Optical fibre are mainly used to transmit information over long distances and with high bit rates. Their benefits are numerous: the signal transmitted on the fiber is not disturbed by any electromagnetic wave created by power cables or electric machines. It also provides more security, as these cables can be fully dielectric. Besides, they provide a weight and space saving due to their small diameter, only 250 μm.
An optical fiber is made up of three main parts: the core, the cladding and the coating. In the center, the “core” is made of doped silica and
is surrounded by the “cladding”, made of natural silica.
The light signal propagates along the core and the signal is reflected on the surface between the core and the cladding.
An acrylic “coating”, generally made of two layers, is protecting the sillica part against abrasion during installation.
Different Fibre Types
Multimode fibre are used for Local Area Networks (LAN) where the network links can be up to 2,000 meters. Two standard sizes of core are offered: 62.5 μm and 50 μm (with better performances). Multimode fibre have a graded index profile to reduce the dispersion of the signal during the transmission. The high size of the core is interesting for easy connection and does not require high cost test equipment.
Singlemode fibre are able to transmit over longer distances. The installation is more delicate as they have a smaller core of 9 μm. This implies more precise connectors and test equipment.
On a global network point of view, although the cost of multimode fibre is more important than the singlemode’s, the complete system is more economic.
Indeed Multimode fibre are used with cheap transmission components LED(1) or VCSEL(2) whilst Singlemode fiber perates with more expensive LASER.
(1) LED: Light Emitting Diode
(2) VCSEL: Vertical Cavity Surface Emitting Laser
Optical fibre are used at specific wavelength. Multimodes fibre are mainly used at 850 nm and 1,300 nm and Singlemode are used at 1,310 nm and 1,550 nm. The attenuation performances are better at the higher bandwidth with consequently improved transmission performances.
Optical fibre can be provided with different characteristics. Indeed the performance need for fibre in patch cord or fiber over one kilometer link are obviously different. The fibre choice is based on optical parameters such as attenuation, bandwidth performances and chromatic dispersion.
Different international standards are available to describe the optical fiber characteristics: ITU G652 for Singlemode fiber and IEC 60793-2-10 for Multimode fibre are worldwide references.
| G 50/125 G | 62.5/125 E | 9/125 | |
| Attenuation coefficient at 850 nm | 2.8 dB/km | 3.3 dB/km | |
| Attenuation coefficient at 1,300 nm | 0.8 dB/km | 0.9 dB/km | 0.4 dB/km |
| Attenuation coefficient at 1,550 nm | 0.3 dB/km | ||
| Minimum modal band with at 850 nm | > 200 MHz.km | > 200 MHz.km | |
| Minimum modal band with at 1,300 nm | > 200 MHz.km | > 200 MHz.km | |
| Numerical aperture | 0.200 } 0.02 | 0.275 } 0.02 | |
| Dispersion at 1,285 – 1,330 nm | .≤ 3.5 ps/nm.km | ||
| Dispersion at 1,550 nm | .≤ 18 ps/nm.km | ||
Optical Fibre connectors
Nexans are able to preassemble optical fibre with plugs, we can provide this service in our factory or on site. A fibre optic connector is a non permanent join between two fibre.
In the optic connector systems gives a plurality to connector, they are not compatible among on another. It is recommendable to use ST connector or E2000 connector for reel and flexible cables with integrated fibre optics.
A high quality connector is required to achieve the best possible transfer of light signal between fibre.
ST Connector (standard)
This type of connector is suitable for both multimode fiber and singlemode fiber. The ST connector and the bajonet-holder is the most popular used connector worldwide.
E2000 Connector
An E2000 connector is a special connector with high
level attenuation coefficient. This connector is suitable for multimode fiber and singlemode fiber.
Due to the code system, this connector is very user friendly and can also be fit as a single connector or duplex connector
The built-in filler cap protects the ferrule against contamination. The filler cap open/close during the connector plug in/out.
