JP2011010015A - Wavelength division multiplex optical transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct gain deviation to be generated on a transmission line in a short time, to obtain an optical signal of a predetermined optical level, in wavelength extension.SOLUTION: The wavelength division multiplex optical transmitter is provided with: a wavelength level monitor 13 which detects the optical level of each wavelength of a received extended wavelength division multiplex signal; an optical amplifier 16 which amplifies the optical level of the extended wavelength division multiplex signal; a wavelength division multiplexer 17 which divides the extended wavelength division multiplex signal whose optical level is amplified by the optical amplifier into an optical signal of each wavelength; a variable attenuator 18 which attenuates the optical level of the optical signal of each wavelength to be divided by the wavelength division multiplexer; a light receiving element 19 which detects the optical level from the optical signal of each wavelength to be attenuated by the variable attenuator; and a monitoring controller 21 which controls an attenuation amount of the optical level of each wavelength by the variable attenuator based on the optical level to be detected by the wavelength level monitor, and controls an amplification amount of the optical level of the optical amplifier based on the optical level to be detected by the light receiving element.

Description

  The present invention relates to a wavelength division multiplexing optical transmission apparatus for increasing the system capacity by, for example, increasing the wavelength of an existing wavelength division multiplexing optical transmission system.

  Submarine optical cable transmission systems are roughly classified into a non-relay system that is applied to the strait crossing and a long-distance relay system that includes a submarine repeater that is applied to the ocean. A submarine optical cable transmission system that requires a long-distance repeater system consists of a submarine repeater transmission line and land-based wavelength division multiplexing optical transmitters at both ends, and a submarine repeater is installed for each repeat span of about 50 to 80 km. To do.

  As a technique for efficiently transmitting a plurality of information using such an optical cable, there is a wavelength division multiplexing optical transmission system. In this wavelength division multiplexing optical transmission system, it is rare that the system is operated with the maximum number of wavelengths from the initial design, and the number of wavelengths is generally increased according to the line demand. Also, since the submarine repeater is always operated at a constant power, the total power of the optical signal transmitted from the land-based wavelength division multiplexing optical transmission device is always output at a constant level, and the power for each wavelength of the optical signal is also operated. It is necessary to make it constant regardless of the number of wavelengths.

  Therefore, when the operating wavelength of this wavelength division multiplexing optical transmission system is less than the maximum number of wavelengths, in order to make the total power for optical transmission and the power for each wavelength of the optical signal constant, power adjustment called dummy optical signal is performed. It is common to send a pseudo signal together with an optical signal to a submarine repeater. In addition, it is possible to transmit (upgrade) an optical signal with a number of wavelengths that exceeds the number of wavelengths initially designed by improving the characteristics of transmitters and receivers used in recent years and strengthening error correction capability. However, in this upgrade, various extension methods have been implemented, such as removing existing wavelengths and adding new wavelengths, or increasing the system capacity by coexisting existing wavelengths and new wavelengths. The optimization adjustment is complicated.

  First, in the wavelength division multiplexing optical transmission apparatus, it is necessary to carry out optimization for preventing the expansion work from adversely affecting the existing wavelengths already in operation. In particular, when a new wavelength is added, it is necessary to adjust the optical level of the newly added wavelength on the transmission side, and to optimize the optical level so that a predetermined OSNR (Optical Signal-to-Noise Ratio) is obtained. is there. However, if the light level is increased too much, the signal characteristics of other wavelengths may be deteriorated, and if it is too low, there is a problem that its own signal characteristics cannot be satisfied.

  Further, after the adjustment of the light level on the transmission side, it is necessary to further adjust the light level on the reception side so that it is within the dynamic range of the optical receiver. Here, in the case of an optical receiver using an optical amplifier, the dynamic range can be set wide, and the optical level adjustment on the reception side is much easier than the optical level adjustment on the transmission side. On the other hand, there is a problem that the cost increases.

  On the other hand, without using an optical amplifier for each optical receiver, the optical signal wavelengths are collectively amplified by the optical amplifier so that an appropriate optical level is obtained before the wavelength division multiplexer in the previous stage. There is also a wavelength division multiplexing optical transmission apparatus that adjusts an optical level received by an optical receiver after division. However, depending on this adjustment, the optical level received by the optical receiver may be near the minimum allowable optical level.In particular, there is a margin for a decrease in optical level due to the effects of time fluctuations from the transmission path, repair of occurrence of optical cable faults, etc. There is a problem of decreasing. In addition, due to the problem of the bandwidth of the submarine repeater, there is a problem that the received light spectrum does not become flat and the gain may be inclined. For the above reasons, the operator needs to pay attention to both the existing wavelength and the additional wavelength, which causes a problem that makes optimization adjustment more complicated.

