Network management device, network management system, and network management program

Abstract

This invention provides a network management device that suppresses transmission errors caused by XPM (cross-phase modulation). [Solution] A network management device for managing an optical network including at least two optical transmission devices facing each other via a transmission path, comprising: a determination unit that, when a path setting for the optical network is requested, determines whether or not an error occurs in the transmission of the signal light based on the type of the transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path; and a setting unit that, when it is determined that an error has occurred, sets a path in the optical network using an unused wavelength different from a specific wavelength of the signal light that has the same delay amount as the secondary excitation light.

Description

Technical Field

[0001] The present disclosure relates to a network management device, a network management system, and a network management program.

Background Art

[0002] ROADM (Reconfigurable Optical Add / Drop Multiplexer) that can dynamically change network path routes is known. As an optical device for realizing ROADM, WSS (Wavelength Selective Switch) is also known. The WSS has three functions: a demultiplexing function for separating input optical signals in wavelength units, a switching function for selecting the demultiplexed optical signals, and a multiplexing function for combining the selected optical signals (see, for example, Patent Document 1).

[0003] In addition, a technology is also known that suppresses XPM (Cross Phase Modulation) degradation of signal light in conformity with the fiber type of an optical transmission line (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, some ROADMs are equipped with a forward-excited Raman amplifier. A forward-excited Raman amplifier outputs forward-excited light that propagates in the same direction as the signal light propagating through the optical transmission path, thereby Raman-amplifying the signal light. The forward-excited light may include not only incoherent primary excitation light but also coherent secondary excitation light with a shorter excitation wavelength than the primary excitation light. Furthermore, the optical transmission path may partially include NZ-DSF (Non-Zero Dispersion Shifted Fiber).

[0006] When an optical transmission path includes a zero-dispersion-scale fiber (NZ-DSF), transmission errors may occur in the signal light due to secondary excitation light. The NZ-DSF has a quadratic delay characteristic with respect to the zero-dispersion wavelength. Due to this delay characteristic, the signal light and secondary excitation light propagate through the NZ-DSF at partially the same speed. The aforementioned XPM (X-wavelength dispersion) is strongly generated between lights propagating at the same speed. Therefore, the signal light is strongly affected by XPM from the secondary excitation light. As a result, there is a risk of transmission errors occurring in the signal light due to XPM.

[0007] Therefore, one objective is to provide a network management device, a network management system, and a network management program that suppress transmission errors caused by XPM. [Means for solving the problem]

[0008] In one embodiment, the network management device is a network management device that manages an optical network including at least two optical transmission devices facing each other via a transmission path, and when a path setting for the optical network is requested, it includes a determination unit that determines whether or not an error occurs in the transmission of the signal light based on the type of the transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path, and a setting unit that, when it is determined that an error has occurred, sets a path in the optical network using an unused wavelength different from a specific wavelength of the signal light that has a common delay amount with the secondary excitation light. [Effects of the Invention]

[0009] This can suppress transmission errors caused by XPM. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram illustrates an example of APN. [Figure 2] This is an example of the optical circuit configuration for two opposing nodes. [Figure 3] This is an example of an optical circuit configuration for a forward-excited Raman amplifier. [Figure 4] Block diagram showing an example of NMS hardware configuration. [Figure 5] This is a branch of an example of the NMS functional configuration. [Figure 6] This is an example of an optical path management table. [Figure 7] This flowchart shows an example of how NMS works. [Figure 8] This diagram illustrates an example of the relationship between the wavelengths of the signal light, primary excitation light, and secondary excitation light, and the zero-dispersion wavelength. [Figure 9] This diagram illustrates an example of the distance from the zero-dispersion wavelength. [Figure 10] This diagram illustrates an example of the relationship between wavelength and delay characteristics. [Figure 11] (a) is an example of a comparative example. (b) is an example of an embodiment. [Figure 12] This is a block diagram showing an example of the functional configuration of the control unit. [Figure 13] This is an example of an operations management table. [Figure 14] This is a flowchart illustrating an example of the operation of the control unit. [Modes for carrying out the invention]

[0011] The following will explain the implementation of this project with reference to the drawings.

[0012] (First Embodiment) As shown in Figure 1, an APN (All Photonics Network) 50 includes PDNs (Photonics Domain Networks) 10 and 20, and a PCN (Photonics Core Network) 40.

[0013] The PDN 20 includes, for example, an optical metro network. The PDN 20 may include an optical access network in place of the optical metro network, or in addition to the optical metro network. The PDN 10 has basically the same network configuration as the PDN 20 except that the telecommunications carrier managing the PDN 20 is different, and detailed description thereof will be omitted.

[0014] The PDN 20 includes a plurality of optical transmission apparatuses (hereinafter referred to as nodes) 21, 22, 23, 24, and 25 such as ROADMs. Similarly, the PDN 10 includes a plurality of nodes 11, 12, 13, 14, and 15. Although details will be described later, each of the plurality of nodes 11, ..., 25 is provided with a WSS. Therefore, each of the plurality of nodes 11, ..., 25 can separate signal light in units of wavelengths, can select a demultiplexed optical signal, and can multiplex the selected signal light.

[0015] The node 24 is connected to a mobile base station 26 via an optical transmission line F2. The node 25 is connected to a mobile base station 27 via an optical transmission line F3. Any of the nodes 21, 22, and 23 may be connected to any of the mobile base stations 26 and 27. The node 11 is connected to a mobile base station 16 via an optical transmission line F1. Any of the nodes 12, 13, 14, and 15 may be connected to the mobile base station 16.

