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What is OTN system?


The principal advantages of fiber optic cable as compared to copper cable are well known and include almost perfect electromagnetic isolation, light weight, compact size, excellent transmission security and substantially better bandwidth/distance performance.

Fiber optic technology has led to a new generation of private and industrial networks providing much larger bandwidths, high reliability and increased maximum geographical coverage.

OTN or “Open Transport Network”, is a transmission system specifically conceived for the needs encountered in industrial environments. OTN is based on the latest fiber optic technology to fulfill the requirements of said environments.

An industrial network is characterized by heterogeneous communication requirements.

You will find all types of communication, such as voice, data, video, audio, etc.

Moreover, the critical nature of all applications in case of incidents imposes requirements regarding back-bone reliability and resilience, whereas the economic constraints imply a low network operating cost. The industrial environmental conditions also dictate the equipment’s level of robustness. Finally, the industrial domain prefers systems that are easy to install and easy to use, while being able to operate and develop over 10-15-year life cycles.

As such, OTN can fulfill all these requirements for such environments.


1.1 What is OTN?

OTN is exactly what its name implies:

Open                     It can handle nearly all existing physical interfaces via its interface cards.

Transport            It carries different types of information (such as voice, data, digital video and LAN) completely transparently throughout the network.

Network              It is based on fiber optic technology in a future-proof network infrastructure, over virtually unlimited distances.

OTN is the ideal solution for mixed environments that are found in many stretched networks in e.g. the transportation environment of metros, railways, light rail, motor-way systems, mines and airports, along oil, gas or water pipelines, in electricity distribution networks and in the petrochemical and chemical industries.

OTN, the Secure Investment

In this so called “Information Age”, communications infrastructures have to cope with rapidly changing requirements (e.g. increasing video applications).

OTN grows smoothly with these new requirements and services. Its easy migration capability from one environment to another by simply adding interface cards, makes it a system that can be used for years to come.

Different bandwidth requirements are met by the respec-tive members of the family, i.e. the 150 Mb/s, 600 Mb/s, 2.5 Gb/s and 10 Gb/s versions, with smooth upgrading capabilities from one version to another.

OTN Advantages

The OTN system features many advantages when com-pared to dedicated networks for voice, data, LAN and video transmission, or compared to the traditional digital transmission systems in use today:

  • the economies of different services sharing equipment and fiber;
  • easy implementation in any environment, safeguard-ing the investments made in the existing equipment;
  • LANs can be interconnected at full bandwidth;
  • different applications have a dedicated amount of bandwidth reserved for them on the network
  • transparent connections, making the network independent of changes in the higher layers of the various protocols;
  • easier and simpler communications wiring, and hence easier management and maintenance.
  • easy to use network management system requiring only limited training of staff

OTN System Adaptations

OTN comes with an extensive suite of interface cards. New industry standard and specific interfaces are developed as specific needs arise or standards gain momentum. OTN is the ideal platform for such developments.


1.2 OTN Features

Maximum Network Availability

System unavailability is restricted to a minimum, as the ring automatically recovers in error situations, also in the case of dual errors. This reconfiguration time is so short, that e.g. a telephone call is not interrupted while the ring is reconfiguring. During network expansion, adaptation or repair, the network remains operational thanks to:

  • Automatic Reconfiguration: The network reacts autonomously to fiber cuts by switching to the standby ring or by performing loopbacks.
  • Universal Nodes: Each node is a potential master node for network synchronization, i.e. each node can generate frames to which the remaining network synchronizes. When the active master node drops out, its functions are immediately taken over by another node. Also in the case of dual errors, resulting in two separate networks, a node automatically takes over the master node’s tasks in both networks.
  • Automatic Startup Procedure: The network starts up automatically after a power failure, a ring reconfiguration, or after a node is switched back into the ring.
  • Interface Cards: When an interface card is switched off, it can be inserted into or removed from the node without disabling the node. Only links set up via this interface card will be disrupted, whereas the rest of the network remains operational.

Direct Access to the Network and Guaranteed Bandwidth

OTN guarantees direct access to the network at any time avoiding long access times and enabling real time applications. Each application has its own virtual connection because the transmission capacity on the backbone is allocated in a semi-permanent way, which means that the allocated bandwidth is always available for that application, independently of the other applications running on the network. OTN provides the optimum mix of fixed bandwidth (constant bit rate) for real-time traffic and packet based Ethernet traffic.

Reliable Communication

OTN guarantees reliable communication in office as well as in industrial and transport surroundings. OTN uses optical fibers as transmission medium, offering a number of advantages over conventional copper wire conductors.

  • The resistance to electromagnetic interference (interruptions by transmitters and radar signals, by switching large currents for powering machines, adjacent cables, high-voltage cables, etc.) ensures very reliable communication in both office and industrial surroundings.
  • The low BER (Bit Error Rate) of the optical fibers (BER = 10-10 … 10-12) compared to conventional cabling (BER = 10-6) ensures very reliable communication.

Diversity of Interface Cards

OTN provides a wide range of interface cards and can therefore be used for diverse applications. This diversity of interface cards eliminates the need for additional transmission equipment, such as protocol converters and conversion equipment.

OTN features interface cards for:

  • Data transport (e.g. RS232, RS422, RS485)
  • Local Area Networks (e.g. Gigabit Ethernet, Fast Ethernet)
  • Telephony purposes (e.g. analog and digital 2-wire and 4-wire voice links, E1, T1)
  • Public Addressing
  • Video applications (video distribution and video monitoring, CCTV)

Geographical Extensiveness of the Network

The OTN network allows spanning very large distances (up to 1000 km (622 miles) or more).

Flexible System

  • Flexible Bandwidth Allocation: The high available bandwidth allows the multiplexing of a range of low and high-speed applications. New applications can be implemented by adding inter-face cards, which are allocated part of the available bandwidth (transmission channels) of the backbone.
  • Simple Network Adjustments: The network can be easily expanded thanks to the modular network structure. If free interface slots are available, a node’s functionality can be expanded by inserting one or more new interface cards. The net-work can be expanded through the addition of a new node into the ring. When the ring is interrupted, the network automatically reconfigures, which ensures the communication between the connected equipment.

Fast Error Detection and Simple Network Recovery

Any ring operation and interface card errors are reported centrally, and in part also locally.

  • OTN Management System (OMS): The system’s central error reporting lies within the OMS. The OMS constantly monitors the network and receives data related to the operation of the different nodes and the interface cards installed. The alarm messages indicate the nature and location of errors, if any, so these can be located and solved immediately.
  • Visual Indications: Local error reporting takes place in the nodes. LEDs on the front panel of the network cards indicate the ring and node operation, whereas LEDs on the interface cards indicate the operation, status and setting of the interface card concerned. An alphanumerical display for error location is provided on the BORA.
  • Modular Structure: Once an error has been located by OMS alarm mes-sages or visual indications on the cards, it can be quickly solved by replacing the card.


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