 _N cascade-connected thereto.
It is composed of Here, the optical transceiver 11 transmits the wavelength-division multiplexed light 13 and the first to N-th optical repeaters 12 ₁ ,.
... is a device for receiving the wavelength-multiplexed light 14 which has been sent back from the 12 _N. The first to N-th optical repeaters 12 ₁ ,
.., 12 _N are devices for extracting necessary wavelengths from the transmitted wavelength-division multiplexed light 13, inputting necessary information to the extracted wavelengths, and transmitting the information to the optical transceiver 11.

[0004] The optical transmission / reception device 11 includes first to N-th optical relays.
Device 12₁, ..., 12_NFirst to N-th light sources 1 corresponding to
5₁~ 15_NIt has. The optical combiner 16 is a light source for these light sources.
Fifteen ₁~ 15_NMultiplexed light 1
The number 3 is transmitted from the output end 17 to the transmission side transmission line 18.
The transmission line 18 on the transmission side is constituted by an optical fiber.
You. Receiving-side transmission line 19 also composed of optical fiber
Wavelength multiplexed light 14 transmitted by the
11 to the variable wavelength filter 22 from the input end 21
The light 23 of a specific wavelength is extracted and
Receive the contents.

The first to N-th optical repeaters 12 ₁ ,..., 1
Since 2 _N its construction are the same, for the first optical repeater 12 ₁ illustrating its configuration. The first optical repeater 12 ₁ receives the wavelength multiplexed light 13
From the reception signal output end 32 to the next transmission side transmission line 1
8 is output. Further, the wavelength multiplexed light 14 transmitted from the transmission signal input terminal 33 through the reception side transmission line 19 is received, and the wavelength multiplexed light 14 is transmitted from the transmission signal output end 34 to the next reception side transmission line 19. Has become.

[0006] The first multi-wavelength light 13 received from the reception signal input terminal 31 of the optical relay device 12 _1, the first optical repeater 12 ₁ own wavelength are separated is input to the fixed wavelength demultiplexer 35 You. The light modulator 37 performs modulation for adding information to the light 36 having the separated wavelength. The modulated light 38 is input to an optical amplifier 39 and amplified to a predetermined level, and the amplified light 41 is input to an optical combiner 42.
The optical combiner 42 multiplexes the light 41 onto the wavelength-division multiplexed light 14 input from the transmission signal input terminal 33 and outputs the multiplexed wavelength-division multiplexed light 14 from the transmission signal output terminal 34 to the next reception-side transmission line 1.
9. That is, the first to N-th
The optical repeater 12 _1, ..., 12 in _N, this by modulating by separating the light in each optical repeater own wavelength, the optical transceiver light of each wavelength and joined by optical combining 42 11 To be sent to.

In such an optical multiplex repeater system as shown in FIG. 4, the paths of the transmission lines 18 and 19 are different for each wavelength transmitted from the optical transceiver 11. In general, light of each wavelength transmitted from the optical transmitting / receiving device 11 is
9 and attenuation at each of these connections. Therefore, depending on how the respective optical repeaters 12 ₁ ,..., 12 _N are arranged, the level of the modulated light transmitted to the optical transmitter / receiver 11 via the optical repeaters 12 ₁ ,. If this is not done, it will be different for each wavelength. It is preferable that the light of each wavelength input to the optical receiver 24 has the same level to some extent.

Therefore, in the conventional optical multiplex repeater system shown in FIG. 4, optical amplifiers 39 are separately prepared inside the respective optical repeaters 12 ₁ ,..., 12 _N and input to the optical receiver 24. The light level of each wavelength is adjusted. Therefore, each of the optical repeaters 12 ₁ ,.
Since the optical amplifiers 39 are individually mounted on 12 _N , these devices have a problem that the size of these devices increases or the circuit configuration becomes complicated. Also, each optical repeater 12 ₁ ,
Since the optical amplifier 39 is required for 12 _N , the power consumption of the entire system is increased, which hinders the reduction of the power consumption.

