Keysight Technologies 81490A User manual

Keysight 81490A
Reference Transmitter Module
User’s Guide

Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 1

2Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
Notices
©Keysight Technologies 2017
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Manual Part Number
81490-90A02
Edition
Edition 3.0, October 2017
Subject Matter
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applies directly to all instruments.
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workmanship for a period of one
year from date of shipment. During
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Certification
Keysight Technologies certifies that
this product met its published
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Keysight Technologies further
certifies that its calibration
measurements are traceable to the
United States National Institute of
Standards and Technology, NIST
(formerly the United States
National Bureau of Standards,
NBS) to the extent allowed by the
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Organization members.
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Produced to ISO 9001 international
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our objective of continually
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through improved process control.

Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 3
Table of Contents
Getting Started 5
Safety Considerations 6
Safety Symbols 6
Initial Inspection 6
Line Power Requirements 7
Firmware Requirements 7
Operating Environment 7
Storage and Shipment 7
Environmental Information 8
Laser Safety Information 8
Getting Started with the Reference Transmitter Module 10
What is a Reference Transmitter Module? 10
The Front Panel 11
Optical Output 11
RF Data In 12
Operation 13
Setting the Wavelength 13
Setting the Optical Attenuation 13
Calibrating and Setting the Operating Point 13
Programming Information 17
SCPI Commands 18
New Status Bit 18
New Commands 18
Accessories 21
Recommended Connector Interfaces 22
Specifications 23
Definition of Terms 24
Reference Transmitter Module Specifications 32
General specifications 33

4Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
Performance Tests 35
General 36
General conditions 36
Related information 36
Test Record 36
Test Failure 36
Guaranteed specifications 36
Tests 37
Electrical-optical modulation bandwidth (data output) 37
Eye Mask and Jitter Test 37
Vertical Eye Closure Penalty 43
Optical Wavelength (data output) 46
Keysight 81490A Performance Test Record 47
Cleaning Information 55
Safety Precautions 56
Why is it important to clean optical devices? 57
What do I need for proper cleaning? 58
Preserving Connectors 64
Cleaning Instructions 65
Other Cleaning Hints 77
Warranty Information 79
79Remove all doubt
Product information online 82

1
Getting Started
This chapter introduces the features of the Keysight 81490A
Reference Transmitter Module.
Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Initial Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Line Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Firmware Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Operating Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Storage and Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Environmental Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Laser Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Getting Started with the Reference Transmitter Module. 10
What is a Reference Transmitter Module? . . . . . . . . . . . . . . . . .10
The Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Optical Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
RF Data In. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Setting the Wavelength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Setting the Optical Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Calibrating and Setting the Operating Point . . . . . . . . . . . . . . . . 13

Getting Started Safety Considerations
6Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
Safety Considerations
The following general safety precautions must be observed
during all phases of operation, service, and repair of this
instrument. Failure to comply with these precautions or with
specific warnings elsewhere in this manual violates safety
standards of design, manufacture, and intended use of the
instrument. Keysight Technologies assumes no liability for
the customer’s failure to comply with these requirements.
Before operation, review the instrument and manual,
including the red safety page, for safety markings and
instructions. You must follow these to ensure safe operation
and to maintain the instrument in safe condition.
WARNING The WARNING sign denotes a hazard. It calls attention to a procedure,
practice or the like, which, if not correctly performed or adhered to,
could result in injury or loss of life. Do not proceed beyond a WARNING
sign until the indicated conditions are fully understood and met.
Safety Symbols
The apparatus will be marked with this symbol when it is
necessary for the user to refer to the instruction manual in
order to protect the apparatus against damage.
Hazardous laser radiation.
Initial Inspection Inspect the shipping container for damage. If there is
damage to the container or cushioning, keep them until you
have checked the contents of the shipment for completeness
and verified the instrument both mechanically and
electrically.
The Performance Tests give procedures for checking the
operation of the instrument. If the contents are incomplete,
mechanical damage or defect is apparent, or if an instrument
does not pass the operator’s checks, notify the nearest
Keysight Technologies Sales/Service Office.
WARNING To avoid hazardous electrical shock, do not perform electrical tests
when there are signs of shipping damage to any portion of the outer
enclosure (covers, panels, etc.).

