SDH

This term is quite a versatile term and it has many meanings attached to it, and if one is given this term asked to tell its meaning, he would be confused, as the meaning of this term changes with respect to the situation and the place it is used in. This article deals with this term with respect to the networking world and in this world of networks; this term stands for Synchronous Digital Hierarchy. 

This technology is an international standard for the multiplexing protocols that transfer multiple digital bit streams over fiber optic cables, by making use of the Lasers or LEDs or light emitting diodes, however, the lower data rate can be transferred via electrical interfaces, and there is no need for them to travel through the optic cables, if these cables are loaded with transporting the high speed data. This technology was introduced to the networking world to replace an older technology which performed the same job.

The name of this older technology was PDH or Plesiochronous Digital Hierarchy. The reason this technology was released in place of PDH was to allow the organizations to transport larger amount of calls and data traffic over the same fiber optic cables without any synchronization problems. In North America, there is another technology, named SONET or Synchronous optical Networking, and it is equal to the SDH technology and performs the same role, however, SONET is their standard not SDH.

The SDH technology has a standard rate of data transmission and data cannot travel any faster than that speed. The speed of data transfer in SDH is 155.22 Mbps and this speed is often referred as the STS-3 at the electrical level and STM-1 for SDH. Another thing to note is that the speed STM-1 is equivalent to the Optical Carriers levels – 3 in the SONET technology.