FIG. 5 shows a configuration of an optical multiplex repeater system proposed to solve such a problem. The system disclosed in Japanese Patent Application Laid-Open No. HEI 8-18538 includes a central node 51 and a fiber ring 52.
Terminal node 53 ₁ of the first to N connected in a ring shape by, ..., and a 53 _N. Here, the central node 51 is composed of first to Nth terminal nodes 53 _{1 ,.}
, Λ ₁ ,...,.
A multi-wavelength light source 54 for generating light of λ _N is provided. The first to N-th wavelengths λ ₁ output from the multi-wavelength light source 54,...
, Λ _N are multiplexed by the first optical wavelength multiplexer 55 and sent out to the fiber ring 52 together with the receiving light multiplexed by the second optical wavelength multiplexer 56.

[0010] The second optical wavelength multiplexer 56 in this case, the wavelengths lambda ₁ separated by the separator 57, ..., transducers light of lambda _N 5
8, an optical-electrical signal conversion is performed, and the obtained electric signal is exchanged for each destination by the exchange switch 59, and each wavelength λ ₁ ′, which is converted from the electric signal to light again by the converter 61,.
.., Λ _N ′ are multiplexed.

In the first terminal node 53 ₁ , the separator 63
To separate the multiplexed light, and its own terminal node 53 ₁
Transmission wavelength light λ ₁ and reception wavelength light λ ₁ ′ assigned to
, And further separated by another separator 64.
Then, the reception wavelength light λ ₁ ′ is received by the optical receiver 65.
The transmission wavelength light λ ₁ is supplied to an optical modulator 66 and modulated by a transmission signal 67. This modulated light having the wavelength λ ₁ is input to the multiplexer 68 together with the unseparated light, multiplexed, and transmitted to the _second terminal node 532. 2nd to Nth
The terminal node 53 _2, ..., since the construction of 53 _N is the same ₁ and the first terminal node 53, description thereof is omitted.

[0012]

As described above, in the proposed optical multiplex repeater system, the central node 51 has the first to N-th nodes.
The terminal node 53 _1, ..., has a configuration of connecting the 53 _N in a ring shape. Each wavelength lambda ₁ to the ring-shaped fiber ring 52, ..., the first to be transmitted the light of lambda _N
Terminal node 53 ₁ of the N, ......, while modulating the corresponding light at 53 _N, each wavelength _{λ 1 ', ......, λ N} ' light of the first to
The Nth terminal nodes 53 ₁ ,..., 53 _N receive the signals. That is, in the optical multiplex relay system shown in FIG. 5, the central node 51 exchanges light, and cannot collectively receive the light of the terminal nodes 53 ₁ ,..., 53 _N. Thus, in the proposed optical multiplex repeater system, unlike the optical multiplex repeater system shown in FIG. 4, the optical transmitter / receiver for performing optical transmission / reception cannot be centrally arranged at one place in the system.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate the need for an optical amplifier for centrally receiving light transmitted from each optical repeater at one location and adjusting the level of light from each optical repeater. It is an object of the present invention to provide an optical multiplex repeater system that can perform the above.

[0014]

According to the first aspect of the present invention, there is provided (a) a transmitting means for outputting an unmodulated wavelength-division multiplexed light;
The optical transmitting and receiving apparatus is provided with receiving means for receiving light of one or more desired wavelengths from the wavelength multiplexed light obtained by combining the modulated lights of the respective wavelengths, and (b) transmitted from the optical transmitting and receiving apparatus side. An optical input / output means for inputting the wavelength multiplexed light and outputting the same as it is toward the return side of the wavelength multiplexed light transmission path, and inputting the wavelength multiplexed light after the return of the wavelength multiplexed light transmission path to the own apparatus Separating means for separating the light of the assigned wavelength, modulating means for modulating the light of the wavelength separated by the separating means, and the remaining light separated by the separating means for the light of the wavelength modulated by the modulating means Optical combining means for combining the light with the light having the wavelength of 1 and outputting the combined light to the optical transmitting and receiving apparatus side, sequentially transmitting the wavelength multiplexed light output from the transmitting means of the optical transmitting and receiving apparatus, and returning the folded wavelength multiplexed light. And enter Outputs by modulating the length of the light, and an optical repeater which a plurality of stages cascade-connected as the final stage of the apparatus inputs a wavelength-multiplexed light after the modulation to the receiving means of the optical transceiver,
(C) The wavelength division multiplexing optical amplifying means disposed between the output side of the optical input / output means and the input side to the demultiplexing means of the last stage optical repeater is provided in the optical multiplexing repeater system.

