HP 37717C
Communications
Performance Analyzer
SDH / SONET
Operating Manual
Copyright HewlettPackard Ltd.1997
All rights reserved.
Reproduction, adaption,
or translation without prior
written permission is
prohibited, except as
allowed under the
copyright laws.
Information in this
document may apply to
modules which use the
VxWORKS TM software.
The VxWORKS TM
software was developed by
Wind River Systems, Inc.,
which has copyright to it.
HP Part No. 37717-90284
First edition, September 97
Printed in U.K.
Warranty
The information contained
in this document is subject
to change without notice.
Hewlett-Packard mak es no
warranty of any kind with
regard to this material,
including, but not limited
to, the implied warranties
or merchanability and
fitness for a particular
purpose.
Hewlett-Packard shall not
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incidental or
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or use of this material.
WARNING
Warning Symbols Used
on the Product
!
The product is marked
with this symbol when the
user should refer to the
instruction manual in order
to protect the apparatus
against damage.
The product is marked
with this symbol to
indicate that hazardous
voltages are present
The product is marked
with this symbol to
indicate that a laser is
fitted. The user should
refer to the laser safety
information in the
Calibration Manual.
Hewlett-Packard Limited
Communications Measurements Division
South Queensferry
West Lothian, Scotland EH30 9TG
SDH / SONET Operating Manual
HP 37717C Communications
Performance Analyzer
About This Book
“The HP 37717C SDH / SONET Operating Manual” explains the following:
• How to select and use the SDH / SONET features provided with the SDH /
SONET options
• How to make SDH / SONET measurements
For some operations and measurements, information from one of the following
associated books may be required:
“The HP 37717C Mainframe Operating Manual” explains how to obtain the
required display, how to use the front panel keys, how to interpret the status
indicators, how to connect to external equipment and how to perform instrument
tasks associated with the HP 37717C Communications Performance Analyzer
irrespective of the option configuration.
“The HP 37717C PDH /DSn Operating Manual” describes the selection of PDH /
DSn features and how to perform PDH / DSn tests with the HP 37717C
Communications Performance Analyzer.
“The HP 37717C Jitter Operating Manual” describes the selection of Jitter
features and how to perform Jitter tests with the HP 37717C Communications
Performance Analyzer.
“The HP 37717C ATM Operating Manual” describes the selection of ATM
features and how to perform ATM tests with the HP 37717C Communications
Performance Analyzer.
iv
Contents
1 SDH / SONET Modules
Introduction to SDH / SONET 2
SDH / SONET Options 3
SDH / SONET Features 5
2 SDH / SONET Application Measurements
Add/Drop Multiplexer Testing 24
Alarm Stimulus/Response 29
DCC Testing 33
Desynchroniser Stress 36
Frame Synchronization 39
SDH Jitter Transfer 44
MSP Stimulus/Response 47
Optical Clock Recovery Stress 51
Payload Mapping/Demapping 53
Performance Monitor Stimulus/ Response 59
Selective Jitter Transfer Measurement 62
3 ETSI / ANSI Terminology
ETSI / ANSI Equivalent Terms 68
v
Contents
vi
1
Introduction to SDH / SONET page 2
SDH / SONET Options page 3
SDH / SONET Features page 5
SDH Settings page 5
SONET With ATM Payload, Settings page 6
STM-1 THRU Mode (Option A1T (A1U) only) page 7
STM-4 THRU Mode (Option A1T (A1U) and UKT or USN only) page 8
Transmit Static Overhead (Option A1T (A1U) only) page 9
Transmit Overhead Sequence page 13
Receive Overhead Monitor page 14
Receive Overhead Capture page 15
Errors and Alarms page 16
Overhead Bit Error Rate (A1T (A1U) only) page 17
Add Pointer Adjustments (A1T (A1U) only) page 17
Pointer Graph (A1T (A1U) only) page 19
MSP (Multiplexer Section / Transport Protection) Messages page 20
SYNC Messages page 21
Optical Clock Recovery Stress (A1T (A1U) only) page 21
DCC Insert and Drop (A1T (A1U) only) page 21
Optical Power Measurement (Options USN and UKT Only) page 22
STM-1/STM-4 Binary Interface (Option OYH with USN or UKT) page 22
1 SDH / SONET Modules
Information on the optional modules including
selection of the features available.
