JP4522894B2 - Wavelength division multiplexing communication system. - Google Patents

Description

  The present invention relates to a wavelength division multiplexing system, and more particularly to a wavelength division multiplexing system having a function of setting gain of a preamplifier using ASE (Amplified Spontaneous Emission) light.

  In recent years, wavelength division multiplexing (WDM) technology has been widely used as an optical transmission technology. The WDM technology is a method in which light having different wavelengths (for example, 40 to 1OO waves) is multiplexed and a plurality of signals are simultaneously transmitted through one optical fiber.

  A conceptual configuration of such a WDM transmission system is shown in FIG. FIG. 1A shows a system configuration, and FIG. 1B is a diagram for explaining a change in signal level.

  As shown in FIG. 1A, nodes 100 and 120 are provided on the optical fiber transmission lines 130 and 131 of the WDM transmission system, and a relay node 110 is provided between the nodes 100 and 120. The nodes 100 and 120 have an OADM (0ptical Add Drop Multiplexing) function that allows an optical signal having a specific wavelength to pass (transmit), drop (drop), or add (add) to a WDM signal. It has an OADM node.

  The OADM nodes 100 and 120 are provided with a preamplifier unit 1 on the input side and a postamplifier unit 5 on the output side. The relay node 110 has an inline amplifier.

  In the OADM nodes 100 and 120, the wavelength division multiplexed optical signal is separated for each wavelength by the demultiplexing circuit 2. Then, the insertion / branching circuit 3 transmits, branches, or inserts each wavelength. Further, the wavelength transmitted through the OADM node 100 by the multiplexing circuit 4 and the wavelength inserted by the inserting / branching circuit 3 are multiplexed, input to the postamplifier unit 5, and transmitted to the optical fiber transmission line 130.

  Here, in the WDM transmission system in which the optical amplifiers (preamplifier unit 1, postamplifier unit 5 and inline amplifier unit 110) are arranged on the optical fiber transmission line 130, at the time of initial start-up, failure and line disconnection, the wavelength It is necessary to set these optical amplifiers so that they have a predetermined gain at the time of resetting or when the maintenance person mistakenly removes the main signal system cable.

  It is known that such gain setting is performed by generating noise light (ASE: Amplified Spontaneous Emission) having a level equivalent to one wave in the post-amplifier unit 5 on the transmission side and using that light.

  For example, as a method of setting the gain of an amplifier using ASE light, a preamplifier having two control modes of AGC (Automatic gain Control) mode and ALC (Automatic Level Control) mode, and an ASE mode (an output level of ASE light) Invention of a method for setting the gain of the preamplifier of the next-stage node using the ASE light using a post-amplifier having two control modes of AGC mode and AGC mode (Patent Document) 1) An invention for setting the gain of a receiving amplifier (preamplifier) of the succeeding station by outputting the ASE light by blocking the transmitted light and the inserted light from the preceding station based on the ASE light output request from the succeeding station (Patent Document) 2) etc.

  An example of a method for starting up a WDM system using ASE light has been proposed by the present applicant in a previous patent application (Japanese Patent Application No. 16-007857).

  That is, as shown in FIG. 1B, it is possible to obtain the required gain (gain) of the amplifier at the subsequent station by starting up using ASE light. In FIG. 1B, (a) is the output level of the ASE light from the post-amplifier unit 5 of the OADM node 100. (B) is an input level of the in-line amplifier unit 110, and the input level is lowered due to a transmission line loss while passing through the optical fiber transmission line 130. FIG. The in-line amplifier unit 110 detects this input ASE light and amplifies it to a predetermined gain. The output level is adjusted to correspond to the output level of the post-amplifier unit 5 of the OADM node 100, for example, as shown in (c).

  Next, the level of the ASE light transmitted from the in-line amplifier unit 110 is similarly lowered by the transmission line loss of the optical fiber transmission line 131 until reaching the preamplifier unit 1 of the OADM node 120. It becomes. The OADM node 120 detects this input ASE light and adjusts the preamplifier unit 1 so as to obtain a predetermined gain. Therefore, the required gain can be obtained as shown in (e).

