A reconfigurable optical add-drop multiplexer

Abstract

The present invention discloses a reconfigurable optical add-drop multiplexer, comprising: a line-side optical processing device, including a wavelength selective switch connected to a network node in the L dimension; a client-side optical processing device, including a bidirectional optical amplifier array and a multicast optical switch, the multicast optical switch including M 1×N-port optical splitters / couplers and N M×1-port optical switches, the wavelength selective switch being connected to the optical splitters / couplers one by one through the bidirectional optical amplifier array; wherein, x optical splitters receive signals from the network node and disperse the signals to y optical switches for selective output to the client side; N - y optical switches receive signals from the client side and select the corresponding couplers in the M - x range for coupling output corresponding to the required transmission dimension, x being an integer and less than M. The present invention realizes up-and-down wave deployment with the same multicast optical switch, reduces node deployment and development costs, saves rack space, and realizes flexible allocation of receiving and sending ports.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communication networks, and particularly to a reconfigurable optical add-drop multiplexer. Background Art

[0002] With the continuous progress of wavelength division multiplexing technology, flexibly supporting a mesh topology, dynamic capacity allocation, automated network control, and optical path setup are key elements in designing the next-generation optical transmission network. To achieve these functions, a reconfigurable optical add-drop multiplexer with a dynamic add-drop structure is required. To overcome the wavelength competition problem caused by single-port optical devices at service add-drop nodes, resulting in information loss, a multicast switch is applied to network nodes, greatly meeting the communication requirements between multiple ports. With the demand for services, multicast switches with a larger number of ports are applied to large-scale telecommunication networks. The emergence and development of edge networks have brought new requirements to multicast optical switches: low cost, low power consumption, and small footprint.

[0003] In existing telecommunication network nodes, taking the add-drop wavelength services in four directions as an example, locally, two 8×16 multicast optical switches receive the signals transmitted from the four directions and perform wavelength dropping, and at the same time, upload the information of the local network to each direction. However, when the usage scenario is a telecommunication network with less than 4 dimensions, one 8×16 multicast optical switch is used on each of the add and drop sides of the node, resulting in a high deployment cost; using different multicast optical switches on the add and drop sides will occupy a certain rack position, wasting valuable rack resources to a certain extent. At the same time, when the add and drop parts of the multicast switch are reconfigured, the two isolator structures of the supporting optical amplifier array limit its bidirectional transmission ability. The optical amplifier array can only make the entire module work properly by manually adjusting the input and output by staff, and does not have the function of automatically changing the amplification direction according to the signal transmission direction, restricting the flexible allocation of receiving and sending ports. Summary of the Invention

[0004] The purpose of the present invention is to provide a reconfigurable optical add-drop multiplexer, which realizes add and drop deployments using the same multicast switch, reduces the node deployment and development costs, saves rack space, and realizes the flexible allocation of receiving and sending ports.

[0005] To solve the above technical problems, the present invention provides a reconfigurable optical add-drop multiplexer, including:

[0006] An optical processor device on the line side, including a wavelength selection switch connected to a network node in the L dimension, where the wavelength selection switch is used to send or receive signals in the dimension where it is located;

[0007] The customer-side optical processor device includes a bidirectional optical amplifier array and a multicast optical switch. The multicast optical switch includes M 1×N-port splitters / couplers and N M×1-port optical switches. The wavelength selective switch is connected to the splitter / coupler one by one through the bidirectional optical amplifier array;

[0008] Among them, x splitters receive signals from the network node and disperse the signals to y optical switches for selective output to the customer side; N - y optical switches receive signals from the customer side and select the corresponding coupler in the range of M - x for coupling output according to the required transmission dimension. x is an integer and less than M.

[0009] As a further improvement of the present invention, the bidirectional optical amplifier array includes M bidirectional erbium-doped fiber amplifiers. One end of each bidirectional erbium-doped fiber amplifier is connected to the splitter / coupler one by one, and the other end is connected to the wavelength selective switch in the corresponding dimension. The signal amplification direction of the bidirectional erbium-doped fiber amplifier matches the signal transmission direction.

