JPH09289502A - Wavelength multiplex optical submarine cable network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the wavelength multiplex optical submarine cable network which can increase the transmission capacity of light signals without lowering the reliability of transmission quality. SOLUTION: Wavelengths λ1-λi-a-i and λi+b+i-λn of ordinary transmission characteristics among in-use wavelengths are assigned to optical transmitters 1a-1i-a-1 and 1i+b+1-1n of an optical wavelength multiplex transmitting terminal station and a communication is made at a transmission speed of, for example, 5Gbps. Wavelengths λi-a-λi+b of excellent transmission characteristics are assigned to optical transmitters 1i-a-1i+b and a communication is made at a transmission speed of, for example, 10Gbps. Consequently, the optical transmitters 1i-a-1i+b can be increased in transmission capacity by the increase in transmission speed. There is another practical style which is increased in transmission capacity by using light signals of a wavelength area of inferior transmission characteristics at a slow transmission speed or using light signals of wavelength of inferior transmission characteristics for a short-distance ground communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing optical submarine cable network, and more particularly to a wavelength division multiplexing optical submarine cable network capable of increasing transmission capacity while ensuring required transmission quality.

[0002]

2. Description of the Related Art In an optical submarine cable network to which an optical direct amplification technique is applied, a wavelength multiplexing communication method has been conventionally proposed in which optical signals having a plurality of different wavelengths are wavelength-multiplexed for communication. An outline of this conventional wavelength division multiplexing communication method will be described with reference to FIG. Since optical submarine cables are generally long distances, optical signals are attenuated during their transmission.
In order to compensate for this attenuation, a plurality of optical repeaters are provided in the middle of the transmission line, and the optical signals are amplified by the optical repeaters. The transmission characteristic of the optical signal is mainly determined by the characteristic of the optical amplifier in the optical repeater, and in general, the characteristic x in FIG.
become that way. Now, if the transmission rate is constant, the wavelength λ
If the transmission characteristics of the optical signal of i are the best, the transmission characteristics deteriorate as the wavelength becomes smaller than the wavelength λi and as the wavelength becomes larger than the wavelength λi. Therefore, conventionally, optical signals of wavelengths λ1 to λn having a transmission characteristic value s or more required as a minimum condition for a relay transmission line are used for wavelength division multiplexing communication.

FIG. 7 shows a schematic configuration of one system of a conventional wavelength division multiplexing transmission line, which is an optical wavelength division multiplexing transmission terminal station 20 and a multiplexer 2.
1, a relay transmission line 22, a demultiplexer 23, and an optical wavelength multiplex reception terminal station 24. The optical wavelength division multiplexing transmission terminal station 20 is an optical transmitter 2 for transmitting optical signals of wavelengths λ1 to λn.
0a to 20n, the optical wavelength division multiplexing reception terminal station 24 has a wavelength λ
It has optical receivers 24a to 24n for receiving optical signals of 1 to λn. A plurality of optical repeaters 22a to 22m are inserted in the relay transmission line 22 at appropriate intervals. Now, the optical transmitters 20 a to 2 of the optical wavelength division multiplexing transmission terminal station 20
When the optical signals of wavelengths λ1 to λn are transmitted from each of 0n, these optical signals are multiplexed by the multiplexer 21 and enter the relay transmission line 22, and are transmitted through the relay transmission line 22 as optical wavelength multiplexed signals. Is transmitted. During this transmission, it is amplified by the plurality of optical repeaters 22a to 22m and arrives at the demultiplexer 23. The demultiplexer 23 demultiplexes the received optical signal, and the demultiplexed optical signal is received by each of the optical receivers 24a to 24n.

In the wavelength division multiplex communication using the wavelength division multiplex transmission line having such a configuration, conventionally, all the optical signals of the wavelengths λ1 to λn are transmitted at the same transmission rate. For example, all optical signals of wavelengths λ1 to λn are transmitted at 5 Gbps.

