In recent years, fiber optic communication technology has developed rapidly and new technologies have been emerging, which has greatly improved the communication capacity and expanded the application scope of optical fiber communication.
First, the development of fiber optic cable in China
1. Common optical fiber
Common single-mode fiber is the most commonly used fiber. With the development of optical communication system, the capacitance of optical relay distance and single wavelength channel increased. 652. The performance of A fiber can be further optimized. The low attenuation coefficient of the 1550rim area is not fully utilized and the lowest attenuation coefficient and the zero dispersion point of the optical fiber are not in the same area. Single mode optical fiber with the cut-off wavelength in accordance with itutg.654. The dispersion displacement single mode fiber of 653 has realized such an improvement.
2. Core network cable
Our country has adopted the optical cable in the main route (including the national trunk line, the provincial trunk line and the main trunk line). The multi-mode fiber has been eliminated, all of which adopt single-mode fiber, including g... 652 optical fiber and g. 655 optical fiber. G.. Although the optical fiber has been used in our country, it will not develop in the future. G.. 654 optical fiber has not been used in China's terrestrial optical fiber because it cannot increase the capacity of optical fiber system greatly. Discrete optical fiber is used in the main fiber optic cable and no optical fiber band is used. Mainline optical cable is mainly used for outdoor. In these optical cables, the once used layer type and skeleton structure have been discontinued.
3. Access network cable
The optical cable in the access network is short, the branch is more, and more frequently, in order to increase the capacity of the net, the fiber core is usually added. Especially in the city pipe, because the inner diameter of the pipe is limited, it is very important to increase the optical fiber concentration density and reduce the diameter and weight of the optical fiber. The access network USES G.. 652 common single-mode fiber and g. 652.C low water peak single mode fiber. Low water peak single mode fiber is suitable for dense wavelength division multiplexing, which has been used in small quantities in China.
4. Indoor optical cable
Indoor optical cables often require simultaneous transmission of voice, data and video signals. It may also be used for telemetry and sensors. The international electrotechnical commission (IEC), in the optical cable classification, refers to the indoor optical cables, which I believe should include at least two large parts of the cable and integrated cable. The local fiber optic cable is placed in the central bureau or other telecommunication room, and the cloth is kept tightly in order and the position is relatively fixed. It is mainly used by the users to use the fiber optic cable in the client room, so the vulnerability should be considered more strictly than the local optical cable.
5. Communication optical cable in power lines
The fiber is dielectric, and the fiber optic cable can be used as the whole medium, which is completely free of metal. Such a full dielectric cable will be the most ideal communication line for the power system. There are two kinds of dielectric optical cables used for power wire rod laying: the all-medium self-supporting (ADSS) structure and the winding structure used for the aerial line. ADSS optical cable is widely used in power transmission system in China because of its wide range and wide range. ADSS optical cable is a popular product in the near future.
The development trend of optical fiber communication technology
In the case of optical fiber communication, ultra-high speed, super capacity and long distance transmission have always been the target of people's pursuit, and the all-optical network is also the dream of people's unremitting pursuit.
1. The transmission capacity of optical fiber transmission system has been greatly improved by the technology of ultra-large capacity and ultra-long distance transmission technology, and there is a wide application prospect in future transsea optical transmission system. In recent years, the wave division multiplexing system has developed rapidly. Currently, the 1.6 Tbit/WDM system has been used in large number of commercial applications, while the total optical transmission distance is also greatly expanded. Another way to increase the transmission capacity is to use optical time division multiplexing (OTDM) technology, and WDM by increasing the number of transmission channel in the single fiber to improve the transmission capacity, OTDM technology is to improve the transmission capacity by increasing rate of single channel, the implementation of single channel 640 gbit/s highest rate.
Only OTDM and WDM can be used to improve the capacity of optical communication system. After all, it can be used to multiplexed multiple OTDM signals so as to improve the transmission capacity greatly. Polarization multiplexing (PDM) technology can significantly reduce the interaction of adjacent channels. Due to zero (RZ) coded signal in the small space in the ultra high speed communication system, reduce the demand for distribution of dispersion management, and RZ encoding of nonlinear optical fiber and polarization mode dispersion (PMD) of strong ability to adapt to, so now the large capacity of WDM/OTDM transmission communication system generally adopts the RZ code. Key technologies for WDM/OTDM hybrid transmission systems are mainly included in the key technologies of OTDM and WDM communication systems.
2. Optical soliton communication.
Optical soliton is a special kind of ps orders of magnitude of ultrashort optical pulse, because it's in the anomalous dispersion region of the fiber, the group velocity dispersion and nonlinear effect balance each other, so after fiber long distance transmission, waveform and speed remains constant. The optical soliton communication is to use the optical soliton as the carrier to realize the long distance non-distortion communication, in the case of zero error code transmission can reach 10,000 miles.
Optical soliton technology is the outlook for the future: in the aspect of transmission speed with long distance high-speed communication, time domain and frequency domain of ultrashort pulse control technology and production and application of ultrashort pulse technology makes the current rate of 10-20 gbit/s increased to more than 100 gbit/s; In the aspect of increasing transmission distance, it adopts the resetting, shaping, regenerating technology and reducing the ASE, and the optical filtering increases the transmission distance to more than 100000km; Low noise high output EDFA is achieved in high-performance EDFA. Practical optical soliton communication, of course, there are still many technical problems, but has led us to believe that the breakthrough progress optical soliton communication, in the long distance, high speed, large capacity optical communication, especially in underwater optical communication system, has a bright development prospect.
3. All-optical network.
The future high-speed communication network will be all optical networks. The whole optical network is the highest stage of the development of optical fiber communication technology. The traditional optical network has realized the QuanGuangHua between nodes, but still USES the electric parts in network node, limits of the current network main total capacity to further improve, so the real all-optical networks has become a very important topic.
All-optical networks with nodes light instead of electricity, between nodes is also QuanGuangHua, information is always in the form of light transmission and exchange, exchange of user information processing is no longer according to bits, but depends on the wavelength routing.