JP2008141674A - Wavelength multiplex transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a wavelength multiplex transmission apparatus which improves apparatus reliability without using an optical switch in which there is a possibility of occurrence of a fault. <P>SOLUTION: The wavelength multiplex transmission apparatus comprises: dummy light sources 3a1, 3a2 for outputting to a dummy light output unit 2-a dummy light having central wavelengths λa1, λa2 proximate to a set central wavelength λa; a photocoupler 4a for multiplexing the dummy light having the central wavelengths λa1, λa2; and a dummy light source control unit 6a for measuring a light output level of the multiplexed dummy light and controlling light output levels of the dummy light sources 3a1, 3a2 so that the measured light output level becomes a predetermined value. The photocoupler 4a is a passive component for which mechanical and electrical control is not needed, differently from the optical switch and probability of fault occurrence is so small as to be ignored. Consequently, a redundant system with extremely high reliability for the dummy light sources can be configured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wavelength division multiplexing transmission apparatus used for optical communication.

  In a wavelength division multiplexing transmission apparatus used for optical communication, ASE light (amplified spontaneous emission) is input to a free wavelength as dummy light when operated at a wavelength number less than the maximum number of wavelengths to be designed. The This is to prevent the phenomenon that, when there is no dummy light, the power input to the optical amplifier on the optical transmission line is lower than the design value and the SN ratio (signal-to-noise ratio) of the optical amplifier output is deteriorated.

  As an example of the wavelength division multiplexing transmission device in the prior art, a plurality of signal light transmitting units that output signal lights having different center wavelengths and a plurality of dummy that output dummy lights having different center wavelengths from the plurality of signal lights A light source, an optical multiplexer that multiplexes dummy lights output from a plurality of dummy light sources, a plurality of optical amplifiers that respectively amplify signal lights output from a plurality of signal light transmitters, and a wavelength from the optical multiplexer An optical amplifier that amplifies the multiplexed dummy light, an optical multiplexer that combines the signal light amplified by the plurality of optical amplifiers and the wavelength multiplexed dummy light, and a demultiplexer that demultiplexes the wavelength multiplexed light from the optical multiplexer; The optical monitor unit for measuring the optical output level of the wavelength multiplexed light demultiplexed by the demultiplexer and the optical output level measured by the optical monitor unit so that the optical output level is the same as when operating at the maximum number of wavelengths. Multiple dummy lights There is provided with a control unit for controlling the optical amplifier to the width, an optical amplifier to be transmitted to the optical transmission path amplifies the wavelength-multiplexed light that has passed through the demultiplexer (e.g., see Patent Document 1).

  In such a wavelength division multiplexing transmission apparatus, dummy light has an important role of maintaining the S / N ratio of an optical signal to be transmitted, so that a redundant configuration is generally adopted. As a general redundant configuration of dummy light sources, a monitor circuit that detects a failure of dummy light output from two dummy light sources and a connection circuit connected to the output lines of the two dummy light sources, and a failure is detected by the monitor circuit And an optical switch that selects and outputs normal dummy light.

JP 2002-353939 A

  Since conventional wavelength division multiplexing transmission devices are configured as described above, optical switches are used for redundant configuration of dummy light. However, optical switches are mechanically or electrically operated components that fail. When a malfunction that does not operate due to the occurrence of the dummy light is lost, the optical signal is seriously deteriorated. In addition, even if an optical switch malfunction is detected, replacement of the optical switch is necessary for recovery, and thus there is a problem that the operation of the apparatus cannot be continued because it becomes inevitable that the dummy light is cut off. It was.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a wavelength division multiplex transmission apparatus that improves the reliability of the apparatus without using an optical switch that may cause a failure. .

  In the wavelength division multiplexing transmission apparatus according to the present invention, a dummy light output unit combines a plurality of dummy light sources that output dummy light close to the set center wavelength, and an optical coupler that combines the plurality of dummy lights. And a dummy light source control unit for controlling the light output levels of the plurality of dummy light sources so that the measured light output level becomes a predetermined value.

