WO2006085375A1

WO2006085375A1 - Wavelength division multiplex apparatus

Info

Publication number: WO2006085375A1
Application number: PCT/JP2005/002014
Authority: WO
Inventors: Tomoyuki Suzuki; Mitsuaki Haneishi; Hiroaki Nakazato; Takashi Sakata
Original assignee: Fujitsu Limited
Priority date: 2005-02-10
Filing date: 2005-02-10
Publication date: 2006-08-17

Abstract

In a wavelength division multiplex apparatus having a transmitting station node, a relaying station node and a terminating station node, a bypass for passing a wavelength multiplexed signal without separating and multiplexing is provided to the relaying station node having an OADM part (demultiplexing part). In this way, noise light components can be prevented from being apparently eliminated, and a single OSNR measurement in the single terminating station node can provide an accurate measurement of a total end-to-end OSNR. Moreover, the number of operation processes can be significantly reduced.

Description

Specification

Wavelength division multiplexer

Technical field

TECHNICAL FIELD [0001] The present invention relates to a wavelength division multiplexing (WDM) apparatus, and in particular, an OADM (Optical Add Drop Module) unit (demultiplexing unit) capable of adding, dropping, and passing a wavelength to a relay station. In a WDM device equipped with

It relates to WDM equipment that can measure OSNR (Optical Noise Signal Ratio) from to End.

Background art

[0002] In recent WDM equipment (wavelength division multiplexing equipment), the topology configuration is conventional.

From the point-to-point configuration form, OADM (Optical

The introduction of WDM equipment with the Add Drop Module) section (demultiplexing section) is increasing.

[0003] One of the important conditions for constructing a system using WDM equipment is the signal Z-noise ratio (OSNR ((Optical Noise Signal Ratio)) of optical signals received at the terminal station.

FIG. 1 is a diagram illustrating OSNR. OSNR is a value representing the difference between signal light and noise light in dB. The smaller this difference (the smaller the difference between signal light and noise light), the greater the noise in the signal received at the terminal station. It becomes difficult to receive. The OSNR limit value is the maximum OSNR that can be received by the receiving unit of the terminal station. Also, the noise light includes broadband noise called ASE (Amplified Spontaneous Emission) due to optical amplification relay.

FIG. 2 is a diagram for explaining OSNR in a conventional WDM apparatus having a point-to-point configuration. In FIG. 2, the WDM equipment is configured to include a starting station node (Node) A, a relay station node B, and a terminating station node C. A plurality of relay station nodes B may be provided on the optical signal transmission path. The starting station node A has a multiplexing unit (Multiplexer) ll that multiplexes and transmits optical signals of a plurality of wavelengths, and a transmission amplifier unit 12 that amplifies the transmitted optical signal. Also relay The station node B has an amplifier section (In

Line Amp) 21 and no OADM section. In addition, the terminal station node C includes a reception amplifier unit 31 that amplifies the received optical signal and a demultiplexer 32 that demultiplexes the multiplexed optical signal.

[0006] In an interval in which an optical signal is transmitted from the multiplexing unit 11 of the starting station node A to the separating unit 32 of the terminal station node C, a noise component is superimposed on the signal light every time the optical signal passes through the amplifier unit. Every time it passes through the amplifier, the OSNR gets smaller. The OSNR of the optical signal passing through each amplifier section can be confirmed by connecting an OSNR confirmation measuring instrument (spectrum analyzer) 40 to the output terminal of each amplifier section. FIG. 2 schematically shows a state in which the spectrum analyzer 40 is connected to the reception amplifier unit 31 of the terminal station node C.

[0007] Then, in the OSNR confirmation work that is indispensable for ensuring the stable operation of the WDM equipment, the starting station A power measured by the receiving amplifier unit 31 of the terminal station node C is also increased to the terminal station node C. Total OSNR force It is necessary to design the WDM equipment so that it exceeds the OSNR limit value of the receiver that receives the optical signal of each wavelength.

[0008] In Patent Document 1 below, in the demultiplexer and multiplexer of the WDM optical signal, only the pass wavelength band is made equal, and the free spectral ranges representing the periodicity of the pass characteristics are made different from each other. Thus, the invention for preventing the accumulation of unnecessary ASE noise light is disclosed.

