JP7686986B2 - Optical receiver and method for determining optical reception level - Google Patents

Description

This invention relates to an optical receiver and a method for determining an optical reception level, which are used to measure and determine the level of received light in optical communications in which station buildings are connected by multiple optical fibers, for example.

In optical communications (hereafter also referred to as optical fiber communications) in which stations are connected by multiple optical fibers, signal loss detection is performed when receiving light.

One method for detecting signal loss is to compare the optical reception level with a predetermined threshold and detect signal loss if the optical reception level is lower than the threshold (see, for example, Patent Document 1). The signal loss detection method disclosed in Patent Document 1 determines which bit rate is being used for communication among multiple bit rates, and detects signal loss using the threshold for that bit rate.

JP 2012-262792 A

However, in the above-mentioned conventional example, signal loss is determined based on whether the optical reception level is lower than a specific threshold. For this reason, although the signal is not lost, it is not possible to detect signs of abnormality such as the optical reception level being lower than the normal value.

This invention was made in consideration of the above situation. The purpose of this invention is to provide an optical receiver and a method for determining the optical reception level that can prevent failures such as signal loss by detecting that, even if no failure due to signal loss detection has occurred, the amount of optical attenuation is large and there is a possibility that an abnormality will occur in the future.

To achieve the above-mentioned object, the optical receiver of the present invention, which receives optical signals from an optical transmitter via multiple optical fibers, is configured with an optical receiving section, a holding section, and a determination section.

The optical receiving unit acquires an optical reception level for each optical fiber from the received optical signal. The storage unit stores a threshold based on a minimum reception level of the optical receiving unit and a predicted optical reception level, which is an optical reception level for each optical fiber calculated in advance by simulation. When the optical reception level is equal to or higher than the threshold, the determination unit determines whether the optical reception level is equal to or higher than the predicted optical reception level, and determines that the optical reception level is normal when the optical reception level is equal to or higher than the predicted optical reception level.

According to a preferred embodiment of the optical receiver of the present invention, the optical receiver is further configured to include an attenuation acquisition unit that acquires the attenuation as the difference between the optical transmission level and the optical reception level for each optical fiber on the optical transmitter side, and a notification unit.

The holding unit further holds a normal optical reception level, which is an optical reception level measured under normal conditions. The determining unit determines whether or not a first condition is satisfied that the attenuation in the selected optical fiber is equal to or less than a value close to the minimum value of the attenuation in all optical fibers, and determines whether or not a second condition is satisfied that the difference between the normal optical reception level and the optical reception level is equal to or less than a predetermined value, and determines that there is a sign of a failure when both the first condition and the second condition are not satisfied. The notifying unit notifies an external device of a signal loss when the optical reception level is lower than a threshold, notifies an external device of an abnormality sign since it is determined that there is a sign of a failure when both the first condition and the second condition are not satisfied, and notifies an external device of a warning when at least one of the first condition and the second condition is satisfied.

Furthermore, the present invention provides an optical reception level determination method performed by an optical receiver that receives optical signals from an optical transmitter through a plurality of optical fibers, the method comprising the following steps: In the storage step, a first threshold value and a predicted optical reception level, which is an optical reception level for each optical fiber calculated in advance by simulation, are stored; In the optical reception step, an optical signal is received for each optical fiber, and the optical reception level for each optical fiber is obtained from the received optical signals; In the determination step, when the optical reception level is equal to or greater than the first threshold value, it is determined whether the optical reception level is equal to or greater than the predicted optical reception level, and when the optical reception level is equal to or greater than the predicted optical reception level, it is determined to be normal.

According to a preferred embodiment of the optical reception level determination method of the present invention, the method further includes an attenuation acquisition step of acquiring an attenuation amount as a difference between the optical transmission level of each optical fiber on the optical transmitter side and the optical reception level, and a notification step. The first threshold is a threshold based on the minimum reception level of the optical receiver. The holding step further holds a normal optical reception level, which is an optical reception level measured during normal operation. The determination step further includes a first determination step of determining whether or not the attenuation amount in the selected optical fiber satisfies a first condition that the attenuation amount in the selected optical fiber is equal to or less than a value close to the minimum value of the attenuation amount in all optical fibers, and a second determination step of determining whether or not the difference between the normal optical reception level and the optical reception level is equal to or less than a predetermined value. The notification step notifies the outside of a signal loss when the optical reception level is lower than the first threshold, determines that there is a sign of failure when both the first condition and the second condition are not satisfied, and notifies the outside of an abnormality sign, and notifies the outside of a warning when at least one of the first condition and the second condition is satisfied.

