JP4297348B2 - Light output cutoff control device - Google Patents

Description

  The present invention relates to a light output cutoff control device that is used in a wavelength division multiplexing communication system and performs control to cut off light output under a predetermined condition in order to prevent radiation of light output that causes danger to a human body from an open end.

  Conventionally, in an optical communication system using a high-power optical amplifier, in order to maintain safety against laser output from the optical amplifier, the reflected return light is detected, and if this reflected return light is above a certain intensity, The output is shut down or lowered to a safe level.

  In particular, when the output connector is open, there is reflected return light (output -14 dB) attenuated by about 14 dB due to Fresnel reflection at the end of the connector. When the amount R is less than the threshold value Rth (R <Rth), it is determined that the reflection is abnormal, and the output from the optical amplifier is cut off. Note that a small return loss R means a large amount of reflected return light. Here, the threshold value Rth is set to, for example, around 16 dB, and is set slightly larger than Fresnel reflection (about 14 dB).

Japanese Patent Laid-Open No. 6-177837

  By the way, in a WDM communication system using an optical amplifier, optical signals of a plurality of wavelengths are multiplexed and output from an output terminal of an optical amplifier placed at a terminal station at the final stage. An optical demultiplexer is connected to the subsequent stage of the amplifier, and is demultiplexed into optical signals of each wavelength by this optical demultiplexer, and further output to an optical receiver in the subsequent stage. In this WDM communication system, not all wavelengths are set to be usable, and only some wavelengths (channels) are set and operated first, and channels of other wavelengths may be added later. is there.

  FIG. 10 shows a schematic configuration of a conventional WDM communication system. In this WDM communication system, an optical multiplexer MUX and an optical demultiplexer DEMUX are connected by a span of three optical fibers, and a booster amplifier B-OFA is connected between the optical multiplexer MUX and the first span. The in-line amplifier I-OFA is connected between the spans, and the preamplifier P-OFA is connected between the last span and the optical demultiplexer DEMUX. An optical transmitter corresponding to each wavelength is connected to the preceding stage of the optical multiplexer MUX, and an optical receiver corresponding to each wavelength is connected to the subsequent stage of the optical demultiplexer DEMUX. Here, when the optical transmitter TX1 and the optical receiver RX1 corresponding to the channel “1” are already connected and the optical transmitter TX2 and the optical receiver RX2 corresponding to the channel “2” are added, Generally, since the input range in which the receiver can receive light is limited, it is necessary to adjust the optical output of the optical demultiplexer DEMUX using an attenuator ATT or the like. When this adjustment is performed, since the output end of the optical demultiplexer DEMUX of the channel “2” is an open end, Fresnel reflection occurs at this open end, and the preamplifier P-OFA shuts down due to this reflection. As a result, there is a problem that the channel “1” of the existing wavelength is blocked.

Here, specifically, the reflection threshold Rth of the return loss R at which the preamplifier P-OFA blocks the light output is set to 16 dB, the loss of the optical demultiplexer DEMUX is set to 0, and the return loss due to Fresnel reflection is set to 14 dB. Think about the case. First, when the output of the preamplifier P-OFA is equal to each channel, the output of the existing channel “1” and the additional channel “2” are both P0. / 2 (−3 dB), it returns with Fresnel reflection (−14 dB) at the maximum, so the return loss R measured at the output terminal of the preamplifier P-OFA is R = 3 + 14 = 17 dB> Rth, and light The output is not shut off. On the other hand, when the output of the preamplifier P-OFA is not equal to each channel and there is an inter-channel deviation in which the output P2 of the channel “2” is 3 dB larger than the output P1 of the channel “1”, the output of each channel is Pi ( If dBm, i = 1, 2), P1 = P0 (dBm), and P2 = P0 + 3 (dBm). At this time, if the total output for two channels is Pt (dBm),
Pt = ₁₀ log ₁₀ (10 ^{P0 / 10} +10 ^{(P0 + 3) / 10} )
= P0 + 4.8 (dBm)
It becomes. Since the return light from the open end of the channel “2” is P2-14 = P0-11 (dBm), even if it is assumed that there is no reflection from other channels, the return loss R for the total output Pt is ,
R = Pt− (P0-11)
= 15.8 dB
<Rth
Thus, the preamplifier P-OFA is shut off.

