Tektronix ST2400A Datasheet

The ST2400A is the first
STM-16/OC-48 test product
optimized for testing

2.488 Gbit/s Dense Wave­length Division Multiplexed
(DWDM) client systems. Its
compact size, flexibility of
configuration, choice of oper­ating modes, unique I/O fea­tures, extensive software
driver support, and range of
error and defect inject capa­bilities make it particularly
effective for DWDM system
test during production and
installation. It can also be
used in non-DWDM SDH and
SONET test applications.

The ST2400A is payload­independent; external
SDH/SONET 155 Mbit/s
optical and electrical and
622 Mbit/s optical signals are
supported in add/drop mode.
The ST2400A can be ordered
as an ST2400A Transceiver,
as an ST2400R Receiver, or
as an ST2400T Transmitter to
meet a wide range of applica­tion needs economically.

The ST2400A Transceiver
version can transmit and
receive STM-16/OC-48 sig­nals. The ST2400A has the
ability to receive, generate
and modify an STM-16c/
OC-48c signal. The transmit­ter section can internally gen­erate a 2.4 Gb/s signal or
multiplex the higher-rate sig­nal from STM-1 or STM-4
(OC-3 or OC-12) signal
inputs. The ST2400A can
also accept a STM-16/OC-48
signal in through mode and
regenerate it. The receiver
section receives an STM­16/OC-48 signal, demulti­plexes it, and can drop out
either the STM-1 or STM-4
(OC-3 or OC-12) signal as
required.

The Transmitter version can
generate and transmit the
STM-16/OC-48 signal from
an internal source, or multi­plex the higher-rate signal
from either STM-1 or STM-4
(OC-3 or OC-12) signal
inputs. In the case of STM-4c
and STM-16c (OC-12c or

Copyright © 1999 Tektronix, Inc. All rights reserved.

ST2400A
STM-16/OC-48 2.4 Gbit/s Test
Set for DWDM Applications

Optimized for Dense Wavelength
Division Multiplexing (DWDM)
Transmission Quality Testing

Available in Transceiver, Receiver
and Transmitter Only Versions

Tributary Testing of STM-64/OC-192
Systems

Easily Switchable to/from
SDH/SONET

Optical Tributary Payload Add/Drop
with Payload Independence

External Sync Reference for Timing
Coordination

Active Through Mode to Simulate
Fault Conditions on Installed
Networks

Compact and Light Weight for
Production and Installation Test

A Variety of Optics Options,
Including No Optics

Emulates Network Elements
Transmitting Live Traffic

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 con­tain 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) sig­nal 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 elec­trical 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 out­puts. 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 broad­band optical detector which
is not wavelength-selective).

Three Operating Modes

The ST2400A Transceiver
features three operating
modes to provide the flexibil­ity 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), Multi­plexer 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 inde­pendently. An internally-gen­erated 2.488 Gbit/s test signal
provides full error perfor­mance 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 over­head 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 synchro­nization and protection
switching, and for diagnosing
system interoperability prob­lems. 155 or 622 Mbit/s sig­nals can be dropped from the
receiver for path level analy­sis on another tester.

Add/Drop (External) Mode

In this mode, the ST2400A
transmitter creates the 2.488
Gbit/s signal from an exter­nally added 155 or 622
Mbit/s SDH or SONET signal.
The external signal can be

copied into one or all avail­able 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 equip­ment is preserved.

Emulation of Real SDH/SONET
Systems

The ST2400A provides two
features that let the tester
emulate real network condi­tions. First, a 2

23

-1 PRBS pat­tern can be generated to pro­duce a synchronous signal
that behaves like live traffic.
Second, the optical receiver’s
decision threshold can be off­set to emulate older
SDH/SONET network ele­ments that are deployed in
the field and which can cre­ate interoperability issues
when connected to optically
amplified systems such as
DWDM. By controlling what
the ST2400A considers a
“one” or a “zero,” true sys­tem transmission quality can
be determined; installed
behavior predicted; and, opti­mized in the factory.

DWDM Parallel Channel Test

Because DWDM systems car­rying SDH/SONET clients are
expected to operate at a trans­mission quality level of
10

–12

BER or better per ITU-T
G.692 and Bellcore GR­2918,per channel transmis­sion quality test cycles can
easily exceed twelve hours.
By testing all channels in par­allel, 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 mea­sure the transmission perfor­mance of each channel of the
multi-wavelength system,
while a ST2400T Transmitter

page 3

is used to generate the

2.488 Gbit/s signal, which
can be split to multiple
inputs of the DWDM system.
The Parallel Channel Test is
illustrated in the figure
below.

