Compare and contrast for SDH & SONET OAM

This Topic is legacy now but just to keep reader aware about the basic concepts, compiling  all together SONET/SDH here.

• Bellcore  defines GR.253 (SONET) and  ITU-T defines G.691 (SDH)
• SONET means Synchronous Optical NETwork
• First North American Fiber-Optic Telecommunications Standard to overcome the limitations of the traditional asynchronous network.
• Formulated by the Exchange Carriers Standards Association for the American National Standards Institute
• Incorporated into the Synchronous Digital Hierarchy (SDH) recommendations of the International Telecommunications Union (ITU).
• SDH is mostly used outside North America and principally in Europe
• Synchronous systems (e. g. SONET) :
• — Average frequency of all clocks in the system are same or nearly—Clocking provided by a highly stable reference supply

  —Allows many STS- 1s to be stacked together without of bit- stuffing

  —STS- 1s as well as VTs easily accessed from higher rates signals

  —Pointers accommodate differences in reference source frequencies, and phase wander

  • STS-1: Synchronous Transport Signal – level 1
  • STM-1: Synchronous Transport Module – level 1
• The telecommunications industry adopted the Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) standard for optical transport of TDM data. SONET, used in North America, and SDH, used elsewhere, are two closely related standards that specify interface parameters, rates, framing formats, multiplexing methods and management for synchronous TDM  over fiber.
• SONET/SDH takes “n” bit streams, multiplexes them and optically modulates the signal, sending it out using a light emitting device over fiber with a bit rate equal to (incoming bit rate) multiplied by “n.” Traffic arriving at the SONET/SDH multiplexer from four places at 2.5 Gigabits per second will go out as a single stream at 4 times 2.5 Gigabits per second, or 10 Gigabits per second.  

 SONET/SDH Digital Hierarchy

 SONET/SDH Tributaries