Nortel Networks OPTera Metro 3500 - Manual (Page 290)

3-62 Hardware feature descriptions
OPTera Metro 3500 Multiservice Platform NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
Equipping rules
The OC-192 optical interface circuit pack can be installed in slots 11 and 12.
See
Table 3-3 on page 3-6 for operational temperature ranges.
An OPTera Metro 3500 network element with a protected OC-192 line rate
requires two OC-192 circuit packs in slots 11 and 12 of each shelf.
Note 1: Requires the shelf to be equipped with STX-192 circuit packs in
slots 13 and 14.
Note 2: Supports STS managed connections only.
Note 3: Interoperability with the OPTera Metro 3500 OC-192 Long reach
(LR) G.709 FEC and OC-192 DWDM G.709 FEC optical interfaces
requires G.709 compatible optics. You can equip the OPTera Metro 3500
shelf with a mix OC-192 IR and OC-192 G.709 circuits, however they
must connect to the same type of card on the other end of the fiber span.
OC-192 protection switching
OC-192 traffic can be protected by 1+1 linear, UPSR, or BLSR protection.
1+1 linear protection
OC-192 linear protection switching is 1+1 non-revertive, unidirectional or
bidirectional. If a fiber cut occurs in either the receive or transmit fibers of the
active fiber path, or the transmitter or receiver of an OC-192 optical interface
circuit pack fails at either end of the active fiber span, traffic is switched from
the active OC-192 transmitter or receiver to the standby OC-192 transmitter or
receiver. Switching can also take place under user control.
In bidirectional protection switching, if traffic in one of the two directions is
interrupted, traffic in both directions is switched to the protection line. In
unidirectional protection switching, if traffic in one of the two directions is
interrupted, only the interrupted traffic switches to the protection line; traffic
in the uninterrupted direction remains on the working fiber. Both OC-192
interface circuit packs are active if unidirectional switching occurs and one
fiber fails.
The signal degrade threshold is user-provisionable for the working OC-192
facility of a 1+1 linear protected OC-192 pair. The default value is 10
-6
. The
threshold is provisionable within the range 10
-5
to 10
-9
. If the bit error rate
(BER) drops below the threshold, an autonomous protection switch occurs.
UPSR path protection
OC-192 path switching uses nonrevertive protection. There are no permanent,
STS-1/, STS-3c, STS-12, STS-12c, STS-24c, STS-48c protection or working
paths. The network element receives two incoming STS-1/, STS-12, STS-3c,
STS-12c, STS-24c or STS-48c signals: one from the provisioned working
optical interface circuit pack and one from the switchmate optical interface
circuit pack. The network element selects the better of the two signals.