Agilent E5574A Users Guide

HP E5574A Optical Loss Analyzer

User’s Guide

Notices

This document contains proprietary information that is protected by copyright. All rights are reserved.

No part of this document may be photocopied, reproduced, or translated to another language without the prior written consent of Hewlett-Packard GmbH.

Subject Matter

The information in this document is subject to change without notice.

Hewlett-Packard makes no warranty of any kind with regard to this printed material, including, but not limited to, the implied warranties of merchantability and ﬁtness for a particular purpose.

Hewlett-Packard shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material.

Printing History

New editions are complete revisions of the guide reﬂecting alterations in the functionality of the instrument. Updates are occasionally made to the guide between editions. The date on the title page changes when an updated guide is published. To ﬁnd out the current revision of the guide, or to purchase an updated guide, contact your Hewlett-Packard representative.

Control Serial Number: First Edition applies directly to all instruments.

Warranty

ThisHewlett-Packardinstrument product is warranted against defects in material and workmanship for a period of one year from date of shipment. During the warranty period, HP will, at its option,eitherrepairorreplace products that prove to be defective.

For warranty service or repair, this product must be returned to a service facility designated by HP. Buyer shall prepay shipping charges to HP and HP shall pay shipping charges to return the product to Buyer. However, Buyer shall pay all shipping charges, duties, and taxes for products returned to HP from another country.

HP warrants that its software and ﬁrmware designated by HP for use with an instrument will execute its programming instructions when properly installed on that instrument. HP does not warrant that the operation of the instrument, software, or ﬁrmwarewill be uninterrupted or error free.

Limitation of Warranty

The foregoing warranty shall not apply to defects resulting from improper or inadequate maintenance by Buyer, Buyer-supplied

software or interfacing, unauthorized modiﬁcation or misuse, operation outside of the environmental speciﬁcations for the product, or improper site preparation or maintenance.

No other warranty is expressed or implied. Hewlett-Packard speciﬁcally disclaims the implied warranties of Merchantability and Fitness for a Particular Purpose.

Exclusive Remedies

The remedies provided herein are Buyer’s sole and exclusive remedies. Hewlett-Packard shall not be liable for any direct, indirect, special, incidental, or consequential damages whether based on contract, tort, or any other legal theory.

Assistance

Productmaintenance agreements and other customer assistance agreements are available for Hewlett-Packard products. For any assistance contact your nearest Hewlett-Packard Sales and Service Ofﬁce.

Certiﬁcation

Hewlett-Packard Company certiﬁes that this product met its published speciﬁcations at the time of shipment from the factory.

Hewlett-Packard 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 Institutes’s calibration facility,and to the calibration facilities of other International Standards Organization members.

ISO 9001 Certiﬁcation

Produced to ISO 9001 international quality system standard as part of our objective of continually increasing customer satisfaction through improved process control.

Third Edition September 1999 E5574-91011 E0999 (First Edition E0895) (Second Edition E1096)

Hewlett-Packard GmbH Herrenberger Str. 130 71034 Böblingen Federal Republic of Germany

HP E5574A Optical Loss Analyzer

User’s Guide

Safety Summary

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. Hewlett-Packard Company assumes no liability for the customer’s failure to comply with these requirements.

General This is a Safety Class 1 instrument (provided with terminal for protective earthing) and has been manufactured and tested according to international safety standards.

Operation – Before applying power Comply with the installation section. Additionally, the following shall be observed:

• Do not remove instrument covers when operating.

• Before the instrument is switched on, all protective earth

terminals, extension cords, auto-transformers and devices connected to it should be connected to a protective earth via a ground socket. Any interruption of the protective earth grounding will cause a potential shock hazard that could result in serious personal injury.

• Whenever it is likely that the protection has been impaired, the

instrument must be made inoperative and be secured against any unintended operation.

• Make sure that only fuses with the required rated currentand of

the speciﬁed type (normal blow, time delay, etc.) are used for replacement. The use of repaired fuses and the short-circuiting of fuseholders must be avoided.

• Adjustments described in the manual are performed with power

supplied to the instrument while protective covers are removed. Be aware that energy at many points may, if contacted,result in personal injury.

• Any adjustments, maintenance, and repair of the opened

instrument under voltageshould be avoidedas much as possible, and when unavoidable, should be carried out only by a skilled person who is aware of the hazard involved. Do not attempt internal service or adjustment unless another person, capable of rendering ﬁrst aid and resuscitation is present. Do not replace components with power cable connected.

Safety Summary

• Do not operate the instrument in the presence of ﬂammable

gases or fumes. Operation of any electrical instrument in such an environment constitutes a deﬁnite safety hazard.

• Do not install substitute parts or perform any unauthorized

modiﬁcation to the instrument.

• Be aware that capacitors inside the instrument may still be

charged even if the instrument has been disconnected from its source of supply.

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, risk of electric shock.

Frame or chassis terminal.

Protective conductor terminal.

Hazardous laser radiation.

