JP3866421B2 - Wavelength division multiplexing optical transmission system, optical receiver, optical amplifier, and optical wavelength division multiplexing transmitter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wavelength division multiplexing optical transmission system, and an optical receiver, an optical amplifier, and an optical wavelength division multiplexing transmitter used in this system.
[0002]
[Prior art]
With the recent development of communication systems, there is a strong demand for an increase in transmission capacity. Under these circumstances, wavelength division multiplexing optical transmission systems are attracting attention and are being actively studied.
[0003]
In a wavelength division multiplexing optical transmission system, a plurality of optical signals having different wavelengths are multiplexed and transmitted through the same transmission path. This feature provides the advantage of a larger transmission capacity than conventional single-wavelength optical communication systems, but also has some problems. Among these, what was pointed out by the present inventors will be described below.
[0004]
(1) In a wavelength division multiplexing optical transmission system, a plurality of repeaters are used to realize long-distance communication. In the repeater, an optical amplifier capable of amplifying a plurality of optical signals having different wavelengths at once is used. Note that “optical amplifier” in the text means an amplifier that can amplify an optical signal as it is without converting the optical signal into an electrical signal, such as an EDFA (erbium-doped optical fiber amplifier).
[0005]
By the way, such an optical amplifier is often used in a gain saturation state (a state in which the gain decreases as the input signal power increases), particularly when used in a repeater. This is because, in any one of the plurality of repeaters, when the gain of the optical amplifier decreases due to deterioration or failure, the subsequent optical amplifier compensates for the gain deterioration.
[0006]
However, when a plurality of gain-saturated optical amplifiers are connected, a phenomenon occurs in which the signal power of each channel rapidly changes when the number of channels of signals propagating in the optical amplifier changes. This will be described in detail below.
[0007]
FIG. 8 shows a configuration of a conventional wavelength division multiplexing optical transmission system. In FIG. 8, optical signals λ1 to λn having different wavelengths transmitted from a plurality of optical transmitters T1 to Tn in the wavelength division multiplex transmission apparatus 1 are combined in the wavelength division unit 2, and the wavelengths are transmitted through the relay transmission path unit 3. It is transmitted to the multiplex receiver 4. The wavelength division multiplexed light is separated into optical signals λ1 to λn by the wavelength separator 5, and received by the optical receivers R1 to Rn, respectively, and data # 1 to #n and clocks # 1 to #n are reproduced.
[0008]
As shown in FIG. 9, the wavelength multiplexing unit 2 combines the optical signals λ1 to λn with an optical multiplexer, amplifies them with an optical amplifier, and sends them to the transmission line. Further, as shown in FIG. 10, the wavelength demultiplexing unit 5 amplifies an incoming wavelength multiplexed signal with an optical amplifier, then branches it into optical signals for n channels by an optical branching unit, and outputs light having wavelengths λ1 to λn, respectively. Optical signals having wavelengths of λ1 to λn are branched and output through the filters F1 to Fn.
[0009]
8 includes optical linear repeaters A1 to Ak each including an optical amplifier, and each optical amplifier is in a gain saturation state. At this time, fluctuations in signal power when the number of transmission channels changes will be described with reference to FIG. FIG. 11A is a diagram showing the behavior of the optical amplifier in the optical repeater located in the preceding stage of the relay transmission path unit 3, and FIG. 11B is a diagram showing the behavior of the latter optical amplifier. For simplicity, in the following description, it is assumed that optical signals (wavelengths λ1 and λ2) having the same transmission output power are multiplexed (n = 2) and that the gain of the optical amplifier has no wavelength dependency.
[0010]
In FIG. 11A, when the signal of wavelength λ2 falls, the signal power input to the preceding optical amplifier falls from Pa (λ1) + Pa (λ2) to Pa (λ1), but the gain rises from Ga1 to Ga2. . As a result, the output power of the remaining optical signal having the wavelength λ1 increases. When the optical signal with wavelength λ2 is restored, the gain returns to the original Ga1, and the output power of the optical signal with wavelength λ1 decreases (returns to the original).