SDH / SONET Modules
Introduction to SDH / SONET
Introduction to SDH / SONET
Synchronous Digital Hierarchy (SDH) is an international standard (ETSI)
for high speed synchronous optical telecommunications networks.
Synchronous Optical NETwork (SONET) is the U.S. (ANSI) equivalent of
SDH defined by Bellcore.
The concept of a synchronous transport system, based on SDH / SONET standards,
goes beyond the basic needs of a point to point transmission system. It includes the
requirements of telecommunications networking - switching, transmission and
network control. These capabilities, allow SDH / SONET to be used in all three
traditional network application areas - Local Network, Inter-exchange Network and
Long Haul Network - thus providing a unified telecommunication network structure.
The SDH / SONET standards are based on the principle of direct synchronous
multiplexing. This means that individual tributary signals (Payload) may be
multiplexed directly into a higher rate SDH / SONET signal without intermediate
stages of multiplexing. SDH / SONET network elements, even those supplied by
different manufacturers, can be interconnected directly giving cost and equipment
savings.
There are minor differences between SDH and SONET, mainly in nomenclature.
The most obvious technical difference occurs in the ‘SS’ bits in the H2 pointer byte
of the Section OverHead (SOH) / Transport OverHead (TOH). The terminology on
the instrument display is mainly ETSI. A table of ETSI / ANSI equivalent terms is
given at the rear of this manual.
SDH / SONET is capable of transporting all the common tributary signals
E1 (2.048 Mb/s), E3 (34.368 Mb/s), E4 (139.264 Mb/s), DS1 (1.544 Mb/s) and DS3
(44.736 Mb/s) currently in use. In addition SDH / SONET has the flexibility to
readily accommodate any new types of service which are being introduced for
example (ATM) or which may be required in the future. Approximately 5% of the
SDH / SONET signal structure (Overhead) is reserved for network management
and maintenance.
This means that SDH / SONET can be deployed as an overlay to the existing
network thus providing enhanced network flexibility.
The HP 37717C provides comprehensive testing of both payload and overhead at
electrical and optical SDH / SONET interfaces.
2
SDH / SONET Modules
SDH / SONET Options
SDH / SONET Options
SDH / SONET options are available according to your testing needs:
Option US1 (US5)
Provides an STM-1 Electrical interface. (When Option UH1 is fitted
provides an STM-1 Optical interface. When Option UH2, URU, USN or
UKT is fitted provides STM-1 and STM-4 optical interfaces.)
Provides frequency offset of the SDH signal of ±999 ppm.
Payloads of 140 Mb/s, 34 Mb/s and 2 Mb/s are available.(If Option UKJ
U.S.A. Structured PDH is fitted, Structured Payloads are available and a
2Mb/s Insert port is provided.)
Bit errors can be added to the Payload.
Allows Errors & Alarms to be added to the SDH signal.
The K1K2 MSP bytes can be user programmed
The S1 byte can be user programmed.
3
SDH / SONET Modules
SDH / SONET Options
Option A1T (A1U)
Provides an STM-1 Electrical interface. (When Option UH1 is fitted
provides an STM-1 Optical interface. When Option UH2, URU, USN or
UKT is fitted provides STM-1 and STM-4 optical interface.)
When Option UKZ is also fitted, provides an additional OC-3c transmit and
receive facility.
Includes a THRU mode capability such that the Payload and the Section /
Transport Overhead of the incoming STM-1 signal can be overwritten by the
test set.