[0005]

In recent years, the demand for international communication has been rapidly increasing, and there is a possibility that the transmission capacity of the conventional wavelength division multiplexing transmission line may be exceeded. As a countermeasure against this, it is possible to increase the transmission capacity by slightly lowering the above-mentioned transmission characteristic value s, that is, the threshold value s of the transmission characteristic and using the optical signals of the wavelengths λa1 and λb1. However, with this measure, the transmission quality of communication using optical signals of wavelengths λa1 and λb1 will be inferior to that of wavelengths λ1 to λn, and all users will be provided with communication services under fair communication conditions. There was a problem that I could not do it.

The object of the present invention is to eliminate the above-mentioned problems of the prior art and to transmit an optical signal without lowering the reliability of the transmission quality (that is, without lowering the threshold s of the transmission characteristic). It is to provide a wavelength division multiplexing optical submarine cable network capable of increasing the capacity. Another object of the present invention is to provide a wavelength-multiplexed optical submarine cable network that can inexpensively increase the transmission capacity of an optical signal without laying a new wavelength-multiplexed transmission line.

[0007]

In order to achieve the above object, a feature of the present invention is that a wavelength-division optical submarine cable network that wavelength-multiplexes and communicates optical signals having a plurality of different wavelengths, The point is that a transmission terminal station device for transmitting an optical signal having a wavelength in a wavelength region having a better transmission characteristic at a higher transmission speed is provided. Another feature is that a transmission terminal station device is provided for transmitting an optical signal having a wavelength in a wavelength region having a transmission characteristic lower than that of a used wavelength at a lower transmission rate. Still another feature is 3
In the above-mentioned wavelength-division-multiplexed optical submarine cable network for communication between grounds, a transmission terminal station device that uses an optical signal in a wavelength region having good transmission characteristics is provided as the distance between the grounds becomes longer.

According to the present invention, it is possible to perform communication at a speed higher than the conventional normal transmission speed, and it becomes possible to perform communication using a wavelength in the wavelength region which has not been used conventionally, so that the transmission capacity of the optical signal is increased. Will be able to increase. Also, the longer the distance to the ground is, the more preferentially the optical signal with a wavelength having a good transmission characteristic is used, and the optical signal that is not used or not suitable for the long distance transmission is used between the short distances to the ground. The transmission quality can be averaged without depending on the distance to the ground, and the optical signal wavelength can be effectively used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, in which 1a to 1n are optical transmitters of an optical wavelength multiplex transmission terminal station, 2 is an optical repeater 2a, ... Reference numerals 3a to 3n are optical receivers of an optical wavelength multiplex reception terminal station. Note that a multiplexer, a demultiplexer, etc. are omitted in the figure. In this embodiment, wavelengths λ1 to λi-a-1, λi + b + 1
Optical transmitters 1a to 1i-a-1 and 1 for transmitting optical signals of .about..lambda.n.
i + b + 1 to 1n are transmitted at, for example, 5 Gbps and have a wavelength of λi-a.
An optical transmitter that transmits an optical signal of ~ λi + b is, for example, 10 Gbps
Send with s. FIG. 2 shows that the same transmission rate (in this case, 5 Gbps) and the same transmission distance (in this case,
In the relay transmission line 2), the wavelength λ in the relay transmission line 2
The transmission characteristics of 1 to λn are shown. Here, the transmission characteristic is a factor (Q factor) equal to the electrical SNR that is uniquely associated with the code error rate of the received and reproduced signal. 2 s is the minimum value of the transmission characteristics for which the relay transmission line 2 is required (called the threshold value of the transmission characteristics). That is, as shown in FIG. 2, a wavelength λ having a transmission characteristic value s1 or more whose transmission characteristic is 3 dB or more larger than the threshold value s.
The transmission speed of the optical signals of ia to λi + b is doubled.

According to this embodiment, since the transmission rate of the optical signals of the wavelengths λi-a to λi + b which is equal to or larger than the threshold value s1 is doubled, the transmission characteristic is lowered by about 3 dB, but the system It can be said that the threshold value s of the transmission characteristic required above can be maintained, and therefore the transmission capacity of the system can be increased without deteriorating the transmission quality. As one specific example of the wavelengths λ1 to λn, 1545
nm to 1561 nm can be considered.