  Therefore, in order to solve the above-mentioned problems, wavelength division multiplexing optical transmission that makes it possible to reduce the light level of the existing wavelength to the lowest allowable light level and to increase the light level of the new wavelength accordingly. There is an apparatus (for example, refer to Patent Document 1).

JP 2005-269007 A

  However, the wavelength division multiplexing optical transmission device disclosed in Patent Document 1 does not consider the control method for the optical level of the newly installed optical signal and the problem of the gain tilt of the submarine repeater. When the dynamic range is narrow, there is a problem that the specified value may not be satisfied even if the light level is optimized.

  The present invention has been made in order to solve the above-described problems, and is capable of realizing wavelength extension in a shorter time by saving labor in adjustment work necessary for wavelength extension. The object is to provide a transmission device.

  The wavelength division multiplexing optical transmission apparatus according to the present invention is a wavelength division multiplexing optical transmission apparatus that adds an additional wavelength division multiplexing signal to an existing wavelength division multiplexing signal, and detects the optical level of each wavelength of the received additional wavelength division multiplexing signal. Wavelength level monitor, optical amplifier that amplifies the optical level of the received additional wavelength division multiplexed signal, and wavelength division multiplexing that demultiplexes the additional wavelength division multiplexed signal whose optical level is amplified by the optical amplifier into optical signals of each wavelength An attenuator, a variable attenuator for attenuating the optical level of each wavelength optical signal demultiplexed by the wavelength division multiplexer, and a light receiving element for detecting the optical level from the optical signal for each wavelength attenuated by the variable attenuator, Based on the light level detected by the wavelength level monitor, the attenuation of the light level of each wavelength by the variable attenuator is controlled, and the light of the optical amplifier is based on the light level detected by the light receiving element. In which and a monitoring controller for controlling the amount of amplification of the bell.

  According to this invention, since it comprised as mentioned above, the adjustment operation required in order to acquire a desired characteristic by wavelength extension can be performed in a short time. In addition, since the number of optical amplifiers provided in the optical receiver can be reduced, the cost can be reduced.

It is a figure which shows the structure of the wavelength division multiplexing optical transmission system which concerns on Embodiment 1 of this invention. It is a figure which shows the optical level of the optical signal received by the transmission-and-reception optical spectrum and optical receiver before and behind the wavelength extension in Embodiment 1 of this invention. It is a figure which shows the structure of the wavelength division multiplexing optical transmission system which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the optical receiver in Embodiment 2 of this invention. It is a figure which shows the structure of the wavelength division multiplexing optical transmission system which concerns on Embodiment 3 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a diagram showing a configuration of a wavelength division multiplexing optical transmission system according to Embodiment 1 of the present invention.
In the wavelength division multiplexing optical transmission system according to the embodiment of the present invention, when a new wavelength is inserted at a wavelength interval narrower than the existing wavelength while leaving the existing wavelength, a part of the existing wavelength is removed and the existing wavelength is removed. There are three cases where new wavelengths are inserted at a narrow wavelength interval and when all existing wavelengths are removed and all new wavelengths are used. A case will be described in which wavelength extension is performed by inserting a new wavelength while keeping the wavelength.

  As shown in FIG. 1, the wavelength division multiplexing optical transmission system includes a wavelength division multiplexing optical transmission device (transmission side) 1, a submarine repeater transmission line 2, and a wavelength division multiplexing optical transmission device (reception side) 3.

  The wavelength division multiplexing optical transmission device (transmission side) 1 transmits an existing wavelength division multiplexing signal of a wavelength and a wavelength division multiplexing signal of an additional wavelength to the wavelength division multiplexing optical transmission device (reception side) 3 and a submarine repeater transmission line 2. Is to be sent via. As shown in FIG. 1, the wavelength division multiplexing optical transmission apparatus (transmission side) 1 includes an existing WDM (Wavelength Division Multiplexing) apparatus 4, a supervisory control apparatus 5, optical transmitters 6-1 to 6-n, and wavelength division multiplexing. And an optical amplifier 8, a multiplexer / demultiplexer 9, and an optical amplifier 10.