[0016] Nodes 21, 22, 23, 24, and 25 are connected in a ring configuration by optical transmission paths F5 and F7. Optical transmission path F5 is, for example, SMF (Single Mode Fiber). Optical transmission path F7 is, for example, NZ-DSF. Both SMF and NZ-DSF are types of optical fibers. NZ-DSF may be TWRS (True Wave Reduced Slope) fiber or any other type of optical fiber. For example, node 22 is connected to nodes 23 and 24 which are adjacent to node 22. Nodes 21, 22, 23, 24, and 25 may also be connected in a mesh configuration by optical transmission paths F5 and F7. In this case, node 22 is connected not only to nodes 23 and 24 which are adjacent to node 22, but also to nodes 21 and 25 which are not adjacent to node 22.

[0017] Similarly, nodes 11, 12, 13, 14, and 15 are connected in a ring configuration by optical transmission path F4. Optical transmission path F4 is, for example, an SMF. Nodes 11, 12, 13, 14, and 15 may also be connected in a mesh configuration by optical transmission path F4. Nodes 21, 22, 23, 24, and 25 may be connected in a linear configuration by optical transmission paths F5 and F7. Furthermore, nodes 11, 12, 13, 14, and 15 may also be connected in a linear configuration by optical transmission path F4.

[0018] Nodes 21, 22, 23, 24, and 25 have their optical paths configured by the Network Management System (NMS) 200. NMS 200 is an example of a network management device. Optical paths confined within PDN 20 are configured by NMS 200. Similarly, nodes 11, 12, 13, 14, and 15 have their optical paths configured by NMS 100. Optical paths confined within PDN 10 are configured by NMS 100. Note that the network management system is implemented by at least two of nodes 21, 22, 23, 24, and 25 and NMS 200. For example, the network management system is implemented by nodes 21, 24 and NMS 200.

[0019] PCN40, like PDN10 and 20, includes multiple nodes 41, 42, and 43. In PCN40, nodes 14 and 21 are shared as POIs (Points of Interface). Therefore, PCN40 may also include nodes 14 and 21. Nodes 14, 21, 41, 42, and 43 are connected in a ring configuration by optical transmission path F6. Optical transmission path F6 is, for example, an SMF. Node 14 is connected to adjacent nodes 41 and 43. Nodes 14, 21, 41, 42, and 43 may also be connected in a mesh configuration by optical transmission path F6.

[0020] Nodes 41, 42, and 43 are directly monitored and controlled by the optical network controller (denoted as PN-C in Figure 1) 30. The optical network controller 30 is another example of a network management device. Node 14 is indirectly monitored and controlled by the optical network controller 30 via the NMS 100. Node 14 may also be directly monitored and controlled by the optical network controller 30. Similarly, node 21 is indirectly monitored and controlled by the optical network controller 30 via the NMS 200. Node 21 may also be directly monitored and controlled by the optical network controller 30.

[0021] In this way, in APN50, PDN10 and PCN40 are optically connected. Similarly, in APN50, PDN20 and PCN40 are optically connected. This allows the optical network controller 30 to manage all optical paths accommodated in APN50 at once. In APN50, optical paths are assigned to each optical communication service, so as the number of optical communication services increases, a huge number of wavelengths corresponding to the optical paths will be required.

[0022] As will be explained in more detail later, at any of nodes 11, ..., 25 and nodes 41, 42, 43, wavelength conversion of the input signal light may be performed, resulting in the output of signal light with a different wavelength than the input signal light. For example, if signal light with wavelength "λ1" is input to node 21, node 21 converts the wavelength "λ1" of the signal light to wavelength "λ2" and outputs signal light with wavelength "λ2". Therefore, if, for example, an optical path with node 11 as the starting node and node 24 as the ending node is set up and connected in APN50, signal light of various wavelengths, including wavelengths "λ1" and "λ2", may be transmitted end-to-end using that optical path as a communication route.

[0023] Referring to Figure 2, the details of nodes 21 and 24 will be described as an example. Nodes 21 and 24 are indirectly connected via node 25. Alternatively, node 25 could be removed from PDN20, allowing nodes 21 and 24 to directly connect. Note that nodes 21 and 24 have basically the same configuration, but in each case, configurations other than those necessary for this explanation are omitted.

[0024] First, let's describe node 21. Node 21 comprises multiple optical transmitters (indicated as Tx in Figure 2) 21A, an MCS (Multicast Switch) 21B, and a WSS 21C. Node 21 also includes an OAO (Optical-Analog-Optical) type wavelength converter (indicated as OAO Cnv in Figure 2) 21D, EDFAs (Erbium Doped Fiber Amplifiers) 21E and 21F, a forward-excited Raman amplifier (indicated as FWD Raman in Figure 2) 21G, and a control unit 21H.

[0025] Multiple optical transmitters 21A transmit signal light of different wavelengths from each other. For example, one of the multiple optical transmitters 21A transmits signal light Ls5 with wavelength "λ5". The multiple optical transmitters 21A are optically connected to the MCS 21B. As a result, the signal light Ls5 is input to the MCS 21B.

[0026] MCS21B is optically connected to WSS21C. MCS21B is electrically connected to control unit 21H. When signal light Ls5 is input to MCS21B, it detects the wavelength "λ5" of signal light Ls5, notifies control unit 21H, and outputs signal light Ls5 to WSS21C. As a result, signal light Ls5 is input to WSS21C.

[0027] WSS21C is optically connected to the OAO type wavelength converter 21D and EDFA 21E, 21F. WSS21C is electrically connected to the control unit 21H. WSS21C includes a demultiplexer that separates the input signal light on a wavelength basis, an optical switch that identifies a signal light of any wavelength and selects and switches the path to output the identified signal light, and a multiplexer that combines and outputs the signal light.

