JP2012109653A - Wavelength multiplex transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep output of an optical amplification section of a transmission unit constant even when a failure occurs on a transmission line.SOLUTION: A wavelength multiplex transmission device comprises: a monitoring section 24 for monitoring a light level relating to received wavelength-multiplexed light; a dummy light source 26 for emitting/extinguishing dummy light; a dummy light control section 25 which, when it is determined on the basis of the light level monitored by the monitoring section 24 that the wavelength-multiplexed light is in an input interruption state, makes the dummy light source 26 emit the dummy light; and a multiplexing section 29 for multiplexing modulated wavelength light and the dummy light emitted from the dummy light source 26. A transmission unit 2 transmits the wavelength-multiplexed light generated by the multiplexing section 29.

Description

  The present invention relates to a wavelength division multiplexing transmission apparatus having a wavelength pass-through function, which stabilizes output light even when input of wavelength division multiplexed light is cut off.

  Submarine optical cable transmission systems are roughly classified into a non-relay system that is applied to the crossing of the strait and a long-distance relay system that includes a submarine relay device intended for crossing the ocean. A submarine optical cable relay transmission system that requires a long-distance relay system is generally composed of a submarine repeater transmission line and land coastal station devices at both ends of the submarine repeater. Is.

  As a technique for efficiently transmitting a plurality of information using such an optical cable, there is a wavelength division multiplexing optical transmission technique. In the wavelength division multiplexing optical transmission technology, a plurality of signals are assigned (divided) to optical signals having different wavelengths, and these signals are multiplexed and transmitted bidirectionally through two optical fibers. On the transmitting side, optical signals from light sources having different wavelengths are combined by an optical multiplexer, and on the receiving side, optical signals of each wavelength are demultiplexed by an optical demultiplexer, and these are converted into electrical signals by a light receiving element. .

In such a submarine optical cable relay transmission system, each wavelength division multiplexing transmission device (landing station) is connected by a pair (two) of optical fiber pairs (FP). Here, a station that unloads all transmission data is referred to as a trunk station, and a station that unloads part of the transmission data is referred to as a branch station.
In recent years, at the time of system construction, a pair of FPs is allocated between the trunk station and the branch station, and a pair or more of FPs are allocated between the trunk station and the trunk station, and signals are transmitted and received between the stations. Here, in the submarine optical cable relay transmission system, it is rare that the submarine optical cable relay transmission system is normally operated with the maximum wavelength multiplexing number from the start of system operation. That is, at the start of system operation, only the number of wavelengths (number of lines) required at the initial stage is operated, and when the line demand comes later, the number of wavelength multiplexing is newly increased.

  However, the FPs added after the system operation is started are not uniform, and the FPs that require communication capacity are often between the trunk station and the trunk station. Therefore, even if the number of wavelengths is limited between the trunk station and the trunk station, there is often a case where there is still a capacity between the trunk station and the branch station. However, it is difficult to newly install a submarine optical cable to increase the capacity between the trunk station and the trunk station because a large amount of cost is required. Therefore, in recent years, in a wavelength division multiplexing transmission apparatus, the capacity between the trunk station and the trunk station is increased by transmitting the wavelength that is not in operation to the trunk station as it is without branching (termination) at the branch station. Attention has been focused on a wavelength division multiplexing transmission apparatus having a wavelength pass-through function.

  The operation of the wavelength division multiplexing transmission apparatus having this wavelength pass-through function will be described in detail. On the receiving side, first, the optical amplifying unit optically amplifies the wavelength multiplexed light input from the transmission path and goes to the 1: 2 branching unit. Output. This optical amplifying unit functions to compensate for loss generated in the transmission path. Next, the 1: 2 branching unit demultiplexes the wavelength multiplexed light into two, outputs one wavelength multiplexed light to the wavelength demultiplexing unit, and outputs the other wavelength multiplexed light to the transmitting unit (wavelength pass-through). This wavelength-passed wavelength multiplexed light is wavelength multiplexed light including a wavelength band that is not branched / inserted by the authorities. Next, the wavelength separation unit separates the wavelength multiplexed light into wavelength light for each wavelength and outputs the light to the wavelength conversion unit. Next, the wavelength conversion unit demodulates each wavelength light into the original signal, and outputs it to the signal reception unit as reception data.