  The existing WDM device 4 multiplexes existing optical signals of respective wavelengths to generate a wavelength division multiplexed signal. The existing wavelength division multiplexed signal generated by the existing WDM device 4 is transmitted to the multiplexer / demultiplexer 9.

  The supervisory control device 5 performs control and status monitoring of each device of the wavelength division multiplexing optical transmission device (transmission side) 1. The supervisory control device 5 causes the optical transmitters 6-1 to 6-n to generate optical signals having respective amplification wavelengths.

  The optical transmitters 6-1 to 6-n (n is a natural number) generate and transmit an optical signal of an additional wavelength based on the control by the monitoring control device 5, and are provided for each additional wavelength. It is. Note that the total power of the wavelength division multiplexed signal transmitted from the wavelength division multiplexing optical transmission apparatus (transmission side) 1 needs to be the same as the total power already in operation, but the optical transmitters 6-1 to 6-6. Since n is intended to increase the wavelength with respect to the existing wavelength, it is necessary to lower the optical level of the optical signal with the additional wavelength with respect to the optical level of the optical signal with the existing wavelength. Therefore, the optical transmitters 6-1 to 6-n are configured to have a transmission quality higher than that of the existing WDM device 4 and capable of transmitting even at a wavelength interval narrower than the existing wavelength. The optical signals of the additional wavelengths generated by the optical transmitters 6-1 to 6 -n are transmitted to the wavelength division multiplexer 7.

  The wavelength division multiplexer 7 combines the optical signals of the additional wavelengths transmitted from the optical transmitters 6-1 to 6-n. Further, the wavelength division multiplexer 7 may be configured to include a chromatic dispersion compensating fiber and an optical amplifier according to the conditions of the transmission path in order to align the optical peak level per combined wavelength to some extent. The additional wavelength division multiplexed signal combined by the wavelength division multiplexer 7 is transmitted to the optical amplifier 8.

  The optical amplifier 8 amplifies the optical level of the additional wavelength division multiplexed signal transmitted from the wavelength division multiplexer 7, and compensates for the loss of the optical level due to transmission. The additional wavelength division multiplexed signal whose optical level is amplified by the optical amplifier 8 is transmitted to the multiplexer / demultiplexer 9.

The multiplexer / demultiplexer 9 multiplexes the existing wavelength division multiplexed signal transmitted from the existing WDM device 4 and the amplified wavelength division multiplexed signal transmitted from the optical amplifier 8. The multiplexer / demultiplexer 9 includes an optical coupler or a WDM filter that multiplexes / demultiplexes only a predetermined optical band. The wavelength division multiplexed signal combined by the multiplexer / demultiplexer 9 is transmitted to the optical amplifier 10.
In FIG. 1, the multiplexer / demultiplexer 9 is arranged on the input side of the optical amplifier 10, but the optical level after the combination of the existing wavelength division multiplexed signal and the additional wavelength division multiplexed signal is a desired optical level. Therefore, the multiplexer / demultiplexer 9 may be arranged on the output side of the optical amplifier 10.

  The optical amplifier 10 amplifies the optical level of the wavelength division multiplexed signal transmitted from the multiplexer / demultiplexer 9 and compensates for the loss of the optical level due to transmission. The wavelength division multiplexed signal whose optical level is amplified by the optical amplifier 10 is transmitted to the submarine repeater transmission line 2.

  The submarine repeater transmission line 2 transmits a wavelength division multiplexed signal transmitted from the wavelength division multiplexing optical transmission apparatus (transmission side) 1 to the wavelength division multiplexing optical transmission apparatus (reception side) 3, and includes an optical fiber and its loss. It is comprised from the optical amplifier for compensating. In the submarine relay transmission line 2, a submarine relay device (not shown) is provided for each relay span of about 50 km to 80 km. The wavelength division multiplexed signal that has passed through the submarine repeater transmission line 2 is transmitted to the wavelength division multiplexing optical transmission apparatus (reception side) 3.

  The wavelength division multiplexing optical transmission device (reception side) 3 receives a wavelength division multiplexing signal transmitted from the wavelength division multiplexing optical transmission device (transmission side) 1 via the submarine repeater transmission line 2. As shown in FIG. 1, the wavelength division multiplexing optical transmission device (reception side) 3 includes an optical amplifier 11, an optical coupler 12, a wavelength level monitor (OSA) 13, a multiplexer / demultiplexer 14, an existing WDM device 15, an optical amplifier. 16, a wavelength division multiplexer 17, a variable attenuator 18, a light receiving element 19, optical receivers 20-1 to 20-n, and a monitoring control device 21.

