We are continuously asked questions about different aspects of Structured Cabling. See below for some of those most frequently asked.
Q. Multimode & Singlemode Fibre Cables
A Multimode -
Multimode Optical fibre is suitable for local area networks (LAN’s) because it can carry enough energy to support all the subscribers to the network. Relatively inexpensive LED transmitters can be used, which reduces the overall installation cost. The preferred cable size recommended bythe ISO/ANSI standards is 62.5/125 micron fibre. 50/125 cable can be used and is getting evermore popular. It must be remembered that all components actve and passive will also need to be rated 50/125
Singlemode -
Generally regarded as the long distance/ national carier optical fibre (50km+). As LAN networks require more bandwidth, Singlemode is becoming more popula as part of the installation despite the increased cost. The prefered cable is 8-10/125
Q. What are the different classes when referring to ISO/IEC 11801?
A. ISO/IEC 11801 defines five classes for link performance:
Class A - For speech band and low frequency applications specified to 100kHz
(no longer recognised by the ISO)
Class B - For medium bit rate data applications specified to 1Mhz
(no longer recognised by ISO)
Class C - For High bit rate data applications specified to 16Mhz (Category 3)
Class D - For very High bit rate applications specified to 100Mhz (Category 5/5e)
Class E - Standards for applications specified to 250Mhz (Category 6)
Class F - Standards for applications specified to 600Mhz (Category 7)
Optical Class - For high and very high bit data rate applications, specified to 10 MHz and above. Generally bandwidth is not a limiting factor in customer premises.
Q. What is an APC connector
A. APC is the abbreviation for Angled Physical Contact. This is a style of fibre connector with a 5-15 degree angle on the connector tip for the minimum possible back reflection.
Q. What is Ethernet?
A. When transmitting a signal, a computer needs a Protocol (language) in order to communicate with other devices. The Internet uses TCP/IP, whereas LAN’s (Local Area Networks) tend to use the Ethernet Protocol. Information is sent across the network in ‘packets’ using the binary language (1’s and 0’s). In order to send a packet along a copper cable the signal needs to be converted into a voltage pulse (this equates to a 1 in binary being represented by a 1 volt pulse and a 0 being represented by a ½ volt pulse). A computer needs to have a link to other computers before it can send or receive information, and this normally requires the use of ‘Active Equipment’ such as Hubs or Switches.
One Bit = 1 or 0 (Binary Format)
Eight Bits = One Byte = A letter, number or symbol
One Kilobit = 1000 Bits
One Megabit = 1,000,000 Bits
The transmission speed of a signal is expressed as bits per second (bps), therefore a 56Kbps modem is capable of 56,000 bits per second (9 thousand bytes). Most modern networks are capable of running at 100Mbps (100,000,000 bits per second, 12.5 million bytes)
A category 5E/6 network can run at speeds of up to 1000Mbps (1000,000,000 bits per second 125 million bytes). This is around 17,800 times faster than a 56K modem.
Q. What is Fibre Optic cable?
A. An Optical Fibre Cable basically consists of a solid rod of pure glass enclosed inside a ‘cladding’. The cladding protects the fibre and helps prevent light loss. By sending millions of pulses of light every second, Optical Fibre is capable of transmitting more information, for longer distances, in less time than conventional copper media. It is not affected by electricity, water or radio interference and is not a conductor, therefore is safe to run externally. Optical Fibre is also a very secure media.
Optical Fibre is available in two formats:
MULTI-MODE (MM): A type of fibre with a comparatively large central core, typically 62.5 or 50 microns, surrounded by a larger outer cladding, typically 125 microns. Most frequently used as a network backbone or to link building or networks.
SINGLE-MODE (SM): A type of fibre with a comparatively small central core, typically 8 or 10 microns, surrounded by a larger outer cladding, typically 125 microns. Most commonly, used for long distances and high speeds by national carriers such as BT and CATV franchises.
Q. What are the Cabling Specifications for Optical Fibre?
A. Optical Fibre is rated as core and cladding size e.g. 62.5/125 has a core diameter of 62.5 microns and a cladding diameter of 125microns. There are two types of Optical Fibre available for the structured cabling system. Multimode and singlemode. primarily multimode is the preferred fibre due to the use of cheaper LED transmitters but singlemode (as backbone) can be offered as an alternative if very high bandwidth applications are to be used in the future.
Q. Why use Optical fibre?
A. Optical Fibre has the ability to work in harsh/industrial areas without the need for additional protction against electrical interference or damp environments. It can be installed internally ro externally without the need to change cable types or specifications.
Advantages for using Fibre cable over Copper cabling are-
Capacity -
Optical fibres carry the signal with less eergy loss than copper cables and does so at a greater bandwidth. Bandwidth equates t odata carrying capacity therefore more channels of information can be carried over longer distances with fewer repeaters.
Size & Weight -
Optical fibres are much thinner and lighter than copper cables; this means there is less space required in ducting and trunking when installing a structured system.
Security-
Optical fibres are almost impossible to tap information without detection, an ideal media for banks and information sensitive environments. It is immune from radio signals, ignition systems, lighting etc so they can be safely routed through explosive or flammable atmospheres and potentially hazardous sites.
Running costs-
the main consideration for choosing fibre when installing in communication sectors such as domestic cable TV networks and telecomms’ is the electricity bill. Athough copper coaxial cable can handle the bandwidth requirement over short distances a copper system will consume far more power than fibre simply to carry the signals.