What is the origin and development of optical fiber?
1970, corning company took the lead in developing the world's first timely glass fiber with attenuation less than 20dB/km. This data of 20dB/km was considered as the threshold of optical fiber communication at that time, which was also determined by Dr. Gao Kun's calculation. At that time, the attenuation of existing glass fiber was as high as 1000dB/km, but the attenuation was too high. Cannot be used for communication. Shortly thereafter, in 1970, the first semiconductor laser realized room temperature operation. In this way, the problem of light source and transmission medium is expected to be solved, and the whole world is excited about it! Since then, the prelude of optical fiber research and optical fiber communication research has been opened, and the development of modern optical fiber communication has begun.
When the international optical fiber communication research kicked off, it was the time when Wuhan Institute of Posts and Telecommunications was prepared for construction. Therefore, at the beginning of the establishment of Wuhan Institute of Posts and Telecommunications (WRI)( 1974), the research on optical fiber communication was determined as the main direction. Fiberhome Communication Technology Co., Ltd. was founded by WRI, and the optical fiber and cable industry of Fiberhome Communication Technology Co., Ltd. was developed on the basis of WRI optical fiber and cable research department. With the rapid development of optical cable industry in optical fiber communication technology Co., Ltd., the development history of multimode optical fiber, one of the main products of optical fiber communication, is briefly reviewed, and its development trend is prospected.
Second, the history and development of multimode fiber
Looking back on the development of multimode fiber for 30 years, it can be roughly divided into three stages.
The first stage, 197 1 ~ 1980, is the research and development period of multimode fiber. During this period, the traditional double crucible process was phased out in the world, and four new chemical vapor deposition preform processes were developed, such as MCVD, OVD, VAD and PCVD. From multi-component oxide glass fiber to timely glass fiber: The transmission theory and fiber design of multimode fiber are studied, especially the key technologies to optimize preform technology and improve bandwidth of multimode fiber by analyzing the measurement results of differential mode delay (DMD). ? The multimode optical fiber communication system is tested in the field. The industry standard of 50/ 125-mm gradient multimode fiber (hereinafter referred to as 50 -MMF) is established. 50 mm MMF put into mass production. ? Representatively, Corning's Wilmington optical fiber factory was put into production in June 1979, and T Company's at&: Atlanta optical fiber factory was expanded in April 1979 and put into production the following year. ? In 1980, the global annual output of optical fiber was less than 654.38+10,000 kilometers, and 100% was multimode fiber. This is the beginning of the optical fiber industry. In the following 20 years, the annual output of MMF increased rapidly, reaching 4 million kilometers in 2000 (see table 1).
The second stage, 198 1 ~ 1995, is the development period of practical multimode fiber and increasing new varieties. Worldwide, a practical trunk optical fiber communication system has been established using 50 MMF. However, in the first few years of this period (1983 ~ 1984), the technology of single-mode fiber (G.652A fiber) was mature, and the position of 50 MMF in the inter-office trunk optical fiber communication system was quickly replaced by single-mode fiber. Since then, 50 -MMF has turned to the field of data transmission, mainly used in LAN. At that time, in order to reduce the cost of LAN system as much as possible, people widely used low-priced light-emitting diodes (LEDs) as light sources instead of expensive semiconductor lasers (LD). The divergence angle of LED is much larger than that of LD, but the core diameter and numerical aperture of 50φ-MMF are relatively small at that time, which is not conducive to efficient coupling with LED. In order to make the connection and coupling easier, and make the optical power coupled into the optical fiber more powerful, gradient multimode optical fibers with larger core diameter and larger numerical aperture have been developed internationally, such as 62.5/ 125, 80/ 125,100140. Shortly thereafter, most of the market share of 50 MMF was replaced by the newly emerging 62.5/125mm gradient multimode fiber. However, due to various reasons such as high bending loss, high manufacturing cost and special cladding diameter, 80/ 125, 100/ 140 and other multimode fibers have not been widely used. During this period, multimode optical fiber gradually replaced the traditional copper wire and coaxial cable, and became the preferred physical medium for modern ultra-high-speed LAN systems.
In the third stage, from 1996 to 2002, the research and development of multimode fiber entered the latest active period. It is estimated that the active period will last until 20 10. In the meantime? The local area network system is developing at an ultra-high speed above GB/S. IEEE adopted Gigabit Ethernet standard1998 in June; ? In June 2002, the 10Gb/s Ethernet standard was just passed. This ultra-high-speed LAN system must use laser as light source and a new generation of high-performance multimode fiber. In addition to the 10Gb/s Ethernet standard, there are many industrial standards that will adopt the new generation of multimode fiber (see Table 3).
Corning of the United States, OFS of Lucent and Draka of the Netherlands have all introduced this new generation of multimode fiber samples. The promulgation of various industrial standards provides a unified foundation for the development, production and application of this kind of optical fiber, and more optical fiber manufacturers will invest in the development and production of a new generation of multimode optical fiber. It is predicted that after 2002, it will be the golden age for multimode fiber to achieve greater development.
3. Development and application of multimode optical fiber for beacon communication.
WRI is the first company in China to develop timely glass multimode optical fiber by MCVD process. Table 4 summarizes the early development of WRI multimode fiber.