  On the transmission side, first, the wavelength conversion unit modulates transmission data input from the signal transmission unit into each wavelength light for each signal, and outputs it to the wavelength multiplexing unit. Next, the wavelength multiplexing unit wavelength-multiplexes each wavelength light and outputs it to the 2: 1 multiplexing unit. On the other hand, the wavelength filter blocks wavelength-multiplexed light having a wavelength that is branched by the authorities out of the wavelength-multiplexed light that has been wavelength-passed through from the receiving unit, and passes only wavelength-multiplexed light that has a wavelength that is not branched by the authorities. Output to 1 multiplexing unit. Next, the 2: 1 multiplexing unit multiplexes the wavelength multiplexed light from the wavelength multiplexing unit and the wavelength multiplexed light from the wavelength filter, and outputs them to the optical amplification unit. Next, the optical amplifying unit amplifies the wavelength division multiplexed light and sends it to the wavelength division multiplexing transmission apparatus of the next station via the transmission line.

Here, in the submarine optical cable relay transmission system, the optical level per wave is roughly determined by the amount obtained by dividing the saturation output of the optical amplifier provided at the appropriate place in the transmission path by the number of wavelengths. However, when the number of wavelengths is small, the light level per wave becomes excessive, which causes a nonlinear optical effect in the transmission path and significantly deteriorates the transmission quality. As the nonlinear optical effect that causes this transmission quality deterioration, four-wave mixing (FWM), self-phase modulation (SPM), and the like are well known.
Therefore, wavelength multiplexed light propagating through the transmission line includes wavelength light (dummy light) with a high peak level in addition to modulated light (transmitted / received wavelength light, pass-through wavelength light). This dummy light exhibits the effect of lowering the peak level of the modulated light, and can suppress the nonlinear optical effect.

  In order to suppress the nonlinear optical effect in the transmission line, the peak level of the modulated light per wavelength is made constant and the total level is kept constant for the output of the optical amplifier on the transmission side. There is a need. However, in a wavelength division multiplexing transmission apparatus having a wavelength pass-through function, when a failure such as a cable break in a subsea section occurs in the transmission path, there is no input signal to the wavelength filter. As a result, since the number of wavelengths is reduced, when the optical amplifying unit is performing constant gain control, the output is lower than when normal, and when performing constant output control, 1 The peak level per wavelength increases.

  On the other hand, what is configured to keep the output of the optical amplification unit constant by controlling the amplification factor of the optical amplification unit based on the number of wavelengths input to the optical amplification unit and the output of the optical amplification unit at that time. Yes (for example, see Patent Documents 1-3).

Japanese Patent No. 4005646 Japanese Patent No. 3379052 Japanese Patent No. 4084144

However, the method disclosed in Patent Documents 1-3 performs gain control according to the number of wavelengths of the optical amplifier. Therefore, if the gain of the optical amplifier is controlled to increase when a plurality of wavelengths that are passed through the wavelength are cut off at the same time, the peak level per wavelength increases, and the same gain remains. Even when control is performed so as to maintain the peak level per wavelength, there is a problem in that the total level transmitted to the transmission path is reduced.
The wavelength multiplexed light output from the optical amplifier is repeatedly amplified as necessary by the optical amplifier in the submarine repeater installed at the appropriate position in the optical transmission line. However, the optical amplifier has the maximum number of input wavelengths. The gain profile is designed to be optimal at the time. For this reason, when operating at a wavelength number different from the design wavelength number, the gain profile differs from the design-time gain profile. There is a problem that it cannot be kept.

  The present invention has been made to solve the above-described problems. Even when a failure occurs in the transmission line, the wavelength at which the output of the optical amplification unit of the transmission unit can be kept constant and the transmission quality can be maintained. An object of the present invention is to provide a multiplex transmission apparatus.

  The wavelength division multiplexing transmission apparatus according to the present invention includes a dummy light source that emits and extinguishes dummy light, a monitor unit that monitors an optical level related to the received wavelength division multiplexed light, and wavelength multiplexing based on the light level monitored by the monitor unit. A dummy light control unit that causes the dummy light source to emit dummy light and a multiplexing unit that combines the modulated wavelength light and the dummy light emitted from the dummy light source when the light is determined to be in an input-off state; Provided, and the transmission unit transmits the wavelength multiplexed light generated by the multiplexing unit.

  In addition, the wavelength division multiplexing transmission apparatus according to the present invention includes a dummy light source that emits dummy light, a monitor unit that monitors a light level related to the received wavelength multiplexed light, wavelength light passed through from the reception unit, and the dummy light source. A wavelength selective switch that inputs dummy light and selects output light, and when it is determined that the wavelength multiplexed light is in an input cutoff state based on the light level monitored by the monitor unit, the dummy light is input to the wavelength selective switch. A dummy light control unit that is selected as output light, and a multiplexing unit that combines the modulated wavelength light and the output light from the wavelength selection switch, and the transmission unit transmits the wavelength multiplexed light generated by the multiplexing unit Is.