  The optical amplifier 11 amplifies the optical level of the wavelength division multiplexed signal transmitted from the submarine repeater transmission line 2, and compensates for the loss of the optical level due to transmission. The wavelength division multiplexed signal whose optical level is amplified by the optical amplifier 11 is transmitted to the optical coupler 12.

  The optical coupler 12 optically branches the wavelength division multiplexed signal transmitted from the optical amplifier 11, and is an optical branching unit having a branching ratio that does not affect the transmission quality. The wavelength division multiplexed signal optically branched by the optical coupler 12 is transmitted to the wavelength level monitor 13 and the multiplexer / demultiplexer 9. In FIG. 1, the optical coupler 12 is disposed on the output side of the optical amplifier 11, but may be disposed on the input side of the optical amplifier 11.

The wavelength level monitor 13 (OSA) detects the optical level of each wavelength from the wavelength division multiplexed signal transmitted from the optical coupler 12 and calculates the level deviation between the wavelengths, and has sufficient resolution, for example. Consists of an optical spectrum analyzer. The level deviation between the wavelengths calculated by the wavelength level monitor 13 is transmitted to the monitoring control device 21.
Since the wavelength level monitor 13 is usually an expensive optical spectrum analyzer, it is rarely installed in the wavelength division multiplexing optical transmission device (reception side) 3 and can be installed when necessary. Since it is normal, the level deviation between the wavelengths calculated by the wavelength level monitor 13 may be manually input to the monitoring control device 21.

  The multiplexer / demultiplexer 14 separates the wavelength division multiplexed signal transmitted from the optical coupler 12 into an existing wavelength division multiplexed signal and an additional wavelength division multiplexed signal. The existing wavelength division multiplexed signal separated by the multiplexer / demultiplexer 14 is transmitted to the existing WDM device 15, and the additional wavelength division multiplexed signal is transmitted to the optical amplifier 16.

  The existing WDM device 15 receives an existing wavelength division multiplexed signal transmitted from the multiplexer / demultiplexer 14. The existing wavelength division multiplexed signal received by the existing WDM device 15 is demultiplexed into optical signals of respective wavelengths, attenuated to a desired optical level, and signal reproduction is performed.

  The optical amplifier 16 amplifies the additional wavelength division multiplexed signal transmitted from the multiplexer / demultiplexer 14 to a desired optical level based on the control by the monitoring control device 21. The additional wavelength division multiplexed signal whose optical level is amplified by the optical amplifier 16 is transmitted to the wavelength division multiplexer 17.

  The wavelength division multiplexer 17 demultiplexes the additional wavelength division multiplexed signal transmitted from the optical amplifier 16 into optical signals of the respective additional wavelengths. The wavelength division multiplexer 17 may be configured to include a chromatic dispersion compensating fiber and an optical amplifier according to the conditions of the transmission path. The optical signals of the additional wavelengths demultiplexed by the wavelength division multiplexer 17 are transmitted to the variable attenuator 18.

  The variable attenuator 18 attenuates the optical signal of each additional wavelength transmitted from the wavelength division multiplexer 17 to a desired optical level based on the control by the monitoring control device 21, and is provided for each additional wavelength. It is. The optical signals of the additional wavelengths whose light levels are attenuated by the variable attenuator 18 are transmitted to the light receiving element 19.

  The light receiving element 19 detects the optical level from the optical signal of each additional wavelength transmitted from the variable attenuator 18, and is provided for each additional wavelength. The optical level of each additional wavelength detected by the light receiving element 19 is transmitted to the monitoring control device 21, and the optical signal that has passed through the light receiving element 19 is transmitted to the optical receivers 20-1 to 20-n.

  The optical receivers 20-1 to 20-n (n is a natural number) receive optical signals of each additional wavelength transmitted from the light receiving element 19, and perform signal regeneration. The optical receivers 20-1 to 20-n have a reception quality higher than that of the existing WDM device 15 and are configured to have a performance capable of receiving even at a wavelength interval narrower than the existing wavelength.

