Optical Receiver and Optical Reception Level Determination Method

Abstract

To avoid failure such as signal disconnection by detecting possibility of abnormality in the future by detecting a large optical attenuation amount even though trouble due to signal disconnection detection has not occurred.SOLUTION: An optical receiver for receiving an optical signal from an optical transmitter through a plurality of optical fibers, includes an optical receiver section 10, a storage section 20, and a determination section 50. The optical receiver section acquires optical reception levels for each optical fiber from received optical signals. The storage section stores a predetermined threshold value and a predicted optical reception level which is an optical reception level for each optical fiber previously calculated by simulation. The determination section determines whether the optical reception level is the predicted optical reception level or higher if the optical reception level is the threshold value or more, and determines as normal if the optical reception level is the predicted optical reception level or higher.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical receiver and an optical reception level determination method used for measurement and determination of a received optical level in optical communication performed by connecting between buildings with a plurality of optical fibers, for example.

Background Art

[0002] In optical communication (hereinafter also referred to as optical fiber communication) performed by connecting between buildings with a plurality of optical fibers, signal loss detection is performed at the time of optical reception.

[0003] As a signal loss detection method, there is a method of comparing an optical reception level with a predetermined threshold value and detecting signal loss when the optical reception level is lower than the threshold value (see, for example, Patent Document 1). In the signal loss detection method disclosed in this Patent Document 1, it is determined which bit rate among a plurality of bit rates is being communicated, and signal loss detection is performed using the threshold value for that bit rate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above-described conventional example, signal loss determination is performed based on whether the optical reception level is lower than a specific threshold value. For this reason, although signal loss does not occur, it has not been possible to detect signs of abnormality such as the optical reception level being lower than the original normal value.

[0006] The present invention has been made in view of the above situation. The object of the present invention is to prevent failures such as signal interruption by detecting that although there is no failure due to signal interruption detection, the optical attenuation amount is large and there is a possibility of becoming abnormal in the future, and to provide an optical receiver and an optical reception optical level determination method capable of doing so.

Means for Solving the Problems

[0007] In order to achieve the above-described object, an optical receiver that receives an optical signal from an optical transmitter via a plurality of optical fibers according to the present invention includes an optical reception unit, a holding unit, and a determination unit.

[0008] The optical reception unit acquires the optical reception level for each optical fiber from the received optical signal. The holding unit Based on the minimum reception level of the optical receiver unit holds a threshold value and a predicted optical reception level that is the optical reception level for each optical fiber calculated in advance by simulation. The determination unit determines whether or not the optical reception level is equal to or higher than the predicted optical reception level when the optical reception level is equal to or higher than the threshold value, and determines that it is normal when the optical reception level is equal to or higher than the predicted optical reception level.

[0009] According to a preferred embodiment of the optical receiver of the present invention, further, an attenuation amount acquisition unit that acquires an attenuation amount as a difference between the optical transmission level for each optical fiber on the optical transmitter side and the optical reception level, and a notification unit are provided.

[0010] The holding unit further holds a normal-time optical reception level that is the optical reception level measured during normal times. The determination unit determines whether or not a first condition that the attenuation amount in the selected optical fiber is equal to or less than a value near the minimum value of the attenuation amounts in all the optical fibers is satisfied, and determines whether or not a second condition that the difference between the normal-time optical reception level and the optical reception level is equal to or less than a predetermined value is satisfied, and further If both the first condition and the second condition are not satisfied, it is determined that there is a sign of failure. When the optical reception level is lower than the threshold value, the notification unit notifies the outside of a signal interruption. When both the first condition and the second condition are not satisfied, since it is determined that there is a sign of failure, an abnormal sign is notified to the outside. When at least one of the first condition and the second condition is satisfied, a warning is notified to the outside.

[0011] In addition, the optical reception level determination method performed by an optical receiver that receives an optical signal from an optical transmitter through a plurality of optical fibers according to the present invention is configured to include the following processes. In the holding process, a first threshold value and a predicted optical reception level, which is the optical reception level for each optical fiber calculated in advance by simulation, are held. In the optical reception process, an optical signal is received for each optical fiber, and the optical reception level for each optical fiber is obtained from the received optical signal. In the determination process, when the optical reception level is First equal to or higher than the threshold value, it is determined whether the optical reception level is equal to or higher than the predicted optical reception level, and when the optical reception level is equal to or higher than the predicted optical reception level, it is determined to be normal.

