LeCroy MT01 Book

Operator’s Manual

Mask Tester
for LeCroy
Digital Oscilloscopes

October 2000

LeCroy Corporation

700 Chestnut Ridge Road
Chestnut Ridge, NY 10977–6499
Tel: [phone], Fax: [phone]

Internet: www.lecroy.com

Copyright © 2000, LeCroy. All rights reserved. Information in this publication supersedes all earlier
versions. Specifications subject to change.

LeCroy is a registered trademark of LeCroy Corporation.
MT-OM-E Rev E 1000

Contents

Introduction ............................................................................1

Preparing the Test .................................................................. 3

Choosing the Right Adapter for the Right Signal .............3

Setting Up the Oscilloscope ..................................................4

Running the Test .................................................................... 5

Selecting.............................................................................. 5

Adjusting the Trace.............................................................6

Slice Width......................................................................... 10

Dark Cal .............................................................................11

TBR Parameter ..................................................................12

The Test Options............................................................... 13

Testing............................................................................... 14

Mask Testing Remote Control Commands..........................18

Appendix A: Specifications..................................................25

MT-OM-E Rev E ISSUED: October 2000 iii

BLANK PAGE

iv ISSUED: October 2000 MT-OM-E Rev E

Introduction

The Problem Oscilloscopes are commonly used in the telecommunications

industry to perform “Mask Testing” — a check of whether the
signal shape falls within a particular defined tolerance.

However, performing such mask tests can quickly become
frustrating, for the following reasons:

Ø The oscilloscope is a general-purpose instrument that is not

optimized for any specific application. Setting it up for mask
testing can be particularly tedious.

Ø Some adjustments, particularly horizontal ones, need to be

performed frequently during mask testing. Making these
adjustments manually is not only cumbersome, but may
even be impossible if the oscilloscope is used in an
automated test station.

Ø Some tests require either amplitude and peak adjustment or

special triggering to isolate the correct pattern — also
difficult if not impossible to achieve using a standard
oscilloscope.

The Solution LeCroy’s innovative Mask Tester application is designed to

address these issues and is ideal for Manufacturing Testing,
Type Approval and Field Testing applications. The Mask Tester
supports the major electrical bit rates in telephony, from both
ITU G.703 and ANSI T1.102 standards, and the optical
telecommunication standards, ITU-T G.957 and ANSI T1.105.
Its leading features include:

Ø One-step loading of masks and instrument setups
Ø Mask–to–signal alignment even on random bit streams
Ø Choice of fail actions such as screen printout, “beep”, “stop

test” and “store failed trace”

Ø A complete set of twisted-pair and 75 Ω adapters, providing

accurate cable termination and amplitude scaling.

Available Mask Tests The Mask Tester application supports both ANSI and ITU-T

standards. LeCroy’s MT01 supports most ITU-T G.703 masks,

MT-OM-E Rev E ISSUED: October 2000 1

MT02 supports most ANSI T1.102 masks, and MT03 supports most
ITU-T G.957 standards and their ANSI T1.105 equivalents. Bundled
packages, such as MT01/02, are also available.

MT01 — ITU G.703

Signal Bit Rate Line Impedance LeCroy Adapter

E-1 2.048 Mb/s
E-1 2.048 Mb/s
E-2 8.448 Mb/s
E-3 34.368 Mb/s
E-4 139.264 Mb/s

STM-1E

†

155.520 Mb/s

120 Ω twisted pair

75 Ω coax
75 Ω coax
75 Ω coax
75 Ω coax
75 Ω coax

AP120
PP090
PP090
PP090
PP090
PP090

MT02 — ANSI T1.102-1993

Signal Bit Rate Line Impedance LeCroy Adapter

DS-1 1.544 Mb/s
DS-3 44.736 Mb/s

STS-1 51.840 Mb/s

†

STS-3E

155.520 Mb/s

100 Ω twisted pair

75 Ω coax
75 Ω coax
75 Ω coax

AP100
PP090
PP090
PP090

MT03* — ITU-T G.957 and ANSI T1.105-1996

Signal Bit Rate Medium LeCroy Adapter

OC3/STM-1 155.520 Mb/s Singlemode optical fiber OE325

OC12/STM-4 622.080 Mb/s Singlemode optical fiber OE325

* MT03 is limited to oscilloscope models with a bandwidth = 1 GHz and a sample rate = 4 GS/s

†

STM-1E and STS-3E in the MT01 and MT02 packages, respectively, are limited to oscilloscope
models with a bandwidth = 500 MHz and a sample rate of = 1 GS/s

2 ISSUED: October 2000 MT-OM-E Rev E

Preparing the Test

Choosing the Right Adapter for the Right Signal

75 Ω Coax Signals Plug in the PP090 on the oscilloscope’s desired channel

connector. The PP090 will provide the correct 75 Ω impedance

adaptation.