[0011]
What is important here is that the optical signal power (total) output from the optical amplifier in the previous stage does not change because the gain changes automatically. As a result, an optical signal having the same intensity is input to the subsequent optical amplifier regardless of the increase or decrease in the number of channels. In this way, the optical signal power finally input to the wavelength division multiplex receiver 4 is kept constant.
[0012]
However, as the number of channels decreases / increases, the signal power of each channel input to the optical receiver increases / decreases. Further, the speed of this power fluctuation increases as the number of stages of the optical amplifier through which the optical signal passes increases. The literature reporting the speed of signal power change when the number of channels changes is “Fast Power Transients in Optically Amplified Multiwavelength Optical Networks”, Optical Fiber Communication Conference, vol. 2, PD-31 (1996) by JLZsykind et al. . This document shows that the speed of change of the output optical power is several tens to 100 μsec when one optical amplifier is used, but increases as the number of optical amplifiers increases.
[0013]
In summary, in a wavelength multiplexing optical transmission system, when the number of channels of an optical signal of a wavelength multiplexed light changes due to loss or addition of an optical signal of a certain wavelength, the power of the optical signal of each wavelength is changed to an optical amplifier. The phenomenon of fluctuating at a speed depending on the number of units occurs.
[0014]
Usually, the optical receiver has an AGC (Automatic Gain Control) function so that the reception function operates normally over a predetermined reception power range. However, when the received power fluctuates so rapidly that the AGC cannot follow, transmission quality such as a reception error (burst error) may be deteriorated.
[0015]
(2) In the optical wavelength multiplexing system, an optical amplifier is also used as a booster amplifier in the wavelength multiplexer 2. An example of an optical amplifier used for such use is shown in FIG. That is, this optical amplifier outputs an optical signal input through the optical isolator 12 from the optical isolator 15 through the multiplexer 13 and the amplification fiber 14. At this time, the pumping light generated in the pumping LD (semiconductor laser) 16 is incident on the multiplexer 13 to amplify the optical signal. Here, the operation control of the excitation LD 16 is performed by the control circuit 17.
[0016]
Incidentally, in the configuration of FIG. 8, there is a case where one of the optical transmitters needs to be replaced due to a cause such as a failure. It takes a certain amount of time for the optical transmitter activated after replacement to become stable and to output an optical signal having a certain wavelength. However, before reaching the stable state, the output light of this optical transmitter may interfere with the output light of other optical transmitters, thereby degrading crosstalk. This will be described in detail with reference to FIG.
[0017]
Suppose now that the optical transmitter Tn has been replaced and activated. The optical transmitter generally obtains output light having a desired wavelength by controlling the temperature of a chip that oscillates laser. For this reason, an optical signal having a wavelength (λ0) corresponding to room temperature is output immediately after the optical transmitter Tn is started up. As the optical transmitter Tn warms from this state, the output wavelength shifts to a stable point and finally settles at the wavelength λn.
[0018]
However, if there is an optical transmitter Tm that operates stably at a wavelength longer than λn at this time, the output optical wavelength of the optical transmitter Tn crosses the output optical wavelength λm of the optical transmitter. Therefore, the output lights of the optical transmitters Tn and Tm interfere with each other, and the crosstalk deteriorates. Of course, this also occurs in a wavelength region corresponding to a temperature lower than room temperature.
[0019]
In order to prevent the influence of the crosstalk degradation due to this wavelength shift, conventionally, the output of the optical amplifier is cut off until the exchanged optical transmitter rises and settles to the stable point, and the output is turned on after the stabilization. It was. However, in order to realize such a method, the optical disconnection circuit 18 must be provided in the optical amplifier, resulting in an increase in cost. Furthermore, since the unit replacement operator must monitor the output of the optical transmitter after replacement and perform the on / off operation of the optical amplifier, it takes extra time.
[0020]
[Problems to be solved by the invention]
As described above, in the conventional wavelength division multiplexing optical transmission system, when the number of channels of the optical signal propagating through the optical repeater changes, the power of the optical signal of each channel changes rapidly, so that a code error, etc. There is a problem that the transmission quality is likely to deteriorate.
[0021]
Further, the optical transmitter causes a wavelength shift before reaching a stable operation state. In the conventional optical wavelength division multiplex transmission apparatus, in order to prevent the transmission quality from being deteriorated due to the wavelength shift, it is necessary to monitor the output of the exchanged optical transmitter and turn on / off the optical amplifier. For this reason, the burden on the operator is large and the cost is increased.