  According to the present invention, since it is configured as described above, even when a failure occurs in the transmission path, the output of the optical amplification unit of the transmission unit can be kept constant and the transmission quality can be maintained.

It is a figure which shows the structure of the submarine optical cable relay transmission system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the wavelength division multiplexing transmission apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the dummy light source in Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the receiving part in Embodiment 1 of this invention. It is a figure which shows the spectrum of the wavelength division multiplexed light (transmission / reception wavelength light and pass-through wavelength light) input from the transmission line in Embodiment 1 of this invention. It is a flowchart which shows the wavelength division multiplexing optical transmission operation | movement of the transmission part in Embodiment 1 of this invention. It is a figure which shows the spectrum of the wavelength multiplexed light (transmission / reception wavelength light) output from the wavelength multiplexing part in Embodiment 1 of this invention. It is a figure which shows the characteristic of the wavelength filter in Embodiment 1 of this invention. It is a figure which shows the spectrum of the wavelength division multiplexed light (pass-through wavelength light) output from the wavelength filter in Embodiment 1 of this invention. It is a flowchart which shows the input state confirmation operation | movement of the wavelength division multiplexed light of the transmission part in Embodiment 1 of this invention. It is a figure which shows the spectrum of the dummy light output from the wavelength filter in Embodiment 1 of this invention. It is a figure which shows the spectrum of the wavelength division multiplexed light (transmission / reception wavelength light and dummy light) output from the 2: 1 multiplexing part in Embodiment 1 of this invention. It is a figure which shows the structure of the wavelength division multiplexing transmission apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the operation | movement outline | summary of the wavelength selective switch in Embodiment 2 of this invention. It is a flowchart which shows the input state confirmation operation | movement of the wavelength division multiplexed light of the transmission part in Embodiment 2 of this invention. It is a figure which shows the structure of the dummy light source in Embodiment 3 of this invention. It is a figure which shows the spectrum of CW light and spectrum slice light in Embodiment 3 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the following description, it is assumed that the wavelength light that has been wavelength pass-through by the wavelength division multiplexing transmission apparatus and the wavelength light that is modulated from the input transmission data are wavelength multiplexed light in which a plurality of different wavelengths of light are multiplexed.
Embodiment 1 FIG.
First, a submarine optical cable relay transmission system including a wavelength division multiplexing transmission device having a wavelength pass-through function will be described.
1 is a diagram showing a configuration of a submarine optical cable relay transmission system according to Embodiment 1 of the present invention. FIG. 1 shows a case where four wavelength multiplexing transmission devices (landing stations A to D) are provided, and the stations are connected to each other via a pair (two) of optical fiber pairs (FP).
Here, it is referred to as a trunk station where all transmission data is landed, such as A station and D station, and a branch station where a part of the transmission data is landed, such as B station and C station.

In the submarine optical cable repeater transmission system configured as described above, each wavelength division multiplexing transmission apparatus transmits wavelength division multiplexed light between wavelength division multiplexing transmission apparatuses (for example, station A and station B) connected by FP.
For example, when wavelength multiplexed light is transmitted from station A to station C via station B, the wavelength multiplexed light from station A is wavelength-passed through station B and transmitted to station C. In this way, among the wavelength multiplexed light input to a certain station, wavelength multiplexed light having a wavelength that does not branch at that station can be transmitted to the next station by wavelength pass-through.

Next, the configuration of the wavelength division multiplexing transmission apparatus having the wavelength pass-through function as described above will be described.
FIG. 2 is a diagram showing the configuration of the wavelength division multiplexing transmission apparatus according to Embodiment 1 of the present invention. FIG. 2 shows a wavelength multiplexing transmission apparatus (B station) that transmits wavelength multiplexed light from the transmission path A-1 to the transmission path B-1.
As shown in FIG. 2, the wavelength multiplexing transmission apparatus includes a receiving unit 1 and a transmitting unit 2.

  The receiving unit 1 separates the wavelength multiplexed light input from the transmission path A-1 for each wavelength and demodulates the original signal. The receiving unit 1 includes an optical amplifying unit 11, a 1: 2 demultiplexing unit 12, a wavelength separating unit 13, and a wavelength converting unit 14.

  The optical amplifying unit 11 amplifies the wavelength multiplexed light input from the transmission line A-1, and fulfills the function of compensating for the transmission line loss. The wavelength multiplexed light amplified by the optical amplifying unit 11 is output to the 1: 2 demultiplexing unit 12.

  The 1: 2 demultiplexing unit 12 demultiplexes the wavelength multiplexed light amplified by the optical amplification unit 11 into two. One wavelength multiplexed light demultiplexed by the 1: 2 demultiplexing unit 12 is output to the wavelength demultiplexing unit 13, and the other wavelength multiplexed light is output to the transmission unit 2 (wavelength pass-through). This wavelength-passed wavelength multiplexed light is wavelength multiplexed light including a wavelength band that is not branched / inserted by the authorities.