According to the present invention, the dummy optical power level of the dummy light combined by the optical coupler is measured, and the dummy light output level is controlled so that the measured light output level becomes a predetermined value. Since the light source control unit is provided, even if some of the dummy light sources out of the plurality of dummy light sources break down, the optical couplers combine them by controlling to increase the light output level of other normal dummy light sources. The optical output level of the dummy light thus set can be set to a predetermined value, and the operation of the apparatus can be continued.
In addition, since an optical coupler that combines dummy lights output from multiple dummy light sources is provided, the optical coupler is a passive component that does not require mechanical and electrical control unlike an optical switch, causing a failure. The probability of doing so is negligible. Therefore, the effect that a highly reliable redundant system can be configured for the dummy light source can be obtained.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a wavelength division multiplexing transmission apparatus according to Embodiment 1 of the present invention. In the figure, signal light transmitters 1-1 to 1-n (n is an arbitrary natural number) have different center wavelengths λ1. Each of the signal lights having .about..lamda.n is output.
The dummy light output units 2-a and 2-b are ASE lights having center wavelengths λa and λb different from the center wavelengths λ1 to λn of the signal lights output from the signal light transmitters 1-1 to 1-n, respectively. Are output as dummy lights, respectively.

  In the dummy light output unit 2-a, the dummy light sources 3a1 and 3a2 have center wavelengths λa1 and λa2 that are different from each other in a symmetrical manner with respect to the center wavelength λa set in the dummy light output unit 2-a, and The dummy lights that are close enough to prevent interference between wavelengths are output. The maximum value of the light output level of each of the dummy light sources 3a1 and 3a2 can output more than twice the value assumed in normal operation. The optical coupler 4a combines the dummy lights output from the dummy light sources 3a1 and 3a2. The demultiplexer 5a demultiplexes the dummy light combined by the optical coupler 4a. The dummy light source controller 6a measures the light output level of the dummy light demultiplexed by the demultiplexer 5a, and the dummy light sources 3a1 and 3a2 so that the measured light output level becomes a predetermined value set in advance. A control signal for controlling the light output level of the light is output.

  Similarly, in the dummy light output unit 2-b, the dummy light sources 3b1 and 3b2 have center wavelengths λb1 and λb2 that are symmetrically different from each other about the center wavelength λb set in the dummy light output unit 2-b. In addition, dummy lights that are close enough to prevent interference between wavelengths can be output. The maximum value of the light output level of each of the dummy light sources 3b1 and 3b2 can output more than twice the value assumed in normal operation. The optical coupler 4b combines the dummy lights output from the dummy light sources 3b1 and 3b2. The demultiplexer 5b demultiplexes the dummy light combined by the optical coupler 4b. The dummy light source controller 6b measures the light output level of the dummy light demultiplexed by the demultiplexer 5b, and the dummy light sources 3b1 and 3b2 so that the measured light output level becomes a predetermined value set in advance. A control signal for controlling the light output level of the light is output.

  The optical multiplexer 7 combines the dummy lights output from the dummy light output units 2-a and 2-b. The optical amplifiers 8-1 to 8-n amplify the signal lights output from the signal light transmitters 1-1 to 1-n, respectively. The optical amplifier 9 amplifies the wavelength multiplexed dummy light from the optical multiplexer 7. The optical multiplexer 10 combines the signal light amplified by the optical amplifiers 8-1 to 8-n and the wavelength multiplexed dummy light amplified by the optical amplifier 9. The demultiplexer 11 demultiplexes the wavelength multiplexed light from the optical multiplexer 10. The optical amplifier control unit 12 measures the optical output level of the wavelength-division multiplexed light demultiplexed by the demultiplexer 11, and the measured optical output level is the same as when operating at the maximum number of wavelengths. The optical amplifier 9 that amplifies the wavelength-multiplexed dummy light is controlled. The optical amplifier 13 amplifies the wavelength multiplexed light that has passed through the duplexer 11 and sends it to the optical transmission line 14.