  Here, in the WDM transmission system, there is a demand to arrange the wavelengths with high density in the same band for the purpose of reducing the transmission cost per wavelength and expanding the transmission signal band. It has been proposed to use an interleaver as a method for meeting such demands. The interleaver is an optical component having reversibility, which includes, as an example, a wavelength separation unit including two deflection separators and an etalon unit as described in Patent Document 3 as a main element. The interleaver can demultiplex the wavelength multiplexed light into odd wavelength (odd channel wavelength) light and even wavelength (even channel wavelength) light. (Patent Document 3, FIG. 2 and [0021] to [0031]) Furthermore, since it has reversibility, it is also possible to multiplex and output odd wavelength light and even wavelength light input alternately.

  However, as a characteristic of the interleaver, when the wavelength multiplexed light is demultiplexed into odd wavelength light and even wavelength light, the output level is halved (the level is reduced by about 3 dB). For this reason, there is a problem that the gain setting of the conventional preamplifier described above cannot be performed as it is.

  In recent years, in a wavelength division multiplexing system, it has been proposed to use VIPA as a dispersion compensator for adjusting each wavelength to fall within a predetermined reception level range in an OADM node. Such a VIPA also has a characteristic that the level is halved at a predetermined wavelength interval like the interleaver.

Therefore, when the gain of the preamplifier is adjusted by the ASE light in the transmission line section in which the VIPA is inserted, there is a problem that the preamplifier gain cannot be set as it is as in the case of using the interleaver described above.
Japanese Patent Laid-Open No. 2004-23437 JP 2004-187071 A

  Accordingly, an object of the present invention is to solve the problem in the gain setting of a preamplifier when an interleaver or VIPA is used in a WDM transmission system.

  In a WDM transmission system that solves the problems of the present invention, as a first aspect, in the wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line and an optical signal that is wavelength division multiplexed is transmitted. Each of the OADM nodes includes a first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength, and an optical signal of an odd wavelength and an even wavelength group that is divided and output by the interleaver. Each of the first and second systems is wavelength-multiplexed of the divided odd wavelength group or even wavelength group with a predetermined gain. A preamplifier that amplifies the optical signal, a wavelength multiplexing / separation unit that wavelength-separates the wavelength-multiplexed optical signal amplified by the preamplifier, and a wavelength multiplexing / separation unit. Further, among the plurality of wavelengths, a branching / inserting unit that transmits or branches a predetermined wavelength, a wavelength multiplexing unit that wavelength-multiplexes the transmitted and inserted wavelengths, and a postamplifier that amplifies the output of the wavelength multiplexing unit And a second interleaver for synthesizing the outputs of the first and second system post-amplifiers, and using the ASE light transmitted from the post-amplifier of the preceding OADM node, When the preamplifier of the OADM node is set to have a predetermined gain, the preceding stage corresponds to the difference between the level at the input of the first interleaver of the subsequent OADM node and the predetermined gain of the preamplifier. The level of the ASE light transmitted from the postamplifier of the OADM node is set large.

  In a WDM transmission system that solves the above-described problems of the present invention, as a second aspect, in the first aspect, the size for setting a large level of the ASE light transmitted from the post-amplifier of the preceding OADM node is about The size is 3 dB.

  In a WDM transmission system that solves the above-described problems of the present invention, as a third aspect, in the wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line and an optical signal that is wavelength division multiplexed is transmitted. Each of the OADM nodes includes a first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength, and an optical signal of an odd wavelength and an even wavelength group that is divided and output by the interleaver. Each of the first and second systems is wavelength-multiplexed of the divided odd wavelength group or even wavelength group with a predetermined gain. A preamplifier for amplifying an optical signal, a wavelength multiplexing / demultiplexing unit for wavelength-separating the wavelength-multiplexed optical signal amplified by the preamplifier, and a wavelength multiplexing / separating unit. An add / drop unit that transmits or adds a predetermined wavelength among a plurality of wavelengths, a wavelength multiplexing unit that wavelength-multiplexes the transmitted and inserted wavelengths, and a postamplifier that amplifies the output of the wavelength multiplexing unit; , A second interleaver for synthesizing the outputs of the first and second system post-amplifiers, and optical switches at the input and output ports of the first and second interleavers. , Using the ASE light transmitted from the post-amplifier of the preceding OADM node, when the preamplifier of the subsequent OADM node is set to have a predetermined gain, the inputs of the first and second interleavers And the optical switch included in the output port is controlled to be switched so as to bypass and connect the first and second interleavers from the input port to the output port. And features.