[0012] According to a preferred embodiment of the optical reception level determination method of the present invention, further, an attenuation amount acquisition process for acquiring an attenuation amount as a difference between the optical transmission level for each optical fiber on the optical transmitter side and the optical reception level, and a notification process are provided. The first threshold value is a threshold value based on the minimum reception level of the optical receiver. In the holding process, further, a normal-time optical reception level, which is the optical reception level measured during normal operation, is held. The determination process further includes a first determination process for determining whether a first condition that the attenuation amount in the selected optical fiber is equal to or less than a value near the minimum value of the attenuation amounts in all the optical fibers is satisfied, and a second determination process for determining whether a second condition that the difference between the normal-time optical reception level and the optical reception level is equal to or less than a predetermined value is satisfied. The notification process is such that when the optical reception level is First lower than the threshold value, a signal interruption is notified to the outside. When both the first condition and the second condition are not satisfied, it is determined that there is a sign of failure, and an abnormal sign is notified to the outside. When at least one of the first condition and the second condition is satisfied, a warning is notified to the outside.

Advantages of the Invention

[0013] According to the optical receiver and the optical reception level determination method of the present invention, even when the optical reception level exceeds the threshold and there is no failure due to signal interruption, if the optical reception level is lower than the predicted optical reception level calculated by simulation, it is not determined as normal. In this way, when it is not determined as normal, it can be judged that there is a possibility of becoming abnormal at some point in the future. Therefore, by performing cleaning of the lens, replacement of the port accommodation card, etc. at that time, it becomes possible to prevent failures such as signal interruption.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but each drawing only schematically shows the present invention to the extent that it can be understood. Further, hereinafter, preferred configuration examples of the present invention will be described, but they are merely preferred examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications can be made without departing from the scope of the configuration of the present invention and achieving the effects of the present invention.

[0016] (Configuration) Referring to FIG. 1, a configuration example embodiment of the optical receiver of the present invention will be described. FIG. 1 is a schematic block diagram for explaining a configuration example of the optical receiver of the present invention.

[0017] The optical receiver 100 is, for example, for optical communication performed by connecting between buildings with a plurality of optical fibers 300 It is used for communication. Here, an example will be described in which one station building is equipped with an optical transmitter 200 and the other station building is equipped with an optical receiver 100. Also, as the plurality of optical fibers 300, a plurality of single-core optical fibers may be used, or a multi-core optical fiber may be used. Here, it is assumed that an optical fiber with n (n is an integer of 2 or more) cores is used.

[0018] The optical receiver 100 includes an optical receiving unit 10, a holding unit 20, an attenuation amount acquisition unit 30, a degradation amount acquisition unit 40, a determination unit 50, and a notification unit 60.

[0019] The optical receiving unit 10 receives an optical signal for each optical fiber and acquires the optical reception level for each optical fiber from the received optical signal. For example, when using a multi-core optical fiber, it can be configured such that the optical fibers are respectively connected to a plurality of ports of one optical receiving unit. On the other hand, when using a plurality of single-core optical fibers, optical receiving units corresponding to the number of optical fibers can be prepared, and each optical receiving unit can be configured such that one optical fiber is connected thereto. The first to nth optical reception levels RCV_L1 to n respectively acquired 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.

[0020] The optical receiving unit 10 is configured using any suitable conventionally known technology. For the holding unit 20, the attenuation amount acquisition unit 30, the degradation amount acquisition unit 40, the determination unit 50, and the notification unit 60, it is only necessary to be able to realize the functions described later, and those skilled in the art can configure them using any suitable conventionally known technology.

[0021] The holding unit 20 holds, as necessary, a threshold value MIN_L, predicted optical reception levels SIM_L1 to n, and normal-time optical reception levels RVOK_L1 to n. The storage in the holding unit 20 can be configured to be performed by operating any suitable input means provided in the optical receiver 100.

[0022] This threshold value MIN_L is a value that indicates the minimum reception level of the optical receiver 10, which is predetermined. This threshold value MIN_L is used to determine a signal break, similar to the conventionally known technology. Note that the threshold value MIN_L does not have to match the minimum reception level of the optical receiver 10 and may have a margin. Also, here, the threshold value MIN_L is described as a common value for each port to which the first to nth optical fibers are input, but different threshold values may be used for each port.

[0023] The predicted optical reception levels SIM_L1~n are the optical reception levels for each optical fiber calculated in advance by simulation. This simulation is performed in consideration of the distance between stations, the characteristics of the optical fiber, the routing devices through which the optical signals transmitted between stations pass, etc., and calculates a value close to the actual optical reception level. The prediction of the optical reception level by this simulation itself can be performed using existing technology.