According to the optical receiver and optical reception level determination method of the present invention, even if the optical reception level exceeds the threshold and no fault due to signal loss has occurred, if the optical reception level is lower than the predicted optical reception level calculated by simulation, it is not determined to be normal. In this way, if it is not determined to be normal, it can be determined that there is a possibility that an abnormality will occur in the future, so that at that point, it is possible to prevent faults such as signal loss in advance.

FIG. 1 is a schematic block diagram for explaining a configuration example of an optical receiver according to the present invention. FIG. 13 is a diagram for explaining a method for determining an optical reception level, showing a processing flow of an optical receiver.

The following describes an embodiment of the present invention with reference to the drawings, but each drawing is merely a schematic view to allow the invention to be understood. In addition, the following describes a preferred configuration example of the present invention, but this is merely a preferred example. Therefore, the present invention is not limited to the following embodiment, and many modifications or variations can be made that achieve the effects of the present invention without departing from the scope of the configuration of the present invention.

(composition)
An embodiment of a configuration example of an optical receiver according to the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic block diagram for explaining an example of the configuration of an optical receiver according to the present invention.

The optical receiver 100 is used, for example, in optical communications in which stations are connected by a plurality of optical fibers 300. Here, an example will be described in which one station is equipped with an optical transmitter 200 and the other station is equipped with an optical receiver 100. As the plurality of optical fibers 300, a plurality of single-core optical fibers or a multi-core optical fiber may be used, but here, an optical fiber with n cores (n is an integer of 2 or more) is used.

The optical receiver 100 is configured with an optical receiving unit 10, a holding unit 20, an attenuation amount acquisition unit 30, a deterioration amount acquisition unit 40, a determination unit 50, and a notification unit 60.

The optical receiver 10 receives an optical signal for each optical fiber and obtains the optical reception level for each optical fiber from the received optical signal. For example, when a multi-core optical fiber is used, the optical fibers can be connected to multiple ports of one optical receiver. On the other hand, when multiple single-core optical fibers are used, optical receivers according to the number of optical fibers can be prepared and one optical fiber can be connected to each optical receiver. The first to nth optical reception levels RCV_L1 to n obtained for the first to nth optical fibers are sent to the attenuation amount acquisition unit 30, the degradation amount acquisition unit 40, and the determination unit 50.

The optical receiving unit 10 is configured using any suitable conventional technology. The holding unit 20, the attenuation amount acquiring unit 30, the degradation amount acquiring unit 40, the determining unit 50, and the notifying unit 60 only need to realize the functions described below, and a person skilled in the art can configure them using any suitable conventional technology.

The holding unit 20 holds the threshold value MIN_L, the predicted optical reception levels SIM_L1-n, and the normal optical reception levels RVOK_L1-n as necessary. Storage in the holding unit 20 can be configured to be performed by operating any suitable input means provided in the optical receiver 100.

This threshold MIN_L is a predetermined value indicating the minimum reception level of the optical receiving unit 10. This threshold MIN_L is used to determine signal loss, similar to conventional known technology. Note that the threshold MIN_L does not have to match the minimum reception level of the optical receiving unit 10, and may be a value with a margin. Also, here, the threshold MIN_L is described as a common value for each port to which the first to nth optical fibers are input, but a different threshold may be used for each port.

The predicted optical reception levels SIM_L1 to n are the optical reception levels for each optical fiber calculated in advance by simulation. This simulation is performed taking into account the distance between the stations, the characteristics of the optical fiber, and the relay devices through which the optical signals transmitted between the stations pass, and calculates a value close to the actual optical reception level. The prediction of the optical reception level by this simulation can itself be performed using existing technology.

The optical receiver 100 is notified of the optical transmission levels SND_L1-n in the optical transmitter 200 from the optical transmitter 200. The optical transmission levels SND_L1-n are given, for example, by the output setting level of the optical transmitter 200. Alternatively, if the optical transmission level is measured by the optical transmitter 200, the optical transmitter 200 may be configured to notify the optical receiver 100 of the measured value as the optical transmission level. Furthermore, notification to the optical receiver 100 may be made directly from the optical transmitter 200 to the optical receiver 100 via any suitable communication line, or the optical transmission levels SND_L1-n may be input by operating an input means provided in the optical receiver 100.