  In a WDM transmission system that solves the above-described problems of the present invention, as a fourth aspect, in the third aspect, the inputs of the first and second interleavers that bypass the first and second interleavers are used. And an attenuator between the output ports.

  The WDM transmission system that solves the above-mentioned problems of the present invention is characterized in that, as a fifth aspect, in the fourth aspect, the level attenuation by the attenuator is set to about 3 dB.

  A WDM transmission system that solves the above-described problems of the present invention is a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line to transmit wavelength division multiplexed optical signals. Each of the OADM nodes includes a first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength, and an optical signal of an odd wavelength and an even wavelength group that is divided and output by the interleaver. Each of the first and second systems is wavelength-multiplexed of the divided odd wavelength group or even wavelength group with a predetermined gain. A preamplifier for amplifying an optical signal, a wavelength multiplexing / demultiplexing unit for wavelength-separating the wavelength-multiplexed optical signal amplified by the preamplifier, and a wavelength multiplexing / separating unit. An add / drop unit that transmits or adds a predetermined wavelength among a plurality of wavelengths, a wavelength multiplexing unit that wavelength-multiplexes the transmitted and inserted wavelengths, and a postamplifier that amplifies the output of the wavelength multiplexing unit; , A second interleaver for synthesizing the outputs of the first and second system post amplifiers, a variable attenuator on the input side of the first interleaver, and an OADM node in the previous stage The amount of attenuation of the variable attenuator is set to zero when the preamplifier of the subsequent OADM node is set to have a predetermined gain by using ASE light transmitted from the post-amplifier. .

  In a WDM transmission system that solves the above-described problems of the present invention, as a seventh aspect, in the sixth aspect, the attenuation of the variable attenuator is reduced by about 3 dB during normal operation after the start-up. It is characterized by.

  The WDM transmission system that solves the above-described problems of the present invention provides, as an eighth aspect, a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line to transmit wavelength division multiplexed optical signals. Each of the plurality of OADM nodes includes a preamplifier for amplifying an optical signal wavelength-multiplexed with a predetermined gain, a wavelength multiplexing / separation unit for wavelength-separating the wavelength-multiplexed optical signal amplified by the preamplifier, and a wavelength multiplexing / separation unit. Of the plurality of separated wavelengths, a branching / inserting unit that transmits or branches a predetermined wavelength, a wavelength multiplexing unit that wavelength-multiplexes the transmitted and inserted wavelengths, and amplifies the output of the wavelength multiplexing unit It has a post-amplifier, further has a VIPA on the input side of the OADM node, and uses ASE light transmitted from the post-amplifier of the preceding OADM node. , Corresponding to the difference between the output level of the VIPA provided on the input side of the subsequent OADM node and the predetermined gain of the preamplifier when the preamplifier of the subsequent OADM node is set to have a predetermined gain. The ASE light level transmitted from the post-amplifier of the preceding OADM node is set large.

  The features of the present invention will become more apparent from the embodiments described below with reference to the drawings.

  According to the present invention, it is possible to use an interleaver and VIPA without making it difficult to set the gain of the preamplifier by ASE light. Therefore, in the wavelength division multiplexing transmission system, it is necessary to arrange the wavelengths with high density in the same band. It is possible to respond.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the present invention, the embodiments shown in the drawings are for understanding the present invention, and the technical scope of the present invention is not limited thereto.

  FIG. 2 is a configuration diagram of an optical transmission system using an interleaver to which the present invention is applied. When compared with FIG. 1, the relay node 110 has no direct relationship in the present invention, and is not shown for the sake of simplicity.

  Each of the OADM nodes 100 and 120 is configured in two systems as an embodiment, and similarly to the configuration shown in FIG. 1, a preamplifier unit 1a (1b) is provided on the input side, and a postamplifier unit 5a (5b) is provided on the output side. It has been. Further, the wavelength division multiplexed optical signal is separated for each wavelength by the demultiplexing circuit 2a (2b). Subsequently, transmission, branching, or insertion is performed for each wavelength by the inserting / branching circuit 3a (3b). Further, the wavelength transmitted through the OADM node 100 and the wavelength inserted by the inserting / branching circuit 3 are multiplexed by the multiplexing circuit 4a (4b).