[0024] The optical transmitter 200 notifies the optical receiver 100 of the optical transmission levels SND_L1~n in the optical transmitter 200. The optical transmission levels SND_L1~n are given, for example, by the output setting levels of the optical transmitter 200. Alternatively, when the optical transmitter 200 measures the optical transmission level, the optical transmitter 200 may be configured to notify the optical receiver 100 of the measured value as the optical transmission level. Also, the notification to the optical receiver 100 may be directly made from the optical transmitter 200 to the optical receiver 100 via an arbitrarily suitable communication line, or the configuration may be such that the input means provided in the optical receiver 100 is operated to input the optical transmission levels SND_L1~n.

[0025] 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 it is not limited to this. When the optical transmitter 200 measures the optical transmission levels SND_L1~n, etc., the optical transmission levels SND_L1~n may be directly sent to the attenuation amount acquisition unit 30 without passing through the holding unit 20.

[0026] The attenuation amount acquisition unit 30 acquires attenuation amounts RCV_D1 to n for each optical fiber. The attenuation amounts RCV_D1 to n are respectively given by the differences between the optical transmission levels SND_L1 to n for each optical fiber on the optical transmitter 200 side and the optical reception levels RCV_L1 to n for each optical fiber on the optical receiver 100 side.

[0027] The degradation amount acquisition unit 40 acquires degradation amounts DIFF_L1 to n. The degradation amounts DIFF_L1 to n are given by the differences between the normal-time optical reception levels RVOK_L1 to n and the current optical reception levels RCV_L1 to n. The normal-time optical reception levels RVOK_L1 to n are the optical reception levels measured by the optical reception unit 10 during normal times. The normal-time optical reception levels RVOK_L1 to n are measured at the time of constructing the optical communication network or the like and are held in the holding unit.

[0028] The degradation amounts DIFF_L1 to n are set to take positive values when the attenuation amount is larger than that during normal times. That is, the degradation amount DIFF_Lk (k is an integer from 1 to n) is given by RVOK_Lk - RCV_Lk.

[0029] The determination unit 50 includes, for example, a signal interruption determination means 52, an abnormality determination means 54, a first determination means 56 as an abnormality omen determination means, and a second determination means.

[0030] The signal interruption determination means 52 determines whether the optical reception levels RCV_L1 to n are equal to or lower than a threshold value MIN_L. When the signal interruption determination means 52 determines that the optical reception levels RCV_L1 to n are equal to or lower than the threshold value MIN_L, it determines that there is a signal interruption. In this case, the notification unit 60 notifies an external party such as an operator of the signal interruption notification via an arbitrarily suitable output means. This signal interruption determination means 52 is configured by an arbitrarily suitable conventionally known technique.

[0031] The abnormality determination means 54 determines the presence or absence of an abnormality when the signal interruption determination means 52 determines that the optical reception levels RCV_L1 to n are larger than the threshold value MIN_L.

[0032] The abnormality determination means 54 determines whether the optical reception levels RCV_L1~n are equal to or higher than the predicted optical reception levels SIM_L1~n. When the optical reception levels RCV_L1~n are equal to or higher than the predicted optical reception levels SIM_L1~n, the abnormality determination means 54 determines that it is normal. In this case, the notification unit 60 notifies the outside such as an operator that the reception is normal as necessary. When designed normally, since the predicted optical reception levels SIM_L1~n are values that can be received by the optical reception unit 10, the predicted optical reception levels SIM_L1~n are values equal to or higher than the threshold value MIN_L.

[0033] Here, when the optical reception levels RCV_L1~n are equal to or higher than the threshold value MIN_L and lower than the predicted optical reception levels SIM_L1~n, that is, when MIN_L≦RCV_L1~n<SIM_L1~n is satisfied, it has been conventionally determined to be normal, but there may be an abnormality.

[0034] Therefore, the first determination means 56 and the second determination means 58 as the abnormal sign determination means determine the presence or absence of an abnormal sign when the optical reception levels RCV_L1~n are lower than the predicted optical reception levels SIM_L1~n.

[0035] The first determination means 56 determines whether the attenuation amounts RCV_D1~n in the selected optical fiber satisfy a first condition that they are equal to or less than a value near the minimum value of the attenuation amounts for all optical fibers. Here, the value near the minimum value of the attenuation amounts RCV_D1~n for all optical fibers is a value obtained by adding a margin A considering fluctuations and errors to the minimum value Min(RCV_D1~n) of the attenuation amounts 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.