[0010] As a further improvement of the present invention, the bidirectional erbium-doped fiber amplifier includes an erbium-doped fiber amplifier. Both ends of the erbium-doped fiber amplifier are respectively connected with double branches. One end of the double branches converges and is connected to the splitter / coupler, and the other end of the double branches converges and is connected to the wavelength selective switch; optical circulators are respectively arranged at the convergence points of the double branches.

[0011] As a further improvement of the present invention, an optical isolator is arranged between the optical circulators on the same double branch.

[0012] As a further improvement of the present invention, the bidirectional optical amplifier array further includes a power detector, a control unit and a pump laser connected in sequence;

[0013] The power detector detects the signal power on the line where the erbium-doped fiber amplifier is located;

[0014] The control unit adjusts the gain of the erbium-doped fiber amplifier on this line through the pump laser according to the signal power.

[0015] As a further improvement of the present invention, the pump laser adopts an independent pump laser array or a shared pump laser; when the pump laser adopts an independent pump laser array, the independent pump laser array controls each erbium-doped fiber amplifier separately; when the pump laser adopts a shared pump laser, the pump laser is connected to each erbium-doped fiber amplifier through a fast adjustable optical attenuation array for selective control.

[0016] As a further improvement of the present invention, a tunable filter is arranged at one end of the optical switch output to the customer side.

[0017] As a further improvement of the present invention, M is equal to 8, N is equal to 16, and L is less than or equal to 4.

[0018] As a further improvement of the present invention, x is equal to 4, and y is less than or equal to 16.

[0019] As a further improvement of the present invention, two wavelength selective switches are provided on the network nodes of each dimension. One of the wavelength selective switches is used to send the signals of the network nodes of this dimension to the multicast optical switch, and the other wavelength selective switch is used to receive the client-side signals from the multicast optical switch.

[0020] Advantages of the present invention: Compared with the traditional situation where two or more multicast optical switches are required for up-wave and down-wave respectively, the present invention realizes the up-wave and down-wave deployment with the same multicast optical switch, reducing the deployment cost and splitting the device functions, thus reducing the development cost. For the limited rack resources of small-scale telecommunication networks, the present invention can save a certain amount of rack space; the receiving and sending ports are flexibly allocated, and there are symmetric and asymmetric allocation situations. When the up-wave and down-wave services are balanced, balanced allocation is adopted, and the number of up-wave and down-wave ports is balanced; when one of the services increases significantly, the number of ports corresponding to this service is appropriately increased for allocation, adopting an unbalanced allocation method to cope with different service demand changes, and can flexibly and reliably support all current and future services; when the up-wave and down-wave parts of the multicast switch are reconfigured, the present invention proposes a bidirectional fiber optic amplifier array compatible with the reconfigurable multicast switch, which can amplify the optical signals coming from both directions and has the function of automatically changing the amplification direction according to the signal transmission direction without manual adjustment. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the present invention adopting the balanced allocation method;

[0022] Figure 2 It is a schematic structural diagram of the existing optical add-drop multiplexer;

[0023] Figure 3 It is a schematic structural diagram of the multicast optical switch of the present invention adopting the asymmetric splitting method;

[0024] Figure 4 It is a schematic structural diagram of the bidirectional optical amplifier array based on independent pumping of the present invention;

[0025] Figure 5 It is a schematic structural diagram of the bidirectional optical amplifier array using a shared pump laser to provide pumping of the present invention. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited do not limit the present invention.

[0027] As described in the background art, in existing telecommunication network nodes, for example, Figure 2 as shown, taking the up / down wavelength services in four dimensions as an example, locally, two 8*16 multicast optical switches receive the signals transmitted from four directions and perform wavelength conversion downward, and at the same time upload the information of the local network to each direction. The 8*16 multicast optical switch on the left is responsible for the wavelength conversion side and receives the signals transmitted from each direction. After the received signal enters the module, first, power pre-compensation of the first-stage optical amplifier is performed to prevent distortion of the received signal caused by too low received power. Then, the optical signal is propagated to each lower-level optical switch through a first-stage optical splitter. Finally, the optical signal is received by configuring the connection of the optical switch. For the up-wavelength side, the transmitted signal is accurately sent to the coupler corresponding to a certain direction through the selection of the optical switch. After being multiplexed by the coupler, it is sent to a certain dimension to achieve the up-wavelength process. At the same time, since the multicast switch uses a power divider and the power divider has a certain insertion loss, the insertion loss of the entire module reaches more than 15 dB. In order to ensure that the signal received at the receiving end has a certain optical power, the multicast switch needs to be used in combination with an optical amplifier.