  Further, the first interleaver 6 is disposed in the front stage of the preamplifier units 1a and 1b, and the second interleaver 7 is disposed in the rear stage of the post amplifier units 5a and 5b.

  3 and 4 are diagrams for further explaining the operation of the interleavers 6 and 7.

  FIG. 3 is a diagram for explaining the operation of the first interleaver 6. The wavelength-multiplexed optical signal is output to an odd wavelength (a wavelength corresponding to an odd channel) and an even wavelength (a wavelength corresponding to an even wavelength). Outputs demultiplexed waves. In the spectrum A of the wavelength-multiplexed optical signal input to the input terminal (a) of the interleaver 6, a plurality of channel (wavelength) signals of channels Ch1 to Chn are superimposed on the ASE noise light level AL.

  The interleaver 6 has a transmission characteristic D to the odd wavelength output port (b) and a transmission characteristic E to the even wavelength output port (c). Therefore, the optical signal output from the output port (b) has an odd wavelength output spectrum B. On the other hand, the optical signal output from the output port (c) has an even wavelength output spectrum C.

  FIG. 4 is a diagram for explaining the operation of the second interleaver 7, which multiplexes and outputs odd-numbered and even-numbered wavelengths. The odd wavelength and even wavelength optical signals respectively input to the input terminals (b) and (c) of the interleaver 7 have wavelength spectra B and C, respectively. In the wavelength spectra B and C, odd and even wavelength signals are superimposed corresponding to the ASE noise light level AL, respectively.

  The interleaver 7 has reversible characteristics with the interleaver 6 and has an odd-port transmission characteristic D for an odd-wavelength optical signal input from the port (b), and an even-number input from the port (c). The optical signal having the wavelength has an even-numbered port transmission characteristic E, and the output from the wavelength multiplexing output port (a) has an output spectrum A in which the wavelength multiplexing of the odd number and the even number is performed.

  In the output spectrum A, multiple channel (wavelength) signals of channels Ch1 to Chn are superimposed on the ASE noise light level AL.

  FIG. 5 is a diagram showing a change in the power level of the ASE light. In FIG. 5, when the power level of the ASE light at the output of the postamplifier unit 5a (5b) of the OADM node 100 is “A”, the ASE light output of the interleaver 7 becomes “B”. That is, the output attenuation increases alternately between odd and even, so the output spectrum of the ASE light is as shown by “B”.

  At this time, the total level (required level Lr) of the ASE light is substantially half the level (3 dB lower) than the level “A” on the input side of the interleaver 7 to be the actual ASE level La.

  Therefore, the input level of the preamplifier unit 1a (1b) of the ASE light transmitted through the optical fiber transmission line 130 is in a “C” state due to the transmission line loss of the optical fiber transmission line 130. That is, the actual ASE light level La is smaller than the ASE level Lr required for the input of the preamplifier unit 1a (1b).

  Thus, there is a difference between the required ASE light level Lr and the ASE light level after passing through the interleaver.

  Therefore, as shown in FIG. 5, “D”, there is a difference between the gain Gr originally required for the preamplifier unit 1a (1b) and the gain Gs necessary to be actually set.

  Actually, in the conventional wavelength transmission system, as shown in the previous patent application (Japanese Patent Application No. 16-007857), in the start-up method using ASE light, the post-amplifier unit 5a is used at the time of start-up. , (5b), ASE light equivalent to one wave of signal light is output. On the other hand, the preamplifier unit 1a (1b) uses the ASE light to set the gain. At this time, in the system using the interleaver, since the adjacent wavelength of each wavelength is removed in the even-numbered interleaver, the ASE light level is approximately halved (the level is reduced by about 3 dB). For this reason, there is a problem that the preamplifier unit 1a (1b) at the next stage cannot be set to a required gain.

  Therefore, the present invention solves this problem.

  FIGS. 6 and 7 are diagrams for explaining switching of the post-amplifier unit 5 and the pre-amplifier unit 1 during start-up (when the pre-amplifier gain is set) and during operation, respectively.

  FIG. 6 is a diagram showing a schematic configuration of the post-amplifier unit 5 of the upstream OADM node 100. As shown in FIG. An optical switch 50, a post-amplifier module 51, and an OSC coupler 52 are connected in series. Further, the amplifier control unit 53 controls switching between the optical switch 50 and the post-amplifier module 51.

