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Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 10 Network Reference
10.10 Even Band Management
2. 10,709,225.316 kbps—Optical Transport Unit 2 (OTU2)
3. 43,018,413.559 kbps—Optical Transport Unit 3 (OTU3)
The OTU2 rate is higher than OC-192 because the OTU2 has to carry overhead and FEC bytes in its
frame; the bits must be sent faster to carry the payload information at the OC-192 rate.
The ITU-T G.709 frame has two parts. Two are similar to a SDH/SONET frame:
1. Overhead area for operation, administration, and maintenance functions
2. Payload area for customer data
In addition, the ITU-T G.709 frame also includes FEC bytes.
10.9.4.1 OC-192 Packaged Into OTU2 G.709 Frame Data Rate (10.70923 Gbps)
In this case, an OC-192 frame is being transported over a OTU2 G.709 frame, which adds the benefit of
FEC. The OC-192 data rate (9.95328 Gbps) must increase in order to transport more bytes (OC-192 plus
ITU-T G.709 overhead plus ITU-T G.709 FEC bytes) in the same amount of time. In an OTU2
transmission, 237 of the 255 bytes are OC-192 payload. This means the resultant data rate is:
9.95328 x 255/237 = 10.70923 Gbps
10.9.4.2 10GE Packaged Into OTU2 G.709 Frame Data Rate (Nonstandard 11.0957 Gbps)
Encapsulating Ethernet data into an OTU2 G.709 frame is considered nonstandard. The goal is to add
the benefit of ITU-T G.709 encapsulation to achieve better burst error performance. However, this means
adding overhead and FEC bytes, so more bytes must be transmitted in the same amount of time, so the
data rate must increase. The new date rate is:
10.3215 x 255/237 = 11.0957 Gbps
10.9.4.3 10G FC Packaged Into OTU2 G.709 Frame Data Rate (Nonstandard 11.31764 Gbps)
Encapsulating Fibre Channel in an OTU2 frame is considered nonstandard. The rate is higher than the
10.51875 rate because OTU2 includes FEC bytes. The bits must run at a faster rate so that the payload
is provided at the standard Fibre Channel rate. The rate is:
10.51875 x 255/237 = 11.31764 Gbps
10.10 Even Band Management
With the introduction of the following cards, it is now possible to transport 72, 80, 104, or 112
wavelength channels in the same network:
• 40-WSS-CE (40-channel Wavelength Selective Switch, C-band, even channels)
• 40-DMX-CE (40-channel Demultiplexer, C-band, even channels)
By using these new cards along with the 40-WSS-C and 40-DMX-C cards (which handle 40 C-band odd
channels), the 32WSS and 32DMX cards (which handle 32 C-band odd channels), and the 32WSS-L and
32DMX-L (which handle 32 L-band odd channels), it is possible to cover 80 C-band channels (40 even
and 40 odd channels) and 32 L-band odd channels, for a maximum of 112 channels. The following
channel coverage combinations are possible:
• 72 C-band channels, using the 32WSS, 32DMX, 40-WSS-CE, and 40-DMX-CE cards
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