  The wavelength separation unit 13 separates the wavelength multiplexed light input via the 1: 2 demultiplexing unit 12 into wavelength light for each wavelength. Each wavelength light separated by the wavelength separation unit 13 is output to the wavelength conversion unit 14.

  The wavelength conversion unit 14 demodulates each wavelength light separated by the wavelength separation unit 13 into an original signal. Each signal demodulated by the wavelength converter 14 is output as received data to a signal receiver (not shown).

  The transmission unit 2 modulates a plurality of signals into different wavelength lights, wavelength multiplexes them, and sends them to the transmission line B-1. The transmitter 2 includes a wavelength converter 21, a wavelength multiplexer 22, a 1: 2 demultiplexer 23, a monitor 24, a dummy light controller 25, a dummy light source 26, a 2: 1 multiplexer 27, a wavelength filter 28, A 2: 1 multiplexer 29 and an optical amplifier 30 are included.

  The wavelength conversion unit 21 modulates transmission data input from a signal transmission unit (not shown) into wavelength light for each signal. Each wavelength light modulated by the wavelength converting unit 21 is output to the wavelength multiplexing unit 22.

  The wavelength multiplexing unit 22 wavelength-multiplexes a plurality of wavelength lights modulated by the wavelength conversion unit 21. The wavelength multiplexed light multiplexed by the wavelength multiplexing unit 22 is output to the 2: 1 multiplexing unit 29.

  The 1: 2 demultiplexing unit 23 demultiplexes the wavelength multiplexed light that has been wavelength-passed through by the receiving unit 1 into two. One wavelength multiplexed light demultiplexed by the 1: 2 demultiplexing unit 23 is output to the 2: 1 multiplexing unit 27, and the other wavelength multiplexed light is output to the monitor unit 24.

  The monitor unit 24 monitors the optical level of the wavelength multiplexed light input via the 1: 2 demultiplexing unit 23 and confirms the input state of the wavelength multiplexed light. Here, the monitor unit 24 determines that the wavelength division multiplexed light is normally input when the monitored light level matches the preset expected value. On the other hand, when the monitored light level is lower than the expected value, the monitor unit 24 determines that the wavelength division multiplexed light is not normally input (the input is cut off). The result of the wavelength multiplexed light input state by the monitor unit 24 is notified to the dummy light control unit 25.

  The dummy light control unit 25 is a dummy light source so as not to emit dummy light when the result indicates normal (wavelength multiplexed light is normally input) based on the input state result notification from the monitor unit 24. 26 is controlled. On the other hand, when the result indicates an abnormality (wavelength multiplexed light is in an input-off state), the dummy light source 26 is controlled to emit dummy light.

The dummy light source 26 emits / extinguishes dummy light according to control by the dummy light control unit 25. As shown in FIG. 3, the dummy light source 26 includes a plurality of CW light sources 261-1 to 261-N capable of emitting CW (Continuous Wave) light in a band that is wavelength-passed through (not branched) by the authorities, and a plurality of CW light sources. An N: 1 multiplexing unit 262 that collects output light of the light sources 261-1 to 261-N is configured. This CW light is unmodulated light.
The dummy light source 26 can have various configurations other than the configuration shown in FIG. Further, the light level of the dummy light of the dummy light source 26 is set in advance to a value equivalent to the light level of the wavelength multiplexed light that is wavelength-passed by the receiving unit 1 so as to be equivalent to the case where the output of the wavelength filter 28 is normal. Is done. The dummy light emitted from the dummy light source 26 is output to the 2: 1 multiplexing unit 27.

  The 2: 1 multiplexer 27 multiplexes the wavelength multiplexed light input from the receiver 1 through the 1: 2 demultiplexer 23 and the dummy light emitted from the dummy light source 26. is there. The wavelength multiplexed light combined by the 2: 1 multiplexer 27 is output to the wavelength filter 28.

  The wavelength filter 28 blocks the wavelength multiplexed light having a wavelength that is branched by the authorities out of the wavelength multiplexed light input through the 2: 1 multiplexer 27, and passes only the wavelength multiplexed light having a wavelength that is not branched by the authorities. Is. The wavelength multiplexed light passed through by the wavelength filter 28 is output to the 2: 1 multiplexer 29.

