Technical development and thinking of the hottest

Technical development and thinking of optical fiber and communication cables

1.1 the development of network puts forward new requirements for optical fiber

next generation network (NGN) has triggered many views and debates. Some experts predict that no matter how the next generation network develops, it will reach three worlds, namely, the IP world at the service level, the optical world at the transmission level and the wireless world at the access level. The next generation transmission requires higher speed and larger capacity, which is not the case with optical fiber, but the development of high-speed backbone transmission also puts forward new requirements for optical fiber

(1) expand the transmission capacity of a single wavelength

at present, the transmission capacity of a single wavelength has reached 40 gbit/s, and 160 gbit/s has been studied. More than 40gbit/s transmission will put forward certain requirements for optical fiber PMD. At the ITU-T SG15 conference in 2002, the United States has proposed to introduce a new optical fiber category (g.655.c) to 40gbit/s system, and it is suggested to conduct in-depth discussion on some problems of unnecessary losses caused by its PMD transmission. Maybe a special 40gbit/s optical fiber type will appear in the near future

(2) realizing ultra long distance transmission

relay free transmission is an ideal backbone transmission. At present, some companies have been able to adopt dispersion homogeneous technology to realize 2000 ~ 5000km relay free transmission. Some companies are further improving the optical fiber index, and adopting Raman optical amplification technology can greatly extend the optical transmission distance

(3) adapt to the application of DWDM technology

currently 32 × 2.5gbit/s DWDM system has been used, 64 × 2.5gbit/s and 32 × 10gbit/s system has been developed and made good progress. The extensive use of DWDM system puts forward higher requirements for the nonlinear index of optical fiber. ITU-T's standard (g.650.2) for nonlinear properties and test methods of optical fibers has also been completed recently. When the nonlinear test indicators of optical fibers are clear, corresponding indicators will be put forward for the effective area of optical fibers, especially for the nonlinear characteristics of G.655 optical fibers

1.2 the subdivision of optical fiber Standard promotes the accurate application of optical fiber

2000 World Telecommunication Standards conference approved the reclassification of the original G.652 optical fiber into G.652 a. G.652.8 and g.652 C Class 3 optical fiber; Divide the G.655 optical fiber into G.655 A and g.655 B two types of optical fibers. The subdivision of this optical fiber Standard promotes the accurate use of optical fibers. While refining the standard, it also improves the index requirements of some optical fibers (for example, the tolerance of some optical fiber geometric parameters becomes smaller), defines the different index requirements for optical fibers used in different network levels and different transmission systems (for example, the provisions of PMD value), and puts forward some new index concepts (such as "dispersion longitudinal uniformity"), It has played a good role in the rational use of optical fibers. The revision of all these suggestions, the emergence of sub suggestions and the drafting of new sub suggestions mean that there are some improvements or important improvements in fiber classification, indicators and testing methods; It marks the improvement of optical fiber quality or the adjustment of application direction, which is a new trend of optical fiber technology worthy of attention

1.3 new optical fibers are emerging.

in order to meet the needs of the market, the technical indicators of optical fibers are constantly improving, and various new optical fibers are emerging. At the same time, major companies are stepping up the development of new varieties

(1 it is difficult for the market demand of non-ferrous metal products to increase significantly) the new high-capacity long-distance optical fibers for long-distance communication

are mainly some new G.655 optical fibers with large effective area and low dispersion maintenance. Their PMD value is very low, which can easily upgrade the capacity of the existing transmission system to 10 ~ 40gbit/s, and facilitate the use of distributed Raman amplification on the optical fiber, so that the transmission distance of optical signals is greatly extended. For example, the pure mode PM series of new optical fibers launched by Corning company uses polarization transmission and composite cladding for DWDM systems with more than 10 gbit/s, which is said to be very suitable for the development and application of Raman amplifiers. The teralight ultra fiber launched by Alcatel cable has been reported to have a single channel transmission length of more than 100km of 40Gbit/s and a total capacity of 10.2 Tbit/s. Some companies also develop optical fibers with negative dispersion and large effective area, which improves the requirements of nonlinear indicators and simplifies the dispersion compensation scheme, showing good performance in long-distance non regenerative transmission and good effect in long-distance communication of submarine optical cables

(2) new low water peak optical fiber for metropolitan communication

in the design of metropolitan area, it is necessary to consider the simplification of equipment and cost reduction, as well as the possibility of the application of non wavelength division multiplexing technology (making the reading between 10% and 90% of the full scale CWDM). The bandwidth of low water peak optical fiber in the extended band of 1360 ~ 1460nm is greatly expanded, so that the CWDM system is greatly optimized, and the transmission channel is increased by 3. The ultra long travel can fully meet the testing of ultra large deformation rate materials; Long transmission distance. The design of some metropolitan areas may require not only the low water peak of the optical fiber, but also the negative dispersion value of the optical fiber. On the one hand, it can offset the positive dispersion of light source optical devices. On the other hand, it can be combined with G.652 optical fiber or G.655 standard optical fiber to make dispersion compensation, so as to avoid complex dispersion compensation design and save costs. If Raman amplification technology is used in metropolitan fiber in the future, this network will also have obvious advantages. But after all, the specification of metropolitan area is not very mature, so the specification of metropolitan optical fiber will continue to change with the change of metropolitan mode

(3) new multimode optical fiber for local area

due to the rapid development of local area and user station, a large number of generic cabling systems also use multimode optical fiber to replace digital cable, so the market share of multimode optical fiber will gradually increase. The reason why multimode fiber is selected is that the local transmission distance is relatively short. Although multimode fiber is 50% - 100% more expensive than single-mode fiber, its supporting optical devices can choose light-emitting diodes, which is much cheaper than laser tubes. Moreover, multimode fiber has a large core diameter and numerical aperture, which is easy to connect and couple, and the corresponding connectors, couplers and other components are much cheaper. ITU-T has not accepted 62.5/125 so far μ M-type multimode fiber standard, but due to the needs of local development, it is still widely used. The g.651 fiber recommended by ITU-T is 50/125 μ M standard multimode fiber, its core diameter is smaller, and its coupling and connection are relatively difficult. Although it has some applications in some European countries and Japan, it is rarely used in North America and most European countries. In view of these problems, some companies have made improvements and studied