JP2001028567A - Optical wavelength converter and optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communication system that can easily specify the part which is the cause of an error when the error occurs in a received optical signal. SOLUTION: A transponder 24 converts an optical signal sent from an SDH (synchronous digital hierarchy) terminal station device 2 into electrical signal and discriminates the occurrence of errors in the signal on the basis of parity data in an SOH(section overhead) of the SDH. Similarly a reverse transponder 29 and an SDH receiver 13 discriminate the occurrence of an error on the basis of the parity data. Respective built-in memories are stored with the results of the discrimination, and a place of occurrence of the error is specified on the basis of the storage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical wavelength conversion device and an optical communication system capable of easily specifying a location causing an error in an optical signal.

[0002]

2. Description of the Related Art CCITT (The Theatre) describes an interface for effectively multiplexing various high-speed network services and existing low-speed network services.
International Telegraph and Telephone Consultativ
e Committee) standardized SDH (Synchronous
Digital Hierarchy). FIG. 4 shows 155.52 Mbps (STM-1) of the basic form of the SDH interface.
FIG. 3 is a diagram illustrating a frame structure of an interface. As shown in FIG. 4, the STM-1 frame is composed of 270 columns × 9 rows, and has SOH (Section OverHead) data and payload data. Here, the SOH data is SDH
, And includes parity data B1 and B2, section trace data J0, and the like, as shown in FIG. Here, the parity data B1 is used, for example, for monitoring a code error between repeaters or between a repeater and an SDH terminal device.
The parity data B2 is used for monitoring a code error between the SDH terminal devices. Section trace data J0
Is data indicating a section (line) conduction check.

FIG. 6 is a configuration diagram of an optical communication system 1 employing a conventional SDH system. In the optical communication system 1,
1.3 μm wavelength from the SDH transmitter 3 of the SDH terminal device 2
Is output to the transponder 4. Then, after the optical signal S2 is converted into the electric signal S5 in the 3R_O / E converter 5 of the transponder 4, E / E
In the O converter 6, the light is converted into an optical signal S4 having a wavelength in the 1.55 μm band, for example. The optical signal S4 is 1.55 μm
In the optical fiber 7 for transmission, and is amplified by one or more optical amplifiers 8 provided at predetermined positions on the optical fiber 7 in the transmission process.

The optical signal S4 is input to the reverse transponder 9, is converted into an electric signal S10 by the 3R_O / E converter 10, and is converted into an optical signal S9 having a wavelength of 1.3 μm by the E / O converter 11. The converted optical signal S9 is output to the SDH terminal device 12. And
The optical signal S9 is received by the SDH receiving device 13 of the SDH terminal device 12, and the parity data B1 and B2 of the SOH data in the frame and the section trace data J0
Is determined based on the error.

[0005]

However, in the above-described optical communication system 1, since the transponder 4 and the reverse transponder 9 do not have an error detection function,
Even when the SDH receiving device 12 of the DH terminal device 11 detects that an error has occurred in the optical signal S9, the error is detected between the SDH terminal device 2 and the transponder 4.
Between the transponder 4 and the reverse transponder 9,
And the reverse transponder 9 and the SDH terminal device 1
It is not possible to specify in which section between the two.
Therefore, when an error is frequently detected in the optical signal S9 in the SDH receiver 13 and it seems that the optical communication system 1 has some problem, it is necessary to inspect the entire optical communication system 1 using a tester or the like. There is a problem that the burden associated with the inspection is large. In particular, the sections are often long distances, and the maintenance company of each section may be different, so that it is not possible to give an accurate instruction to the site, which is a problem. In particular, when the optical switching network develops in the future, it is considered that the above-mentioned problems will be greatly increased.

The present invention has been made in view of the above-mentioned problems of the prior art, and when an error occurs in a received optical signal, an optical wavelength converter and an optical communication system capable of easily specifying a location causing the error. The purpose is to provide.

[0007]

In order to solve the above-mentioned problems of the prior art and achieve the above-mentioned object, an optical wavelength converter according to the present invention comprises a photoelectric conversion means for converting an input optical signal into an electric signal. Error detecting means for detecting an error in the electric signal; and electro-optical converting means for converting the electric signal into an output optical signal having a different wavelength from the input optical signal.

