Standard

ITU-T 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. OTN was designed to provide support for optical networking using wavelength-division multiplexing (WDM) unlike its predecessor SONET/SDH.

 

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Summary

At a very high level the typical client signals that OTN equipment processes and transports are:

•SONET/SDH

•Ethernet

•Special Packet and CBR Signals (GFP, ATM, ESCON, FICON, Fiber Channel, Infiniband, Video)

•ODU signals (from same or other OTNs)

 

OTN is standardized by ITU-T since 2009 (see Appendix for complex hierarchical structure).

 

Multiplexers

Typical OTN equipment combine an ‘electrical’ multiplexing section and a ‘photonic’ WDM mapping section into one multiplexer:

 

 

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Rates

OTN Rates are made up of nxODU0 base units. For simplicity OTU and ODU rates are mapped together in ConnectMaster.

 

 

ODU Rate Name

Rate (Mbps)

No of base units: ODU0

Standard

ODU0

1244.16

1

OTH

OTU1/ODU1

2498.78

2

OTH

OTU2/ODU2

10037.27

8

OTH

OTU3/ODU3

40319.22

32

OTH

OTU4/ODU4

104794.5

80

OTH

OTU2e/ODU2e

10399.52

8

OTH

OTU3e/ODU3e

41785.97

32

OTH

ODU-Flex

 

Flexible 1 to 80

OTH

 

OTN Mapping

 

Child OTN TC can be mapped into Parent OTN TC based on the following structure rules.

 

 

Parent TC

 

ODU0

ODU1

ODU2

ODU3

ODU4

ODU2e

ODU3e

Child TC

# children

#ODU0 Occup

# children

#ODU0 Occup

# children

#ODU0 Occup

# children

#ODU0 Occup

# children

#ODU0 Occup

# children

#ODU0 Occup

# children

#ODU0 Occup

ODU0

x1

1

x2

1

x8

1

x32

1

x80

1

x8

1

x32

1

ODU1

-

-

x1

2

x4

2

x16

2

x40

2

x4

2

x16

2

ODU2

-

-

-

-

x1

8

x4

8

x10

8

x1

8

x4

8

ODU3

-

-

-

-

-

-

x1

32

x2

32

-

-

x1

32

ODU4

-

-

-

-

-

-

-

-

 

 

-

-

-

-

ODU2e

-

-

-

-

-

-

*x3

*9

x10

8

x1

8

x4

8

ODU3e

-

-

-

-

-

-

-

-

x2

32

-

-

x1

32

 

Note

*Please note the special case of the ODU2e utilization in the ODU3 capacity is 9 ODU0 blocks, maximum of 3 ODU2e can go into an ODU3 (with 5xODU0 blocks free for use by smaller capacities). However, in other “normalized” parents (ODU3e and ODU4), the ODU2e only occupies 8 ODU-0 blocks.

 

Client Mapping

Child SDH/SONET and Ethernet TC can be mapped into Parent OTN TC based on the following structure rules.

 

Parent TC

Child TC

Capacities

ODU0

Ethernet TC

<= ODU0 payload size
1,244,160 bps (carries 1 GbE)

 

SDH TC

<= STM-4

 

SONET TC

<=STS-12

OTU1/ODU1

Ethernet TC

<= 2,488,320 bps

 

SDH TC

<= STM-16

 

SONET

<= STS-48

OTU2/ODU2

Ethernet TC

<= 9,995,277 bps (10Gb WAN-PHY)

 

SDH TC

<= STM-64

 

SONET

<=STS-192

OTU2e/ODU2e

Ethernet TC

<= 10.3G  (full rate 10GbE)

OTU3/ODU3

Ethernet TC

<= 40,150,519 (40GbE)

 

SDH TC

<=STM-256

 

SONET

<=STS-768

OTU3e/ODU3e

Ethernet TC

<=40,150,519 (40GbE)

OTU4/ODU4

Ethernet TC

<= 100GbE