Next, the operation will be described.
In FIG. 1, signal light transmission units 1-1 to 1-n output signal light having different center wavelengths λ1 to λn, respectively, and dummy light output units 2-a and 2-b are the centers of the signal lights. Dummy light having center wavelengths λa and λb different from the wavelengths λ1 to λn is output.
FIG. 2 is a characteristic diagram showing the wavelength spectrum of the signal light and the dummy light. The maximum number of wavelengths that can be multiplexed by this wavelength multiplexing transmission apparatus is m (m is an arbitrary natural number greater than or equal to n) and is used. When the wavelength number n of the signal light to be transmitted is less than the maximum wavelength number m, by inputting the dummy light to the empty wavelength, the power input to the optical amplifier 13 is lower than the design value, and the SN ratio of the optical amplifier output This prevents the phenomenon of deterioration.

  Therefore, in FIG. 2, the dummy light has only two wavelengths of the central wavelengths λa and λb, but the number of wavelengths of the dummy light is appropriately set according to the number of wavelengths n of the signal light to be operated. In FIG. 2, the wavelength of the dummy light is shorter and longer than the operating signal light, but may be applied to an empty wavelength between the operating signal lights. Further, in FIG. 2, the light output level of the dummy light is made higher than the light output level of the signal light, but this is because the wavelength intervals λ1-λa and λb-λn between the signal light adjacent to the dummy light are different from each other. This is because the wavelength interval between the signal lights is longer than, for example, λ2 to λ1, so that the entire wavelength spectrum is balanced. The optical output level of such dummy light is also appropriately set in advance according to the signal light to be operated. Is set.

In the dummy light output unit 2-a of FIG. 1, the dummy light sources 3a1 and 3a2 output dummy lights having different center wavelengths λa1 and λa2, respectively, and the optical coupler 4a outputs dummy light output from the dummy light sources 3a1 and 3a2. Are combined.
FIG. 3 is a characteristic diagram showing the wavelength characteristics of the dummy light. As shown in FIG. 3A, when dummy light having the same wavelength λa is output from the dummy light sources 3a1 and 3a2 and combined, the dummy light source It is conceivable that interference between wavelengths occurs in the combined dummy light due to a slight wavelength deviation caused by the characteristic difference between the individual products 3a1 and 3a2, and this may cause a decrease in performance such as beat.

In the first embodiment, as shown in FIG. 3 (b), center wavelengths λa1, which are symmetrically different from each other about the center wavelength λa set from the dummy light sources 3a1, 3a2 to the dummy light output unit 2-a. Dummy lights having λa2 and close enough to prevent interference between wavelengths are output.
Therefore, the wavelengths output from the dummy light sources 3a1 and 3a2 are slightly shifted from the center wavelengths λa1 and λa2 depending on the characteristics of the individual products of the dummy light sources 3a1 and 3a2, but the center wavelengths λa1 and λa2 may be slightly shifted. Since it is set in advance so that interference between wavelengths can be prevented, interference between wavelengths of the combined dummy light can be prevented, and a factor of performance degradation such as beat can be prevented.

  In FIG. 3B, the case where two dummy light sources 3a1 and 3a2 are used has been described. However, when three dummy light sources are used, the dummy light source 3a1 is used as shown in FIG. , 3a2 and 3a3 with the center wavelength λa set in the dummy light output unit 2-a as the center, the center wavelengths λa1, λa2 and λa3 are different from each other in a symmetrical manner, and interference between wavelengths can be prevented. It suffices to output dummy lights that are close to each other. Further, even when four or more dummy light sources are used, similarly, dummy lights that are close to each other with respect to the center wavelength λa so as to be able to prevent interference between the wavelengths are output. It ’s fine.

In the dummy light output unit 2-a of FIG. 1, the optical coupler 4a combines the dummy lights output from the dummy light sources 3a1 and 3a2.
Here, unlike the optical switch, the optical coupler 4a is a passive component that does not require mechanical and electrical control, and the probability of occurrence of a failure is small enough to be ignored. Therefore, a highly reliable redundant system can be configured for the dummy light source.

  The demultiplexer 5a demultiplexes the dummy light combined by the optical coupler 4a, and the dummy light source controller 6a measures the optical output level of the dummy light demultiplexed by the demultiplexer 5a. A control signal for controlling the light output level of the dummy light sources 3a1 and 3a2 is output so that the measured light output level becomes a predetermined value set in advance.