Getting Started Safety Considerations
Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 7
WARNING You MUST return instruments with malfunctioning laser modules to a
Keysight Technologies Service Center for repair and calibration.
Line Power
Requirements
The Keysight 81490A Reference Transmitter Module operates
when installed in the 8163A/B Lightwave Multimeter,
8164A/B Lightwave Measurement System, or
8166A/B Lightwave Multichannel System.
Firmware
Requirements
The Keysight 81490A Reference Transmitter Module can only
operate with more recent versions of the mainframe
firmware.
To find the version of your firmware
1. Press Config.
2. Move to [About Mainframe], and press Enter.
The bottom line shows the firmware revision.
On a 8163A/B Lightwave Multimeter, you should have
firmware V5.01 or greater.
On a 8164A/B Lightwave Measurement System, you should
have firmware V5.01 or greater.
On a 8166A/B Lightwave Multichannel System, you should
have firmware V5.01 or greater.
Operating
Environment
The safety information in the 8163A/B Lightwave Multimeter,
8164A/B Lightwave Measurement System, & 8166A/B
Lightwave Multichannel System User’s Guide summarizes the
operating ranges for the Keysight 81490A Reference
Transmitter Module. In order for these modules to meet
specifications, the operating environment must be within the
limits specified for the mainframe.
Storage and
Shipment
The module can be stored or shipped at temperatures
between 40 C and +70 C. Protect the module from
temperature extremes that may cause condensation within it.

Getting Started Safety Considerations
8Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
Environmental
Information
This product complies with the WEEE Directive
(2002/96/EC) marking requirements. The affixed label
indicates that you must not discard this electrical/ electronic
product in domestic household waste.
Product Category: With reference to the equipment types in
the WEEE Directive Annex I, this product is classed as a
"Monitoring and Control instrumentation" product.
Do not dispose in domestic household waste.
To return unwanted products, contact your local Keysight
office, or see
http://about.keysight.com/en/companyinfo/environment/takeb
ack.shtml
for more information.
Laser Safety
Information
The laser sources specified by this user guide are classified
according to IEC 60825-1 (2007).
The laser sources comply with 21 CFR 1040.10 except for
deviations pursuant to Laser Notice No. 50 dated
2007-June-24.
Table 1 Reference Transmitter Module Safety Information
Keysight 81490A
Laser type CW DFB Laser
with built-in isolator
1310 nm / 1550 nm
<10 mW
9 m
0.1
1M
Wavelength range
Max. CW output power*
Beam waist diameter
Numerical aperture
Laser Class according to
IEC 60825-1 (2007)- International
Max. permissible CW output power ** 52 mW / 163 mW
* Max. CW output power means the highest possible optical CW power that the laser
source can produce at its output.
** Max. permissible CW output power is the highest possible power that is permitted with-
in the appropriate IEC laser class.

Getting Started Safety Considerations
Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 9
Laser Safety Labels
A sheet of laser safety labels is included with the laser
module as required. In order to meet the requirements of
IEC 60825-1 we recommend that you stick the laser safety
labels, in your language, onto a suitable location on the
outside of the instrument where they are clearly visible to
anyone using the instrument.
WARNING Please pay attention to the following laser safety warnings:
• Under no circumstances look into the end of an optical cable attached
to the optical output when the device is operational. The laser
radiation can seriously damage your eyesight.
• Do not enable the laser when there is no fiber attached to the optical
output connector.
• The laser is enabled by pressing the gray button close to the optical
output connector on the front panel of the module. The laser is on
when the green LED on the front panel of the instrument is lit.
• The use of the instruments with this product will increase the hazard
to your eyes.
• The laser module has built-in safety circuitry which will disable the
optical output in the case of a fault condition.
• Refer servicing only to qualified and authorized personnel.