Since then, WRI has increased its investment in the research of PCVD equipment and technology, and has successively completed the research of PCVD equipment and rod-making technology (1990). Research on Manufacturing Technology of Large Preform by High Efficiency PCVD Method (1992): Long PCVD optical fiber preform manufacturing system research (1995) and other projects, and obtained a number of related patent authorization. The above research results greatly enrich the technical strength and development potential of WRI in multimode fiber.
1996, China issued and implemented the industry standard YD/T? WRI drafted 816-1996 multimode fiber with large core diameter and large numerical aperture. The promulgation and implementation of this standard has promoted the standardized development of the domestic data optical fiber market. Since WRI successfully developed the 62.5/ 125 data fiber and passed the ministerial appraisal in 1998 1, the fiber has been mass-produced on the self-made PCVD equipment and passed the appraisal. The products are of high quality and good reputation. In addition to supplying domestic demand, it is also exported to South Korea, India and other countries, which is welcomed by domestic and foreign users. The LAN system established by optical cable produced by WRI Data Optical Fiber Company is widely used in institutions, schools, factories and network companies. The economic and social benefits are remarkable.
Since the establishment of 1999, Fiberhome Communication has taken the industrialization of multimode optical fiber as an important task and implemented a leap-forward development strategy. First of all, in the original pilot plant, by improving equipment performance, adding new PCVD equipment and improving process technology, the annual production and sales ratio of 200 1 optical fiber 1999 increased by five times. At the same time, the newly-built optical fiber factory in Wuhan Optics Valley, China will be put into operation soon. In addition to mass production of single-mode optical fiber, the latest generation of PCVD equipment will be used to produce high-performance multimode optical fiber, and the production capacity will be increased by 4 ~ 5 times on the existing basis. ? In the research of a new generation of 50/ 125 multimode fiber, DMD measurement is an indispensable technology. Fiberhome communication is fully prepared. R&D personnel collected and studied relevant technical data, purchased DMD measuring equipment, and studied the process of eliminating RIP defects.
Four. Summary and prospect
This paper reviews the development of multimode fiber in the past 30 years. At present, it is the latest active period of multimode fiber research and development, and the application of multimode fiber in local area network and other short-distance communication systems has gone through more than 20 years. With the acceleration of the information process of human society, the transmission rate and capacity of these systems are also increasing rapidly. At high speed, compared with coaxial cable and copper wire, the technical and economic advantages of optical fiber cable are increasingly obvious. Therefore, the application of multimode fiber in local area network will continue to expand. ? In addition, due to the development of the new generation of 50/ 125 multimode optical fiber, the application of multimode optical fiber will not only be limited to local area network, but also be widely used for the interconnection of communication equipment in storage area network (SAN) and wide area network/metropolitan area network (WAN/MAN) exchange offices. The industry has shown great interest in studying various new technologies to improve MMF production capacity. Using these new technologies, it is possible to increase the effective bandwidth of MMF by dozens of times. It is predicted that there will still be some new technological breakthroughs after the new generation of multimode fiber comes out.
It is worth noting that in IEEE? Before the introduction of 802.3z Gigabit Ethernet standard, single-mode optical fiber was rarely used in LAN. While adopting multimode fiber, the standard also adds traditional single-mode fiber for transmission within 5 kilometers. ? In the newly released 10Gb/s Ethernet standard, the transmission within 40km also includes conventional single-mode optical fiber. It is predicted that with the upgrading of network speed and the expansion of network scope, more conventional single-mode fiber or even more advanced single-mode fiber, such as low water peak fiber, may be used. Some companies have introduced single-mode optical fiber data transmission solutions working at short wavelengths (850 nm and 1200 nm). Because the life of optical fiber network should be much longer than 10 years, in some practical projects, a hybrid optical cable of multimode fiber and single-mode fiber has been laid, and single-mode fiber has been used as dark fiber for future upgrade. A foreign company has introduced a new optical fiber sample that combines multimode fiber and single-mode fiber, which is called multimode-single-mode composite fiber (Combined? MM-SM- fiber). The fiber has a convex core refractive index distribution, that is, a single-mode core concentric with the multimode fiber protrudes from the center of the multimode fiber. When both ends of the optical fiber are connected with MMF, the optical fiber works in multimode mode; ? When both ends of the optical fiber are connected with SMF, the optical fiber works in single mode. Its characteristic is easy to upgrade to single mode.
In LAN environment, the total cost of multi-mode system is still lower than that of single-mode system at present and in the future. From 2000 to 20 10, the global market share of multimode fiber in LAN is about 70%, with an average annual growth rate of over 2 1%. In the future LAN market, multimode fiber will not only continue to compete with copper wire, but also with plastic fiber and single-mode fiber. This requires multimode fiber manufacturers to continue to improve productivity and reduce production costs, while actively adopting new technologies to develop new products and solutions that meet market demand. Fiberhome communication has a long and brilliant development history in multimode optical fiber, and has the advantages of integrating photoelectric subsystem-photoelectric device-optical fiber and cable, and has established a soaring platform. We believe that the optical fiber and cable industry of Fiberhome Communication Technology Co., Ltd. will forge ahead and create greater glories.