Fiber-optic cables

Fiber-optic cables High-speed data transmission

Data transmission via fiber-optic cables (FO) has many advantages. It enables data rates of up to 40 Gbps over routes that are many kilometers long, does not have a negative affect on adjacent cables and at the same time, is resistant to electromagnetic interference. The different fiber types (POF, PCF, GOF) and fiber categories OM1 to OM5 plus OS2 allow cabling concepts to be tailored to specific requirements.


  • Up to 90% thinner fiber-optic cables and lines compared to copper cables
  • No shielding concepts required due to metal-free transmission
  • Low material usage for passive cabling
  • Transmission of multiple signals in different wavelengths over the same fiber-optic cable with large transmission bandwidths
Principle of optical data transmission

Principle of optical data transmission

The principle of FO transmission

Fiber-optic (FO) cables transmit data in the form of light across long routes. To achieve this, the electrical signals at the transmitter are converted into optical signals and sent to the receiver through plastic or glass fibers. There, the transmitted light signals are converted back into electrical signals and then evaluated and processed.

The cables and lines are up to 90% lighter and thinner than copper cables, and yet enable longer transmission routes and higher data rates of up to 40 Gbps or more. At the same time, elaborate shielding concepts are unnecessary since the system is absolutely resistant to EMC and ESD interference due to metal-free transmission.

The materials used and the associated costs for passive cabling are typically lower compared to copper cabling. And wide transmission bandwidths with higher signal density provide the option to transmit several signals in different wavelengths via the same fiber-optic cable (multiplexing).

Data transmission in data centers

Fiber-optic cabling optimizes data transmission in data centers

Fiber-optic cables in use

Whether over short, medium or long distances, at speeds of less than 100 Mbps or up to 40 Gbps, or within bus or Ethernet structures, there is the right cable for fiber-optic data transmission for virtually any demand in industrial and semi-industrial automation. Even when used under harsh conditions such as those on wind farms, fiber-optic cables reliably complete their task.

That is why their applications range from use in vehicle technology and industrial cabling to Local Area Networks (LAN) in data centers and wide area networks. The key to cabling is selecting the right type of fiber and fiber category.

The right fiber for all applications Each type of fiber has its own specific application. The smaller the outer diameter of the fiber, the more delicate the fiber behavior is during assembly. Smaller fiber core diameters enable higher data rates and distances. Click on the turquoise spots for more information.

Interactive image map: Fiber core and cladding diameters of fiber-optic cables
POF for short transmission paths up to 70 m and up to 100 Mbps
In POF (polymer optical fiber) cables, both the core and the cladding are made of plastic. The typical core diameter is 980 µm; for cladding, it is 1,000 µm. With short transmission routes of up to 70 m and data rates of a maximum of 100 Mbps, depending on the active components, POF cables are used for automotive engineering or industrial cabling. The robustness and size of the fiber make it easy to assemble in the field. Due to high attenuation and dispersion, this fiber type is not suitable for high data rates or long distances.
POF for short transmission paths up to 70 m and up to 100 Mbps
PCF for medium transmission distances up to 500 m and up to 1 Gbps
PCFs (polymer-clad fibers) are plastic-coated fiber-optic cables made of glass. Known under various designations such as PCS (polymer-clad silica), HCS (hard-clad silica), and HPCF (hard polymer-clad fiber), these cables are robust and can be assembled easily. PCF fibers with a typical core diameter of 200 µm and a cladding diameter of 230 µm are often encountered in industrial cabling with medium lengths of up to 300 m and data rates of ≤100 Mbps. Other areas of application include automotive, sensors, and medical technology.
PCF for medium transmission distances up to 500 m and up to 1 Gbps
GOF multimode for long transmission distances up to 550 m at 10 Gbps
In GOF (glass optical fiber) multimode cables, the fiberglass has a core made of quartz surrounded by cladding of reflective glass. Multimode cables have core diameters of 50 µm or 62.5 µm. The larger diameter allows more light energy to be coupled at the beginning of the fiber, but attenuation is higher along the length of the fiber. That is why multimode fibers are mainly used in local area networks (LANs) and data centers, where they can handle transmission routes of up to 550 m with 10 Gbps.
GOF multimode for long transmission distances up to 550 m at 10 Gbps
GOF singlemode for long transmission distances up to 50 km and up to 40 Gbps
GOF (glass optical fiber) singlemode fibers have a much smaller core diameter of approximately 8 µm. For singlemode fibers, we differentiate between core diameter and field diameter. The field diameter depends on the wavelength. The larger the wavelength, the larger the field diameter. Since only one light mode can be transmitted in the fiber, a great deal of signal light can be fed into the fiber and transmitted. The fiber’s coefficient of attenuation in the transmission range is very low. Low attenuation and low dispersion are the ideal conditions for using singlemode fibers for distances of up to 50 km and data rates of up to 40 Gbps.
GOF singlemode for long transmission distances up to 50 km and up to 40 Gbps

In accordance with ISO/IEC 11801, fiber categories OM1, OM2, OM3, and OM4 have been internationally established for multimode fibers and OS1 and OS2 have been established for singlemode fibers. They indicate which transmission bandwidths and attenuation values a fiber has. Due to the constant increase in transmission bandwidths, the number of future categories, such as OM5 for transmission rates of up to 400 Gbps, is also growing.