Electromagnetic interference (EMI)

WARNING The WARNINGsign 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 The CAUTION sign denotes a hazard. It calls attention to an operating

procedure, practice or the like, which, if not correctly performed or adhered to, could result in damage to or destruction of part or all of the equipment. Do not proceed beyond a CAUTIONsign until the indicated conditions are fully understood and met.

Safety Summary

Initial Safety Information for Laser Source

The speciﬁcations for the laser source are as follows:

E5574A

Laser Type FP-Laser

InGaAsP

Laser Class

According to IEC 825 (Europe) 3A

According to 21 CFR 1040.10

(Canada, Japan, USA)

Output Power (CW) less than 500 µW Beam Waist Diameter 9 µm Numerical Aperture 0.1 Wavelength 1310 ±20nm

1550 ±20nm

NOTE The laser safety warning labels are ﬁxed on the front panel of the instrument.

Safety Summary

A sheet of laser safety warning labels is included with the laser module. You muststick the labels in thelocal language onto the outside of the instrument, in a position where they are clearly visible to anyone using the instrument.

NOTE The Max. Output Power stated on the label located on the rear panel of the

instrument are the maximum allowances for class 1 (USA) and class 3A (non-USA) laser products respectively.

The real output power of the built-in laser source(s) never exceeds 500 µW.

The recommended position for the laser safety warning label is the bottom right corner on the front of the instrument as shown by the arrow in the diagram below.

E5574A

OPTICAL LOSS ANALYZER

Appl 7

Instr

Source On/Off

Syst

Head Input A Head Input B Optical Input Optical Output

Preset Cursor/Vernier

Aux

Help

Enter

•

+/–

MODIFYENTRY

Active

You must return instruments with malfunctioning laser modules to a HP Service Center for repair and calibration, or have the repair and calibration performed on-site by HP personnel.

The laser module has built in safety circuitry that disables the optical output in the case of a fault condition.

WARNING Use of controls or adjustments or performance of procedures other

than those speciﬁed for the laser source may result in hazardous radiation exposure.

WARNING Refer Servicing only to qualiﬁed and authorized personnel.

WARNING Do not enable the laser when there is no ﬁber attached to the optical

output connector. The optical output connector is at the bottom right corner of the

Safety Summary

instrument’s front panel. The laser is enabled bypressing SOURCE ON/OFF. The laser is enabled when the green LED on the front panel of the laser module is lit.

WARNING Under no circumstances look into the end of an optical cable attached

to the optical output when the device is operational. The laser radiation is not visible to the humaneye, but it canseriously damage your eyesight.

There is a safety circuit which monitors the average laser power output, and the power output of each laser pulse. If either the average or the pulse power is greater than the limit for the module, the laser will be disabled.

In This Book

The Structure of this Manual

This manual is divided into four parts:

• General information and guidelines in chapter 1.

• The operating guide, describing how to use the instrument from the front panel, in chapters 2 to 7.

• The programming guide, describing how to operate the instrument remotely via the HP-IB, in chapter 8.

• Additional information not required for routinely day-to-day use in the appendix.

Conventions used in this Manual

• Quoted terms like “Pol. Depend. Loss” are menu items or applications, respectively.

• Small capitals are used to indicate front panel keys, e.g. PRESET.

• Grey text is used to indicate softkeys, e.g. SELECT.

Contents

1 Introducing the HP E5574A Optical Loss Analyzer

1.1 The Components of the OLA 23

1.2 What You Can Do With the OLA 24

Operational Modes 24 The OLA Applications 25

1.3 The OLA Front Panel Keys 26

The Softkeys 27 The MORE Key 27 The Keypad 27 The Cursor Control Keys 28 The Rotary Knob 29

1.4 Operating the OLA 29

1.5 Help is Available 30

1.6 Getting Started 31

Power-On 31 General Instrument Settings 32 Zeroing the Heads 33 Storing the Reference Power 34 Checking the Stability 36

1.7 How to Obtain Exact Results 37

Mechanical Stability 37 Selection of the Optical Heads 37 The Influence of the Output Connector 38

2 Taking Polarization Dependent Measurements

2.1 Measuring Polarization Dependent Loss 41

PDL Measurement Setup 41

Contents

Starting the Measurement 42 Checking the Measurement Conditions 43 Checking the Stability of the Setup 43 Repeating the PDL Measurement 43 Measuring PDL and Insertion Loss Simultaneously 44 Explanation of the Results 44

2.2 Measuring the Polarization Dependent Characteristics of Couplers 46

PD Coupler Test Measurement Setup 46 Starting the Measurement 47 Checking the Measurement Conditions 48 Checking the Stability of the Setup 48 Continuing the Measurement 49 Repeating the Measurement 49 Explanation of the Results 50

3 Taking Standard Loss Measurements

3.1 Measuring the Insertion Loss 55

Insertion Loss Measurement Setup 56 Starting the Measurement 57 Checking the Measurement Conditions 57 Checking the Stability of the Setup 58 Explanation of the Result 58

3.2 Measuring the Return Loss 58

Return Loss Calibration Setup 59 Calibrating for RL Measurements 60 Return Loss Measurement Setup 62 Starting the Measurement 63 Checking the Stability of the Setup 63 Checking the Influence of Polarization 63

