Release date : 2016/9/5 10:23:07

The fiber coaxial cable hybrid network will become the main body of the broadband communication network. Hybrid fiber coaxial cable (HFC) has two structures, one is from the cable television network (CATV), and the other is from the telecommunication network.
At present, there are hundreds of millions of TV sets in my country, and the number of TV sets far exceeds that of telephone sets by many times. The cable television network (CATV) develops rapidly and continues to grow, and there are more than 1,000 cable television stations alone. Small-scale CATV networks are interconnecting through satellite channels, microwave channels or optical fiber channels to form a CATV network with larger geographic coverage. Obviously, if the CATV network is transformed from the current broadcast network to a two-way interactive network, and the TV and telecommunication services are integrated, the CATV network will become a new computing access network. At present, CATV network technology will become the focus of research and development.
Since the 1990s, due to the maturity of high linearity DFB (distributed feedback line) laser manufacturing technology, its price has dropped significantly, prompting AM-VSB optical fiber transmission systems to be widely used in cable television networks. After AM fiber enters the field of cable television, it has a significant impact on the topology of the cable television network. First, the traditional multi-stage amplifier cascaded coaxial cable trunk line is replaced by high-quality AM fiber trunk line, which improves the transmission quality of CATV; secondly, the bidirectional transmission of CATV is practically applied. As a result, the network topology is transformed from a unidirectional tree to a star and a bus. Its structures include: fiber to branch, fiber to roadside, and fiber to the last amplifier. The introduction of AM optical fiber technology makes the cable television network that transmits multi-channel TV programs singly develop into a comprehensive multi-function network that transmits TV, telephone, data and multimedia services.
At the same time, the telecommunications industry has also proposed the HFC method. The representative one is AT&T in the United States. AT&T proposed the latest HFC scheme as early as 1994. As soon as it was proposed, it attracted great attention from the telecommunications industry and was quickly adopted. Used by many telecommunications companies in the United States.
AT&T's HFC is a broadband communication network using subcarrier technology. Optical fibers are used between switches and optical nodes, and coaxial cables are used for network interface units (NIUs) from optical nodes to user terminals, which can transmit TV programs (broadband services), as well as telephony and narrowband data. Each optical node of HFC can provide comprehensive services to 400-2500 users.
In Europe, the French company ALCATEL, the world's largest manufacturer of telecommunication equipment, has also proposed its own HFC solution, namely ALCATEL1570BB, from the reality of Europe.
The use of HFC technology can realize the connection of PC to the Internet. HFC network is likely to develop into the main body of broadband communication network, and realize multimedia communication in combination with multimedia computer.
Because HFC is based on the analog transmission mode, it can comprehensively access a variety of service information. Up to now, the main services that can be realized are: telephone, analog radio and television, digital radio and television, on-demand television, and digital interactive services. The HFC network formed by merging the telephone network, the data network and the cable television network can provide various services of the original three networks. That is what people now call "three networks in one".
About HFC spectrum arrangement: Among them, 5-50MHZ is used for ordinary telephone services; 50-550MHZ is used for CATV; currently, it can transmit 60-100 channels of analog broadcast PAL TV signals; 550-750MHZ is used for 400 channels of compressed digital channels , of which 200 are used for on-demand TV, 200 are used for interactive services; 750-1000MHZ is reserved for personal communication.
Under the current situation that fiber-to-user is not realistic, adopting the HFC system in which the main line is optical fiber and the access network is coaxial cable can integrate CATV, data communication and telephone for cost-effective transmission, and realize CATV as soon as possible. , data communication, telephone three networks merge and normalize transmission.