Alcatel-Lucent 7330 - CES Clocking and Synchronization

3 — ONT and MDU general and interface technical specifications
Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX ONT R04.06.02 November 2013 3-13
3FE 55873 AAAA TCZZA Edition 01
ONT Product Information Guide
The business ONT supports DS1 and E1 service connections at the subscriber
premises. The following TDM link types are supported:
• structured (fractional) DS1 or E1
• unstructured DS1 or E1
At the subscriber premises, the business ONT terminates DS1 or E1 links from the
subscriber. The TDM traffic is adapted and packetized using MEF-8 pseudo-wire
technology before being transported across the GPON. MEF-8 is the payload option
that is used. The MEF-8 packets are multiplexed with the Ethernet layer 2 data traffic
at the business ONT GPON port.
When the MEF-8 packets are received at the OLT, the packets are forwarded to the
destination PSTN, typically via a voice gateway that is connected to the IP network.
Figure 3-2 shows the traffic flow.
Figure 3-2 CES DS1 or E1 traffic between the ONT and PSTN over the GPON via the OLT
CES clocking and synchronization
The same clocking reference at both ends of the DS1 or E1 link is required to meet
the wander requirements of TDM traffic.
The business ONT can use one of two clocking sources for CES:
• a derived GPON clock at 16.384 MHz
• a 6.384 MHz local oscillator.
When the system clock for CES is derived from the GPON, the upstream P-OLT
locks to the BIT clock and supplies the ONT with an Ethernet clock that is traceable
to a network timing reference. The supplied Ethernet clock is used for differential
clock recovery and for timing the upstream pseudo-wire MEF-8 packet streams in
the absence of a valid TDM recovery clock. The local oscillator is only used if
adaptive mode is selected.
The downstream TDM streams may be timed from one of two clocking sources:
• a 16.384 MHz adaptive clock received from the MEF-8 packet stream.
• a differential clock recovered from the MEF-8 packet stream via the GPON.
L2
Ethernet
cloud
OLT
DS1 or E1
DS1 or E1 GE GE GPON
Class 5 PSTN
switch
Voice gateway
Business
ONT
EMS
DHCP server