In FIG. 1, an example is shown in which the optical transmission levels SND_L1-n are stored in the holding unit 20 and sent from the holding unit 20 to the attenuation amount acquisition unit 30, but this is not limiting. In a case where the optical transmitter 200 is measuring the optical transmission levels SND_L1-n, for example, the optical transmission levels SND_L1-n may be configured to be sent directly to the attenuation amount acquisition unit 30 without passing through the holding unit 20.

The attenuation acquisition unit 30 acquires the attenuation RCV_D1-n for each optical fiber. The attenuation RCV_D1-n is given by the difference between the optical transmission level SND_L1-n for each optical fiber on the optical transmitter 200 side and the optical reception level RCV_L1-n for each optical fiber on the optical receiver 100 side.

The degradation amount acquisition unit 40 acquires the degradation amount DIFF_L1-n. The degradation amount DIFF_L1-n is given by the difference between the normal optical reception level RVOK_L1-n and the current optical reception level RCV_L1-n. The normal optical reception level RVOK_L1-n is the optical reception level measured by the optical receiving unit 10 under normal conditions. The normal optical reception level RVOK_L1-n is measured when the optical communication network is constructed, and is stored in the storage unit.

The degradation amounts DIFF_L1 to n are set to take positive values when the amount of attenuation is greater than normal. In other words, the degradation amount DIFF_Lk (k is an integer between 1 and n) is given by RVOK_Lk - RCV_Lk.

The judgment unit 50 is configured to include, for example, a signal loss judgment means 52, an abnormality judgment means 54, and a first judgment means 56 and a second judgment means as abnormality sign judgment means.

The signal loss determination means 52 determines whether the optical reception levels RCV_L1-n are equal to or lower than the threshold value MIN_L. If the signal loss determination means 52 determines that the optical reception levels RCV_L1-n are equal to or lower than the threshold value MIN_L, it determines that a signal loss has occurred. In this case, the notification unit 60 notifies an external party, such as an operator, of the signal loss notification via any suitable output means. This signal loss determination means 52 is configured using any suitable conventionally known technology.

The abnormality determination means 54 determines whether an abnormality exists when the signal loss determination means 52 determines that the optical reception levels RCV_L1 to n are greater than the threshold value MIN_L.

The abnormality determination means 54 determines whether the optical reception levels RCV_L1-n are equal to or greater than the predicted optical reception levels SIM_L1-n. The abnormality determination means 54 determines that the optical reception levels RCV_L1-n are normal when they are equal to or greater than the predicted optical reception levels SIM_L1-n. In this case, the notification unit 60 notifies an external party, such as an operator, that reception is normal, as necessary. Note that if the system is designed normally, the predicted optical reception levels SIM_L1-n will be values that the optical receiving unit 10 can receive, and therefore the predicted optical reception levels SIM_L1-n will be values equal to or greater than the threshold value MIN_L.

Here, if the optical reception level RCV_L1-n is equal to or greater than the threshold MIN_L and is lower than the predicted optical reception level SIM_L1-n, i.e., if MIN_L≦RCV_L1-n<SIM_L1-n is satisfied, then conventionally this would be judged as normal, but there is a possibility of an abnormality.

The first and second determination means 56 and 58, which serve as abnormality sign determination means, determine whether or not there is an abnormality sign when the optical reception levels RCV_L1-n are lower than the predicted optical reception levels SIM_L1-n.

The first determination means 56 determines whether the attenuation amount RCV_D1-n in the selected optical fiber satisfies the first condition that the attenuation amount RCV_D1-n is equal to or less than a value close to the minimum value of the attenuation amount for all optical fibers. Here, the value close to the minimum value of the attenuation amount RCV_D1-n for all optical fibers is a value obtained by adding a margin A that takes into account fluctuations and errors to the minimum value Min(RCV_D1-n) of the attenuation amount RCV_D1-n for all optical fibers. This margin A may be set as a common value for all optical fibers, or may be set for each optical fiber.

For example, if the minimum value of the attenuation amounts RCV_D1 to n is 2 dB and the margin A is 3 dB, if the attenuation amount RCV_Dk for the kth optical fiber does not satisfy the first condition of being 5 dB or less, it is determined that the attenuation is greater than that of the other optical fibers.