[0028] Based on electrical instructions from the control unit 21H, the WSS21C switches the paths of the signal light Ls1 input to node 21 and the signal light Ls5 input from MCS21B. For example, based on instructions from the control unit 21H, the WSS21C switches the path of signal light Ls1 from the EDFA21F side to the OAO type wavelength converter 21D side. For example, based on instructions from the control unit 21H, the WSS21C switches the path of signal light Ls5 from the EDFA21F side to the EDFA21E side. As a result, signal light Ls1 is input to the OAO type wavelength converter 21D, and signal light Ls5 is input to the EDFA21E.

[0029] The OAO-type wavelength converter 21D converts the input signal light Ls1 of wavelength "λ1" to signal light Ls2 of wavelength "λ2" and outputs it, based on instructions from the control unit 21H. Wavelength "λ1" is an example of a specific wavelength. Specifically, when signal light Ls1 is input to the OAO-type wavelength converter 21D, it converts signal light Ls1 into an electrical analog signal and amplifies it. After amplifying the electrical analog signal, the OAO-type wavelength converter 21D compensates for the phase of the electrical analog signal and then converts the electrical analog signal into signal light Ls2 of wavelength "λ2". The OAO-type wavelength converter 21D amplifies signal light Ls2 of wavelength "λ2" and outputs it to the WSS21C. In this way, the OAO-type wavelength converter 21D can convert and output the input signal light on a wavelength basis without converting it to an electrical digital signal.

[0030] EDFA21E is connected to optical transmission path F5. EDFA21E amplifies the signal light Ls5 and outputs it to optical transmission path F5. EDFA21F is connected to optical transmission path F7 via forward-excited Raman amplifier 21G. EDFA21F amplifies the signal light Ls2 and outputs it to forward-excited Raman amplifier 21G.

[0031] The forward-excited Raman amplifier 21G outputs a forward-excited light Lpf based on electrical instructions from the control unit 21H. The forward-excited light Lpf propagates in the same direction as the propagation direction of the signal light Ls2. The forward-excited light Lpf is output from node 21 to the optical transmission path F7. The signal light Ls2 is Raman-amplified within the optical transmission path F7 by the forward-excited light Lpf.

[0032] Next, node 24 will be described. Node 24 comprises multiple optical receivers (denoted as Rx in Figure 2) 24A, MCS 24B, WSS 24C, EDFA 24E, 24F, and a control unit 24H. Node 24 may also include a back-excited Raman amplifier upstream of EDFA 24F. The back-excited Raman amplifier can output back-excited light that propagates in the opposite direction to the propagation direction of the signal light Ls2, based on electrical instructions from the control unit 24H.

[0033] EDFA24E is connected to optical transmission path F5. EDFA24E amplifies the signal light Ls5 and outputs it to WSS24C. EDFA24F is connected to optical transmission path F7. EDFA21F amplifies the signal light Ls2 and outputs it to WSS24C. WSS24C is optically connected to EDFA24E and 24F. WSS24C is electrically connected to the control unit 24H. WSS24C includes a demultiplexer, an optical switch, and a multiplexer.

[0034] Based on electrical instructions from the control unit 24H, the WSS24C switches the paths of signal light Ls2 input from optical transmission path F7 and signal light Ls5 input from optical transmission path F5. For example, based on instructions from the control unit 24H, the WSS24C switches the path of signal light Ls2 from the optical transmission path F2 side to the MCS24B side. For example, based on instructions from the control unit 24H, the WSS24C switches the path of signal light Ls5 from the MCS24B side to the optical transmission path F2 side. As a result, signal light Ls2 is input to the MCS24B. Signal light Ls5 is output to optical transmission path F2.

[0035] MCS24B is optically connected to WSS24C and multiple optical receivers 24A. Each of the multiple optical receivers 24A receives signal light of a different wavelength. When signal light Ls2 is input to MCS47, based on instructions from the control unit 24H, it selects and outputs a path from among multiple paths that outputs signal light Ls2. As a result, one of the multiple optical receivers 24A corresponding to wavelength "λ2" can receive signal light Ls2.

[0036] Refer to Figure 3 for a detailed explanation of the forward-excited Raman amplifier 21G.

[0037] The forward-excited Raman amplifier 21G comprises multiple primary excitation light sources (indicated as 1st P-LDs in Figure 3) 71A, 71B, 71C, multiple secondary excitation light sources (indicated as 2nd P-LDs in Figure 3) 72A, 72B, 72C, 72D, 72E, multiple polarization couplers 73, 74A, 74B, multiple multiplexing filters 75, 76, 78, 79, and a WDM (Wavelength Division Multiplexing) coupler 80. The primary excitation light sources 71A, 71B, 71C are examples of first light sources. The secondary excitation light sources 72A, 72B, 72C, 72D, 72E are examples of second light sources.

[0038] The primary excitation light sources 71A, 71B, and 71C output incoherent primary excitation light Lp1 with wavelengths that differ from each other. The excitation wavelengths of the primary excitation light Lp1 are all shorter than the shortest wavelength belonging to the C-band (Conventional-band). Multiple secondary excitation light sources 72A, 72B, 72C, 72D, and 72E output coherent secondary excitation light Lp2 with wavelengths that differ from each other. The excitation wavelengths of the secondary excitation light Lp2 are all shorter than the shortest excitation wavelength of the primary excitation light Lp1. The primary excitation light sources 71A, 71B, and 71C and the secondary excitation light sources 72A, 72B, 72C, 72D, and 72E use ASE (Amplified Spontaneous Emission) light sources. By using ASE light sources, the effects of RIN (Relative Intensity Noise) caused by either or both of the primary excitation light Lp1 and secondary excitation light Lp2 are suppressed. As a result, the degradation of transmission performance is suppressed, and the transmission distance is extended.