That is, according to the first aspect of the present invention, a plurality of optical repeaters are cascaded to the optical transceiver, and the unmodulated wavelength multiplexed light output from the optical transceiver is transmitted to the optical repeaters. The data is sequentially transferred by the input / output means and input to the wavelength division multiplexing light amplifying means arranged at the return point of the transmission line.
The wavelength multiplexed light output from the wavelength multiplexing optical amplification means is sequentially input to the plurality of optical repeaters in the direction returning to the optical transmission / reception apparatus, and the light of the wavelength assigned to the own apparatus is separated by the respective separation means, and modulated. The light of the wavelength modulated by the means is combined with the light of the remaining wavelength separated by the separating means by the optical combining means and transmitted to the next optical repeater. In this way, the modulated wavelength multiplexed light output from the optical repeater closest to the optical transceiver is input to the receiving means of the optical transceiver. As described above, according to the first aspect of the present invention, the unmodulated wavelength-division multiplexed light is transmitted to the turn-back point, modulated with the corresponding wavelength sequentially from this point, merged with the light of the remaining wavelength, and delivered to the next place. Therefore, the light of each wavelength can be amplified to match the reception level of the optical transmitting and receiving apparatus only by arranging the wavelength multiplexing optical amplifying means at the turning point.

According to the second aspect of the present invention, (a) transmitting means for outputting unmodulated wavelength-division multiplexed light, and one or more wavelengths of desired one or more wavelengths from the wavelength-division multiplexed light obtained by combining the modulated light of each wavelength. An optical transmitting and receiving apparatus comprising: receiving means for receiving light; amplifying means for amplifying light received by the receiving means in accordance with the reception level; and (b) wavelength multiplexing transmitted from the optical transmitting and receiving apparatus. An optical input / output means for inputting light and outputting the light as it is toward the return side of the wavelength multiplexed light transmission path, and inputting the wavelength multiplexed light after the return of the wavelength multiplexed light transmission path and being assigned to its own device Separating means for separating the light having the wavelength of the light having the wavelength, the modulating means for modulating the light having the wavelength separated by the separating means, and the remaining wavelength having been separated by the separating means for the light having the wavelength modulated by the modulating means. To the optical transceiver. Optical multiplexing means for transmitting the wavelength multiplexed light output from the transmission means of the optical transmitting and receiving apparatus, and sequentially input the folded wavelength multiplexed light to modulate the light of the corresponding wavelength. Output, and an optical repeater cascaded in multiple stages so that the last-stage device inputs the modulated wavelength-multiplexed light to the receiving means of the optical transceiver.
(C) The optical multiplex repeater system is provided with a return point connection transmission line for connecting the output side of the optical input / output means of the last-stage optical repeater and the input side to the separation means.

That is, according to the second aspect of the present invention, a plurality of optical repeaters are cascaded to the optical transceiver, and the unmodulated wavelength multiplexed light output from the optical transceiver is transmitted to the optical repeaters. The data is sequentially transferred by the input / output means and turned back at the turning point of the transmission line without any particular amplification. The wavelength multiplexed light output from the wavelength multiplexing light amplifying means is sequentially input to the plurality of optical repeaters in a direction returning to the optical transceiver,
The light of the wavelength assigned to the own device is separated by the respective separating means, and the light of the wavelength after being modulated by the modulating means is combined with the light of the remaining wavelength separated by the separating means by the light combining means, and then the light is combined. To the optical repeater. In this way, the modulated wavelength multiplexed light output from the optical repeater closest to the optical transceiver is input to the receiving means of the optical transceiver. Thus, in the invention according to claim 2,
Since the unmodulated wavelength multiplexed light is transmitted to the turning point, modulated from the corresponding wavelength in this order, and then combined with the light of the remaining wavelength and delivered to the next place, the wavelength multiplexed light amplifying means is used. Amplifying means arranged in the optical transmitting / receiving apparatus and amplifying light before being received by the receiving means in advance according to the receiving level is also merely arranged in the optical transmitting / receiving apparatus so as to match the receiving level of the optical transmitting / receiving apparatus. Light of each wavelength can be amplified.

