JP3520211B2 - WDM optical transmission system - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wavelength division multiplexing technique (W
DM: Wavelength Division Multiplexing (S)
The present invention relates to an ONET / SDH wavelength division multiplexing optical transmission system.

[0002]

2. Description of the Related Art An optical transmission system for constructing a core network of a telecommunications carrier generally uses a globally unified multiplexing method and its frame structure recommended by ITU-T. The multiplexing method is called Synchronous Digital Hierarchy (SDH).
With 55.52 Mbit / s as the basic speed, it specifies an interface for effectively multiplexing various high speed services and existing low speed services. Meanwhile, SONET in North America
(Synchronous Optical Network) is the base of SDH and is basically the same as SDH, but there are differences in the byte usage method of the frame.

One of the characteristics of SDH is that there are plenty of areas called operation overhead for transferring operation and maintenance information in the transmission frame so that the network operation can be advanced. Another feature is that the hierarchical design of the transmission network is clearly incorporated into the frame structure, which enables hierarchical design and maintenance of the network.

FIG. 4 shows a configuration example of a SONET / SDH optical transmission system. In the figure, a multiplexer (LT:
Line Terminal Multiplexer), drop-and-insert device (AD
M: Add Drop Multiplexer, Cross-connect device (X
C: Cross Connector) and the like comply with SDH. Low-order group path (LO-POH), X between the exchanges
Higher-order group path (HO-POH), LT and A between C
The DMs are divided into multiple sections, the LTs and the ADMs and the regenerators are distinguished from each other, and the regenerators are distinguished from the relay sections, so that operation and maintenance are layered. Specifically, the overhead is used to perform error detection, detection alarm type, transmission line switching protocol, and failure section identification.

On the other hand, since the communication traffic is increasing due to the increasing demand for the Internet, the rapid spread of mobile phones, the development of corporate LANs, etc., there is an urgent need for communication carriers to increase the capacity of their core networks. Up to now, the increase in capacity of optical transmission systems has been performed mainly by increasing the transmission speed. However, in recent years, attention has been focused on increasing the capacity using WDM technology. This is 10 in the existing SDH.
This is because it is difficult to achieve higher speeds than Gbit / s and there has been significant progress in optical technology that supports WDM. At a practical level, there are 2.4 Gbit / s 32-wave system and 10 Gbit / s 16-wave system.

FIG. 5 shows a configuration example of a general wavelength division multiplexing optical transmission system. In the figure, the optical signals of wavelength λx output from the SONET / SDH devices 51-1 such as the multiplexer LT, the add / drop multiplexer ADM, and the router are as follows:
Wavelengths λ1 to λ4 suitable for WDM in the wavelength converter 52-1
Respectively, and wavelength division multiplexed transmission is performed via the optical fiber transmission line 53. The wavelength-division-multiplexed optical signals of the respective wavelengths are re-converted into the optical signals of the wavelength λx by the wavelength conversion device 52-2, and the opposite SONET / SDH device 51-
2 is received.

In the wavelength converter 52, as shown in FIG. 5, a method of converting an input optical signal into an opto-electrical (O / E) signal and converting it into an electro-optical (E / O) signal again into a target wavelength is provided. To take. Other wavelength conversion methods, although at the research level, convert optical signals into electrical signals by using the gain saturation characteristics of semiconductor optical amplifiers or the oscillation suppression phenomenon of semiconductor lasers, or by using nonlinear optical effects such as four-wave mixing. There is also a method of performing wavelength conversion without doing so.

Further, as shown in FIG. 6, there is also a configuration in which a WDM-compatible ADM / router 57 for inputting and outputting optical signals of wavelengths λ1 to λ4 for wavelength division multiplexing transmission is used without using a wavelength conversion device.

The optical fiber transmission line 53 may be combined with an optical amplification repeater 54 for collectively amplifying a plurality of wavelengths and an optical ADM device 55 for adding / dropping an optical signal of an arbitrary wavelength.

[0010]

The wavelength division multiplexing optical transmission system as shown in FIGS. 5 and 6 is capable of constructing a low-cost and large-capacity network, and many telecommunications carriers have begun to introduce it at this time. . However, the wavelength division multiplexing optical transmission system has the following problems.