Then connect your signal using a 75 Ω cable to the PP090.

Twisted-Pair Signals Use the appropriate adapter supplied in your package:

Ø For DS-1 signals, use the AP100.
Ø For 2 Mb/s twisted pairs, use the AP120.

These adapters automatically ensure proper termination,
convert the balanced signal into an unbalanced 50 Ω input, and
scale the amplitude with the appropriate factor.

Optical Signals Use the OE325 optical-to-electrical converter supplied in

your package. The OE325 can be used on any scope channel for

optical signal analysis. By plugging the OE325 into a matched
scope channel (see back of OE325 for matching scope serial
number and channel), reference receiver processing capability is
provided as required for STM-1/OC3 or STM-4/OC12 compliance
mask testing.

Test Signal Configuration

All tested signals can be random-bit streams, for optimum
convenience and flexibility.

If the signal is not random or PRBS, ensure that it contains
valid isolation patterns so that the oscilloscope’s pulse
isolating mechanism can operate properly. The required

isolation patterns are described in Appendix A.

MT-OM-E Rev E ISSUED: October 2000 3

Setting Up the Oscilloscope

1. Power up the oscilloscope.

2. If you purchased the MT01, MT02, MT01/02 or MT01/02/03
options, plug in the SRAM card containing the masks and
instrument setups in the slot located on the lower right-hand
side of the front panel. The MT03 option does not require a
SRAM card.

3. Press the ANALYSIS PACKAGES front panel button on the
WavpPro DSO (CURSORS /M EASURE on other scopes) . On the
DDA, press CURSORS, then select Analysis Packages from
the “WAVE PILOT” menu.

4. Select the MASK TESTER menu. The oscilloscope is now in
“Mask Tester” mode and is dedicated to mask testing. The
oscilloscope can now only be controlled by using the seven
menu buttons and the two menu knobs associated with the
bottom two buttons. Each of these buttons and knobs
corresponds to, and controls, the on-screen menu appearing
beside it. Beneath them on the scope front panel is the
RETURN button, an important navigation control that
enables you to return to the next higher menu level and to
exit the Mask Tester mode.

Tip: After exiting the Mask Tester mode, the previously
selected telecom mask will no longer be displayed.
However, for MT01 and MT02, the mask is still assigned to a
scope zoom trace and can be displayed by turning the
corresponding trace on.

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Running the Test

Selecting

signal type

NEXT...

The test proceeds in three steps:

1. Selecting the signal type

2. Adjusting the trace, and the test options

3. Testing.

The following pages detail these steps.

This is the top menu. Scroll through the list to select the
appropriate signal type using the two top-most menu buttons
alongside the menu.

When applying the Optical masks, you will have the further
choice of applying Reference Receiver filtering or not. The
Reference Receiver must be enabled for STM-1/OC3 or STM­4/OC12 compliance testing.

Press the corresponding menu button beside this menu to
access the “TRACE ADJUST” trace adjustment and test options
menus (shown next page).

source

Select the desired channel and connect the signal under test to
it using the appropriate adapter ( see above and page 13). To
enable Reference Receiver processing, the OE325 must be
plugged into the matching scope channel as designated on the
back of the OE325.

MT-OM-E Rev E ISSUED: October 2000 5

Adjusting the Trace

Case 1 Simple Masks in Volts (ITU 2, 8, 34 Mb/s)

If test fails, do...

Press the button corresponding to this menu to choose the
action the oscilloscope should perform when a trace fails ( see
page 13).