The second determination means 58 determines whether the degradation amounts DIFF_L1-n satisfy the second condition that they are equal to or less than a predetermined value B. This predetermined value B is set taking into consideration fluctuations and errors. This predetermined value B may be set as a common value for all optical fibers, or may be set for each optical fiber.

For example, if the predetermined value B is set to 2 dB, and the degradation amount DIFF_L1-n does not satisfy the second condition of being 2 dB or less, it is determined that the attenuation is greater than the initial normal state.

In this way, when neither the first nor the second condition is satisfied, it indicates that the signal attenuation is greater than that of other optical fibers and is worse than the previous state. In this case, the notification unit 60 issues an alarm to an external party such as an operator, indicating that there is a sign of a malfunction. The cause of this predicted malfunction may be, for example, increased attenuation due to dirt on the fiber lens.

When this abnormality warning alarm is issued, it can be determined that there is a possibility that an abnormality will occur at some point. Therefore, by taking measures such as cleaning the lens or replacing the port housing card at the time when the abnormality warning alarm is issued, it is possible to prevent problems such as signal loss.

If at least one of the first and second conditions is satisfied, the notification unit 60 may be configured to issue a warning notification.

(operation)
The optical reception level determination method will be described with reference to Fig. 2. Fig. 2 is a diagram for explaining the optical reception level determination method, showing a processing flow of the optical receiver.

First, in the holding process of step 10 (hereinafter, step is abbreviated as S), initial conditions are set. In S10, the previously calculated predicted optical reception levels SIM_L1-n, the predetermined threshold MIN_L, margin A and predetermined value B, the normal optical reception levels RVOK_L1-n, and the optical transmission levels SND_L1-n are acquired and held in the holding unit 20, etc.

Next, in the optical reception process S20, an optical signal is received for each optical fiber, and the optical reception levels RCV_L1 to n for each optical fiber are obtained from the received optical signals.

Next, in the judgment process of S30, the optical reception level is judged. Here, the judgment using the optical reception level RCV_L1 for the first optical fiber is explained. Judgments for the second to nth optical fibers can be made in the same way as the judgment for the first optical fiber, so explanations are omitted.

The result of the judgment in the judgment process of S30 is notified in the notification process S40.

The judgment process S30 further includes a signal loss judgment process S31, an abnormality judgment process S32, a first judgment process S33, and a second judgment process S34.

In the determination process S30, first, a signal loss determination process S31 is performed.
determines whether or not the optical reception level RCV_L1 for the first optical fiber is equal to or lower than the threshold value MIN_L, that is, whether or not RCV_L1≦MIN_L is satisfied.

If the result of the signal loss determination process S31 is that the optical reception level RCV_L1 is equal to or lower than the threshold value MIN_L (Yes), it is determined that there is a signal loss. If it is determined that there is a signal loss, the signal loss is notified in the notification process S40a.

If the result of the signal loss determination process S31 is that the optical reception level RCV_L1 is greater than the threshold value MIN_L (No), then the abnormality determination process S32 is performed.

In the abnormality determination process S32, it is determined whether the optical reception level RCV_L1 is equal to or greater than the predicted optical reception level SIM_L1, i.e., whether RCV_L1 ≧ SIM_L1 is satisfied.

If the result of the abnormality determination process S32 is that the optical reception level RCV_L1 is equal to or greater than the predicted optical reception level SIM_L1 (Yes), it is determined to be normal. If it is determined to be normal, a notification of normality is given in notification process S40b as necessary.

If the result of the abnormality determination process S32 is that the optical reception level RCV_L1 is lower than the predicted optical reception level SIM_L1 (No), the first determination process S33 is then performed.

In the first determination step S33, the attenuation acquisition unit 30 acquires the first to nth attenuation amounts RCV_D1 to n (= SND_L1 to n - RCV_L1 to n) and determines whether the attenuation amount RCV_D1 is equal to or less than a value close to the minimum attenuation amount for all optical fibers, i.e., whether it satisfies the first condition RCV_D1 ≦ Min (RCV_D1 to n) + A.

If the result of the first determination process S33 is that the first condition is not met (No), the second determination process S34 is then performed.

In the second determination step S34, the deterioration amount acquisition unit 40 acquires the deterioration amount DIFF_L1 (= RVOK_L1 - RCV_L1) and determines whether the deterioration amount DIFF_L1 is equal to or less than a predetermined value B, i.e., whether it satisfies the second condition DIFF_L1 ≦ B.