  The monitoring control device 21 controls each device of the wavelength division multiplexing optical transmission device (reception side) 3, and a plurality of monitoring control devices 21 are provided. Further, in the supervisory control device 21, the optical level (target level) of the optical signal necessary for the optical receivers 20-1 to 20-n and the level deviation between each allowable wavelength are set in advance. The monitoring control device 21 uses the variable attenuator 18 for each wavelength based on the difference value calculated from the level deviation between the wavelengths transmitted from the wavelength level monitor 13 and the preset level deviation between the wavelengths. By controlling the attenuation of the light level, the level deviation between the wavelengths is absorbed. Further, based on a comparison between the light level of each additional wavelength transmitted from the light receiving element 19 and a preset desired light level, the amount of amplification of the light level by the optical amplifier 16 is controlled so as to obtain a desired light level. To do.

  1 shows transmission of a wavelength division multiplexed signal from the wavelength division multiplexing optical transmission apparatus (transmission side) 1 to the wavelength division multiplexing optical transmission apparatus (reception side) 3, but normally, an optical transmitter 6- 1-6-n and optical receivers 20-1 to 20-n are often transponders having functions of both transmitters and receivers, and wavelength division multiplexing optical transmission apparatuses (receiving side) 3 to wavelength division multiplexing optical transmission apparatuses ( It is also possible to transmit a wavelength division multiplexed signal toward the transmission side 1. These are omitted because the figure becomes complicated.

Next, the operation of the wavelength division multiplexing optical transmission system configured as described above will be described.
First, the existing WDM apparatus 4 of the wavelength division multiplexing optical transmission apparatus (transmission side) 1 generates an existing wavelength division multiplexing signal by multiplexing the existing optical signals of respective wavelengths. The existing wavelength division multiplexed signal generated by the existing WDM device 4 is transmitted to the multiplexer / demultiplexer 9.

  On the other hand, the optical transmitters 6-1 to 6-n generate an optical signal of an additional wavelength based on the control by the monitoring control device 5 and transmit it to the wavelength division multiplexer 7. Next, the wavelength division multiplexer 7 multiplexes the optical signals of the additional wavelengths transmitted from the optical transmitters 6-1 to 6-n. The additional wavelength division multiplexed signal multiplexed by the wavelength division multiplexer 7 is amplified by the optical amplifier 8 and transmitted to the multiplexer / demultiplexer 9.

  Next, the multiplexer / demultiplexer 9 multiplexes the existing wavelength division multiplexed signal transmitted from the existing WDM device 4 and the amplified wavelength division multiplexed signal transmitted from the optical amplifier 8. The wavelength division multiplexed signal combined by the multiplexer / demultiplexer 9 is amplified by the optical amplifier 10 and transmitted to the wavelength division multiplexed optical transmission apparatus (reception side) 3 through the submarine repeater transmission line 2.

  Next, the optical amplifier 11 of the wavelength division multiplexing optical transmission apparatus (reception side) 3 determines the optical level of the wavelength division multiplexing signal transmitted from the wavelength division multiplexing optical transmission apparatus (transmission side) 1 via the submarine repeater transmission line 2. Amplify. The wavelength division multiplexed signal whose optical level is amplified by the optical amplifier 11 is transmitted to the optical coupler 12. Next, the optical coupler 12 optically branches the wavelength division multiplexed signal transmitted from the optical amplifier 11. The wavelength division multiplexed signal optically branched by the optical coupler 12 is transmitted to the wavelength level monitor 13 and the multiplexer / demultiplexer 14.

  Next, the wavelength level monitor 13 detects the optical level of each wavelength from the wavelength division multiplexed signal transmitted from the optical coupler 12, and calculates the deviation level between the wavelengths. The deviation level between the wavelengths calculated by the wavelength level monitor 13 is transmitted to the monitoring control device 21.

  On the other hand, the multiplexer / demultiplexer 14 separates the wavelength division multiplexed signal transmitted from the optical coupler 12 into an existing wavelength division multiplexed signal and an additional wavelength division multiplexed signal. The existing wavelength division multiplexed signal separated by the multiplexer / demultiplexer 14 is transmitted to the existing WDM device 15, and the additional wavelength division multiplexed signal is transmitted to the optical amplifier 16.

  Next, the existing WDM device 15 demultiplexes the existing wavelength division multiplexed signal transmitted from the multiplexer / demultiplexer 14 into optical signals of each wavelength, attenuates them to a desired optical level, and performs signal reproduction.

