Atec Tektronix-ST2400A - Manual (Page 2)

page 2
OC-48c, the ST2400A can
either generate four STM-4c
(OC-12c) tributary signals
with PRBS payloads inside
an STM-16/OC-48 envelope,
or generate three tributary
payloads of PRBS STM-4c
(OC-12c) and insert a fourth
from outside the tributary
interface (which could con-
tain IP traffic). In the case of
STM-16c/OC-48c, the entire
(single) payload is PRBS. All
applicable SDH/SONET Path
Pointer Bytes (H1/H2/H3) are
set correctly to indicate the
type of payload being carried
(STM-4c/STM-16c,
OC-12c/OC-48c, etc.).
The Receiver version can
receive and demultiplex the
STM-16/OC-48 signal and
drop either the STM-1 or
STM-4 (OC-3 or OC-12) sig-
nal to an auxiliary test set,
as required.
ST2400A can accept zero,
one or two factory-installed
2.488 Gb/s laser transmitter
modules and/or zero or one
APD receiver module (also
referred to as I/O modules).
One type of laser transmitter
– direct modulated (DM) – is
available.
The ST2400A provides elec-
trical input and output clock
and data interfaces operating
at 2.488 Gb/s. Base
Transceiver configuration
provides 2.488 Gb/s electrical
interfaces and 155/622 Mb/s
optical and electrical
add/drop tributary interfaces.
Transmitter configurations do
not include 155/622 optical
and electrical drop interface.
Receiver configurations do
not include 155/622 optical
and electrical add interface.
The user can individually
enable/disable laser #1 (if
installed), laser #2 (if
installed), and electrical out-
puts. Multiple outputs can be
simultaneously active.
NOTE: RX will not measure
correctly if both TX lasers are
enabled and looped back to
RX (since RX contains broad-
band optical detector which
is not wavelength-selective). Three Operating Modes
The ST2400A Transceiver
features three operating
modes to provide the flexibil-
ity you need to test today’s
advanced STM-16, OC-48,
STM-64, OC-192, and DWDM
systems. Analysis is done at
the SDH/SONET Regenerator
Section (Section), Multi-
plexer Section (Line) and
Path levels independent of
the payload.
Standalone (Internal) Mode
Where payload testing is not
required, or an external
155 or 622 Mbit/s tributary
signal is not available, the
ST2400A can operate inde-
pendently. An internally-gen-
erated 2.488 Gbit/s test signal
provides full error perfor-
mance analysis and reporting
of the 2.488 Gbit/s signal.
1.5 Mbit/s, 2 Mbit/s, and
2 MHz external reference
clock signals or an internal
clock signal can be used to
time the transmitted signal in
internal mode. Internal mode
is ideal for DWDM
SDH/SONET client system
testing, where transmission
quality test time and cost can
be lowered through the use of
a high-speed signal.
Active Through Mode
Through Mode allows over-
head bytes to be passed or
edited while regenerating the
received 2.488 Gbit/s signal.
Alarms and errors can also be
added to the received signal
prior to retransmission. This
mode is especially valuable
for testing framing synchro-
nization and protection
switching, and for diagnosing
system interoperability prob-
lems. 155 or 622 Mbit/s sig-
nals can be dropped from the
receiver for path level analy-
sis on another tester.
Add/Drop (External) Mode
In this mode, the ST2400A
transmitter creates the 2.488
Gbit/s signal from an exter-
nally added 155 or 622
Mbit/s SDH or SONET signal.
The external signal can be
copied into one or all avail-
able payload envelopes in the
2.488 Gbit/s signal. The
ST2400A receiver performs
2.488 Gbit/s level testing and,
as required, drops a tributary
signal for path level analysis
by a Tektronix CTS 850, CTS
710, ST112, or any other 155
or 622 Mbit/s SDH or SONET
test set. Previous investment
in lower speed test equip-
ment is preserved.
Emulation of Real SDH/SONET
Systems
The ST2400A provides two
features that let the tester
emulate real network condi-
tions. First, a 2
23 -1 PRBS pat-
tern can be generated to pro-
duce a synchronous signal
that behaves like live traffic.
Second, the optical receiver’s
decision threshold can be off-
set to emulate older
SDH/SONET network ele-
ments that are deployed in
the field and which can cre-
ate interoperability issues
when connected to optically
amplified systems such as
DWDM. By controlling what
the ST2400A considers a
“one” or a “zero,” true sys-
tem transmission quality can
be determined; installed
behavior predicted; and, opti-
mized in the factory.
DWDM Parallel Channel Test
Because DWDM systems car-
rying SDH/SONET clients are
expected to operate at a trans-
mission quality level of
10
–12 BER or better per ITU-T
G.692 and Bellcore GR-
2918,per channel transmis-
sion quality test cycles can
easily exceed twelve hours.
By testing all channels in par-
allel, system test time can
remain constant as channel
counts increase from eight to
sixteen to thirty two and
beyond. The ST2400R
Receiver provides the means
for highly cost-effective
simultaneous multi-channel
analysis. A Receiver can mea-
sure the transmission perfor-
mance of each channel of the
multi-wavelength system,
while a ST2400T Transmitter