Fiber optic network as a high-speed and effective pronoun has been deeply rooted in the hearts of the people, and has been deployed and applied on a large scale in the communication system. The realization of transparent and high survivability all-optical communication network is the development goal of broadband communication network. As an important basic technology in all-optical communication network, the development and application of optical switching technology largely determine the future direction of optical communication network. This paper briefly introduces the concept and development of optical switching technology and its application in communication, so as to provide research and discussion for scientific researchers.
The advantages of optical fiber communication lie in its huge information capacity and strong anti-jamming ability. Its superior performance has been proved for a long time. In modern communication system, it gradually replaces the communication network composed mainly of electronic circuits, and becomes an important way of modern communication. However, the lack of electronic circuits in the original communication system hinders the development of the advantages of optical fiber communication system and becomes the bottleneck of performance.
In the optical fiber communication system, only a scientific and reasonable communication architecture can give full play to the advantages of optical fiber system and form an ideal high-speed, large-capacity and high-quality optical fiber network. The original electronic line communication is a huge obstacle in the implementation of all-optical network. To remove the influence of electronic line, optical fiber communication is needed. The progress of system technology . The process of photoelectric conversion exists in the coexistence of traditional communication network and optical fiber network, and the combination of the two is limited by electronic devices. The capacity of photoelectric exchange information depends on the working speed of the electronic part. The original optical fiber network with large bandwidth becomes narrow when photoelectric exchange is carried out, resulting in the bandwidth of the whole network. Be limited to. Therefore, in optical communication networks, optical switching needs to be carried out directly on the switching nodes without optoelectronic conversion. Only in this way can the communication bandwidth of optical fibers be released, and the advantages of large communication capacity and high communication rate can be realized. Therefore, optical switching technology has attracted much attention and is considered as the most important part of the new generation of broadband technology.
1. Ways of Optical Switching
Optical signal multiplexing generally has three modes: space division multiplexing, time division multiplexing and wavelength division multiplexing. There are also space division switching, time division switching and wavelength division switching to complete the switching of three multiplexing channels .
Space separation switching is the optical signal in the switching space domain, and its basic functional component is the space optical switch. The principle of space optical switch is that the optical switching elements are composed of gate array switches, which can arbitrarily establish paths in optical fibers with multiple inputs and multiple outputs. It can be used as an air separation optical switching unit, or as a time division or wave division switching unit together with other types of switches. There are two types of space-splitting switch: optical fiber switch and space switch. The space-splitting switch divides the switching space.
Time division multiplexing (TDM) is a common method of signal multiplexing in communication networks. A channel is divided into several different time slots. Each optical signal allocates different time slots, and a baseband channel is fitted to a high-speed optical data stream for transmission. Time-division switching needs to be implemented using slot switches. The slot switch writes the input signal into the optical buffer sequentially, and reads it out in the given order, so that any slot in a frame can be switched to another slot and output, and the program of sequential switching is completed. Generally, bistable lasers can be used as optical buffers, but they can only output in bits, which can not meet the needs of high-speed switching and large capacity. Fiber delay line is a kind of time-division switching equipment, which uses more time-division multiplexing signals to input into the optical splitter, so that each output path has only one optical signal with the same time slot, and then these signals passing through different optical delay lines are combined to obtain signals through different time-delay lines. Different time delays are combined to match the original signal before signal multiplexing, thus completing time-division switching.
Wavelength division multiplexing (WDM) technology is widely used in optical transmission systems. Generally, in optical wavelength division multiplexing systems, both source and destination end need to use the same wavelength of light to transmit signals. For example, each multiplexing terminal needs to use additional multiplexing equipment when not so multiplexing, which increases the cost of the system. Complexity
. Therefore, if we use WDM switching in the intermediate transmission node in WDM system, we can meet the need of no additional devices to realize the source-end interoperability of WDM system, and can save system resources and improve resource utilization.
Hybrid switching technology is a multi-level link optical connection in large-scale communication networks, which is composed of multiple switching technologies. In large-scale networks, the advantages of WDM can not be brought into full play because of the need to divide the multi-channel signals into different links, so it is necessary to use WDM technology in connection links at all levels, and then use space division switching technology to complete link-to-link connection in link switching at all levels, and finally re-target end. Wave division switching technology is used to output the corresponding optical signal, and then the signal is merged and finally the output is divided. The commonly used switching technologies include space-time mixing, space-time-wave mixing and space-time-wave mixing.