Keysight Technologies 81625B User manual

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User’s Guide
Keysight 81618A/9A
Optical Head Interface Modules
and Keysight 81620B/3B/4B/6B/8B
Optical Heads

Notices
© Keysight Technologies 2018
No part of this manual may be reproduced
in any form or by any means (including
electronic storage and retrieval or transla-
tion into a foreign language) without prior
agreement and written consent from
Keysight Technologies as governed by
United States and international copyright
laws.
Manual Part Number
81623-90B12
Edition
Edition 7.1, December 2018
Printed in Germany
Keysight Technologies Deutschland GmbH
Herrenberger Strasse 130,
71034 Böblingen, Germany
Technology Licenses
The hardware and/or software described in
this document are furnished under a
license and may be used or copied only in
accordance with the terms of such license.
U.S. Government Rights
The Software is “commercial computer
software,” as defined by Federal Acquisition
Regulation (“FAR”) 2.101. Pursuant to FAR
12.212 and 27.405-3 and Department of
Defense FAR Supplement
(“DFARS”) 227.7202, the U.S. government
acquires commercial computer software
under the same terms by which the soft-
ware is customarily provided to the public.
Accordingly, Keysight provides the Soft-
ware to U.S. government customers under
its standard commercial license, which is
embodied in its End User License Agree-
ment (EULA), a copy of which can be found
at http://www.keysight.com/find/sweula.
The license set forth in the EULA represents
the exclusive authority by which the U.S.
government may use, modify, distribute, or
disclose the Software. The EULA and the
license set forth therein, does not require
or permit, among other things, that Key-
sight: (1) Furnish technical information
related to commercial computer software
or commercial computer software docu-
mentation that is not customarily provided
to the public; or (2) Relinquish to, or other-
wise provide, the government rights in
excess of these rights customarily provided
to the public to use, modify, reproduce,
release, perform, display, or disclose com-
mercial computer software or commercial
computer software documentation. No
additional government requirements
beyond those set forth in the EULA shall
apply, except to the extent that those
terms, rights, or licenses are explicitly
required from all providers of commercial
computer software pursuant to the FAR and
the DFARS and are set forth specifically in
writing elsewhere in the EULA. Keysight
shall be under no obligation to update,
revise or otherwise modify the Software.
With respect to any technical data as
defined by FAR 2.101, pursuant to FAR
12.211 and 27.404.2 and DFARS 227.7102,
the U.S. government acquires no greater
than Limited Rights as defined in FAR
27.401 or DFAR 227.7103-5 (c), as appli-
cable in any technical data.
Warranty
THE MATERIAL CONTAINED IN THIS DOCU-
MENT IS PROVIDED "AS IS," AND IS SUB-
JECT TO BEING CHANGED, WITHOUT
NOTICE, IN FUTURE EDITIONS. FURTHER,
TO THE MAXIMUM EXTENT PERMITTED BY
APPLICABLE LAW, KEYSIGHT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR
IMPLIED WITH REGARD TO THIS MANUAL
AND ANY INFORMATION CONTAINED
HEREIN, INCLUDING BUT NOT LIMITED TO
THE IMPLIED WARRANTIES OF MER-
CHANTABILITY AND FITNESS FOR A PAR-
TICULAR PURPOSE. KEYSIGHT SHALL NOT
BE LIABLE FOR ERRORS OR FOR INCIDEN-
TAL OR CONSEQUENTIAL DAMAGES IN
CONNECTION WITH THE FURNISHING,
USE, OR PERFORMANCE OF THIS DOCU-
MENT OR ANY INFORMATION CONTAINED
HEREIN. SHOULD KEYSIGHT AND THE
USER HAVE A SEPARATE WRITTEN AGREE-
MENT WITH WARRANTY TERMS COVER-
ING THE MATERIAL IN THIS DOCUMENT
THAT CONFLICT WITH THESE TERMS, THE
WARRANTY TERMS IN THE SEPARATE
AGREEMENT WILL CONTROL.
Safety Notices
CAUTION
A CAUTION notice denotes a hazard.
It calls attention to an operating pro-
cedure, practice, or the like that, if
not correctly performed or adhered
to, could result in damage to the
product or loss of important data. Do
not proceed beyond a CAUTION
notice until the indicated conditions
are fully understood and met.
WARNING
A WARNING notice denotes a hazard.
It calls attention to an operating pro-
cedure, practice, or the like that, if
not correctly performed or adhered
to, could result in personal injury or
death. Do not proceed beyond a
WARNING notice until the indicated
conditions are fully understood and
met.
2 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 3
Safety Summary
General Safety
Precautions
The following general safety precautions must be observed during all phases of operation
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. For safe operation the general safety precautions for the M9502A
and M9505A AXIe chassis, must be followed.
See: http://www.keysight.com/find/M9505A
Keysight Technologies Inc. assumes no liability for the customer's failure to comply with
these requirements. Before operation, review the instrument and manual for safety
markings and instructions. You must follow these to ensure safe operation and to
maintain the instrument in safe condition.
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.).
General This product is a Safety Class 3 instrument. The protective features of this product may
be impaired if it is used in a manner not specified in the operation instructions.
Environment Conditions This instrument is intended for indoor use in an installation category II, pollution degree 2
environment. It is designed to operate within a temperature range of 0 °C – 40 °C (32 °F –
105 °F) at a maximum relative humidity of 80% and at altitudes of up to 2000 meters.
This 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.
Ground the Instrument To minimize shock hazard, the instrument chassis and cover must be connected to an
electrical protective earth ground. The instrument must be connected to the ac power
mains through a grounded power cable, with the ground wire firmly connected to an
electrical ground (safety ground) at the power outlet. Any interruption of the protective
(grounding) conductor or disconnection of the protective earth terminal will cause a
potential shock hazard that could result in personal injury.
Before Applying Power Verify that all safety precautions are taken including those defined for the mainframe.
The power cable inlet of the instrument serves as a device to disconnect from the mains
in case of hazard. The instrument must be positioned so that the operator can easily
access the power cable inlet. When the instrument is rack mounted the rack must be
provided with an easily accessible mains switch.