For example, in the wavelength division multiplexing optical transmission system shown in FIG. 5, as shown in FIG. 7, a telecommunications carrier A who owns a drop-and-insert type device ADM and a telecommunications carrier B who owns a multiplexer LT and a router. When using the WDM transmission line (wavelength conversion device, optical fiber transmission line, etc.) provided by the communication carrier C, the input side of the wavelength conversion device 52 serves as an interconnection point.

Here, it is assumed that an erroneous connection occurs between the multiplexing device LT and the router of the communication carrier B and the wavelength conversion device 52-1 of the communication carrier C. At this time, carrier B
The multiplexer LT and the router detect the communication interruption,
The communication carrier C cannot detect the communication interruption (problem 1).

Further, the optical ADM 5 is connected to the optical fiber transmission line 53.
It is assumed that the optical signal of wavelength .lambda.1 is dropped / added due to an erroneous setting of the optical ADM 54 as shown in FIG. At this time, the ADM of the communication carrier A
Detects the communication interruption, but the communication carrier C cannot detect the communication interruption (problem 2).

The problems 1 and 2 mean that the carrier C cannot guarantee the WDM line provided to the carriers A and B. Note that, in the wavelength division multiplexing optical transmission system shown in FIG. 6, the problem 1 is avoided, but the same problem as the problem 2 occurs, as shown in FIG.

As described above, SONET / SDH
In the base wavelength division multiplexing optical transmission system, the WDM technology is considered to be a part of the optical layer and can also be considered as a virtual optical fiber. However, when the wavelength is regarded as a path as shown in FIGS. 5 to 8, as shown in FIG. 9, W which performs necessary monitoring for maintenance operation such as disconnection, quality, and continuity of the wavelength path.
A DM layer is needed. In future WDM systems,
As shown in FIG. 10, it has been studied to treat a wavelength as a large capacity optical path.

FIG. 10A shows an example in which a normal optical ADM device 55 is used. An optical path of wavelength λ1 is set between the optical ADM device 55-1 and the optical ADM device 55-2, and
Between the device 55-1 and the optical ADM device 55-3, the wavelength λ2
The optical path is set, and the optical path of wavelength λ3 is set between the optical ADM device 55-2 and the optical ADM device 55-4.

FIG. 10B shows an example in which an optical ADM device 56 incorporating a wavelength conversion function is used. In the same optical path setting as in FIG. 10A, if the optical path of the wavelength λ2 is converted to the wavelength λ1 by the optical ADM apparatus 56-2, the optical ADM apparatus 56-2 and the optical ADM apparatus 56-4 are connected. The wavelength of the optical path set to can be set to λ2. That is, FIG.
In 0 (b), an optical path using 3 wavelengths can be realized with 2 wavelengths.

With an ideal wavelength layer, a large-capacity optical network that does not depend on the transmission rate or format can be realized. In such a future wavelength division multiplexing optical transmission system, it is necessary for the WDM layer to directly support ATM and IP services, and a monitoring item of the WDM layer and a transfer method of monitoring control information are indispensable.

As described above, since the WDM technology has matured with respect to the function of transmitting the main signal, SONET / SD
Although the product combined with H has reached a practical level, the WDM technology is not matured with respect to the function of managing the wavelength path, and the above-mentioned problem occurs.

An object of the present invention is to provide a wavelength division multiplexing optical transmission system capable of confirming wavelength connection by supplementing the function of WDM layer with the function of SONET / SDH.

[0021]

Wavelength conversion device 52 of FIG.
Focusing on the wavelength conversion unit used in the optical ADM device 56 incorporating the wavelength conversion function shown in FIG. 10 (b), the wavelength conversion of the wavelength division multiplexing optical transmission system is composed of O / E and E / O. Recognize. The combination of O / E and E / O is the basic configuration of the optical repeater, and the SONET / SDH repeater is the one in which the processing function of the relay section (RSOH) is added to O / E and E / O. .

The wavelength division multiplexing optical transmission system of the present invention is characterized in that processing functions such as a SONET / SDH multiplexing section and a relay section are added to the wavelength converting device and the wavelength converting function. By adding the SONET / SDH processing function, the wavelength path section can be managed as one of the SONET / SDH layers.

