Optical transport network

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The optical transport network ( OTN , English optical transport network ) is a technology standardized by the ITU in the G.709 standard for a telecommunications network with which network operators use a transport service to transmit useful data.

architecture

The architecture of the optical transport network consists of three layers:

  • The lowest layer, the Optical Transmission Section (OTS), describes the optical fiber route between two optical system components. These can be optical amplifiers (OA), optical add-drop multiplexers (OADM) or optical cross-distributors (OXC).
  • The layer above, the Optical Multiplex Section (OMS), comprises the multiplex functions of a D WDM connection between two network nodes .
  • The top layer, the Optical Channel Layer (OCh), describes the optical channel between two participants. Any user data can be transmitted in such a channel. Standardized adaptation functions allow Ethernet and IP frames to be transmitted without prior PDH or SDH framing.

Analogous to the terms PDH and SDH, the abbreviation OTH ( optical transport hierarchy ) was chosen for the optical transport hierarchy . The bit rates that are transmitted by the optical transport network begin where those of SDH technology end. Standardized bit rates of the optical transport hierarchy are:

  • OTM-1: 2.67 Gbit / s
  • OTM-2: 10.7 Gbit / s
  • OTM-3: 43.0 Gbit / s
  • OTM-4: 111.8 Gbit / s

In addition, OTU-2, as described in ITU document G.Sup43, can be overclocked (OTU-2e) to enable 10 Gigabit Ethernet LAN PHY.

Devices that correspond to the standardized architecture of the OTN have now been introduced by all major manufacturers of telecommunication devices and are now also used in the technical infrastructure of the Internet. Interconnecting devices from different manufacturers has so far only been possible to a limited extent, since the standardization so far only describes optical multiplex principles without specifying the physical implementation down to the last detail.

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