The Use Of Optical Cables and Optical Fibers In Data Center

Structured cabling system DPC (Data Center) should support the work of various applications, including those that are only planned to use in the future. Speed in data centers are increasing due to the use of server virtualization technology and the use of this technology leads to an increase in requirements for the cable system. Using an optical cable in data centers is primarily due to the fact that a large number of reliable and working technologies and solutions that use as a medium for data transmission singlemode and multimode fiber , the transmission of large information flows and the distance is much more than it can reach copper cables.

Optical cables have no problems with EMC and crosstalk occurring between the twisted pairs and copper cables, which makes use of copper cables in data centers .

The diameter of the optical cable is less than copper and it allows the use of cable channels for the optical cable of smaller sections, which allows better use of space in data center, reduce the costs of cable channels. Also reduces the load on the mount cable channel.

Using an optical cable increases the efficiency of the cooling system: optical cable run cool, creates fewer obstacles when placing cable channels under the raised floor, electric power consumption of the active ports of equipment on the optics, copper below.

A well-designed cabling in data center allows the owner of the data center to solve the problem of scaling data center, with no problems in connecting with a new network and equipment storage. And to solve the problem of scaling the data center without using an optical cable is impossible.

Multimode Or Singlemode Fiber In The Data Center

In the data center in accordance with the requirements and recommendations of all standards are allowed to use two types of optical fibers: single-mode fiber and multimode fiber.

Single-mode fiber is cheaper than multimode fiber, but due to the fact that the ports are active equipment to fiber mode are much more expensive, the single-mode fiber is not widespread in the data center . Most single-mode fiber is used for connecting services from the operator, who delivers it to the room of the cable entry point in the network interface. In contrast to SCS for commercial buildings in the cable system, data center allowed the use of single-mode fiber in the horizontal subsystem. Using a single-mode optical fiber may be required when filing service from service provider directly to the port of the active equipment installed in the machine room in the hardware distribution area.

Most of the data center equipment is used with ports that support the work of multimode optical fiber as the price of the port of active equipment for multimode fiber is cheaper than the ports of the active equipment for single-mode optical fiber.

The type of multimode fiber depends on the size of the data center and the applications that will be used at the time of design and in the future.

TIA EIA 942 Standard allowed the use of multimode optical fibers with core and shell 62.5/125um and 50/125 categories of OM1, OM2 and OM3. However, the TIA/EIA-942 standard recommend using multimode fiber optimized for use with a laser with a ratio of broadband multimode fiber is not less than 2000 MHz • km at 850 nm, that is recommended for multimode fiber 50/125 categories of OM-3.

European standard EN 50173-5 for SCS in the data center do not permit the use of 62.5/125 micron multimode fiber and even 50/125 OM1 category, and also as the standard TIA/EIA-942 recommend using OM3 multimode fiber category.

The international standard ISO / IEC 24764, which is not yet approved and which is designed with the latest requirements for SCS in the data center , generally spelled use in a data center of a multimode fiber does not lower OM3 category, ie the data center , which is designed should meet international standard requirements.

The use of OM3 multimode fiber category ensures data transfer rate 10Gbit/sec at a distance of 300 meters, however, if the insertion loss in the optical channel at a distance will not exceed 1.6 dB.

Multimode fiber category OM4

American and international working committees on standardization shall consider the adoption of a new category of multimode optical fibers. TIA / EIA working document TIA-492AAAD, which will include the specification of the characteristics of the fiber category OM4. And the international working group is working on a standard IEC IEC 60793-2-10 with a new type of multimode fiber. While the new category OM4 multimode fiber has not been accepted, but working groups have agreed on the minimum value of the coefficient of bandwidth for multimode optical fiber of a new category for VCSEL laser with 850 nm radiation. Coefficient of bandwidth for new category OM4 must be at least 4700 MHz * km.

OM4 multimode fiber category will allow data centers to move into the future without any problems on the use of 40 and 100 Gigabit Ethernet technology, allowing you to work 10Gbit/sec system at distances up to 550 m and reduce the requirements for insertion loss in the channel. A requirement for the insertion loss at the limit for the standard distance is very difficult to reach when using an optical cable with multimode fiber category OM3 and OM2 particular category.

The Design Of Optical Cable In The Data Center

The choice of design of optical cable depends on the number of optical fibers, method of installation, place gaskets and other technical requirements and conditions.
In order to reduce the diameter of the optical cable, it should not be used with fiber optic cables having a secondary buffer coating (external diameter of the fiber in the secondary buffer coating 900 micron).

If the number of fiber optic cable is more than 24 ex-tape, it is better to use fiber-optic cables, as they have a smaller diameter with the same number of optical fibers. This reduces the size of the cable channels or use them more effectively.

It is recommended to use the distribution cables in the data center, rather than the usual cables, which are used for the manufacture of optical cables and jumpers. The concept of “distribution cable,” defined by the standard ICEA S-83-596 and related to the level of mechanical strength of optical cable. Electrical cables can be routed on the tray and ladders.

If the optical cable is laid on top of the telecommunications closet 42U, it is usually the additional protection of the optical, however, if the optical cable will be run in places where access will take the technical staff (for example, under the raised floor), then you may need an optical cable with extra protection. The design of the optical cable may include additional reinforcing the strength of materials – Kevlar thread, fiberglass rods, etc.

If the data center must meet the requirements of the fourth level of reliability (Tier 4), you may need to use an armored optical fiber cable to ensure a certain level of protection for cabling infrastructure.

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