According to a third aspect of the present invention, in the optical multiplex repeater system according to the first or second aspect, the receiving means of the optical transmission / reception apparatus converts the wavelength-multiplexed light obtained by combining the modulated lights of the respective wavelengths into a desired one. It is characterized by comprising a filter for selecting light of a wavelength, and a selected light receiving means for receiving light selected by the filter.

That is, according to the third aspect of the present invention, since the receiving means includes a filter for selecting light having a desired wavelength from the wavelength multiplexed light, light having a desired wavelength can be extracted and received. .

According to a fourth aspect of the present invention, in the optical multiplex repeater system according to the first aspect, the wavelength division multiplexing optical amplifying means includes an optical transmission and reception device for the optical transmission and reception device according to the level of the wavelength multiplexed light inputted from the last stage optical repeater. It is characterized in that the amplification level is adjusted to a level suitable for reception by the receiving means.

That is, according to the fourth aspect of the present invention, attention is paid to the fact that the wavelength multiplexing light amplifying means inputs the unmodulated wavelength multiplexing light at the return point of the transmission line, and the attenuation of the light by the transmission line or the like up to that point is considered. Investigation and adjustment of the light level on the return path side in response to this check enable the receiving means of the optical transmitting and receiving apparatus to receive an appropriate level of light.

According to a fifth aspect of the present invention, in the optical multiplex repeater system according to the fourth aspect, the wavelength multiplexing optical amplifying means converts the light having a wavelength not used by any of the plurality of cascade-connected optical repeaters from the wavelength multiplexed light. Separately, the amplification factor is controlled according to the reception level.

In other words, according to the fifth aspect of the present invention, the loss of light in a transmission line or the like is determined by using light of a wavelength other than the light of the wavelength assigned to each optical repeater, so that light associated with the determination is determined. I try to eliminate the loss.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows the configuration of an optical multiplex repeater system according to an embodiment of the present invention. This system comprises an optical transceiver 101 and a first cascade connected thereto.
To Nth optical repeaters 102 ₁ ,..., 102 _N. Here, the optical transmitting / receiving device 101 is the wavelength multiplexed light 10.
3 and the first to Nth optical repeaters 102 ₁ ,..., 1
02 is a receiving apparatus capable collectively WDM light 104 sent back from the _N. First to Nth optical repeaters 10
2 _1, ......, 102 _N is fed multi-wavelength light 103
These are devices that take out necessary wavelengths from among them, add (modulate) necessary information to the extracted wavelength components, and send them to the optical transmitting / receiving device 101.

The optical transceiver 101, the optical repeater 102 ₁ of the first to N, ......, first through a wavelength corresponding to 102 _N
Source 105 ₁ of the N, ......, and a 105 _N. The optical combiner 106 combines the lights input from these light sources 105 ₁ ,..., 105 _N and sends the combined light as a wavelength multiplexed light 103 from an output end 107 to a transmission side transmission line 108. In this embodiment, the transmission line 108 is constituted by one optical fiber. ,..., 102 _N via the receiving-side transmission line 109, which is also composed of one optical fiber, and the wavelength-division multiplexed light 104 transmitted from the optical repeaters 102 ₁ ,. The light is taken into the variable wavelength filter 112 from the end 111. Then, light 113 having a specific wavelength is selectively extracted, and the optical receiver 114 receives the light having that wavelength.

The first to N-th optical repeaters 102 ₁ ,.
A wavelength multiplexing optical amplifier 123 is connected between the reception signal output terminal 121 and the transmission signal input terminal 122 of the N-th optical repeater 102 _N at the last stage of the 102 _N. The wavelength-division multiplexing optical amplifier 123 includes first to first optical receivers 114.
This circuit adjusts the level of light of each wavelength sent from the N-th optical repeaters 102 ₁ ,..., 102 _N to the level corresponding to the optical receiver 114.