Further, in the present invention, SONET / SDH
A wavelength ID for recognizing the WDM wavelength is written in any of the overheads. That is, on the transmitting side, the wavelength ID corresponding to the wavelength is written in the SONET / SDH frame,
On the receiving side, it is compared with the expected wavelength ID. If the wavelength IDs are different, an alarm can be notified as an erroneous connection. In different systems, if different wavelength IDs are assigned even for the same wavelength, even if the same optical signal as the wavelength is erroneously connected as shown in FIGS. 7 and 8, an alarm can be notified as an erroneous connection. Becomes

In the future wavelength division multiplexing optical transmission system, FIG.
A method of reaching the target node while changing the wavelength at a node on the way like 0 can be considered. According to the present invention, if the wavelength ID (or the device ID or the place ID representing a building or the like) is additionally written in the passing wavelength conversion device, the final receiving side device can trace the route of the optical path.

In the wavelength division multiplexing optical transmission system of the present invention, the function of the WDM layer is performed by the upper SONET / SDH layer, which does not fit the arrangement of the layer structure shown in FIG. . However, since the wavelength section is also the relay section, normal SONET / SD
It can be considered that the device conforms to the H layer structure.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a first embodiment of a wavelength division multiplexing optical transmission system of the present invention.
In the figure, the wavelength division multiplexing optical transmission system of the present embodiment is
SONET / SDH device 11, wavelength conversion device 12, optical cross-connect device (wavelength conversion optical XC) 13 that performs wavelength conversion and cross-connection of optical signals, optical ADM device 14 that adds and drops optical signals, optical amplification repeater 15 Are connected in a straight line.

Here, a device having a wavelength conversion function, that is, the wavelength conversion device 12 and the optical cross connect device 13
Is equipped with a relay section processing function and has an RSOH structure
The wavelength ID is written in 0 byte. By processing the J0 byte of this relay section, it is possible to confirm the incorrect connection of the wavelength.

FIG. 2 shows the RSOH in the first embodiment.
Shows how to use. Section overhead (SOH)
Is composed of a relay section overhead (RSOH) and a terminal station section overhead (MSOH). R
B1 of SOH is an error monitor (parity check bit) of the relay section, E1 is an order wire, F1 is a user channel, and D1 to D3 are data communication channels (DCC). J0 is a relay section trace, and this 1 byte (8 bits) bit is used fixedly, and wavelength IDs 1 to 256 (excluding 1111111100000000000) are added.

If a 16-byte multi-frame is combined with the J0 byte, the amount of information to be written increases, and not only the building ID and the like can be written in each device ID, but also by sequentially adding data, what kind of wavelength path will be used? You can check the final device to see if it has passed the device or route.

Although the example using the J0 byte of RSOH is shown here, if the B1 arithmetic function of RSOH is used,
It is also possible to measure the error in the section whose connection is confirmed by J0. Further, it is possible to provide an MSOH processing function and perform error measurement by B2. Instead of J0, it is also possible to use another unused byte (F1 or DCC) or the like. Similar to MSOH, the same applies when a higher-order path is used.

(Second Embodiment) FIG. 3 shows a second embodiment of the wavelength division multiplexing optical transmission system of the present invention. The present embodiment is an optical network in which an optical cross-connect device (wavelength conversion light XC) that performs wavelength conversion and cross-connect of an optical signal is connected in a mesh shape, and shows a wavelength path involving wavelength conversion described in FIG. .

The wavelength path is the wavelength-converted light XC21, 22, 22.
23, and the wavelengths are converted in the order of λ1, λ2, and λ3. In addition, there is no wavelength conversion in the wavelength converted light XC21, and the wavelength converted light XC22 converts the wavelength from λ1 to λ2.
The wavelength conversion light XC23 converts the wavelength λ2 to λ3. Here, by adding the wavelength ID, the wavelength converted light XC22 changes from J0 = λ1 to J0 = λ1, λ2, and the wavelength converted light XC23 changes from J0 = λ1, λ2 to J0 =.
It changes to λ1, λ2, and λ3. If the wavelength used in each section is fixed, the trace of the wavelength path can be confirmed by looking at J0 at the end.