  The amplifier controller 53 notifies the device controller (not shown) of the state of the optical switch read from the optical switch 50 and the state of the post-amplifier module 51 (step S1). Based on the determination in the apparatus control unit from the notification state, a switch control command for switching between the ASE startup mode and the normal operation mode is sent to the amplifier control unit 53.

  When the ASE startup mode command is sent, the amplifier control unit 53 instructs the optical switch 50 to switch to the side where the input to the post-amplifier module 51 is cut off (step S2). Further, the ASE startup mode is set for the post-amplifier module 51 (step S3).

  On the other hand, an OSC signal that is a supervisory control signal is inserted by the coupler 52 and sent to the OADM node 120 at the subsequent stage.

  FIG. 7 shows the configuration of the preamplifier unit 1. The OSC signal transmitted from the OADM node 100 is separated by the OSC coupler 10 and is determined to be in the ASE start-up mode by a device control unit (not shown).

  As a result, the ASE startup mode is notified from the apparatus control unit to the AMP control unit 11 (step S10). Next, the AMP control unit 11 sets the ASE startup mode for the preamplifier module 12 (step S11). The gain of the preamplifier module 12 is set so as to become a predetermined level later according to the reference according to each embodiment according to the level of the received ASE light, and the start-up setting process is completed.

  In FIG. 7, when a dispersion compensating fiber (DCF) is used, it is connected to a dispersion compensating fiber (DCF) (not shown) through terminals (DCFOUT, DCFIN), and a predetermined reference gain setting is performed.

  FIG. 8 is a diagram for explaining the change of the ASE light in the first embodiment according to the present invention, corresponding to FIG.

  In FIG. 8, FIG. 8A is a diagram showing a change in the level of the ASE light corresponding to FIG. 5, and FIG. 8B is a diagram showing a change in the level of the ASE light according to the present invention.

  8A and 8B, the level of the ASE light output from the interleaver 7 of the OADM node 100 in FIG. 2 is indicated by “B”.

  In comparison between “B” in FIG. 8A and “B” in FIG. 8B according to the present invention, the feature is that in FIG. 8B, the gain of the post-amplifier unit 5a (5b) is increased by 3 dB, and the level of the ASE light is 3 dB. It is rising. As a result, the level on the input side of the interleaver 6 of the OADM node 120 on the receiving side is as shown in “C” in FIG. 8B. That is, as shown in FIG. 8B, “C”, the signal level transmitted through the transmission line 130 is increased by 3 dB on the transmission side, and therefore the received level is also increased by Lg.

  Therefore, according to the present invention, the ASE level of the output divided into odd and even numbers by the interleaver 6 of the OADM node 120 becomes closer to the required ASE level Lr than the actual ASE level La in FIG. 8A. Therefore, the gain required for the preamplifier unit 1a (1b) can be the same as the preamplifier gain setting method for a transmission system without a conventional interleaver.

  FIG. 9 is a configuration diagram of an optical transmission system using an interleaver according to the second embodiment of the present invention. The feature of this embodiment is that the optical switches 60-62 and 70-72 are provided at the input and output ports of the interleavers 6 and 7, respectively, so that the interleavers 6 and 7 can be bypassed when the system is started up. It is. Further, attenuators 63 and 64 and 73 and 74 are provided in a circuit that bypasses the interleavers 6 and 7. The attenuators 63 and 64 are for making the passage loss of the output side optical switches 61 and 62 of the preamplifier unit 1a (1b) from the transmission line side optical switch 60 the same as the passage loss of the interleaver 6. Similarly, the attenuators 73 and 74 are for making the passage loss from the input of the post-amplifier unit 5a (5b) side optical switches 71 and 72 to the transmission path 103 side optical switch output the same as the passage loss of the interleaver 7. is there.

  At startup, that is, when the gain of the preamplifier unit 1a (1b) is set, the optical switches 60 to 62 and 70 to 72 are switched to control the interleavers 6 and 7 so that the optical signals are bypassed. A halving (about 3 dB reduction) is avoided.

  That is, control is performed so that the optical switch 71-70 or the optical switch 72-70 passes through the odd-numbered and even-numbered channels, and at the same time, the optical switch 60-61 or the optical switch 60-62 is controlled.