Contents

Explanation of the Result 64

4 Testing Optical Couplers

4.1 Measuring Optical Coupler Characteristics 67

Coupler Test Measurement Setup 67 Starting the Measurement 68 Checking the Measurement Conditions 69 Checking the Stability of the Setup 69 Continuing the Coupler Test 70 Measuring the Directivity 71 Explanation of the Results 72

5 Measuring Power

5.1 Measuring Absolute and Relative Power 75

Powermeter Measurement Setup 75 Starting the Measurement 76 Checking the Measurement Conditions 76 Storing a Reference Value 77 Setting the Measurement Mode 78 Measuring the Fluctuation of Optical Power 79 Explanation of the Results 80

6 Using the OLA as a Laser Source and Polarization

Controller

6.1 Using the OLA as a Laser Source 83

Using the Internal Laser 83 Using an External Source 84

6.2 Using the OLA as a Polarization Controller 84

Contents

Sweeping Through all States of Polarization 85 Setting a Reproducible State of Polarization 87

7 Instrument Settings and Software Status

7.1 Checking the General Instrument Settings 91

7.2 Checking the System Configuration 91

7.3 Checking the Software Status 92

8 HP-IB Programming

8.1 Introduction to Programming the OLA 95

The HP Interface Bus 95 Setting the HP-IB Address 96 Modes of Operation 96 OLA Specific Features 97 How the OLA Processes HP-IB commands 98 Some Notes about Programming and Syntax Conventions 99

8.2 Command Summary 101

IEEE Common Commands 101 SCPI Standard STATUS Commands 102 OLA Specific Commands 103

8.3 IEEE Common Commands 107

General Remarks 108 Command Descriptions 109

8.4 Standard STATUS Commands 118

General Remarks 118 Command Descriptions 120

8.5 OLA Specific Commands 125

Contents

8.6 Programming Examples 159

Example 1 - Checking the Communication 159 Example 2 - Reading Power and Storing the Reference 160

A Installation and Maintenance

Safety Considerations 165 Initial Inspection 165 AC Line Power Supply Requirements 166

Line Power Cable 166 Replacing the Fuse 168 Replacing the Battery 169

Environmental Specifications 170

Instrument Positioning and Cooling 171

Optical Output 171 HP-IB Interface 172

Connector 172 HP-IB Logic Levels 173

Claims and Repackaging 174

Return Shipments to HP 174

B Accessories

Instrument and Options 177 HP-IB Cables and Adapters 178 Connector Interfaces and Other Accessories 179

C Specifications

Contents

Definitions of Terms 185 Technical Data, Product Specifications and Characteris-

tics 188

D Performance Test

Required Test Equipment 195 General 196

Setup and Performing the Performance Test 196 Setting the Wavelength 197

Test I. Center Wavelength 198 Test II. Output Power 199 Test III. CW-Stability Short Term 200 Test IV. Linearity and Accuracy 202 Test V. PDL/PDG uncertainty (#020 only) 206 Test VI. Repeatability PDL/PDG 208 Test VII. Noise 210

Absolute PDCR Uncertainty, Repeatability for PDCR 212

Performance Test Form Sheets 213

E Cleaning Procedure

The Cleaning Kit 223 Other Cleaning Tools 225 Preserving Connectors 227 Cleaning Instrument Housings 228

Contents

Cleaning Procedures 228

Cleaning Cable Connectors 228 Cleaning Connector Adapters 230 Cleaning Connector Interfaces 231 Cleaning Bare Fiber Adapters 232 Cleaning Bare Fiber Ends 233 Cleaning Lenses 233 Cleaning Large Area Lenses and Mirrors 234 Cleaning Fixed Connector Interfaces 235 Cleaning Optical Glass Plates 236 Cleaning Physical Contact Interfaces 236 Cleaning Recessed Lens Interfaces 237 Cleaning Fragile Optical Devices 238 Cleaning Metal Filters or Attenuator Gratings 239

F Error Messages

Display Messages 243

Light A?, Light B?, Light A & B? 243 No Head A, No Head B, No Heads 243 P < P par ? 243

HP-IB Messages 244

Instrument Specific Errors 244 Command Errors (-100 to -199) 244 Execution Errors (-200 to -299) 248 Device-Specific Errors (-300 to -399) 249 Query Errors (-400 to -499) 250