[0022]
The present invention has been made for the above circumstances, and a first object of the present invention is to provide a wavelength division multiplexing optical transmission system and an optical receiver that do not deteriorate transmission quality even when the number of channels of a propagating optical signal changes. There is to do.
[0023]
A second object of the present invention is to provide an optical amplifier and an optical wavelength division multiplex transmitter capable of suppressing degradation of transmission quality due to wavelength shift of an optical transmitter without labor and cost.
[0024]
[Means for Solving the Problems]
In order to achieve the first object, the first aspect of the present invention provides a plurality of optical transmitters that output optical signals of different wavelengths, and wavelength multiplexing for wavelength multiplexing optical signals output from these optical transmitters. An optical transmission device that sends wavelength multiplexed light to an optical transmission line,
Light comprising: a wavelength demultiplexing unit that demultiplexes the wavelength-multiplexed light that has arrived via the optical transmission line; and a plurality of optical receivers that regenerate reception information from the demultiplexed optical signals output from the wavelength demultiplexing unit. In a wavelength division multiplexing optical transmission system comprising a receiving device,
Each of the separated optical signals is input to each of the plurality of optical receivers via one or more optical amplifiers set in a gain saturation state.
[0025]
By taking such means, the wavelength division multiplexed light that has arrived at the optical receiving device from the optical transmitting device via the optical transmission path is separated into optical signals having wavelengths of the respective channels by the wavelength demultiplexing unit. The optical signals of these wavelengths are input to the optical receivers of the respective channels through one or a plurality of optical amplifiers connected in series, and the received information is reproduced.
[0026]
Here, the optical amplifier is set to a gain saturation state. For this reason, the gain of the optical amplifier decreases or increases according to the magnitude of the power of the separated optical signal of each wavelength, and as a result, the power fluctuation of the optical signal of each wavelength is suppressed. Therefore, even if the number of transmission channels changes due to a drop / restoration of the optical signal, a constant level of the optical signal is always input to the optical receiver, so that it is possible to suppress deterioration in transmission quality. Become.
[0027]
Furthermore, as described in the prior art page, the rate of change in the power of the optical signal increases as the number of optical amplifiers passing through increases. By utilizing this fact, by increasing the number of optical amplifiers in the optical receiver, even if the optical signal power of each wavelength varies rapidly during transmission, it is possible to follow this.
[0028]
That is, conventionally, by setting an optical amplifier provided in the middle of an optical transmission line to a gain saturation state, fluctuations in the power of each optical signal when the number of channels changes are caused. Therefore, in the present invention, an optical amplifier in a gain saturation state is newly provided at the subsequent stage of the wavelength separation unit so that the power of the optical signal having a single wavelength after separation is made constant.
[0029]
In the first invention, the optical transmission apparatus is provided with error correction coding means using, for example, a Reed-Solomon code, and the optical reception apparatus is provided with error correction decoding means. This makes it possible to compensate for the effect of suppressing the transmission quality degradation caused by the optical amplifier and to reduce the number of optical amplifiers according to the performance of the optical receiver, so that the system can be provided at a lower cost. Become.
[0030]
In order to achieve the second object, the second invention is a plurality of optical transmitters that output optical signals of different wavelengths, and optical transmitters connected to and connected to these optical transmitters, respectively. A plurality of optical amplifiers for amplifying the output light from each of the optical amplifiers, and a wavelength multiplexing unit for wavelength-multiplexing the optical signal after passing through these optical amplifiers
For each of the plurality of optical amplifiers,
An optical bandpass filter that transmits only an optical signal having a wavelength corresponding to a stable output wavelength of each of the connected optical transmitters is provided.
[0031]
More specifically,
For each of the plurality of optical amplifiers,
A light source for generating and outputting excitation light; an amplification optical fiber for receiving the excitation light and an input optical signal; and an amplification optical fiber provided between the light source and the amplification optical fiber to transmit the excitation light. A reflection type filter that reflects an optical signal having a specific wavelength among the input optical signals that are incident on the optical fiber and that are incident on the amplification optical fiber; and first, second, and third ports; An optical signal from the optical transmitter input from the first port is incident on the amplification optical fiber from the second port, and an input optical signal reflected by the reflective filter is input to the second port. An optical circulator that outputs from the port to the wavelength multiplexing unit via the third port, and sets the reflection wavelength of the reflection type filter in association with the stable output wavelength of each connected optical transmitter And wherein the door.
