JP2000183853A - Wavelength multiplex optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize a wavelength multiplex optical transmission system which compensates the function of a WDM layer by a function of SONET/SDH and can confirm a wavelength connection. SOLUTION: Processing functions for multiple sections, repeating sections, etc., of SONET/SDH (11) are added to a wavelength converting device and a wavelength converting function to manage wavelength path sections as one layer of SONET/SDH (11). A wavelength ID for recognizing WDM wavelength is written to one of overheads of SONET/SDH (11) and on a reception side, connection normalcy is confirmed by checking the wavelength ID.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art An optical transmission system for constructing a core network of a telecommunications carrier generally uses a universal multiplexing method recommended by the ITU-T and a frame configuration thereof. The multiplexing method is called Synchronous Digital Hierarchy (SDH).
The basic speed is 55.52 Mbit / s, and an interface for effectively multiplexing various high-speed services and existing low-speed services is defined. Meanwhile, SONET in North America
(Synchronous Optical Network) is the basis of SDH and is basically the same as SDH, but differs in the method of using bytes of a frame.

[0003] One of the features of the SDH is that there are plenty of areas for transferring operation and maintenance information called overhead in a transmission frame so that network operation can be advanced. Another feature is that network design and operation and maintenance can be hierarchized by clearly incorporating the concept of layering of transmission networks into the frame structure.

FIG. 4 shows a configuration example of a SONET / SDH optical transmission system. In the figure, a multiplexing device (LT:
Line Terminal Multiplexer), add-drop type device (AD
M: Add Drop Multiplexer), cross-connect device (X
C: Cross Connector) is based on SDH. Low-order group path (LO-POH) between exchanges, X
High-order group path (HO-POH), LT and A between C
A multiplex section is used between DMs, and between the LT and ADM and the regenerative repeater, and between regenerative repeaters is distinguished from a relay section. Specifically, the error detection, the type of the detection alarm, the protocol of the transmission line switching, the specification of the failure section, and the like are performed using the overhead.

On the other hand, communication traffic is growing due to the increase in demand for the Internet, the rapid spread of mobile phones, and the development of corporate LANs. Therefore, it is urgent for telecommunications carriers to increase the capacity of core networks. Up to now, the capacity of optical transmission systems has been increased mainly by increasing the transmission speed. However, in recent years, attention has been paid to increasing the capacity using WDM technology. This is 10 in existing SDH.
This is because it is difficult to increase the speed to Gbit / s or higher, and the optical technology supporting WDM has made great progress. At a practical level, there are a 2.4 Gbit / s 32 wave system and a 10 Gbit / s 16 wave system.

FIG. 5 shows an example of the configuration of a general wavelength multiplexing optical transmission system. In the figure, optical signals of wavelength λx output from SONET / SDH devices 51-1 such as a multiplexing device LT, a drop-and-insert device ADM, and a router, respectively,
Wavelengths λ1 to λ4 suitable for WDM in wavelength converter 52-1
And are wavelength-division multiplexed via the optical fiber transmission line 53. The wavelength multiplexed optical signals of the respective wavelengths are reconverted by the wavelength converter 52-2 into optical signals of the wavelength λx, respectively, and the 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 optical signal (O / E) and converting the input optical signal to a target wavelength when the optical signal is converted into an optical signal (E / O) again is used. Take. Other wavelength conversion methods, at the research level, use the gain saturation characteristics of semiconductor optical amplifiers or the oscillation suppression phenomenon of semiconductor lasers, or convert optical signals to electrical signals using nonlinear optical effects such as four-wave mixing. There is also a method of performing wavelength conversion without performing.

As shown in FIG. 6, there is also a configuration in which an ADM / router 57 compatible with WDM for inputting / outputting optical signals of wavelengths λ1 to λ4 for wavelength multiplex transmission without using a wavelength conversion device is used.

Incidentally, the optical fiber transmission line 53 may be combined with an optical amplifying repeater 54 for amplifying a plurality of wavelengths at once or an optical ADM device 55 for dropping and inserting an optical signal of an arbitrary wavelength.

[0010]

The wavelength division multiplexing optical transmission system as shown in FIGS. 5 and 6 can construct a low-cost, large-capacity network, and many telecommunications carriers have begun to introduce it at present. . However, the present wavelength 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 communication company A owning the add-drop type device ADM and a communication company B owning the multiplexing device LT and the router are provided. When the WDM transmission line (wavelength conversion device, optical fiber transmission line, etc.) provided by the communication carrier C is used, the input side of the wavelength conversion device 52 is an interconnection point.

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

The optical ADM 5 is connected to the optical fiber transmission line 53.
It is assumed that the optical signal having the wavelength λ1 is dropped / inserted due to an erroneous setting of the optical ADM 54, for example, as shown in FIG. At this time, the ADM of the communication carrier A
Detects the disconnection, but the carrier C cannot detect the disconnection (problem 2).

