Characteristics of the development of fiber optic cable technology
1. The development of the network puts new demands on optical fiber
The Next Generation Network (NGN) has sparked many ideas 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 world of light at the transport level, and the wireless world at the access level. The next-generation transport network requires higher speed and larger capacity. This is not a fiber-optic network, but the development of high-speed backbone transmission also puts new demands on optical fiber.
(1) Expanding the transmission capacity of a single wavelength
At present, the transmission capacity of a single wavelength has reached 40 Gbit/s, and research on 160 Gbit/s has begun. The transmission of more than 40 Gbit/s will impose certain requirements on the PMD of the optical fiber. At the ITU-TSG15 meeting in 2002, the United States has proposed to introduce a new fiber category (G.655.C) for the 40 Gbit/s system, and proposes In-depth discussion of some of the problems in its PMD transmission, perhaps a special 40Gbit / s fiber type will appear in the near future.
(2) Realizing ultra long distance transmission
Non-relay transmission is ideal for backbone transmission networks. At present, some companies have been able to use the chromatic dispersion technology to achieve 2000-5000km non-electrical relay transmission. Some companies are further improving the fiber index, and Raman optical amplification technology can greatly extend the distance of light transmission.
2. New fiber optics are constantly appearing
In order to meet the needs of the market, the technical indicators of optical fiber are constantly improving, various new types of optical fibers are constantly emerging, and major companies are stepping up development of new varieties.
(1) New high-capacity long-distance fiber for long-distance communication
It is mainly a new type of G.655 fiber with large effective area and low dispersion maintenance. Its PMD value is extremely low, which can easily upgrade the capacity of the existing transmission system to 10 to 40 Gbit/s, and facilitate distributed distribution on the fiber. The MANN effect is amplified to greatly extend the transmission distance of the optical signal. For example, Corning’s new PureModePM series of optical fibers utilize polarization transmission and composite cladding for DWDM systems above 10Gbit/s, which is said to be well suited for the development and application of Raman amplifiers. Alcatelcable’s TeralightUltra fiber has been reported to have a single channel of 40 Gbit/s and a total capacity of 10.2 Tbit/s. Other companies have developed optical fibers with large dispersion and large effective area, which have improved the requirements of nonlinear indicators and simplified the scheme of dispersion compensation. They have shown good performance in long-distance non-regeneration transmission, and long distances in submarine cables. The effect in communication is also very good.
(2) New low water peak fiber for metropolitan area network communication
Metropolitan area network design needs to consider simplifying equipment and reducing costs, and also consider the possibility of non-wavelength division multiplexing (CWDM) applications. The low-water peak fiber greatly expands the bandwidth in the extended band of 1360 to 1460 nm, which greatly optimizes the CWDM system, increases the transmission channel, and increases the transmission distance. Some metropolitan area networks may not only require low water peaks of the fiber, but also require the fiber to have a negative dispersion value. On the one hand, it can offset the positive dispersion of the light source optical device, and on the other hand, the negative dispersion fiber and the G.652 fiber can be combined. Or G.655 standard fiber, use it to do dispersion compensation, thus avoiding complex dispersion compensation design and saving cost. If Raman amplification technology is adopted in the metropolitan area network fiber in the future, such a network will also have obvious advantages. But after all, the specifications of the metropolitan area network are not very mature, so the specifications of the metropolitan area network fiber will change with the change of the metropolitan area network mode.
(3) New multimode fiber for local area network
Due to the rapid development of local area networks and customer premises networks, a large number of integrated wiring systems have also adopted multimode fiber instead of digital cables, so the market share of multimode fiber will gradually increase. The reason why multimode fiber is used is because the transmission distance of the LAN is short. Although the multimode fiber is 50% to 100% more expensive than the single mode fiber, the optical device can be equipped with LED, and the price is much cheaper than the laser tube. Moreover, multimode fiber has a large core diameter and numerical aperture, which is easy to connect and couple, and the corresponding components such as connectors and couplers are also much cheaper. ITU-T has not yet accepted the 62.5/125μm multimode fiber standard, but it is still widely used due to the development of LAN. The ITU-T-recommended G.651 fiber, which is a 50/125μm standard multimode fiber, has a small core diameter and is difficult to couple and connect. Although it has some applications in some European countries and Japan, it is used in North America. Most countries in Europe rarely use it. In response to these problems, some companies have improved and developed a new 5O/125μm fiber-graded (G1) fiber, which is different from the gradient index profile of the traditional 50/125μm fiber core. The distribution has been adjusted to match the use of two windows at 850 nm and 1300 nm. This improvement may find a new market for 50/125 pm fiber in LAN applications.