TWI407729B - Bus-type optical fiber network system - Google Patents

Description

Busbar optical network system

The present invention relates to a busbar type optical fiber network system, in particular to a device that enables the optical fiber terminator and the optical network unit to have traffic control capabilities, so that the fairness of media access conforms to the ideal fairness of the network. The requirements of the features are not affected by the network topology and the network location of the optical network unit, and the network communication can maintain good quality, and the number of central computer rooms and optical fibers can be reduced at the same time, thereby significantly reducing the construction and maintenance costs.

In recent years, the demand for bandwidth on public access networks has increased exponentially due to the strong demand for bandwidth of various communication services. Because in the traditional access network, the available bandwidth and its transferable distance are subject to the transmission characteristics of the twisted wire, and can not effectively meet the needs of various communication services, so the network operators are vigorously pushing the fiber to the home (fiber To the home, FTTH) access to the construction and use of the network. The FTTH access network has been launched in several regions in Europe and Asia, but its high construction and maintenance costs have become a bottleneck for the rapid global development of FTTH networks. Therefore, how to reduce the construction and maintenance costs and keep the communication quality from deteriorating is an important issue for the FTTH access network.

The public access network can be considered as being between the backbone network and the network user. bridge. A wider bridge can carry more traffic. The capacity of the optical fiber is much larger than the capacity of the twisted wire, and the bandwidth requirement of a network user is very small, so the capacity of one optical fiber can be shared by multiple network users. Therefore, in the construction of the FTTH network, it is a reasonable way to reduce the construction cost by the environment of media sharing. In order to establish a media sharing environment, several multiple access network structures have been proposed as a reference for constructing FTTH networks. These multiple access network structures can be divided into two categories according to the difference in the number of optical network units (ONUs) that the optical fibers are connected to. In the first category, each group of fibers is connected to only one ONU, and in the second type of network structure, each group of fibers is connected to multiple ONUs. The second type of network topology is a ring [refer to the second figure], and the end of the ring fiber is terminated by an optical line terminal (OLT). This fiber terminator is located in the central office (CO). Each OLT contains two transmitters and two receivers. One set of transmitters and receivers is used to generate the upstream channel flow, and the other set of transmitters and receivers are used to generate the downlink channel flow, and the upstream and downstream channels are in opposite directions. On the other hand, the first type is due to the presence or absence of a splitter or a passive fiber branching point, and its network structure can be divided into a star (see Figure 3) and a tree ( Tree) [Refer to Figure 4] Two topologies. In the star topology, CO is the center of the star, from which the fiber is distributed to the ONU. In the tree topology, the splitter or passive fiber branch point is the sub-center, and the fiber branches from the sub-center to the ONU; in addition, there is a fiber link between the OLT and the sub-center, which is used as the middle Following this relay, there are uplink and downlink channels. The downlink channel bearer is sent by the backbone network through the OLT. The message forwarded to the ONU (message), the upstream channel collection is transmitted by the ONU, and then transmitted to the backbone network via the OLT.

The FTTH network with the first type of topology requires a large amount of fiber because the bandwidth of the fiber is very inefficient. Therefore, the FTTH network built on this topology must pay a large amount of cost to purchase and install optical fibers. On a ring-shaped FTTH network, the bandwidth efficiency of the fiber is much higher than that of the star and the tree. Therefore, the number of fibers required for construction is less than that of a star or a tree; therefore, the construction cost of the fiber is spent on the fiber. Far lower than a star or tree FTTH network. However, in a ring-shaped FTTH network, the distance from one CO to the farthest ONU is much shorter than the corresponding distance within the star or tree FTTH network, and this effect leads to a relative increase in the number of COs. An increase in the number of COs will increase the cost of CO construction. Therefore, from the perspective of construction cost, to compare the star or tree topology and the ring topology, the construction cost of the ring topology due to the reduction in the number of fibers is required to compensate for the construction cost due to the increase in the number of COs. . Conversely, the star or tree topology, the construction cost saved by the reduced number of COs, is used to compensate for the construction cost of the large increase in the number of fibers. On the other hand, the maintenance cost of the FTTH network is related to the number of optical fibers. The use of a large number of optical fiber FTTH networks not only complicates the deployment of optical fibers, but also increases the difficulty of fiber management and maintenance. Will increase the cost of FTTH network maintenance. Therefore, if the amount of CO and fiber is reduced at the same time, not only the construction cost of the FTTH network can be reduced, but also the maintenance cost can be lowered.