Therefore, the light 113 on the optical receiver 114 side
In a system where the reception level is not particularly problematic or a system where some level adjustment is performed on the optical transmitting / receiving apparatus 101 side, the wavelength multiplexing optical amplifier 123 itself can be omitted. The amplified wavelength-multiplexed light 132 is output from the wavelength-multiplexed optical amplifier 123.

The first to N-th optical repeaters 102
_1, ......, 102 _N since construction thereof are the same, will be described representatively their configuration for the first optical repeater 102 _1. The first optical repeater 102 ₁ receives the wavelength-division multiplexed light 103 from the reception signal input terminal 125 and receives the next, that is, the optical transmission and reception device 10 from the reception signal output terminal 121.
This is output to the transmission side transmission line 108 located on the side farther from the transmission line 1. Further, it receives the wavelength multiplexed light 104 transmitted from the transmission signal input terminal 122 through the transmission line 109 on the reception side, and receives the wavelength multiplexed light 104 from the transmission signal output terminal 126, that is, the reception side located closer to the optical transceiver 101. The wavelength multiplexed light 104 is transmitted to the transmission line 109. In the case of the first optical repeater 102 ₁ closest to the optical transceiver 101, the wavelength multiplexed light 104 is transmitted to the input terminal 111 of the optical transceiver 101.

In the first optical repeater 102 ₁ , a reception signal output terminal 121 and a reception signal input terminal 125 are directly connected by an optical fiber 131. The wavelength-division multiplexed light 104 sent from the transmission signal output terminal 126 of the optical repeater 102, which is one stage later, is input to the transmission signal input terminal 122 and supplied to the fixed wavelength separator 134, where the light Only the wavelength components to be extracted in the repeater 102 ₁ are separated and input to the optical modulator 135. In the case of the N-th optical repeater 102 _N , the wavelength multiplexed light 104 sent from the wavelength multiplexing optical amplifier 123 is input to the transmission signal input terminal 122 and then to the optical modulator 135.

The optical modulator 135 modulates the light of this wavelength component with data output from a data source (not shown).
The modulated light 137 is supplied to the optical combiner 138. Light 139 of a wavelength component other than the light 136 of the wavelength extracted by the fixed wavelength separator 134 is also input to the optical combiner 138. The optical combiner 138 has these lights 137,
139. That is, the wavelength-division multiplexed light 104 including all the wavelength components transmitted from the optical transmitting / receiving apparatus 101 is transmitted again from the transmission signal output terminal 126 to the next reception-side transmission line 109.
Will be sent to

The operation of the optical multiplex repeater system having such a configuration will be described below. In the optical multiplex repeater system of this embodiment, each of the first to N-th optical repeaters 102 ₁ ,..., 102 _N has its own video information, and each optical modulator 135 has its own Modulation of video information is performed. The variable wavelength filter 112 in the optical transmitting / receiving apparatus 101 selects the wavelength of the light to be selected as necessary, thereby providing the first to N-th optical repeaters 102 ₁ ,.
, 102 _N , video information transmitted from a desired device is received by the optical receiver 114 as light 113.

By the way, the optical multiplexer 106 in the optical transmitting / receiving apparatus 101 includes first to N-th optical repeaters 102 ₁ ,.
The unmodulated lights having the wavelengths corresponding to 02 _N are combined and transmitted from the output end 107 to the transmission side transmission line 108 as the wavelength multiplexed light 103. The wavelength multiplexed light 103 includes first to Nth
The optical repeater 102 _1, ......, 102 _N of the transmitting side transmission line 108 via the order, as a final stage the N optical repeater 102 _N of the reception signal output terminal 121 from the WDM optical amplifier 123 Is input to WDM optical amplifier 123
Are cascaded first to Nth optical repeaters 102 ₁ ,
.., 102 _N are disposed at the turning point. The wavelength multiplexed light 103 up to this point is transmitted on the transmission side transmission line 10 on the way.
Although the light is attenuated at 8, unlike the conventional system shown in FIG.