  On the other hand, the optical amplifier 16 amplifies the additional wavelength division multiplexed signal transmitted from the multiplexer / demultiplexer 14 to a desired optical level based on the control by the monitoring control device 21. The additional wavelength division multiplexed signal whose optical level is amplified by the optical amplifier 16 is transmitted to the wavelength division multiplexer 17. Next, the wavelength division multiplexer 17 demultiplexes the additional wavelength division multiplexed signal transmitted from the optical amplifier 16 into optical signals of the respective additional wavelengths. The optical signals of the additional wavelengths demultiplexed by the wavelength division multiplexer 17 are transmitted to the variable attenuator 18.

  Next, the variable attenuator 18 attenuates the optical signal of each additional wavelength transmitted from the wavelength division multiplexer 17 to a desired optical level based on the control by the monitoring control device 21. The optical signals of the additional wavelengths whose light levels are attenuated by the variable attenuator 18 are transmitted to the light receiving element 19. Next, the light receiving element 19 detects the optical level of the optical signal of each additional wavelength transmitted from the variable attenuator 18. The optical level of the optical signal of each wavelength detected by the light receiving element 19 is transmitted to the monitoring control device 21, and the optical signal of each additional wavelength passing through the light receiving element is transmitted to the optical receivers 20-1 to 20-n. Is done.

  Next, the optical receivers 20-1 to 20-n receive the optical signals of the additional wavelengths transmitted from the light receiving element 19, and perform signal regeneration.

Next, control of the optical amplifier 16 and the variable attenuator 18 by the monitoring control device 21 of the wavelength division multiplexing optical transmission device (reception side) 3 will be described.
FIG. 2 is a diagram showing the transmission / reception optical spectrum before and after the wavelength extension and the optical level of the optical signal received by the optical receivers 20-1 to 20-n in the first embodiment of the present invention. FIG. 2A is a diagram showing the transmission / reception light spectrum and light level before the wavelength extension, and FIG. 2B is a diagram showing the transmission / reception light spectrum and light level after the wavelength addition.

  As shown in FIG. 2, when upgrading by adding wavelengths, the number of wavelengths exceeds the initially designed number of wavelengths, so the optical level of the added wavelength is the same as the optical level of the existing wavelength assumed in the initial setting. Therefore, it is necessary to make the light level of the additional wavelength lower than the light level of the existing wavelength. Specifically, when the band for the existing wavelength of 2 wavelengths is newly upgraded with the additional wavelength of 4 wavelengths, it is required to set the optical level of the additional wavelength to half of the existing wavelength.

  In addition, when transmitting a wavelength division multiplexed signal with an increased wavelength, a gain tilt is generated in the received light spectrum by the submarine repeater disposed in the submarine repeater transmission line 2. Therefore, as shown in FIG. 2B, a level deviation occurs in the optical levels of the optical signals of the additional wavelengths received by the optical receivers 20-1 to 20-n.

  In view of this, in the monitoring control device 21, the optical level required by the optical receivers 20-1 to 20-n and the allowable level deviation between the respective wavelengths are set in advance, and are first transmitted by the wavelength level monitor 13. The difference value between the level deviation between each wavelength and the preset level deviation of each wavelength is calculated, and the attenuation amount of the optical level of each wavelength by the variable attenuator 18 is set based on this difference value, and a gain inclination occurs. Control is performed so that the level deviation due to the operation is absorbed. Here, the variable attenuator 18 is a means for only attenuating the optical level, but the variable attenuator 18 may be replaced with an optical amplifier capable of adjusting the gain.

  In addition, the monitoring control device 21 compares the light level of each wavelength transmitted from the light receiving element 19 with a predetermined desired light level, and is received by the optical receivers 20-1 to 20-n. When it is determined that the optical level of the optical signal of each wavelength is insufficient, control is performed so that the amount of amplification of the optical level by the optical amplifier 16 is increased and a desired optical level is obtained.

  With this configuration, adjustment work necessary for obtaining desired characteristics by increasing the wavelength can be performed in a short time, and the dynamic range of the optical receivers 20-1 to 20-n is reduced. However, since it is possible to compensate for the decrease in the dynamic range, it is not necessary to provide an optical amplifier in each of the optical receivers 20-1 to 20-n, and the cost can be reduced.