In the media sharing environment of the FTTH network, most FTTH networks use time-division multiple access (TDMA) technology on the upstream channel. The downstream channel uses time-division multiplexing (TDM) technology. In the downlink channel, except for a small number of control and maintenance messages sent by the OLT, most of the messages are mostly the response of the communication service initiated by the network user. Although the TDM technology can fairly use the bandwidth of the downstream channel to transmit a response message to the corresponding ONU, it cannot effectively apply the capacity of the channel. In addition, the amount of response traffic of a service initiated by a network user varies according to the type of service that is initiated, and the multiplex technology of TDM cannot flexibly and dynamically allocate bandwidth according to different services. Therefore, the application of TDM multiplex technology to the downlink channel does not meet the changing demand for commercial bandwidth on the public access network. In terms of the uplink channel, all ONUs connected to an OLT are senders using channels. The TDMA multiple access technology provides the required bandwidth according to the bandwidth requirements of the ONU by the customer premise equipment (CPE). Under this operating condition, when some ONUs initiate service requests while the network is under heavy load, these ONUs will not be able to get the bandwidth they need in time, and must wait for a period of time for the required bandwidth. In such an operating environment, if the number of ONUs is increased, it is necessary to extend the reload time, and the time required to wait for a sufficient bandwidth will be lengthened accordingly. On the other hand, an organization that performs control functions such as connection admission control, resource management, and priority control on the backbone network, such as usage parameter control (UPC) Will reject the ONU has been sent, but beyond the amount of traffic permitted by the commercial contract, which will result in rejected traffic, in the backbone "retransmission" between the network and the ONU. Repeated "re-transmission" will invalidate the bandwidth of the upstream channel; this invalid occupancy will not only reduce the ONU's throughput, but also increase the network's reload time. This vicious cycle will make the message waiting time in the ONU lengthy; however, in order to reduce the construction and maintenance costs, the number of ONUs connected to an OLT must be increased, which will inevitably lead to the frequency of network overload conditions. Increase, and the reload time will continue to grow. Therefore, the reduction of construction and maintenance costs will inevitably lead to a deterioration in the quality of FTTH network communication. [Communication quality refers to the average waiting time of network nodes, while waiting time refers to the first buffer in the node. , the length of time the data segment is waiting to be transmitted].

The reason is that the average waiting time of a node can be regarded as a symbol of the node's access to the media bandwidth. The shorter the average waiting time of a node, the greater the access rights of the node to the media bandwidth. In the case of a high-speed TDMA network, the average waiting time of the node is inversely related to the node's traffic, regardless of the network topology. Based on this feature, it can be inferred that if the media access control of the fiber TDMA network is controlled by the application of traffic control, the network will meet the requirements of the ideal fair behavior of the network. The ideal fair behavior of this network means that the average waiting time of the node does not change with the change of the node position when the node traffic does not change. On the public business network, traffic control is an important process; from a business behavior perspective, network users must pay for the required bandwidth, and the higher the bandwidth required, the higher the cost. . If the amount of traffic transmitted by a node can be controlled according to the content of the commercial contract, then the UPC The "retransmission" operation resulting from the control will not occur. Therefore, the capacity of a TDMA channel will be fully and reasonably allocated to all nodes; in addition, when using the traffic control method to allocate the access rights of the TDMA channel to each node, the communication quality of the TDMA network, Even when the network is fully loaded, it will not deteriorate. Therefore, traffic control must be used by the FTTH network to allocate bandwidth access rights to increase the number of ONUs, effectively reducing construction and maintenance costs, and ensuring that communication quality does not deteriorate due to cost reduction. The main object of the invention.