In the optical wavelength conversion apparatus according to the present invention, preferably, the input optical signal includes parity data for error detection for each frame, and the error detection means includes the parity data included in the electric signal. Based on the data error.

Further, in the optical wavelength conversion apparatus according to the present invention, the input optical signal includes, for each frame, confirmation data indicating confirmation of line continuity, and the error detecting means includes the confirmation data included in the electric signal. Based on the above, the continuity of the line is confirmed.

Further, the optical wavelength conversion device of the present invention has rewriting means for rewriting the confirmation data of the frame, in which the error detection means has detected that the line has been disconnected, to predetermined data.

An optical communication system according to the present invention comprises: a transmitting device for transmitting a first optical signal having a first wavelength; and a second device for converting the wavelength of the first optical signal input from the transmitting device to a second signal. Wavelength converting means such as a transponder or a reverse transponder for generating a second optical signal having a wavelength of, and outputting the second optical signal to an optical transmission line, and the second optical signal from the wavelength converting means An optical communication system comprising: a receiving device for inputting the first optical signal; and the wavelength converting means, wherein the first optical signal is used as an input optical signal, and the second optical signal is used as an output optical signal. Device.

Further, the optical communication system of the present invention preferably has an error occurrence detecting means for detecting a faulty section from a detection result of the error detecting means of the second wavelength converting means.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical communication system according to an embodiment of the present invention will be described. First Embodiment FIG. 1A is a configuration diagram of an optical communication system 21 of the present embodiment. As shown in FIG. 1A, the optical communication system 2
1 includes an SDH terminal device 2, a transponder 24, a reverse transponder 29, and an SDH terminal device 12. Transponder 24 and reverse transponder 29
A 1.55 μm optical fiber 7 provided with a plurality of, for example, Er-doped optical fiber type optical amplifiers 8 at predetermined locations.
Connected through.

[SDH terminal device 2] The SDH terminal device 2 has an SDH transmitter 3, and the SDH transmitter
An optical signal S2 having a wavelength of 1.3 μm, for example, having the frame structure shown in FIG. 1 is generated and output to the transponder 24.

[Transponder 24] Transponder 2
Reference numeral 4 includes a 3R_O / E converter 5, an SOH monitor 22, which is an example of an error detection unit of the present invention, and an E / O converter 6. The 3R_O / E converter 5 converts the optical signal S2 input from the SDH transmitter 3 into an electric signal S5,
Is output to the SOH monitor 22. At this time, 3R_O /
In the E converter 5, readjustment of timing, waveform shaping,
Gain adjustment and the like are performed.

The SOH monitor 22 controls the parity data B shown in FIG. 5 in the SOH shown in FIG.
1 and B2 are monitored to determine whether a data error has occurred. The SOH monitor 22 stores, for example, a built-in memory, a result of determining whether or not an error has occurred and the error occurrence rate (BER). In addition, the SOH monitor 22 stores the determination result of the section of each frame in the built-in memory based on the section trace data J0 included in the electric signal S5, determines whether the section is conductive, and determines whether the section is conductive. The section trace data J0 of the frame that does not exist is rewritten to fixed data indicating that the section is not conducted.

The E / O converter 6 converts the electric signal S5 input from the SOH monitor 22 into an optical signal S having a wavelength of 1.55 μm.
24, and outputs the optical signal S24 to the optical fiber 7.

[Reverse Transponder 29] The reverse transponder 29 is a 3R_O / E converter 10
An H monitor 23 and an E / O converter 11 are provided. 3R_O /
The E converter 10 receives the optical signal S2 input from the optical fiber 7.
4 to an electric signal S10, and convert the electric signal S10 to SOH
Output to the monitor 23.

The SOH monitor 23 determines whether or not a data error has occurred based on the parity data B1 and B2 shown in FIG. 5 included in the electric signal S10, and stores the result of the determination and the error occurrence rate in a built-in memory. I do. Also, SO
The H monitor 23 stores the determination result of the section of each frame in the built-in memory based on the section trace data J0 included in the electric signal S10 and determines whether or not the conduction is established. Is rewritten to fixed data indicating that the section is not conducted.

The E / O converter 11 converts the electric signal S10 input from the SOH monitor 23 into an optical signal S29 having a wavelength of 1.3 μm, and outputs the optical signal S29 to the SDH terminal device 12.

