In recent years, the continuous development of network video surveillance is inseparable from the support of network broadband. At the same time, the huge demand for bandwidth of network surveillance also promotes the development of access technology. Network monitoring is characterized by high definition, networking, popularization and complexity. With the construction of “safe city” and “smart city”, optical transceiver access and optical fiber transceiver access can not meet the needs of access bandwidth, and the existing access methods will have bottlenecks.

Modern cities are developing towards multi-function, and the urban layout is becoming more and more complex. There are hundreds, hundreds or even thousands of ground monitoring points. To ensure that functional departments can master real-time, clear and high-quality video images at the first time, it highlights the shortage of optical fiber resources. Moreover, in today’s increasingly powerful and complex urban functions, the cost of re laying optical cables is not only very expensive, but also difficult for all parties to coordinate.

In view of this, how to solve the above problems? In fact, the same problem has been encountered in the construction of FTTH (fiber to home) of telecom operators. In order to solve this problem, give full play to the bandwidth advantages of optical fiber, solve the shortage of optical fiber resources and improve the reliability of the network, telecom operators choose PON (passive optical network) technology. This technology can also be applied to security network monitoring.

What is PON?

PON (passive optical network) is passive optical network. A passive optical network includes an optical line terminal (OLT) installed in the central control station and a batch of supporting optical network units (onus) installed in the user site. The optical distribution network (ODN) between OLT and ONU includes optical fiber and passive beam splitter or coupler.

How to solve the problem of remote monitoring transmission

The PON system structure is mainly composed of the optical line terminal (OLT) of the central office, the optical distribution network (ODN) including passive optical devices, and the optical network unit / optical network terminal (ONU / ont optical network unit / optical network terminal) of the client. The difference is that the ont is directly located at the client, There are other networks between ONU and users, such as Ethernet) and network element management system (EMS), which usually adopts point to multipoint tree topology.

The outstanding advantage of PON network is that it eliminates the outdoor active equipment, and all signal processing functions are completed in the switch and the equipment in the user’s house. Moreover, the early-stage investment of this access method is small, and most of the funds will not be invested until the user really accesses. Its transmission distance is shorter than that of the active optical fiber access system and its coverage is smaller, but its cost is low, there is no need to set up another computer room and it is easy to maintain. Therefore, this structure can economically serve home users.

There are no active components in the passive optical network from the center to the grounding network. Instead, the passive optical components are inserted into the network, and the transmitted traffic is guided by separating the power of optical wavelength on the whole path. This replacement makes the user no longer need to supply energy and maintenance to the active devices in the transmission loop, which greatly saves the user’s cost. Passive beam splitter and coupler only play the role of transmitting and limiting light, do not need power supply and information processing, and have unrestricted mean time between failures, which can comprehensively reduce the maintenance cost.


From the structure of the whole network, due to the laying of a large number of optical fibers and the application of new technologies such as DWDM, the backbone network has made a breakthrough development in a few years. At the same time, due to the progress of Ethernet technology, the LAN bandwidth dominated by Ethernet is also from 10m, 100m to 1g or even 10g. At present, we are concerned that the most important breakthrough is the section connecting the network backbone, LAN and home users, which is often referred to as the “last kilometer”, which is a bottleneck. We must break this bottleneck before we can usher in a new world of the Internet world. It is like that in a country’s highway system, trunk lines and regional trunk roads have been built with high-grade and wide roads, but the doorway to families and businesses is still a small path. The efficiency of this highway network can not be brought into full play effectively.

After years of development, APON has not really entered the market. The main reason is that the ATM protocol is complex and the equipment is expensive compared with the access network market. At the same time, due to the rapid development of Ethernet technology, ATM technology has completely withdrawn from the LAN. The introduction of Gigabit and 10g standards has opened the door for Ethernet technology to move towards the backbone. Therefore, how to combine simple and economical Ethernet technology with PON transmission structure has attracted extensive attention of technical circles and network operators since 2000. At the same time, the industry generally believes that many shortcomings of ATM PON, such as lack of video transmission capacity, limited bandwidth, complex system and high price, will not exist in EPON.

The first phase goal of optical access network evolution is FTTB (fiber to the building) and FTTC (fiber to the cube) systems, and then developed to FTTH (fiber to the home) to provide users with comprehensive services including data, video and voice through a simple platform. EPON can provide higher bandwidth and more comprehensive services than APON, but the cost is very low. At the same time, the architecture of EPON also meets most requirements of g.983 standard.

The advantages of PON technology are mainly reflected in the following aspects:

1. Optical fiber access network is the most suitable solution for future development. In particular, PON technology has been proved to be a very economical and effective way in current integrated broadband access.

2. Due to the adoption of PON technology, the whole optical distribution network is passive. The passive optical network has small volume and simple equipment. Compared with copper network, PON can reduce maintenance and operation costs and completely avoid electromagnetic interference and lightning interference.

3. The passive ONU (optical network unit) of PON does not need power supply, which not only eliminates a series of problems of power supply, but also has better reliability than active equipment.

4. Due to the use of passive components and shared optical fiber transmission medium, the investment cost of the whole optical network is low.

5. PON is transparent to the transmission system used to a certain extent, and it is easy to upgrade.

PON technology has become the preferred solution to realize fiber to home (FTTH) in the industry. PON technology adopts point to multipoint topology, and downlink and uplink transmit data through TDM and TDMA respectively. The maximum distance between OLT and ONU can reach 20km, the transmission rate is bidirectional symmetrical 1Gbps, and the maximum splitting ratio generally supports 1:32 or higher. It can be divided at one level or connected by multiple splitters. PON technology can effectively solve the bandwidth and distance constraints of network monitoring. The office end OLT equipment is deployed in the office end machine room, and multi-level light splitting is adopted to realize the flexible layout of points;

The ONU webcam is used as the terminal combination, in which the ONU can be a Poe switch with PON function; The bureau sends the uplink multicast data to the customer’s monitoring room and storage server at the same time. It can be monitored in real time in the monitoring room, and the video data can be sent to the storage server to facilitate the collection of post evidence.

In today’s “light advance and copper retreat”, the wide application of PON technology is particularly important. The remote video monitoring system using PON technology reasonably solves the problems of dense and complex modern urban monitoring points and shortage of optical fiber resources. It has incomparable advantages in networking form, optical fiber resources, video quality and reliability, and provides the best network solution for the development of operators’ remote video monitoring business.

Responsible editor: CT


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