[0028] However, in the case of a telecommunication network with less than 4 dimensions in the usage scenario, one 8*16 multicast optical switch is used on each of the up-wavelength and down-wavelength sides of the node, resulting in a situation of excess ports, leading to higher costs; using different multicast optical switches on the up / down wavelength sides will occupy a certain rack position, wasting valuable rack resources to a certain extent. At the same time, when the up-wavelength and down-wavelength parts of the multicast switch are reconfigured, the multi-channel optical amplifier array does not have the function of automatically changing the amplification direction according to the signal transmission direction.

[0029] To solve the above problems, according to the characteristics of existing optical add-drop multiplexer nodes (pursuing colorless, directionless, and wavelength non-competitive, colorless means that each port on the customer side supports signals of any up / down wavelength; directionless means that the customer side can be connected to any dimension to send and receive signals; non-competitive means that when the number of channels with the same wavelength does not exceed the degree of the node, the output port can be assigned any wavelength), while only using one up / down wavelength structure, it is realized that each up / down wavelength port can support all wavelengths and be connected to any dimension. The multicast optical switch, as a commonly used up / down wavelength device in network nodes, supports the characteristics of being colorless, directionless, and non-competitive, and can be input from the upper end or the lower end. Therefore, the present invention provides a reconfigurable optical add-drop multiplexer, including:

[0030] A line-side optical processing device, comprising a wavelength selective switch connected to a network node in the L dimension, the wavelength selective switch being used to send or receive signals in the dimension;

[0031] The client-side optical processing device includes a bidirectional optical amplifier array and a multicast optical switch, wherein the multicast optical switch includes M 1×N port splitters / couplers and N M×1 port optical switches, and the wavelength selective switch is connected to the splitters / couplers in a one-to-one correspondence through the bidirectional optical amplifier array;

[0032] Among them, x splitters receive signals from network nodes and disperse the signals to y optical switches for selection and output to the client side; Ny optical switches receive signals from the client side and select couplers corresponding to the required transmission dimension within the range of Mx for coupling output, where x is an integer and less than M.

[0033] Compared with the traditional method of using two or more wavelet optical switches for adding and dropping waves respectively, the present invention realizes adding and dropping waves deployment with the same multicast optical switch, thereby reducing deployment cost, realizing the separation of device functions, and reducing development cost. For limited rack resources of small-scale telecommunication networks, the present invention can save a certain amount of rack space; flexibly allocate receiving and sending ports, and there are symmetrical allocation and asymmetrical allocation. When the adding and dropping wavelet services are balanced, balanced allocation is adopted, and the number of adding and dropping wavelet ports is balanced; when a certain service increases significantly, the allocation of the number of ports corresponding to the service is appropriately increased, and an unbalanced allocation method is adopted to cope with the changes in different service requirements, and all current and future services can be flexibly and reliably supported; when the adding and dropping wavelet parts of the multicast switch are reconfigured, the present invention proposes a bidirectional fiber optic amplifier array matched with the reconfigurable multicast switch, which can amplify optical signals transmitted from two directions, and has the function of automatically changing the amplification direction according to the signal transmission direction, without manual adjustment.

[0034] Example 1

[0035] like Figure 1 As shown, an embodiment of the present invention provides a reconfigurable optical add / drop multiplexer. For a four-dimensional telecommunications network node, each dimension is composed of two wavelength selection switches (line-side processing devices), which are responsible for sending and receiving signals. The local node is composed of an 8*16 multicast optical switch and an 8-way optical amplifier array (client-side processing device), that is, L=4, M=8, N=16. The local node sends and receives signals in each direction. Each dimension is connected to the upper wave side and the lower wave side of the local telecommunications network respectively, and an optical amplifier array is placed in between. A tunable filter is added to the receiving side of the local node, which is responsible for screening the useful signals transmitted to the local area in each dimension. The useful signal can be filtered out by adjusting the resonant frequency.

