The Modern Communications Cabling Environment

Range of Services
Telecommunications cabling on customer premises may be required to support the following range of services:

  • Voice (Analog Telephone)
  • Voice (Digital Telephone such as ISDN)
  • Digital Data (LAN, inter-LAN and WAN connected)
  • Alarm
  • Security (Surveillance, access control)
  • Environmental Control
  • Paging, Music Distribution
  • Video Distribution

Some of these services require connections to or through a carrier’s PTN (Public Telephone Network). These connections may involved twister pare, coaxial cable, optical fiber or satellite media.

Transmission media used to provide the range of services within a building or between buildings (Campus Style) may involve twisted pair, coaxial cable, optical fiber and microwave or infra-red transmission. A minimum requirement at a commercial work area has become a telephone and a data connection for the PC which has an insatiable ‘appetite’ for information. The PC is demanding higher and higher data rate connections to satisfy its information ‘appetite’ , putting heavy demands on the transmission performance of supporting cable media.


Mandatory Standards

The following standards are mandatory for a customer premises installation:

Local Authority and/or Carriers
All cable and cabling components shall conform with requirements of local rules. This conformity is indicated by inclusion in Local Authority and/or Carriers Certified Components Listing (CCL) or, in the case of components in the transmission path such as sockets and termination modules by the issue of a Local Carrier permit number for that component.

The cabling installation shall meet all requirements of the wiring rules of the local wiring rules and in particular the separations and segregation requirements from hazardous services.

Industry Recommendations:

The following standards are industry recommendations but become legally binding in civil law if included in a work contract:

ISO 11801
Layout, dimensioning, component transmission quality specification, installation practices, compliance testing; ISO 11801 covers transmission quality up to Category 5 in accordance with ISO standard ISO 11801.

Pathway design (conduit, tray, ducting, service pole, in false ceiling, under computer floor, (etc) and associated installation practices, design of telecommunication closets, equipment rooms and entrance facilities.

Local Authority and/or Carriers
Telecommunications installations – coaxial cables for telecommunications applications – cables for connection to carrier’s networks.

Local Authority and/or Carriers
Telecommunications installations – optical fiber cables for telecommunications applications – cables for connection to carrier’s networks.

Local Authority and/or Carriers
Telecommunications installations – twisted pair cables for telecommunications applications – cables for connection to carrier’s networks.

Telecommunications installations – Administration of communication cabling systems – Basic requirements.

International Standard

International Standard Organization (ISO):

ISO 11801 – Information Technology – Generic Cabling for customer premises cabling.

This standard includes class D applications to 100 MHz (Cat 5 equivalent) and is the basis for category 5 transmission quality.

United States Standard

Electrical Industry Association/Telecommunications Industry Association (EIA/TIA)

EIA/TIA 568A 568B
Cabling layout, provisioning, component specification, installation, testing to category 5 transmission quality.

An updateto EIA/TIA 568 to category 4 and 5 transmission quality in connecting hardware specification and installation.

An update to EIA/TIA 568 to category 4 and 5 transmission quality of cables.

Documentation and recording practices for cabling installations.

EIA/TIA 678 – TSB67
Transmission performance specifications for field testing of unshielded twisted pair cabling systems (1995 – in draft form) including tighter specifications for the hand held cable testers.

Local Authority and/or Carriers Compliance

These authorities sets the rules and regulations which ensure a safe environment for:

  • the carrier’s personnel
  • the customer/user of telecommunications equipment
  • the carrier’s equipment

Their regulations also ensure an interface free environment for the carrier’s equipment and inter-operability between the carrier’s equipment and the customer’s equipment connected to the carrier’s network.

Local Authority and/or Carriers compliance is required of all cabling which is on the customer’s side of the network boundary and directly or indirectly connects to a carrier’s network – Local Authority and/or Carrier’s calls such cabling ‘customer cabling’.

Local Authority and/or Carriers compliance means:

  • installation/maintenance of customer cabling can only be carried out by Local Authority licensed cablers or cablers working under the supervision of Local Authority licensed cablers
  • all customer cable shall be a Local Authority approved type (CCL Listed) in accordance with Local Authority and/or Carriers markings.
  • all hardware used in the transmission chain of such cabling shall be Locally approved to EIA/TIA TSB 40A either holding a Local permit or listed in the CCL of approved components.
  • customer cabling installation/maintenance shall be carried out in accordance with Local Authority and/or Carriers rules.
  • all customer equipment (telephones, modems, fax machines etc) directly or indirectly connected to carrier’s network shall exhibit local permits, unless isolated from the carrier’s network by an Authority – permitted line isolation unit (LIU).

Fiber Optic Application

Fiber has the ability to propagate light launched into it with very low loss. In addition, virtually none of the light escapes the fiber along its walls, provided the recommended minimum bending radius specifications are not violated.

Fiber optics are generally constructed from a very pure form of glass, although some forms of low loss plastic fiber are currently under development. Signals used for transmission on fiber are generally in the red/infra-red range of the spectrum. This is because the materials currently being used for fiber manufacturing exhibit lowest losses in this range of wavelengths.

The ability of fiber to contain and propagate the light signal comes about from Snell’s Law of Refraction. Snell’s Law basically states that total internal reflection occurs for light travelling in a medium when it encounters a boundary to a medium of lower refractive index, at an angle greater than what is known as the critical angle. Fiber optic is manufactured in such a manner that the refractive index of the material is greatest in the center of the core and decreases towards the edges. Hence light travelling inside is totally reflected whenever it approaches the edges of the fiber.

The importance of not exceeding the fiber’s minimum recommended bending radius specifications can be seen. If this bending radius is exceeded, the critical angle criterion will not be met and some of the light will escape. This will manifest itself as a loss in the circuit. On long underground routes, it is important to ensure that if the fiber cable is directly buried, it is not placed under excessive stress by the fill material. Pressure from the fill material can cause localized sharp bends in the fiber cores. This can cause un-budgeted loss increases due to escaping light, to a point where the cable becomes unworkable. It then becomes a very expensive excercise to dig it up again to rectify it.