In this embodiment, RS is added to each wavelength converted light XC.
The case of using the J0 byte with the OH processing function has been described, but if the B1 arithmetic function of RSOH is used, J
It is also possible to measure the error in the section connected with 0. Further, it is also possible to provide each wavelength converted light XC with an MSOH processing function and perform error measurement by B2. Instead of J0,
Other unused bytes other than RSOH (F1 and DCC),
Using unused bytes of MSOH and higher-order group path, J0
It is also possible to perform the same connection confirmation as.

[0034]

As described above, in the wavelength division multiplexing optical transmission system of the present invention, the function of the WDM layer is supplemented by the SONET / SDH function, the wavelength ID is written in any of the SONET / SDH overheads, and the reception side It is possible to confirm the wavelength connection by detecting the wavelength ID.

Further, in the passing wavelength conversion device, the optical cross-connect device having the wavelength conversion function, or the optical ADM, the wavelength ID (or the device ID or the place I representing the building, etc.)
By adding D), the route of the optical path can be traced by the final receiving side device.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a wavelength division multiplexing optical transmission system of the present invention.

FIG. 2 is a diagram showing how to use RSOH in the first embodiment.

FIG. 3 is a diagram showing a second embodiment of a wavelength division multiplexing optical transmission system of the present invention.

FIG. 4 is a block diagram showing a configuration example of a SONET / SDH optical transmission system.

FIG. 5 is a block diagram showing a configuration example of a general wavelength division multiplexing optical transmission system.

FIG. 6 is a block diagram showing a configuration example of a general wavelength division multiplexing optical transmission system.

FIG. 7 is a diagram illustrating a problem of the wavelength division multiplexing optical transmission system shown in FIG.

FIG. 8 is a diagram illustrating a problem of the wavelength division multiplexing optical transmission system shown in FIG.

FIG. 9 is a diagram showing a layer structure using WDM.

FIG. 10 is a diagram showing an example of a future WDM system.

[Explanation of symbols]

Reference Signs List 11 SONET / SDH device 12 Wavelength conversion device 13, 21, 22, 23 Optical cross-connect device (wavelength conversion light XC) 14 Optical ADM device 15 Optical amplification repeater 51 SONET / SDH device 52 Wavelength conversion device 53 Optical fiber transmission line 54 Optical amplification repeaters 55, 56 Optical ADM equipment 57 ADM / router for WDM

Front Page Continuation (72) Inventor Takao Omori 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) Reference JP-A-11-103275 (JP, A) JP-A-10 −75222 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04J 14/00-14/08 H04J 3/00-3/26 H04B 10/00-10/28

Claims (3)

(57) [Claims] 1. A plurality of optical signals output from a SONET / SDH device or a router device are converted into wavelengths suitable for WDM transmission by a wavelength conversion device, and an optical fiber transmission line, an optical amplification repeater, or an optical ADM is used. WDM transmission via an optical fiber transmission line connecting at least one of
WDM-transmitted optical signals of respective wavelengths are converted to the original wavelengths by opposite wavelength conversion devices, and the opposite SONET /
In a wavelength division multiplexing optical transmission system for receiving in an SDH device or a router device, the wavelength conversion device is provided with a SONET / SDH relay section or multiple section or high-order group path processing function, and the transmission side is provided with the SONET / SDH relay section. Alternatively, a means for writing and transmitting the wavelength ID in either the multiple section or the overhead of the higher-order group path is provided, and the receiving side is provided with means for discriminating the received wavelength ID and confirming whether or not the optical path is properly connected. A wavelength division multiplexing optical transmission system characterized by being provided. 2. A wavelength division multiplexing optical transmission system including an optical cross-connect device for wavelength conversion of optical signals and cross-connect, and an optical ADM device for wavelength conversion and add / drop of optical signals. Optical ADM equipment, SO
The NET / SDH relay section or multiple section or high-order group path processing function is provided, and the transmitting side has means for writing and transmitting a wavelength ID in any of the SONET / SDH relay section or multiple section or high-order group path overhead. In the optical path in which a plurality of different wavelength sections are connected, each device has a wavelength ID in the overhead. Alternatively, the wavelength division multiplexing optical transmission system is provided with a device for additionally recording a device ID or a location ID and confirming a trace of an optical path at a final reception side device. 3. The wavelength division multiplexing optical transmission system according to claim 1 or 2 , wherein the overhead used is J0 bytes of a relay section overhead.