Based on the above description, the present invention proposes a system for constructing an FTTH network. The topology of this system is a busbar type and consists of a pair of optical fibers. The TDMA technology establishes a media sharing environment on the busbars. The capacity of the two fibers is shared by all ONUs (shared uplink channels) and within the OLT. The queue corresponding to the ONU (shared downstream channel) is shared. The medium access control protocol (MAC) of the ONU and the OLT must control the access of the TDMA bandwidth in a traffic control manner. Since the FTTH network adopts a bus-type topology, the distance from the CO to the farthest ONU of the OLT will be far longer than the corresponding distance of the ring FTTH network, and at the same time, it is required The number of fibers used is also much less than that used in a star or tree FTTH network; therefore, the FTTH network system of the present invention requires a reduction in the number of COs to be constructed and the number of fibers to be used. The construction and maintenance costs that are required to be spent are greatly reduced. In addition, since the traffic control is used in the media access, the FTTH network system of the present invention not only allocates the entire transmission capacity reasonably among the ONUs, but also enables the network to be in a fully loaded state. Road, still able to maintain good communication quality.

(1) ‧‧‧Fiber

(11)‧‧‧ Receiving busbars

(12)‧‧‧Transport busbar

(2) ‧‧‧Fiber Terminator

(21)‧‧‧ Near-end fiber terminator

(22)‧‧‧Remote fiber terminator

(3) ‧‧‧ Optical Network Unit

First: Schematic diagram of the bus-type fiber-to-the-home network architecture of the present invention

Figure 2: Schematic diagram of the existing ring-to-home network architecture

Figure 3: Schematic diagram of the existing star-to-home network architecture

Figure 4: Schematic diagram of the existing tree-like fiber-to-home network architecture

For a more complete and clear disclosure of the technical means, the purpose of the invention, and the effect of the present invention, the following detailed description is provided,

Please refer to the first figure, which is a schematic diagram showing the architecture of the bus-type fiber-to-the-home (FTTH) network system of the present invention. The busbar fiber-to-the-home network system comprises: a pair of optical fibers (1), two optical fiber terminators (2), and a plurality of optical network units (3); wherein: the pair of optical fibers (1), one of which is transmitted A trans-mitting bus (T Bus) (12), the other is a receiving bus (a receiving bus, R Bus) (11); the transmitting bus (12) is an upstream channel [an upstream channel] The traffic carried on the upper slot is transmitted to the customer at the other end served by the backbone network; the receiving bus (11) is the downstream channel [an downstream channel], and the message carried on the upper slot Service, which is received by customers in the fiber-to-home network; the two-fiber terminator [optical line terrni] Nal, OLT] (2), divided into two parts, the first part is located in the central office (CO) or close to the central machine room, called the near-end fiber terminator [the near part of Optical line terminal, OLTN (21), the second part is to terminate the optical fiber (1) at the remote location away from the central equipment room, called the far part of optical line terminal (OLTF) ( twenty two). The near-end fiber terminator (21) and the remote fiber terminator (22) both include a slot generator and a slot terminator, so that the TDMA channel on the transmission busbar (12) flows far away. The slot generator of the fiber optic terminator (22) transmits the slot terminator that enters the near-end fiber terminator (21), and the TDMA channel stream on the receiving busbar (11) is terminated by the near-end fiber optic The slot generator of the device (21) transmits and enters the slot terminator of the remote fiber terminator (22); in addition, the near-end fiber terminator (21) is used to switch the fiber to the home network and backbone The inter-network communication; the optical network unit (3) [optical netw-ork unit, ONU] is connected between the transmission bus (12) of the FTTH network and the receiving bus (11). The interface between the FTTH network and the user's private network [private networks]; the private network includes various customer premise equipments (CPEs), and the front end device and its interface can directly interface with the optical network The circuit unit (3) is connected to the optical network unit (3) through a wireless network, a coaxial network, or various regional networks, and the like. The media access control protocol of each optical network unit (3) must have and perform a traffic control function when accessing the bandwidth of the transport bus (12). Moreover, the maximum transmittable traffic amount of each optical network unit (3) can be limited, and the maximum allowable transmit traffic amount can be regarded as a traffic control of each optical network unit (3). A parameter that dynamically changes as the contract of the maximum transmittable traffic changes. Accordingly, the maximum transmittable traffic of the receiving busbar (11) to the optical network unit (3) is also regarded as a parameter of the traffic control of the near-end fiber terminator (21), which can be maximized. The contract that can transmit traffic changes dynamically and changes.

