JPH09284221A - Optical transmitter and optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To tentatively restore a fault due to reduction in a reception level at a receiver side resulting from deterioration in a light emitting element or a light receiving element or the like. SOLUTION: In the optical transmitters 1, a transmission section 14 of one transmitter is connected to a reception section 15 of the other transmitter by an optical fiber 2 so as to attain data communication in two-way. When a reception level fault that a reception level of a light receiving element provided to the reception section 15 of one optical transmitter 1 is lower than a receptible level is detected, the reception level fault is tentatively restored by using a receptible level revision circuit 15a to revise the receptible level. Furthermore, the fact of the occurrence of the reception level fault is displayed on display sections 16 of both the optical transmitters 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device for performing data communication via an optical fiber and an optical transmission system using this optical transmission device.

[0002]

2. Description of the Related Art Recently, even in monitoring systems for monitoring buildings, factories, water treatment facilities, road facilities, etc.,
Various proposals have been made using an optical transmission system for transmitting and receiving data between optical transmission devices connected via an optical fiber.

In general, an optical transmission device is provided with a transmitter having a light emitting element such as a light emitting diode or a laser diode and a receiver having a light receiving element such as a photodiode. The transmission-side optical transmission device controls the lighting of the light-emitting element to transmit data, and the reception-side optical transmission device detects transmission data from the light received by the light-receiving element.

By the way, when the intensity of light received by the light receiving element (hereinafter referred to as the reception level) drops below a certain value due to deterioration of the light emitting element or the light receiving element or contamination or deterioration of the end surface of the optical fiber, the receiving side. The optical transmission device of No. 1 cannot detect transmission data accurately, resulting in an abnormal reception level.
Therefore, in the optical transmission device, the reception level is always detected, and when the reception level becomes lower than the preset receivable level, an abnormality display or the like is performed to notify the maintenance personnel. Further, when the optical transmission device detects an abnormal reception level, the optical transmission device then executes recovery confirmation processing for confirming whether the reception level has recovered to the receivable level or higher at regular time intervals. If the recovery confirmation process confirms that the abnormal reception level has been recovered, the abnormal display is erased and the normal state is recovered. Note that the restoration confirmation process is executed at regular time intervals because the optical transmission devices on the transmission side and the reception side are installed in separate locations in a normal system. When performing recovery processing such as light emitting element replacement, it is necessary to let maintenance personnel go to the optical transmission device on the receiving side and input that the work for recovery is completed (enter a start command for recovery confirmation processing) This is to eliminate such problems.

[0005]

However, when the reception level on the receiving side fluctuates in the vicinity of the receivable level, abnormality detection and recovery detection are frequently repeated, and an extra load is added to the system, which adversely affects the system. There was a problem of giving. In order to prevent this problem, a method of increasing the time interval for performing recovery detection processing was proposed, but this method can reduce the frequency of repeating abnormality detection and recovery detection, and is a very effective method. Was not.

Therefore, a method has been proposed in which the receivable level is provided with hysteresis, and when an abnormality is detected, it is determined that the reception level has been restored when the reception level becomes higher than the receivable level in the normal state by a predetermined amount. . In this method, even if the time interval for performing the restoration detection process is short, the above-described problem of frequent abnormality detection and restoration detection does not occur, but deteriorated optical fiber, light emitting element, light receiving element, etc. Since the parts in the above are not restored until the maintenance personnel replace them, data communication between the optical transmission devices will be completely stopped during that time, and if a reception level error occurs, the deteriorated parts must be replaced and the parts can be restored. Since it was not there, there was a problem that the cost of system maintenance was high.

An object of the present invention is to provide an optical transmission apparatus for tentatively recovering an abnormal reception level caused by a decrease in reception level caused by deterioration of an optical fiber, a light emitting element, a light receiving element, and the like.
Another object of the present invention is to provide an optical transmission system using this optical transmission device.

[0008]

The present invention described in claim 1 is an optical transmission device for receiving a signal transmitted through an optical fiber and detecting transmission data transmitted from the signal, Reception level abnormality detecting means for detecting a reception level abnormality when the reception level of the received signal is lower than a preset receivable level, and a reception level for changing the reception level when the reception level abnormality is detected And a changing unit.

