Fibre optic cables

Fibre optic cables as a transmission medium for optical signals are becoming increasingly popular when transmitting data in Ethernet networks. Depending on the application area and type of fibre optic cable, they can achieve maximum speeds over long distances and, thanks to their expansion, are also the perfect argument for sustainable networking. We will clarify for you what fibre optic cables are, how they differ and which benefits the use of glass fibre cables offers.

What is a fibre optic cable?

Fibre optic cables are cables for transmitting signals in the form of light using fibres made of quartz glass or polymer optical fibres (plastics). The optical signals (light signals) are transmitted over long distances.

These are often referred to as glass fibre cables. To be more precise, however, a glass fibre cable is a special type of fibre optic cable whose fibres are made from glass as the basic material. Fibre optic cables, on the other hand, is the generic term for all cables that conduct light, which also includes the glass optical fibre.

How are fibre optic cables constructed? 

Fibre optic cables are available with fibre cores made of quartz or plastic fibres. The optical transmission of signals in a fibre optic cable works according to the principle of “total reflection”. To achieve this, an optically thinner sheath (cladding) is placed around the light-conducting core. At the interfaces between the core and the sheath, the light is reflected and thus guided through the fibre optic cable. The higher refractive index of the fibre material used in the core compared to the sheath material is decisive for total reflection.

In order to mechanically protect the surface of the optical sheath (cladding), a plastic coating is also applied as the outer sheath. This protects the cable against external influences.

Fig. 1 Structure of a fibre optic cable (cross-section and longitudinal cross-section)






1: Coating

2: Optical sheath (cladding)

3: Optical core

Which fibre optic cables are available at LAPP?

In our LAPP portfolio, we offer three overarching fibre types for fibre optic cables:

They are essentially different in terms of the material used in the core (core) and sheath (cladding), as well as the maximum distances and transmission speeds that can be achieved as a result.

In the following chapter, we will therefore highlight the important differences.

POF – plastic fibre

Polymer optical fibres, or POF for short, are all made of plastic. Thanks to the optical polymer fibres, also known as plastic fibres, POF fibre optic cables are resistant to external electromagnetic radiation and do not even emit any electromagnetic radiation.

POF fibre optic cables are therefore very easy to process and are particularly suitable for use in cable ducts with power cables, for example. Due to their flexibility, fibre optic cables made of optical polymer fibres are suitable for fixed installation indoors or for flexible use in drag chains.

For use in the industrial Ethernet sector, we at LAPP offer POF fibre optic cables for special network protocols such as PROFINET and ETHERNET/IP.

POF fibre optic cables are typically made of PMMA (acrylic), an all-purpose resin as the core material, which is why they are also known as PMMA optic fibre. Similar to glass fibre optic cables, POF transmits light through the core of the fibre.

Properties of a POF fibre optic cable

Fig. 2 Design of a POF fibre optic cable



PCF fibre:

  • P980/1000

POF applications:

  • SIMPLEX (single-core application)
  • DUPLEX (two-core application)


1: Core: 980 μm

2: Sheath (cladding): 1000 μm

3: Insulating layer (coating): 2200 μm

The POF fibre type specifies the core and sheath dimensions (core/cladding). Because of their simple assembly and considerably lower procurement costs, POF fibre optic cables are often preferred to PCF or GOF fibre optic cables, particularly in short-distance applications.

One major disadvantage of POF fibre optic cables, on the other hand, is the high attenuation values, which limit the maximum fibre length to around 100 to 120 m without reinforcement.

PCF – Plastic Cladded Glass Fibre 

Polymer Cladded Fibres or PCF are made of plastic cladded glass fibres and are also known as "hard-cladded silica optical fibres (HCS)”.

PCF fibre optic cables are primarily used in industrial and medical applications and offer the ideal cost-benefit balance between plastic fibre optic cables (POF) and glass fibre optic cables (GOF). A PCF fibre optic cable is slightly more demanding to install, but offers significantly higher bandwidths and better attenuation compared to POF fibre optic cables. This enables you to achieve higher transmission speeds and a better range with a PCF fibre optic cable.

Our PCF fibre optic cables guarantee reliable and very fast data transmission even over transmission distances of up to 500 metres, e.g. in large factories.

Figure 3Structure of a PCF fibre optic cable



PCF fibre type:

  • K200/230

PCF applications:

  • SIMPLEX (single-core application)
  • DUPLEX (two-core application)


1: Core: 200 μm

2: Cladding: 230 μm

3:Insulating layer (coating): 500 μm

The PCF fibre type specifies the core and sheath dimensions (core/cladding). PCF fibre optic cables also offer simple and fast assembly technology, making them easy to assemble in the field.

You can generally replace existing POF systems with PCF fibre optic cables without replacing the transmitter/receiver and thus connect larger distances, which is particularly economical when upgrading the transmitter/receiver.

GOF - Glass Optical Fibres

Glass Optical Fibres, or GOF for short, are made entirely of glass. When we refer to “glass fibre cables”, we generally refer to this type of fibre. Unlike POF and PCF fibre optic cables, the optical glass fibre is not easy to assemble. A special splicing robot is required to process GOF fibre optic cables.

A GOF fibre optic cable is therefore the “real” glass fibre cable, as in this case both the core glass and the sheath glass are made of quartz glass or silicon oxide.