In order to transmit the traffic to the optical network unit (3), there are a plurality of queues in the near-end fiber terminator (21), each of which corresponds to an optical network unit (3), each optical network The corresponding queue of the road unit (3) temporarily stores the traffic to be delivered to the optical network unit (3) via the receiving bus (11). Although the near-end fiber terminator (21) is the only device that sends traffic to all optical network units (3), all the queues in the near-end fiber terminator (21) are truly shared receive busses ( 11) Bandwidth components. Therefore, the TDMA slots on the receiving busbar (11) need to be advertised by all the queues in the near-end fiber terminator (21). In order to distribute the right to receive the bus (11) between these queues fairly and reasonably, the mechanism that the near-end fiber terminator (21) performs the traffic control must write the message to the queue. Start when slot. The maximum amount of traffic that can be transmitted by a queue is determined by the contract between the user and the network operator connected to the corresponding optical network unit (3). Therefore, the recommended network receiving bus (11) TDMA technology is used to complete multiple access, so the FTTH access network can flexibly meet the dynamic needs of customers in terms of bandwidth.

Since the present invention uses a busbar topology, the distance between the central computer room and the farthest optical network unit in an FTTH network is much greater than the corresponding distance in the ring FTTH network, which will make the busbar The service area covered by the fiber-to-the-home network is far larger than the service area covered by the central computer room built by the ring-to-fiber network. Therefore, not only the number of fibers used in the bus-to-home network can be large. The reduction in the number of central computer rooms required can also be reduced at the same time. Therefore, the construction cost of the bus-type fiber-to-the-home network can be greatly reduced. In addition, since the allocation of media access rights is completed by the traffic control, not only the convergence is transmitted. The access rights of the row and receiving busbars can be reasonably allocated to all the optical network units and the corresponding queues in the near-end fiber terminator. At the same time, the bus-type fiber-to-the-home network can still be fully loaded even when fully loaded. Maintain high communication quality.

The above is only a part of the embodiments of the present invention, and is not intended to limit the present invention, and it is intended that the invention may be included in the scope of the present invention.

In summary, the embodiments of the present invention can achieve the expected use efficiency, and the specific technology disclosed therein has not been seen in similar products, nor has it been disclosed before the application, and has completely complied with the provisions of the Patent Law. And the request, the application for the invention of a patent in accordance with the law, please forgive the review, and grant the patent, it is really sensible.

(1) ‧‧‧Fiber

(11)‧‧‧ Receiving busbars

(12)‧‧‧Transport busbar

(2) ‧‧‧Fiber Terminator

(21)‧‧‧ Near-end fiber terminator

(22)‧‧‧Remote fiber terminator

(3) ‧‧‧ Optical Network Unit

Claims (3)

A busbar type optical fiber network system includes: a pair of optical fibers, one of which is an upstream bus transmission bus, and the other is a downlink channel receiving busbar, and both busbars adopt TDMA (time-sharing multiple access, Time-division multiple access) technology for multiple access; two fiber terminators, all with traffic control capabilities, one in a central machine room or close to the central machine room, for the near-end fiber terminator, another The terminal fiber is located at a remote location away from the central computer room, and is a remote fiber terminator, and the remote location of the central computer room refers to another central computer room or any optical fiber transmission outside the central computer room. One of the positions; a plurality of optical network units, connected between the transmission bus and the receiving bus, is an interface between the fiber-to-the-home network and the user's private network; the media connection of each optical network unit Take the control agreement, and must have and perform the traffic control function when receiving the bandwidth of the transmission bus. The bus-type optical fiber network system according to claim 1, wherein the private network of the fiber-to-the-home network includes a customer front-end device, and the front-end device and the interface thereof can directly connect with the optical network unit. Or connect to the optical network unit through one of a wireless network, a coaxial network, or a regional network. The bus-type optical network system according to claim 1, wherein the maximum transmittable traffic amount of each optical network unit is limited, and the maximum allowable transmit traffic amount can be regarded as each a traffic control parameter of an optical network unit, The parameter can be dynamically changed as the maximum transmittable traffic volume changes; accordingly, the amount of traffic received by the receiving busbar to each optical network unit can also be regarded as the traffic control of the near-end optical fiber terminator. The parameters can be dynamically transmitted to each optical network unit as the maximum transmittable traffic changes.