CN103686465B - Optical network node, optical network unit and communicating between the optical network unit of low delay - Google Patents

Abstract

The invention provides an optical network node, which includes an optical splitter, a controller, two electro-optical switches and two circulators. The optical splitter is used to divide the downlink signal into two paths and provide them to the controller and each optical network unit respectively. The circulator is used to separate the uplink signal from the downlink signal. The controller is used to receive the control signal from the optical line terminal and control the routing function of the electro-optic switch. Electro-optic switches are used to provide routing functions based on control signals. An optical network unit is also provided, including a first receiver for receiving downlink signals, a second receiver for receiving local transmission signals from other optical network units, and a transmitter for sending uplink signals to optical line terminals and sending local transmission signals to other The optical network unit, the switching element is respectively connected to the second receiver and the transmitter for controlling the signal reception of the second receiver and the signal transmission of the transmitter. It also provides a communication mechanism between optical network units with low delay and controllable by the optical line terminal.

Description

Communication among optical network nodes, optical network units and low-latency optical network units

technical field

The present application relates to an optical network, in particular to an optical network node, an optical network unit, and communication between optical network units with low delay in the optical network.

Background technique

In the traditional passive optical network (PON) structure, the routing processing at the optical line terminal (OLT) and the propagation delay caused by the long fiber length make the optical network unit (ONU) Network interconnections (ie, base station-to-base station communications) suffer from severe latency problems. For strict end-to-end latency requirements (eg, less than 30ms), such delays are undesirable. In addition, this also greatly wastes the downlink bandwidth and the processing capability of the optical line terminal.

Therefore, in future passive optical networks, especially when realizing cooperative multi-point transmission between optical network units, low-latency network interconnection functions are crucial.

At present, various structures have been proposed for realizing network interconnection among optical network units. Although it is possible to allocate additional wavelengths for local communication, this requires at least two transmitters with different wavelengths, so the simplest solution is to use time division multiplexing (TDM). In the TDM-PON structure, a typical solution is based on a fiber Bragg grating (fiber Bragg grating, FBG), a switch in an optical network unit, and a star coupler.

Contents of the invention

Through research on most of the existing solutions, the inventors of the present application found that these existing solutions usually use star couplers in the optical distribution network (ODN) and modify the optical distribution network by adding passive devices . However, these purely passive devices cannot provide routing functions in local communication, and the entire optical access network also lacks an optical line terminal control mechanism.

Therefore, it is very advantageous to provide a communication mechanism between optical network units controllable by an optical line terminal.

According to the first aspect of the present invention, an optical network node is provided, which includes a first optical splitter, a first circulator, a second circulator, a controller, a first electro-optical switch and a second electro-optical switch, wherein the A first optical splitter configured to split a downlink signal from an optical line terminal into a first downlink signal and a second downlink signal, and provide the first downlink signal to the controller and the The second downlink signal is provided to the first circulator, wherein the power of the first downlink signal is less than the power of the second downlink signal and the first downlink signal and the second downlink signal include A control signal; the controller, configured to receive the first downlink signal from the first optical splitter, and control the first electro-optical signal according to the control signal in the first downlink signal A switch provides a routing function and controls the second electro-optic switch to provide a routing function; the first electro-optic switch is configured to provide a routing function according to the control signal of the controller; the first circulator is configured to configured to provide the second downlink signal from the first optical splitter to the second circulator, and configured to provide data from the second electro-optical switch to the optical line terminal; the The second circulator is configured to provide the second downlink signal from the first circulator to each optical network unit, and is configured to provide the uplink signal and the local transmission signal from the optical network unit to The second electro-optical switch, wherein the control signal in the second downlink signal is used to inform each optical network unit of the opening/closing time of the first electro-optical switch; and the second electro-optical switch, It is configured to provide the uplink signal to the first circulator on a first time slot and provide the local transmission signal to the first electro-optic signal on a second time slot according to the control of the controller. switch.

According to a second aspect of the present invention, an optical network unit is provided, comprising: a first receiver configured to receive downlink signals from an optical line terminal; a second receiver configured to receive signals from other optical networks a local transmission signal of the unit; a transmitter configured to send an uplink signal to the optical line terminal and to send a local transmission signal to other optical network units; and a switching element connected to the second receiver and the a transmitter and is configured to control signal reception by the second receiver and signal transmission by the transmitter.