HORIZONTAL ALIGN

Pressing the button for this menu causes the instrument to
recalculate its trigger position to readjust the signal to the mask.

attenuation factor

Use the knob associated with this menu to compensate for any
amplitude loss caused by the signal path. Pressing the
corresponding menu button resets the value to 1.

DO TEST NOW

Once all adjustments and action setups have been made, start
the test using this menu’s button.

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Case 2 CMI masks (STM-1E, STS-3E and 139 Mb/s)

If test fails, do...

Press the button corresponding to this menu to choose the
action the oscilloscope should perform when a trace fails ( see
page 13).

VERTICAL ALIGN

Press this menu’s button to adjust the signal offset, possible
within a ±50 mV range. If the required adjustment is outside this
range, the warning message “Offset out of range, cannot do
test” will be displayed.

HORIZONTAL ALIGN

Pressing the corresponding button causes the instrument to
recalculate its trigger position and readjust the signal to the
mask.

attenuation factor

Use the knob associated with this menu to compensate for any
amplitude loss caused by the signal path. Pressing the menu
button resets the value to 1.

DO TEST NOW

Once all adjustments and action setups have been made, start
the test using this menu control.

MT-OM-E Rev E ISSUED: October 2000 7

Case 3 Normalized masks (ANSI DS-1, DS-3, STS-1)

If test fails, do...

Press the button corresponding to this menu to choose the
action the oscilloscope should perform when a trace fails ( see
page 13).

AUTO-FIT TO MASK

Pressing the corresponding button will cause the signal to be re­normalized to its mask; amplitude and trigger position will be
readjusted.

averaging

The signal under test can be averaged using this button. The knob
selects the continuous averaging weighting.

DO TEST NOW

Once all adjustments and action setups have been made, start
the test using this control ( page 14).

8 ISSUED: October 2000 MT-OM-E Rev E

Case 4 Optical signal masks (STM-1/OC3, STM-4/OC12)

If test fails, do...

Press the button corresponding to this menu to choose the
action the oscilloscope should perform when a trace fails ( see
page 13).

AUTO-FIT TO MASK

Pressing the corresponding button will cause the signal to be re­normalized to its mask; amplitude and trigger position will be
readjusted.

DO TEST NOW

Once all adjustments and action setups have been made, start
the test using this control ( page 14).

Note: To remove the STM-1 or STM-4 masks prior to leaving the MT
mode of operation, return to the Telecom Setup menu set.

MT-OM-E Rev E ISSUED: October 2000 9

Slice Width

In cases when mask testing is required only over a limited
portion of the mask, use the "slice width" function. The area on
which the test will be performed is bounded by two cursors. It is
possible to select either 5%, 10%, 20%, or 100% of the mask
area. When a different value is set, the cursors accordingly
move to the new setting. (See the figure below.)

The slice width option is only available if one of the MT03
optical packages (OC3 or OC12) is selected in the signal type
menu, as shown at left.

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Dark Cal

Description:
This function determines the value seen by the scope with no

input signal applied. The Dark Cal measurement establishes a
reference for accurate top and base measurements.

To perform the Dark Calibration:

1. From the “TRACE ADJUST” menu, select DARK CAL to
access the “DARK CAL” menu.

2. Disconnect the light source and cover the OE325 input
connection.

3. Select Continue to perform the dark calibration.

The scope will acquire the input signal for a few seconds, then
return to the TRACE ADJUST menu. The calculated adjustment
is displayed inside the Dark Cal menu selection. This value can
also be adjusted manually in the range –99 to 99 [µW] in steps
of 0.01 [µW].

If the scope’s internal calibration takes place during a dark
calibration, repeat the dark calibration to obtain an accurate
measurement.

MT-OM-E Rev E ISSUED: October 2000 11

TBR Parameter

Description:
The TBR (Top to Base Ratio) parameter is used to measure the

ratio of top to base for power signals. The measurement can be
expressed as

• top to base ratio

• base to top in percent

• top to base in dB.

The offset for top and base can be adjusted in the range –99 to
99 [µW] in steps of 0.01 [µW].