  That is, in this case, when the channel is added, the preamplifier P-OFA is shut off by the return light from the optical demultiplexer DEMUX of the added channel “2”, thereby shutting off the existing channel “1” and forcibly communicating. It becomes impossible. In particular, the output of the preamplifier P-OFA installed at the last stage of the multistage relay system using optical amplifiers usually has an inter-channel deviation of about 3 dB due to the accumulation of gain tilt of the optical amplifier. There was a problem that the light output sometimes cut off.

  On the other hand, when the first first wave (channel “1”) is connected as shown in FIG. 11, light is put into the optical multiplexer MUX from the optical transmitter, and each part is sequentially arranged from the upstream side, that is, the booster amplifier B-OFA. Generally, the system is started up while adjusting the optical input of the light using an optical attenuator or the like. Even in this case, each optical amplifier is often an open end for output measurement, and in the case of an optical amplifier that cuts off the optical output due to a reflection abnormality as in the conventional case, the output measurement of each optical amplifier is performed. Each time the optical amplifier is cut off, it must be restored each time, and there is a problem that the working efficiency is lowered.

  The present invention has been made in view of the above, and is capable of avoiding the interruption of existing channels when adding channels in a WDM communication system, and maintaining the safety of optical output, and working efficiency at system startup. An object of the present invention is to provide a light output cutoff control device capable of increasing the power.

  In order to solve the above-mentioned problems and achieve the object, the present invention is used in a wavelength division multiplexing communication system, and cuts off the light output under a predetermined condition in order to prevent the radiation of the light output that poses a danger to the human body from the open end. A light output shut-off control device that performs control, comprising: a shut-off control unit that performs control to shut off the light output when the light output exceeds a predetermined output threshold and the reflection attenuation amount is less than the predetermined reflection threshold. It is characterized by that.

  Moreover, this invention is provided with the alerting | reporting means which alert | reports that abnormality generate | occur | produced in said invention, The said interruption | blocking control means uses the said alerting | reporting means when the said return loss is less than a predetermined reflection threshold value. It is characterized by notifying that an abnormality has occurred.

  In the above invention, the output threshold value may be set to, for example, 10 dBm, 17 dBm, or 27 dBm according to the installation conditions of the apparatus.

  In the above invention, the start notification means for notifying the optical amplifier of the start of wavelength addition in the optical transmitter using the monitoring communication of the wavelength division multiplexing communication system, and the reception of the wavelength in the optical receiver using the monitoring system Confirmation notification means for notifying the optical amplifier of confirmation, and the cutoff control means is a control that does not operate the optical output cutoff function between the notification of the start of wavelength addition by the start notification means and the notification of light reception confirmation by the confirmation notification means. It is characterized by performing.

  Further, the present invention is an optical output cutoff control device which is used in a wavelength division multiplexing communication system and performs control to cut off optical output under a predetermined condition in order to prevent radiation of optical output that causes danger to the human body from an open end, Start notifying means for notifying the optical amplifier of the start of wavelength addition in the optical transmitter using the monitoring system communication of the wavelength division multiplexing communication system, and notifying the optical amplifier of the reception of the wavelength in the optical receiver using the monitoring system A confirmation notification means; and an operation control means for performing control so as not to operate the light output blocking function between the notification of the start of wavelength addition by the start notification means and the notification of the light reception confirmation by the confirmation notification means. And

  According to this invention, the blocking control means performs the control to block the light output when the light output exceeds the predetermined output threshold and the reflection attenuation amount is less than the predetermined reflection threshold. With a simple configuration and with certainty and freedom of design, it is possible to avoid blocking existing channels when adding channels and to maintain the safety of optical output.

  In addition, since the operation control means or the cutoff control means performs control so as not to operate the optical output cutoff function from the notification of the start of wavelength addition by the start notification means to the notification of light reception confirmation by the confirmation notification means. There is an effect that it is possible to increase the working efficiency by eliminating frequent interruption at the time of start-up.

  Embodiments of a light output cutoff control device according to the present invention will be described below with reference to the drawings.

(Embodiment 1)
1 is a diagram showing a schematic configuration of a WDM communication system including an optical output cutoff control apparatus according to Embodiment 1 of the present invention. In FIG. 1, this WDM communication system has three optical fiber spans L 1 to L 3 between an optical multiplexer 1 and an optical demultiplexer 2. A booster amplifier 11 is provided between the optical multiplexer 1 and the span L1, and in-line amplifiers 12 and 13 are provided between the spans L1, L2 and spans L2, L3. The span L3 and the optical demultiplexer 2 are provided. Is provided with a preamplifier 14. The booster amplifier 11, the in-line amplifiers 12 and 13, and the preamplifier 14 perform optical amplification according to their installation locations. Here, the optical transmitter TX1 having the wavelength λ1 is connected to the channel “1” of the optical multiplexer 1, and the optical receiver RX1 having the wavelength λ1 is connected to the channel “1” of the optical demultiplexer 2. Channel “1” is set. The optical attenuator ATT between the optical demultiplexer 2 and the optical receiver RX1 is an attenuator for adjusting to the input range of the optical receiver RX1. The optical transmitter TX2 and the optical receiver RX2 correspond to the channel “2” having the wavelength λ2 to be added.

