1. Overview of optical fiber communication In 1966, Chinese-American CKKao and CA Hockham published papers, foreseeing that low-loss optical fiber can be used for communication, knocking on the door of optical fiber communication, and attracting people Attention. In 1970, Corning Corporation of the United States successfully developed optical fiber with a loss of 20dB / km for the first time, and the era of optical fiber communication began. Optical fiber communication uses light waves of very high frequency (on the order of 1014 Hz) as carrier waves and optical fibers as transmission media. Optical fiber communication has the advantages of low loss, transmission frequency bandwidth, large capacity, small size, light weight, anti-electromagnetic interference, and not easy to crosstalk. It is favored by people in the industry and has developed very rapidly. The transmission capacity of the optical fiber communication system has increased by nearly 10,000 times from 1980 to 2000, and the transmission speed has increased about 100 times in the past 10 years.
The development of optical fiber communication depends on the progress of optical fiber communication technology. At present, optical fiber communication technology has made great progress, and new technologies are constantly emerging, which has greatly improved communication capabilities and continuously expanded the application range of optical fiber communication.
Second, the current status of optical fiber communication technology development (1) wavelength division multiplexing technology. Wavelength division multiplexing technology can make full use of the huge bandwidth resources brought by the single-mode fiber low-loss region. According to the different frequency (or wavelength) of the light wave of each channel, the low loss window of the optical fiber is divided into several channels, the light wave is used as the signal carrier, and the wavelength division multiplexer (wave combiner) is used at the sending end The signal optical carriers of the wavelength are combined and sent to an optical fiber for transmission. At the receiving end, a wavelength division multiplexer (demultiplexer) separates these optical carriers carrying different signals at different wavelengths. Since the optical carrier signals of different wavelengths can be regarded as independent of each other (when the nonlinearity of the optical fiber is not considered), multiplexing transmission of multiple optical signals can be realized in one optical fiber.
(2) Fiber access technology. The fiber access network is the "last mile" of the information highway. To realize the high-speed transmission of information and meet the needs of the public, not only a broadband backbone transmission network, but also the user access part is the key, and the optical fiber access network is the key technology for high-speed information flow into millions of households. In optical fiber broadband access, due to the different location of the optical fiber, there are different applications such as FTTB, FTTC, FTTCab and FTTH, collectively called FTTx. FTTH (Fiber to the Home) is the ultimate method of optical fiber broadband access. It provides all-optical access. Therefore, it can make full use of the broadband characteristics of optical fibers and provide users with the unlimited bandwidth required to fully meet broadband access. Demand. At present, domestic technology can provide users with FE or GE bandwidth, which is an ideal access method for users of large and medium-sized enterprises.
Third, the development trend of optical fiber communication technology In recent years, with the advancement of technology, the reform of the telecommunications management system and the gradual and comprehensive opening of the telecommunications market, the development of optical fiber communication has once again presented a new situation of vigorous development. The main development hotspots in the field are summarized and prospected. [
(1) Development towards ultra-high speed systems. From the perspective of the development of telecommunications in the past 20 years, the demand for network capacity and the increase in transmission rate have been a major contradiction. The development of traditional optical fiber communication has always been carried out in accordance with the electrical time division multiplexing (TDM) method. When the transmission rate is increased by 4 times, the cost per bit is reduced by about 30% to 40%: Therefore, the economic benefits of high bit rate systems are roughly exponential The regular growth is the fundamental reason why the transmission rate of optical fiber communication systems has been continuously increasing over the past 20 years. At present, the commercial system has increased from 45Mbps to 10Gbps, and its rate has increased by 2000 times in 20 years, which is much faster than the increase in the integration of microelectronics technology during the same period. The emergence of high-speed systems not only increases the service transmission capacity, but also provides the possibility of realizing various new services, especially broadband services and multimedia.