[0036] For example, when the minimum value of the attenuation amounts RCV_D1~n is 2 dB and the margin A is 3 dB, if the attenuation amount RCV_Dk for the k-th optical fiber does not satisfy the first condition of being 5 dB or less, it is determined that the attenuation is large compared to other optical fibers.

[0037] The second determination means 58 determines whether or not the second condition that the degradation amounts DIFF_L1 to n are equal to or less than a predetermined value B is satisfied. This predetermined value B is set in consideration of variations 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.

[0038] For example, when the predetermined value B is set to 2 dB, if the second condition that the degradation amounts DIFF_L1 to n are less than 2 dB is not satisfied, it is determined that the attenuation is larger than that at the initial normal time.

[0039] As described above, when neither the first condition nor the second condition is satisfied, it indicates that the signal attenuation is larger than that of other optical fibers and the condition has deteriorated compared to the previous state. In this case, the notification unit 60 notifies an alarm of an abnormal sign to the outside, such as an operator, as there is a sign of a failure. As a cause of this predicted failure, for example, an increase in attenuation due to dirt on the fiber lens can be considered.

[0040] When this alarm of an abnormal sign is notified, it can be determined that there is a possibility of becoming abnormal at some point. Therefore, by performing lens cleaning, port accommodation card replacement, etc. when the alarm of an abnormal sign is notified, it becomes possible to prevent failures such as signal interruption.

[0041] Note that when at least one of the first condition and the second condition is satisfied, a configuration may be adopted in which the notification unit 60 issues a notification for calling attention.

[0042] (Operation) Referring to FIG. 2, the optical reception level determination method will be described. FIG. 2 is a diagram for explaining the optical reception level determination method and shows the processing flow of the optical receiver.

[0043] First, in the holding process of step 10 (hereinafter, steps are denoted as S), initial conditions are set. In S10, the predicted optical reception levels SIM_L1~n calculated in advance, a predetermined threshold value MIN_L, a margin A, a 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 or the like.

[0044] Next, in the optical reception process S20, an optical signal is received for each optical fiber, and the optical reception levels RCV_L1~n for each optical fiber are acquired from the received optical signal.

[0045] Next, in the determination process of S30, the optical reception level is determined. Here, the determination using the optical reception level RCV_L1 for the first optical fiber will be described. The determination for the second to nth optical fibers can be performed in the same manner as the determination for the first optical fiber, so the description is omitted.

[0046] The result of the determination in the determination process of S30 is notified in the notification process S40.

[0047] The determination process S30 further includes a signal interruption determination process S31, an abnormality determination process S32, a first determination process S33, and a second determination process S34.

[0048] In the determination process S30, first, the signal interruption determination process S31 is performed. The signal interruption determination process S31 determines whether the optical reception level RCV_L1 for the first optical fiber is less than or equal to the threshold value MIN_L, that is, whether RCV_L1≦MIN_L is satisfied.

[0049] As a result of the determination in the signal interruption determination process S31, if the optical reception level RCV_L1 is less than or equal to the threshold value MIN_L (in the case of Yes), it is determined that there is a signal interruption. When it is determined that there is a signal interruption, a signal interruption is notified in the notification process S40a.

[0050] If, as a result of the determination in the signal interruption determination process S31, the optical reception level RCV_L1 is greater than the threshold value MIN_L (in the case of No), subsequently, the abnormality determination process S32 is performed.

[0051] In the abnormality determination process S32, it is determined whether the optical reception level RCV_L1 is greater than or equal to the predicted optical reception level SIM_L1, that is, whether the condition RCV_L1 ≧ SIM_L1 is satisfied.

[0052] If, as a result of the determination in the abnormality determination process S32, the optical reception level RCV_L1 is greater than or equal to the predicted optical reception level SIM_L1 (in the case of Yes), it is determined to be normal. When it is determined to be normal, if necessary, in the notification process S40b, it is notified that it is normal.

[0053] If, as a result of the determination in the abnormality determination process S32, the optical reception level RCV_L1 is lower than the predicted optical reception level SIM_L1 (in the case of No), subsequently, the first determination process S33 is performed.

[0054] In the first determination process S33, the attenuation amount 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 satisfies the first condition that it is less than or equal to a value near the minimum value of the attenuation amounts for all optical fibers, that is, RCV_D1 ≦ Min(RCV_D1 to n) + A.

[0055] If, as a result of the determination in the first determination process S33, the first condition is not satisfied (No), subsequently, the second determination process S34 is performed.

[0056] In the second determination process 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 satisfies the second condition that it is less than or equal to a predetermined value B, that is, DIFF_L1 ≦ B.