  Here, the preamplifier 14 uses the attenuation amount measuring unit 21 that measures the reflection attenuation amount R with respect to the optical output of the amplifier 20, the output threshold value 24 (Pth), and the reflection threshold value 25 (Rth), and thereby the optical output of the amplifier 20. A blocking control unit 22 that controls the blocking of the output, a setting unit 23 that sets the output threshold value Pth and the reflection threshold value Rth, and a notification unit 26 that notifies when an output blocking occurs.

  Here, the light output cutoff control processing procedure by the cutoff controller 22 will be described with reference to the flowchart shown in FIG. In FIG. 2, the cutoff control unit 22 first determines whether or not the reflection attenuation amount R measured by the attenuation amount measurement unit 21 is smaller than a preset reflection threshold Rth (step S101). When the reflection attenuation amount R is smaller than the reflection threshold Rth (step S101, YES), a notification process 1 that is a reflection alarm indicating that the reflection attenuation amount R is abnormal is performed (step S102). The notification process 1 is, for example, to turn on an alarm lamp or LED, sound a buzzer, or notify the outside via a monitoring system.

  Thereafter, the cutoff control unit 22 determines whether or not the light output P is smaller than the output threshold value Pth (step S103). If the light output P is smaller than the output threshold value Pth (step S103, YES), the light output P An output blocking process for blocking the output is performed (step S104), and a notification process 2 to the effect that the light output is blocked is performed (step S105). The notification process 2 is to, for example, turn on an alarm lamp or LED, sound a buzzer, or notify the outside via a monitoring system, as in the notification process 1 described above. On the other hand, when the reflection attenuation amount R is larger than the reflection threshold value Rth (step S101, NO) and when the light output P is larger than the output threshold value Pth (step S103, NO), the process proceeds to step S101.

  As a result, even when the return loss R is small, if the light output P is small, the light output is not cut off, and the reflection threshold Rth is not set for each different channel addition state. Light output blocking processing can be performed. The notification state that has been subjected to the notification process is not canceled even if the light output is interrupted, and the administrator is surely notified that the light output has been interrupted.

  Further, the light output blocking process will be described in detail. First, the output threshold Pth = 10 dBm, the reflection threshold Rth = 16 dB, the reflection attenuation amount due to Fresnel reflection is 14 dB, the maximum value of the interchannel deviation is D (dB), the lower limit of loss of the optical demultiplexer 2 is Ld, and the channel The expansion is assumed to be performed one channel at a time. It is assumed that the outputs of the amplifiers 20 of all the existing channels are P0 (dBm) and only the extension channel is P0 + D (dBm). Further, P0 = 0 dBm (see FIG. 3).

Therefore, consider the case where the lower limit loss Ld = 0 (dB). In this case, the optical output of the existing channel is ₁₀ log ₁₀ Σ10 ^{Pi / 10} (dBm), and the total optical output is
Pt = ₁₀ log ₁₀ Σ10 ^{Pi / 10} + D (dBm)
It becomes. While the optical demultiplexer output of the extension channel is open, if the loss of the optical demultiplexer is set to 0, a 14 dB down reflection return occurs from this open end by Fresnel reflection, and the value is r = D -14 (dBm). Therefore, the return loss R measured by the attenuation measurement unit 21 is
R = Pt-r
= ₁₀ log ₁₀ Σ10 ^{Pi / 10} +14 (dB)
It becomes. This result is as shown in FIG. 4, and the maximum inter-channel deviation D dependency of the return loss R detected at the output terminal of the amplifier 20 as shown in FIG. 5 is obtained. In FIG. 5, the return loss R decreases as the maximum inter-channel deviation D increases, and the return loss R increases as the number of existing channels at the time of expansion increases.

  As a result, for each stage (pattern) of channel addition, the maximum inter-channel deviation threshold value Dth is obtained, in which the amplifier 20 is not blocked as a reflection abnormality, that is, R ≧ Rth = 16 dB. FIG. 6 shows the result of obtaining the maximum inter-channel deviation threshold Dth at each stage based on FIG.

