What is Optical Fiber ?



Optical fibre is the most efficient technology to transmit data at the speed of light, with virtually unlimited bandwidth.

Technical principle.

With the size of a hair (250 micrometers), the optical fibre is made of a silica heart surrounded by a plastic sheath in which an optical signal transmitted by a laser diode carries data at the speed of light.

Dark fibre has now become the indispensable support of high-speed transmission for businesses:

  • Cloud access;
  • Interconnection of local area networks;
  • Connection of remote sites;
  • Data centre back-up;
  • Use of any telecommunication protocol (IP, FiberChannel …)

Fibre type mainly used is single mode G652 that guarantees good quality data transmission.
It is possible to multiplex wavelengths and thus transmit over 100 signals simultaneously on the same fibre, each at 10 Gbps or more.
Signal attenuation and transmission constraints define the architecture to be implemented: distances over 50 km are possible by regeneration of the transmitted signal: one can thus go around the earth in a few seconds.

A big advantage of optical fibre is that there is no signal interference with electro-magnetic waves.

Different types of optical cables

Optical fibres are grouped into tube (modulo 6 or 12 fibres) and placed in protective cables (anti-rodent, anti-acid …). The cables can contain up to 512 FO. Cables can be laid in ducts, tunnels, sewers…

Network Design

RATP Connect relies on RATP ‘s transport network to organize its network which is therefore strongly meshed and dense.
It provides connection points every 300 m and has 70,000 km of fibre installed.