[0039] The primary excitation light sources 71A and 71B are optically connected to the polarization coupler 73. The polarization coupler 73 combines the orthogonal polarizations of the primary excitation light Lp1 output from each of the primary excitation light sources 71A and 71B and outputs them to the multiplexer 75. The multiplexer 75 combines the primary excitation light Lp1 output from the polarization coupler 73 and the primary excitation light Lp1 output from the primary excitation light source 71C and outputs them to the multiplexer 79.

[0040] The secondary excitation light sources 72A and 72B are optically connected to polarization coupler 74A. The secondary excitation light sources 72C and 72D are optically connected to polarization coupler 74B. Polarization coupler 74A combines the orthogonal polarizations of the secondary excitation light Lp2 output from each of the secondary excitation light sources 72A and 72B and outputs it to the multiplexer 76. Polarization coupler 74B combines the orthogonal polarizations of the secondary excitation light Lp2 output from each of the secondary excitation light sources 72C and 72D and outputs it to the multiplexer 76. The multiplexer 76 combines the secondary excitation light Lp2 output from each of the polarization couplers 74A and 74B and outputs it to the multiplexer 78. The multiplex filter 78 combines the secondary excitation light Lp2 output from the multiplex filter 76 and the secondary excitation light Lp2 output from the secondary excitation light source 72E, and outputs the combined light to the multiplex filter 79.

[0041] The multiplexer 79 combines the primary excitation light Lp1 output from the multiplexer 75 and the secondary excitation light Lp2 output from the multiplexer 78, and outputs the forward excitation light Lpf to the WDM coupler 80. The forward excitation light Lpf contains both the primary excitation light Lp1 and the secondary excitation light Lp2. The WDM coupler 80 outputs the forward excitation light Lpf in the same direction as the propagation direction of the signal light Ls2. As a result, the forward excitation light Lpf is output from node 21 to the optical transmission path F7.

[0042] Referring to Figure 4, the hardware configuration of NMS200 will be described. Note that the hardware configurations of the optical network controller 30 and NMS100 are basically the same as those of NMS200, so a detailed explanation will be omitted.

[0043] The NMS200 includes a CPU (Central Processing Unit) 200A as a processor, and RAM (Random Access Memory) 200B and ROM (Read Only Memory) 200C as memory. The NMS200 also includes a network interface 200D and a hard disk drive (HDD) 200E. An SSD (Solid State Drive) may be used as the storage device instead of the hard disk drive 200E.

[0044] The NMS200 may include, as needed, at least one of the following: input I / F 200F, output I / F 200G, input / output I / F 200H, and drive device 200I. The CPU 200A through the drive device 200I are connected to each other by an internal bus 200J. In other words, the NMS200 can be implemented by a computer.

[0045] Input I / F200F is connected to an input device 710. Examples of input devices 710 include keyboards, mice, and touch panels. Output I / F200G is connected to a display device 720. Examples of display devices 720 include liquid crystal displays. Input / Output I / F200H is connected to a semiconductor memory 730. Examples of semiconductor memory 730 include USB (Universal Serial Bus) memory and flash memory. Input / Output I / F200H reads the network management program stored in the semiconductor memory 730. Input I / F200F and Input / Output I / F200H are equipped with, for example, USB ports. Output I / F200G is equipped with, for example, a DisplayPort.

[0046] A portable recording medium 740 is inserted into the drive device 200I. The portable recording medium 740 can be a removable disk such as a CD (Compact Disc)-ROM or a DVD (Digital Versatile Disc). The drive device 200I reads the network management program recorded on the portable recording medium 740. The network interface 200D includes, for example, a LAN port and communication circuits. The communication circuits include either a wired communication circuit or a wireless communication circuit, or both. The network interface 200D is connected to nodes 21, 22, 23, 24, 25 and the optical network controller 30 via the communication network 200K. The communication network 200K includes either the Internet or a LAN (Local Area Network), or both.

[0047] The network management program stored in at least one of the ROM200C, HDD200E, and semiconductor memory 730 is temporarily stored in RAM200B by the CPU200A. The network management program recorded on the portable recording medium 740 is also temporarily stored in RAM200B by the CPU200A. By executing the stored network management program, the CPU200A realizes various functions described later and also executes a network management method including various processes described later. The network management program should conform to the flowchart described later.

[0048] The functional configuration of NMS200 will be explained with reference to Figures 5 and 6. Figure 5 shows the main functional components of NMS200. Note that the functional configurations of the optical network controller 30 and NMS100 are basically the same as those of NMS200, so a detailed explanation will be omitted.

[0049] As shown in Figure 5, the NMS200 comprises a storage unit 210, a processing unit 220, an input unit 230, and an output unit 240. The storage unit 210 can be implemented by either or both of the RAM 200B and HDD 200E described above. The processing unit 220 can be implemented by the CPU 200A described above. The input unit 230 and the output unit 240 can be implemented by the network I / F 200D described above.

[0050] The memory unit 210, processing unit 220, input unit 230, and output unit 240 are connected to each other. The memory unit 210 includes a wavelength memory unit 211 and an optical path management memory unit 212. The processing unit 220 includes a determination unit 221, a search unit 222, and a setting unit 223.

[0051] The wavelength memory unit 211 stores the excitation wavelengths of the secondary excitation light Lp2 and the zero-dispersion wavelength of the NZ-DSF. If the NZ-DSF is a TWRS fiber, the wavelength memory unit 211 stores 1452 nm (nanometers) as the zero-dispersion wavelength. The optical path management memory unit 212 stores the optical path management table. As shown in Figure 6, the optical path management table has multiple items such as node ID (Identifier), path, wavelength, usage status, and XPM generation.