Losses and fiber-optic cables

Attenuation is a loss of signal light intensity that occurs as light is being transported from the transmitter to the receiver. The goal is to transport signal light to receivers with as little attenuation as possible. There is a difference between the attenuation that occurs at a specific location and attenuation in relation to length, the attenuation coefficient. The attenuation coefficient for fiber-optic cables refers to a length of 1 km.

Attenuation in fiber-optic cables
Attenuation in fiber-optic cables
Attenuation in fiber-optic cables
Attenuation in fiber-optic cables

Insertion and coupling losses can occur when the light is fed into the fiber by the transmitter or also through plug and splice connection along the route and at the receiver. Many things can cause these types of losses. One frequent cause is contamination on connector faces.

Coupling different core diameters in one link also leads to losses. Splice connections created with fusion splicing are very low-attenuation, with values below 0.1 dB. Longitudinal, transverse, and angled fiber end offsets can also lead to attenuation. Scratches and cracks on face surfaces not only increase attenuation, but can also damage the coupled face surface on the opposite side. Assembly errors such as a notch from the outside on fiberglass during assembly can also lead to attenuation or even breakage at a later point in time.

Attenuation in fiber-optic cables

Minimum bending radii are listed in the fiber-optic cable data sheets. Values below them cause losses, and the attenuation increases accordingly. Part of the light escapes from the core. Several years ago, GOF fibers that can be bent to very small angles were developed for multimode and singlemode fiber-optic cables. Bending radii of under 10 mm can be achieved with these fibers, which are less sensitive to bending. The fibers are internationally specified in the relevant standards in the IEC 60793-x and ITU-Tx series. The advantage is that they can be routed under poor installation conditions in buildings, residential units, and industrial environments.

Attenuation in fiber-optic cables

The material used to manufacture fiber-optic cables and the manufacturing process itself could cause attenuation. Causes can be material-specific or the result of contaminants, for example. Fiberglass is manufactured such that it is optimized for specific wavelength ranges. In these wavelength ranges, attenuation is as low as possible. The attenuation coefficients that apply for these wavelengths are listed in the data sheets accordingly. The fiber-optic cables should be operated within those ranges.

Dispersion in fiber-optic cables

Signal distortion during the runtime from transmitter to receiver

Effects of dispersion

Dispersion also limits the data rates and transmission bandwidths of fiber-optic cables. Dispersion is when signals are deformed. During the runtime from transmitter to receiver, the signal loses amplitude and the edges continuously drop off. When two signals are sent back to back, the recipient can no longer tell if there is one signal or two.

This results in transmission errors. The higher the transmission bandwidth and the longer the link length, the more important it is to focus on low dispersion. For long singlemode routes in particular, this is a key factor for reliable, error-free transmission quality.

FO portfolio from Phoenix Contact

Comprehensive product portfolio for fiber-optic cabling

Products for FO-based data cabling

Phoenix Contact provides an extensive FO cabling and FO data connectors product portfolio. Alongside a comprehensive selection of cables and the matching connection technology, device connections, patch panels, couplings and distributors for DIN rails round out the portfolio.

• Transmission speeds up to 40 Gbps
• Solutions for IP20, IP65/IP67, and IP68
• For all common fiber types
• For all common interfaces
• Maximum protection against the effects of EMC and ESD

Ideally suited for these industries

Fiber-optic cables enable a wide range of applications in the following application areas:

Modern connection technology lays the foundation for smart building automation

Intelligent device connections in building automation

Smart buildings are also changing the device connection: Applications are networked decentrally. Standardized and at the same time scalable device connections are required if building automation to succeed.

Device manufacturer in the process of selecting connection technology for their application

Device manufacturers

Connection solutions are becoming increasingly smaller and more robust. Modern connection technology from Phoenix Contact for industry and infrastructure gives device manufacturers a high degree of freedom when planning and developing their applications.

E-paper on data connectors
Our FO portfolio of data connectors
Would you like to browse through our FO range? – The e-paper on data connectors also provides an overview of the FO connections for you.
Open the e-paper
Visualization with hand and key for data connectivity