Figures

1-1 The OLA Components 23 1-2 The OLA Front Panel 26 1-3 Select Application Display 27 1-4 Example of an Application Display 29 1-5 Preset Display 32 1-6 Setup for Measuring the Reference Power 35 2-1 Setup for PDL Measurements 41 2-2 Polarization Dependent Loss Display 42 2-3 Polarization Dependent Loss / Insertion Loss Display 44 2-4 Setup for PD Coupler Test 46 2-5 Polarization Dependent Coupler Test Display, Page 1 47 2-6 Polarisation Dependent Coupler Test Display, Page 2 49 2-7 Connection Scheme for Optical Couplers 50 3-1 Setup for Insertion Loss Measurements 56 3-2 Insertion Loss Display 57 3-3 Setup for Return Loss Calibration 59 3-4 Return Loss Settings Display 60 3-5 Return Loss Calibration Display 61 3-6 Setup for Return Loss Measurements 62 3-7 Return Loss Display 63 4-1 Setup for Coupler Test 67 4-2 Coupler Test Display, Page 1 68 4-3 Coupler Test Display, Page 2 70 4-4 Coupler Test Directivity Display 71 4-5 Connection Scheme for Optical Couplers 72 5-1 Powermeter Setup 75 5-2 Powermeter Display 76 5-3 Powermeter Settings Display 76 5-4 Powermeter Minimum/Maximum Display 79 6-1 Polarization Controller Rate Settings Display 86 6-2 Polarization Controller Paddle Settings Display 87 7-1 System Configuration Display 91 8-1 Common Status Registers 108 A-1 Line Power Cables – Plug Identification 166 A-2 Rear Panel Markings 168

Figures

A-3 Releasing the Fuse Holder 168 A-4 The Fuse Holder 169 A-5 Correct Positioning of the HP E5574A 171 A-6 The HP-IB Connector 172 D-1 Center Wavelength Test Setup 198 D-2 Output Power Test Setup 199 D-3 CW-Stability Short Term Test Setup 200 D-4 Accuracy Test Setup 202 D-5 Linearity Test Setup 204 D-6 PDL/PDG Uncertainty Test Setup 206 D-7 Example Drawings 207 D-8 Repeatability PDL/PDG Test Setup 208 D-9 Noise Test Setup 210

Tables

8-1 HP-IB Capabilities 96 8-2 EEE Common Commands 101 8-3 SCPI Standard STATUS Commands 102 8-4 Application Independent Commands 103 8-5 PDCT Specific Commands 103 8-6 IL Specific Commands 104 8-7 PDL/IL Specific Commands 104 8-8 Coupler Test Specific Commands 104 8-9 Return Loss Specific Commands 105 8-10 Powermeter Specific Commands 106 8-11 Min/Max Application Specific Commands 107 8-12 Commands, which are Called from all Applications 107

1 Introducing the HP E5574A

Optical Loss Analyzer

Introducing the HP E5574A Optical Loss Analyzer

In this chapter you will ﬁnd basic information about the HP E5574A Optical Loss Analyzer (OLA).

After reading this chapter you will know

• how the instrument works,

• which applications it supports,

• how it is operated.

Introducing the HP E5574A Optical Loss Analyzer

The Components of the OLA

1.1 The Components of the OLA

The HP E5574A Optical Loss Analyzer is a complete solution for the loss/gain characterization of active and passive optical components. The instrument has been optimized to measure the loss of optical ﬁbers and components caused by different states of polarization.

Signal Processing and Display

Head Input AHead Input A Head Input BHead Input B Optical Input Optical OutputHead Input A Head Input B Optical Input Optical Output

Figure 1-1 The OLA Components

Choice of

• 1310 nm

• 1550 nm

• 1310 & 1550 n Fabry-Perot Lase

Internal

Source(s)

Choice of

• 81525A

• 81524A

• 81521B opt 00 Detector Heads

Choice of

• Bare Fiber Pigtail

• Straight Contact Connect

• Angled Contact Connect

Coupler

Pol. Ctrl.

3 dB

• Tunable Laser Sourc or

• White Light Source or

• LED

Introducing the HP E5574A Optical Loss Analyzer

What You Can Do With the OLA

The OLA consists of

• one or two built-in Fabry-Perot laser sources,

• a 3-dB optical coupler for the connection of an external source

and for Return Loss measurements,

• a4-paddle polarization controller for automaticsweep or manual

setting of the polarization,

• an optical output with either a FC/PC terminated ﬁber pigtail, or

a straight contact connector, or an angled contact connector,

• one or two optical heads, chosen to match wavelength and

sensitivity requirements,

• the signal processing and display unit.

1.2 What You Can Do With the OLA

As one can see from Figure 1-1, the OLA has one output and three input ports. It therefore supports a variety of applications.

Operational Modes

You can set-up the OLA to perform as follows:

• It can serve as a highly stable source of linear polarized infra-red

light with a wavelength of 1310 nm and/or 1550 nm.

• It can launch its own or any light from anexternal source to any

optical device under test (DUT).

• It can circulate the optical output through all states of

polarization or establish any desired state of polarization.

• Once the source power has been measured and stored, you can

measure the Insertion Loss of any passive DUT, the output of which is connected to one of the optical heads.

Introducing the HP E5574A Optical Loss Analyzer

What You Can Do With the OLA

• You can measure the optical power of any active optical device

connected to one of the optical heads.

• You can measure two optical powers simultaneously (which is

mandatory for comparing active or passive optical devices and for measuring optical couplers).

• You can measure the polarization dependent characteristics of

the DUT, be that two-port devices or couplers.

• By connecting the sensor head to the optical input, you can

measure the backreﬂection of a DUT, called Return Loss.

The OLA Applications

The OLA applications include the following measurements:

Insertion Loss (IL)

You measure the power loss of passive optical components.

