内容发布更新时间 : 2024/5/3 1:41:04星期一 下面是文章的全部内容请认真阅读。
分布并不遵循跨越核心直径的理想抛物的变化。这些光纤在位于光纤的轴处有一个不连续的小指标,以防止近轴射线被及时有效的传达。这些是受到最少的色散影响的射线，然而它却是允许使用高信号率的低等分散。扩展带宽多模光纤，已经制定了一个改进的折射率分布。他们又提高了在多模光纤上可传播的吉比特以太网的距离到大约1km。VCSEL激光器有沿光纤中心近轴射线发射的能力，它是使用扩展带宽光纤的理想助手。
传统上，铜网络比他们的光学相应物便宜，但是，当数据速率增加时，安装这些媒介的费用将聚合。这可能发生在2.5 Gbs速率。 未来
显然,对未来的所有需求预测是困难重重的,我们必须依赖于过去的经验。当处理水平网络时，错误判断将带来昂贵而持久的后果。但通常只有一个得到正确的机会，因为水平布线的寿命是10年或更多点。通过对比的方式，PC机的寿命约为2 - 3年，而以太交换机3 - 5年。鉴于此,正确的选择水平布线是至关重要的。
对于10Mbs工作，铜3类电缆很足够了。 对于100Mbs工作，铜5类电缆是必需的。 对于1 Gbs工作，铜5e类电缆是必需的。
对于10 Gbs的工作，延长工作50/125μm的光纤电缆是必需的。 如果，作为趋向建议，我们也许期待在布线的寿命之内10Gbs的操作，然而，事实上，水平布线是昂贵的改变，我们应该尽我们所能设法使当前的装置作为所谓“面向未来的”。因为改进的铜缆布线提供的解决方案很可能是短暂的，也很可能和光纤一样昂贵，所以我们需要在所有的新工作考虑提供光纤。如果因为目前的成本问题，在任何给定的项目并不实际安装光纤，但至少，在布线内容中应该预留光纤的空间，以适应未来的应用。一种实现这一没有铺设任何实际的光纤的方法就是是使用“气吹光纤”导管。这是一种藉以沿着传统布线的输送管道安装光纤的技术。他们随后可能会投入使用，通过使用压缩空气将光纤吹入预装管道下到目的地。这具有下列优点： 对装修有最小的干扰；
对大厦的员工正常工作模式有最小的干扰。当在零碎的基础上且和现有的线路同行需要或预算许可时，光纤可以提供额外的带宽。它允许将开支推迟。
气吹光纤是“原始”（直径约0.1毫米）的光纤。它是由预安装管道
保护的免受损坏。它比传统的由熟悉的塑料护套包装的光纤电缆更便宜。
如果环境改变或发生损坏，光纤的等级可以被改变。老化的光纤能够快速方便地回收,并且被不同的光纤取代。
输送管道是小的，并且可以通过传统的线缆包含进行运载。损坏的管道可以切去进行修理，并且损坏的部分也可以用新的管替换它。 因为光纤具有成熟的优势技术,大大优于电噪声免疫、本质电气安全,优越的带宽能力,数据高度安全性，通过长距离携带数据的能力允许在“主干”的拓扑结构中使用，所以它的用途或潜在的用途应该在所有新线缆施工时认真被考虑。
如果历史告诉我们什么，那就是没有任何解决方案是“面向未来的”。
外文原文：
The Future of Structured Cabling
The JHMI Premise Distribution Plan will be consistent with standards specified by the AT&T Premise Distribution System and the International Standards Organization's Integrated Services Digital Network. This includes wallplates, wire for the horizontal distribution and the voice/data wiring closet modular cross connection equipment.It is recommended that wire runs be less than 230 feet from the voice/data wiring closet to the wall station. Horizontal Distribution Wire & Wallplates
AT&T type %unshielded twisted pairs shall be used. Each voice/data wall station will receive four type \cables. Each 4-pair \cable will be terminated in an standard RJ45 (8-position) jack so that each wallplate will need to house four RJ-45 jacks. Vertical Distribution Wire & Voice/Data Wiring Closets
The wiring closets are generally located on each floor of a building.Existing buildings must be evaluated on a case-by-case basis since some of the older buildings have limited space. For new buildings, each closet should be large enough to accommodate a minimum of two standard 19\computer racks. Each of the major premiseplans recommends mounting electronics in 19\racks. The larger electronic components will require full frame computer racks. These racks will support the ISDN, Ethernet and Token Ring components. In addition, cross connection panels will be required for the telephone wiring, terminal wiring, Ethernet connections and future Token Ring.
Two separate sets of cross connection panels will be required. The data wires will terminate in one set of panels and the voice wires in another.This will segregate functions and minimize confusiondue to two separate organizations maintaining the same set of wires.The data wires will be patched into the appropriate rack-mounted data hardware (i.e. 3274 controllers, Ethernet Bridge boxes, etc.) and the voice wires will be patched into the rack-mounted voice hardw
are (where possible). However if needs change, the base wiring plant will be able to support either the voice or the data technology. Modular cross connection equipment provides easier long-term maintenance and reconfigurability. There are many configurations available from third party sources such as Mod-Tap, Nevada Western and Ortronics. At this point, however, it is most likely that JHMI will go with an AT&T solution.
A minimum of two ThickWire Ethernet segments (Belden 9880 or equivalent) will be run through each building to the interconnecting basements. Loops should be left on each floor for future installations.Ethernet cable must have readily available access (i.e. not run in conduit) to insure future use.
A minimum of one 62.5/125 micron fiber riser will be installed in each building riser for future data communications use. Sufficient bulk voice communications riser cable should be run to meet the current and projected requirements. Again, the wiring of existing buildings will need to be evaluated with feasibility in mind. In many buildings the basement wiring closet will act as an intermediate distribution frame back to the main wiring frame. Inter-building linkswill probably be run using fiber optic cable especially to increase the bandwidth of the data communications networks.
A Structured Cabling System (SCS) most simply stated is based on following a standard methodology defined by EIA/TIA 568 specifications when planning and installing network cabling for commercial buildings. The purpose of this standard is to specify a generic telecommunications cabling system for commercial buildings that will support a multi-product, multi-vendor environment. It also provides information that may be used for the design of telecommunications products for commercial enterprises.
The EIA/TIA-568 standard includes EIA/TIA-568-B.1 General Requirements,EIA/TIA-568-B.2 Copper Cabling Requirements, EIA/TIA-568-B.3 Fiber Cabling Requirements.
Industrial Considerations
So what changes for the industrial environment related to the