The wavelength division multiplexing optical amplifier 123 amplifies the wavelength division multiplexed light 103 uniformly for each wavelength so that the reception level of the optical receiver 114 in the optical transmission and reception apparatus 101 becomes an ideal state. Wavelength-multiplexed light 132 after the amplification is input to the transmission signal input terminal 122 of the optical repeater 102 _N of the N. The fixed wavelength separator 134 separates only the light 136 of the wavelength assigned to the _N-th optical repeater 102 _N and sends out the light 139 of the remaining wavelength to the optical combiner 138. Optical modulator 135
Modulates the light 136 based on an image information source (not shown) in the N-th optical repeater 102 _N and sends out the modulated light 137 to the optical combiner 138. The optical combiner 138 outputs these light 1
37 and 139 are combined and sent out from the transmission signal output end 126 to the reception side transmission line 109 as the wavelength multiplexed light 104 in which each wavelength is multiplexed.

The transmitted wavelength multiplexed light 104 is input to the transmission signal input terminal 122 of the (N-1) th optical repeater 102 _N-1 (not shown). Similarly, the (N-
The light 136 of the wavelength assigned to the optical repeater 102 _N-1 of 1) is separated, modulated with its own image information, and similarly combined with light of another wavelength component. Then, the wavelength multiplexed light 104 is transmitted to the next (N-2) th optical repeater 102 _N-2 . Hereinafter, similarly, finally, the first optical repeater 10
2 ₁ wavelength multiplexed light 104 output from the optical transceiver 1
Reach 01.

Therefore, in the path from the wavelength division multiplexing optical amplifier 123 to the optical transmitting / receiving apparatus 101, the light of all the wavelength components transmitted from the optical transmitting / receiving apparatus 101 is transmitted to the respective receiving-side transmission paths 109. In other words, the wavelength division multiplexing optical amplifier 123 does not need to make the amplification factor of a specific one of these wavelength components different from other wavelength components, and simply amplifies all wavelengths with the same amplification factor. This means that it is not necessary to prepare an optical amplifier for each optical repeater 102 differently from the conventional case shown in FIG. In this embodiment, the wavelength division multiplexing optical amplifier 123 is provided after the last N-th optical repeater 102 _1.
Has the advantage that an optical amplifier with a low saturation output can be used for this.

First Modified Example

FIG. 2 shows the configuration of an optical multiplex repeater system according to a first modification of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

In the system of this modified example, the first to N-th optical repeaters 102 ₁ ,.
02 _N are connected in cascade. The reception signal output terminal 1 of the N-th optical repeater 102 _N at the last stage among them
21 and the transmission signal input terminal 122 are directly connected by an optical fiber 151, and the wavelength division multiplexing optical amplifier 123 as shown in FIG. 1 of the previous embodiment is not connected. Instead, a preamplifier 152 is arranged between the input terminal 111 and the variable wavelength filter 112 in the optical transceiver 101A of this modification.

In the optical multiplex repeater system of the modified example having such a configuration, unlike the previous embodiment, the N-th optical repeater 102
_{Since the} wavelength division multiplexing optical amplifier 123 is not connected between the _N reception signal output terminal 121 and the transmission signal input terminal 122, the input signal from the input terminal 111 of the optical transmitting and receiving apparatus 101A is input via the transmission line 108 and the reception line 109. The wavelength multiplexed light 104 is attenuated. The preamplifier 152 amplifies the wavelength-division multiplexed light 104 to a level optimal for reception by the optical receiver 114.

In this modification, light is amplified on the receiving side of the wavelength multiplexed light 104 of the optical transmitting / receiving apparatus 101A. However, depending on the system, the wavelength multiplexed light 103 transmitted from the optical transmitting / receiving apparatus 101 is transmitted to the optical receiver 114. It is also effective to amplify in advance by assuming the reception level of.

