CN1889405A - Optical splitter and passive optical network loop system - Google Patents

Abstract

The invention discloses a light splitting device and a passive optical network loop system, which are used to solve the problem that an optical coupler and a dual-port optical network unit must be used in a passive optical network loop with an automatic protection switching function in the prior art question. The passive optical network loop system includes logically independent two optical line terminals, one active and one standby, several optical network units, and several optical splitting devices with bidirectional optical splitting function corresponding to the optical network units one by one; logically independent The two optical line terminals and several optical splitting devices are connected to form a ring through optical fibers, and the optical splitting devices and optical network units are correspondingly connected through optical fibers. When the light splitting device is used to connect the optical network unit to the passive optical network loop system, there is no limit to the number of ports of the optical network unit, so that the passive optical network loop can be connected to more end users at the same time.

Description

Optical splitting device and passive optical network loop system

technical field

The invention relates to a passive optical network networking technology, in particular to a light splitting device and a passive optical network loop system.

Background technique

In the increasingly large-scale broadband access network, most of the existing local area networks run on the 100Mbit/s network, and many large-scale commercial companies are transitioning to Gigabit Ethernet. At present, the bandwidth capacity of the core network of the metropolitan area and the edge network of the metropolitan area is very abundant, which causes a serious bandwidth bottleneck in the access network. Compared with cable transmission, optical fiber transmission has the advantages of large capacity, low loss, and strong anti-electromagnetic interference capability. Therefore, as the cost of optical fiber transmission gradually decreases, the development of optical fiber in the access network is an inevitable development trend.

PON (Passive Optical Network, Passive Optical Network) is a pure media network that inserts passive optical devices into the network. The transmitted traffic is guided by separating the power of the optical wavelength, thereby effectively avoiding the influence of electromagnetic interference and lightning on external devices, and improving the reliability of the communication system. Passive optical splitters and couplers only function to transmit and limit light, do not require power supply and information processing, and have unlimited mean time between failures, which can comprehensively reduce maintenance costs for service providers. Due to the increase in bandwidth demand of end users and the sharp drop in the price of optical devices, PON has gradually become a long-term solution for optical access networks.

The PON networking mode in the prior art mainly adopts a tree topology or a ring topology.

Figure 1 shows a schematic diagram of the structure of a tree-type PON. The PON consists of an OLT (Optical Line Terminal, Optical Line Terminal) located in the service exchange, several ONUs (Optical Network Unit, Optical Network Unit) located in the user premises, and ODN ( Optical Distribution Network, optical distribution network), in which the OLT is connected to several ONUs through the ODN, and the ODN is composed of optical fibers, optical splitters or optical couplers. In order to improve the reliability and stability of PON, there are two main types of optical fiber protection switching methods used in PON with tree topology: one is backbone optical fiber protection switching, and the other is full protection switching, which are described below. .

FIG. 2 is a schematic diagram of a tree-type PON adopting a backbone optical fiber protection switching mode. It can be seen from the figure that the tree-type PON adopting the backbone optical fiber protection switching mode uses a backup optical fiber on the backbone line between the OLT and the optical splitter, and can automatically perform automatic switching when the optical fiber between the OLT and the optical splitter fails. Protection switching, but the failure of the optical fiber between the optical splitter and the ONU cannot be protected, so it cannot adapt to the environment with high protection requirements for PON.

FIG. 3 is a schematic diagram of a tree-type PON adopting a full-protection switching mode. It can be seen from the figure that the tree-type PON in the full protection switching mode is fully redundant from the OLT to the ONU, and has two sets of optical splitters. This full protection method actually uses two sets of PONs, one master and one backup, to solve the redundancy problem of each node. When the master PON fails, it automatically switches to the backup PON for optical transmission. The PON with full protection switch mode The used optical fibers and optical splitters are multiplied, which leads to the multiplied increase of the cost of the PON.