The 2: 1 multiplexing unit 29 multiplexes the wavelength multiplexed light wavelength-multiplexed by the wavelength multiplexing unit 22 and the wavelength multiplexed light input from the wavelength filter 28. The wavelength multiplexed light combined by the 2: 1 multiplexer 29 is output to the optical amplifier 30.
The optical amplifying unit 30 amplifies the wavelength multiplexed light combined by the 2: 1 combining unit 29. The wavelength multiplexed light amplified by the optical amplifying unit 30 is transmitted to the transmission line B-1.

Next, the operation of the wavelength multiplexing transmission apparatus configured as described above will be described. First, the operation of the receiving unit 1 will be described.
FIG. 4 is a flowchart showing the operation of the receiving unit 1 according to Embodiment 1 of the present invention.
In the operation of the receiving unit 1, as shown in FIG. 4, first, the optical amplifying unit 11 amplifies the wavelength multiplexed light input from the transmission path A-1 (step ST41). Here, as shown in FIG. 5, the wavelength multiplexed light input from the transmission line A-1 includes transmission / reception wavelength light branched by the authority and pass-through wavelength light not branched by the authority (wavelength pass-through to the next station). Has been. The wavelength multiplexed light includes wavelength light (dummy light) with a high peak level located on both sides of the band of the modulated light (transmitted / received wavelength light, pass-through wavelength light). This dummy light is for exhibiting the effect of lowering the peak level of the modulated light. The wavelength multiplexed light amplified by the optical amplifying unit 11 is output to the 1: 2 demultiplexing unit 12.

  Next, the 1: 2 demultiplexing unit 12 demultiplexes the wavelength multiplexed light amplified by the optical amplification unit 11 into two (step ST42). One wavelength multiplexed light demultiplexed by the 1: 2 demultiplexing unit 12 is output to the wavelength demultiplexing unit 13, and the other wavelength multiplexed light is output to the transmission unit 2 (wavelength pass-through).

  Next, the wavelength demultiplexing unit 13 demultiplexes the wavelength multiplexed light demultiplexed by the 1: 2 demultiplexing unit 12 into wavelength light for each wavelength (step ST43). The wavelength light separated by the wavelength separation unit 13 is output to the wavelength conversion unit 14.

  Next, the wavelength conversion unit 14 demodulates each wavelength light separated by the wavelength separation unit 13 into an original signal (step ST44). The signal demodulated by the wavelength converter 14 is output as reception data to the signal receiver.

Next, the operation of the transmission unit 2 will be described. First, the normal wavelength multiplexed light transmission operation of the transmitter 2 will be described.
FIG. 6 is a flowchart showing the wavelength multiplexed light transmission operation of the transmitter 2 in the first embodiment of the present invention.
In the wavelength division multiplexed light transmission operation of the transmission unit 2, as shown in FIG. 6, first, the wavelength conversion unit 21 modulates transmission data input from the signal transmission unit into wavelength light for each signal (step ST61). Each wavelength light modulated by the wavelength converting unit 21 is output to the wavelength multiplexing unit 22.

  Next, the wavelength multiplexing unit 22 wavelength-multiplexes each wavelength light modulated by the wavelength conversion unit 21 (step ST62). The wavelength multiplexed light wavelength-multiplexed by the wavelength multiplexing unit 22 is composed of transmission / reception wavelength light as shown in FIG. Further, the wavelength multiplexed light includes dummy light for lowering the peak level of transmitted / received wavelength light. The wavelength multiplexed light multiplexed by the wavelength multiplexing unit 22 is output to the 2: 1 multiplexing unit 29.

  On the other hand, the wavelength filter 28 blocks the wavelength multiplexed light of the wavelength branched by the authorities from the wavelength multiplexed light wavelength-passed by the receiving unit 1 through the 1: 2 demultiplexing unit 23 and the 2: 1 multiplexing unit 27. Then, only the wavelength multiplexed light having a wavelength that is not branched by the authorities is passed through (step ST63). Here, the wavelength filter 28 has a filter characteristic as shown in FIG. 8, and passes only the pass-through wavelength light as shown in FIG. The wavelength multiplexed light that is passed through and output by the wavelength filter 28 is output to the 2: 1 multiplexer 29.

Next, the 2: 1 multiplexer 29 multiplexes the wavelength multiplexed light wavelength-multiplexed by the wavelength multiplexer 22 and the wavelength multiplexed light input from the wavelength filter 28 (step ST64). As shown in FIG. 5 again, the wavelength multiplexed light combined by the 2: 1 multiplexer 29 becomes wavelength multiplexed light composed of transmission / reception wavelength light and pass-through wavelength light. The wavelength multiplexed light combined by the 2: 1 multiplexer 29 is output to the optical amplifier 30.
Next, the optical amplifying unit 30 amplifies the wavelength multiplexed light combined by the 2: 1 multiplexing unit 29 (step ST65). The wavelength multiplexed light amplified by the optical amplifying unit 30 is transmitted to the transmission line B-1.