Patent Document 1: Japanese Patent Laid-Open No. 2003-69496

Disclosure of the invention

Problems to be solved by the invention

FIG. 3 is a diagram for explaining the OSNR of a WDM apparatus having an OADM unit. In comparison with FIG. 2, the central station node B includes an OADM unit 22 and amplifier units 21 and 23 on the upstream side and the downstream side, respectively. The OADM unit 22 includes a separation unit 221 that separates the multiplexed optical signal for each wavelength and a multiplexing unit 222 that multiplexes again. The optical signal can pass between the separation unit 221 and the multiplexing unit 222. When an optical signal is transmitted in the direction opposite to the illustrated direction, the demultiplexing unit functions as a multiplexing unit, and the multiplexing unit functions as a demultiplexing unit. You will be jealous.

[0010] In such a separation unit 221 of the OADM unit 22, the optical signal passing therethrough is separated for each wavelength, so that a noise light component (ASE light) important for measuring the OSNR is cut by the filter. As a result, it becomes impossible to distinguish between the signal light component and the noise light component, and the noise light becomes less powerful. Whereas the signal light is a signal having a peak at a specific wavelength, the noise light (ASE light) is a signal that spreads in a wavelength band having a certain width. As a result, the noise light component is also divided for each specific wavelength together with the signal light component. As a result, the spread of the wavelength band of the noise light component cannot be recognized, and the signal light and the noise light cannot be substantially distinguished.

[0011] Thus, when the optical signal passes through the OADM unit 22 of the relay station node B, the apparent noise light component disappears once, and then the state where no noise light component is included. Since the noise light component is superimposed every time the signal passes through, a spectrum analyzer is connected to the receiving amplifier 31 of the terminal station node C, and the total OSNR up to the starting station node A force and the terminal station node C is calculated. When measuring, OSNR larger than the actual value (with less noise) is measured. That is, there is a problem that the OSNR for the optical signal path passing through the relay node B having the OADM unit 22 cannot be measured. Currently, when measuring the end-to-end OSNR from the start station node A to the end station node C on the path where the relay station node B having the OADM section is installed on the way, the optical signal path is changed to the OADM section. Divide immediately before 22 and measure OSNR for each of multiple spans.

The total OSNR is obtained by summing the OSNR for each span according to the to-end route. However, measuring OSNR for each span requires a lot of time and labor. In addition, since measurement is performed multiple times, measurement errors of the spectrum analyzer that measures OSNR are also superimposed, leading to poor measurement accuracy.

In view of the above problems, an object of the present invention is to measure an OSNR (Optical Noise Signal Ratio) end to end in a WDM apparatus (wavelength division multiplexing apparatus) in which a relay station node has an OADM unit. It is to provide a wavelength division multiplexing apparatus.

Means for solving the problem [0013] A first wavelength division multiplexing apparatus of the present invention for realizing the above object generates a first wavelength multiplexed signal by multiplexing a plurality of optical signals having different wavelengths, and generates the first wavelength multiplexed signal. The first wavelength-multiplexed signal from the first node and the first wavelength-multiplexed signal received from the first node, the first wavelength-multiplexed signal is divided into optical signals for each wavelength, and further divided A plurality of optical signals having different wavelengths including at least a part of the optical signal are multiplexed to generate a second wavelength multiplexed signal, and the first path for transmitting the second wavelength multiplexed signal is received. A second node having a second path for transmitting the first wavelength multiplexed signal without being divided and multiplexed; and the first wavelength multiplexed signal from the second node or the second And a receiving node for receiving the wavelength division multiplexed signal.

[0014] A second wavelength division multiplexing apparatus according to the present invention is the first wavelength division multiplexing apparatus, wherein the second node transmits the first wavelength division multiplexed signal for each wavelength on the first path. And a multiplexing unit that multiplexes a plurality of optical signals having different wavelengths including at least a part of the divided optical signal to generate a second wavelength multiplexed signal. The second path is branched from the first path on the upstream side of the separation unit and merges with the first path on the downstream side of the multiplexing unit.

[0015] A third wavelength division multiplexing apparatus according to the present invention is the first wavelength division multiplexing apparatus, wherein the second node is a path of the first wavelength division multiplexed signal in the OSNR measurement mode. The first path is selected in the normal operation mode.

[0016] A fourth wavelength division multiplexing apparatus according to the present invention is the third wavelength division multiplexing apparatus, wherein the second node includes a plurality of switches for switching the first path or the second path. It is characterized by providing.

[0017] A fifth wavelength division multiplexing apparatus of the present invention includes a first node that selects and transmits either a first wavelength multiplexed signal or a dummy optical signal obtained by multiplexing a plurality of optical signals having different wavelengths. The first wavelength multiplexed signal is divided into optical signals for each wavelength, and a plurality of optical signals having different wavelengths including at least a part of the divided optical signals are further multiplexed to generate a second wavelength multiplexed signal. The second path for transmitting the second wavelength multiplexed signal and the second node for transmitting the dummy optical signal without being divided and multiplexed can be selected. And a receiving node that receives the second wavelength multiplexed signal or dummy optical signal from the second node.

