Views: 77 Author: Site Editor Publish Time: 2020-04-13 Origin: Site
As we all know, the bubble in the IT industry in 2000 led to the explosive development of the production scale of the fiber optical communication industry and the overproduction of fiber optic products. Whether it is optical transmission equipment, optoelectronic devices and optical fibers, their prices have plummeted. So when would the fiber optic communications market recover?
In 2002, it was the lowest valley of optical fiber communication market, which was equivalent to 4 years of retrogression. In recent years, the fiber optic communications market has also improved with the IT market.
After all, FTTH is the demand of the information society, and the optical fiber communication market must have a bright future. FTTH in developed countries has already started construction and there is already a considerable market. In general, with the needs of the market, the profits of devices and equipment will gradually rise. But in the fibre optical industry, despite the success of anti-dumping, prices are still low and profits are minimal. In fact, in the world, the production scale of optical fiber is too large, and the development speed of FTTH is affected by the social environment, including the economic conditions of citizens and the development of digital TV.
The general trend of the development of optical fiber communication is to continuously improve the information rate and increase the relay distance. The figure of merit of the system is expressed by the "information rate" and "distance", which is approximately doubled each year. Develop optical fiber networks, especially optical fiber user networks. Use new technologies, especially rare earth-doped optical fibers amplifier, photoelectric integration and optical integration.
1. The highest level of commercial optical fiber communication system in the early 1990s was 2.488Gbit/s system. The information rate of the experimental system in the laboratory is 8, 10, 16 Gbit/s, the corresponding non-relay distance is 76, 80, 65 km, and the information rate has reached 20 Gbit/s. If the speed of the single machine is too high, the speed of the electrical time division multiplexing and demultiplexer of the large-scale integrated circuit will increase, and the laser must be able to work stably at a very high speed. If the 1.55μm wavelength is used and the conventional single-mode optical fiber is used, excessive dispersion and intersymbol interference will be technical difficulties. It is also uneconomical. Optical wavelength division multiplexing (OWDM) can be used to increase the information rate. The number of multiplexing in the laboratory is multiplexed with up to 100 systems of 622 Mbit/s, with a wavelength interval of 0.1 nm, a transmission distance of 50 km, and incoherent reception. Subcarrier modulation (SCM) can also be used to increase system capacity and used in fiber optic cable TV systems.
The success of the rare earth metal erbium-doped single-mode fiber amplifier has greatly increased the sensitivity and transmission distance of the system. The recently published loop test of the conventional system has four erbium-doped fiber amplifiers in this loop, with transmission rates of 2.4Gbit/s and 5Gbit/s. The calculation results show that the transmission distance reaches 21000km and 9000km. The wavelength is 1.55 μm, and dispersion-shifted fiber is used. This test system will be practical in the new optical cable system across the Pacific and Atlantic.
The system that uses optical wavelength division multiplexing to increase the rate and uses optical amplification to increase the transmission distance is the fifth-generation optical fiber communication system. In the new system, the coherent optical fiber communication system has reached the level of field experiments and will be applied in practice. The optical soliton communication system can obtain extremely high rates, and the experimental results have reached 32 Gbit/s. Adding fiber amplifiers to the system makes it possible to realize fiber communication at extremely high rates and long distances.
2. Optical fiber user network. The use of synchronous optical fiber network (SONET) or synchronous digital system (SDH) and the establishment of optical fiber user networks are two major steps to achieve broadband services.
Optical fiber user networks have different structures. The connection between the central office and the remote office can use a ring network to improve the flexibility and efficiency of the network. The network from the remote office to the user can be a single star or double star network.
3. Erbium-doped fiber amplifier has the advantages of high gain, wide bandwidth, low noise, easy connection with transmission fiber, easy manufacturing, etc. It can be used for pre-amplification, line amplification and final amplification. It can improve the system sensitivity and increase the transmission distance. Using it in the user network can expand the scope of the network and increase the number of users, which will play an important role in the development of fiber optical communications. The erbium-doped fiber amplifier only works at 1.55μm, and it is necessary to explore the fiber doped with another rare earth metal to obtain an amplifier that works at 1.3 μm.
In addition, in order to improve the reliability and economy of the fiber optical communications system, optoelectronic integration and optical integration are required.