[0032]
With this configuration, in the optical amplifier, only an optical signal having a specific wavelength is amplified and output from the third port of the optical circulator. In the optical wavelength division multiplexing apparatus, the output of each optical transmitter is multiplexed through the optical amplifier. Since the reflection wavelength of the reflective filter is set in correspondence with the stable output wavelength of each connected optical transmitter, only the output of the stabilized optical transmitter is input to the wavelength multiplexing unit. become.
Therefore, there is no possibility that the outputs of different optical transmitters interfere with each other, and it becomes possible to prevent the deterioration of crosstalk.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a configuration of a wavelength division multiplexing optical transmission system according to the first embodiment of the present invention. 1, the same parts as those in FIG. 8 are denoted by the same reference numerals, and only different parts will be described here.
[0034]
That is, the wavelength division multiplex receiver 6 of the present embodiment passes the optical signals of the wavelengths λ1 to λn after being separated by the wavelength separator 5 to the optical receivers R1 to Rn via the compensating optical amplifiers 71 to 7n, respectively. It is supposed to be entered. Here, each of the compensation optical amplifiers 71 to 7n includes one or more (not necessarily the same number of) optical amplifiers connected in series, and these optical amplifiers all have a gain. It is set to saturation.
[0035]
The operation of the compensating optical amplifiers 71 to 7n in such a configuration will be described below. That is, an optical signal having a single wavelength is input to each of the compensation optical amplifiers 71 to 7n, not the wavelength multiplexed light. For example, taking an optical signal of wavelength λ1 as an example, the gain of the preceding optical amplifier in the compensating optical amplifier 71 changes according to the change in input signal power as shown in FIG. That is, when the input signal power is low, the gain increases (Gb1) when (Pb1 (λ1)), and when the input signal power is high (Pb2 (λ1)), the gain decreases (Gb2). In this way, each amplifier in the compensation optical amplifier 71 operates so that its output power is always constant.
[0036]
Therefore, as shown in FIG. 2B, the change in input power is gradually compressed from the preceding optical amplifier to the subsequent optical amplifier, and a constant output power can be obtained. That is, even if the signal power of each channel changes during transmission due to the increase or decrease in the number of channels, it is possible to always obtain a constant signal power at the output stage of the compensating optical amplifiers 71 to 7n. Further, the speed of gain fluctuation in the optical amplifier becomes faster as the number of (optical amplifiers) connected in series increases, so that by increasing the number of optical amplifiers in the compensating optical amplifiers 71 to 7n, high-speed power can be obtained. Fluctuations can be easily dealt with.
[0037]
For these reasons, fluctuations in the input power to the optical receivers R1 to Rn, which occur when the number of channels changes during transmission, are suppressed, and it is possible to prevent deterioration in transmission quality due to power fluctuations.
[0038]
(Second Embodiment)
FIG. 3 shows the configuration of a wavelength division multiplexing optical transmission system according to the second embodiment of the present invention. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and only different parts will be described here.
[0039]
That is, in the wavelength division multiplexing optical transmission system according to the present embodiment, for each wavelength, the error correction units 91 to 9n are provided on the wavelength division multiplexing transmission apparatus (symbol is 8) side, and the wavelength multiplexing receiving apparatus (symbol is 11). ) Side is provided with error correction units 101 to 10n, respectively. For example, a Reed-Solomon code is used as an encoding method for performing error correction.
[0040]
With this configuration, it is possible to correct an instantaneous error that still occurs even when the compensating optical amplifiers 71 to 7n are used. That is, the gain fluctuation compensation effect by the compensating optical amplifiers 71 to 7n can be complemented. From the opposite viewpoint, the number of optical amplifiers in the compensating optical amplifiers 71 to 7n can be reduced according to the error correction capability of the error correction units 91 to 9n and 101 to 10n. As a result, the cost of the system can be reduced.