1. Extension to the PARAMETER_CUSTOM command/query

COMMAND SYNTAX PACU <line>,TBR,<source>,<mesurement_type>

<line>:= 1 to 5
<mesurement_type>:={TB,BTP,TBDB}

TB = top/base
BTP = base/top in %
TBDB = top/base in dB

2. PARAMETER_VALUE Query

QUERY SYNTAX <trace>:PAVA? TBR

<trace>:={TA,TB,TC,TD,C1,C2,C3,C4}
PAVA? CUST<line>
<line>:= 1 to 5

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The Test Options The menus shown on this page are displayed when the “If test

fails, do” menu button is pressed. They determine what the
instrument does when a trace fails the test.

stop

Select “Yes” with the corresponding button to stop the
acquisition.

store

Select “Yes” here to store the failed trace to memory card.

hardcopy

“Yes” to make a hard copy of the screen using the internal
printer.

beep

“Yes” to emit a sound.

MT-OM-E Rev E ISSUED: October 2000 13

Testing These menus are displayed when the “DO TEST NOW” menu

button is pressed.

Case 1 2, 8 and 34 Mb/s

PAUSE/CONTINUE

Press this menu’s button to pause or continue the test without
resetting the pass/fail count.

polarity

Use the corresponding button to toggle between positive and
negative pulses. The pass/fail counter will be reset.

STOP TEST NOW

Press the corresponding button to stop the test. The pass/fail
counter will be reset.

14 ISSUED: October 2000 MT-OM-E Rev E

Case 2 STM-1E, STS-3E and 139 Mb/s

PAUSE/CONTINUE

Press this menu’s button to pause or continue the test without
resetting the pass/fail count.

symbol

Press the corresponding button to toggle between “1” and “0”
patterns. The pass/fail counter will be reset.

STOP TEST NOW

Press the corresponding button to stop the test. The pass/fail
counter will be reset.

MT-OM-E Rev E ISSUED: October 2000 15

Case 3 DS-1, DS-3 and STS-1

PAUSE/CONTINUE

Press this menu’s button to pause or continue the test without
resetting the pass/fail count.

polarity

Use the corresponding button to toggle between positive and
negative pulses. The pass/fail counter will be reset.

STOP TEST NOW

Press the corresponding button to stop the test. The pass/fail
counter will be reset.

16 ISSUED: October 2000 MT-OM-E Rev E

Case 4 STM-1, STM-4, OC3 and OC12

PAUSE/CONTINUE

Press this menu’s button to pause or continue the test without
resetting the pass/fail count.

Automatic Measurements

For optical signal tests five automatic measurements are
displayed below the PAUSE menu. It is recommended that
these measurements be performed with the Reference Receiver
turned on to condition the signal prior to measurement.
Extinction ratio: 10 Log Top/Base. If the base value is
determined to be below 300 nW, which is the lowest power level
MT03 can accurately resolve, a ”>" is shown indicating that the
Extinction ratio is at least the value displayed.

Pwr: (Top + Base)/2. This is equivalent to mean launched
power for 1310 nm optical signals. For 1550 nm signals, multiply
by the constant value as shown on the OE325 calibration
certificate to determine mean launched power.

X(fit): Signal rising and falling edge-crossing point. This
measurement is determined during the auto fit to mask.

Top: The average power of light on.
Base: The average power of light off.

STOP TEST NOW

Press the corresponding button to stop the test. The pass/fail
counter will be reset.

MT-OM-E Rev E ISSUED: October 2000 17

Mask Testing Remote Control Commands

IDENTIFICATION

DESCRIPTION The CU_OPT? query identifies options currently enabled due to the

presence of a PP100. These options can also be enabled by the
normal ‘option key’ mechanism. If so, they are reported by the
*OPT? query instead of CU_OPT?. The response to CU_OPT?
consists of a series of response fields listing all the options enabled
due to the presence of a PP100.

QUERY SYNTAX CU_OPT?

RESPONSE FORMAT CU_OPT <option_1>, <option_2>,...,<option_n>

<option_n> = MT01: Mask Tester option for ITU

MT02: Mask Tester option for ANSI
MT03: Mask Tester for Optical Signals
0: No custom options installed

CU_OPT?

Query

CUSTOM_APPLICATION, CUAP

Command/Query

DESCRIPTION The CUSTOM_APPLICATION command toggles from Mask

Tester mode to standard oscilloscope mode.

COMMAND SYNTAX CUSTOM_APPLICATION <state>

QUERY SYNTAX CUSTOM_APPLICATION?