Getting Started Getting Started with the Reference Transmitter Module
10 Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
Getting Started with the Reference Transmitter
Module
What is a Reference
Transmitter Module?
A reference transmitter is an electrical-optical (E/O)
converter, where the data input modulates the output of a
(DFB) laser.
The Keysight 81490A Reference Transmitter Module offers
excellent eye quality as a reference for testing 10 GbE-LR
and 10 GbE-ER, according to IEEE 802.3ae and according to
10 G Fibre Channel specifications.
Offering both 1310 and 1550 nm gives the fastest
reconfiguration between these two transmission bands
without reconnecting.
The separation of the signal source and the modulator is the
only way to offer a zero-chirp modulation. This is essential
for a clean and repeatable eye diagram when modulating
with an appropriate clean external source to fulfill the
requirements of the IEEE standard. Another advantage of
this design, compared with directly modulated transmitters,
is the wide extinction ratio range that can only be achieved
by this architecture. Additionally, the reference transmitter
has a linear transmission behavior. This means that when
used with an electrical arbitrary waveform generator, the
Keysight 81490A Reference Transmitter Module can be used
as an optical arbitrary waveform generator.

Getting Started Getting Started with the Reference Transmitter Module
Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 11
The Front Panel
Figure 1 Front Panel of the Reference Transmitter Module
To insert these modules into your mainframe see your
mainframe’s User’s Guide.
Optical Output Straight Contact Connectors
The Keysight 81490A Reference Transmitter Module are
equipped with a straight contact optical output connector.
Straight contact connectors help you maximise the power
output.
CAUTION Only use cables with straight connectors with the instrument.
Using an angled contact connector can result in losses of 7dB or more.
Figure 2 Straight Contact Connector Symbols
Unlocking the Laser
You have to unlock the laser before you can switch it on.
You can unlock the laser when you first switch the
mainframe by entering the password.
If you need to unlock the laser later,
1. Press Config.
Straight Contact
Connector Symbol
(
with PMF
)

Getting Started Getting Started with the Reference Transmitter Module
12 Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
2. Move to [Unlock], and press Enter.
3. Enter the password, and press Enter.
4. Press Close.
NOTE The default password for the mainframe is “1234”.
Enabling and Disabling the Laser Output
Switch the laser on and off by pressing the Active button on
the front panel of the module.
The State parameter and the Active LED indicate whether
the module is emitting radiation.
If the the laser is active, the State parameter is On and the
Active LED on the front panel of the module is lit.
If the laser is inactive, the State parameter is Off and the
green LED on the front panel of the module is unlit.
RF Data In
CAUTION Do not apply signals to the Data In that exceed -2V and +2V. Within this
range, the signal voltage must be less than 2V peak-to-peak.
The RF input is a 2.4 mm female RF connector. It is AC
coupled. The RF input signal should be less than 1Vpp. This
is the linear area of the E/O converter.
Values outside this range will overdrive the output signal.
If you have applied a signal that overdrives the output
1. Reduce the level of the input.
2. Turn the laser off and back on again.

Getting Started Operation
Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 13
Operation
Setting the
Wavelength
1. On your mainframe, move to the channel of the reference
transmitter module.
2. Move to ], and press Enter.
3. Select the wavelength, and press Enter.
Setting the Optical
Attenuation
1. On your mainframe, move to the channel of the reference
transmitter module.
2. Move to Att] for the wavelength you are using, and press
Enter.
3. Set the attenuation, and press Enter.
Calibrating and
Setting the
Operating Point
For the best possible results, the operating point for the
reference transmitter should be as close as possible to the
center of the modulator’s transfer characteristic. This
ensures you can make the best use of the linear part of the
transfer characteristic.
When you turn the instrument on, a default value is used,
and "Unc" or "Uncal" is shown on the display.
The reference transmitter also checks its temperature
periodically. If the temperature differs too much from the
temperature at which the last recalibration was performed,
this is reflected in the modules status line in the user
interface (“Uncal” for 8164A/B, “Unc” for 8163A/B and
8166A/B).
RF Data In
Optical Output
Modulator
Transfer Characteristic
Operating Point

Getting Started Operation
14 Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
The instrument can set a first approximation to the best
operating point.
1. Press Tx Recal.
To fine tune the operating point
2. Set up your equipment as displayed in Figure 3.
Figure 3 Operating Point Setup
3. On the signal source, set up a “best case” signal.
4. Turn on the laser of the reference transmitter.
5. Set up the optical sampling ’scope to show the “eye”.
The crossing point for the eye should be at 50% ± 1%.
If the crossing point is in this range, you do not need to
adjust the operating point and you can start testing.
Otherwise continue with the following steps.
6. On your mainframe, move to the channel of the reference
transmitter module.
7. For the wavelength you are using, move to [Oper pt.].
OR
aPress Menu.
bMove to [Oper Pt.] for the wavelength you are using, and
press Enter.
8. Set the value for the offset, and press Enter.
You can adjust the operating point from -50 to 50.
9. Refresh the results on the optical sampling ’scope.
If the crossing point is in the range 50% ± 1% (see
Mainframe Optical Sampling ’Scope
Reference
Transmitter
Signal Source