[0036] The present invention can flexibly allocate receiving and sending ports, and there are symmetric allocation and asymmetric allocation cases. When the up and down wave services are balanced, balanced allocation is adopted, and the number of up and down wave ports is balanced; when a certain service increases significantly, the allocation of the corresponding port number for this service is appropriately increased, and an unbalanced allocation method is adopted. Specifically as follows:

[0037] Symmetric allocation: In the case of 1:1 symmetric splitting of the multicast optical switch, as Figure 1 shown, in this case, the 8*16 multicast optical switch is divided into two functionally independent 4*8 multicast optical switches from the middle. On the right side, x = 4 and y = 8 is the lower wave side, and the remaining part on the left side is the upper wave side. There is an optical path between each optical splitter and coupler (optical splitter / coupler, which can perform optical splitting function or coupling function) and the optical switch, but in specific use, the direction of optical transmission is different. When the upper end of this device is the input, the input light is dispersed by the first part of the optical splitter to the optical switch in front of the input port for optical signal selection and output, completing the entire process from input to output. When the lower end of this device is the input, the input light first goes to the optical switch for output port selection, and then is coupled and output on the second part of the coupler. At this time, the optical splitter is used in reverse, and this device is a coupler, and its function is to couple the input optical signal for output. The above are the two input and output methods of the multicast optical switch. Through these two methods, some ports can be set as input ports and some ports can be set as output ports, so as to realize the function of this design.

[0038] Asymmetric allocation: As Figure 3 shown, the left side is the lower wave side and the right side is the upper wave side, and the transmission direction of the optical signal in the module is marked by the dotted arrow. When the service demand changes, for example, when the lower wave demand increases, that is, a large amount of services arrive at the 4 lower wave input ports above the left part and need to be received, it is possible that the 8 lower wave receiving ports below the left part may not be able to receive each arriving service in time. At this time, the path of the switch can be adjusted. Without disturbing the upper wave service, some ports below the right side can be divided into receiving ports to process the large amount of arriving services in time, thus solving the possible blocking problem. Similarly, when the upper wave demand increases, the port allocation can be adjusted, and the number of upper wave ports can be adjusted to 9 or more to meet the needs of the upper wave service.

[0039] During the configuration process of the optical switch: Since each optical switch is connected to each optical splitter, it is necessary to ensure that the input optical path signal cannot be coupled with the output optical path signal on the same path. The selection ports of the optical switch part in the multicast optical switch structure are closed and opened. The optical switch on the upper wave side is connected to the coupler to maintain the path. Although physically connected to the optical splitter on the lower wave side, it is in a disconnected state functionally. The optical switch on the lower wave side is connected to the optical splitter to maintain the path, and the coupler on the upper wave side is selected to be closed. That is, for a 1*8 optical switch, the optical switch responsible for the lower wave does not receive the optical signal on the upper wave. When configuring the optical switch, it is necessary to deny access to the four ports on the upper wave. Similarly, the optical switch on the lower wave side is the same.

[0040] Furthermore, when the network scale increases and the number of dimensions increases to more than 4, the ROADM can expand the dimension to 8 by adding a multicast optical switch.

[0041] In the existing small-scale telecommunication network of this embodiment, there is a situation of excess ports. For a certain 8*16 multicast optical switch, when the number of used dimensions is less than 4 ports, it can be flexibly converted into two 4*8 multicast optical switches, achieving a similar effect to two 8*16 multicast optical switches under a certain traffic in the telecommunication network. When the service demand changes, by reasonably allocating the receiving and sending ports, the transceiver speed can be improved to a certain extent, and the port resources can be better utilized. Adopting this configuration scheme can make full use of the limited equipment scale, reduce the network deployment conditions, and at the same time maintain a certain data exchange capacity. Compared with using two 4*8 multicast optical switches, the present invention has an advantage in cost and can achieve the same switching capacity with a smaller rack space.