[0052] The Node ID field registers identifiers that identify nodes such as Node 21 and Node 24. For example, the identifier "ND01" is registered as the identifier for Node 21. The Path field registers identifiers for the paths that output signal light Ls1, signal light Ls2, signal light Ls5, etc. The Wavelength field registers the wavelengths that can be used for transmitting signal light Ls1, signal light Ls2, signal light Ls5, etc. The Usage Status field registers the usage status of the wavelengths. For example, if "Used" is registered for the wavelength usage status, it means that the wavelength has already been used. If "Unused" is registered for the wavelength usage status, it means that the wavelength has not yet been used. The XPM Occurrence field registers whether or not XPM has occurred due to secondary excitation light Lp2. If XPM occurs, for example, a transmission error may occur in signal light Ls1. Examples of transmission errors include a change in the phase of signal light Ls1, or Node 24 being unable to receive signal light Ls1 from Node 21.

[0053] When the optical network controller 30 requests the setting of a path to the PDN 20 via the input unit 230, the determination unit 221 determines whether or not a transmission error occurs in the transmission of signal light. Specifically, when the setting of a path is requested, the determination unit 221 identifies the types of optical transmission paths F5 and F7 located downstream of node 21 and the conditions of the forward-excited Raman amplifier 21G.

[0054] For example, the determination unit 221 determines whether or not the optical transmission path F7 is an NZ-DSF. Based on the transmission path information of the APN50 managed in advance by node 21, the determination unit 221 can determine the type of optical transmission paths F5 and F7. The determination unit 221 also determines whether or not node 21 has a forward-excited Raman amplifier 21G. Based on the node configuration information managed in advance by node 21, the determination unit 221 can determine the presence or absence of the forward-excited Raman amplifier 21G. The transmission path information and node configuration information may be managed by the optical network controller 30.

[0055] Furthermore, if the optical transmission path F7 is an NZ-DSF and node 21 has a forward-excited Raman amplifier 21G, the determination unit 221 acquires each excitation wavelength and zero-dispersion wavelength of the secondary excitation light Lp2 from the wavelength memory unit 211. Once the determination unit 221 acquires each excitation wavelength and zero-dispersion wavelength of the secondary excitation light Lp2, it determines whether or not a transmission error occurs in the transmission of the signal light based on each excitation wavelength of the secondary excitation light Lp2, the zero-dispersion wavelength, and the relationship between wavelength and delay characteristics in the optical transmission path F7. For example, if any of the excitation wavelengths of the secondary excitation light Lp2 superimpose on the wavelength λ1 of the signal light Ls1 with the zero-dispersion wavelength in between, the determination unit 221 determines that a transmission error occurs. The details of the determination unit 221 will be explained in detail later.

[0056] When a transmission error occurs, the search unit 222 accesses the optical path management storage unit 212 and searches for and identifies a wavelength for which "unused" is registered as the wavelength usage status and "none" is registered as the presence or absence of XPM. Specifically, when a transmission error occurs, the search unit 222 identifies the node where the transmission error occurred from the optical path management table and identifies the direction of the optical transmission path where the transmission error occurred at the identified node. In this embodiment, the search unit 222 identifies the identifier "ND01" that identifies node 21 and identifies the identifier "DEG#1" that identifies the direction of the optical transmission path F7 where the transmission error occurred at node 21.

[0057] When the search unit 222 identifies these identifiers, it searches for and identifies wavelengths that are registered as "unused" in terms of wavelength usage and as "none" in terms of XPM generation, based on these identifiers. In this embodiment, for example, the search unit 222 identifies wavelength "λ2". As will be described in detail later, the search unit 222 identifies an unused wavelength λ2 that is different from the wavelength "λ1" of the signal light Ls1, which has the same delay amount as the secondary excitation light Lp2.

[0058] The setting unit 223 sets a path in PDN20 that uses the wavelength "λ2" identified by the search unit 222. More specifically, the setting unit 223 sets a path using the unused wavelength "λ2" when the delay amount of the signal light Ls1 and the delay amount of the secondary excitation light Lp2 are symmetrical with respect to the zero-dispersion wavelength in the optical transmission path F7. For example, the setting unit 223 outputs a setting to the control unit 21H of node 21 via the output unit 240 to convert wavelength "λ1" to the unused wavelength "λ2". This allows the setting unit 223 to set a path in PDN20 that uses the unused wavelength "λ2". In addition, the setting unit 223 outputs the destination of the signal light Ls2 of wavelength "λ2" to the control unit 24H of node 24 via the output unit 240. This allows the control unit 24H to notify the MCS24B of the destination of the signal light Ls2, and the MCS24B can switch the path through which the signal light Ls2 is output.

[0059] The operation of NMS200 will be explained with reference to Figures 7 through 10. Note that the optical network controller 30 and NMS100 operate essentially the same as NMS200, so a detailed explanation will be omitted.

[0060] First, as shown in Figure 7, the determination unit 221 waits until a path setting is requested (step S1: NO). As described above, the path setting is input to the determination unit 221 from the optical network controller 30. The optical network controller 30 can output the path setting based on instructions from a terminal device operated by, for example, an APN50 operator.