Second Modified Example

FIG. 3 shows a circuit configuration of a wavelength division multiplexing optical amplifier of an optical multiplex repeater system according to a second modification of the present invention. Wavelength multiplexing optical amplifier 1 of the second modified example
23A includes a variable amplifier 161 that variably amplifies the wavelength division multiplexed light 103 output from the N-th optical repeater 12 _N. The wavelength-division multiplexed light 162 amplified by the variable amplifier 161 is input to the demultiplexer 163, where it is demultiplexed into the original wavelength-division multiplexed light 132 and the level-detected wavelength-division multiplexed light 164. The wavelength multiplexed light 164 for detection is transmitted to the level detector 16.
5, and its signal level is detected. Then, the variable amplifier 16 is controlled so that the level of the wavelength-division multiplexed light 132 output from the demultiplexer 163 becomes a predetermined desired value.
An amplification control signal 166 is supplied to 1 to adjust the amplification factor.

That is, in the optical multiplex repeater system of the second modification, the wavelength multiplex optical amplifier 123A is normally used as a circuit for feedback-controlling the amplification factor.
If the system configuration of the _first to Nth optical repeaters 102 ₁ ,..., 102 _N is changed, the amplification factor can be controlled in response to the change.

In the embodiment, the variable wavelength filter 112 is used.
Decided to select one desired wavelength component. However, depending on the optical transmitting / receiving device 101, the wavelength division multiplexed light 104 input to the input terminal 111 of the optical transmitting / receiving device 101 is separated into a maximum of N types of wavelength components. May be received in parallel in time.

[0047]

As described above, according to the first aspect of the present invention, unmodulated wavelength-division multiplexed light is transmitted to the turning point, and modulated with the corresponding wavelength from this point, and then combined with the light of the remaining wavelengths. Then, the light of each wavelength can be amplified so as to match the reception level of the optical transmitting and receiving device only by arranging the wavelength multiplexing optical amplifying means at the turning point. Therefore, the optical multiplex repeater system can be economically configured. Moreover, there is an advantage that an optical amplifier having a lower saturation output can be used as compared with the case where the wavelength multiplexing optical amplifying means is arranged in the optical transmitting / receiving apparatus.

According to the second aspect of the present invention, the unmodulated wavelength-division multiplexed light is transmitted to the turning point, modulated in order from this point, and then combined with the light of the remaining wavelengths to the next place. Since it is to be delivered, the wavelength multiplexing optical amplifying means is arranged in the optical transmitting and receiving apparatus, and the amplifying means for amplifying light before being received by the receiving means in advance according to the reception level is also arranged in the optical transmitting and receiving apparatus. By simply doing so, the light of each wavelength can be amplified to match the reception level of the optical transceiver. Therefore, the optical multiplex repeater system can be economically configured. In addition, even when the number of optical repeaters is increased or decreased, the gain of the wavelength division multiplexing optical amplifying means disposed in the optical transceiver may be adjusted, so that maintenance is easy.

Further, according to the third aspect of the present invention, since the receiving means includes a filter for selecting light having a desired wavelength from the wavelength multiplexed light, only light having a desired wavelength can be extracted and received. it can.

Further, in the invention according to claim 4, attention is paid to the fact that the wavelength multiplexing light amplifying means inputs the unmodulated wavelength multiplexed light at the return point of the transmission line, and the attenuation of the light by the transmission line or the like up to that point is considered. Investigating and adjusting the light level on the return path according to this, so that the light of the appropriate level was received by the receiving means of the optical transceiver, so when the number of optical repeaters was increased or decreased, Even if the loss of the transmission line fluctuates due to the cause, the wavelength multiplexed light can always be received at the optimum level.

Further, according to the fifth aspect of the present invention, the loss of light in a transmission line or the like is determined by using light of a wavelength other than the light of the wavelength assigned to each optical repeater, so that the light associated with the determination is determined. Loss can be eliminated.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a configuration of an optical multiplex relay system according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram illustrating a configuration of an optical multiplex relay system according to a first modification of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a wavelength division multiplexing optical amplifier according to a second modification of the present invention.

FIG. 4 is a system configuration diagram showing an example of an optical multiplex repeater system using a conventional optical multiplex repeater.

FIG. 5 is a system configuration diagram of a conventionally proposed optical multiplex relay system.