Polarization Dependent Loss (PDL)

You measure the maximal power ﬂuctuation caused by the DUT’s sensitivity to changes in polarization.

Coupler Test

You measure the Coupling Ratio (CR), Splitting Ratio (SR), Insertion Loss (IL), Excess Loss (EL), and Directivity (DIR) of optical couplers.

Polarization Dependent Coupler Test

You measure the Polarization Dependent Coupling Ratio (PDCR), Splitting Ratio (PDSR), Loss (PDL), and Excess Loss (PDEL) of optical couplers.

PDL / Insertion Loss

You measure the Polarization Dependent Loss (PDL) and the averaged Insertion Loss (IL avg) simultaneously.

Introducing the HP E5574A Optical Loss Analyzer

The OLA Front Panel Keys

Return Loss (RL)

You measure the fraction of power which is scattered back to the source by a component.

Powermeter

You measure the absolute or relative power of one or two light sources in dBm or Watts.

1.3 The OLA Front Panel Keys

This paragraph deals with the operation of the OLA using the front panel keys and the rotary knob.

Press APPL to choose the application

E5574A

OPTICAL LOSS ANALYZER

Press MORE to access all options of each application “Source on” indicator

Figure 1-2 The OLA Front Panel

The OLA can also be operated remotely, controlled by a computer using the HP Interface

The front panel shows (from left to right) the power on/off key,four keys below the display, the MORE key, a numerical keypad with additional function keys, four cursor control keys, and the rotary knob.

Bus. See Chapter 8 “HPIB Programming” for details.

Appl 7

Instr

Source On/Off

Syst

Preset Cursor/Vernier

•

Head Input A Head Input B Optical Input Optical Output

Aux

Help

Enter

+/–

MODIFYENTRY

Active

Introducing the HP E5574A Optical Loss Analyzer

The OLA Front Panel Keys

The Softkeys

The four keys below the display are softkeys (software controlled keys). Their meaning changes according to the instrument application you use.

The current function of each softkey is indicated in the corresponding box on the display.

The MORE Key

The key named MORE is used to activate and to display additional softkeys. An application can thus provide more than four softkeys.

After selecting an application, always press MORE to view any additional options provided by the application. Press MORE once again to return to the ﬁrst screen.

The Keypad

The keypad comprises numerical keys as well as named keys. The numerical keys can be used to enter numerical parameters. The named keys can be pressed at any time. They are used as

follows: APPL Use this key to invoke the “Select Application” menu which

shows the list of applications.

Figure 1-3 Select Application Display

Introducing the HP E5574A Optical Loss Analyzer

The OLA Front Panel Keys

With the softkeys, the cursor control keys, or the rotary knob you can choose any application. To start the highlighted application press SELECT or ENTER or APPL once more.

If you have started an application, you can directly access all relevant settings.

These settings apply to all the measurements you take.

INSTR Use this key to invoke the “Select Instrument” menu. You can check or change the settings of the light source, the polarization controller, and the powermeter.

SOURCE ON/OFF Use this key to turn the internal laser light source on or off. The “Source on” indicator lamp shows the current state.

SYST Use this key to invoke the “System Conﬁguration” screen. You can check and change the current HP-IB address of the instrument.

PRESET Use this key to check and to change the general instrument settings for the measurement sensitivity and for the display of measured values.

ATTENTION Pressing this key does not reset the instrument to power-up defaults!

AUX Use this key to display the status of the software presently installed.

HELP Use this key to invoke the built-in help system. ENTER Use this key to conﬁrm the selection of a menu item or to

terminate the manual input of a numerical parameter value.

The Cursor Control Keys

The use of the cursor control keys depends on the application. ↑ / ↓ Use these keys to either move the cursor on the display or to

decrement/increment the highlighted parameter value. → / ← If the upper right-hand corner of the window frame on the

display shows > or <, you use these keys to proceed to a second page or to return to the previous page.

Introducing the HP E5574A Optical Loss Analyzer

Operating the OLA

When changing a numerical parameter, you can use these keys to move the cursor.

The Rotary Knob

The rotary knob performs like ↑ / ↓. It is especially useful if you want to increment or decrement a highlighted parameter value quickly and conveniently.

1.4 Operating the OLA

In general, the OLA is operated by means of the softkeys. Each application comes with its own set of softkeys.

For example:

Figure 1-4 Example of an Application Display

The display shows not only the measured parameters and value(s), but also the current measurement conditions, which can be changed at the touch of a softkey.

If you want to measure the same parametersat head B or atanother optical wavelength, simply press the corresponding softkey below the screen.

However, there are some exceptions to the rule.

Introducing the HP E5574A Optical Loss Analyzer

Help is Available

Please note:

• The application may provide more options than are displayed.

Press MORE to view any additional softkeys available.

• The > in the upper right-hand corner of the window frame

indicates, that a second page exists. Press → to access this page. Press ← to return.

• If you chose a numerical parameter to be changed (by pressing

the appropriate softkey), use the rotary knob, or ↑ / ↓, or the numerical keypad to set its new value.

• The named keys take precedence over the softkeys. If youpress

one of these keys, the current application will be suspended.