[0018] In a sixth wavelength division multiplexing apparatus of the present invention, in the fifth wavelength division multiplexing apparatus, the first node selects and transmits the dummy optical signal in an OSNR measurement mode. In the operation mode, the first wavelength division multiplexed signal is selected and transmitted, and the second node selects the second path in the OSNR measurement mode, and in the normal operation mode, the first node is selected. The path is selected.

In the seventh wavelength division multiplexing apparatus of the present invention, in the sixth wavelength division multiplexing apparatus, the first node selects either the first wavelength division multiplexed signal or the dummy optical signal. The second node has a plurality of second switches for switching the first path or the second path.

[0020] An eighth wavelength division multiplexing apparatus of the present invention is the seventh wavelength division multiplexing apparatus, further comprising a control device for remotely operating the first switch and the second switch. It is characterized by.

The invention's effect

[0021] According to the wavelength division multiplexing apparatus of the present invention, by providing a bypass (second node) that relays the wavelength multiplexed signal without separating and multiplexing the wavelength multiplexed signal, the node that relays the wavelength multiplexed signal is provided. Therefore, it is possible to prevent the noise light component from disappearing by 4 points and to measure the OSNR at the end-to-end with a single OSNR measurement at the terminal station (third node) at one power point. In addition, the number of work steps can be greatly reduced.

[0022] Since end-to-end OSNR measurement is possible at a single power point, the OSNR measured for each span is added to the end.

Compared with the conventional method for determining the to-end OSNR, it is possible to significantly improve the OSNR measurement accuracy.

Brief Description of Drawings

[0023] FIG. 1 is a diagram for explaining OSNR.

FIG. 2 is a diagram for explaining OSNR in a conventional WDM apparatus having a point-to-point configuration.

FIG. 3 is a diagram for explaining the OSNR of a WDM apparatus having an OADM unit. FIG. 4 is a diagram showing a first configuration of a WDM apparatus in an embodiment of the present invention.

FIG. 5 is a diagram showing another configuration example of the starting point station node A.

FIG. 6 is a diagram showing a configuration example of an end station node C.

FIG. 7 is a diagram showing a second configuration of the WDM apparatus in the embodiment of the present invention.

FIG. 8 is a diagram showing a system configuration for remotely controlling each switch of a node.

FIG. 9 is a diagram showing an example of a switch setting table held by the control terminal 80.

FIG. 10 is a diagram showing a flowchart for controlling the switch operation of each node. Explanation of symbols

[0024] A, B, C: nodes

SW1, SW2, SW3: Switch

22: OADM Department

221: Separation part

222: Multiple part

25: Bypass

80: Control terminal

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment does not limit the technical scope of the present invention.

FIG. 4 is a diagram showing a first configuration of the WDM apparatus in the embodiment of the present invention. In the first configuration of the WDM apparatus, in comparison with the configuration of FIG. 3 above, the upstream side of the separation unit 221 of the relay station node B, more specifically, between the (reception) amplifier unit 23 and the separation unit 221 A switch SW3 for switching the signal path is provided, and further, a switch SW1 for switching the optical signal path is provided downstream of the multiplexing unit 222, more specifically, between the multiplexing unit 222 and the (transmission) amplifier unit 24. A normal path through which the optical signal passes through the OADM unit 22 and a bypass 25 through which the optical signal does not pass through the OADM unit 22 are provided between the switch SW1 and the switch SW3.

[0027] Switches SW1 and SW3 switch the optical signal path between the normal operation mode and the OSNR measurement mode. That is, in the normal operation mode, the switch SW3 selects a normal path for introducing the optical signal of the receiving amplifier unit 23 to the OADM unit 22, and the switch SW1 is also connected to the OA. Selects the normal nose to which the optical signal from DM section 22 is input. On the other hand, in the OSNR measurement mode, in order to prevent the optical signal from passing through the OADM unit 22, the switch SW3 selects the bypass 25 and branches the optical signal from the reception amplifier unit 23 to the bypass 25. The switch SW1 is also switched to input the optical signal from Neupath 25.

[0028] In this way, the optical signal does not pass through the OADM unit 22! By providing a bypass and transmitting the binos in the OSNR measurement mode, the optical signal is transmitted to the OADM unit 22. The above-mentioned problem that noise light does not seem to be visible by passing through can be solved. Therefore, even if the relay station node B includes the OADM unit 22, by transmitting the no-path route, the noise light component is superposed every time the amplifier unit passes, and is received by the receiving amplifier 31 of the terminal station node C. By connecting a spectrum analyzer, the total OSNR from the start station node A to the end station node C can be measured.