[0061] When a path setting is requested (step S1: YES), the determination unit 221 determines whether or not the error occurrence conditions are met (step S2). The error occurrence conditions are conditions that indicate there is a risk of a transmission error occurring in the transmission of signal light Ls1. The error occurrence conditions include three conditions: a first condition, a second condition, and a third condition. The first condition relates to the type of optical transmission path F7. For example, the first condition defines that the optical transmission path F7 is an NZ-DSF. The second condition relates to the conditions of the optical amplifier that outputs secondary excitation light Lp2 that propagates in the same direction as the propagation direction of signal light Ls1 propagating through the optical transmission path F7. For example, the second condition defines that there is a forward-excited Raman amplifier 21G at node 21. The third condition relates to the relationship between wavelength and delay characteristics in the optical transmission path F7. For example, the third condition defines that one of the excitation wavelengths of the secondary excitation light Lp2 is superimposed on the wavelength λ1 of the signal light Ls1, with the zero-dispersion wavelength of the NZ-DSF in between.

[0062] The third condition will be explained in more detail. As shown in Figure 8, wavelengths belonging to the C-band or L-band (Long wavelength band) are used for the transmission of the signal lights Ls1, Ls2, and Ls5 mentioned above. Therefore, for example, wavelengths "λ1", "λ2", and "λ5" belong to either the C-band or the L-band. For example, wavelengths "λ1" and "λ2" belong to the C-band, and wavelength "λ5" belongs to the L-band.

[0063] Each of the three primary excitation light Lp1s described above uses an excitation wavelength shorter than the shortest wavelength in the C band. The excitation wavelength of the first primary excitation light Lp1 is the shortest of the three primary excitation light Lp1s. The excitation wavelength of the third primary excitation light Lp1 is the longest of the three primary excitation light Lp1s. Therefore, the excitation wavelength of the second primary excitation light Lp1 lies between the excitation wavelengths of the first and third primary excitation light Lp1s. The zero-dispersion wavelength "λz" of the NZ-DSF is often located near the excitation wavelength of the second primary excitation light Lp1.

[0064] Each of the five secondary excitation light Lp2s described above uses an excitation wavelength shorter than the shortest excitation wavelength of the primary excitation light Lp1. The excitation wavelength of the first secondary excitation light Lp2 is the shortest of the five secondary excitation light Lp2s. The excitation wavelength of the fifth secondary excitation light Lp2 is the longest of the five secondary excitation light Lp2s. Therefore, for example, the excitation wavelength "λc" of the third secondary excitation light Lp2 lies between the excitation wavelength of the first secondary excitation light Lp2 and the excitation wavelength of the fifth secondary excitation light Lp2.

[0065] Although not shown in Figure 8, the excitation wavelength of the second secondary excitation light Lp2 lies between the excitation wavelength of the first secondary excitation light Lp2 and the excitation wavelength "λc" of the third secondary excitation light Lp2. The excitation wavelength of the fourth secondary excitation light Lp2 lies between the excitation wavelength of the fifth secondary excitation light Lp2 and the excitation wavelength "λc" of the third secondary excitation light Lp2. If the excitation wavelengths of the first to fourth secondary excitation lights Lp2 are virtually arranged symmetrically around the zero-dispersion wavelength "λz", then these excitation wavelengths will superimpose on the C-band and L-band.

[0066] Specifically, as shown in Figure 9, when the distance from the zero-dispersion wavelength "λz" is expressed on the wavelength axis, the excitation wavelengths of the second to fourth secondary excitation light Lp2 belong to the C band, and the excitation wavelength of the first secondary excitation light Lp2 partially belongs to the L band. As shown in Figure 10, the NZ-DSF exhibits a quadratic delay symmetry as a delay characteristic, with the zero-dispersion wavelength "λz" in between. Due to this delay characteristic of the NZ-DSF, the delay amounts of the signal light Ls1 and some of the secondary excitation light Lp2 become equivalent, causing the signal light Ls1 and secondary excitation light Lp2 to propagate through the NZ-DSF at partially the same speed. As a result, the signal light Ls1 is strongly affected by XPM from some of the secondary excitation light, and transmission errors caused by XPM occur in the signal light Ls1.

[0067] In other words, the determination unit 221 determines whether all of the first, second, and third conditions described above are met. If at least one of the first, second, and third conditions is not met, the determination unit 221 determines that the error occurrence conditions are not met, as shown in Figure 7 (Step S2: NO). If all of the first, second, and third conditions are met, the determination unit 221 determines that the error occurrence conditions are met (Step S2: YES).

[0068] If the error conditions are met, the search unit 222 searches for an unused wavelength (step S3). That is, the search unit 222 accesses the optical path management storage unit 212 and searches the optical path management table for an unused wavelength where no XPM occurs. As a result, for example, the search unit 222 identifies the wavelength "λ2" (see Figure 6). If the error conditions are not met, the determination unit 221 skips the process in step S3. In this case, the wavelength "λ1" of the signal light Ls1 is maintained as is.

[0069] If the process in step S3 is executed or if the process in step S3 is skipped, the setting unit 223 outputs a setting instruction (step S4) and terminates the process. More specifically, if the process in step S3 is executed, the setting unit 223 outputs a setting instruction to the control unit 21H of node 21 instructing it to convert wavelength "λ1" to wavelength "λ2". As a result, the control unit 21H changes the settings of WSS21C and OAO type wavelength converter 21D. Specifically, the control unit 21H switches the setting of the path for outputting the signal light Ls1 of wavelength "λ1" to the OAO type wavelength converter 21D side for WSS21C. The control unit 21H also sets the conversion of wavelength "λ1" to wavelength "λ2" for the OAO type wavelength converter 21D.

[0070] As a result, a signal light Ls1 with wavelength "λ1" is input to WSS21C. When signal light Ls1 is input to WSS21C, WSS21C outputs signal light Ls1 toward the OAO type wavelength converter 21D (see Figure 2). Then, when signal light Ls1 is input to the OAO type wavelength converter 21D, the OAO type wavelength converter 21D converts signal light Ls1 with wavelength "λ1" to signal light Ls2 with wavelength "λ2" and outputs it toward WSS21C. If the processing in step S3 is skipped, for example, WSS21C outputs signal light Ls1 toward EDFA21E.