Provides frequency offset of the SDH / SONET signal of ±999 ppm.
Payloads of 140 Mb/s, TU3, TU2 and TU12 are available.(If Option UKJ
(USA) or UKN (USE) Structured PDH is fitted, Structured Payloads are
available and a 2Mb/s, 34 Mb/sand 140 Mb/s Insert port is provided). Bit
errors can be added to the Payload.
Allows Errors & Alarms to be added to the SDH / SONET signal.
Pointer Movements can be added to the SDH / SONET signal and a
Graphical display of Pointer activities available.
Section / Transport and Path Overhead bytes are user programmable and can
be monitored. Overhead byte activity can be captured and displayed.
Allows BER testing of Section / Transport and Path Overhead bytes.
DCC Drop and Insert capability is included.
Optical Clock stress capability is included.
Additional SDH interface capability is provided by the following Options:
STM-1/STM-4 optical interface at 1550 nm, option URU.
STM-1/STM-4 optical interface at 1330 nm and 1550 nm with access to STM-4
overhead and Optical power measurement, option USN.
STM-1/STM-4 optical interface at 1330 nm and 1550 nm with access to STM-4
overhead and Optical power measurement, option UKT.
SDH binary interface for Option UKT and USN only, option 0YH.
4
SDH / SONET Modules
SDH / SONET Features
SDH / SONET Features
Various SDH / SONET features are available with Options US1 (US5) and A1T
(A1U). The use of these features is explained in the following pages:
SDH Settings
SIGNAL selection is normally STM-1. If
Option UH1 is fitted STM-1 OPT is added.
If Option UH2, URU, USN or UKT is
fitted STM-1 OPT and STM-4 OPT are
added.
If Option A1T (A1U) is fitted selection
between INTERNAL and THRU is
available.
CLOCK SYNC can be derived internally
from the test set, from the SDH Master
Timing Source or from the received SDH signal.
FREQUENCY OFFSET allows SDH line rate offset of ± 999 ppm).
PAYLOAD selection is 140 Mb/s, TU3 (34
Mb/s Option US1 (US5)), TU2 (Option
A1T (A1U) only) or TU12 (ASYNC2 Mb/s
Option US1 (US5)).
TU MODE selection sets the Tributary
Mapping mode to ASYNC or FLOATING
BYTE and is only available on Option A1T
(A1U) when TU12 payload is selected.
TU CONCATENATION selection (A1T
(A1U) only) determines the number of TU2
tributaries to be tested.
5
SDH / SONET Modules
SDH / SONET Features
SELECTED TU allows the selection of the Trib utary required for testing which in a
TU12 payload is 1 of 63 Tributaries.
TU PAYLOAD sets the type of payload. If
Unstructured PDH module, Option UKK
(USB), is fitted only UNFRAMED is
available. INSERT 34 Mb/s and INSERT
140 Mb/s are only available when Option
A1T (A1U) is fitted.
P ATTERN allows selection of the T ributary
test pattern.
OFFSET (Option A1T (A1U) only) allows
the tributary payload to be frequency offset
relative to its virtual container (VC-12, VC-3 or VC-4) in the range ± 100 ppm. 2M
OFFSET if payload TU12, 34M OFFSET if payload TU3, 140M OFFSET if
payload 140 Mb/s. This affects the stuff rate but does not cause pointer movements
and can be used to test mapping Jitter.
PATTERN IN OTHER TU’s allows selection of the test pattern inserted in the non
test tributaries.
SONET With ATM Payload, Settings
An ATM payload produced by Options
UKN and UKZ may be transmitted at
STM-1 and OC-3c by the SDH / SONET
Option A1T (A1U). The ATM payload
may then be multiplexed into an OC-12
signal with the dual wavelength (1310 /
1550 nm) Option USN.