FIG. 5 is a diagram showing another configuration example of the starting point station node A. The node that is the starting point of the OSNR measurement interval (starting station node A) does not necessarily have a light source. Therefore, a dummy light source 50 is provided at the starting station node A, and a switch SW1 for inputting and transmitting light from the dummy light source 50 in the OSNR measurement mode is provided. The dummy light source 50 generates light having the same wavelength band as that of the optical signal used in the normal operation mode. Note that the switch inserted between the multiplexing unit and the transmission amplifier unit in the start station node A and the terminal station node C, not limited to the relay station node B, is referred to as a switch SW1, and the reception amplifier unit and the separation unit are connected to each other. The switch inserted between them is called switch SW3.

FIG. 6 is a diagram showing a configuration example of the end station node C. At the node that is the end point of the OSNR measurement interval (end station node C), the receiving amplifier unit 31 outputs the optical power bra 311 that branches the received optical signal and the output for extracting the optical signal that also splits the optical signal to the outside. The terminal 312 is provided, and the OSNR check measuring instrument (spectrum analyzer) 40 is connected to the output terminal 312 to measure the OSNR from the starting station node A.

FIG. 7 is a diagram showing a second configuration of the WDM apparatus in the embodiment of the present invention. In the second configuration, the WDM equipment constitutes a ring system. In a ring system, each node can be a starting station node, and each node can be a terminal station node. it can. Therefore, as shown in the figure, a dummy light source 50 is provided at each node, and switches S Wl, SW 2, and SW 3 are arranged. The switch SW2 is a switch that selects either the bypassed wavelength multiplexed signal power or the optical signal from the dummy light source 50, and its output is input to the switch SW1. The switch SW1 operates to select either the optical signal from the switch SW2 (from the bypass) or the optical signal from the OADM unit 22 (with normal path power).

[0032] Figure 7 (a) shows the case where OSNR is measured for the optical signal route between node A and node.

Indicates the operating position of each switch in (OSNR measurement mode). In the node A, the switches SW1 and SW2 are operated so that the optical signal from the dummy light source 50 is input to the transmission amplifier unit 21. In node B, switches SW1 and SW3 are operated so as to bypass the OADM unit 22. Note that the switch SW3 of node B may use a 1: 1 optical power bra instead of a switch device and simply split the optical signal in two directions.

[0033] By the switching operation at node A and node B, node C receives the optical signal from the dummy light source 50 of node A without the noise light component being cut by the OADM unit 22 of node B. Can. Therefore, by connecting the spectrum analyzer 40 to the output terminal 312 of the receiving amplifier 31 of the node C, it is possible to measure the OSNR between the node A and the node C with high accuracy in one measurement at one power point. become able to.

[0034] Fig. 7 (b) shows the operating position of each switch in the normal operation mode. In the normal operation mode, the switch SW1 of node A and node B and the switch SW3 of node B and node C are operated so that the optical signal of the light source power passes through the demultiplexing unit. Switch SW 2 may be in either position.

FIG. 8 is a diagram showing a system configuration for remotely controlling each switch of the node. The CPU 70 (70A, 70B, 70C) of each node A, B, C is connected to the remote control terminal 80. In the configuration of FIG. 8, the CPUs 70B and 70C of the node B and the node C are connected to the CPU 70A of the node A via the photoelectric conversion unit 90 of each node, and the CPU 70A of the node A is connected to the control terminal 80 and the LAN line. Connected. Each node also includes a switch selection state memory 92 for storing the switching position of each switch.

[0036] Then, based on an instruction from the control terminal 80, the CPU 70 switches each switch SW1, SW2, S Give instructions to W3 and operate each switch. In this case, the CPU 70 and the remote control terminal 80 can be connected by means such as an in-band monitoring line between the CPUs, a modem, and a serial interface in addition to the LAN interface.

FIG. 9 is a diagram showing an example of a switch setting table held by the control terminal 80. As shown in the figure, the control terminal 80 is in the normal operation mode or in the OSNR measurement mode (condition 1), and in the OSNR measurement mode, any of the start station node, the relay station node, and the end station node Based on a certain force (Condition 2), it has a table for setting the switching position of switches SW1, SW2, SW3 of each node. Then, the operator of the control terminal 80 sets the mode of each node and the node type in the OSNR measurement mode, so that the control terminal 80 performs the switch operation on the CPU of each node according to this table. Give instructions.