ATTENTION The display does not show the general instrument settings. These can only be accessed by pressing the PRESET key!

ATTENTION The display may burn in if itremains unchanged for longer than 24 hours. To avoid damaging the display:

• Change the appearance of the display occasionally.

• Turn off the OLA when it is not in use.

1.5 Help is Available

Whenever you are in doubt, press HELP. You will get information about the current screen. If you need more

information, press SEARCH. You will then see an alphabetical list of related topics. This list

covers the parameters displayed and all related softkeys, including those which are only availableafter pressing MORE. The list usually comprises several pages.

From this list, you can access help to any parameter and/or softkey.

Introducing the HP E5574A Optical Loss Analyzer

Getting Started

1.6 Getting Started

This section is intended to give you general advice. Details can be found in chapters 2 to 7, depending on the application chosen.

Please follow these steps in the given order:

1 Power-on 2 General instrument settings 3 Zeroing the heads 4 Storing the reference power 5 Checking the stability

Power-On

The OLA has been designed to measure even very small changes of optical power.

How to Obtain the Highest Accuracy 1 After switching the instrument on and connecting the optical

head(s), wait one hour before taking measurements.

After this warm-up time, the instrument will deliver measurement results within the speciﬁed measurement accuracy.

Introducing the HP E5574A Optical Loss Analyzer

Getting Started

General Instrument Settings

The general instrument settings for display and sensitivity affect all subsequent measurements.

How to Check the General Instrument Settings 1 Press PRESET to check or change the general instrument settings.

You can change the number of digits to be displayed, the measurement and display mode, and the sensitivity.

Figure 1-5 Preset Display

Number of Digits The standard setting is four digits. It may be

desirable to reduce the number of digits, e.g. if the OLA is used for screening examinations of optical components.

To change the setting press NDIGITS. Mode The measurement and display mode affects all polarization

dependent measurements. The standard setting is “refresh”: The display is updated

continuously. You may change this setting to “average”: The instrument measures

one time interval, calculates the average and then stops. To repeat the measurement, the RESET softkey has to be pressed.

When measuring polarization dependent loss, please note: The PDL value is within the speciﬁed accuracy after the bargraph shown at the bottom of the display is ﬁlled.

Introducing the HP E5574A Optical Loss Analyzer

Getting Started

In refresh mode, this value can change as the measuring window is a sliding window which is updated continuously. However, the accuracy of the PDL value will not improve over time.

In average mode, the measurement will continue and take an average over a second time window. After twice the time the PDL result is displayed and will not change any more. The display will blink during taking of the measurement and the average.

To change the setting press MODE. Optimization of the Head(s) Standard setting is “Low PDL”:

The power range is reduced to -64 dBm, but you get the highest possible polarization sensitivity (0.003 dBpp PDL). This setting is recommended for all polarization dependent measurements. It is only applicable if you use the optical heads HP 81521B opt. 001.

You can change the standard setting to “High sensitivity”: You get the maximal power range (-80 dBm), but less polarization sensitivity (0.012 dBpp PDL typical).

To change the setting press OPTIMIZE. Allow 20 s for switching between these modes.

Though it is not a must, it is recommended that the heads be zeroedonce after the warm-up time. This ensures that the OLA will use the full sensitivity range of the heads.

To return to the last application or menu prior to pressing PRESET, press PREVIOUS.

Zeroing the Heads

Loss measurements are relative measurements, comparing the optical power transmitted to the device under test (DUT) with the power returned from the DUT.

Zeroing the heads is only necessary, if you wish to use the OLA to measure the absolute output power of optical devices. Zeroing is only required once after warm-up.

Introducing the HP E5574A Optical Loss Analyzer

Getting Started

How to Zero the Heads 1 Shield the optical head(s) from light.

Do one of the following:

• Screw the protection caps onto the heads.

• Interrupt the signal path (e. g. by turning the source off). 2 Press APPL and activate “Powermeter”. 3 Press MORE to view the ZERO softkey.

Most of the OLA applications provide the

ZERO softkey.

4 Press ZERO.

If there are two heads connected, both heads will be zeroed. The message “Light A” or “Light B”will be displayed, if one of the heads is still sensing a signal. In this case, zeroing is not possible. You can either disconnect the second head or repeat step one.

5 Wait some seconds until a power value is shown again. 6 Press APPL to terminate the “Powermeter” application.

After zeroing, the instrument is ready to measure absolute power values.

Note that the power range is independent of the source wavelength. Even if you change the wavelength, there is no need to zero the heads once again.

Storing the Reference Power

In order to measure the optical power loss of a device, you must ﬁrst measure and store the power transmitted to the device. As long as you use one of the internal light sources and the same setup, this is required only once after warm-up (unless the room temperature changes drastically).

Introducing the HP E5574A Optical Loss Analyzer

Getting Started

How to Measure the Reference Power

Internal

Signal Processing and Display

Head Input A Head Input B Optical Input Optical OutputHead Input A Head Input B Optical Input Optical Output

Source(s)

Figure 1-6 Setup for Measuring the Reference Power

1 Connect the optical output to the optical head you wish to use.

Include all connectors and connector adaptors you are going to use for connection of your device under test.

