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Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 8 Transponder and Muxponder Cards
8.8.5 Multiplexing Function
Caution You must use a 20-dB fiber attenuator (15 to 25 dB) when working with the cards in a loopback on the
trunk port. Do not use direct fiber loopbacks with the cards. Using direct fiber loopbacks causes
irreparable damage to the MXP_2.5G_10E_C and MXP_2.5G_10E_L cards.
8.8.5 Multiplexing Function
The muxponder is an integral part of the ROADM network. The key function of the MXP_2.5G_10E_C
and MXP_2.5G_10E_L cards is to multiplex four OC-48/STM16 signals onto one ITU-T G.709 OTU2
optical signal (DWDM transmission). The multiplexing mechanism allows the signal to be terminated at
a far-end node by another similar card.
Transparent termination on the muxponder is configured using OTUx and ODUx OH bytes. The
ITU-T G.709 specification defines OH byte formats that are used to configure, set, and monitor frame
alignment, FEC mode, section monitoring, tandem connection monitoring, and transparent termination
mode.
The MXP_2.5G_10E and MXP_2.5G_10E_L cards perform ODU to OTU multiplexing as defined in
ITU-T G.709. The ODU is the framing structure and byte definition (ITU-T G.709 digital wrapper) used
to define the data payload coming into one of the SONET/SDH client interfaces on the cards. The term
ODU1 refers to an ODU that operates at 2.5-Gbps line rate. On the cards, there are four client interfaces
that can be defined using ODU1 framing structure and format by asserting a ITU-T G.709 digital
wrapper.
The output of the muxponder is a single 10-Gbps DWDM trunk interface defined using OTU2. It is
within the OTU2 framing structure that FEC or E-FEC information is appended to enable error checking
and correction.
8.8.6 Timing Synchronization
The MXP_2.5G_10E_C and MXP_2.5G_10E_L cards are synchronized to the TCC2/TCC2P clock
during normal conditions and transmit the ITU-T G.709 frame using this clock. No holdover function is
implemented. If neither TCC2/TCC2P clock is available, the card switches automatically (hitless) to the
first of the four valid client clocks with no time restriction as to how long it can run on this clock. The
card continues to monitor the TCC2/TCC2P card. If a TCC2/TCC2P card is restored to working order,
the card reverts to the normal working mode of running from the TCC2/TCC2P clock. If there is no valid
TCC2/TCC2P clock and all of the client channels become invalid, the card waits (no valid frames
processed) until one of the TCC2/TCC2P cards supplies a valid clock. In addition, the card is allowed
to select the recovered clock from one active and valid client channel and supply that clock to the
TCC2/TCC2P card.
8.8.7 Enhanced FEC (E-FEC) Capability
The MXP_2.5G_10E_C and MXP_2.5G_10E_L cards can configure the FEC in three modes: NO FEC,
FEC, and E-FEC. The output bit rate is always 10.7092 Gbps as defined in ITU-T G.709, but the error
coding performance can be provisioned as follows:
• NO FEC—No FEC
• FEC—Standard ITU-T G.975 Reed-Solomon algorithm
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