  FIG. 10 is a configuration diagram of an optical transmission system using an interleaver according to the third embodiment of the present invention. FIG. 11 is a diagram showing a change in the power level of the ASE light corresponding to the embodiment shown in FIG.

  The embodiment shown in FIG. 10 inputs to the preamplifier unit 1a (1b) at the time of start-up operation on the premise of the fact that the ASE at start-up is reduced by about 3 dB due to the presence of the interleavers 6 and 7. The optical signal level is reduced by about 3 dB.

  That is, the variable optical attenuator 8 is provided on the front side of the interleaver 6 on the input side of the preamplifier unit 1a (1b). As shown in FIG. 11, the attenuation amount of the attenuator 8 is reduced by 3 dB at the time of start-up by ASE light, and the level is increased by 3 dB with respect to the normal operation.

  In other words, the effect of setting the gain of the preamplifier in a state where the ASE light is halved (about 3 dB reduction) by inserting the interleavers 6 and 7 equivalently can be avoided.

  Here, the above embodiment has been described for a wavelength division multiplexing communication system that uses an interleaver exclusively. However, as described above, the present invention can also be applied to a system using a VIPA as a chromatic dispersion compensator whose output is halved at a predetermined frequency period like an interleaver.

  FIG. 12 is an example of a wavelength division multiplexing communication system in which a VIPA 132 is placed on the input side of the OADM node 120. The output of the VIPA 132 has a characteristic of periodically halving as described above.

  FIG. 13 is a diagram showing signal levels at various parts of a transmission line system having the VIPA 132 in the middle of the transmission line. Further, FIG. 13A shows the signal level of each part when the present invention is not applied, and FIG. 13B shows the signal level of each part when the present invention is applied.

  In FIG. 13A and FIG. 13B, “C” is the signal level on the output side of VIPA 132, and the level is periodically halved, so the actual ASE level is halved relative to the required ASE level. Accordingly, it is necessary to set the gain of the preamplifier 1 not to the required gain Gr but to a gain of Gs larger than that.

  On the other hand, as shown in FIG. 13B, “A”, according to the present invention, the gain of the postamplifier unit 5 is increased by 3 dB and the ASE light level is increased by 3 dB on the transmission side. As a result, the level on the input side of the VIPA 132 of the OADM node 120 on the receiving side becomes as shown in “B” of FIG. 13B.

  That is, as shown in FIG. 13B, “B”, since the signal level transmitted through the transmission line 130 is increased by 3 dB on the transmission side, the level on the input side of the VIPA 132 is also increased by Lg. Yes.

  Therefore, according to the present invention, the output ASE level periodically halved by the VIPA 132 on the input side of the OADM node 120 is closer to the required ASE level Lr than the actual ASE level La in FIG. 13A. Therefore, the gain required for the preamplifier unit 1a (1b) can be the same as that of the preamplifier gain setting method for a transmission system without a conventional VIPA.

(Appendix 1)
In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line to transmit a wavelength division multiplexed optical signal,
Each of the plurality of OADM nodes is
A first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength;
A first system and a second system provided corresponding to optical signals of an odd wavelength group and an even wavelength group divided and output by the interleaver;
Each of the first and second systems is
A preamplifier for amplifying the wavelength-multiplexed optical signal of the divided odd wavelength group or even wavelength group with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A post-amplifier for amplifying the output of the wavelength multiplexing unit;
And a second interleaver for synthesizing the outputs of the first and second system post-amplifiers,
The first interleaver of the subsequent OADM node is input at the time of start-up that sets the preamplifier of the subsequent OADM node to have a predetermined gain using the ASE light transmitted from the postamplifier of the upstream OADM node. A wavelength division multiplexing communication system, wherein the level of the ASE light transmitted from the post-amplifier of the preceding OADM node is set to be large corresponding to the difference between the level of the preamplifier and the predetermined gain of the preamplifier.

(Appendix 2) In Appendix 1,
2. A wavelength division multiplexing communication system characterized in that a magnitude for setting a large level of ASE light transmitted from the post-amplifier of the preceding OADM node is about 3 dB.