NOTE: the OC-12 is not 622Mb/s ATM
(OC-12c)
6
SDH / SONET Modules
SDH / SONET Features
The signal received by the ATM module
(UKN or UKZ) may be retransmitted by
selecting THRU mode. Jitter from the
jitter generator module may be added to
the retransmitted signal.
For ATM testing at STM-1, the ATM
receiver of Option UKZ receives an
ATM payload from Option A1T (A1U).
For ATM testing at OC-3c or STM-1
within an OC-12, the dual wavelength
(1310 / 1550 nm) module Option USN is
required.
NOTE: the OC-12 is not 622Mb/s ATM
(OC-12c)
STM-1 THRU Mode (Option A1T (A1U) only)
The primary purpose of THRU mode is to non-intrusively monitor SDH / SONET
lines where no protected monitor points are available.
THRU Mode allows a ne w Payload and/or
Section Overhead to be substituted in the
received STM-1 SDH signal for test
purposes.
If PAYLOAD OVERWRITE [OFF] and
SOH+POH CHANNEL OVERWRITE
[OFF] are both selected the SDH signal is
retransmitted without alteration.
The B1, B2 and B3 BIPS are not
recalculated.
7
SDH / SONET Modules
SDH / SONET Features
When PAYLOAD OVERWRITE [AU4] is
selected a user selectable Payload can be
substituted for the received SDH payload.
A new path overhead is generated and the
B3 BIP is recalculated.
The payload is selected as for SDH Internal
mode.
When SOH+POH OVERWRITE [ON] is
selected new Section / Transport and Path
Overhead, is substituted for the received
overhead. The B1, B2 and B3 Bips are
recalculated.
The user can only modify certain overhead
bytes by using one of the TRANSMIT test
functions: Errors & Alarms, Sequences,
Overhead BER, MSP Messages, DCC
Insert and Stress Test.
The overhead cannot be modified using OVERHEAD SETUP.
STM-4 THRU Mode (Option A1T (A1U) and UKT or USN only)
Provides a non-intrusive monitor of the
STM-4 signal where no protected monitor
points are available. Neither the payload or
overhead can be altered and the received
signal is retransmitted unchanged.
8
SDH / SONET Modules
SDH / SONET Features
Transmit Static Overhead (Option A1T (A1U) only)
It can be desirable to set an overhead byte to a known static state to aid in
troubleshooting, for example, to quickly check for “stuck bits” in path overhead
bytes. This capability is provided under TRANSMIT OVERHEAD SETUP.
Path Overhead
The value of each bit of VC4 path overhead bytes: C2, F2, G1, H4, Z3, Z4 and Z5
can be set to 0 or 1. Byte B3 cannot be set. If TRANSMIT PAYLOAD [TU3] is
selected the value of each bit of VC3 path overhead bytes C2, G1, F2, Z3, Z4 and Z5
can be set to 0 or 1.
An overhead byte cannot be set to a static value if a TEST FUNCTION is active in
that byte, for example: If the ERROR & ALARMS Test Function is selected, and
TU PATH UNEQUIPPED alarm is set, the value of C2 will be determined by the
Alarm selection.
If TRANSMIT PAYLOAD [TU2] or [TU12] is selected H4 byte is set to carry a
SEQUENCE. Selection between ;
and is available.
COC1 SEQUENCE
The Signal Label value for VC-2 or VC-12 can also be set.
FULL SEQUENCE
REDUCED SEQUENCE
Path Trace The path trace capability allows:
A user selected data message to be inserted in the appropriate J1 byte to verify
the VC-3 or VC-4 path connection
A user selected data message to be inserted in the appropriate J2 byte to verify
the VC-2 or VC-12 path connection.
V C-3/VC-4 Path Trace
1 Press ; ;
OVERHEAD SETUP
TRANSMIT
SDH
and using
and the display softkeys set
up the display as shown
TRANSMIT
opposite.
2. Selection of
DEFAULT MESSAGE
programs the J1 byte to carry 64 ASCII
Null characters.