Next, the operation of checking the input state of wavelength multiplexed light by the transmitter 2 will be described.
FIG. 10 is a flowchart showing the operation of checking the input state of wavelength multiplexed light in the transmitter 2 according to Embodiment 1 of the present invention.
In the operation of confirming the wavelength multiplexed light input state of the transmitter 2, first, as shown in FIG. 10, the monitor 24 monitors the wavelength multiplexed light input from the receiver 1 via the 1: 2 demultiplexer 23. Then, it is determined whether or not wavelength division multiplexed light is normally input (step ST101). That is, the monitor unit 24 determines that the wavelength multiplexed light is normally input when the monitored light level matches the preset expected value, and determines that the wavelength multiplexed light is smaller than the expected value. Is determined not to be entered correctly.

In step ST101, when the monitor unit 24 determines that the wavelength multiplexed light is normally input, the dummy light control unit 25 then controls the dummy light source 26 so as not to emit the dummy light ( Step ST102).
As a result, the dummy light from the dummy light source 26 is not input to the 2: 1 multiplexer 27, and the wavelength filter 28 blocks the wavelength that is branched by the authorities from the wavelength multiplexed light that has been wavelength-passed through from the receiver 1. Output only the wavelength that passes through to the next station. Accordingly, the output of the 2: 1 multiplexer 29 is normal, the peak level and the total level per wavelength of the wavelength multiplexed light transmitted to the transmission line B-1 are constant, and the transmission quality is maintained.

On the other hand, if the monitor unit 24 determines in step ST101 that the wavelength-division multiplexed light is not normally input (the input is cut off), then the dummy light control unit 25 causes the dummy light to be emitted. The dummy light source 26 is controlled (step ST103).
For example, when a failure such as a cable break in the underwater section occurs in the transmission path A-1, and the input to the receiving unit 1 is cut off, the data received by the authorities is cut off for all wavelengths. For this reason, since there is no wavelength-multiplexed light that is subject to wavelength pass-through, the output of the optical amplifying unit 30 becomes lower than the normal value and becomes unstable.

  However, dummy light as shown in FIG. 11 can be output by emitting dummy light from the dummy light source 26 and blocking the wavelength components that are not branched by the authorities in step ST103. At this time, the intensity of the dummy light is adjusted so that the output of the wavelength filter 9 becomes the same as that at the normal time. It is not necessary to prepare dummy light for the number of wavelengths to be transmitted, and there is no problem even if the total level of a plurality of signal wavelengths is combined into one dummy light wavelength within a range in which the entire transmission spectrum shape is maintained. .

  Further, when broadband ASE (Amplified Spontaneous Emission) light is used as dummy light, the ASE light has a lower peak level than modulated light. Therefore, in a system that performs multistage amplification repeater, the gain is concentrated on the modulated light having a strong peak level due to the effect of spectral hole burning, and the total level is not stable. Therefore, in the dummy light source 26 according to the first embodiment, the total level is stabilized by using CW light as dummy light.

  After that, the 2: 1 multiplexing unit 29 combines the wavelength multiplexed light from the wavelength multiplexing unit 22 into the wavelength multiplexed light as shown in FIG. In this way, by supplementing the wavelength-pass-through target wavelength multiplexed light in the input-off state with the dummy light, the output of the optical amplifying unit 30 becomes a value equivalent to the normal value and is stabilized.

  Since the dummy light does not include a signal component, the wavelength conversion unit of the trunk station that branches this dummy light cannot decode the data signal of the transmission source. Therefore, the abnormality can be detected also in the end-to-end system as a whole.

  Thereafter, when the failure of the transmission line A-1 disappears and the wavelength multiplexed light is restored from the input cut-off state to the normal state, the optical level monitored by the monitor unit 24 matches the expected value. It is possible to detect that has been restored to the normal state. This is notified to the dummy light control unit 25, and the dummy light control unit 25 controls the dummy light source 26 so as to stop the emission of the dummy light.

  As described above, according to the first embodiment, the optical level of the wavelength multiplexed light input from the receiving unit 1 is monitored without controlling the amplification factor of the optical amplifying unit 30, and the wavelength multiplexed light is not input. If it is determined that the dummy light is emitted, the output of the optical amplifying unit 30 can be kept constant even when a failure occurs in the transmission line A-1, and the transmission quality is improved. Can be kept high.