(Appendix 3)
In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line to transmit a wavelength division multiplexed optical signal,
Each of the plurality of OADM nodes is
A first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength;
A first system and a second system provided corresponding to optical signals of an odd wavelength group and an even wavelength group divided and output by the interleaver;
Each of the first and second systems is
A preamplifier for amplifying the wavelength-multiplexed optical signal of the divided odd wavelength group or even wavelength group with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A postamplifier for amplifying the output of the wavelength multiplexing unit;
A second interleaver for synthesizing the outputs of the first and second system post-amplifiers;
And an optical switch at the input and output ports of the first and second interleavers,
At the start-up of setting the preamplifier of the subsequent OADM node to have a predetermined gain using the ASE light transmitted from the postamplifier of the upstream OADM node, the inputs of the first and second interleavers and An optical switch provided in an output port is controlled to be switched so as to bypass and connect the first and second interleavers from the input port to the output port.

(Appendix 4) In Appendix 3,
A wavelength division multiplex communication system comprising an attenuator between input and output ports of the first and second interleavers that bypass the first and second interleavers.

(Appendix 5) In Appendix 4,
A wavelength division multiplexing communication system, wherein the level attenuation by the attenuator is set to about 3 dB.

(Appendix 6)
In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line to transmit a wavelength division multiplexed optical signal,
Each of the plurality of OADM nodes is
A first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength;
A first system and a second system provided corresponding to optical signals of an odd wavelength group and an even wavelength group divided and output by the interleaver;
Each of the first and second systems is
A preamplifier for amplifying the wavelength-multiplexed optical signal of the divided odd wavelength group or even wavelength group with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A postamplifier for amplifying the output of the wavelength multiplexing unit;
A second interleaver for synthesizing the outputs of the first and second system post-amplifiers; and a variable attenuator on the input side of the first interleaver;
Using the ASE light transmitted from the post-amplifier of the upstream OADM node, the attenuation amount of the variable attenuator is set to zero at the start-up when the pre-amplifier of the downstream OADM node is set to have a predetermined gain. A wavelength division multiplexing communication system.

(Appendix 7) In Appendix 6,
A wavelength division multiplexing communication system, wherein the attenuation amount of the variable attenuator is reduced by about 3 dB during normal operation after the startup.

(Appendix 8)
In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line to transmit a wavelength division multiplexed optical signal,
Each of the plurality of OADM nodes is
A preamplifier for amplifying an optical signal wavelength-multiplexed with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A post-amplifier for amplifying the output of the wavelength multiplexing unit;
Furthermore, a VIPA is provided on the input side of the OADM node,
Using the ASE light transmitted from the post-amplifier of the front-stage OADM node, the VIPA provided on the input side of the rear-stage OADM node is set up so that the pre-amplifier of the rear-stage OADM node is set to have a predetermined gain. A wavelength division multiplexing communication system, wherein a level of ASE light transmitted from a post-amplifier of the preceding OADM node is set to be large corresponding to a difference between an output level and a predetermined gain of the preamplifier.

(Appendix 9) In Appendix 8,
2. A wavelength division multiplexing communication system characterized in that a magnitude for setting a large level of ASE light transmitted from the post-amplifier of the preceding OADM node is about 3 dB.

  As described above with reference to the drawings, according to the present invention, it is possible to avoid the influence on the gain setting of the preamplifier upon start-up due to the insertion of an interleaver or VIPA. Therefore, it is possible to use an interleaver and VIPA, meet the demand for arranging wavelengths with high density in the same band, and this is very advantageous for the industry.

It is a figure which shows the conceptual structure of a WDM transmission system. It is a block diagram of the optical transmission system using the interleaver made into the object of this invention. It is a figure explaining operation | movement of the 1st interleaver. It is a figure explaining operation | movement of the 2nd interleaver. It is a figure which shows the change of the electric power level of ASE light. It is a figure explaining the switching at the time of starting (at the time of preamplifier gain setting) with respect to the post-amplifier unit 5 and operation. It is a figure explaining the change at the time of starting (at the time of preamplifier gain setting) with respect to the preamplifier unit 1, and an operation. It is a figure explaining the change of the ASE light in 1st Example according to this invention corresponding to FIG. It is a block diagram of the optical transmission system which uses the interleaver which shows the 2nd Example of this invention. It is a block diagram of the optical transmission system which uses the interleaver which shows the 3rd Example of this invention. It is a figure which shows the change of the electric power level of the ASE light corresponding to the Example shown in FIG. It is a figure which shows the example of the transmission line system by which VIPA was set | placed on the input side of the OADM node. It is a figure which shows the signal level of each part of the wavelength division multiplexing communication system which has VIPA in the middle of a transmission line.