9
SDH / SONET Modules
SDH / SONET Features
3. Selection of
TEST MESSAGE
programs the J1 byte to carry the displayed
HP 37717C test message.
4. Selection of allows
USER MESSAGE
the user to program the message content of
the J1 byte with up to 62 ASCII characters
followed by CR LF.
5. Selection of allows
CRC7 MESSAGE
the user to program the message content of
the J1 byte with up to 15 ASCII characters
(padded out with ASCII Null characters if
necessary) followed by a frame marker
byte with CRC7.
10
SDH / SONET Modules
SDH / SONET Features
VC-2/VC-12 Path Trace
6. Selection of
DEFAULT MESSAGE
programs the J2 byte to carry 16 ASCII
Null characters.
Selection of programs
TEST MESSAGE
the J2 byte to carry the test set Serial
number.
Selection of allo ws the
USER MESSAGE
user to program the message content of the
J2 byte with up to 14 ASCII characters
followed by CR LF.
The VC-2 or VC-12 Signal Label value
can be set in the range 000 to 111.
Section / Transport Overhead
The value of each bit of Section / Transport overhead bytes in columns 1,4,7:
A1,A2; C1; E1; F1; D1 - D3; K1,K2; D4 - D12; Z1; Z2 and E2 can be set to 0 or 1.
Only bits 5 and 6 of byte H1 can be set to 0 or 1. Bytes B1, B2, H2 and H3 cannot be
set at any time.
If columns 2,5,8 or 3,6,9 are selected only bytes A1,A2; H1 - H3; B2; Z1 and Z2 are
labelled as the other overhead functions have not yet been defined. The v alue of each
bit of Section / Transport ov erhead bytes: A1,A2; H1; H2; Z1; Z2 and all the bits of
the unlabeled functions can be set to 0 or 1. Bytes B2 and H3 cannot be set at any
time.
An overhead byte cannot be set to a static value if a TEST FUNCTION is active in
that byte, for example: If the MSP MESSAGES Test Function is selected then
K1,K2 value will be determined by the MSP MESSAGES selections.
Setting Undefined Overhead Functions For test purposes it may be important to
be able set the value of those overhead functions which are presently undefined (Z2)
or unlabeled as in columns 2,5,8 and 3,6,9.
11
SDH / SONET Modules
SDH / SONET Features
1. Press ; ;
OVERHEAD SETUP
TRANSMIT
SDH
and using
and set up the
TRANSMIT display as shown opposite
2. In this example the Z2 byte can be set
in the range 00000000 to 11111111
using the display softkeys.
Static Overhead Known (Default) Conditions
After testing it may be desirable to return the static overhead to the known (default)
state using one of the methods shown below.
1. Set up the ;
SETUP
TRANSMIT
OVERHEAD
display as shown opposite. This
returns overhead, not set by a TRANSMIT
test function to the known (default) state.
Any overhead byte set by a TEST
FUNCTION will not be returned to the
default state, for example:
If the MSP MESSAGES Test Function is
selected then K1,K2 value will be
determined by the MSP MESSAGES
selections.
2. Set up the ;
SETTINGS
OTHER
STORED
display as shown opposite.
This returns all settings, including
Overhead and TRANSMIT T est Functions,
to the known(default) state.
12
SDH / SONET Modules
SDH / SONET Features
Transmit Overhead Sequence
It can be desirable to insert a pattern into a functional group of overhead bytes for
testing or troubleshooting purposes. This capability is provided under TRANSMIT
SDH TEST FUNCTION SEQUENCE.
Overhead Bytes
Sequences can be inserted into 3XA13XA2 (Framing), C1, E1, F1, D1-D3
(Regenerator Section / Transport Overhead); K1K2, D4-D12, S1, Z1 column 2, Z1
column 3, Z2 column 4, Z2 column 5, E2 (Multiplexer Section / Transport
Overhead) and J1, C2, G1, F2, H4, Z3, Z4 or Z5 (Path Overhead).