Problems 1 and 2 mean that the carrier C cannot guarantee the WDM line provided to the carriers A and B. In the wavelength division multiplexing optical transmission system shown in FIG. 6, as shown in FIG. 8, the above problem 1 is avoided, but the same problem as the problem 2 occurs.

As described above, SONET / SDH
In a base wavelength-division multiplexed optical transmission system, WDM technology is considered part of the optical layer and can be thought of as a virtual optical fiber. However, when the wavelength is taken as a path as shown in FIGS. 5 to 8, as shown in FIG.
A DM layer is required. In future WDM systems,
As shown in FIG. 10, handling a wavelength as a large-capacity optical path has also been studied.

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 the optical ADM is set.
Wavelength .lambda.2 between the device 55-1 and the optical ADM device 55-3.
The optical path of wavelength .lambda.3 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 setting of the optical path as in FIG. 10A, when the optical path of the wavelength λ2 is converted to the wavelength λ1 by the optical ADM device 56-2, the optical ADM device 56-2 and the optical ADM device 56-4 are converted. Can be set to λ2. That is, FIG.
In the case of 0 (b), an optical path using three wavelengths can be realized with two wavelengths.

With an ideal wavelength layer, a large-capacity optical network independent of transmission speed and format can be realized. In such a future wavelength-division multiplexing optical transmission system, it is necessary that the WDM layer directly supports ATM and IP services, and a method of transferring monitoring items and monitoring control information of the WDM layer is indispensable.

As described above, since the WDM technology has matured for the function of transmitting the main signal, the SONET / SD
The product combined with H has also reached the practical level, but the WDM technology is not mature for the function of managing the wavelength path, and the above-described 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 the WDM layer with the function of SONET / SDH.

[0021]

The wavelength converter 52 shown in FIG.
Focusing on the wavelength conversion unit used in the optical ADM apparatus 56 incorporating the wavelength conversion function shown in FIG. 10B, the wavelength conversion of the wavelength division multiplexing optical transmission system is composed of O / E and E / O. Understand. The combination of O / E and E / O is a basic configuration of an optical repeater, and the SONET / SDH repeater is a combination of O / E and E / O with a relay section (RSOH) processing function. .

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

Further, in the present invention, SONET / SDH
The 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,
The receiving side compares the wavelength ID with the expected one. Here, if the wavelength IDs are different, an alarm can be notified as an erroneous connection. In different systems, if different wavelength IDs are assigned to the same wavelength, even if the same optical signal is incorrectly connected as shown in FIGS. Becomes

In a future wavelength division multiplexing optical transmission system, FIG.
A method of changing the wavelength at a node in the middle, such as 0, to reach the target node is also conceivable. According to the present invention, if a wavelength ID (or a device ID or a place ID representing a building or the like) is additionally recorded in a passing wavelength conversion device, the route of an optical path can be traced by the final receiving device.

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, so that the layer structure shown in FIG. 9 does not fit. . However, since the wavelength section is also a relay section, ordinary SONET / SD
It can be considered that the device conforms to the H layer structure.

[0026]

(First Embodiment) FIG. 1 shows a first embodiment of a wavelength division multiplexing optical transmission system according to the present invention.
In the figure, the wavelength division multiplexing optical transmission system of the present embodiment comprises:
SONET / SDH device 11, wavelength converter 12, optical cross-connect device (wavelength-converted light XC) 13 for wavelength conversion and cross-connection of optical signals, optical ADM device 14 for dropping and inserting optical signals, optical amplifier repeater 15 Are linearly connected.

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

FIG. 2 shows the RSOH according to the first embodiment.
Shows how to use. Section overhead (SOH)
Is composed of a relay section overhead (RSOH) and a terminal section overhead (MSOH). R
B1 of the 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, which uses fixedly one byte (8 bits) and assigns a wavelength ID from 1 to 256 (excluding 11111111,00000000).

If a 16-byte multi-frame is formed in the J0 byte, the amount of information to be written increases. In addition to writing a building ID or the like in each device ID, if data is sequentially added, the type of wavelength path will be determined. The final device can confirm whether the vehicle has passed the device or route.

Here, an example using the J0 byte of RSOH has been described, but if the B1 operation function of RSOH is used,
Error measurement of the section for which connection has been confirmed in J0 can also be performed. Further, an MSOH processing function can be provided to perform error measurement using B2. Instead of J0, another unused byte (F1 or DCC) can be used. Similarly to the MSOH, the same applies to the case where a higher-order group path is used.