[0071] Referring to Figures 11(a) and (b), the present case will be explained by comparing the comparative example and the example.

[0072] First, as shown in Figure 11(a), in the comparative example, the excitation wavelength of the third secondary excitation light Lp2 and the wavelength of the signal light Ls1 are located approximately equidistant from the zero-dispersion wavelength "λz" and partially superimpose. Therefore, based on the delay characteristics described above, XPM caused by the third secondary excitation light Lp2 occurs in the signal light Ls1. Consequently, a transmission error occurs in the transmission of the signal light Ls1.

[0073] On the other hand, as shown in Figure 11(b), in the embodiment, the excitation wavelength of the third secondary excitation light Lp2 and the wavelength of the signal light Ls2 are located at different distances from the zero-dispersion wavelength "λz". Therefore, based on the delay characteristics described above, the generation of XPM for the signal light Ls2 caused by the third secondary excitation light Lp2 is avoided. As a result, transmission errors are suppressed in the transmission of the signal light Ls2. In this way, when the error generation conditions are met, the NMS200 can suppress transmission errors by instructing node 21 to perform a wavelength conversion to avoid the generation of XPM.

[0074] (Second Embodiment) A second embodiment of this invention will be described with reference to Figures 12 to 14. In Figure 12, components similar to those of the NMS200 described with reference to Figure 5 are denoted by corresponding reference numerals, and their detailed descriptions are omitted. For example, in Figure 12, the determination unit 921 performs basically the same processing as the determination unit 221 of the NMS200. The search unit 922 performs basically the same processing as the search unit 222 of the NMS200. The setting unit 923 performs basically the same processing as the setting unit 223 of the NMS200.

[0075] First, as shown in Figure 12, the control unit 21H of node 21 includes a storage unit 910, a processing unit 920, an input unit 930, and an output unit 940. The storage unit 910 can be implemented by RAM, ROM, or NVM (Non-Volatile Memory). The processing unit 920 can be implemented by a CPU, ASIC (Application Specific Integrated Circuit), or FPGA (Field Programmable Gate Array). The input unit 230 and output unit 240 can be implemented by an input / output interface.

[0076] The memory unit 910, processing unit 920, input unit 930, and output unit 940 are connected to each other. The memory unit 910 includes a wavelength memory unit 911 and an operation management memory unit 912. The processing unit 920 includes a determination unit 921, a search unit 922, a setting unit 923, and an alarm unit 924.

[0077] The wavelength memory unit 911 stores the excitation wavelengths of the secondary excitation light Lp2 and the zero-dispersion wavelength of the NZ-DSF. The operation management memory unit 912 stores the operation management table. As shown in Figure 13, the operation management table has multiple items such as path, wavelength, usage status, and XPM generation. In other words, the operation management table is a table from which the node ID item has been removed from the optical path management table described in the first embodiment. The information registered in each of the items of path, wavelength, usage status, and XPM generation is basically the same as the information registered in each of the items of path, wavelength, usage status, and XPM generation in the optical path management table, so a detailed explanation is omitted.

[0078] The determination unit 921 determines whether a transmission error occurs in the transmission of signal light when a path setting to the PDN20 is requested from the NMS200 via the input unit 930. If a transmission error occurs, the search unit 922 accesses the operation management storage unit 912 and searches for and identifies a wavelength for which "unused" is registered as the wavelength usage status and "none" is registered as the presence or absence of XPM.

[0079] When the search unit 922 identifies the wavelength "λ2", the setting unit 923 sets the path using wavelength "λ2" in the PDN20. Specifically, the setting unit 923, via the output unit 940, sets the WSS21C to direct the signal light Ls1 to the OAO type wavelength converter 21D. The setting unit 923 also, via the output unit 940, sets the OAO type wavelength converter 21D to convert wavelength "λ1" to the unused wavelength "λ2". As a result, the setting unit 923 can set the path using wavelength "λ2" in the PDN20.

[0080] If the search unit 922 fails to identify an unused wavelength, the alarm unit 924 notifies the NMS200 of an alarm via the output unit 940. This allows the NMS200 to display information regarding the transmission error on a terminal device operated by the APN50 operator, for example, via the optical network controller 30.

[0081] The operation of the control unit 21H will be explained with reference to Figure 14.

[0082] The determination unit 921 waits until a path setting is requested (step S11: NO). When a path setting is requested (step S11: YES), the determination unit 921 determines whether or not the error occurrence conditions are met (step S12). If the error occurrence conditions are met (step S12: YES), the search unit 922 searches for unused wavelengths (step S13) and determines whether or not there are any unused wavelengths (step S14). If there are any unused wavelengths (step S14: YES), or if the process in step S13 is skipped, the setting unit 923 executes the setting process (step S15). The setting process includes setting the signal light Ls1 to be directed to the OAO type wavelength converter 21D for the WSS21C, and setting the wavelength "λ1" to an unused wavelength "λ2". After executing the setting process, the setting unit 923 terminates its process.

[0083] If there are no unused wavelengths (step S14: NO), the alarm unit 924 performs alarm processing (step S16). The alarm processing includes notifying the NMS200 of the alarm. As a result, as described above, information regarding the occurrence of a transmission error is displayed on the terminal device. After performing the alarm processing, the alarm unit 924 terminates its processing. Thus, instead of suppressing transmission errors by the NMS200, suppression of transmission errors by the node 21 may be adopted.