FIG. 10 is a diagram showing a flowchart for controlling the switch operation of each node based on the table of FIG. In FIG. 10, various parameters related to OSNR measurement are input to the control terminal 80 (S10). Specifically, as described above, the OSNR measurement mode or normal operation mode parameters and the parameters related to the type of each node (whether it is a start station node or relay station node or end station node) are input.

[0039] If the control terminal 80 determines that it is not in the OSNR measurement mode (in the normal operation mode) based on the input parameters (S11), the switch of each node related to the node type is determined. The switch position instructs each node of the setting value in the setting table 4 in FIG.

[0040] In the case of the OSNR measurement mode in step S11, for the node set as the starting station node (YES in S12), the setting value in setting table 1 in Fig. 9 is instructed. For the node set as the relay node (YES in S13), the setting value in setting table 2 in Fig. 9 is instructed. For the node set as the terminal station node (NO in S13), the setting value in setting table 3 in FIG. 9 is instructed.

[0041] Each node for which the set value is instructed operates switches SW1, SW2, and SW3 according to the set value (S18). Then, the selection position by the operation is overwritten and saved in the switch selection state memory 92 (S19).

[0042] In this way, the switching operation of each node is remotely controlled by the control terminal 80, so that each It is not necessary to go to the node location and control the switch. For ONSR measurement, the operator only needs to go to the terminal station node and perform the measurement. Therefore, work man-hours and time can be reduced.

Industrial applicability

The present invention is applied to high-accuracy measurement of end-to-end total OSNR, which is indispensable for designing WDM equipment, by providing a bypass that does not pass the OADM part that separates and multiplexes wavelength-multiplexed signals at the relay node. be able to.

Claims

The scope of the claims

[1] A first node that multiplexes a plurality of optical signals having different wavelengths to generate a first wavelength multiplexed signal, and transmits the first wavelength multiplexed signal;

Receiving the first wavelength-division multiplexed signal from the first node, dividing the first wavelength-division multiplexed signal into optical signals for each wavelength, and further including a wavelength including at least a part of the divided optical signal; A plurality of different optical signals are multiplexed to generate a second wavelength multiplexed signal, a first path for transmitting the second wavelength multiplexed signal, and the received first wavelength multiplexed signal is divided and multiplexed. A second node having a second node for transmitting without

A wavelength division multiplexing apparatus comprising: a receiving node that receives the first wavelength multiplexed signal or the second wavelength multiplexed signal from the second node.

[2] In claim 1,

The second node includes a separation unit that separates the first wavelength multiplexed signal into optical signals for each wavelength on the first path, and a wavelength that includes at least a part of the divided optical signals. A multiplexing unit that multiplexes a plurality of optical signals to generate a second wavelength multiplexed signal, and the second path branches from the first path upstream of the separation unit, and the multiplexing unit The wavelength division multiplexing apparatus is characterized in that it joins the first path on the downstream side.

[3] In claim 1,

The second node selects the second path as the path of the first wavelength multiplexed signal in the OSNR measurement mode, and selects the first path in the normal operation mode. Division multiplexing equipment.

[4] In claim 3,

The wavelength division multiplexing apparatus, wherein the second node includes a plurality of switches for switching the first path or the second path.

[5] a first node that selects and transmits either a first wavelength multiplexed signal obtained by multiplexing a plurality of optical signals having different wavelengths or a dummy optical signal;

The first wavelength multiplexed signal is divided into optical signals for each wavelength, and a plurality of optical signals having different wavelengths including at least a part of the divided optical signals are multiplexed to obtain a second wavelength multiplexed signal. A first path for transmitting the second wavelength multiplexed signal and a second path for transmitting the dummy optical signal without being divided and multiplexed can be selected. A second node,

A wavelength division multiplexing apparatus comprising: a receiving node that receives the second wavelength multiplexed signal or dummy optical signal from the second node.

[6] In claim 5,

The first node selects and transmits the dummy optical signal in an OSNR measurement mode, and selects and transmits the first wavelength multiplexed signal in a normal operation mode. The second node A wavelength division multiplexing apparatus, wherein the second path is selected in an OSNR measurement mode, and the first path is selected in a normal operation mode.

[7] In claim 6,

The first node has a first switch for selecting the first wavelength multiplexed signal or the dummy optical signal!

The wavelength division multiplexing apparatus, wherein the second node has a plurality of second switches for switching the first path or the second path.

[8] In claim 7,

A wavelength division multiplexing apparatus comprising a control device for remotely operating the first switch and the second switch.