If TRANSMIT PAYLOAD [TU2] or [TU12] is selected sequences can only be
inserted into the H4 byte using ; .
The sequence is derived from 5, user defined, hexadecimal blocks of data. Each
block of data can be transmitted in up to 64000 frames.
The sequence can be run once only SINGLE RUN, or on a repetitiv e basis REPEAT
RUN.
Transmit Frame Synchronization Sequence
1. Press ;
FUNCTION
TRANSMIT
and using
SDH TEST
and and the display softkeys set up the
display as shown opposite.
TRANSMIT
OVERHEAD SETUP
Press to start the sequence. As
STARTED
a result of this sequence one OOF alarm
and one LOF alarm should occur every two
seconds.
13
SDH / SONET Modules
SDH / SONET Features
Receive Overhead Monitor
When first connecting to a network a start-up confidence check can be made by
viewing the behavior of all the overhead bytes. If the network shows alarm
indications, some diagnosis of the problem may be gained from viewing all the
overhead bytes. This facility is provided on the RECEIVE display under
OVERHEAD MONITOR
All path overhead bytes are monitored and
displayed. VC4 path overhead is shown
opposite. If TRANSMIT PAYLOAD
[TU3] is selected VC-3 path overhead can
be monitored and displayed. If
TRANSMIT PAYLOAD [TU12] is
selected VC-12 path overhead can be
monitored and displayed.
The display is updated once per second
(once per 8000 frames approximately).
.
STATUS: Loss of frame alarm
All Section / Transport overhead bytes
are monitored and displayed as shown
opposite.
The display is updated once per second
(once per 8000 frames approximately).
If any abnormal behavior is observed on a particular path or Section / Transport
overhead byte, or an associated group of bytes (3XA1,3XA2; D1 - D3) the
RECEIVE
TEST FUNCTION
OVERHEAD CAPTURE
; display of can be used
to “zoom” in on the suspect byte, or bytes, on a frame by frame basis.
14
SDH / SONET Modules
SDH / SONET Features
Receive Overhead Capture
Regenerator Section / Transport, Multiplexer Section / Transport and Path overhead
provide network support functions, responding dynamically to network conditions
and needs. It is therefore desirable to be able to capture overhead activity on a frame
by frame basis. This capability is provided under ; ;
TEST FUNCTION
;.
OVERHEAD CAPTURE
RECEIVE
Overhead Capture allows selection of the starting point of the capture by means of
Trigger selection:
Trigger OFF start immediately the capture is initiated
Trigger ON capture activity after a specified overhead state has occurred
Trigger ON NOT capture activity after the first occurrence of a deviation from a
specified overhead state.
Trigger OFF can be used to provide a “frame by frame monitor” of the selected
byte, or bytes, immediately the capture is initiated.
Trigger ON and ON NOT can be used for “transient detection” from a specified
expected state.
SDH
The overhead capture feature provides up to 16 records of overhead state. Each
record will represent between 1 and 64,000 frames. A capture is started by
pressing and terminates when 16 records have been captured. The
capture can be terminated sooner by pressing .
STARTED
STOPPED
Frame by Frame Monitor of H1,H2
The frame by frame monitor capability provides a “zoom” in version of the Receiv e
Overhead Monitor feature using the Trigger OFF condition of overhead capture.
1. Press ; ;
FUNCTION
RECEIVE
;
SDH TEST
OVERHEAD CAPTURE
and using and and
the display softkeys set up the
RECEIVE
display as shown opposite.
Press to start the capture.
STARTED
15
SDH / SONET Modules
SDH / SONET Features
Transient Detection on A1,A1,A1,A2,A2,A2
Under normal operating conditions the A1,A2 bytes will remain in a known stable
state (F6F6F6282828). Using the Trigger ON NOT condition of the Overhead
Capture, any transient deviations from that state can be detected.
