What is the OTN (Optical Transport Network)?
ITU-T (Telecommunication
Standardization Sector) defines an Optical Transport Network (OTN) as a set
of Optical Network Elements (ONE) connected by optical fiber links, able to
provide functionality of transport, multiplexing, switching, management,
supervision and survivability of optical channels carrying client signals.
ITU-T Recommendation G.709 is
commonly called Optical Transport Network (OTN). As of December 2009 OTN has standardized the
following line rates.
Signal
|
Approximate
data rate (Gbit/s)
|
Applications
|
OTU1
|
2.66
|
|
OTU2
|
10.70
|
Transports an OC-192, STM-64 or wide area network (WAN) physical layer (PHY) for 10 Gigabit Ethernet (10GBASE-W)
|
OTU2e
|
11.09
|
Transports a 10 Gigabit Ethernet local area network (LAN) PHY coming from IP/Ethernet
switches and routers at full line rate (10.3 Gbit/s). This is specified in
G.Sup43.
|
OTU3
|
43.01
|
|
OTU3e2
|
44.58
|
Transports up to four OTU2e signals
|
OTU4
|
112
|
Why use OTN?
OTN offers the following advantages relative
to SONET/SDH:
·
Stronger Forward Error
Correction
·
More Levels of Tandem Connection
Monitoring (TCM)
·
Transparent Transport of
Client Signals
·
Switching Scalability
OTN Equipment Type
At a very high level
the typical signals that OTN equipment at the Optical Channel layer processes
are:
·
OTN
·
SONET/SDH
·
Ethernet/Fiber Channel
·
Packets
A few of the key
functions performed on these signals are:
·
Protocol processing of all
the signals. Some of the more complex processes are:
§ Forward
error correction (FEC) on OTN signals
§ Multiplexing
and de-multiplexing of OTN signals
§ Mapping
and de-mapping of non-OTN signals into and out of OTN signals
·
Packet processing in
conjunction with mapping/de-mapping of packet into and out of OTN signals
The basic OTN Layer
is consisting of the following information.
·
OCh:
Optical Channel
OCh
is consist of the end-to-end transparent transmission functions, including
re-arranging OCh connection to implement flexible network routing, processing
OCh overheads to achieve the completeness of OCh adaption information, and
monitoring OCh to implement the running and management of the network section.
·
OMS:
Optical Multiplex Section
It
provides multi-wavelength signals with network functions, including
re-arranging OMS connection to implement flexible multi-wavelength network
routing, processing OMS overheads to achieve the completeness of
multi-wavelength OMS adaption information, and monitoring OMS to implement the
running and management of the section.
·
OTS:
Optical Transmission Section
It transmits optical signals over various fibers as well as detects and controls the optical amplifiers.
It transmits optical signals over various fibers as well as detects and controls the optical amplifiers.