The routing strategy of ring PON is very simple, the control and management of network resources is relatively easy, and when the optical fiber of the PON ring is cut or the network node fails, it can be protected in a simple way, fast and reliable. Figure 4 is a schematic structural diagram of a PON loop with automatic protection switching function. The PON mainly includes two OLTs, several dual-port ONUs, and several 2×2 optical couplers. Communication between the two OLTs is possible. The OLT and multiple 2×2 optical couplers are connected to form a ring through optical fibers, and the 2×2 optical couplers are correspondingly connected to the ONU through optical fibers. The 2×2 optical coupler has four ports, and the two ports of the ONU are respectively connected to two of the four ports of the 2×2 optical coupler. The ONU connected to the PON ring through a 2×2 optical coupler can have two working modes, one is for one port to work and the other is for port monitoring, that is, one port works in any OLT subsystem, and the other port is a standby port; The other is that two ports work in a load sharing manner, that is, each port works in an OLT subsystem. Each ONU port corresponds to one interface of the OLT, and each port of the ONU cannot be optically connected to two ports of the OLT at the same time.

Figure 5 is a schematic diagram of automatic protection switching when a single-point break occurs in the PON loop. Before a single-point break occurs in the optical fiber, ONU1-ONU6 adopts the working mode of one port working and one port monitoring, in which ONU1, ONU2, and ONU3 work on OLT1 In the subsystem, ONU4, ONU5, and ONU6 work in the OLT2 subsystem. Assume that the fiber break point occurs between ONU1 and ONU2. The communication interrupted by the OLT1 subsystem, since ONU2 and ONU3 have two ports, can use the spare port to automatically switch to the OLT2 subsystem to continue running, and then the automatic protection switching can be completed. In this kind of PON loop, an optical coupler and an ONU with dual ports must be used, otherwise automatic protection switching cannot be performed, and each port of the dual-port ONU corresponds to an interface of the OLT, and each port of the ONU cannot be connected to the OLT at the same time. The two ports are optically connected. Since the dual-port ONU has only two line terminal (LT) modules inside, the number of end users it can access is limited.

Contents of the invention

The invention provides an optical splitting device and a passive optical network loop system to solve the problem in the prior art that an optical coupler and a dual-port optical network unit must be used in a passive optical network loop with an automatic protection switching function .

The present invention adopts following technical scheme:

An optical splitting device used in a passive optical network loop; its structure is composed of two 1:N+1 type optical splitters and N 1:2 type optical splitters, one of which is 1:N+1 One branch end of a 1:N+1 type optical splitter is connected to one branch end of another 1:N+1 type optical splitter, and the remaining branch ends of each 1:N+1 type optical splitter are respectively connected to One branch end connection of each 1:2 optical splitter.

The trunk ends of the N 1:2 type optical splitters and the trunk ends of the two 1:N+1 type optical splitters constitute the N+2 external ports of the optical splitter.

A passive optical network loop system, including logically independent two optical line terminals, one active and one standby, and several optical network units; Device; two logically independent optical line terminals and several optical splitting devices are connected to form a ring through optical fibers, and the optical splitting devices and optical network units are correspondingly connected through optical fibers.

The two logically independent optical line terminals are composed of one optical line terminal physical device with two line terminal modules inside, or two optical line terminals with one line terminal module inside respectively. The two logically independent optical line terminals have respectively established optical connections with all ports of each optical network unit in the ring.

The optical network unit is an N-port optical network unit with N line terminal modules inside, and the value of N is an integer greater than or equal to 1. The optical splitting device connected to the N-port ONU has N+2 ports, wherein N ports are used to connect the N-port ONU, and the other two ports are used to connect the N-port ONU to the passive optical network loop.

The optical splitting device with N+2 ports is composed of two 1:N+1 type optical splitters and N 1:2 type optical splitters, wherein one of the 1:N+1 type optical splitters One branch end is connected to one branch end of another 1:N+1 type optical splitter, and the remaining branch ends of each 1:N+1 type optical splitter are respectively connected to each 1:2 type optical splitter One branch end of the optical splitter is connected. The N ports that are used to connect the optical network unit in the optical splitting device are respectively the backbone ends of N 1:2 type optical splitters; the optical splitting device is used to connect the optical network unit to the passive optical network loop The two ports are respectively the backbone ends of two 1:N+1 optical splitters.

A passive optical network loop protection method, the passive optical network loop includes two optical line terminals, one active and one standby, and several optical network units, and the optical network units are connected to the loop with two The optical line terminals respectively establish optical connections; including steps:

A. The optical network unit in the loop performs optical communication with the main optical line terminal through its own working port, and the standby optical line terminal is in a standby state;

B. When the optical fiber of the passive optical network loop is disconnected, the standby optical line terminal is switched from the standby state to the working state; the optical network unit that maintains an optical connection with the main optical line terminal continues to communicate with the main optical line terminal through its own working port. The line terminal performs optical communication; the optical network unit maintaining the optical connection with the standby optical network unit switches the working port to perform optical communication with the standby optical network unit.