RESPONSE FORMAT CUSTOM_APPLICATION <state>

<state> = OFF for the standard oscilloscope state

18 ISSUED: October 2000 MT-OM-E Rev E

MASK_TESTER for the Mask Tester state

MT-OM-E Rev E ISSUED: October 2000 19

SELECTING

DESCRIPTION The MT_SELECT_TEST command selects the signal/test type,

and performs “AUTOALIGN” or “HORIZONTAL ALIGN” actions
automatically on the signal.

MT_SELECT_TEST

Command/Query

COMMAND SYNTAX MT_SELECT_TEST <test_name>, <channel>G, <averaging>

QUERY SYNTAX MT_SELECT_TEST?

RESPONSE FORMAT MT_SELECT_TEST <test_name>, <channel>, <averaging>

<test_name> = NO_TEST if no test selected
<test_name> = {2M_TP, 2M_COAX, 8M, 34M, 139M, 156M,
DS1, DS3, STS1, STS3E, OC3, OC12

Note: OC3 and OC12 are equivalent to STM-1 and STM-4
signals, respectively.

G

AVAILABILITY <channel>

On four-channel oscilloscopes:

for 2M_TP, 2M_COAX, 8M, DS1: {C1, C2, C3, C4}
for 34M, 139M, 156M, DS3, STS1, STS3E: {C2, C3}

On two-channel oscilloscopes:

for 2M_TP, 2M_COAX, 8M, DS1: {C1, C2}
for 34M, 139M, 156M, DS3, STS1, STS3E: {C2}

<averaging> available only for DS1, DS3, STS1

Note: Autoalign and Horizontal Align actions are performed
automatically using the MT_SELECT_TEST command.

G

20 ISSUED: October 2000 MT-OM-E Rev E

OPERATION
COMPLETE

DESCRIPTION The MT_OPC? (Operation Complete) query checks the

completion of the following commands.
MT_SELECT_TEST
MT_VERTICAL_ALIGN
MT_SYMBOL
The query returns a “0” when the command is not completed,
and a “1” otherwise.

QUERY SYNTAX MT_OPC?

RESPONSE FORMAT MT_OPC <state>

<state> = {0, 1}

MT_OPC?

Query

MT-OM-E Rev E ISSUED: October 2000 21

ADJUSTING

DESCRIPTION Performs offset alignment for STM-1E, STS-3E and 139M.

COMMAND SYNTAX MT_VERTICAL_ALIGN

MT_VERTICAL_ALIGN

Command

MT_OFFSET?

DESCRIPTION Returns the offset value for STM-1E, STS-3E and 139M.

QUERY SYNTAX MT_OFFSET?

RESPONSE FORMAT MT_OFFSET <offset_value> mV

MT_ATTENUATION

Command/Query

Query

DESCRIPTION Controls cable attenuation factor for 2M_TP, 2M_COAX, 8M, 34M,

139M, 156M.

COMMAND SYNTAX MT_ATTENUATION <attn_value>

QUERY SYNTAX MT_ATTENUATION?

RESPONSE FORMAT MT_ATTENUATION <attn_value>

<attn_value> = value between 0.5 and 1

22 ISSUED: October 2000 MT-OM-E Rev E

ADJUSTING

DESCRIPTION Controls the actions the instrument should perform when a test fails.

COMMAND SYNTAX MT_FAIL_ACTION <action>[,<action>]

QUERY SYNTAX MT_FAIL_ACTION?

RESPONSE FORMAT MT_FAIL_ACTION <action>[,<action>]

<action> := {STOP, STORE, DUMP, BEEP}

MT_FAIL_ACTION

Command/Query

MT_OPTICAL_PARAMS?

Query

DESCRIPTION Returns optical signal measurement parameter values automatically

displayed for STM1/OC3 and STM4/OC12 tests

QUERY SYNTAX MT_OPTICAL_PARAMS?