[Explanation of symbols]

101,101A optical transceiver 102 _1, ......, 102 _N optical repeater of the first to N 103 (the return side) (forward side) wavelength-multiplexed light 104 wavelength-multiplexed light 105 _1, ......, 105 _N first 1st to Nth light sources 106, 138 optical combiner 107 output end (of optical transmitting / receiving device) 108 transmitting side transmission line 109 receiving side transmission line 111 input end (of optical transmitting / receiving device) 112 variable wavelength filter 114 optical receiver 123, 123A WDM optical amplifier 134 Fixed wavelength separator 135 Optical modulator 152 Preamplifier

Claims (5)

[Claims] 1. A transmitter for outputting unmodulated wavelength multiplexed light, and a receiver for receiving light of one or more desired wavelengths from wavelength multiplexed light obtained by combining modulated light of each wavelength. An optical transmitting / receiving device, an optical input / output means for inputting the wavelength multiplexed light sent from the optical transmitting / receiving device side and outputting the wavelength multiplexed light as it is toward the return side of the transmission line of the wavelength multiplexed light, A separating unit that inputs the wavelength-multiplexed light after the return of the transmission line and separates the light of the wavelength assigned to the own device, a modulating unit that modulates the light of the wavelength that is separated by the separating unit, and a modulating unit. Optical combining means for combining the light having the modulated wavelength with the light having the remaining wavelength separated by the separating means and outputting the combined light to the optical transmitting and receiving apparatus side, and the transmitting means of the optical transmitting and receiving apparatus Wavelength multiplexed light output from Next, the folded wavelength multiplexed light is sequentially input, the light of the corresponding wavelength is modulated and output, and the last stage device inputs the modulated wavelength multiplexed light to the receiving means of the optical transceiver. And a wavelength multiplexing optical amplifying means arranged between the output side of the optical input / output means and the input side to the demultiplexing means of the last-stage optical repeater. An optical multiplex repeater system comprising: 2. A transmitting means for outputting unmodulated wavelength multiplexed light, a receiving means for receiving light of one or a plurality of desired wavelengths from wavelength multiplexed light obtained by combining modulated light of each wavelength, and An optical transmitting and receiving apparatus comprising: an amplifying means for amplifying the light received by the receiving means in accordance with the reception level; and a wavelength multiplexing light transmission path for inputting the wavelength multiplexed light sent from the optical transmitting and receiving apparatus side. An optical input / output means for outputting the same as it is toward the return side, and a separating means for inputting the wavelength multiplexed light after the return of the transmission path of the wavelength multiplexed light and separating the light of the wavelength assigned to the own apparatus, A modulating means for modulating the light having the wavelength separated by the separating means; and a light transmitting / receiving device which combines the light having the wavelength modulated by the modulating means with the light having the remaining wavelength separated by the separating means. Light converging means that outputs toward the side The wavelength multiplexed light output from the transmission means of the optical transceiver is sequentially transmitted, and the folded wavelength multiplexed light is sequentially input to modulate and output the light of the corresponding wavelength, and output at the final stage. An optical repeater cascaded in a plurality of stages so that the device inputs the modulated wavelength multiplexed light to the receiving means of the optical transceiver, an output side of the optical input / output means of the last optical repeater, and a separating means An optical multiplex repeater system, comprising: a return point connection transmission line for connecting an input side of the optical multiplexing apparatus to the optical fiber. 3. A filter for selecting light of a desired wavelength from wavelength-division multiplexed light obtained by combining modulated lights of respective wavelengths, and receiving means for receiving the light selected by the filter. 3. The optical multiplex repeater system according to claim 1, further comprising a selection light receiving unit. 4. The wavelength multiplexing optical amplifying means adjusts an amplification level suitable for reception by a receiving means of the optical transmitting / receiving apparatus according to a level of wavelength multiplexed light input from a last-stage optical repeater. The optical multiplex repeater system according to claim 1, wherein: 5. The wavelength division multiplexing optical amplification means separates light having a wavelength not used by any of a plurality of cascade-connected optical repeaters from the wavelength division multiplexing light, and increases the amplification factor according to the reception level. The optical multiplex repeater system according to claim 4, wherein the optical multiplex repeater controls.