FIG. 3 is a schematic configuration diagram of the second embodiment of the present invention. In the figure, 1a1 and 1n1 are 2.5 Gbp
Optical transmitters 3a1 and 3n1 for transmitting at s are optical receivers for receiving the optical signals transmitted by the optical transmitters. Also, 1
a to 1n are optical transmitters that transmit optical signals at 5 Gbps, 3
Reference numerals a to 3n are optical receivers for receiving these optical signals.
FIG. 4 shows the wavelengths λ11, λ1, ..., λn in the relay transmission line 2 at the same transmission rate (5 Gbps in this case) and the same transmission distance (relay transmission line 2 in this case).
The transmission characteristics of λn1 are shown. S in FIG. 4 is the minimum value of the transmission characteristics for which the relay transmission line 2 is sought (called the threshold value of the transmission characteristics).

In this embodiment, as shown in FIG. 4, a transmission characteristic value s2, which is about 3 dB below the threshold s of the transmission characteristic, is set, and the wavelength λ11 corresponding to the transmission characteristic values s to s2 is set. The optical signal of λn1 is transmitted at a reduced transmission rate.

According to this embodiment, at the same transmission rate as other wavelengths, the transmission rate of an optical signal having a wavelength having a slightly poorer transmission characteristic is reduced to 1/2 and used. Since s can be secured, the transmission capacity of the system can be increased without degrading the transmission quality. By using the first and second embodiments together, the transmission capacity of the system can be further increased even after the system is constructed.

Next, a third embodiment of the present invention will be described. FIG. 5 shows a schematic configuration of a wavelength division multiplexing optical submarine cable network of the present embodiment, 10a to 10c are optical transmitters of an optical wavelength division multiplexing transmission terminal station A for transmitting optical signals of wavelengths .lambda.1 to .lambda.3, and 11a is the above-mentioned. The optical receiver of the optical wavelength multiplex receiving terminal station B for receiving the optical signal of the wavelength λ2, 12a is the optical receiver of the optical wavelength multiplex receiving terminal station C for receiving the optical signal of the wavelength λ1, and 13a is the optical receiver of the wavelength λ3. It is an optical receiver of an optical wavelength division multiplexing reception terminal station D for receiving a signal. Also, 15a, 15b
Is an underwater branching device inserted in the relay transmission line.

As shown in the figure, the optical signal of wavelength λ1 sent from the optical transmitter 10a of the optical wavelength division multiplexing transmission terminal station A is transmitted through the relay transmission line and is branched by the undersea branching device 15a. The signal is received by the optical receiver 12a of the station C. The optical signal of wavelength .lambda.2 sent from the optical transmitter 10b of the terminal station A is transmitted through the relay transmission line and received by the optical receiver 11a of the terminal station B. Further, the optical transmitter 10 of the terminal station A
The optical signal of wavelength λ3 sent from c is transmitted through the relay transmission line, branched by the undersea branching device 15b, and received by the optical receiver 13a of the terminal station D.

Now, assuming that the transmission path between the terminal stations A and B is a long distance, the transmission path between the terminal stations A and D is a medium distance, and the transmission path between the terminal stations A and C is a short distance, this embodiment is carried out. In the configuration, the optical signal of the wavelength having the best transmission characteristic is assigned to the transmission between the long-distance terminal stations A and B, and the optical signal of the wavelength having the next best transmission characteristic is transmitted between the intermediate distance terminal stations A-D. The optical signal having the wavelength with the worst transmission characteristic is assigned to the transmission between the short-distance terminal stations A to C. The transmission speed of each optical signal is constant.

By doing so, in the present embodiment, for example, the wavelength λ1 below the threshold s of the transmission characteristic of FIG.
1, λn1, etc. can be assigned for short-distance transmission.
In this case, the transmission distance of the transmission characteristic of FIG. 4 is between the long distance terminal stations AB. As the transmission distance becomes shorter, the deterioration of the quality of the optical signal becomes smaller. Therefore, even if the wavelengths λ11 and λn1 below the threshold s of the transmission characteristic of FIG. It can be ensured and the transmission quality can be sufficiently guaranteed. In the above description, the optical signal is transmitted from the terminal station A to the terminal stations B, C and D. However, when the optical signal is transmitted from another terminal station to a plurality of other terminal stations. Similarly, considering the distance between terminal stations, an optical signal with a good transmission characteristic is used for long-distance communication, and conversely a wavelength with poor transmission characteristic for short-distance communication. Optical signals are used.