[0057] If, as a result of the determination in the second determination process S34, the second condition is not satisfied (No), it is determined that there is a sign of failure. When it is determined that there is a sign of failure, in the notification process S40c, an alarm for the sign of failure is notified.

[0058] On the other hand, when it is determined in the first determination process S33 that the first condition is satisfied (Yes) and when it is determined in the second determination process S34 that the second condition is satisfied (Yes), if necessary, in the notification process S40d, a notice for calling attention is given.

[0059] According to the optical receiver and the optical reception level determination method of the present invention, even when the optical reception level exceeds the threshold value and there is no failure due to signal interruption, when the optical reception level is lower than the predicted optical reception level calculated by simulation, it is not determined as normal. In this way, when it is not determined as normal, it can be determined that there is a possibility of becoming abnormal at some point. Therefore, by performing cleaning of the lens, replacement of the port accommodation card, etc. at that time, it becomes possible to prevent failures such as signal interruption in advance.

Explanation of Reference Numerals

[0060] 10 Optical reception unit 20 Holding unit 30 Attenuation amount acquisition unit 40 Deterioration amount acquisition unit 50 Determination unit 52 Signal interruption determination means 54 Abnormality determination means 56 First determination means 58 Second determination means 60 Notification unit 100 Optical receiver 200 Optical transmitter 300 Optical fiber

Claims

A photoreceiver that receives an optical signal from an optical transmitter via a plurality of optical fibers, comprising: a photoreceiving unit that obtains the optical reception level for each optical fiber from the received optical signal; a holding unit that holds a threshold value based on the minimum reception level of the photoreceiving unit and a predicted optical reception level, which is the optical reception level for each optical fiber calculated in advance by simulation; a determination unit that determines whether the optical reception level of an optical fiber whose optical reception level is equal to or higher than the threshold value is equal to or higher than the predicted optical reception level, and determines that it is normal when the optical reception level is equal to or higher than the predicted optical reception level; an attenuation amount acquisition unit that obtains an attenuation amount as the difference between the optical transmission level for each optical fiber on the optical transmitter side and the optical reception level; a notification unit; wherein the holding unit further holds a normal-time optical reception level, which is the optical reception level measured during normal operation; the determination unit determines whether a first condition that the attenuation amount in the selected optical fiber is less than or equal to a value near the minimum value of the attenuation amounts in all optical fibers is satisfied, and whether a second condition that the difference between the normal-time optical reception level and the optical reception level is less than or equal to a predetermined value is satisfied. Further, when neither the first condition nor the second condition is satisfied, it is determined that there is a sign of failure; the notification unit notifies the outside of a signal interruption when the optical reception level is lower than the threshold value, notifies the outside of an abnormal sign when neither the first condition nor the second condition is satisfied, and notifies the outside of a warning when at least one of the first condition and the second condition is satisfied; a photoreceiver characterized by the above.

2. An optical reception level determination method performed by a photoreceiver that receives an optical signal from an optical transmitter via a plurality of optical fibers, comprising: a holding process of holding a first threshold value and a predicted optical reception level, which is the optical reception level for each optical fiber calculated in advance by simulation; a photoreceiving process of receiving an optical signal for each optical fiber and obtaining the optical reception level for each optical fiber from the received optical signal; a determination process of determining whether the optical reception level of an optical fiber whose optical reception level is equal to or higher than the first threshold value is equal to or higher than the predicted optical reception level, and determining that it is normal when the optical reception level is equal to or higher than the predicted optical reception level; an attenuation amount acquisition process of obtaining an attenuation amount as the difference between the optical transmission level for each optical fiber on the optical transmitter side and the optical reception level; a notification process; wherein the first threshold value is a threshold value based on the minimum reception level of the photoreceiver. In the holding process, the normal light reception level, which is the light reception level measured during normal operation, is further held. The determination process further includes a first determination process for determining whether or not a first condition that the attenuation amount in the selected optical fiber is equal to or less than a value near the minimum value of the attenuation amounts in all optical fibers is satisfied; a second determination process for determining whether or not a second condition that the difference between the normal light reception level and the light reception level is equal to or less than a predetermined value is satisfied and has In the notification process, when the light reception level is lower than the first threshold value, a signal interruption is notified to the outside. When both the first condition and the second condition are not satisfied, it is determined that there is a sign of failure, and an abnormality sign is notified to the outside. When at least one of the first condition and the second condition is satisfied, a warning is notified to the outside. A method for determining a light reception level, characterized by the above.

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