Help in Lowering per Channel
Test Time

In addition to using the
ST2400A for effective paral­lel channel test, the product
can also help lower per-chan­nel test time.

Accelerating Low BER Measurement
through Extrapolation

Measuring the low error rates
that DWDM systems promise
can take a minimum of 11
hours at 2.488 Gbit/s. The
ST2400A provides a way in
some applications to save test
time by extrapolating to low
BERs through offset of the
optical receiver’s decision
threshold.

Improved Test Convenience

If the system has been charac­terized in design, then many
of these tests need not be
repeated further down the
value chain. The power of the
ST2400A is focused on sys­tem transmission quality ver­ification during production
and installation. For produc­tion test, a full remote com­mand set plus LabView™and
LabWindows™CVI, HP-VEE

™

drivers help manufacturing
engineers create automated
test suites quickly and effi­ciently. A "pause" feature
enables tests to be suspended
while rearrangements are
made, which allow long-term
testing to proceed. Tests can
also be automatically
resumed after lost power is
restored, again saving retest
time. Finally, by using the
ST2400A in constant wave­length (unmodulated) mode,
optical tests such as OSNR
and spectral width can be

done without the need for an
additional laser source.

2.488 Gbit/s Interface Choices

For manufacturers and
installers of DWDM equip­ment, the ST2400A offers a
low-dispersion, long reach
1550 nm laser option that
provides enhanced perfor­mance. In addition, the low­dispersion optics can be
ordered at specific ITU-T
G.692 grid frequencies to
meet precise requirements. If
low-dispersion optics are not
required, the ST2400A long­reach 1310 nm optics can be
ordered. A dual
1310/1550 nm wavelength
option is provided for cus­tomers who need flexibility.
Finally, a customer can
choose to configure units
with only 2.488 Gbit/s elec­trical I/O. This feature is pro­vided for applications such
as laser-driver module tests
where optics are not
required.

± 1 nm Wavelength Tuning

The ST2400A provides the
capability to “tune” the
wavelength of its 1550 nm
laser from its nominal value
up or down by one nanome­ter. This feature allows the
user to check adjacent chan­nels on the G.692 frequency
grid without purchasing
additional specific wave­length lasers. This feature
would typically be useful in
testing DWDM systems with­out transponders or in testing
transponder-based systems
when the transponder is not
part of the test set up.

STM-64/OC-192 Tributary Testing

Testing 10 Gbit/s systems at
the line rate requires very
expensive test equipment.
These systems can be tested
more economically at the

2.488 Gbit/s tributary rate
using the ST2400A.

Adheres To The Latest Standards

The ST2400A complies with
the latest ITU-T, ANSI, ETSI,
and Bellcore recommenda­tions and standards.

Capabilities

• STM-16 SDH RS and MS

Testing/OC-48 SONET Sec­tion and Line Testing

– B1, B2, B3 Error

Generation

– B1, B2, B3 Error

Measurement

– Path REI, Path Alarms,

Pattern Bit Error
– J0, J1 Capture and J0 Edit
– RS and MS Alarm

Generation
– RS and MS Alarm

Detection
– RS and MS Layer Alarm

and Error Generation

• VC4 PRBS Mappings/STS1,
STS3c PRBS Mappings

• Ability to receive, generate
and modify an STM­4c/STM-16c (OC-12c/
OC-48c) Payload (Opt. 41)

• External Clock Input
(2 Mbps/2 MHz) or

1.5 Mbps

• User-selectable power fail­ure recovery mode

• Electrical Offset of Receiver
Decision Threshold

• ±1 nm wavelength tuning
(applies only to 1550 nm
lasers)

• CW laser source mode

• 2.488 Gb/s electrical I/O

• 3-year warranty

• Automatic Optical Receiver
shut-off if power exceeds
maximum rating

• Specific wavelength G.692
lasers in 1550 nm region

• Portable – 11.4 kilograms
(25 pounds) maximum
weight

• A simple menu system

• Tributary Access at
155 Mb/s or 622 Mb/s

• Easily software switched
between SDH and SONET

• Integrates with the CTS 750
or CTS 850 or ST112 for
complete “all-rate” SDH or
SONET analysis

• Wide optical range:
– 3 dBm to –2 dBm Typical

Output Power

– -29 dBm to –10 dBm

Receiver Sensitivity