[SDH terminal device 12] SDH terminal device 1
2 has an SDH receiver 13, and in the SDH receiver 13, an optical signal S29 from the reverse transponder 29 is transmitted.
To receive. The SDH receiver 13 receives the optical signal S2
9 is converted into, for example, an electric signal, and then the presence or absence of an error and the error occurrence rate are determined based on the parity data B1 and B2 shown in FIG. 5 included in the electric signal, and the result of the determination is stored in the built-in memory. I do. SDH receiver 1
No. 3 determines whether or not the section is conducted based on the section trace data J0 shown in FIG. 5 included in the electric signal, and confirms the section conduction.

Hereinafter, the optical communication system 2 shown in FIG.
1 will be described. First, in the SDH transmitter 3 of the SDH terminal station device 2, an optical signal S2 having a frame structure shown in FIGS. 4 and 5 and having a wavelength of, for example, 1.3 μm is generated, and the optical signal S2 is output to the transponder 24.
Then, in the 3R_O / E converter 5 of the transponder 24, the optical signal S2 is converted into an electric signal S5, and the electric signal S5 is output to the SOH monitor 22. And SO
In the H monitor 22, the presence or absence of an error is determined based on the parity data B1 and B2 shown in FIG. 5 included in the electric signal S5, and the result of the determination and the error occurrence rate are stored in, for example, an internal memory. SOH monitor 2
2, it is determined based on section trace data J0 included in the electric signal S5 whether or not the section of each frame is conductive, the determination result is stored in the built-in memory, and the frame in which the section is not conductive is determined. Is rewritten to fixed data indicating that the section trace data J0 is not taken.

Then, in the E / O converter 6, the electric signal S5 is converted into an optical signal S24 having a wavelength of 1.55 μm,
The optical signal S24 is output to the optical fiber 7. Optical signal S2
4 is transmitted through the optical fiber 7 while being amplified by the optical amplifier 8, and is input to the reverse transponder 29. Then, 3R_O / of the reverse transponder 29
In the E converter 10, the optical signal S24 is converted to the electric signal S10.
And the electric signal S10 is output to the SOH monitor 23.

Then, in the SOH monitor 23, the parity data B1, shown in FIG.
Whether or not an error has occurred is determined based on B2, and the result of the determination and the error occurrence rate are stored in the built-in memory. In the SOH monitor 23, it is determined whether or not the section of each frame is conductive based on the section trace data J0 included in the electric signal S10, and the determination result is stored in the built-in memory, and the conductive state of the section is determined. It is rewritten to fixed data indicating that the section trace data J0 of the untaken frame has not been taken. Then, in the E / O converter 11, the electric signal S10 is converted into an optical signal S29 having a wavelength of 1.3 μm,
The optical signal S29 is output to the SDH terminal device 12.

Then, the optical signal S29 from the reverse transponder 29 is transmitted to the SDH receiver 1 of the SDH terminal equipment 12.
3 is output. Then, in the SDH receiver 13,
The received optical signal S29 is converted into an electric signal, and it is determined whether an error has occurred based on the parity data B1 and B2 shown in FIG. 5 included in the electric signal. The result of the determination and the error occurrence rate are stored in the built-in memory. Also,
Based on the section trace data J0 shown in FIG. 5 included in the electric signal, it is determined whether the section of each frame is conductive.

As described above, in the optical communication system 21, the SOH monitors 22, 2 of the transponders 24, 29
3 and the SDH receiver 13 convert the input optical signal into an electric signal, and
Is determined based on the parity data B1 and B2 shown in (1), and the result of the determination is stored in each built-in memory. Therefore, for example, when a problem such as the occurrence frequency of the error of the optical signal S29 received by the SDH receiver 13 becomes extremely high occurs, the occurrence of the error stored in the SOH monitors 22, 23 and the SDH receiver 13 occurs. By examining the determination result of the presence / absence, at any point between the SDH terminal device 2 and the transponder 24, between the transponder 24 and the reverse transponder 29, and between the reverse transponder 29 and the SDH terminal device 12. Whether an error has occurred in the optical signal can be easily specified.