[0041]
Here, another configuration example of the wavelength division multiplexing optical transmission system to which the present invention is applied is shown in FIG. The system of FIG. 4 includes a wavelength division multiplexing transmission apparatus 1-1 that multiplexes and transmits optical signals having wavelengths λ1 to λh, and a wavelength division multiplexing transmission apparatus 1-2 that multiplexes and transmits optical signals having wavelengths λh + 1 to λn. And after relaying the output light of each of the wavelength division multiplexing transmitters 1-1 and 1-2 by the repeater transmission line sections 3-1, 3-2 (equipped with optical linear repeaters B1 to Bi and C1 to Cj, respectively) The signals are coupled by the optical coupler 19 and further transmitted to the wavelength division multiplexing receiver 6 via the relay transmission path section 3-3 (including the optical linear repeaters A1 to Ak).
[0042]
In such a configuration, when the output light from one wavelength multiplexing transmission device disappears due to a device failure or fiber breakage, the sum of the optical power given to the relay transmission path section 3-3 decreases, and the other This causes power fluctuations in the output light from the wavelength division multiplex transmitter. However, even in such a case, the power of the optical signal of each wavelength input to the optical receivers R1 to Rn is kept constant by the action of the compensating optical amplifiers 71 to 7n in the wavelength division multiplexing receiver 6. It becomes possible to suppress degradation of transmission quality. Similarly, even when the lost optical signal is recovered, power fluctuations occur at the stage of reaching the wavelength division multiplex receiver 6, but at the stage of input to the optical receivers R1 to Rn, the power of the optical signal of each wavelength. Is kept constant, and transmission quality deterioration can be suppressed.
[0043]
(Third embodiment)
Next, FIG. 5 shows a configuration of an optical amplifier according to the third embodiment of the present invention. In FIG. 5, the same parts as those in FIG. In FIG. 5, the excitation light output from the excitation LD (semiconductor laser) 16 under the control of the control circuit 17 is transmitted through the reflection filter 20 and guided to the amplification fiber 14. As a result, the amplification fiber 14 is in an excited state.
[0044]
On the other hand, the optical signal is first input to the port 1 of the optical circulator 21, enters the amplification fiber 14 from the port 2, is amplified, and is input to the reflection filter 20. Then, only the optical signal having a specific wavelength is reflected by the reflection filter 20, amplified again by the amplification fiber 14, and output from the port 2 of the optical circulator 21 through the port 3.
[0045]
FIG. 6 shows the characteristics of a fiber Bragg grating (hereinafter abbreviated as FBG) which is an example of a reflective filter. In the FBG, as shown in FIG. 6A, incident light is separated into reflected light having a specific wavelength and transmitted light having other wavelengths. The reflection characteristics of the reflected light are as shown in FIG. 6B, where only the optical signal having a wavelength within the reflection region at the center of the graph is reflected, and most of the optical signal having a wavelength outside this region is reflected. Is done. Thus, the FBG has the following characteristics <1> to <4> that are not found in other optical filters such as a dielectric multilayer filter.
<1> The boundary between the reflection region and the transmission region is extremely steep.
<2> Crosstalk between reflected light and transmitted light is large.
<3> The band of the reflection region is flat.
<4> Good temperature characteristics.
[0046]
Therefore, by adopting the above configuration, it is possible to provide an optical amplifier that can output only an optical signal having a predetermined wavelength. Here, the narrower the band (Δλ) of the reflection region, the higher the wavelength selectivity. Currently, a bandwidth of about 0.4 nm is possible. In the above configuration, since the number of parts can be reduced as compared with the conventional optical amplifier, the size and cost can be reduced, and the reliability can be improved. Furthermore, since bidirectional amplification is performed using the amplification fiber, it is possible to improve the amplification gain.
[0047]
Next, FIG. 7 shows the configuration of a wavelength division multiplexing transmitter using the optical amplifier having the above configuration. That is, the wavelength division multiplexing transmission apparatus of this embodiment guides the output light (wavelengths λ1 to λn) from the optical transmitters T1 to Tn to the wavelength division multiplexer 2 via the optical amplifiers D1 to Dn having the configuration shown in FIG. It has become. Here, the reflection wavelengths of the reflection filters in the optical amplifiers D1 to Dn are set to the output light wavelengths λ1 to λn of the optical transmitters connected thereto, respectively.
