Alcatel-Lucent 7330 - Figure 3-2 CES DS1 or E1 Traffic between the ONT and PSTN over the GPON Via

3 — ONT and MDU general and interface technical specifications
3-12 March 2011 Alcatel-Lucent 7330/7302 ISAM FTTN R04.02.42a
ONT Product Information Guide Edition 01 3FE 54199 AAAA TCZZA
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.
When the clock is received from the GPON, the GPON must be configured to send
RTP packets.
In adaptive timing, a local, free-running 25 MHz clock is used. The generated bit rate
is determined by the long-term average data rate. The attached DS1/E1 equipment
must be loop timed. In differential timing, a 16.384 MHz reference clock is
synchronized to the PON. Both ends of the DS1/E1 CES PW must use the same
reference clock frequency and be synchronized to a common source. RTP is used to
transport the transmit bit rate information. The DS1 or E1 equipment that is attached
to the terminating CES PW devices must be loop timed. In loop timing, the receive
clock rate is used for the transmit clock rate. The DS1/E1 equipment that is attached
must be source timed, not loop timed.
L2
Ethernet
cloud
OLT
DS1 or E1
DS1 or E1 GE GE GPON
Class 5 PSTN
switch
Voice gateway
Business
ONT
EMS
DHCP server