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

The wavelength path includes wavelength-converted lights XC21, 22,
23, and the wavelengths are converted in the order of λ1, λ2, λ3. Note that 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 λ2 is converted to λ3 by the wavelength conversion light XC23. Here, by additionally writing the wavelength ID, the wavelength converted light XC22 changes from J0 = λ1 to J0 = λ1, λ2, and the wavelength converted light XC23 changes J0 = λ1, λ2 to J0 =
λ1, λ2, 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 the present embodiment, each wavelength converted light XC is
The case where the OH processing function is used and the J0 byte is used has been described.
Error measurement in a section connected with 0 is also possible. Further, each wavelength converted light XC is provided with an MSOH processing function, and it is also possible to perform error measurement by B2. Instead of J0,
Other unused bytes of RSOH (F1 or DCC),
Using the unused bytes of the MSOH and higher order path, J0
It is also possible to perform a connection check similar to the above.

[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 function of the SONET / SDH, the wavelength ID is written into one of the SONET / SDH overheads, By detecting the wavelength ID, it is possible to confirm the wavelength connection.

Further, in a wavelength conversion device that passes therethrough, an optical cross-connect device or an optical ADM having a wavelength conversion function, a wavelength ID (or a device ID or a building ID representing a building or the like).
If D) is added, the route of the optical path can be traced by the last receiving side device.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing a second embodiment of the 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 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 view for explaining a problem of the wavelength division multiplexing optical transmission system shown in FIG. 5;

FIG. 8 is a diagram for explaining a problem of the wavelength division multiplexing optical transmission system shown in FIG. 6;

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]

DESCRIPTION OF SYMBOLS 11 SONET / SDH apparatus 12 Wavelength conversion apparatus 13, 21, 22, 23 Optical cross connect apparatus (wavelength conversion light XC) 14 Optical ADM apparatus 15 Optical amplification repeater 51 SONET / SDH apparatus 52 Wavelength conversion apparatus 53 Optical fiber transmission line 54 Optical amplification repeater 55,56 Optical ADM device 57 ADM / router for WDM

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04J 3/00 (72) Inventor Yoshiki Matsusue 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Stock In-house (72) Inventor Takao Omori 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation F-term (reference) 5K002 AA06 BA06 CA05 CA13 DA02 DA09 EA05 FA01 5K028 BB08 DD05 DD06 MM08 MM14 RR02 TT02

Claims (4)

[Claims] 1. A plurality of optical signals output from a SONET / SDH apparatus or a router apparatus are respectively converted into wavelengths suitable for WDM transmission by a wavelength conversion apparatus, and are converted into an optical fiber transmission line, an optical amplification repeater, or an optical ADM. WDM transmission via an optical fiber transmission line to which at least one is connected,
The WDM-transmitted optical signal of each wavelength is converted to the original wavelength by the opposing wavelength converter, and the opposing SONET /
In a wavelength division multiplexing optical transmission system for reception by an SDH apparatus or a router apparatus, the wavelength conversion apparatus has a SONET / SDH relay section or a multiplex section or a high-order group path processing function, and the SONET / SDH relay section is provided on a transmission side. Alternatively, there is provided a means for writing and transmitting the wavelength ID to either the multiplex section or the higher-order group path overhead, and a means for discriminating the received wavelength ID and confirming whether or not the optical path is correctly connected is provided on the receiving side. A wavelength division multiplexing optical transmission system, comprising: 2. A SONET / SDH device or a router device for inputting / outputting a plurality of optical signals suitable for WDM transmission, and transmitting the optical signals to at least one of an optical fiber transmission line, an optical amplifier repeater, and an optical ADM. In a wavelength division multiplexing optical transmission system for WDM transmission via a connected optical fiber transmission line, the SONET / SDH device or the router
A means for processing the NET / SDH relay section or multiplex section or higher-order group path, and for transmitting, by writing the wavelength ID to any of the SONET / SDH relay section, multiplex section or higher-order group path overhead, and transmitting the same. A wavelength-division multiplexing optical transmission system comprising: a receiving side that includes means for determining a received wavelength ID and confirming whether or not an optical path is correctly connected. 3. A wavelength-division multiplexing optical transmission system including an optical cross-connect device that performs wavelength conversion and cross-connect of an optical signal, and an optical ADM device that performs wavelength conversion and add / drop of an optical signal, wherein the optical cross-connect device or Optical ADM device, SO
A means for processing the NET / SDH relay section or multiplex section or higher-order group path, and for transmitting, by writing the wavelength ID to any of the SONET / SDH relay section, multiplex section or higher-order group path overhead, and transmitting the same. Means for determining the received wavelength ID on the receiving side to confirm whether or not the optical path is correctly connected; and in an optical path in which a plurality of different wavelength sections are connected, each of the devices has a wavelength ID in the overhead. Or a means for additionally adding a device ID or a place ID and confirming a trace of an optical path at a final receiving side device. 4. The wavelength division multiplexing optical transmission system according to claim 1, wherein the overhead to be used is a relay section overhead J0 byte.