As an example, a description will be given of a response when a failure occurs in the dummy light source 3a1 and the light output is cut off.
The light output of the dummy light source 3a1 is cut off, and the light output level of the demultiplexed output from the demultiplexer 5a, which is the result of combining the dummy light output from the dummy light sources 3a1 and 3a2 by the optical coupler 4a, is reduced. When the dummy light source controller 6a measures, the dummy light source controller 6a controls the dummy light sources 3a1 and 3a2 to increase the light output level in order to keep the measured light output level at a predetermined value. In this example, the dummy light source 3a1 cannot increase the light output level because it is in a fault state, but the dummy light source 3a2 increases the light output level by increasing the light output level. The light output level measured by the dummy light source control unit 6a can be kept at a predetermined value.
Accordingly, even if one of the dummy light sources 3a1 and 3a2 breaks down, the dummy light combined by the optical coupler 4a is controlled by increasing the light output level of the other normal dummy light source. The optical output level can be set to a predetermined value, and the operation of the apparatus can be continued.
Although the operation in the dummy light output unit 2-a in FIG. 1 has been described above, the operation in the dummy light output unit 2-b is the same as the operation in the dummy light output unit 2-a. Therefore, the description is omitted.

  The optical multiplexer 7 in FIG. 1 combines the dummy lights output from the dummy light output units 2-a and 2-b, and the optical amplifiers 8-1 to 8-n include the signal light transmission units 1-1 to 1-1. The signal light output from 1-n is amplified, and the optical amplifier 9 amplifies the wavelength-multiplexed dummy light from the optical multiplexer 7. The optical multiplexer 10 combines the signal light amplified by the optical amplifiers 8-1 to 8-n and the wavelength multiplexed dummy light amplified by the optical amplifier 9. The demultiplexer 11 demultiplexes the wavelength multiplexed light from the optical multiplexer 11, and the optical amplifier controller 12 measures the optical output level of the wavelength multiplexed light demultiplexed by the demultiplexer 11, and the measurement The optical amplifier 9 that amplifies the wavelength-multiplexed dummy light is controlled so that the optical output level is the same as when operating at the maximum number of wavelengths. The optical amplifier 13 amplifies the wavelength multiplexed light that has passed through the duplexer 11 and sends it to the optical transmission line 14.

  In the first embodiment, the two dummy light output units 2-a and 2-b are provided. However, if the number of dummy light output units is one or more, how many are provided. Also good.

As described above, according to the first embodiment, the light output level of the dummy light combined by the optical coupler 4a is measured, and the dummy light source 3a1 is set so that the measured light output level becomes a predetermined value. , 3a2 is provided with a dummy light source control unit 6a for controlling the light output level of the other dummy light source 3a1 and 3a2 so as to increase the light output level of the other normal dummy light source. Thus, the optical output level of the dummy light combined by the optical coupler 4a can be set to a predetermined value, and the operation of the apparatus can be continued.
In addition, since the optical coupler 4a that combines the dummy lights output from the dummy light sources 3a1 and 3a2 is provided, the optical coupler 4a is a passive component that does not require mechanical and electrical control unlike the optical switch. The probability that a failure will occur is negligibly small. Therefore, a highly reliable redundant system can be configured for the dummy light source.
Further, with the center wavelength λa set in the dummy light output unit 2-a as the center, the center wavelengths λa1 and λa2 are symmetrically different from each other, and the dummy lights are close enough to prevent interference between the wavelengths. Since the dummy light sources 3a1 and 3a2 for output are provided, the dummy light having the center wavelength λa set in the dummy light output unit 2-a can be output by combining the dummy lights by the optical coupler 4a. In addition, interference between wavelengths of the combined dummy light can be prevented, and a factor of performance degradation such as beat can be prevented.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing a wavelength division multiplex transmission apparatus according to Embodiment 2 of the present invention. In the dummy light output unit 2-a shown in FIG. 4, the monitor circuit 21a1 outputs the dummy light output from the dummy light source 3a1. In addition to measuring the level, the performance state of the dummy light source 3a1 is measured, and a preliminary alarm is generated according to the degradation of the measured performance state. The monitor circuit 21a2 measures the light output level of the dummy light output from the dummy light source 3a2, measures the performance state of the dummy light source 3a2, and generates a preliminary alarm according to the degradation of the measured performance state It is.
When a preliminary alarm is generated from the monitor circuits 21a1 and 21a2, the dummy light source control unit 22a gradually decreases the light output level of the dummy light source subject to the preliminary alarm measured by the monitor circuit to finally become zero. When the light output level of the dummy light source is controlled so that the preliminary alarm from the monitor circuits 21a1 and 21a2 is released, the light output level of the dummy light source from which the preliminary alarm measured by the monitor circuit is released gradually increases. The light output level of the dummy light source is controlled so that the light output level with the other dummy light source is finally balanced.
The dummy light output unit 2-b is configured similarly to the dummy light output unit 2-a. Other configurations are the same as those in FIG.