[0042] Embodiment 2

[0043] Since it is necessary to compensate for the losses caused by using the multicast optical switch, the multicast optical switch needs to cooperate with the corresponding optical amplifier array. There are optical amplifiers on the upper and lower wave sides respectively. The function of the optical amplifier device is to compensate for the optical power of the received optical signal to prevent phenomena such as bit errors caused by too small received signal power at the receiving end. Currently, in each amplification link, in order to reduce the influence of the reflected light from the connection between the optical device and the optical fiber on the signal, two optical isolators are used in the structure to achieve the effect of reducing noise. And as a unidirectional device, the connection direction of the optical amplifier needs to be consistent with the input and output directions. However, the structures of the two isolators limit the bidirectional transmission ability of the multicast optical switch. Different from the number of optical amplifiers required by traditional telecommunication network nodes, in this invention, based on Embodiment 1, it can be optimally matched with an 8-port optical amplifier array. In the same situation, in traditional telecommunication networks, the multicast optical switch requires 2 8-port optical amplifier arrays. As an active device, the signal passing through the optical amplifier needs to conform to its signal input and output directions. The direction setting of the optical amplifier in this invention is a key point.

[0044] Therefore, based on the above-mentioned embodiments and examples, this embodiment provides a bidirectional optical amplifier array applicable to this invention, which includes M bidirectional erbium-doped fiber amplifiers. One end of each bidirectional erbium-doped fiber amplifier is connected to a splitter / coupler in one-to-one correspondence, and the other end is connected to a wavelength selection switch in the corresponding dimension. The signal amplification direction of the bidirectional erbium-doped fiber amplifier matches the signal transmission direction. The bidirectional erbium-doped fiber amplifier includes an erbium-doped fiber amplifier. Both ends of the erbium-doped fiber amplifier are respectively connected with double branches. One end of the double branches converges and is connected to the splitter / coupler, and the other end of the double branches converges and is connected to the wavelength selection switch; optical circulators are respectively arranged at the convergence points of the double branches. The bidirectional optical amplifier array also includes a power detector, a control unit, and a pump laser connected in sequence; the power detector detects the signal power on the line where the erbium-doped fiber amplifier is located; the control unit adjusts the gain of the erbium-doped fiber amplifier on this line through the pump laser according to the signal power. For the bidirectional optical amplifier array of this invention, the optical signals coming from two directions can be amplified.

[0045] This embodiment can be controlled by using two pump laser structures. Specifically:

[0046] Bidirectional optical amplifier array based on independent pumping: As Figure 4As shown, this structure enables better transient control for optical amplifiers: After the signals with bidirectional inputs enter the device, each signal path undergoes power detection so that the control unit can set the amplification structure to an appropriate gain. Subsequently, the bidirectional signals are sent to the corresponding directions by the optical circulator OC and enter the erbium-doped fiber for amplification, and the amplification gain they receive is controlled by the control platform. Each erbium-doped fiber amplifier is completely independent in terms of the control structure, and the utilization efficiency of the pump is also maximized. After the input signals are output from the corresponding output ports, this structure achieves the amplification of the signals input in both directions. In each amplification link, the presence of four optical circulators provides a large isolation degree, effectively reducing the impact of reflections at the device connections on the signals. Further, in order to minimize the impact caused by device reflections and spontaneous emission light, an additional optical isolator can be added between two optical circulators, enabling the amplification structure to provide a greater gain.

[0047] A bidirectional amplifier array with a shared pump laser providing pump power: The difference between the two lies in whether the pump laser directly provides pump power for each path. The shared pump laser uses only one high-power pump laser to provide pump power for each path in a split form. This structure requires the assistance of a fast-adjustable optical attenuator for transient control. The dedicated pump laser uses independent lasers to provide pump power and conducts transient control by directly adjusting the drive current of the pump laser. As Figure 5 shown, the difference between this structure and the independent pump array lies in its amplification part. After detecting the power of each input optical signal, the control unit controls the laser to select a suitable pump light for injection. Since a single pump laser is controlled, this amplification structure combines a fast-adjustable optical attenuator array to adjust the amplification gain of each path and conduct transient control of the amplification simultaneously. This structure will inevitably reduce the stability of the control structure, but due to the use of only a single pump laser, it is a feasible solution under cost constraints.