More specifically, if the judgment result stored in the SOH monitor 22 indicates that an error has occurred, it can be understood that there is at least a defective portion between the SDH terminal device 2 and the transponder 24. . If the judgment result stored in the SOH monitor 22 does not indicate that an error has occurred and the judgment result stored in the SOH monitor 23 indicates that an error has occurred, the transponder 24 and the reverse transponder 29 It can be seen that there is a defect in between. If the judgment result stored in the SOH monitors 22 and 23 does not indicate that an error has occurred and the judgment result stored in the SDH receiver 13 indicates that an error has occurred, the reverse transponder 29 and the SDH It can be seen that there is a faulty location between the terminal device 12. As a result, it is possible to reduce the burden of repairing a defect in the optical communication system 21, particularly, a task of identifying a defect occurrence section.

In the optical communication system 21, the SOH monitors 22 and 23 determine whether or not the section is conductive based on the section trace data J0 shown in FIG. 5 included in the electric signal S10. Is stored in the built-in memory, and the section trace data J0 of the frame for which it is determined that the section is not conductive is rewritten to fixed data indicating that the section is not conductive. Therefore, similarly to the case where it is determined whether or not an error has occurred in the parity data B1 and B2, a defective section can be specified.

According to the optical communication system 21, the transponder 24, the reverse transponder 29 and the S
Since the DH terminal device 12 can monitor the error occurrence rate of the optical signal, the transmission quality of the optical signal for each section can be easily known. Usually, in an optical device that does not return an optical signal to an electric signal, it is necessary to return the optical signal to an electric signal only for performing the above-described error detection. Since the device originally converts the optical signal into an electric signal, error detection can be efficiently performed with a very simple configuration, but 3R_O /
The E converters 5 and 10 output electric signals to both the E / O converters 6 and 11 and the SOH monitors 22 and 23.
Even when the OH monitors 22 and 23 break down, the OH monitors 22 and 23 are further effective in that they do not affect signal transmission.

Second Embodiment FIG. 1B is a configuration diagram of an optical communication system 31 according to the present embodiment. As shown in FIG. 1B, the optical communication system 3
1 includes an SDH terminal device 2, a transponder 34, a reverse transponder 39, and an SDH terminal device 12. 1B, the components denoted by the same reference numerals as those in FIG. 1 are the same as the components denoted by the same reference numerals described in the first embodiment. That is, the optical communication system 3
1 has a feature in the transponder 34 and the reverse transponder 39, and particularly has a feature in the connection form of the SOH monitors 22 and 23. As shown in FIG. 1B, in the optical communication system 31, in the transponder 34,
The electric signal S5 from the 3R_O / E converter 5 is output to the E / O converter 6 and the SOH monitor 22. In the reverse transponder 39, the 3R_O / E converter 1
0 from the E / O converter 11 and SO
Output to the H monitor 23. The optical communication system 31 has basically the same effects as the optical communication system 31 shown in FIG. 1A, except that the 3R_O / E converter is an E / O converter and an SOH.
Since an electrical signal is output to both monitors, even if the SOH monitor fails, it has an additional effect in that signal transmission is not affected.

Third Embodiment FIG. 2 shows an example of an optical switch 40 according to the present embodiment. FIG.
As shown in the figure, the optical switch 40 is provided with a multiplexed optical signal λM ₁
To λM _N are converted into optical signals for each predetermined wavelength by the wavelength demultiplexing element 41, each optical signal is wavelength-converted by the transponder 42, and the wavelength-converted optical signal is switched by the optical switch 43 to switch the line. The optical signal is multiplexed by the wave element 44 and output as a remultiplexed optical signal. According to the optical switch 40, it is possible to remultiplex and output a desired combination of optical signals among the multiplexed optical signals. Now, when such an optical switch 40 is applied to an optical communication system such as an optical switching system, compared to the number of users,
There is a high possibility that available wavelengths will be insufficient, and wavelengths must be used effectively. Also, the optical signal is transmitted to the receiving side via several optical switches 40. Therefore, in which section a data error occurs,
It is very important to detect and respond promptly. Here, the transponder 42 is the transponder 24 of FIG.
, And operates in the same manner. Therefore, with a simple configuration, it is possible to quickly detect the presence of a data error or section conduction. As described above, the wavelength conversion device (transiponder 42) of the present invention has an extremely large effect when applied to the optical switch 40 of the optical switching system.