4 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
Do Not Operate in an
Explosive Atmosphere
Do not operate the instrument in the presence of flammable gases or fumes.
Do Not Remove the
Instrument Cover
Operating personnel must not remove instrument covers. Component replacement and
internal adjustments must be made only by qualified personnel.
Instruments that appear damaged or defective should be made inoperative and secured
against unintended operation until they can be repaired by qualified service personnel.

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 5
General Safety Considerations
Intended Use
This instrument is intended to use in an office or laboratory environment, under the
environmental conditions listed in the specifications.
Safety Symbols
Instrument Markings
Table 1 Instrument Markings
CAUTION
The caution sign denotes a hazard. It calls attention to a procedure
which, if not correctly performed or adhered to, could result in damage
to or destruction of the product. Do not proceed beyond a caution sign
until the indicated conditions are fully understood and met.
WARNING
The warning sign denotes a hazard. It calls attention to a procedure
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.
Symbol Description
Indicates warning or caution. If you see this symbol on a product, you must refer to the
manuals for specific Warning or Caution information to avoid personal injury or damage
to the product.
The laser radiation symbol. This warning symbol is marked on products which have a
laser output.
The electrostatic discharge symbol. This warning symbol is marked on products which
have components that can be damaged by an electrostatic discharge.

6 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
Indicates the time period during which no hazardous or toxic substance elements are
expected to leak or deteriorate during normal use. Forty years is the expected useful life
of the product.
The C-Tick mark is the certification mark of the Australian
Communications Authority.
The RCM Mark is a compliance mark to the ACMA (Australian Spectrum Management
Agency). This indicates compliance with all Australian EMC regulatory information.
CSA is the Canadian certification mark to demonstrate compliance with the Safety
requirements.
The earthing symbol marks a connection that is connected, through the instrument, to
the earth of the line power.
CE compliance marking to the EU Safety and EMC Directives.
ISM GRP-1A classification according to the international EMC standard.
ICES/NMB-001 compliance marking to the Canadian EMC standard.
This symbol on all primary and secondary packaging indicates compliance to China
standard GB 18455-2001.
Symbol Description

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 7
Compliance and Environmental Information
Table 2 Compliance and Environmental Information
Safety Symbol Description
This product complies with 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 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/takeback.shtml for more
information.