(2) Evolution to ultra-large capacity WDM system. The expansion potential of the electrical time-division multiplexing system has been exhausted. However, the 200nm available bandwidth resources of the fiber only use less than 1%, and 99% of the resources have yet to be explored. If multiple light source signals with appropriately shifted wavelengths are simultaneously transmitted on a pole fiber, the information transmission capacity of the fiber can be greatly increased. This is the basic idea of ​​wavelength division multiplexing (WDM). The main benefits of using WDM systems are: 1. Can make full use of the huge bandwidth resources of optical fiber, so that the capacity can be quickly expanded several times to hundreds of times; 2. It can save a lot of optical fiber and regenerator during large-capacity long-distance transmission, thereby greatly reducing the transmission cost: 3. It has nothing to do with the signal rate and electrical modulation method, it is a convenient means to introduce new broadband services; Using WDM network to achieve network exchange and recovery is expected to realize the future transparent and highly survivable optical networking.
(3) Realize optical networking. Although the above practical wavelength division multiplexing system technology has huge transmission capacity, it is basically a system based on point-to-point communication, and its flexibility and reliability are not ideal. If the add-drop function and cross-connect function similar to SDH on the circuit can also be realized on the optical path, it will undoubtedly increase the power of a new layer. According to this basic idea, both optical add-drop multiplexer (OADM) and optical cross-connect equipment (OXC) have been successfully developed in the laboratory, and the former has been put into commercial use. The basic purpose of achieving optical networking is: 1. Realize ultra-large capacity optical network; 2. To achieve network scalability, allowing the continuous growth of the number of nodes and services of the network; 3. Realize the reconfigurability of the network and achieve the purpose of flexible reorganization of the network; 4. Realize the transparency of the network, allowing interconnection of any system and signals of different standards; 5. To achieve rapid network recovery, the recovery time can reach 100ms. In view of the above-mentioned potential huge advantages of optical networking, developed countries have invested a lot of manpower, material and financial resources for preliminary research. Optical networking has become another new climax of optical communication development following SDH electrical networking.
(4) A new generation of optical fiber. In recent years, with the explosive growth of IP traffic, telecommunication networks are beginning to develop in the direction of sustainable development of the next generation, and building a fiber optic infrastructure with huge transmission capacity is the physical foundation of the next generation network. The traditional G.652 single-mode fiber has been exposed to the development of the above-mentioned ultra-high-speed long-distance transmission network. The development of new optical fibers has become an important part of the development of next-generation network infrastructure. At present, in order to adapt to the different development needs of the backbone network and the metropolitan area network, two different new optical fibers have emerged, namely non-zero dispersion fiber (G.655 fiber) and anhydrous absorption peak fiber (full wave fiber).
(5) Optical access network. Over the past few years, the core of the network has changed dramatically. Both the exchange and the transmission have been updated for several generations. Soon, this part of the network will become a fully digital, software-dominated and controlled, highly integrated and intelligent network. On the other hand, the existing access network is still dominated by twisted-pair copper wires (more than 90%) and the original backward analog system. The huge technical contrast between the two shows that the access network has indeed become a bottleneck restricting the further development of the entire network. The only long-term technical means that can fundamentally and completely solve this bottleneck problem is the optical access network. The main purpose of using the optical access network in the access network is to reduce maintenance and management costs and failure rates: develop new equipment and increase new revenue; cooperate with the adjustment of the local network structure to reduce nodes and expand coverage; make full use of the fiberization A series of benefits: building a transparent optical network and welcoming the multimedia era.
Lead-acid is the oldest rechargeable battery in existence. Invented by the French physician Gaston Planté in 1859, lead-acid was the first rechargeable battery for commercial use. 150 years later, we still have no cost-effective alternatives for cars, wheelchairs, scooters, golf carts and UPS systems. The lead-acid battery has retained a market share in applications where newer battery chemistries would either be too expensive.
Lead-acid does not lend itself to fast charging. Typical charge time is 8 to 16 hours. A periodic fully saturated charge is essential to prevent sulfation and the battery must always be stored in a charged state. Leaving the battery in a discharged condition causes sulfation and a recharge may not be possible.
Finding the ideal charge voltage limit is critical. A high voltage (above 2.40V/cell) produces good battery performance but shortens the service life due to grid corrosion on the positive plate. A low voltage limit is subject to sulfation on the negative plate. Leaving the battery on float charge for a prolonged time does not cause damage.
Vrla Ev Batteries,Electric Bicycle Vrla Battery,Motorcycle Vrla Battery,Rechargeable Vrla Ups Battery
Starlight Power Industrial Company Limited , https://www.starlite-power.com