1. Press ; ; ;
FUNCTION
RECEIVE
;
SDH TEST
OVERHEAD CAPTURE
and using and and the
display softkeys set up the
RECEIVE
display as shown opposite.
Press to start the capture.
STARTED
Errors and Alarms
TRANSMIT
PAYLOAD
be added to the payload.
TRANSMIT
SDH ERRORS & ALARMS
Errors and Alarms to be added to the SDH
Overhead.
;;
TEST FUNCTION PDH
ERRORS allows Bit errors to
;;
TEST FUNCTION
; allows
16
SDH / SONET Modules
SDH / SONET Features
Overhead Bit Error Rate (A1T
(A1U) only)
1. The ;
TRANSMIT
OVERHEAD BER
test function inserts a 29-1 PRBS test
pattern into the user selected byte of,
Regenerator Section / Transport,
Multiplexer Section / Transport or Path,
overhead.
Single bit errors can be added to the PRBS
test pattern.
2. The ; test
RECEIVE
OVERHEAD BER
function counts the errors present in the
PRBS test pattern within the user selected
overhead byte.
Results of Error Seconds, Error Ratio, Error
Free Seconds,% Error Free Seconds, Pattern
Loss Seconds and Elapsed Time are
displayed.
Add Pointer Adjustments (A1T (A1U) only)
The ; test function allows the transmitted AU or
TRANSMIT
TU pointer value to be changed for testing purposes in four different ways:
ADJUST POINTER
1. provides a burst of pointers.
BURST
The size of the burst is determined by the
number of PLACES selected. In this
example 5 PLACES are selected and the
pointer value will be stepped five times in
unit steps e.g. 0 (start value), 1, 2, 3, 4, 5
(final value). The interval between steps is
4 frames (500 us).
The direction of change is determined by
the , ,
INCREMENT DECREMENT
ALTERNATE
If is selected the burst will be in the opposite direction to the
ALTERNATE
selection.
preceding burst.
The burst is transmitted when ADJUST POINTER is selected.
ACTION
17
SDH / SONET Modules
SDH / SONET Features
2. allows a user defined
NEXT SUMMARY
pointer value to be transmitted in the range
0 to 782, with or without a New Data Flag
(NDF). A NDF signifies a controlled
change of Payload.
The current Pointer value is displayed for
reference. The New Pointer is transmitted
when ADJUST POINTER is
ACTION
selected.
3. allows either the line rate or
OFFSET
the VC/TU rate to be frequency offset,
relative to each other, by up to ±100 ppm
thus producing pointer movements.
When a VC-4 is offset relative to the line
rate the 87:3 sequence of pointer
movements is generated.
If the line rate is offset the TU rate is locked
to the reference. If the TU rate is offset the
line rate is locked to the reference.
4. provides pointer movement
G.783
sequences as per ITU G.783:
a. Periodic Single adjustments, each with
opposite polarity to the preceding
adjustment.
b. Periodic Single adjustments, with
selectable polarity and added adjustment (1
extra). The added adjustment occurs 4
frames (500) after a periodic
adjustment.The sequence has a repetition rate of approximately 30 seconds.
c. Periodic Single adjustments, with selectable polarity and cancelled adjustment (1
less). The sequence has a repetition rate of approximately 30 seconds.
18
SDH / SONET Modules
SDH / SONET Features
d. Periodic Double adjustments (pair of adjustments). The pair alternate in polarity.
The spacing between pairs of adjustments, of like polarity, is 4 frames (500).
In all cases the interval between adjustments (between pairs in d) is user selectable.
The sequence is started by selecting POINTER SEQUENCES .
STARTED
Pointer Graph (A1T (A1U) only)
The ; test
RECEIVE
function provides a graphical display of
pointer movements.
The capture interval is user programmable.
POINTER GRAPH
19
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