2 Activate the optical output.

If you decide to use the internal light source, press SOURCE ON/ OFF to turn the source on. Watch the source indicator lamp.

If you have connected an external light source to the optical input, press SOURCE ON/OFF to turn the internal source off.

Coupler

Pol. Ctrl.

3 dB

WARNING After connecting an external source to the optical input, light

(eventuallylaser light) will emerge from the optical output even though thesourceindicator lamp isoff! This happens evenwhen the OLA is not connected to the mains or is switched off!

Introducing the HP E5574A Optical Loss Analyzer

Getting Started

3 Press APPL and activate “Powermeter”. 4 Check the “Head” parameter on the display. 5 Press HEAD A or HEAD B, respectively, to activate the head to

which you have connected the optical output.

6 Check the power output value on the display. For the internal

source it should be around –7.5 dBm.

All of the OLA applications for loss measurements provide the

DISP–>REF softkey.

7 Press DISP–>REF. 8 Press APPL to terminate the “Powermeter” application.

After storing the reference power, the instrument is ready to measure power loss.

ATTENTION If you change the interface adaptors orthe source, you must measure and store the reference power anew.

Checking the Stability

Mechanical and electrical stability are vital issues in the measurement of optical characteristics.

After warm-up, the electrical stability of the OLA reaches or surpasses the values stated in its Technical Data sheet.

The mechanical stability depends on your setup. After the ﬁrst setup and after any change it is advisable to check the

stability.Most of the OLA applications offer the STABILITY softkey.

How to Check the Stability 1 Press STABILITY to measure the variation of the optical power

received by the head(s). The instrument uses a sliding time window of 5 s and displays

the difference between the highest and lowest power value

Introducing the HP E5574A Optical Loss Analyzer

How to Obtain Exact Results

measured within that time. The display is automatically updated.

2 Observe the stability value.

If you leave your set-up untouched, it will reach a minimum.

You can decide whether the stability value supports your requirements or not. For example: If you are measuring a signal of

0.1 dB and only 10 % accuracy is required, astability value of 0.01 dB may sufﬁce.

However, in most cases a stability value below 0.002 dB can be achieved in a few seconds.

1.7 How to Obtain Exact Results

The accuracy and reproducibility of the measured results depend largely on your setup. It must be mechanically stable and you must attach adequate heads and connectors.

Mechanical Stability

The signal variations caused by polarization are usually rather small. Vibrations or movement of the optical cables will cause relatively large measurement errors.

The use of an optical workbench is therefore recommended. You should use adhesive tape or clamps to attach as much of the optical cables to the bench as possible.

Selection of the Optical Heads

See the HP E5574A Technical Data sheet for information on the optical heads.

Optical head HP 81521B opt. 001 is recommended for all polarization dependent measurements. It is the only head which has

Introducing the HP E5574A Optical Loss Analyzer

How to Obtain Exact Results

a speciﬁed polarization sensitivity of 0.003 dBpp for the measurement of polarization dependent power variations.

If you are using the optical heads HP 81524A or HP 81525A, respectively, please note that these heads are not suitable for polarization dependent measurements.

The Inﬂuence of the Output Connector

The ﬁber pigtail optical output provides polarization dependent loss measurements with the highest accuracy.

If your instrument is equipped with the straight or angled connector option, please remember:

Due to their construction, angled contact connectors usually exhibit a higher polarization dependent loss than straight contact connectors.

• Every connector or patchcord may induce measurement errors

caused by polarization dependent loss of the connector or patchcord itself.

• It is important that you use high precision connectors with

excellent physical glass-to-glass contact. Even the slightest gap within a connector pair will result in variable reﬂections, which can cause high errors and which may affect the laser source, too.

• Every connector between the source, the device under test, and

the optical head reduces the overall sensitivity.

2 Taking Polarization

Dependent Measurements

Taking Polarization Dependent Measurements

This chapter provides information on how to measure the loss of an optical component or the changes of the characteristics of an optical coupler caused by different states of polarization.

When you start one of the applications

• Pol. Depend. Loss,

• PD Coupler Test,

• PDL / Insert. Loss,

the built-in polarization controller begins to sweep. The light emerging from the optical output will pass through all states of polarization.

What you measure is basically the difference between the highest and lowest intensity caused by the continuously changing polarization and received by the optical head(s). The OLA uses a recursive algorithm which checks the PDL value and changes the measurement window (that is, the number of samples to be taken) so that the speciﬁed accuracy is achieved. The larger the PDL value is, the longer the measurement takes.

This chapter is divided into two sections:

• The measurement of the Polarization Dependent Loss of passive

optical components.

• The measurement of the polarization dependent characteristics

of optical couplers.

Taking Polarization Dependent Measurements

Measuring Polarization Dependent Loss

2.1 Measuring Polarization Dependent Loss

This section covers the use of the applications “Pol. Depend. Loss” and “PDL / Insert. Loss”. You can measure how the optical loss of passive components is affected by different states of polarization.

