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Reliable production processes or the protection of life and limb today depend significantly on the availability of the data connection. Depending on the protocol, topology and number of active devices, redundancy procedures now ensure switching times of a few milliseconds. However, if several errors occur simultaneously, an interruption of the data communication is preprogrammed. With the optical bypass "X-light" EKS Engel will increase the availability of fiber-optic cables.

eks20213The industry-standard technology is protocol-transparent, ie it supports both Ethernet and all fieldbuses and numerous interfaces such as RS-485. The optical bypass works with devices from other manufacturers and can be integrated into ring and line topologies.

Especially for reasons of cost, devices such as Ethernet switches, fieldbus converters or programmable logic controllers are put through their paces by many manufacturers before delivery. However, errors during operation can never be completely excluded. The main causes are hardware and software problems or power failure.

Conventional protective measures have only limited effect

The latter can be compensated with an uninterruptible power supply (UPS) at least for a while. The software is back-protected with extensive evaluation and validation, automated test procedures as well as structure, function and so-called black box tests. In the case of hardware, redundancy is used by using devices as well as plugs and lines in duplicate. At the same time, the network will be designed twice as well. This achieves a kind of hot standby effect: If one device or network fails, it switches to the other one.

However, this strategy is complex and therefore expensive. Therefore, the ring topology was developed. Here the data communication always runs in one direction and in case of a disturbance in the other one. So the function is retained. Together with redundancy procedures, which ensure fast switching times, the ring topology forms, so to speak, the premier class of failure safety. In contrast to the line, this topology copes with a single point of failure, ie the failure of a network subscriber. However, if another fails (Multiple Points of Failure), rings are overwhelmed. So that it does not get that far, networks can be monitored by means of monitoring systems. They show the status of the active components and - like "Fiber View" - the state of the individual optical fiber links, that is: too high attenuation.

eks30213The optical bypass technology, which has previously been used primarily in the classic IT environment, goes one step further. It starts directly with the network subscribers. This can be any device that has an optical input and output. If a network participant fails, the bypass ensures that the data communication to the neighboring participants is maintained. Therefore, only the application that is controlled by the failed participant is affected. The rest of the network, on the other hand, remains in physical condition even with multiple points of failure. This also applies if the bypass, which can either be supplied with power via the subscriber to be protected or a separate power supply, no longer receives power.

Bypass technology also works in case of power failure

With the optical bypass technology fiber optic links are physically switched as soon as an error occurs at the respective network participants. The principle resembles a railway turntable, which is held by a strong electromagnet and automatically switches when there is no electricity flowing. That's why the bypass technology works without voltage. Since this technology takes place at the physical level of the network, it is also protocol-transparent and manufacturer-neutral.

The x-light technology is also suitable for use in harsh industrial environments, for example in terms of temperature range as well as shock and vibration resistance. This device is connected in parallel with the network node via two optical duplex inputs and outputs. If this fails, its fault relay sends a signal to the electrical input of the x-light and thus activates the bypass function. Thereafter, the data is not forwarded to the defective subscriber but to the next in the network. The participant is virtually physically bridged. In order to be able to switch it on again later, for example after booting, the switch-on delay is individually adjustable.

With the optical bypass, however, networks can not only be protected against the effects of hardware and software errors or failure of the power supply or fall short of a previously defined value, but also deliberately remove subscribers from the network. For this purpose, a voltage is applied to the electrical input. Thus, the respective subscriber is completely switched off and can no longer send and receive uncontrolled without having to pull the fiber optic connectors. Because that may lead to problems, such as dirt particles, which get into the connection.

Immune to electromagnetic fields

Otherwise, however, optical fibers have a number of advantages, for example when high data rates are required and / or long distances must be bridged. Because 100 km or 10 Gbit / s are no problem with this medium. Furthermore, light is not affected by electrical or magnetic disturbances, which is why fiber optic cables can also be installed in the immediate vicinity of power lines or other electromagnetic sources. Since they are also made of electrically non-conductive material, the data is always transmitted via an electrical insulator. This means that there are no equipotential bonding currents via fiber-optic cables, which are particularly feared in the case of extensive installations. Even with lightning strikes there is no risk of destruction for the connected devices.

An optical bypass pays off especially where a power failure can lead to financial losses, harmful effects on the environment or even endangerment of people. Examples include traffic control systems, petrochemical plants and wind farms. In addition, the targeted decommissioning of network subscribers opens up new possibilities for maintenance and service of machines and plants or their temporary shutdown.

Since the x-light is designed exclusively as a bypass, it can also be easily retrofitted.

Picture above: Optical bypass technology, which works in a similar way to a railway switch, maintains data communication to the neighboring subscribers in the event of a network subscriber failure.

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