Embodiment 2. FIG.
FIG. 13 is a diagram showing a configuration of a wavelength division multiplex transmission apparatus according to Embodiment 2 of the present invention. The wavelength division multiplexing transmission apparatus according to the second embodiment shown in FIG. 13 deletes the dummy light source 26, the 2: 1 multiplexing unit 27, and the wavelength filter 28 from the wavelength division multiplexing transmission apparatus according to the first embodiment shown in FIG. , CW light sources 261-1 to 261 -N and a wavelength selective switch (WSS) 31 are added. Other configurations are the same, and the same reference numerals are given and description thereof is omitted.

  The dummy light control unit 25 uses the pass-through wavelength light as the output light when the result indicates normal (wavelength multiplexed light is normally input) based on the notification of the input state result from the monitor unit 24. The wavelength selective switch 31 is controlled so as to be selected. On the other hand, if the result indicates an abnormality (wavelength multiplexed light is in an input-off state), the wavelength selective switch 31 is controlled so that dummy light is selected as output light.

Each CW light source 261-1 to 261-N emits dummy light. The CW light sources 261-1 to 261-N emit CW light as dummy light in a band that is wavelength-passed by the authorities. Further, the optical level of the dummy light of the CW light sources 261-1 to 261-N is the optical level of the wavelength multiplexed light that is wavelength-passed through by the receiving unit 1 so that the output of the wavelength selective switch 31 is equivalent to that in the normal state. Is preset in advance. The dummy lights emitted by the CW light sources 261-1 to 261-N are output to the wavelength selective switch 31.
The same effect can be obtained even if the dummy light source 26 in the first embodiment is used instead of the CW light sources 261-1 to 261-N.

  The wavelength selective switch 31 receives the wavelength light that has been wavelength-passed through from the receiving unit 1 and the dummy light from the CW light sources 261-1 to 261-N via the 1: 2 demultiplexing unit 23, and the dummy light control unit 25. The output light is selected in accordance with the control by. As shown in FIG. 14, the wavelength selective switch 31 has a function of selecting an optical signal of an arbitrary wavelength input from an arbitrary input port and inserting an optical signal of an arbitrary wavelength (or the reverse direction) 1 It is an optical device with a multi-connection function.

Next, the operation of checking the input state of wavelength multiplexed light by the transmitter 2 will be described.
FIG. 15 is a flowchart showing an operation for confirming the input state of wavelength multiplexed light by the transmitter 2 in Embodiment 2 of the present invention.
In the input state confirmation operation of the wavelength division multiplexed light of the transmission unit 2, first, as shown in FIG. 15, the monitor unit 24 first monitors the wavelength division multiplexed light input from the reception unit 1 via the 1: 2 demultiplexing unit 23. Thus, it is determined whether or not wavelength multiplexed light is normally input (step ST151).

In step ST151, when the monitor unit 24 determines that the wavelength multiplexed light is normally input, the dummy light control unit 25 then selects the wavelength selection switch so that the pass-through wavelength light is selected as the output light. 31 is controlled (step ST152). That is, the dummy light control unit 25 allows the wavelength selective switch 31 to pass all wavelengths to the port to which the wavelength pass-through light is input, and the dummy light from the CW light sources 261-1 to 261-N is transmitted. All wavelengths are blocked for the input port.
Thereby, the dummy light from the CW light sources 261-1 to 261-N is not input to the wavelength selective switch 31, and only the wavelength that passes through the wavelength is output to the next stage. Accordingly, the output of the 2: 1 multiplexer 29 is normal, the peak level and the total level per wavelength of the wavelength multiplexed light transmitted to the transmission line B-1 are constant, and the transmission quality is maintained.

On the other hand, if the monitor unit 24 determines in step ST151 that the wavelength division multiplexed light is not normally input (the input is cut off), then the dummy light control unit 25 uses the dummy light as output light. The wavelength selective switch 31 is controlled so as to be selected (step ST153). That is, the dummy light control unit 25 causes the wavelength selective switch 31 to block all wavelengths for the port to which the wavelength pass-through light is input, and the dummy light from the CW light sources 261-1 to 261-N is transmitted. Each CW light source wavelength is passed through the input port.
Thereby, the wavelength multiplexed light output to the transmission line B-1 is as shown in FIG. 12, and the same effect as in the first embodiment is obtained.

As described above, according to the second embodiment, the CW light sources 251-1 to 261-N and the wavelength selection switch that selects the output light from the input wavelength light are provided. Compared to 1, the 2: 1 multiplexing unit 27, the wavelength filter 28, and the N: 1 multiplexing unit 262 can be eliminated, so that the number of components can be reduced.
The wavelength selective switch 31 has a function of blocking the ports of the connected CW light sources 261-1 to 261-N. Therefore, the output ON / OFF control for the CW light sources 261-1 to 261-N, which is necessary in the first embodiment, can be made unnecessary, and the control can be simplified. In addition, since the insertion loss can be adjusted in units of ports, the level adjustment of the dummy light becomes easy.
Furthermore, since the wavelength pass-through band is fixed by the wavelength filter in the first embodiment, it is difficult to increase the capacity on the branch station side. However, in the second embodiment, the wavelength pass-through band can be arbitrarily changed. Can respond to flexible changes.