The optical network unit is an N-port optical network unit with N line terminal modules inside, and the value of N is an integer greater than or equal to 1.

When N is equal to 1, all the N ports of the ONU are working ports, and when a working port of the ONU fails, the ONU is offline.

When the value of N is an integer greater than 1, all or some of the N ports of the optical network unit are working ports, and the remaining ports are standby ports. When the working port of the optical network unit fails, the optical signal flow borne by the faulty port will be switched to other ports in the normal state of the optical network unit. The port is the working port for load sharing.

The present invention adopts the above technical scheme, and has the following beneficial effects:

The light splitting device with bidirectional light splitting function of the present invention is composed of two 1:N+1 type optical splitters and N 1:2 type optical splitters, and the optical network unit is connected to the passive optical network by using the light splitting device In the loop system, there is no limit to the number of ports of the optical network unit, so that the passive optical network loop can access more end users at the same time.

Description of drawings

FIG. 1 is a schematic structural diagram of a tree-type PON in the prior art;

FIG. 2 is a schematic diagram of a tree-type PON adopting a backbone optical fiber protection switching mode in the prior art;

FIG. 3 is a schematic diagram of a tree-type PON adopting a full protection switching mode in the prior art;

FIG. 4 is a schematic structural diagram of a PON loop with an automatic protection switching function in the prior art;

FIG. 5 is a schematic diagram of automatic protection switching when a single point break occurs in the PON loop in the prior art;

Fig. 6 is a schematic structural diagram of the PON loop system of the present invention;

FIG. 7 is a schematic structural view of an optical splitting device with N+2 ports of the present invention;

FIG. 8 is a schematic structural view of a light splitting device with three ports of the present invention;

9 is a schematic structural view of a light splitting device with four ports of the present invention;

10A and 10B are schematic diagrams of a single-point disconnection fault occurring in the PON loop fiber of the present invention;

FIG. 11 is a flow chart of automatic protection switching when the currently working port of the ONU fails in the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Fig. 6 shows the structural schematic diagram of the PON loop system of the present invention, and its structure is mainly composed of logically independent two OLTs, several ONUs, several optical splitting devices with bidirectional optical splitting functions corresponding to the ONUs one-to-one, and surrounded by rings. In this PON loop system, two logically independent OLTs are connected to each other and can communicate. The OLT and several optical splitting devices are sequentially connected to form a ring through optical fibers. The optical splitting device and the ONU Corresponding connection via optical fiber. The two logically independent OLTs may be one OLT physical device with two line terminal modules inside, or two OLT physical devices with one line terminal module inside each.

The PON loop system of the present invention has no limit to the number of ports of the connected ONU, and can be connected to either a single-port ONU or a multi-port ONU. When the PON loop is connected to an ONU with N ports, the optical splitting device connected to the ONU should have N+2 ports, two of which are used to connect the ONU to the PON loop, and the remaining N ports are used for It is connected to the N ports of the ONU one by one.

Figure 7 is a schematic structural diagram of an optical splitting device with N+2 ports, the optical splitting device can work normally in at least two wavelength windows, at least one wavelength is used to transmit uplink data, and at least one wavelength is used to transmit downlink data. It can be seen from the figure that the splitting device is composed of two 1:N+1 type optical splitters and N 1:2 type optical splitters, one branch of one 1:N+1 type optical splitter The end of each 1:N+1 type optical splitter is connected to one branch end of another 1:N+1 type optical splitter, and the remaining branch end of each 1:N+1 type optical splitter is connected to each 1:2 type optical splitter A branch end connection of the device. Among the N+2 ports of the optical splitting device, the two ports P ₁ and P ₂ used to connect the ONU to the PON loop are respectively the trunk ends of two 1:N+1 optical splitters for connecting The N ports P ₃ -P _N+2 of the ONU are respectively the backbone ends of the N 1:2 optical splitters. On the 1:N+1 type optical splitter, the splitting ratio of the output optical signal at the branch end can be set. When the P ₁ port receives the downlink optical signal sent by the OLT, the P ₂ -P _N+2 port follows the setting output optical signal according to the ratio; when the P ₂ port receives the downlink optical signal sent by the OLT, the P ₁ port and the P ₃ -P _N+2 port output the optical signal according to the set ratio. Generally, it should be between two 1 : Set the same splitting ratio on the N+1 optical splitter. And when any port in P ₃ -P _N+2 receives the upstream optical signal sent by the ONU, the port P ₁ and the port P ₂ each output 50% of the optical signal.