Explanation of symbols

100, 120 OADM node 110 Relay node 1, 1a, 1b Preamplifier unit 2 Demultiplexing circuit 3 Insertion / branching circuit 4 Multiplexing circuit 5 Post amplifier unit 130, 131 Optical fiber transmission line

Claims (5)

In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line and a wavelength division multiplexed optical signal is transmitted,
Each of the plurality of OADM nodes is
A first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength;
A first system and a second system provided corresponding to an optical signal of an odd wavelength group and an even wavelength group divided and output by the interleaver;
Each of the first and second systems is
A preamplifier for amplifying a wavelength-multiplexed optical signal of the divided odd wavelength group or even wavelength group with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A post-amplifier for amplifying the output of the wavelength multiplexing unit ;
A second interleaver that synthesizes the outputs of the first and second system post-amplifiers ;
When setting the preamplifier of the subsequent OADM node to have a predetermined gain using the ASE light transmitted from the postamplifier of the upstream OADM node, the preamplifier is required to obtain a predetermined ASE optical level. wherein a predetermined gain, corresponding to the difference between the gain of the preamplifier required in response to the level of the ASE light at the input of the first interleaver of the subsequent OADM node, the preceding OADM node post that A control unit for setting a large level of ASE light transmitted from the amplifier ,
A wavelength division multiplex communication system comprising: In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line and a wavelength division multiplexed optical signal is transmitted,
Each of the plurality of OADM nodes is
A first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength;
A first system and a second system provided corresponding to an optical signal of an odd wavelength group and an even wavelength group divided and output by the interleaver;
Each of the first and second systems is
A preamplifier for amplifying a wavelength-multiplexed optical signal of the divided odd wavelength group or even wavelength group with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A post-amplifier for amplifying the output of the wavelength multiplexing unit;
A second interleaver for synthesizing the outputs of the first and second system post-amplifiers ;
Optical switches at input and output ports of the first and second interleavers ;
Furthermore, optical switches provided corresponding to the first and second systems at the input and output ports of the first and second interleavers ,
When the ASE light transmitted from the post-amplifier of the preceding OADM node is used to set the preamplifier of the subsequent OADM node to have a predetermined gain, the first and second interleavers are set by the optical switch. A controller that switches to bypass the optical path from the input port to the output port,
A wavelength division multiplex communication system comprising: In claim 2,
A wavelength division multiplex communication system comprising an attenuator between input and output ports of the first and second interleavers that bypass the first and second interleavers. In claim 3,
A wavelength division multiplexing communication system, wherein the level attenuation by the attenuator is set to about 3 dB. In a wavelength division multiplexing communication system in which a plurality of OADM nodes are connected by an optical fiber transmission line and a wavelength division multiplexed optical signal is transmitted,
Each of the plurality of OADM nodes is
A first interleaver that divides an optical signal in which a plurality of wavelengths are multiplexed into an odd wavelength and an even wavelength;
A first system and a second system provided corresponding to an optical signal of an odd wavelength group and an even wavelength group divided and output by the interleaver;
Each of the first and second systems is
A preamplifier for amplifying a wavelength-multiplexed optical signal of the divided odd wavelength group or even wavelength group with a predetermined gain;
A wavelength demultiplexing unit for wavelength demultiplexing the wavelength-multiplexed optical signal amplified by the preamplifier;
A branching / inserting unit for transmitting or branching a predetermined wavelength among a plurality of wavelengths separated by the wavelength demultiplexing unit;
A wavelength multiplexing unit for wavelength-multiplexing the transmitted and inserted wavelengths;
A post-amplifier for amplifying the output of the wavelength multiplexing unit;
A second interleaver for synthesizing the outputs of the first and second system post-amplifiers ;
Have a variable attenuator on the input side of said first interleaver, further,
When setting the preamplifier of the subsequent OADM node to have a predetermined gain using the ASE light transmitted from the postamplifier of the preceding OADM node, the attenuation of the variable attenuator is set to zero, A control unit for effectively setting the amount of attenuation of the variable attenuator during operation of
A wavelength division multiplex communication system comprising:

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