PDL Measurement Setup

Signal Processing and Display

Head Input A Head Input B Optical Input Optical OutputHead Input A Head Input B Optical Input Optical Output

Figure 2-1 Setup for PDL Measurements

The same setup can be used to measure the Insertion Loss.

1 Connect the optical output to the input of the device under test

(DUT).

2 Connect the optical head to the output of the DUT.

Internal

Source(s)

Coupler

3 dB

Device

under

Test

Pol. Ctrl.

Taking Polarization Dependent Measurements

Measuring Polarization Dependent Loss

3 Activate the optical output.

If you use the internal light source, press SOURCE ON/OFF to turn the source on. The source indicator lamp must be lit.

If you have connected an external light source to the optical input, press SOURCE ON/OFF to turn the internal source off. The source indicator lamp must be off.

Starting the Measurement

1 Press APPL to activate the “Select Applications” menu. 2 Choose “Pol. Depend. Loss”. 3 Wait until the result is displayed.

The OLA immediately starts to measure. Depending on the PDL value, the instrument automatically chooses the right amount of samples to achieve the speciﬁed accuracy. The bargraph at the bottom of the display shows the measurement in progress. The larger the PDL value of the DUT is, the longer the measurement takes.

Figure 2-2 Polarization Dependent Loss Display

Taking Polarization Dependent Measurements

Measuring Polarization Dependent Loss

Checking the Measurement Conditions

1 If not already done, check the general instrument settings by

pressing PRESET. For highest resolution, the “Number of Digits” should read

0.1234 and “Low PDL” should be set. The “Mode” will affect the measuring method (see section 1.6 “Getting Started” on page 31). Press PREVIOUS to return to PDL.

2 Check the “Head” parameter on the display. If it does not show

the head to which you connected the DUT, press HEAD A or

HEAD B respectively.

Before you record the ﬁrst PDL value on your test protocol, it is important to check the stability of your setup.

Checking the Stability of the Setup

1 Press MORE. 2 Press STABILITY. 3 Check the stability value. Refer to page 31 in section 1.6

“Getting Started” for information on the stability value.

4 Press PREVIOUS to return to the previous page and read the PDL.

Repeating the PDL Measurement

If the display is not updated continuously, because you are in average mode, you must restart the PDL measurement manually.

1 Press RESTART.

Taking Polarization Dependent Measurements

Measuring Polarization Dependent Loss

Measuring PDL and Insertion Loss Simultaneously

ATTENTION Before you measure Insertion Loss, you must at

least measure and store the reference power P ref. If you have not yet stored the reference power, refer to page 31 in section 1.6 “Getting Started”.

1 Press APPL to activate the “Select Applications” menu. 2 Choose “PDL / Ins. Loss”.

The instrument immediately starts to measure. Wait until the values are displayed.

Figure 2-3 Polarization Dependent Loss / Insertion Loss Display

Explanation of the Results

The values are calculated according to the following formulas:

Polarization Dependent Loss

PDL 10

(dB) 10

PDL

A/B

For most components (except polarizers) the PDL is much smaller than the Insertion Loss.

----------- -log⋅= P

max min

max

A/B

------------------------log⋅=

min

A/B

Taking Polarization Dependent Measurements

Measuring Polarization Dependent Loss

Averaged Insertion Loss

The Insertion Loss is deﬁned as

A/B

(dB) 10–

A/B

------------- -log⋅= P ref

You will notice a difference in readings for the insertion lossvalues measured with the applications “Insertion Loss” or “PDL / Ins. Loss” respectively.

The reason is that the average insertion loss measured with “PDL / Ins. Loss” represents a PDL independent insertion loss value.

A/B

avg

---------------------------------------------------------=

A/B

max IL

A/B

min+

The value for Averaged Insertion Loss is the same as if measured with an unpolarized source such as an LED.

Taking Polarization Dependent Measurements

Measuring the Polarization Dependent Characteristics of Couplers

2.2 Measuring the Polarization Dependent Characteristics of Couplers

This section covers the use of the application “PD Coupler Test”. You can measure how the Coupling Ratio, the Splitting Ratio and other parameters change with polarization.

PD Coupler Test Measurement Setup

Two optical heads are required to measure the properties of optical couplers.

Signal Processing and Display

Head Input A Head Input B Optical Input Optical OutputHead Input A

Head Input B Optical Input Optical Output

Head B

Head A

Figure 2-4 Setup for PD Coupler Test

Internal

Source(s)

Coupler

3 dB

Coupler

under

Test

Pol. Ctrl.

InOut

Taking Polarization Dependent Measurements

Measuring the Polarization Dependent Characteristics of Couplers

The same setup can be used for the standard coupler test.

1 Connect the optical output to input no. 1 of the device under test

(DUT).

2 Connect optical head A to output no. 1 of the DUT. 3 Connect optical head B to output no. 2 of the DUT. 4 Activate the optical output.

If you use the internal light source, press SOURCE ON/OFF to turn the source on. The source indicator lamp must be lit.

If you have connected an external light source to the optical input, press SOURCE ON/OFF to turn the internal source off. The source indicator lamp must be off.