With this configuration, when the reception level of the received signal is lower than the receivable level at which the transmitted transmission data can be detected, the receivable level is changed to detect the transmission data even at the current reception level. Temporary recovery is carried out so that it can be done. Therefore, for the reception level abnormality caused by the deterioration of the reception level due to the deterioration of the optical fiber, the light emitting element, the light receiving element, etc., the data communication can be stopped until the deteriorated parts are replaced. Absent.

Further, the receivable level changing means is configured to include means for confirming whether or not the reception level abnormality has been resolved by the changed receivable level, thereby simply changing the receivable level. In addition, it is possible to confirm whether or not the reception level abnormality has been resolved by this change.

Further, the optical transmission system described in claims 3 and 4 of the present invention is configured as a system in which a plurality of optical transmission devices described in claims 1 and 2 are connected by an optical fiber. Is.

[0012]

1 is a diagram showing the configuration of an optical transmission system according to an embodiment of the present invention. The optical transmission device 1 is connected by two optical fibers 2. Further, the optical transmission device 1 is connected to a host device 3 that performs processing based on the transmitted data. This upper device 3
Examples of such devices include monitoring devices that monitor buildings, factories, water treatment facilities, road facilities, and the like, and host devices that control the operation of the entire system based on information sent from these monitoring devices.

FIG. 2 is a block diagram showing the configuration of the optical transmission apparatus according to the embodiment of the present invention. The optical transmission device 1 is
A CPU 11, a ROM 12, a RAM 13, a transmission unit 14 having a light source such as a light emitting diode, a reception unit 15 having a light receiving element such as a photodiode, and a display unit 16 for displaying information such as line abnormality. ing. The optical fiber 2 connects the transmitter 14 of one optical transmission device and the receiver 15 of the other optical transmission device 1.

The receiving section 15 outputs a current according to the intensity of the light (input signal) received by the light receiving element 21, and the amplifier 2
2 outputs a signal obtained by amplifying the output of the light receiving element 21 with a set amplification factor, and the discriminator 23 compares a predetermined threshold level set in advance with the signal output from the amplifier 22 and outputs 1 of the input signal. Alternatively, 0 is determined (see FIG. 3). The receiving unit 15 also includes a receivable level changing circuit 15a. The receivable level changing circuit 15a changes the receivable level referred to in the present invention by changing the amplification factor of the amplifier 22.

Next, the operation of the optical transmission device 1 according to the embodiment of the present invention will be described. The optical transmission device 1 transmits and receives data to and from each other via the optical fiber 2. When the data to be transmitted is input from the connected higher-level device 3 or the like, the optical transmission device 1 controls the lighting of a light emitting element such as a light emitting diode at a preset transmission level of the input data, Send data. In this embodiment, since the light emitting element can obtain a light output that is substantially proportional to the magnitude of the driving current, the transmission level is set by setting the magnitude of the driving current passed through the light emitting element.

The other optical transmission device 1 detects transmission data from the light received by the light receiving element 21 and transfers the detected transmission data to the connected higher-level device 3. Host device 3
Then, processing based on this data is performed to control the operation of the entire system. In addition, the optical transmission device 1 has the transmitting unit 14 at a predetermined time interval even when there is no data to be transmitted.
A light emitting element such as a light emitting diode provided in the light emitting device emits light at a set transmission level. In addition, the optical transmission device 1
Then, when the light receiving element 21 receives light, the attenuation amount is calculated from the transmission level of the data on the transmitting side and the reception level of the data received by the receiving section 15, and the calculated attenuation amount is displayed on the display section 16
It is displayed on the screen so that maintenance personnel can be informed of the system status. Here, the transmission level on the transmission side may be stored in the reception side in advance, or may be notified from the transmission side to the reception side.

The optical transmission device 1 repeatedly executes the following reception level confirmation processing for confirming the reception level at predetermined timings. FIG. 4 shows an optical transmission device 1 on the receiving side.
5 is a flowchart showing a reception level confirmation process of FIG. As described above, even when the data is not transmitted, the light emitting element provided in the transmitting unit 14 is made to emit light at the data transmission level at a predetermined time interval, so that the light receiving element 21 emits light at a predetermined time interval. Is received.