[0048]
With this configuration, even if a wavelength shift occurs in any one of the optical transmitters, the optical signal in the middle of the shift is blocked by the optical amplifier immediately after and is not input to the wavelength multiplexer 2. Thereby, it becomes possible to eliminate interference between output lights between different optical amplifiers, and crosstalk between wavelengths is maintained.
[0049]
Therefore, when replacing the optical transmitter, it is not necessary to monitor the output of the newly mounted optical transmitter, disconnect the output until it is stabilized, and release the disconnection after stabilization. As a result, it is possible to save the labor of the operator, and it becomes unnecessary to provide the output disconnection circuit 18, so that the cost of the apparatus can be reduced and the apparatus can be simplified.
[0050]
The present invention is not limited to the above embodiment.
For example, in the optical amplifier having the configuration shown in FIG. 5, the output light from the port 3 of the optical circulator 21 may be output through an appropriate filter. By doing so, it becomes possible to prevent noise light, leakage light, and the like.
In addition, various modifications can be made without departing from the scope of the present invention.
[0051]
【The invention's effect】
As described above in detail, according to the first aspect of the present invention, since the optical signals of individual wavelengths separated by the wavelength separation unit are respectively passed through the optical amplifiers in the gain saturation state, Even if the number of signal channels changes, it is possible to provide a wavelength division multiplexing optical transmission system and an optical receiver that do not cause deterioration in transmission quality.
[0052]
Further, according to the second aspect of the present invention, since the optical amplifier has a filtering function, among the output lights from the plurality of optical transmitters, only a stable optical signal is amplified and multiplexed. It is possible to provide an optical amplifier and an optical wavelength division multiplex transmitter capable of suppressing the degradation of transmission quality due to the wavelength shift of the optical device without taking time and cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a wavelength division multiplexing optical transmission system according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a state in which gain changes in accordance with a change in input signal power in an optical amplifier.
FIG. 3 is a diagram showing a configuration of a wavelength division multiplexing optical transmission system according to a second embodiment of the present invention.
FIG. 4 is a diagram showing another configuration example of a wavelength division multiplexing optical transmission system to which the present invention is applied.
FIG. 5 is a diagram showing a configuration of an optical amplifier according to a third embodiment of the present invention.
FIG. 6 is a view showing characteristics of a fiber Bragg grating.
FIG. 7 is a diagram showing a configuration of a wavelength division multiplexing transmission apparatus according to a third embodiment of the present invention.
FIG. 8 is a diagram showing a configuration of a conventional wavelength division multiplexing optical transmission system.
FIG. 9 is a diagram showing a configuration of a wavelength multiplexing unit 2;
10 is a diagram showing a configuration of a wavelength separation unit 5. FIG.
FIG. 11 is a diagram showing how the signal power fluctuates when the number of transmission channels changes.
FIG. 12 is a diagram showing a configuration of an optical amplifier used as a booster amplifier in the wavelength multiplexer 2;
FIG. 13 is a diagram illustrating a state in which crosstalk occurs between outputs of different optical transmitters in a conventional wavelength division multiplexing optical transmission system.
[Explanation of symbols]
1 (1-1, 1-2) ... wavelength division multiplexing transmitter 2 (2-1, 2-2) ... wavelength multiplexing section 3 (3-1 to 3-3) ... relay transmission path section 4 ... conventional wavelength multiplexing Receiving device 5 ... wavelength demultiplexing unit 6 ... wavelength multiplexing receiving devices 71 to 7n according to the first embodiment of the present invention ... compensating optical amplifiers T1 to Tn ... optical transmitters R1 to Rn ... optical receivers A1 to Ak, B1 to Bi, C1 to Cj, optical linear repeater 8, wavelength division multiplexing transmitters 91 to 9n according to the second embodiment of the present invention, error correction units 101 to 10n, error correction unit 11, and so on. WDM receivers 12, 15... Optical isolator 13 .. multiplexer 14... Amplification fiber 16 .. pumping LD (semiconductor laser) according to the embodiment.