Further, as a modification of this embodiment, as in the second and third embodiments, the transmission rate is changed according to the distance between the terminal stations, or the wavelength and transmission rate of the optical signal are changed according to the distance between the terminal stations. Both may be changed.

[0019]

As is apparent from the above description, according to the first to third aspects of the present invention, a higher speed optical signal having a wavelength in a wavelength region having a better transmission characteristic in the used wavelength can be obtained. A transmission end device that communicates at the transmission speed is provided, or a transmission end that transmits at least one of the wavelengths shorter than the shortest used wavelength and longer than the longest used wavelength at a transmission speed lower than the transmission speed of the used wavelength. Since the station device is provided, the transmission capacity of the optical signal can be increased without lowering the reliability of the transmission quality. In addition, the transmission capacity of the optical signal can be increased at low cost without laying a new wavelength division multiplexing transmission line.

Further, according to the inventions of claims 4 and 5, in addition to the above effects, the wavelength dependence of the transmission characteristics in the wavelength division multiplex transmission is effectively utilized to improve the transmission quality of the communication between each ground. There is an effect that it is possible to provide an averaged wavelength division multiplexing optical submarine cable network.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part of the first embodiment.

FIG. 3 is a block diagram showing an outline of a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is an explanatory diagram of a main part of the second embodiment.

FIG. 5 is a block diagram showing an outline of a configuration of a third exemplary embodiment of the present invention.

FIG. 6 is a diagram showing a transmission characteristic of an optical signal wavelength.

FIG. 7 is a block diagram showing an outline of a conventional wavelength division multiplexing optical submarine cable network.

[Explanation of symbols]

1a to 1n ... Optical transmitter, 2 ... Relay transmission line, 2a to 2m ...
Optical repeaters 3a to 3n ... Optical receivers, 10a to 10c ... Optical transmitters, 11a, 12a, 13a ... Optical receivers, 15a,
15b ... Submarine branching device.

Front page continued (72) Inventor Naoki Norimatsu 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo International Telegraph and Telephone Corporation (72) Inventor Koji Goto 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo International Telegraph Phone Co., Ltd.

Claims (5)

[Claims] 1. In a wavelength-multiplexed optical submarine cable network for wavelength-multiplexing and communicating optical signals of a plurality of different wavelengths, an optical signal of a wavelength in a wavelength region having better transmission characteristics among used wavelengths, A wavelength-division-multiplexed optical submarine cable network provided with a transmission terminal device that transmits at a higher transmission speed. 2. In a wavelength-division optical submarine cable network for wavelength-multiplexing and communicating optical signals of a plurality of different wavelengths, the optical signal having a wavelength in a wavelength region having a transmission characteristic lower than a transmission characteristic of a used wavelength is more A wavelength-division-multiplexed optical submarine cable network, which is provided with a transmission terminal device that transmits at a low transmission speed. 3. The wavelength-division-multiplexed optical submarine cable network according to claim 1 or 2, wherein the used wavelength is a wavelength region that achieves a transmission characteristic of at least a transmission characteristic allowed when transmitted at a predetermined transmission speed. Wavelength-multiplexed optical submarine cable network. 4. A submarine branching device having an optical add / drop function is provided in a relay transmission line, and in a wavelength multiplexing optical submarine cable network for communicating between three or more grounds, the longer the distance between the grounds is, the more the transmission characteristics are improved. A wavelength-division-multiplexed optical submarine cable network comprising a transmission terminal device that uses an optical signal in a good wavelength range. 5. The wavelength-division-multiplexed optical submarine cable network according to claim 4, wherein at least one of wavelengths shorter than the shortest wavelength used and longer than the longest wavelength used is used for communication between the shortest distances to the ground. A wavelength-division-multiplexed optical submarine cable network, which is provided with a transmission terminal device.