At a predetermined timing (timing for checking the reception level) (n1), the optical transmission device 1 detects the reception level of the light received by the light receiving element 21 (n).
2). Then, it is determined whether the detected reception level is lower than the receivable level at which the transmitted transmission data can be accurately detected (n3). If the reception level is higher than the receivable level at n3, the reception level normal is notified to the transmitting side optical transmission apparatus 1 to complete the reception level confirmation processing this time (n4), and the process returns to n1.
On the other hand, when the reception level is lower than the receivable level, the fact that the reception level is abnormal is displayed on the display unit 16 (n5), and the receivable level changing process for changing the receivable level is performed (n6). , N1.

FIG. 5 is a flowchart showing the receivable level changing process. The optical transmission device 1 on the receiving side determines whether or not the current receivable level is the maximum value of the preset receivable level (maximum receivable level) (n11). If it is determined in n11 that the receivable level is not the maximum receivable level, the receivable level changing circuit 15a lowers the receivable level by AdB (A is preset) (n12). To change the receivable level,
As described above, this is performed by changing the amplification factor of the amplifier 22. Therefore, the reception level changing circuit 15a may have a function of changing the amplification factor of the amplifier 22.
Can be configured easily and inexpensively.

Then, it is confirmed whether the changed receivable level is restored to a state in which the transmission data can be accurately detected from the signal of the current reception level (the reception level determined to be abnormal) (temporary restoration). (N13). Upon confirming that the temporary restoration has been performed, the changed receivable level is displayed on the display unit 16 (n14), and the receivable level is notified to the optical transmission device 1 on the transmission side to complete the receivable level changing process. (N15). The optical transmission device 1 that has received the notification of the change in the receivable level displays a message to that effect on the display unit 16.

On the other hand, if the changed receivable level cannot accurately detect the transmission data from the signal of the current reception level (not temporarily restored), n1
The procedure returns to 1 and the above processing is repeated. Further, when it is determined that the maximum receivable level is preset in n11, the receivable level is returned to the initial value (n16), the communication failure is displayed on the display unit 16 (n17), and a message to that effect is transmitted. The optical transmission device 1 on the side is notified (n18). Here, even if the receivable level is set to the maximum receivable level, if provisional restoration cannot be performed, it is in a state in which parts such as disconnection of the optical fiber 2 need to be replaced. The optical transmission device 1 on the transmission side that has received the notification of the communication failure displays a message to that effect on the display unit 16.

Then, after the restoration work such as the replacement of the deteriorated parts is completed (n19), the restoration confirmation process is performed after the restoration work is completed, and the process is completed (n20). The return confirmation process will be described later.

As described above, according to this embodiment,
By changing the receivable level, it is possible to make the data communication possible between the optical transmission devices 1 without replacing the parts that have deteriorated due to the abnormal reception level (temporary restoration can be performed). Therefore, it is possible to reduce the frequency of exchanging the deteriorated parts, and to reduce the cost required for system maintenance. Further, unlike the conventional case, the abnormality detection and the restoration detection are not frequently repeated, so that an extra load is not applied to the system, and therefore the problem that the entire system is adversely affected does not occur. Further, since the fact that the temporary restoration has been performed is displayed on both the transmission side and the reception side of the optical transmission device 1, maintenance personnel do not go to the installation locations of both optical transmission devices at the time of inspection and It is possible to know whether the temporary restoration is being performed by simply going to the installation location of the device 1. As a result, the time and effort required for the maintenance work by the maintenance personnel can be reduced.