RESPONSE FORMAT MT_OPTICAL_PARAMS <extinction ratio dB>, <mean power

dBm>,

Note: reads out the last values computed for display on the OC3 or OC12 test menu. It does not
cause computation. If this query is executed before any values have been computed, it returns:

MT_OPTICAL_PARAMS 0.00dB,-99.90dBm,0.0%,-99.90dBm,-99.90dBm
Extinction ratio defaults to 0 dB and mean power to –99.9 dB if top is negative. If top is

negative, there is probably no signal. The base value is constrained to be at least 300 nW and
not less than 0.0063095 times (22 dB below) the top; that is the calibration specification on the
OE325. If the base is clipped, the screen shows a “>” in front of the extinction ratio, a “<” in front
of the base, and if the change in power would be greater than 1%, a “<” in front of power. If the
base is clipped, the query returns a 1 for < base_clipped>. An example looks like:

MT_OPTICAL_PARAMS 22.00dB,-8.76dBm, 47.5%,-5.78dBm,-27.78dBm,1

<cross height%>, <topdBm>, <basedBm>, <hbase_clipped>

MT-OM-E Rev E ISSUED: October 2000 23

24 ISSUED: October 2000 MT-OM-E Rev E

TESTING

DESCRIPTION Controls the test execution: RUN/STOP or PAUSE/CONTINUE.

COMMAND SYNTAX MT_TEST_STATE <test_state>

<test_state> := {RUN, STOP, CONTINUE, PAUSE}

QUERY SYNTAX MT_TEST_STATE?

RESPONSE FORMAT MT_TEST_STATE <test_state>

<test_state> := {RUN, STOP, PAUSE, ABORTED}

MT_TEST_STATE

Command/Query

MT_SYMBOL

Command/Query

DESCRIPTION For STM-1E, STS-3E and 139 M selects the “1” or “0” symbol.

For DS1, DS3 and STS1 selects the “POS” or “NEG” pulse.

COMMAND SYNTAX MT_SYMBOL <bit_value>

QUERY SYNTAX MT_SYMBOL?

RESPONSE FORMAT MT_ SYMBOL <bit_value>

<bit_value> := {0, 1, POS, NEG}

MT_PF_COUNTERS

Query

DESCRIPTION Controls the test execution: RUN/STOP or PAUSE/CONTINUE.

QUERY SYNTAX MT_PF_COUNTERS?

RESPONSE FORMAT MT_PF_COUNTERS PASS,266,OF,286,FAIL_RATE,6.903007

MT-OM-E Rev E ISSUED: October 2000 25

PRINT_SERIAL_NUMBER, PRSN?

Query

DESCRIPTION For use with an OE325, this command queries the scope for the

serial number of the OE325, and confirms that it is a correct serial
number match for the scope and channel.

QUERY SYNTAX <channel>:PRSN?

RESPONSE FORMAT C1:PRSN “120200222”

§ § §

26 ISSUED: October 2000 MT-OM-E Rev E

Appendix A: Specifications

Name Bit rate

[Mb/s]

2 M TP
2 M Coax
8 M Coax

34 M

139 M

STM-1E

DS-1

DS-3

STS-1

STS-3E

STM-4/

†

†

2.048 pos/neg

2.048 pos/neg

8.448 pos/neg

34.368 pos/neg

139.264 zero/one

155.520 zero/one

1.544 pos/neg

44.736 pos/neg

51.840 pos/neg

155.520 zero/one

622.080 Light

OC12

Pulse Impedance Coding Isolation

Required

MT01 — ITU-T G.703

120 Ω

75 Ω
75 Ω
75 Ω
75 Ω
75 Ω

HDB3 NO
HDB3 NO
HDB3 NO
HDB3 NO

CMI YES
CMI YES

MT02 — ANSI T1.102

100 Ω

AMI or

YES

B8ZS
75 Ω
75 Ω
75 Ω

B3ZS YES

B3ZS YES

CMI YES

MT03* — ITU-T G.957

- NRZ NO

On/Off

Isolation

Pattern

1010/1001
1010/1001

000010
0000-10

0010/00-10
0010/0010
1010/1001

STM-1/

OC3

* MT03 is limited to oscilloscope models with a bandwidth = 1 GHz and a sample rate = 4 GS/s

†

STM-1E and STS-3E in the MT01 and MT02 packages, respectively, are limited to oscilloscope

155.520 Light
On/Off

- NRZ NO

models with a bandwidth = 500 MHz and a sample rate of = 1 GS/s

§ § §

MT-OM-E Rev E ISSUED: October 2000 27