Next, the operation will be described.
In FIG. 4, the monitor circuit 21a1 measures the light output level of the dummy light output from the dummy light source 3a1, and the monitor circuit 21a2 measures the light output level of the dummy light output from the dummy light source 3a2. Notify the light source controller 22a.
The monitor circuit 21a1 always measures the performance state of the dummy light source 3a1, and the light output level can be output normally, but a change in the internal state that is likely to cause a failure in the future, for example, the light source element When heat generation exceeding the design value, increase in supply current, etc. are measured, a preliminary alarm is notified to the dummy light source control unit 22a. The monitor circuit 21a2 is similarly monitored for the dummy light source 3a2.

  As in the first embodiment, the dummy light source control unit 22a measures the light output level of the dummy light demultiplexed by the demultiplexer 5a, and the measured light output level is a predetermined value set in advance. A control signal for controlling the light output level of the dummy light sources 3a1 and 3a2 is output so that

Here, a response when a preliminary alarm is notified from the monitor circuit 21a1 will be described.
When the preliminary alarm is notified from the monitor circuit 21a1, the dummy light source control unit 22a monitors the light output levels measured by the monitor circuits 21a1 and 21a2, and determines the light output level of the dummy light source 3a1 that is the target of the preliminary alarm. The light output level of the dummy light source 3a1 is controlled so as to gradually decrease and finally become zero. In this case, the dummy light source control unit 22a outputs the light output of the dummy light source 3a2 by the amount of decrease in the dummy light source 3a1 so that the light output level of the dummy light demultiplexed by the demultiplexer 5a becomes a predetermined value set in advance. Control to raise the level.
Accordingly, the dummy light source 3a1 can be replaced after the light output level of the dummy light source 3a1 is gradually lowered and finally reduced to zero in accordance with the deterioration of the performance state before causing the failure of the dummy light source 3a1. The equipment can be maintained without affecting the transmission.

Next, a response when the preliminary alarm is canceled from the monitor circuit 21a1 after replacement of the dummy light source 3a1 will be described.
The dummy light source controller 22a monitors the light output levels measured by the monitor circuits 21a1 and 21a2 when the preliminary alarm from the monitor circuit 21a1 is canceled, and the light of the dummy light source 21a1 whose preliminary alarm is canceled. The light output level of the dummy light source 3a1 is controlled so that the output level is gradually increased and finally the light output level with the dummy light source 3a2 is balanced. In this case, the dummy light source control unit 22a increases the light output level of the dummy light source 3a1 and the light output of the dummy light source 3a2 so that the light output level of the dummy light demultiplexed by the demultiplexer 5a becomes a predetermined value set in advance. Control to lower the level.
Accordingly, the dummy light source 3a1 becomes normal, the light output level of the dummy light source 3a1 is gradually increased by releasing the preliminary alarm, and finally the light output level with the dummy light source 3a2 can be balanced. It is possible to restore the state before the occurrence of the preliminary alarm without affecting the transmission.
Although the case where the preliminary alarm is notified and canceled from the monitor circuit 21a1 has been described above, the light output level of the dummy light source 3a2 is similarly set for the case where the preliminary alarm is notified and canceled from the monitor circuit 21a2. The dummy light source 3a2 is replaced after being gradually lowered and finally made zero, and the light output level of the dummy light source 3a2 is gradually raised so that the light output level with the dummy light source 3a1 is finally balanced. Can do.