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 9
Contents
Safety Summary 3
General Safety Considerations 5
Compliance and Environmental Information 7
1 Getting Started with Optical Heads
Safety Considerations 14
Safety Symbols 14
Input Power Limitations 15
Initial Inspection 15
Line Power Requirements 15
Operating Environment 16
Storage and Shipment 16
What is an Optical Head? 17
Analog Output 18
Optical input 19
Heat Sink for 81628B optical Head 19
Attaching the heat sink to the 81628B Optical Head 20
Applicable adapters 20
Mounting Instructions 20
Operation 23

10 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
Contents
2 Accessories
Modules and Options 26
Optical Heads (5mm Sensors) 26
High Power Optical Head (with integrating sphere) 27
Connector Adapters - Reference List 28
3 Specifications
Definition of Terms 30
Averaging Time 30
Linearity 30
Linewidth 31
Noise 31
Power range 31
Offset 31
Reference conditions 32
Relative uncertainty due to polarization 32
Relative uncertainty due to speckle noise 33
Relative uncertainty (spectral ripple) due to interference 33
Return loss 34
Spectral width of optical source 34
Total uncertainty 34
Uncertainty at reference conditions 34
Wavelength range 34
Literature 34
Optical Head Specifications 35
Supplementary Performance Characteristics 39
Analog Output 39
Maximum Safe Input Power 40

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 11
Contents
4 Performance Tests
Equipment Required 42
Test Record 44
Test Failure 45
Instrument Specification 46
Functional Tests 47
Performance Tests 48
For 81628B only 48
Accuracy Test 49
Test Setup 50
Linearity Test 52
Noise Test 62
Return Loss Test 62
Relative Uncertainty due to Polarization (Optional Test) 65
Relative Uncertainty due to Interference (Optional Test) 67
Calculation Sheets 85
5 Cleaning Information
Cleaning Instructions for this Device 88
81000xA Optical Head Adapters 88
8162xx Optical Power Heads 88
Safety Precautions 88
Why is it important to clean optical devices? 90
What do I need for proper cleaning? 91
Standard Cleaning Equipment 91
Additional Cleaning Equipment 94
Preserving Connectors 96
Cleaning Instrument Housings 97

12 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
Contents
Which Cleaning Procedure should I use? 98
How to clean connectors 98
How to clean connector adapters 100
How to clean connector interfaces 101
How to clean bare fiber adapters 102
How to clean lenses 103
How to clean instruments with a fixed connector interface 103
How to clean instruments with an optical glass plate 104
How to clean instruments with a physical contact interface 104
How to clean instruments with a recessed lens interface 105
How to clean optical devices which are sensitive to mechanical stress and
pressure 106
How to clean metal filters or attenuator gratings 107
Additional Cleaning Information 108
How to clean bare fiber ends 108
How to clean large area lenses and mirrors 108
Other Cleaning Hints 111

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B
Optical Heads
User’s Guide
1Getting Started with
Optical Heads
This chapter introduces the features of the Keysight 81623B/4B/6B/8B
Optical Heads.
Safety Considerations / 14
What is an Optical Head? / 17
Attaching the heat sink to the 81628B Optical Head / 20
Operation / 23

14 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
1 Getting Started with Optical Heads
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.
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.
Caution - hot surface
Magnetic fields - may interfere with a pacemaker.
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.
CAUTION
A CAUTION notice denotes a hazard. It calls attention to an operating
procedure, practice, or the like that, if not correctly performed or
adhered to, could result in damage to the product or loss of important
data. Do not proceed beyond a CAUTION notice until the indicated
conditions are fully understood and met.