According to a third aspect of the present invention, there is provided a method for bandwidth request for communication between multiple optical network units in an optical network unit of an optical network, the optical network including an optical line terminal, according to the first aspect above The optical network node and the plurality of optical network units, wherein the method includes the following steps: sending bandwidth request information to the optical line terminal; and receiving a control signal from the optical line terminal, wherein the control The signal is included in a downlink signal sent from the OLT to the ONU, and the control signal is used to inform the ONU of the opening/closing time of the first electro-optical switch in the ONU.

According to a fourth aspect of the present invention, there is provided a method for allocating bandwidth for communication among multiple optical network units in an optical line terminal of an optical network, the optical network comprising The optical line terminal, the optical network node and the plurality of optical network units according to the first aspect above, wherein the method includes the following steps: receiving bandwidth request information from each optical network unit; according to the bandwidth request information, for assigning time slots to each optical network unit; and generating a control signal according to the assigned time slot to each optical network unit and sending the control signal to each optical network unit and a controller in the optical network node, wherein the The control signal is included in the downlink signal sent by the local OLT to each ONU, and the control signal is used to inform each ONU of the opening/closing time of the first electro-optical switch in the ONU.

The solution of the present invention can reduce delay to ensure real-time transmission between optical network units. In addition, since the routing function is controlled by the optical line terminal, compared with the direct communication between the optical network units based on the star coupler in the prior art, the optical network unit in the present invention is easy to manage.

Various aspects of the present invention will be clarified through the description of specific embodiments below.

Description of drawings

These and other features of the present invention will become clearer by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

FIG. 1 shows a schematic diagram of an optical network including optical network nodes according to an embodiment of the present invention;

FIG. 2 shows a schematic structural diagram of an optical network unit according to an embodiment of the present invention;

FIG. 3 shows a schematic diagram of a downlink frame for downlink communication according to an embodiment of the present invention; and

Fig. 4 shows a schematic diagram of an uplink frame and a local communication frame used for uplink communication and local communication among optical network units according to an embodiment of the present invention.

The same or similar reference signs in the drawings indicate the same or similar components.

detailed description

In order to realize the communication between optical network units with low delay and controllable by optical line terminals, an optical network node is introduced in the embodiments of the present invention.

Referring to FIG. 1 , an optical network node 10 has a first optical splitter 11 , a controller 12 , a first electro-optic switch 13 , a first circulator 14 , a second circulator 15 , and a second electro-optic switch 16 and an optical amplifier 17 . Wherein, the controller 12 , the first electro-optic switch 13 , the second electro-optic switch 16 and the optical amplifier 17 are located in the controllable active box of the optical line terminal 20 . The first circulator 14 and the second circulator 15 are used to separate the downlink signal from the uplink signal, thereby ensuring signal transmission in uplink and downlink directions.

Specifically, the first optical splitter 11 is configured to split the downlink signal from the optical line terminal 20 into two downlink signals, that is, a first downlink signal and a second downlink signal, and provide the first downlink signal to the controller 12 and provide the second downlink signal to the first circulator 14 . The first downlink signal and the second downlink signal include control signals.

The power of the first downlink signal is smaller than the power of the second downlink signal. Advantageously, in order to ensure the power budget (power budget) of the downlink, the light splitting ratio of the first optical splitter 11 can be set to 5:95 or 1:99, based on this, the first downlink signal transmitted to the controller 12 is relatively Weak, the second downlink signal transmitted to the first circulator 14 has a power penalty of less than 0.5 dB.

The controller 12 is configured to receive the first downlink signal from the first optical splitter 11, and control the first electro-optical switch 13 to provide a routing function according to a control signal in the first downlink signal. Since the first downlink signal obtained by the controller 12 from the first optical splitter 11 is an optical signal, the controller 12 first converts the optical control signal in the first downlink signal into an electrical control signal, and then according to the electrical control The signal controls the first electro-optical switch 13 to provide a routing function for communication between the various optical network units 30 . Specifically, the controller 12 can store the electrical control signal and convert it into a suitable control voltage waveform, and the routing algorithm of the first electro-optic switch 13 corresponds to different control voltage waveforms.

