Timing Synchronization; Y-Cable Protection; Enhanced Fec (E-Fec) Capability; Fec And E-Fec Modes - Cisco ONS 15454 DWDM Installation And Operation Manual

Chapter 14 Card Reference

14.8.5.6 Timing Synchronization

The MXP_2.5G_10E card is synchronized to the TCC2 clock during normal conditions and transmits
the ITU-T G.709 frame using this clock. No holdover function is implemented. If clocks from both TCC2
cards are not available, the MXP_2.5G_10E 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 MXP_2.5G_10E
continues to monitor the TCC2. If a TCC2 is restored to working order, the MXP_2.5G_10E reverts to
the normal working mode of running from the TCC2 clock. If there is no valid TCC2 clock and all of
the client channels become invalid, the card waits (no valid frames processed) until one of the TCC2
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.

14.8.5.7 Y-Cable Protection

The MXP_2.5G_10E card supports Y-cable protection. Two MXP_2.5G_10E cards can be joined in a
Y-cable protection group with one card assigned as the working card and the other defined as the
protection card. This protection mechanism provides redundant bidirectional paths. See the
"14.9.1 Y-Cable Protection" section on page 14-119
The Y-protection mechanism is provisionable and can be set ON or OFF (OFF is the default mode).
When a signal fault is detected (LOS, LOF, signal degrade [SD], or SF on the DWDM receiver port in
the case of ITU-T G.709 mode) the protection mechanism software automatically switches between
paths.
If you create a GCC on either card of the protect group, the trunk port stays permanently active,
Note
regardless of the switch state. When you provision a GCC, you are provisioning unprotected overhead
bytes. The GCC is not protected by the protect group.

14.8.5.8 Enhanced FEC (E-FEC) Capability

A key feature of the MXP_2.5G_10E is the availability to configure the Forward Error correction in
three modes: NO FEC, FEC, and E-FEC. The output bit rate are always 10.7092 Gbps as defined in
G.709, but the error coding performance can be provisioned as follows:
•
•
•

14.8.5.9 FEC and E-FEC Modes

As client side traffic passes through the MXP_2.5G_10E card, it can be digitally wrapped using FEC
mode error correction or E-FEC mode error correction (or no error correction at all). The FEC mode
setting provides a lower level of error detection and correction than the E-FEC mode setting of the card.
As a result, using E-FEC mode allows higher sensitivity (lower OSNR) with a lower bit error rate than
FEC mode. E-FEC enables longer distance trunk-side transmission than with FEC.
The E-FEC feature is one of three basic modes of FEC operation. FEC can be turned off, FEC can be
turned on, or E-FEC can be turned on to provide greater range and lower BER. The default mode is FEC
on and E-FEC off. E-FEC is provisioned using CTC.
December 2004
NO FEC: no forward error correction
FEC: standard G.975 Reed-Solomon algorithm
E-FEC: standard G.975.1 two orthogonally concatenated BCH super FEC code. This FEC scheme
contains three parameterizations of the same scheme of two orthogonally interleaved block codes
(BCH). The constructed code is decoded iteratively to achieve the expected performance.
for more detailed information.
Cisco ONS 15454 DWDM Installation and Operations Guide, R4.7
14.8.5 MXP_2.5G_10E Card
14-109