Embodiment 3 FIG.
As the dummy light emitted by the dummy light source 26 in the first embodiment, unmodulated spectrum slice light obtained by filtering spontaneous emission light (ASE) with a bandpass filter may be applied.
In this case, as shown in FIG. 16, for example, the dummy light source 26 uses an optical amplifier 263 that generates spontaneous emission light in a wide band by terminating the input without reflection, and spontaneous emission light generated by the optical amplifier 263. A band-pass optical filter 264 that performs band-pass filtering and outputs spectrum slice light in a necessary wavelength band is formed.

  Here, in the CW light sources 261-1 to 261-N assuming that a laser diode emitting at a single wavelength of CW is a light source, the spectral line width of the output laser light is narrow as shown in FIG. For this reason, stimulated Brillouin scattering (SBS), which is one of the nonlinear optical effects, may be caused, and the transmission quality of wavelength multiplexed light may be deteriorated. In addition, since the output laser light is polarized in a specific direction, the gain of modulated light in a fixed polarization direction may decrease or the decrease width may vary with time due to the gain polarization dependence (PDG) of the optical amplifier. is there. However, with spectrum slice light, the spectral line width can be increased as shown in FIG.

  As described above, according to the third embodiment, as the dummy light emitted from the dummy light source 26, the unmodulated spectrum slice light obtained by filtering the spontaneous emission light (ASE) with the bandpass filter is applied. Therefore, the spectral line width can be widened, the transmission quality deteriorates due to the occurrence of stimulated Brillouin scattering (SBS), the gain of the modulated light decreases due to the gain polarization dependence (PDG) of the optical amplifier, and the time variation of the decrease width Etc. can be reduced.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Reception part, 2 Transmission part, 11 Optical amplification part, 12 1: 2 demultiplexing part, 13 Wavelength separation part, 14 Wavelength conversion part, 21 Wavelength conversion part, 22 Wavelength multiplexing part, 23 1: 2 Demultiplexing part, 24 Monitor unit, 25 dummy light control unit, 26 dummy light source, 27 2: 1 multiplexing unit, 28 wavelength filter, 29 2: 1 multiplexing unit, 30 optical amplification unit, 31 wavelength selective switch, 261-1 to 261-N CW light source, 262 N: 1 multiplexer, 263 optical amplifier, 264 band pass filter.

Claims (4)

The received wavelength multiplexed light is demultiplexed, one is demodulated and the received data is output and the other is passed through, and the wavelength light modulated by the input transmission data and the wavelength light passed through from the receiving unit are combined. In a wavelength division multiplex transmission device including a transmission unit that transmits and transmits wavelength division multiplexed light,
A dummy light source that emits / extinguishes dummy light;
A monitor for monitoring the optical level of the received wavelength multiplexed light;
A dummy light control unit that causes the dummy light source to emit dummy light when it is determined that the wavelength multiplexed light is in an input-off state based on the light level monitored by the monitor unit;
A multiplexing unit that combines the modulated wavelength light and the dummy light emitted by the dummy light source;
The wavelength division multiplexing transmission apparatus, wherein the transmission unit transmits the wavelength division multiplexed light generated by the multiplexing unit. The received wavelength multiplexed light is demultiplexed, one is demodulated and the received data is output and the other is passed through, and the wavelength light modulated by the input transmission data and the wavelength light passed through from the receiving unit are combined. In a wavelength division multiplex transmission device including a transmission unit that transmits and transmits wavelength division multiplexed light,
A dummy light source that emits dummy light; and
A monitor for monitoring the optical level of the received wavelength multiplexed light;
A wavelength selective switch that inputs wavelength light passed through from the receiver and dummy light from the dummy light source, and selects output light;
A dummy light control unit that causes the wavelength selective switch to select dummy light as output light when it is determined that the wavelength-multiplexed light is in an input cut-off state based on the light level monitored by the monitor unit;
A multiplexing unit that combines the modulated wavelength light and the output light from the wavelength selective switch;
The wavelength division multiplexing transmission apparatus, wherein the transmission unit transmits the wavelength division multiplexed light generated by the multiplexing unit. 3. The wavelength division multiplexing transmission apparatus according to claim 1, wherein the dummy light source emits CW (Continuous Wave) light as dummy light. 2. The wavelength division multiplexing transmission apparatus according to claim 1, wherein the dummy light source emits spectrum slice light as dummy light.

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