The controller 12 is also configured to control the second electro-optic switch 16 to provide a routing function.

The first electro-optical switch 13 is configured to provide a routing function according to a control signal of the controller 12 . Specifically, the first electro-optic switch 13 is used to determine a data transmission path between optical network units. Since the multicast and broadcast functions can be easily implemented at the first electro-optical switch 13, one ONU can also transmit data to multiple other ONUs at the same time.

The first circulator 14 is configured to provide the second downlink signal from the first optical splitter 11 to the second circulator 15 , and is configured to provide data from the second electro-optical switch 16 to the optical line terminal 20 . Specifically, as shown in Figure 1, the second downlink signal from the first optical splitter 11 enters from the B port of the first circulator 14 and exits from the C port, and the data from the second electro-optical switch 16 passes through the first circulator 14. Port A enters port B and exits.

The second circulator 15 is configured to provide the second downlink signal from the first circulator 14 to each optical network unit 30 respectively, and each network unit 30 can know the The opening/closing time of the switches connected to the respective optical network units in the first electro-optical switch 13 of . The second circulator 15 is also configured to provide the uplink signal for uplink transmission from the ONU 30 and the local transmission signal for inter-ONU transmission to the second electro-optic switch 16 . Specifically, as shown in FIG. 1, the second downlink signal from the first circulator 14 enters through port A of the second circulator 15 and exits through port B, and the uplink signal and the local transmission signal from the optical network unit pass through the second circulator 15. Port B of the second circulator 15 enters Port C and exits.

It should be understood that the wavelength of the uplink signal is the same as that of the local transmission signal, while the wavelength of the downlink signal is different from the wavelength of the uplink signal.

The optical amplifier 17 is configured to amplify the uplink signal and the local transmission signal from the second circulator 15 and provide them to the second electro-optical switch 16 . It should be noted that, considering the degree of attenuation of the optical signal, the optical amplifier 17 is an optional component.

The second electro-optic switch 16 is configured to provide the uplink signal to the first circulator 14 for uplink transmission on the first time slot and provide the first electro-optic signal to the local transmission signal on the second time slot according to the control of the controller 12. The switch 16 is used for signal transmission between optical network units.

Since the traditional ONU has only one receiver, it cannot meet the requirement of simultaneously receiving downlink signals from the OLT and local transmission signals from other ONUs. Based on this, embodiments of the present invention provide a new structure of an optical network unit.

Referring to FIG. 2 , the ONU 30 includes a first receiver 31 , a second receiver 32 , a transmitter 33 and a switching element 34 .

The first receiver 31 is configured to receive downlink signals from the OLT 20 .

The second receiver 32 is configured to receive local transmission signals from other ONUs.

The transmitter 33 is configured to send uplink signals to the OLT 20 and send local transmission signals to other ONUs.

The switching element 34 is respectively connected to the second receiver 32 and the transmitter 33 and is configured to control signal reception of the second receiver 32 and signal transmission of the transmitter 33 . When the transmitter 33 needs to send a signal, the switch connected to the transmitter 33 in the switch element 34 is controlled to be closed; The switch connected to the device 32 is controlled to be closed.

When the transmitter 33 is working, since the ONU does not send data to itself, the second receiver 32 does not need to receive data. When the second receiver 32 is working, the local communication of the transmitter 33 is disabled because the time slot belongs to other ONUs.

It should be noted that although two receivers are shown in FIG. 2 , in practical applications, some data processing modules of the two receivers may be shared.

In another embodiment, the switching element 34 can also be replaced by an optical splitter.

Since an optical network node is introduced into the optical network of the present invention and the structure of the optical network unit has changed, the function of the operating wavelength (operating wavelength) of the optical network of the present invention is different from that of the existing optical network, wherein the wavelength λ ₁ is used for downlink communication, while wavelength λ ₂ is used for uplink communication and local communication on different time slots.