In actual networking, single-port ONU or dual-port ONU is often used. The optical splitting device used to connect single-port ONU should have three ports, and the optical splitting device used to connect dual-port ONU should have four ports. The structure of a splitting device with one port and a splitting device with four ports will be described.

As shown in Figure 8, the optical splitting device with three ports is composed of three 1:2 type optical splitters, the trunk ends of the three 1:2 type optical splitters are respectively the three ports of the optical splitting device, these three There is no distinction between primary and secondary ports, all of which can send and receive optical signals. Any one of the ports can be connected to the port of a single-port ONU, and the other two ports can be connected to the PON loop.

As shown in Figure 9, the four-port optical splitter is composed of two 1:2 type optical splitters and two 1:3 type optical splitters, and the trunk ends of the two 1:3 optical splitters are respectively 1 : The two ports of the 3-type bidirectional optical splitter are used to access the PON loop, and the trunk ends of the two 1:2 optical splitters are respectively used for the two ports of the 1:3 type bidirectional optical splitter and the dual-port ONU. two ports connected to each other. These four ports can all send and receive optical signals.

When the PON loop works normally, for two logically independent OLTs, only one OLT is working, and the other OLT is in standby state. As shown in Figure 6, in this PON loop, the two logically independent OLTs are an OLT physical device with two line terminal modules inside. One line terminal module of the OLT physical device is in working state, and the other line terminal module is The terminal module is in standby standby. Among them, the single-port ONU1 is connected to the PON loop through a three-port optical splitting device, the dual-port ONU2 and ONU3 are respectively connected to the PON ring through a four-port optical splitting device, and the three-port ONU4 is connected to a five-port optical splitting device. Access to the PON loop. For ONUs with multiple ports, such as ONU2, ONU3 and ONU4 in the figure, multiple line terminal modules inside each ONU can have two working modes: one is the load sharing mode for multiple line terminal modules , that is, all line terminal modules inside the ONU must work; the other is that some of the multiple line terminal modules are in the working state, and the other part is in the standby state. Generally, the number of modules in the standby state should be less than or equal to The number of modules in working state.

When the PON loop shown in Figure 6 is in the normal working state, LT1 in the OLT is in the working state, LT2 is in the standby state, the flow direction of the downlink optical signal sent by the OLT is clockwise, and the LT1 and LT2 in the ONU2 carry out the load Work sharing; LT1 in ONU3 works, LT2 is in standby; LT1 and LT2 in ONU4 work, and LT3 is in standby. At this time, if the backbone optical fiber currently in use in the PON loop has a single-point disconnection fault, as shown in Figure 10A, the LT2 will automatically switch from the standby standby state to the working state, and the flow direction of the downlink optical signal sent by the OLT will change from clockwise to counterclockwise. If a single-point disconnection fault occurs on the user-side optical fiber of the PON loop, as shown in Figure 10B, at this time, any optical signal sent by any line terminal module inside the OLT cannot reach all the ONUs on the PON loop. In this case, LT1 and LT2 inside the OLT work at the same time, ONU1, ONU2 and ONU3 receive the optical signal sent by LT1, and ONU4 and ONU5 receive the optical signal sent by LT2, respectively forming two independent tree-type PON networks.

In the PON loop of the present invention, if the working OLT among the logically independent two independent OLTs breaks down, the standby OLT automatically turns to the working state and sends a light signal to the ONU in the PON loop.

As shown in Figure 11, when the current working port of the ONU fails, there are two reasons for the failure. One is that the current working line terminal module inside the ONU has a failure, and the other is that the current working port in the ONU is connected to the The optical fiber between the light splitting devices is broken. In this case, the process of automatic protection switching of the PON loop of the present invention is as follows:

Step S10, when ONU is working normally, judge in real time whether the status of the currently working port is normal, if the currently working port fails, then proceed to step S11, otherwise, the ONU continues to work normally;

Step S11, determine whether the ONU is a single-port ONU, if so, the ONU is off-line, otherwise proceed to step S12;

Step S12, switch the optical signal flow borne by the failed port in the ONU to other ports that are not disconnected. The other ports that are not disconnected can be backup ports, or ports that share the load with the failed port.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (15)

1, a kind of light-dividing device is used for the EPON loop; It is characterized in that, its structure is made of two 1:N+1 type optical branching devices and N 1:2 type optical branching device, a Zhi Luduan of one of them 1:N+1 type optical branching device is connected with a Zhi Luduan of another 1:N+1 type optical branching device, and the residue Zhi Luduan of each 1:N+1 type optical branching device is connected with a Zhi Luduan of each 1:2 type optical branching device respectively.