As described above, according to the second embodiment, when a preliminary alarm is generated from the monitor circuit 21a1, the light output level of the dummy light source 3a1 that is the target of the preliminary alarm measured by the monitor circuit 21a1 gradually decreases. In addition, since the dummy light source control unit 22a that controls the light output level of the dummy light source 3a1 so as to finally become zero is provided, the dummy light source 3a1 according to the deterioration of the performance state before causing the failure of the dummy light source 3a1. Thus, the dummy light source 3a1 can be replaced after the optical output level is gradually reduced to zero and the apparatus can be maintained without affecting the signal transmission.
Further, when the preliminary alarm from the monitor circuit 21a1 is released, the light output level of the dummy light source 3a1 for which the preliminary alarm measured by the monitor circuit 21a1 is released gradually increases, and finally the other dummy light sources Since the dummy light source control unit 22a for controlling the light output level of the dummy light source 3a1 is provided so that the light output level with the 3a2 is balanced, the dummy light source 3a1 becomes normal, and the light output of the dummy light source 3a1 is released by releasing the preliminary alarm. The level can be gradually increased so that the light output level with the other dummy light sources 3a2 can be balanced eventually, and the state before the occurrence of the preliminary alarm is restored without affecting the signal transmission. Can do.

It is a block diagram which shows the wavelength division multiplexing transmission apparatus by Embodiment 1 of this invention. It is a characteristic view which shows the wavelength spectrum of signal light and dummy light. It is a characteristic view which shows the wavelength characteristic of dummy light. It is a block diagram which shows the wavelength division multiplexing transmission apparatus by Embodiment 2 of this invention.

Explanation of symbols

  1-1 to 1-n signal light transmission unit, 2-a, 2-b dummy light output unit, 3a1, 3a2, 3b1, 3b2 dummy light source, 4a, 4b optical coupler, 5a, 5b, 11 demultiplexer, 6a , 6b, 22a Dummy light source control unit, 7, 10 optical multiplexer, 8-1 to 8-n, 9, 13 optical amplifier, 12 optical amplifier control unit, 14 optical transmission line, 21a1, 21a2 monitor circuit.

Claims (4)

A plurality of signal light transmitters that output signal lights having different center wavelengths;
A dummy light output unit that outputs dummy light having a central wavelength different from the plurality of signal lights;
An optical multiplexer that combines the signal light output from the plurality of signal light transmission units and the dummy light output from the dummy light output unit;
An optical amplifier that amplifies the wavelength multiplexed light from the optical multiplexer and sends it to the optical transmission line;
The dummy light output unit is
A plurality of dummy light sources that output dummy light close to the center wavelength set in the dummy light output unit;
An optical coupler for combining dummy lights output from the plurality of dummy light sources;
A dummy light source control unit that measures the light output level of the dummy light combined by the optical coupler and controls the light output levels of the plurality of dummy light sources so that the measured light output level becomes a predetermined value; A wavelength division multiplexing transmission apparatus comprising: Multiple dummy light sources
The dummy light is output so that the center wavelengths are symmetrically different from each other around the center wavelength set in the dummy light output unit and are close enough to prevent interference between the wavelengths. 1 is a wavelength division multiplexing transmission apparatus. The dummy light output section
A dummy light source output from each dummy light source is measured, and the performance state of each dummy light source is measured, and a monitor circuit is provided that generates a preliminary alarm according to the degradation of the measured performance state,
The dummy light source controller
When a preliminary alarm is generated from the monitor circuit, the light output level of the dummy light source is measured so that the light output level of the dummy light source subject to the preliminary alarm gradually decreases and finally becomes zero. 3. The wavelength division multiplexing transmission apparatus according to claim 1, wherein the wavelength multiplexing transmission apparatus is controlled. The dummy light source controller
When the preliminary alarm from the monitor circuit is canceled, the light output level of the dummy light source for which the preliminary alarm measured by the monitor circuit is released gradually increases, and finally the light output level with other dummy light sources 4. The wavelength division multiplex transmission apparatus according to claim 3, wherein the optical output level of the dummy light source is controlled so that the two are balanced.

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