[0048] The bidirectional optical amplifier array in the present invention has great application value in scenarios where the amplification direction changes. Compared with the traditional optical amplifier array, this patent improves the bidirectional optical circulator array in terms of structure. Its modification cost is relatively low and it is easy to be implemented by the industrial community. After adjusting the gains of each path with the supporting control platform, this optical amplifier array can be adapted to the multicast switch.

[0049] The above-described embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A reconfigurable optical add-drop multiplexer, characterized in that: Comprising: A line-side optical processing device, including a wavelength selective switch connected to network nodes in L dimensions, where the wavelength selective switch is used to transmit or receive signals in the corresponding dimension; A client-side optical processing device, including a bidirectional optical amplifier array and a multicast optical switch. The multicast optical switch includes M 1×N port splitters / couplers and N M×1 port optical switches. The wavelength selective switch is connected to the splitter / coupler one-to-one through the bidirectional optical amplifier array; Among them, x splitters receive signals from network nodes and disperse the signals to y optical switches for selective output to the client side; N - y optical switches receive signals from the client side and select the corresponding coupler in the range of M - x for coupling output in the required transmission dimension. x is an integer less than M, and y is an integer less than N.

2. The reconfigurable optical add-drop multiplexer according to claim 1, wherein: The bidirectional optical amplifier array includes M bidirectional erbium-doped fiber amplifiers. One end of each bidirectional erbium-doped fiber amplifier is connected to the splitter / coupler one-to-one, and the other end is connected to the wavelength selective switch in the corresponding dimension. The signal amplification direction of the bidirectional erbium-doped fiber amplifier matches the signal transmission direction.

3. The reconfigurable optical add-drop multiplexer according to claim 2, wherein: The bidirectional erbium-doped fiber amplifier includes an erbium-doped fiber amplifier. Both ends of the erbium-doped fiber amplifier are respectively connected with double branches. One end of the double branches converges and connects to the splitter / coupler, and the other end of the double branches converges and connects to the wavelength selective switch; optical circulators are respectively arranged at the convergence points of the double branches.

4. The reconfigurable optical add-drop multiplexer according to claim 3, wherein: An optical isolator is arranged between the optical circulators on the same double branch.

5. The reconfigurable optical add-drop multiplexer according to claim 3, characterized in that: The bidirectional optical amplifier array further includes a power detector, a control unit, and a pump laser connected in sequence; The power detector detects the signal power on the line where the erbium-doped fiber amplifier is located; The control unit adjusts the gain of the erbium-doped fiber amplifier on this line through the pump laser according to the signal power.

6. The reconfigurable optical add-drop multiplexer according to claim 5, characterized in that: The pump laser adopts an independent pump laser array or a shared pump laser; when the pump laser adopts an independent pump laser array, the independent pump laser array controls each erbium-doped fiber amplifier separately; when the pump laser adopts a shared pump laser, the pump laser is connected to each erbium-doped fiber amplifier through a fast adjustable optical attenuation array for selective control.

7. The reconfigurable optical add-drop multiplexer according to claim 1, characterized in that: An adjustable filter is arranged at one end of the optical switch for output to the client side.

8. The reconfigurable optical add-drop multiplexer according to claim 1, characterized in that: M is equal to 8, N is equal to 16, and L is less than or equal to 4.

9. The reconfigurable optical add-drop multiplexer according to claim 8, wherein: x is equal to 4, and y is less than or equal to 16.

10. A reconfigurable optical add-drop multiplexer according to any one of claims 1-9, characterized in that: Two wavelength selective switches are arranged on the network nodes in each dimension. One of the wavelength selective switches is used to transmit the signals of the network nodes in this dimension to the multicast optical switch, and the other wavelength selective switch is used to receive the client-side signals from the multicast optical switch.

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