2, light-dividing device according to claim 1 is characterized in that, N+2 of the trunk end formation light-dividing device of the trunk end of described N 1:2 type optical branching device and two 1:N+1 type optical branching devices to external port.

3, a kind of passive optical network loop system comprises in logic and independently one leading with standby two optical line terminals and several optical network units; It is characterized in that, comprise that also several have the light-dividing device of two-way beam split function one to one with optical network unit; Independently two optical line terminals and several light-dividing devices are linked to be ring-type by optical fiber in logic, and light-dividing device is by optical fiber and corresponding optical network unit connection.

4, passive optical network loop system according to claim 3, it is characterized in that, described in logic independently two optical line terminals constitute by the optical line terminal physical equipment that an inside has two line terminator modules, perhaps the optical line terminal that has a line terminator module respectively by two inside constitutes.

5, passive optical network loop system according to claim 3 is characterized in that, described in logic independently two optical line terminals respectively with loop in each optical network unit all of the port with set up light and be connected.

6, passive optical network loop system according to claim 3 is characterized in that, described optical network unit is inner N port optical network unit with N line terminator module, and the numerical value of N is the integer more than or equal to 1.

7, passive optical network loop system according to claim 5, it is characterized in that, the described light-dividing device that is connected with N port optical network unit has N+2 port, wherein N port is used to connect N port optical network unit, and two other port is used for N port optical network unit is inserted the EPON loop.

8, passive optical network loop system according to claim 7, it is characterized in that, the light-dividing device of the described N+2 of a having port is made of two 1:N+1 type optical branching devices and N 1:2 type optical branching device, a Zhi Luduan of one of them 1:N+1 type optical branching device is connected with a Zhi Luduan of another 1:N+1 type optical branching device, and the residue Zhi Luduan of each 1:N+1 type optical branching device is connected with a Zhi Luduan of each 1:2 type optical branching device respectively.

9, passive optical network loop system according to claim 8 is characterized in that, N the port that is used to connect optical network unit in the described light-dividing device is respectively the trunk end of N 1:2 type optical branching device; Be used for two ports that optical network unit inserts the EPON loop are respectively the trunk end of two 1:N+1 type optical branching devices in the described light-dividing device.

10, a kind of EPON loop protecting method, described EPON loop comprise that one is main with standby two optical line terminals and several optical network units, set up light respectively with two optical line terminals in the described optical network unit access loop and are connected; It is characterized in that, comprise step:

Optical network unit in A, the loop by self working port with main with optical line terminal and carry out optical communication, standby optical line terminal is in holding state;

B, when the optical fiber of EPON loop opens circuit, standby optical line terminal switches to operating state by holding state; Carry out optical communication with main with optical line terminal by the working port continuation of self with the main optical network unit that keeps light to be connected with optical line terminal; The optical network unit that is connected with standby optical network unit maintenance light switches to working port with standby optical network unit and carries out optical communication.

11, EPON loop protecting method according to claim 10 is characterized in that, described optical network unit is that inside has N line terminator module N port optical network unit, and the numerical value of N is the integer more than or equal to 1.

12, EPON loop protecting method according to claim 11 is characterized in that, when N equaled 1, the N of a described optical network unit port all was a working port.

13, EPON loop protecting method according to claim 12 is characterized in that, when the working port of described optical network unit breaks down, and this optical network unit off-line.

14, EPON loop protecting method according to claim 11; it is characterized in that; when the numerical value of N is during greater than 1 integer, the N of a described optical network unit port all is that working port or part port wherein are working port, and all the other ports are standby port.

15, EPON loop protecting method according to claim 14; it is characterized in that; when the working port of described optical network unit breaks down; the light signal flow that non-working port is born will switch to optical network unit other be in the port of normal condition; port after the switching can be a standby port, also can be the working port that carries out load sharing with the port that breaks down.

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