If the result of the judgment in the second judgment process S34 is that the second condition is not satisfied (No), it is judged that there is a sign of a malfunction. If it is judged that there is a sign of a malfunction, an alarm of the sign of a malfunction is notified in the notification process S40c.

On the other hand, if it is determined in the first determination process S33 that the first condition is met (if Yes) and if it is determined in the second determination process S34 that the second condition is met (if Yes), a warning notification is issued in the notification process S40d as necessary.

According to the optical receiver and optical reception level determination method of the present invention, even if the optical reception level exceeds the threshold and no fault due to signal loss has occurred, if the optical reception level is lower than the predicted optical reception level calculated by simulation, it is not determined to be normal. In this way, if it is not determined to be normal, it can be determined that there is a possibility that an abnormality will occur in the future, so that at that point, it is possible to prevent faults such as signal loss in advance.

REFERENCE SIGNS LIST 10 Optical receiving unit 20 Holding unit 30 Attenuation amount acquiring unit 40 Degradation amount acquiring unit 50 Determination unit 52 Signal loss determining means 54 Abnormality determining means 56 First determining means 58 Second determining means 60 Notification unit 100 Optical receiver 200 Optical transmitter 300 Optical fiber

Claims (2)

An optical receiver for receiving optical signals from an optical transmitter through a plurality of optical fibers,
an optical receiver for acquiring an optical reception level for each optical fiber from a received optical signal;
a storage unit that stores a threshold value based on a minimum reception level of the optical receiving unit and a predicted optical reception level that is an optical reception level for each optical fiber calculated in advance by a simulation;
a determination unit that determines whether or not the optical reception level of an optical fiber having an optical reception level equal to or higher than the threshold is equal to or higher than a predicted optical reception level, and determines that the optical reception level is normal when the optical reception level is equal to or higher than the predicted optical reception level;
an attenuation amount acquiring unit that acquires an attenuation amount as a difference between an optical transmission level for each optical fiber on the optical transmitter side and the optical reception level;
A notification unit,
The storage unit further stores a normal optical reception level, which is an optical reception level measured under normal conditions,
The determination unit is
determining whether or not a first condition is satisfied, that is, the amount of attenuation in the selected optical fiber is equal to or less than a value close to the minimum amount of attenuation in all optical fibers, and whether or not a second condition is satisfied, that is, the difference between the normal optical reception level and the optical reception level is equal to or less than a predetermined value; and, if neither the first condition nor the second condition is satisfied, determining that there is a sign of a failure;
The notification unit notifies the outside of a signal loss when the optical reception level is lower than the threshold, notifies the outside of a sign of an abnormality when both the first condition and the second condition are not satisfied, and notifies the outside of a warning when at least one of the first condition and the second condition is satisfied. 1. A method for determining an optical reception level performed in an optical receiver that receives optical signals from an optical transmitter through a plurality of optical fibers, comprising the steps of:
a storage step of storing a first threshold value and a predicted optical reception level, which is an optical reception level for each optical fiber calculated in advance by a simulation;
an optical receiving step of receiving an optical signal for each optical fiber and acquiring an optical reception level for each optical fiber from the received optical signal;
a determining step of determining whether or not the optical reception level is equal to or higher than a predicted optical reception level for an optical fiber having an optical reception level equal to or higher than the first threshold value, and determining the optical reception level as normal when the optical reception level is equal to or higher than the predicted optical reception level;
an attenuation amount acquisition step of acquiring an attenuation amount as a difference between an optical transmission level for each optical fiber on the optical transmitter side and the optical reception level;
A notification process is also provided.
the first threshold is a threshold based on a minimum reception level of the optical receiver,
In the holding step, a normal optical reception level, which is an optical reception level measured in a normal state, is further held;
The determination process further comprises:
a first determination step of determining whether or not the attenuation in the selected optical fiber satisfies a first condition that the attenuation in the selected optical fiber is equal to or less than a value close to a minimum value of the attenuation in all optical fibers;
a second determination step of determining whether or not a second condition is satisfied, that is, a difference between the normal optical reception level and the optical reception level is equal to or smaller than a predetermined value;
The notification process includes notifying an external party of a signal loss when the optical reception level is lower than the first threshold value, determining that there is a sign of a failure and notifying an external party of an abnormality when both the first condition and the second condition are not satisfied, and notifying an external party of a warning when at least one of the first condition and the second condition is satisfied.

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