【導(dǎo)讀】從靠近長城站的語音/數(shù)據(jù)布線建議線路部署小于230. AT＆T的“D”類非屏蔽雙絞線應(yīng)被使用。將達到四對“D”類電纜的要求。每4對"D"類線纜將被匯聚在一個。因為某些更舊的大廈座位有限，根據(jù)具體情況必須對原有房屋進行評估。對于新樓宇，每個小房間應(yīng)。該至少可以容納兩個標準19"機架。其中每項主要的前提計劃推薦在。19"機架上安裝電子設(shè)備。較大的電子元器件，需要全幀計算機機架。這些機架將支持ISDN，以太網(wǎng)和令牌環(huán)組件。數(shù)據(jù)線將端接于其中一組。面板，而語音線則在另一塊。由于兩個分開的組織維護同一組相同的。線纜，這將分離作用并且使混亂減到最小。但是，如果需求發(fā)生變化，基本接線廠。商將能夠支持，無論是語音或數(shù)據(jù)的技術(shù)。模塊化的交叉連接設(shè)備提供長期的維護和可重構(gòu)性更容易。再次，現(xiàn)有建筑物的布線將需要考慮到可行性評估。在非常高的數(shù)據(jù)速率對UTP銅纜布線的使用有內(nèi)在的局限性。

　　

【正文】 e VCSEL laser. The refractive index profile of ordinary multimode fibre does not follow the ideal parabolic variation across the diameter of the core. These fibres have a small index discontinuity located at the axis of the fibre that prevents paraxial rays from being transmitted efficiently. These are the rays that suffer least dispersion and it is low dispersion that permits higher signalling rates to be used. Extended bandwidth multimode fibres have been developed with an improved refractive index profile. They have increased the distance over which gigabit ether may be transmitted by multimode fibres to about 1km. The VCSEL laser is capable of launching paraxial rays along the centre of an optical fibre and is the ideal plement to the use with extended bandwidth fibre. Traditionally, copper works have been cheaper than their optical counterparts, but as data rates increase, the costs of installing these media will converge. This is likely to happen at rates of about Gbs. The Future Obviously, all predictions about future requirements are fraught with difficulty and we must rely heavily on past experience. Errors of judgement when dealing with the horizontal working are expensive and have long lasting consequences. There is usually only one chance to get it right as the lifetime for horizontal wiring is 10 years or more. By way of contrast, the lifetime of a . is about 2 3 years and that of an ether switch 3 5 years. In view of this, it is crucial that the right choices are made for horizontal cabling. For 10 Mbs working, copper category 3 cabling is quite adequate. For 100 Mbs working, copper category 5 cabling is required. For 1 Gbs working, copper category 5e cabling is required. For 10 Gbs working, extended working 50/125181。m fibre optic cabling is required If, as trends suggest, we may expect 10 Gbs operation within the lifetime of the wiring and in view of the fact that horizontal wiring is expensive to alter, we should try to make any current installation as so called futureproof as we can. As the solution offered by improved copper cabling is likely to be transient and is likely to be just as expensive as fibre, we need to consider the provision of fibre for all new work. If, because of current cost, fibre is not actually installed in any given project, at the very least, space provision in the cable containment ought to be made in order to accommodate its future adoption. One way of achieving this without laying any actual fibre is to make use of blown fibre conduits. This is a technique whereby conduits for fibres are installed alongside traditional wiring. They may subsequently be brought into operation by using pressed air to blow fibres down the preinstalled conduits to their destination. This has the following advantages: There is minimal disturbance to decoration. There is minimal disruption to the normal working patterns of the building39。s staff. The extra bandwidth that fibre offers can be provided on a piecemeal basis and in parallel with existing wiring when need or budget permits. It allows expenditure to be deferred. Blown fibre is raw fibre (about diameter). It is protected from damage by the preinstalled conduits. It is cheaper than traditional fibre cable where fibres are encased in the familiar plastic sheath. The grade of fibre can be changed if circumstances change or if damage occurs. Old fibres can be quickly and easily withdrawn and replaced by different ones. Conduits are small and can be carried by traditional cable containment. Damaged conduit can be repaired by cutting out and the damaged section and replacing it with new tube. As fibre has all the advantages of proven technology, far superior immunity to electrical noise, intrinsic electrical safety, superior bandwidth capability, a high degree of data security and the ability to carry signals over long distances permitting the use of collapsed backbone topologies, its use or potential use ought to be seriously considered for all new cable installations. If history teaches us anything, it39。s that no solution is futureproof