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 15
Getting Started with Optical Heads 1
Input Power Limitations
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.
Line Power Requirements
The Keysight 81618A and Keysight 81619A Optical Head Interface
Modules operate when installed in the 8163B Lightwave Multimeter,
8164B Lightwave Measurement System, and 8166B Lightwave
Multichannel System.
WARNING
Applicable to Keysight 81628B only.
Operation above 34 dBm (2.51 W) is at your own risk.
Operation at a continuous optical power, or an average optical power,
greater than 34 dBm causes, in the specified operating temperature
range, the metal parts (connector adapters, screws) to become hotter
than the required limit (55°C) of the safety standard IEC 61010- 1.
Keysight Technologies Deutschland GmbH will not be liable for any
damage caused by operation above 34 dBm.
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.).

16 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
1 Getting Started with Optical Heads
Operating Environment
The safety information in the Keysight 8163B Lightwave Multimeter,
Keysight 8164B Lightwave Measurement System, and 8166B Lightwave
Multichannel System User’s Guide summarizes the operating ranges for
the Keysight 81618A and Keysight 81619A Optical Head Interface
Modules. In order for these modules to meet specifications, the operating
environment must be within the limits specified for the Keysight 8163B
Lightwave Multimeter, Keysight 8164B Lightwave Measurement System,
and 8166B Lightwave Multichannel System.
Storage and Shipment
This 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.

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 17
Getting Started with Optical Heads 1
What is an Optical Head?
An optical head measures the power emitted from a connected
single-mode or multi-mode fiber or the power applied in an open parallel
beam (with max. 5 mm diameter). The wavelength and power range
depends on the sensor element.
Figure 1 Rear view of an Optical Head with Analog Output
Figure 2 Front View of Optical Head without Adapter
Figure 1 on page -17 and Figure 2 on page -17 show views of a typical
optical head.
Screw to connector
adapter when fitted
Cable to interface
module
Analog output
Optical interface
connector adapter locking screws

18 Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide
1 Getting Started with Optical Heads
Figure 3 on page -18 shows two types of adapter that are available for
connecting the input fiber to an optical head as well as the 81624DD
adapter ring that is used with threaded adapters.
.
Figure 3 Connector adapters
Analog Output
The analog output is the BNC connector on the back of the optical head. It
outputs a voltage directly proportional to the strength of the optical signal
at the optical input in the current range. The analog signal is always in the
range between 0 and 2V, 2V corresponding to a full power input signal in
the current range, 0V corresponding to no input signal.
During autoranging, the level to which 2V corresponds changes. You
should disable autoranging when using the analog output.
D-shape-to-threaded
adapter:
81624DD
D-type magnetic connector
adapter:
(preferred)
81003xx
81001xx
81000BC
Threaded connector
adapter:
81000xA, 81000BT
NOTE
The optical heads are shipped including a mounted 81624DD adapter
ring. To use D-type magnetic connector adapters, this ring should be
removed by loosening the locking screws shown in Figure 2 with a
1.5mm hex key.

Keysight 81618A/9A and Keysight 81620B/3B/4B/6B/8B Optical Heads User’s Guide 19
Getting Started with Optical Heads 1
Disabling Autoranging
Select the best range for the application using the mainframes user
interface. Select <Menu>, <Range Mode>, <Manual> and then choose
from the list of ranges.
Applications
Possible applications for the analog output are:
• to close the feedback loop controlling the current supplied to a laser
• to aid positioning the system for fiber alignment tasks
• to monitor optical power on an oscilloscope
The analog signal reacts instantaneously to the input signal, whereas the
power shown on the display is subject to averaging.
Optical input
The optical input to the optical head requires a connector adapter to
match the connector type (or bare fiber) to the optical head interface.
The optical head interface can be either threaded or a D-type magnetic
interface depending on the model of optical head (81628B is only available
with a threaded interface). See Accessories on page 25 for details of the
connector adapters available.
When a connector adapter is fitted it should be locked in place by
tightening the locking screws located either side of the main optical head
housing.
Heat Sink for 81628B optical Head
The 81628B optical head has a heat sink that allows an extended
operating power range. This heat sink must be mounted on the integrating
sphere for operation from 34 dBm to 38 dBm.