FIG. 6 is a flow chart showing the return confirmation processing. When the maintenance work such as the replacement of the optical fiber 2 by the maintenance personnel is completed, an input indicating that the restoration work is completed is input from the optical transmission device 1 or the host device 3. If there is this input, it is determined that the restoration work is completed in n19, and the restoration confirmation processing described below is executed. The optical transmission device 1 on the receiving side sets the receivable level to the initial value (n31), and confirms whether a reception level abnormality occurs at this receivable level (n32). If an abnormal reception level occurs at this reception level, the fact that the restoration process has not been performed correctly is displayed, and the receivable level changing process described above is performed (n33). On the other hand, when no abnormal reception level occurs, the optical transmission device 1 on the receiving side raises the receivable level to BdB (B is set in advance) (n3).
4) It is confirmed whether an abnormal reception level occurs at this receivable level (n35). At this time, if the reception level abnormality does not occur, the process returns to n34, further raises the receivable level by BdB, and confirms whether the reception level abnormality occurs. Repeat the processing of n34 and n35,
When the receivable level at which the reception level abnormality occurs is detected, the optical transmission device 1 detects the receivable level detected and
After the maintenance work is completed, a design value at which a reception level abnormality occurs (this value is stored in the RAM 13) is compared (n36), and if the receivable level confirmed on the display unit 16 is smaller than the design value, it is normal. Is displayed on the screen (n
37), if it is larger than the design value, that effect (worse than the design value) is displayed (n38). Then, the receivable level is returned to the initial value and the processing is completed (n39). Or later,
Operates with the receivable level set to this initial value,
When it is detected that a reception level abnormality has occurred, the above receivable level changing process is performed.

As described above, when the maintenance work is performed by the maintenance personnel, the receivable level at which the reception level abnormality occurs is detected and the receivable level is compared with the design value. It is also possible to inform the maintenance personnel whether the restoration work has been done correctly.

In the above example, an explanation has been given of an example in which a backup line is not provided to enable data communication even if the optical fiber or the like is broken, but it is an optical transmission system provided with a backup line. Needless to say. Also,
The description has been given by taking the system in which the optical transmission devices 1 are connected by two optical fibers as an example, but the present invention can also be applied to a system in which bidirectional data communication is performed by one optical fiber. Further, although the receivable level is changed by changing the amplification factor of the amplifier 22, the discriminator 23
This may be performed by changing the threshold value in the above, or the receivable level may be changed by another method.

[0027]

As described above, according to the present invention, the receivable level is changed so that the temporary recovery from the abnormal reception level is automatically performed, which causes a serious problem such as disconnection of the optical fiber. Unless it occurs, the data communication does not stop between the optical transmission devices. Further, it is possible to reduce the frequency of exchanging deteriorated optical fibers, light emitting elements, etc., as compared with the related art, and reduce the cost for system maintenance. Further, unlike the conventional case, the abnormality detection and the recovery detection are not frequently repeated, and the problem of adding an extra load to the system and adversely affecting the system does not occur.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of an optical transmission device according to this embodiment.

FIG. 3 is a diagram showing a configuration of a receiving unit of the optical transmission device according to the same embodiment.

FIG. 4 is a flowchart showing a reception level confirmation process of the optical transmission device.

FIG. 5 is a flowchart showing receivable level changing processing of the optical transmission device.

FIG. 6 is a flowchart showing a restoration confirmation process of the optical transmission device.

[Explanation of symbols]

 1-optical transmission device 2-optical fiber 11-CPU 12-ROM 13-RAM 14-transmitter 15-receiver 15a-receivable level changing circuit 16-display

Claims (4)

[Claims] 1. In an optical transmission device for receiving a signal transmitted through an optical fiber and detecting transmission data transmitted from this signal, the reception level of the received signal is a preset receivable level. An optical transmission comprising: a reception level abnormality detecting means for detecting a reception level abnormality when the reception level is lower; and a reception level changing means for changing the reception level when the reception level abnormality is detected. apparatus. 2. The optical transmission device according to claim 1, wherein the receivable level changing means includes means for confirming whether or not the reception level abnormality has been resolved at the changed receivable level. 3. In an optical transmission system in which a plurality of optical transmission devices are connected by an optical fiber, a reception level abnormality is detected when the reception level of a signal received by each optical transmission device is lower than a preset receivable level. An optical transmission system, comprising: a reception level abnormality detecting means for controlling the reception level; and a reception level changing means for changing the reception level when the reception level abnormality is detected. 4. The optical transmission system according to claim 3, wherein the receivable level changing means includes means for confirming whether or not the reception level abnormality is resolved at the changed receivable level.