GOF fibre optic cables are often referred to as "Silica Clad Silica (SCS)" or "All Glass Fibre (AGF). They have very low attenuation and therefore, especially in single-mode, a high data rate (up to 40 Gbps) and range (up to 40 km).

Figure 4 Design of a GOF fibre optic cable




GOF fibre type:

  • Single-mode fibre, SM, E9/125 OS2
  • Multimode fibre, MM, G50, G62.5/125 OM


1: Core: 9.50 or 62.5 μm

2: Cladding: 125 μm

3: Insulating layer (coating): 250 μm

Due to its low attenuation, a single-mode GOF fibre optic cable is well suited for large distances. The fibre core (core) has a diameter of 9 μm here, while the diameter of the sheath (cladding) is 125 μm (notation: 9/125).

With a multi-mode GOF fibre optic cable, on the other hand, light of different wavelengths is transmitted. Due to higher attenuation, multi-mode glass fibre cables are more suitable for shorter distances or for the local network. Here, the fibre core (core) has a diameter of 50 μm (or 62.5 μm) and the sheath (cladding) has a diameter of 125 μm (notation 50/125 or 62.5/125).

Would you like to see a complete overview of the dimensions of our fibre types, attenuation, distances and transmission speeds?

You can find a complete overview here.

What is the difference between fibre optic cables and copper cables?

Fibre optic cables are used to transmit optical signals in the form of light using thin plastic or glass fibres. The data is transported by light particles, so-called photons. In copper cables, on the other hand, the data is transported through the cable in the form of electrons.

Fibre optic cables have significant advantages compared to copper cables, which is why they are indispensable in today's transmission technology and can even be seen as the transmission medium of the future.

Advantages of fibre optic cables compared to copper cables:

Fibre optic cables are resistant to electromagnetic interference as optical signals are not exposed to inductances, capacitances or resistances and therefore hardly suffer any losses even over long distances.

The bandwidth of an individual fibre optic cable is around 60 THz. By adding additional wavelengths to an almost unlimited colour spectrum, enormously high bandwidths can be achieved and the capacities can be increased at any time.

Electrons that enable data to be transferred in copper conductors move at around one percent of the speed of light. By contrast, photons that transport the data in fibre optic cables achieve speeds of around 70% of the speed of light. With fibre optic cables, this is due to the fact that due to the refraction index in the conductor, the photons need a little longer to reach their destination and therefore never reach the exact speed of light.

But this small comparison alone shows what speeds exist between copper conductors and fibre optic cables.

In addition to the important and substantial advantages, fibre optic cables also have a few disadvantages compared to copper cables.

The disadvantages of fibre optic cables compared to copper cables:

Fibre optic cables are more compact in terms of dimensions, lighter in weight and quicker with data transmission, but this also entails higher acquisition costs in production and connectors.

Depending on the fibre type, special splicing robots are sometimes required for connecting and assembling the fibre optic cables.

The use of fibre optic cables usually also requires the use of compatible hardware that enables the full speed potential to be exploited.

The benefits also include the unavailable possibility of intermediate storage of optical signals, as this makes it difficult to intercept them. However, this also means that optical signals for storage, amplification or further processing always have to be converted into electrical signals first.

Where are fibre optic cables used?

Fibre optic cables are now an indispensable part of data transmission technology. Due to the high range and transmission rates, they are increasingly replacing electrical transmission with copper conductors in many areas.

Due to their resistance to external electromagnetic influences, fibre optic cables are mainly suitable for installation in the immediate vicinity of power cables, electric motors, pumps, inverters and frequency converters. The advantage of this is that there is no signal interference and data loss in network communication.

However, it is not just in data transmission technology that fibre optic cables have their trumps, they are also used in energy transmission as light cables for transporting laser beams for material processing in laser cutting systems or in medical engineering as image or light conductors for microscopes, endoscopes and for the lighting of devices and buildings.

Other applications include fibre optic sensors, spectrometers or other optical measuring devices in which fibre optic cables are used for measuring technology to determine distance or transmit data.

At LAPP we offer you fibre optic cables for almost every industry and application. We have a wide range of halogen-free, oil-resistant and heat-resistant cables for different fibre types for indoor or outdoor installation. Assembled, field-configurable and with a wide selection of accessories and tools specifically for you.

What do you need to note when selecting a fibre optic cable? 

The right fibre optic cable for your application depends on several factors. In addition to the application area and the resulting properties in terms of robustness, durability and movement and torsion tolerance of the cable, the distance between the transmitter and receiver, as well as the installation conditions and data speed, are decisive factors in your decision-making.

Pay particular attention to the following criteria:

  • Cable outer sheath material
  • Fibre type and cable mode
  • Maximum cable distances achievable
  • Attainable transmission speeds of the cable

For example: fibre optic cables with a PU outer sheath are halogen-free, heat-resistant and oil-resistant, making them ideal for areas at risk of fire or for use in contact with cutting and cooling oils.

Depending on the design, these as POF fibre optic cables, e.g. achieve speeds of up to 100 Mbps at a maximum distance of 50 m and can be assembled in the field without any problems. By contrast, PCF fibre optic cables can achieve these speeds even at a distance of 100 m. Glass fibre cables (GOF) in turn achieve speeds of up to 40 Gbps in single-mode and distances of up to 40 km, but cannot be assembled directly on site without special splicing robots.

You can quickly and easily find out which LAPP products are perfect for your application in our fibre optic configurator.

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