A self-healing ring, or SHR, is a telecommunications term for loop

Loop (graph theory)

In graph theory, a loop is an edge that connects a vertex to itself. A simple graph contains no loops....

 network topology, a common configuration in telecommunications transmission

Transmission (telecommunications)

Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...

 systems. Like roadway and water distribution systems

Water supply network

A water supply system or water supply network is a system of engineered hydrologic and hydraulic components which provide water supply. A water supply system typically includes:# A drainage basin ;...

, a loop or ring is used to provide redundancy. SDH

SDH

SDH may refer to:* Synchronous Digital Hierarchy, in telecommunications* Secure Digital Host Controller, in computing* Saradhna, a railway station in India* The Shubnikov-De Haas effect, also see Fermi surface...

, SONET

Sonet

Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...

 and WDM systems are often configured in self-healing rings.

Description

The system consists of a ring of bidirectional links between a set of stations, typically using optical fiber

Optical fiber

An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...

 communications.
In normal use, traffic is dispatched in the direction of the shortest path towards its destination.
In the event of the loss of a link, or of an entire station, the two nearest surviving stations "loop back" their ends of the ring. In this way, traffic can still travel to all surviving parts of the ring, even if it has to travel "the long way round".

A second break in the ring may divide it into two sub-rings, but in such a case each sub-ring will remain functional.

Advantages

Self-healing rings offer high levels of resilience at low cost, since it is often geographically easy to take multiple paths across the landscape and link them up into a ring with very little extra fibre length.

Recent submarine communications cable

Submarine communications cable

A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean....

s are typically built in pairs, to function as a self-healing ring.

Very high resilience systems are typically built on interconnected meshes of self-healing rings.

Another example of a self-healing ring network technology is the FDDI local-area network.

Resilient Packet Ring

Resilient Packet Ring

Resilient Packet Ring , also known as IEEE 802.17, is a standard designed for the optimized transport of data traffic over optical fiber ring networks...

is a new technology for packet-switched self-healing ring networks.

These types of rings mainly used for saving high rate traffic flowing in Telecom networks.