The present invention is not limited to the above embodiment. For example, as shown in FIG. 3, an error occurrence point detection device 60 is provided.
H monitor 22, SOH monitor 23 and SDH receiver 1
The location where the error has occurred may be comprehensively specified based on the error determination signals S22, S23 and S13 indicating the result of the determination of the presence / absence of the error input from Step 3. Alternatively, an error detection result in the SOH monitors 22 and 23 may be put in an empty bit of the SOH and transmitted to a subsequent stage. In the above-described embodiment, 1 is set between the SDH terminal device 2 and the SDH terminal device 12.
Although the case of performing one-to-one one-way communication has been described as an example, the present invention can be applied to, for example, one-to-many or many-to-many one-way communication or two-way communication. Further, for example, when the SDH transmitter 3 shown in FIG. 1 transmits an optical signal with a wavelength of 1.3 μm and the SDH receiver 13 receives an optical signal with a wavelength of 1.55 μm, the transponder 24 It is also possible to convert the wavelength of the optical signal from 1.3 μm to 1.55 μm and construct an optical communication system that does not use the reverse transponder 29.

In the above-described embodiment, the case where the optical signal is transmitted by the SDH method has been described as an example. However, the present invention includes data that can be subjected to error detection, such as parity data and confirmation data. If so, the present invention can be similarly applied to the case of transmitting an optical signal of another transmission method.

[0034]

As described above, according to the optical wavelength conversion device and the optical communication system of the present invention, when an error occurs in an optical signal, it is possible to easily specify a location causing the error.

[Brief description of the drawings]

FIG. 1A is a configuration diagram of an optical communication system according to a first embodiment of the present invention, and FIG. 1B is a configuration diagram of an optical communication system according to a second embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical exchange according to a third embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical communication system according to a modified example of the optical communication system shown in FIG. 1;

FIG. 4 is a block diagram of a basic SDH interface.
It is a figure which shows the frame structure of a 5.52 Mbps (STM-1) interface.

FIG. 5 is a diagram for explaining the SOH shown in FIG. 4;

FIG. 6 is a configuration diagram of a conventional optical communication system.

[Explanation of symbols]

2, 12 SDH terminal equipment, 3 SDH transmitter, 5, 1
0 ... 3 RO / E converter, 6, 11 ... E / O converter, 7 ...
Optical fiber, 8 ... optical amplifier, 13 ... SDH receiver, 2
2, 23 SOH monitor, 24, 34 transponder, 29, 39 reverse transponder, 40 access switch, 41 circuit switch, 42 multiplexer
60 ... Error occurrence point detection device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 1/00 H04B 9/00 E H04N 7/22 T H04Q 3/52 F term (Reference) 5C064 EA05 5K002 BA06 DA02 DA05 DA13 EA06 EA07 5K014 AA01 AA02 AA04 BA02 EA00 GA02 HA01 HA10 5K028 AA14 BB08 DD01 DD02 DD04 KK01 MM10 PP04 PP12 5K069 AA10 EA22 EA26 HA01

Claims (6)

[Claims] A photoelectric conversion unit configured to convert an input optical signal into an electric signal; an error detection unit configured to detect an error of the electric signal; and converting the electric signal into an output optical signal having a wavelength different from that of the input optical signal. An optical wavelength conversion device comprising: 2. The input optical signal according to claim 1, wherein the input optical signal includes parity data for error detection for each frame, and wherein the error detection means detects a data error based on the parity data included in the electric signal. An optical wavelength converter according to the above. 3. The input optical signal includes, for each frame, confirmation data indicating a line continuity check, and the error detecting means checks the line continuity based on the check data included in the electric signal. Claim 1 that performs
3. The optical wavelength converter according to claim 1. 4. The optical wavelength conversion device according to claim 3, further comprising rewriting means for rewriting the confirmation data of the frame, in which the error detection means has detected that the line has been disconnected, to predetermined data. 5. A transmitting device for transmitting a first optical signal having a first wavelength, and a second light having a second wavelength by performing wavelength conversion on the first optical signal input from the transmitting device. An optical communication system comprising: a wavelength conversion unit that generates a signal and outputs the second optical signal to an optical transmission line; and a receiving device that inputs the second optical signal from the wavelength conversion unit. The optical communication system as an optical wavelength conversion device according to claim 1, wherein the conversion unit uses the first optical signal as an input optical signal and uses the second optical signal as an output optical signal. 6. The optical communication system according to claim 5, further comprising an error occurrence point detecting means for detecting a fault section from a detection result of said error detecting means of said wavelength converting means.