The basic structure of the downlink frame remains unchanged, only a new frame is added to carry the control signal provided to the controller 12 . The transmission structure of the downlink frame is as shown in Figure 3, wherein, the frame shown in the shaded part carries the control signal for controlling the first electro-optic switch 13 (that is, the working rules of the first electro-optic switch 13), which are respectively sent to The controller 12 and each optical network unit 30 . The downlink frames sent to the ONUs transmit data as in the prior art, while the uplink frames and local communication frames can be used to transmit data only after each ONU 30 knows the working rule of the first EO switch 13 . The interval length between frames shown by two adjacent shaded parts is determined by the optical line terminal 20 .

In order to ensure uplink communication and local communication, an uplink frame and a local communication frame as shown in FIG. 4 are adopted. Specifically, the frames with a wavelength of λ2 are divided into _two categories: one class is an uplink frame, used for uplink communication from the ONU 30 to the OLT 20; the other is a local communication frame, used between ONUs local communication. The allocation of time slots for uplink communication and local communication is controlled by the optical line terminal 20, and the time slot allocation information is sent to the controller 12 and each optical network unit 30 through frames shown in shaded parts in FIG. 3 .

Local communication between optical network units controllable by optical line terminals can ensure that any optical network unit can directly send data to other optical network units. However, special design of local communication frames is required to meet low-latency requirements. For example, the end-to-end delay time in the X2 interface of the evolved nodes (eNBs) of the LTE system is less than 1 ms in some cases, which does not leave enough time for ONU requests and OLT processing. Therefore, as shown in FIG. 4 , a time division multiplex (TDM) mini frame (mini frame) is used for local communication between optical network units instead of an upstream burst frame (upstream burst frame). The maximum number of these mini-frames is determined by the length of the mini-frame, and the usual frame length is, for example, 0.125ms.

In order to avoid the conflict between the former data packet and the latter data packet, some guard time should be included in the switching time (switching time) reserved for the optical network unit, and the value of the guard time is determined by the different distances between each optical network unit to make sure. Assuming that the distance gap is 1km, then the length of the mini-frame is about 5ms. If the effective ONU transmission time is 6.36ms, then the mini-frame length is 11.36μs, therefore, the traditional frame length can transmit 11 mini-frames, which can support real-time local transmission between 16 to 32 ONUs , the end-to-end delay is as low as 0.5-1ms. .

Each ONU is assigned a time slot to transmit its mini-frame to the destination, which is controlled by the first electro-optical switch 13, since the mini-frame in each time slot is always routed to the adjacent ONU , so this information is usually fixed.

The specific structure of the mini-frame can be referred to as shown in FIG. 4 , which includes guard time, header, payload and parity. The header includes physical layer synchronization information. Checksums are used by decoders to detect and correct certain transmission errors. Assuming that the load occupies 50% of the transmission time of the mini-frame, the length of the bit stream is determined by the bit rate of the wavelength _λ2 , if the bit rate is 10Gbit/s, then the length of the load is about 7102 bytes.

The control mechanism of the optical network of the present invention is executed by the optical line terminal. It is assumed that the OLT and all ONUs have a proper synchronization relationship. Considering the low latency in eNodeB CoMP system (ONU-ONU) with mobile backhaul function (ONU-OLT), the control mechanism is as follows:

Bandwidth request and allocation for local communication between multiple optical network units

Firstly, each ONU 30 sends bandwidth request information to the OLT 20 respectively. For example, the bandwidth request information may be filled in the PLOAM channel of the uplink frame for transmission.

After receiving the bandwidth request information from each optical network unit 30, the optical line terminal 20 allocates time slots for each optical network unit according to the bandwidth request information, and generates routing information according to the allocated time slots (that is, the above control signal). Then, the control signal is sent to each ONU 30 and the controller 12 in the ONU 10 . For example, the control signal may be encapsulated in a downlink frame and transmitted to each ONU 30 and controller 12 . The controller 12 controls the first electro-optical switch 13 to provide a routing function according to the control signal in the downlink frame. According to the control signal in the downlink frame, each optical network unit 30 can know the opening/closing time of the switch connected to each optical network unit in the first electro-optical switch 13 in the optical network node 10 .

The controller selects the routing path

When the controller 12 receives the control signal, it decodes the control signal and sends a suitable voltage waveform to the first electro-optic switch 13 . Therefore, each ONU is able to send data to different destinations in its own time slot.