  As described above, according to the first embodiment of the present invention, the monitoring control device 21 determines the level deviation between the wavelengths of the wavelength division multiplexed signal calculated by the wavelength level monitor 13 and the desired level deviation set in advance. And the variable attenuator 18 is controlled to absorb the level deviation based on the difference value, and the light level detected by the light receiving element 19 at the subsequent stage becomes a desired light level in advance. Since the optical amplifier 16 is controlled so as to achieve a desired light level, adjustment work necessary for obtaining desired characteristics by increasing the wavelength can be performed in a short time. Further, it is not necessary to provide an optical amplifier in each of the optical receivers 20-1 to 20-n, and the cost can be reduced.

Embodiment 2. FIG.
3 is a diagram showing a configuration of a wavelength division multiplexing optical transmission system according to Embodiment 2 of the present invention. FIG. 4 is a diagram showing the configuration of the optical receivers 22-1 to 22-n according to the second embodiment of the present invention.
In the wavelength division multiplexing optical transmission system according to the second embodiment of the present invention shown in FIG. 3, in addition to the functions of the optical receivers 20-1 to 20-n in the first embodiment of the present invention shown in FIG. And optical receivers 22-1 to 22-n having an error correction code function (FEC).
In the following, the same or similar components as those in the wavelength division multiplexing optical transmission system according to Embodiment 1 of the present invention shown in FIG.

  The optical receivers 22-1 to 22-n are optical receivers having an error correction code function in addition to the functions of the optical receivers 20-1 to 20-n according to the first embodiment of the present invention. The code error (Bit Error) occurring inside is corrected, and the number of code errors is notified to the monitoring control device 21. As shown in FIG. 4, the optical receivers 22-1 to 22-n include an O / E (Optical / Electrical) unit 23 that converts an optical signal of each additional wavelength transmitted from the light receiving element 19 into an electric signal. The FEC unit 24 that corrects the code error from the electrical signal converted by the O / E unit 23, and the E / O (Electrical / Optical) unit that converts the electrical signal whose code error is corrected by the FEC unit 24 into an optical signal 25.

  In addition to the functions of the supervisory control device 21 according to the first embodiment of the present invention, the supervisory control device 21 uses a code error rate (Bit) from the number of code errors notified from the optical receivers 22-1 to 22-n. (Error Rate; BER) is calculated, and based on a comparison between the calculated BER and a preset desired BER, an optical signal having an additional wavelength that does not reach the desired BER is preset by the monitoring control device 21. It has a function of improving the BER by controlling the variable attenuator 18 so as to reduce the attenuation amount within a range of a desired light level and an allowable level deviation between wavelengths. The BER of the optical signal of each wavelength after transmission is preferably adjusted so as to be averaged for each wavelength in accordance with the performance of the optical receivers 22-1 to 22-n used.

  Thus, the supervisory control device 21 calculates the BER for each wavelength from the number of code errors notified from the optical receivers 22-1 to 22-n, and compares the calculated BER with a preset BER. By controlling the variable attenuator 18 within a range of a desired light level preset by the monitoring controller 21 and an allowable level deviation between the wavelengths so that a desired BER is obtained, After the BER of the optical signal is averaged, the optical signal of each wavelength received by the optical receivers 22-1 to 22-n can be set to a desired optical level, and desired characteristics are obtained by increasing the wavelength. Therefore, it is possible not only to perform the adjustment work necessary for this, but also to obtain high characteristics for each wavelength.

  As described above, according to the second embodiment of the present invention, the supervisory control device 21 calculates the BER for each wavelength from the number of code errors notified from the optical receivers 22-1 to 22-n, and the calculation. In addition to the effect of the first embodiment of the present invention, the variable attenuator 18 is controlled within a permissible range so that the desired BER is compared with the BER set in advance. Thus, it is possible to obtain high characteristics for each wavelength.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing the configuration of a wavelength division multiplexing optical transmission system according to Embodiment 3 of the present invention.
In the following, the same or similar components as those in the wavelength division multiplexing optical transmission system according to the second embodiment of the present invention shown in FIG.

  In addition to the functions of the supervisory control device 21 according to the first embodiment of the present invention, the supervisory control device 21 calculates the code error rate (BER) from the number of code errors notified from the optical receivers 22-1 to 22-n. The BER of the optical signal of each wavelength is calculated and transmitted to the monitoring control device 5 on the receiving side.