Getting Started Operation
Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 15
Figure 1), you do not need to adjust the operating point
further and you can start testing.
Figure 1 Modulator bias operating point optimized to eye crossing of
50% \1
If the operating point is not optimized (see Figure 2),
return to step 8.
Figure 2 Modulator bias operating point not optimized.

2
Programming Information
This chapter introduces the programming commands
associated with the Keysight 81490A Reference Transmitter
Module.
SCPI Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
New Status Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
New Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Programming Information SCPI Commands
18 Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0
SCPI Commands
NOTE The reference transmitter module occupies two slots. <SlotNr> always
refers to the number of the left slot.
New Status Bit A new status bit (bit 11, value 2048) indicates that the
reference transmitter module needs to be calibrated.
This is set at boot time and also after temperature changes.
The module's status registers can be queried with ...
:STATus<SlotNr>:QUEStionable[:EVENt]?
:STATus<SlotNr>:QUEStionable:CONDition?
NOTE The condition register returns the actual state. That is, the bit is set when
the module detects that it has to be recalibrated and cleared after a
recalibration.
The bit in the event register is also set when the module detects that it has
to be recalibrated. However the bit is not cleared by a recalibration but
when the event register is read.
New Commands Recalibration
command: :SOURce<SlotNr>:TRANsmitter:RECalibration
syntax: :SOURce<SlotNr>:TRANsmitter:RECalibration
description: Recalibrates a reference transmitter module.
The result can be queried using :SYSTem:ERRor?:
It is either ‘+0,”No error”’ or e.g. ‘-200,”Execution error (StatExecError)”’
Recalibration takes about 6.8 seconds, so it also takes this time to get the reply to the
:SYSTem:ERRor? query.
parameters: none
response: none
example: :SOUR1:TRAN:REC

Programming Information SCPI Commands
Keysight 81490A Reference Transmitter Module User’s Guide, Edition 3.0 19
Operating Point
Temperature Check
The reference transmitter checks its temperature periodically.
If the temperature differs too much from the temperature at
which the last recalibration was performed, it sets the
“uncalibrated” status. This is reflected in the modules status
line in the user interface (“Uncal” for 8164A/B, “Unc” for
8163A/B and 8166A/B) and also in the status register (see
“New Status Bit” on page 18).
command: :SOURce<SlotNr>:TRANsmitter:RECalibration?
syntax: :SOURce<SlotNr>:TRANsmitter:RECalibration?
description: Recalibrates a reference transmitter module.
Recalibration takes about 6.8 seconds, so it also takes this time to get the reply to this query.
parameters: none
response: The result is returned as an unquoted string:
“OK” or “ERROR - <error message>”.
example: :SOUR1:TRAN:REC? ÆOK<END>
command: :SOURce<SlotNr>:TRANsmitter:OPOint<laser (1,2)>
syntax: :SOURce<SlotNr>:TRANsmitter:OPOint<laser (1,2)> <data>
description: Sets the operating point for one of the reference transmitter's two laser diodes (see
“Calibrating and Setting the Operating Point” on page 13).
You can also set the minimum, maximum or default value.
parameters: Operating point or MINimum | MAXimum | DEFault.
response: none
example: :sour1:tran:opo1 -17
command: :SOURce<SlotNr>:TRANsmitter:OPOint<laser (1,2)>?
syntax: :SOURce<SlotNr>:TRANsmitter:OPOint<laser (1,2)>?
description: Get the operating point for one of the reference transmitter's two laser diodes (see
“Calibrating and Setting the Operating Point” on page 13).
You can also query the minimum, maximum or default value.
parameters: none | MINimum | MAXimum | DEFault
response: The operating point.
example: :sour1:tran:opo2 Æ-17<END>