The ONU sends data on its assigned mini-frame

Once the routing path is established, the ONU can send data to any other ONU in its assigned time slot and the process is secure. This process can continue for a while until new time slots are allocated to each ONU.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be regarded as exemplary and not restrictive from all points of view, and any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the word "a" preceding an element does not exclude the inclusion of "plurality" of such elements. Multiple elements stated in a product claim may also be realized by one element through software or hardware. The words first, second, etc. are used to denote names and do not imply any particular order.

Claims (8)

1. An optical network node comprising a first optical splitter, a first circulator, a second circulator, a controller, a first electro-optical switch and a second electro-optical switch, wherein, The first optical splitter is configured to split the downlink signal from the optical line terminal into a first downlink signal and a second downlink signal, and provide the first downlink signal to the controller and The second downlink signal is provided to the first circulator, wherein the power of the first downlink signal is less than the power of the second downlink signal and the first downlink signal and the second downlink signal including control signals; The controller is configured to receive the first downlink signal from the first optical splitter, and control the first electro-optic switch to provide routing according to the control signal in the first downlink signal function and control the second electro-optic switch to provide a routing function; the first electro-optic switch configured to provide a routing function according to the control signal of the controller; the first circulator, which is configured to provide the second downlink signal from the first optical splitter to the second circulator, and is configured to provide the data from the second electro-optic switch to to said optical line terminal; The second circulator is configured to provide the second downlink signal from the first circulator to each optical network unit, and is configured to provide the uplink signal and the local transmission signal from the optical network unit Provided to the second electro-optical switch, wherein the control signal in the second downlink signal is used to inform each optical network unit of the opening/closing time of the first electro-optical switch; The second electro-optical switch is configured to provide the uplink signal to the first circulator in the first time slot and transmit the local transmission signal in the second time slot according to the control of the controller. A signal is provided to the first electro-optic switch. 2. The optical network node according to claim 1, wherein the optical network node further comprises: an optical amplifier, which is arranged between the second circulator and the second electro-optical switch, and is configured to amplify the uplink signal and the local transmission signal from the second circulator and provide them to The second electro-optic switch. 3. The optical network node according to claim 1, wherein the controller is further configured to convert the optical control signal in the first downlink signal into an electrical control signal, and A signal controlling the first electro-optic switch provides a routing function. 4. The optical network node according to claim 1, wherein the light splitting ratio of the first optical splitter is 5:95 or 1:99. 5. The optical network node according to claim 1, wherein the wavelength of the downlink signal is different from the wavelength of the uplink signal, and the wavelength of the uplink signal is the same as the wavelength of the local transmission signal. 6. An optical network unit, comprising: a first receiver configured to receive a downlink signal from an optical line terminal; a second receiver configured to receive locally transmitted signals from other optical network units; a transmitter configured to send uplink signals to the OLT and send local transmission signals to other ONUs; switching elements connected to the second receiver and the transmitter, respectively, and configured to control signal reception by the second receiver and signal transmission by the transmitter. 7. A method for bandwidth request for communication between a plurality of optical network units in an optical network unit of an optical network, the optical network comprising an optical line terminal, an optical network node according to claim 1, and the A plurality of optical network units, wherein the method includes the following steps: - sending bandwidth request information to said optical line terminal; - receiving a control signal from the optical line terminal, wherein the control signal is included in the downlink signal sent from the optical line terminal to the optical network unit, and the control signal is used to inform the optical network unit of the The opening/closing time of the first electro-optical switch in the optical network node. 8. A method for allocating bandwidth for communication between a plurality of optical network units in an optical line terminal of an optical network, said optical network comprising an optical line terminal, according to claim 1 The optical network node and the plurality of optical network units, wherein the method includes the following steps: - receiving bandwidth request information from each optical network unit; - allocating time slots to each optical network unit according to the bandwidth request information; - generating and sending a control signal to each optical network unit and a controller in the optical network node according to the time slot allocated for each optical network unit, wherein the control signal is located at the optical line terminal The downlink signal is sent to each optical network unit, and the control signal is used to inform each optical network unit of the opening/closing time of the first electro-optical switch in the optical network node.