  In addition to the functions of the supervisory control device 5 according to the first embodiment of the present invention, the supervisory control device 5 uses the optical signal of each wavelength based on the BER of the optical signal of each wavelength transmitted from the supervisory control device 21. The optical level of the optical signal of each wavelength generated by the optical transmitters 6-1 to 6-n is adjusted by adjusting the pre-emphasis amount for providing a deviation in the optical level of each wavelength so as to average the BER of To control.

  Thus, the optical transmission is performed so that the BER of the optical signal of each wavelength calculated by the monitoring control device 21 on the reception side is fed back to the monitoring control device 5 on the transmission side and the BER of the optical signal for each wavelength is averaged. After controlling the optical level of the optical signal of each wavelength generated by the devices 6-1 to 6-n, the variable attenuator 18 and the light receiving element 19 are controlled by the monitoring control device 21 on the receiving side, so that each wavelength After the BERs of the optical signals are averaged, the optical signals of the respective wavelengths received by the optical receivers 22-1 to 22-n can be set to desired optical levels, and desired characteristics can be obtained by increasing the wavelengths. Not only can the adjustment work necessary for obtaining be performed in a short time, but also the BER can be averaged in a short time, and higher average characteristics can be obtained for each wavelength.

  As described above, according to the third embodiment of the present invention, the BER of each wavelength optical signal calculated by the reception-side monitoring control device 21 is fed back to the transmission-side monitoring control device 5 so that each wavelength is fed back. After the optical levels of the optical signals of the respective wavelengths generated by the optical transmitters 6-1 to 6-n are controlled so as to average the BERs of the optical signals, the variable attenuator 18 is monitored by the monitoring control device 21 on the receiving side. In addition to the effect of the first embodiment of the present invention, the BER is averaged in a short time, and it is possible to obtain a higher average characteristic for each wavelength. It is.

  DESCRIPTION OF SYMBOLS 1 Wavelength division multiplexing optical transmission apparatus (transmission side), 2 Submarine repeater transmission line, 3 Wavelength division multiplexing optical transmission apparatus (reception side), 4,15 Existing WDM apparatus, 5,21 Monitoring and control apparatus, 6-1 to 6-6 n optical transmitter, 7, 17 wavelength division multiplexer, 8, 10, 11, 16 optical amplifier, 9, 14 multiplexer / demultiplexer, 12 optical coupler, 13 wavelength level monitor (OSA), 18 variable attenuator, 19 light reception Elements, 20-1 to 20-n, 22-1 to 22-n optical receiver, 23 O / E section, 24 error correction code (FEC) section, 25 E / O section.

Claims (3)

In a wavelength division multiplexing optical transmission apparatus that adds an additional wavelength division multiplexing signal to an existing wavelength division multiplexing signal,
A wavelength level monitor that detects the optical level of each wavelength of the received additional wavelength division multiplexed signal;
An optical amplifier for amplifying the optical level of the received additional wavelength division multiplexed signal;
A wavelength division multiplexer that demultiplexes an additional wavelength division multiplexed signal whose optical level is amplified by the optical amplifier into an optical signal of each wavelength;
A variable attenuator for attenuating the optical level of each wavelength optical signal demultiplexed by the wavelength division multiplexer;
A light receiving element that detects the light level from an optical signal of each wavelength attenuated by the variable attenuator;
Based on the light level detected by the wavelength level monitor, the attenuation amount of the light level of each wavelength by the variable attenuator is controlled, and the light level of the optical amplifier is amplified based on the light level detected by the light receiving element. A wavelength division multiplexing optical transmission device comprising a monitoring control device for controlling the amount. An optical receiver that receives an optical signal of each wavelength passing through the light receiving element and corrects a code error that occurs in the optical signal of each wavelength,
The supervisory control device calculates a code error rate of an optical signal for each wavelength from the number of code errors corrected by the optical receiver, and controls the variable attenuator and the optical amplifier based on the code error rate. The wavelength division multiplexing optical transmission apparatus according to claim 1. An optical receiver that receives an optical signal of each wavelength passing through the light receiving element and corrects a code error that occurs in the optical signal of each wavelength,
The supervisory control device calculates a code error rate of an optical signal for each wavelength from the number of code errors corrected by the optical receiver, and transmits the wavelength to the wavelength division multiplexing optical transmission device on the transmission side based on the code error rate. 2. The wavelength division multiplexing optical transmission apparatus according to claim 1, wherein the optical level of each optical signal is controlled.

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