Optical Transport Network - AbsoluteAstronomy.com

ITU-T defines an Optical Transport Network (OTN) as a set of Optical Network Elements (ONE) connected by optical fibre links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals. An ONE may Re-time, Re-transmit, Re-shape (3R) but it does not have to be 3R— it can be purely photonic.

Standards

OTN was designed to provide support for optical networking using wavelength-division multiplexing

Wavelength-division multiplexing

In fiber-optic communications, wavelength-division multiplexing is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light...

(WDM) unlike its predecessor SONET

Sonet

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

/SDH.

ITU-T Recommendation G.709

G.709

ITU-T Recommendation G.709 "Interfaces for the Optical Transport Network " describes a means of communicating data over an optical network...

is commonly called Optical Transport Network (OTN) (also called digital wrapper technology or optical channel wrapper). As of December 2009 OTN has standardized the following line rates.

OTU1 has a line rate of approximately 2.66 Gbit/s and was designed to transport a SONET
Sonet
Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...

OC-48 or synchronous digital hierarchy (SDH) STM-16 signal.
OTU2 has a line rate of approximately 10.70 Gbit/s and was designed to transport an OC-192, STM-64 or wide area network
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...

(WAN) physical layer (PHY) for 10 Gigabit Ethernet
10 Gigabit Ethernet
The 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...

(10GBASE-W).
OTU2e has a line rate of approximately 11.09 Gbit/s and was designed to transport a 10 Gigabit Ethernet local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

(LAN) PHY coming from IP/Ethernet switches and routers at full line rate (10.3 Gbit/s). This is specified in G.Sup43.
OTU3 has a line rate of approximately 43.01 Gbit/s and was designed to transport an OC-768 or STM-256 signal or a 40 Gigabit Ethernet signal.
OTU3e2 has a line rate of approximately 44.58 Gbit/s and was designed to transport up to four OTU2e signals.
OTU4 has a line rate of approximately 112 Gbit/s and was designed to transport a 100 Gigabit Ethernet
100 Gigabit Ethernet
40 Gigabit Ethernet, or 40GbE, and 100 Gigabit Ethernet, or 100GbE, are high-speed computer network standards developed by the Institute of Electrical and Electronics Engineers . They support sending Ethernet frames at 40 and 100 gigabits per second over multiple 10 Gbit/s or 25 Gbit/s lanes...

signal.

The OTUk (k=1/2/2e/3/3e2/4) is an information structure into which another information structure called ODUk (k=1/2/2e/3/3e2/4) is mapped. The ODUk signal is the server layer signal for client signals. The following ODUk information structures are defined in ITU-T Recommendation G.709

G.709

ITU-T Recommendation G.709 "Interfaces for the Optical Transport Network " describes a means of communicating data over an optical network...

Signal	\|Typical Applications
ODU0	1.24416	Transport of a timing transparent transcoded (compressed) 1000BASE-X signal or a stream of packets (such as Ethernet, MPLS or IP) using Generic Framing Procedure Generic Framing Procedure Generic Framing Procedure is a multiplexing technique defined by ITU-T G.7041. This allows mapping of variable length, higher-layer client signals over a circuit switched transport network like OTN, SDH/SONET or PDH...
ODU1	2.49877512605042	Transport of two ODU0 signals or a STS-48/STM-16 signal or a stream of packets (such as Ethernet, MPLS or IP) using Generic Framing Procedure Generic Framing Procedure Generic Framing Procedure is a multiplexing technique defined by ITU-T G.7041. This allows mapping of variable length, higher-layer client signals over a circuit switched transport network like OTN, SDH/SONET or PDH... .
ODU2	10.0372739240506	Transport of up to eight ODU0 signals or up to four ODU1 signals or a STS-192/STM-64 signal or a WAN PHY (10GBASE-W) or a stream of packets (such as Ethernet, MPLS or IP) using Generic Framing Procedure Generic Framing Procedure Generic Framing Procedure is a multiplexing technique defined by ITU-T G.7041. This allows mapping of variable length, higher-layer client signals over a circuit switched transport network like OTN, SDH/SONET or PDH...
ODU2e	10.3995253164557	Transport of a 10 Gigabit Ethernet 10 Gigabit Ethernet The 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by... signal or a timing transparent transcoded (compressed) Fibre Channel 10GFC signal
ODU3	40.3192189830509	Transport of up to 32 ODU0 signals or up to 16 ODU1 signals or up to four ODU2 signals or a STS-768/STM-256 signal or a timing transparent transcoded 40 Gigabit Ethernet signal or a stream of packets (such as Ethernet, MPLS or IP) using Generic Framing Procedure Generic Framing Procedure Generic Framing Procedure is a multiplexing technique defined by ITU-T G.7041. This allows mapping of variable length, higher-layer client signals over a circuit switched transport network like OTN, SDH/SONET or PDH...
ODU3e2	41.7859685595012	Transport of up to four ODU2e signals
ODU4	104.794445814978	Transport of up to 80 ODU0 signals or up to 40 ODU1 signals or up to ten ODU2 signals or up to two ODU3 signals or a 100 Gigabit Ethernet 100 Gigabit Ethernet 40 Gigabit Ethernet, or 40GbE, and 100 Gigabit Ethernet, or 100GbE, are high-speed computer network standards developed by the Institute of Electrical and Electronics Engineers . They support sending Ethernet frames at 40 and 100 gigabits per second over multiple 10 Gbit/s or 25 Gbit/s lanes... signal
ODUflex(CBR)	²³⁹/₂₃₈ x client bit rate	Transport of a Constant bitrate Constant bitrate Constant bitrate is a term used in telecommunications, relating to the quality of service. Compare with variable bitrate.When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant... signal such as Fibre Channel 8GFC, InfiniBand InfiniBand InfiniBand is a switched fabric communications link used in high-performance computing and enterprise data centers. Its features include high throughput, low latency, quality of service and failover, and it is designed to be scalable... or Common Public Radio Interface Common Public Radio Interface The Common Public Radio Interface standard defines the interface of base stations between the Radio Equipment Controllers in the standard, to local or remote radio units, known as Radio Equipment ....
ODUflex(GFP)	any configured rate	Transport of a stream of packets (such as Ethernet, MPLS or IP) using Generic Framing Procedure Generic Framing Procedure Generic Framing Procedure is a multiplexing technique defined by ITU-T G.7041. This allows mapping of variable length, higher-layer client signals over a circuit switched transport network like OTN, SDH/SONET or PDH...

Equipment

At a very high level the typical signals that OTN equipment at the Optical Channel layer processes are:

OTN
SONET/SDH
Ethernet/FibreChannel
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
  Forward error correction
  In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
  
  (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

Switch fabric

The OTN signals at all data-rates have the same frame structure but the frame period reduces as the data-rate increases. As a result, the Time-Slot Interchange

Time-Slot Interchange

A Time Slot Interchange switch uses RAM, memory for mapping and a counter. Like any switch, it has input and output ports.The function of the RAM is to store the packets which are inputted to it via its input terminal. Memory for mapping stores the information.The counter here is like a normal...

(TSI) technique of implementing SONET/SDH switch fabrics is not directly applicable to OTN switch fabrics. OTN switch fabrics are typically implemented using Packet Switch Fabrics.

FEC Latency

On a point-to-point OTN link there is latency due to forward error correction

Forward error correction

In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....

(FEC) processing.

Standards

Equipment

Switch fabric

FEC Latency

See also