  Usually, the output of the amplifier 20 (preamplifier 14) is smaller than that of the booster amplifier 11 and the inline amplifiers 12 and 13, and is often 10 dBm or less up to three waves. In this case, when the output threshold value Pth is set to 10 dBm, the amplifier 20 is not shut off because of P ≦ Pth even if R <Rth in the extension from 1ch → 2ch, 2ch → 3ch. Therefore, it is only necessary to consider that R <Rth is not satisfied only in each stage after 3ch → 4ch. In this case, from FIG. 6, if the maximum inter-channel deviation D is D <7.0 dB, the output is not cut off.

  Here, if the output cutoff is controlled only by the reflection threshold Rth without setting the output threshold Pth shown in the first embodiment, it is necessary to consider R <Rth even in the case of 1ch → 2ch. In this case, the maximum inter-channel deviation D is D <2.3 dB from FIG.

  In general, in a multi-stage relay system using optical amplifiers, it is difficult to make the interchannel deviation of the output of the preamplifier 14 disposed in the final stage within 2.3 dB. To achieve this, the gain tilt is corrected for each optical amplifier. It is necessary to mount a mechanism for reducing the cost and reliability.

  Here, in the first embodiment, the maximum channel-to-channel deviation D <7 dB can be set, and the output cutoff function at each expansion stage can be performed with a simple configuration and simple processing without providing the above-described gain tilt mechanism. Can be controlled.

Next, a case where the loss lower limit Ld of the optical demultiplexer 2 is a finite value will be considered. The reflection attenuation in this case is r = D-14-2Ld (dBm), and the reflection attenuation amount R is
R = Pt-r
= ₁₀ log ₁₀ Σ10 ^{Pi / 10} + 14 + 2 Ld (dB)
It becomes. In this case, if 2Ld ≧ 2 (dB), that is, Ld ≧ 1, the output is not shut off regardless of the maximum channel deviation D. That is, assuming that 2Ld = 1 (dB) (Ld = 0.5 (dB)), the reflection threshold Rth in FIG. 5 is lowered by 1 dB, which is the same as Rth = 15 dB. As a result, the maximum inter-channel deviation Dth at each stage as shown in FIG. 7 is obtained.

  Even in this case, assuming that the output of the preamplifier 14 is up to 3 dBm and the optical output is 10 dBm or less, Pth = 10 dBm is set, and R <Rth in the extension stage from 1ch → 2ch, 2ch → 3ch. However, since P ≦ Pth is satisfied, the output of the amplifier 20 is not shut off. Therefore, as in the case of the loss lower limit Ld = 0 dB, in order to prevent the output from being cut off after 3ch → 4ch and R ≧ Rth, the maximum inter-channel deviation is set to D <10.5 dB from FIG. It will be good. In this case, the value of the maximum inter-channel deviation D can be greatly earned.

  The setting unit 23 can set various parameters including the output threshold value Pth and the reflection threshold value Rth. The setting unit 23 may be provided outside the optical multiplexer 1 so that setting control can be performed using the monitoring system of the WDM communication system.

  The output threshold Pth described above is 10 dBm, but this 10 dBm can be regarded as a safe output within the class 1 AEL defined by IEC-60825-1. Therefore, for example, the output threshold Pth may be set to 17 dBm corresponding to the Class 3R AEL, or may be set to 27 dBm corresponding to the Class 3B AEL.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the second embodiment, the light output is not frequently interrupted when the first wave is set, thereby preventing the work efficiency from being lowered.

  FIG. 8 is a diagram showing a schematic configuration of a WDM communication system including an optical output cutoff control device according to Embodiment 2 of the present invention. In FIG. 8, the WDM communication system includes a start notification unit 31 that notifies the print amplifier 14 of the start of wavelength extension of the optical transmitter TX1 using the existing monitoring system of the WDM communication system in the optical transmitter TX1. The optical receiver RX1 also has a confirmation notification unit 32 for notifying light reception confirmation of the optical receiver RX1 using the monitoring system, and the cutoff control unit 42 notifies the start of wavelength addition from the start notification unit 31. The light output blocking function described above is not operated until the light reception confirmation notification from the confirmation notification unit 32 is received. Other configurations are the same as those of the first embodiment.

  Here, with reference to FIG. 9, the light output interruption | blocking control processing procedure by the interruption | blocking control part 42 is demonstrated. In FIG. 9, the cutoff control unit 42 first determines whether or not a wavelength extension start notification has been received from the start notification unit 31 (step S <b> 201). When the notification of the start of wavelength extension is received (step S201, YES), the operation of the optical output blocking function shown in the first embodiment is stopped (step S202).