[0084] Furthermore, the following additional information is disclosed regarding the above explanation. (Note 1) A network management device for managing an optical network including at least two optical transmission devices facing each other via a transmission path, comprising: a determination unit that, when a path setting for the optical network is requested, determines whether or not an error occurs in the transmission of the signal light based on the type of the transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path; and a setting unit that, when it is determined that an error occurs, sets a path in the optical network using an unused wavelength different from a specific wavelength of the signal light that has the same delay amount as the secondary excitation light. (Note 2) The network management device according to Note 1, characterized in that the setting unit sets a path using the unused wavelength when the first delay amount of the signal light and the second delay amount of the secondary excitation light are symmetrical with respect to the zero-dispersion wavelength in the transmission path. (Note 3) The network management device according to Note 1 or 2, wherein the optical transmission device includes a wavelength converter that converts the specific wavelength on a wavelength basis, and the setting unit, when it determines that the error has occurred, outputs an instruction to the optical transmission device to convert the specific wavelength to the unused wavelength, thereby setting a path that uses the unused wavelength. (Note 4) The network management device according to Note 1 or 2, characterized in that the excitation wavelength of the secondary excitation light is shorter than the excitation wavelength of the primary excitation light propagating in the same direction as the propagation direction of the signal light, and the optical amplifier is a forward-excited Raman amplifier including a first light source that outputs the primary excitation light and a second light source that outputs the secondary excitation light. (Note 5) The network management device according to Note 4, characterized in that the primary excitation light is incoherent excitation light and the secondary excitation light is coherent excitation light. (Note 6) The network management device according to Note 4, characterized in that both the first light source and the second light source are ASE light sources. (Note 7) The network management device according to Note 1 or 2, characterized in that the transmission path is a non-zero-dispersion shift fiber, and the determination unit determines that the error occurs when the first delay amount of the signal light and the second delay amount of the secondary excitation light are symmetrical with respect to the zero-dispersion wavelength in the non-zero-dispersion shift fiber. (Note 8) A network management system comprising: at least two optical transmission devices facing each other via a transmission path; and a network management device that, when a path setting for an optical network including the optical transmission devices is requested, determines whether an error occurs in the transmission of the signal light based on the type of the transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path, and, if it is determined that an error occurs, sets a path in the optical network using an unused wavelength different from a specific wavelength of the signal light that has the same delay amount as the secondary excitation light. (Note 9) A network management program for managing an optical network including at least two optical transmission devices facing each other via a transmission path, wherein when a path setting for the optical network is requested, the program determines whether or not an error occurs in the transmission of the signal light based on the type of transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between wavelength and delay characteristics in the transmission path, and if it is determined that an error occurs, the program causes a computer to perform the process of setting a path in the optical network using an unused wavelength different from a specific wavelength of the signal light that has the same delay amount as the secondary excitation light. [Explanation of Symbols]

[0085] 10,20 PDN 21,24 nodes 21C WSS 21D OAO Wavelength Converter 21G forward-excited Raman amplifier 30 Optical Network Controllers 40 PCN 50 APN 100,200 NMS F5, F7 Optical Transmission Path

Claims

1. A network management device for managing an optical network including at least two optical transmission devices that are opposite each other via a transmission path, When a path setting for the optical network is requested, a determination unit determines whether or not an error occurs in the transmission of the signal light, based on the type of transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path. When it is determined that the aforementioned error has occurred, a setting unit sets a path in the optical network that uses an unused wavelength different from the specific wavelength of the signal light that has the same delay amount as the secondary excitation light, A network management device having the following features.

2. The setting unit sets a path using the unused wavelength when the first delay amount of the signal light and the second delay amount of the secondary excitation light are symmetrical with respect to the zero-dispersion wavelength in the transmission path. The network management device according to feature 1.

3. The optical transmission device includes a wavelength converter that converts the specific wavelength in wavelength units, When the setting unit determines that the error has occurred, it outputs an instruction to the optical transmission device to convert the specific wavelength to the unused wavelength, and sets a path using the unused wavelength. The network management device according to claim 1 or 2.

4. The excitation wavelength of the secondary excitation light is shorter than the excitation wavelength of the primary excitation light that propagates in the same direction as the propagation direction of the signal light. The optical amplifier is a forward-excited Raman amplifier including a first light source that outputs the primary excitation light and a second light source that outputs the secondary excitation light. The network management device according to claim 1 or 2.

5. The transmission line is a non-zero-dispersion shift fiber, The determination unit determines that the error occurs when the first delay amount of the signal light and the second delay amount of the secondary excitation light are symmetrical with respect to the zero-dispersion wavelength in the non-zero-dispersion shift fiber. The network management device according to claim 1 or 2.

6. At least two optical transmission devices facing each other via a transmission path, When a request is made to set a path for an optical network including the optical transmission device, a network management device determines whether or not an error occurs in the transmission of the signal light based on the type of transmission path, the conditions of an optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path, and if it is determined that an error occurs, sets a path in the optical network that uses an unused wavelength different from the specific wavelength of the signal light that has the same delay amount as the secondary excitation light, A network management system having

7. A network management program for managing an optical network including at least two optical transmission devices that are opposite each other via a transmission path, When a path setting for the optical network is requested, it is determined whether or not an error occurs in the transmission of the signal light based on the type of transmission path, the conditions of the optical amplifier that outputs secondary excitation light propagating in the same direction as the propagation direction of the signal light propagating through the transmission path, and the relationship between the wavelength and delay characteristics in the transmission path. If it is determined that the aforementioned error has occurred, the optical network is configured to use an unused wavelength that is different from the specific wavelength of the signal light that has the same delay amount as the secondary excitation light. A network management program that causes a computer to perform a process.

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