DESCRIPTION OF SYMBOLS 17 ... Control circuit 18 ... Output disconnection circuit 19 ... Optical coupler 20 ... Reflective filter D1-Dn ... Optical amplifier concerning the 3rd Embodiment of this invention

Claims (5)

Light that includes a plurality of optical transmitters that output optical signals of different wavelengths, and a wavelength multiplexing unit that wavelength-multiplexes the optical signals output from the plurality of optical transmitters, and transmits the wavelength multiplexed light to the optical transmission line A transmitting device;
A plurality of optical repeaters provided in the optical transmission line, each including an optical amplifier that amplifies and outputs the wavelength multiplexed light in a gain saturation state;
A wavelength demultiplexing unit that demultiplexes the wavelength-multiplexed light that has arrived via the optical transmission path for each wavelength, and a plurality of optical signals that are output from the wavelength demultiplexing unit are set in a gain saturation state. A plurality of gain fluctuation compensators that are sequentially amplified by an optical amplifier and output at a predetermined power; and a plurality of optical receivers that respectively reproduce received information from a plurality of optical signals output from the plurality of gain fluctuation compensators. A wavelength division multiplexing optical transmission system comprising: an optical receiving device. The optical transmission device further includes a plurality of error correction coding means for adding error correction information to transmission information given to the plurality of optical transmitters,
2. The wavelength according to claim 1, wherein the optical receiving device further includes a plurality of error correction decoding units that decode reception information reproduced by the optical receiver based on the error correction information. Multiplex optical transmission system. In an optical receiver for receiving wavelength multiplexed light, in which a plurality of optical signals having different wavelengths are multiplexed and repeatedly amplified and transmitted by a plurality of optical amplifiers in a gain saturation state in an optical transmission line,
A wavelength separator that separates each wavelength a wavelength division multiplexed light arriving through the optical transmission path,
A plurality of gain fluctuation compensators that sequentially amplify each of a plurality of separated optical signals output from the wavelength separator by a plurality of optical amplifiers set in a gain saturation state, and output at a predetermined power;
An optical receiving apparatus comprising: a plurality of optical receivers that respectively reproduce reception information from a plurality of optical signals output from the plurality of gain fluctuation compensating units. Light that includes a plurality of optical transmitters that output optical signals of different wavelengths, and a wavelength multiplexing unit that wavelength-multiplexes the optical signals output from the plurality of optical transmitters, and transmits the wavelength multiplexed light to the optical transmission line An optical receiver used in a wavelength division multiplexing optical transmission system, comprising: a transmission apparatus; and a plurality of optical repeaters provided in the optical transmission line, each having an optical amplifier that amplifies and outputs the wavelength division multiplexed light in a gain saturation state. Because
A wavelength separation unit that separates the wavelength multiplexed light that has arrived via the optical transmission path for each wavelength;
A plurality of gain fluctuation compensators that sequentially amplify each of a plurality of separated optical signals output from the wavelength separator by a plurality of optical amplifiers set in a gain saturation state, and output at a predetermined power;
A plurality of optical receivers that respectively reproduce received information from a plurality of optical signals output from the plurality of gain fluctuation compensation units ;
Wherein the plurality of the received information reproduced by the optical receiver, an optical receiver device being characterized in that respectively the error correction information such that includes a plurality of error correction decoding means for decoding the original. When optically coupling a plurality of optical transmission lines, each of which transmits a wavelength-multiplexed light in which a plurality of optical signals having different wavelengths, are multiplexed by an optical coupler and relayed by a single optical transmission line, before the optical coupling Optical reception used in a wavelength division multiplexing optical transmission system in which wavelength multiplexed light is repeatedly amplified and transmitted by a plurality of gain-saturated optical amplifiers on a plurality of optical transmission paths and a single optical transmission path after optical coupling. A device,
A wavelength separation unit that separates the wavelength division multiplexed light that has arrived via the single optical transmission line for each wavelength;
A plurality of gain fluctuation compensators that sequentially amplify each of a plurality of separated optical signals output from the wavelength separator by a plurality of optical amplifiers set in a gain saturation state, and output at a predetermined power;
An optical receiving apparatus comprising: a plurality of optical receivers that respectively reproduce reception information from a plurality of optical signals output from the plurality of gain fluctuation compensating units.

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