  Thereafter, it is further determined whether or not there is a reception confirmation notification from the confirmation notification unit 32 (step S203). When there is a notification of reception confirmation (step S203, YES), the operation of the light output blocking function that has been stopped is resumed (step S204), and this process is terminated.

  In addition, it is good to make the interruption | blocking control part 42 mentioned above have all the amplifiers, ie, the booster amplifier 11, and the in-line amplifiers 12 and 13. This is because, in the case of the initial rise of the first wave, the optical input of each part in the optical amplifier is adjusted sequentially from the upstream side using an attenuator or the like, and at that time, it often becomes an open end.

  As a result, the working efficiency of the light input adjustment can be significantly improved particularly at the initial startup.

  As described above, the optical output cutoff control device according to the present invention is particularly useful for a WDM communication system and is suitable for control when a new channel is added.

It is a figure which shows schematic structure of the WDM communication system containing the optical output cutoff control apparatus which is Embodiment 1 of this invention. It is a flowchart which shows the light output interruption | blocking control processing procedure of the interruption | blocking control part shown in FIG. It is a figure explaining an additional pattern. It is a figure which shows the calculation result of the return loss amount in consideration of the largest channel deviation D for every extension pattern. FIG. 5 is a graph showing the calculation results obtained in FIG. 4. It is a figure which shows the maximum channel deviation threshold value Dth for every extension pattern when the loss of an optical demultiplexer is 0 dB. It is a figure which shows the maximum channel deviation threshold value Dth for every extension pattern in case the loss of an optical demultiplexer is 0.5 dB. It is a figure which shows schematic structure of the WDM communication system containing the optical output cutoff control apparatus which is Embodiment 2 of this invention. It is a flowchart which shows the light output interruption | blocking control processing procedure of the interruption | blocking control part shown in FIG. It is a figure explaining the channel expansion in the conventional WDM communication system. It is a figure explaining the addition of the first 1 wave in the conventional WDM communication system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical multiplexer 2 Optical demultiplexer 11 Booster amplifier 12, 13 In-line amplifier 14 Preamplifier 20 Amplifier 21 Attenuation measuring part 22, 42 Cut-off control part 23 Setting part 24 Output threshold value (Pth)
25 Reflection threshold (Rth)
26 Notification Unit 31 Start Notification Unit 32 Confirmation Notification Unit TX1, TX2 Optical Transmitter RX1, RX2 Optical Receiver

Claims (5)

A light output cutoff control device that is used in a wavelength division multiplexing communication system and performs control to cut off the light output under a predetermined condition in order to prevent radiation of light output that causes danger to the human body from the open end,
An optical output cutoff control device comprising: cutoff control means for performing control to cut off optical output when the optical output exceeds a predetermined output threshold and the reflection attenuation amount is less than the predetermined reflection threshold. Informing means for informing that an abnormality has occurred,
2. The light output cutoff control device according to claim 1, wherein when the reflection attenuation amount is less than a predetermined reflection threshold, the cutoff control unit causes the notification unit to notify that an abnormality has occurred. .   The light output cutoff control device according to claim 1, wherein the output threshold is set to any one of 10 dBm, 17 dBm, and 27 dBm. Start notifying means for notifying the optical amplifier of the start of wavelength extension in the optical transmitter using the monitoring communication of the wavelength multiplexing communication system;
Confirmation notifying means for notifying the optical amplifier of the reception of the wavelength in the optical receiver using the monitoring system;
The said cutoff control means performs control which does not operate an optical output cutoff function from the notification of the wavelength addition start by the said start notification means to the notification of the light reception confirmation by the said confirmation notification means. The light output cutoff control device according to any one of the above. A light output cutoff control device that is used in a wavelength division multiplexing communication system and performs control to cut off the light output under a predetermined condition in order to prevent radiation of light output that causes danger to the human body from the open end,
Start notifying means for notifying the optical amplifier of the start of wavelength extension in the optical transmitter using the monitoring communication of the wavelength multiplexing communication system;
Confirmation notifying means for notifying the optical amplifier of the reception of the wavelength in the optical receiver using the monitoring system;
Operation control means for performing control not to operate the light output shut-off function between the notification of the start of wavelength addition by the start notification means and the notification of light reception confirmation by the confirmation notification means;
A light output cutoff control device comprising:

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