OptoTest OP940-SW User manual

Multichannel
Insertion Loss & Return Loss Meter
OP940-SW
Instruction Manual
www.optotest.com 1.805.987.1700

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Contacting OptoTest Corporation
1.805.987.1700 (7:30 a.m. to 5 p.m. PST)
www.optotest.com
[email protected]
OptoTest Corp.
4750 Calle Quetzal
Camarillo, CA 93012 USA
Notice of Proprietary Rights
The design concepts and engineering details embodied in this manual, which are the
property of OptoTest Corporation, are to be maintained in strict condence. No element
or detail of this manual is to be spuriously used or disclosed without the express written
permission of OptoTest Corporation. All rights are reserved. No part of this publication
may be reproduced, stored in a retrieval system, or transmitted in any form or by any
means, electronic, mechanical, photocopying, recording, or otherwise, without prior
written permission from OptoTest Corporation.
COPYRIGHT © 2018 by OptoTest Corp
ALL RIGHTS RESERVED
PRINTED IN THE UNITED STATES OF AMERICA
MnOP940SW-RevD

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OP940-SW
Table of Contents
Overview 3
Initial Preparation
Unpacking and Inspection 4
Damaged In Shipment 4
Standard Contents 4
Front Panel Connector 5
Warming Up 5
Denition of Specications 6
Nomenclature 10
How to Navigate the User Interface
Mode Select Screen 11
Operation Mode Screens 13
Front Panel Operation
OPM Mode 14
IL Mode 16
RL Mode 17
ILRL Mode 18
Dual ILRL Mode 19
Scan Mode 20
Scan Mode with OP725 23
IL Ref 24
RL Ref 25
Settings Mode 26
Status Mode 29
Multichannel Units 30
Bidirectional Functionality - OP725 32
Examples
1. Referencing and Measuring Return Loss 33
2. Referencing Return Loss with APC Reference Cables 36
3. Referencing and Measuring Insertion Loss 37
4. Referencing Bidirectional IL & RL with an OP725 39
5. OTDR-style trace in Scan Mode 41
Troubleshooting 44
Removing the Source Panel 47
Warranty Information 49

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OP940-SW
Overview
The OP940 is a compact, stand-alone insertion loss and return loss test meter. Using
a pulse-based system for return loss measurements the user is not required to perform
mandrel wraps or use matching gel on the DUT to get quick and accurate insertion loss
and return loss measurements.
The OP940 allows the user to view the IL and RL for up to two wavelengths simultaneously.
The color display coupled with user congurable pass/fail (green/red) settings make it
extremely easy to qualify ber optic patchcords for telecom standards.
Additionally, the unit features an Optical Reectance Scan Mode, On Screen Context
Help, and the ability to measure return loss on both ends of a DUT through the front
panel.
The OP940 uses the USB interface to communicate and be driven by OptoTest software
which further integrates the unit into a highly ecient production line.

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OP940-SW
Initial Preparation
Unpacking and Inspection
The unit was carefully inspected, mechanically, electrically and optically before shipment.
When received, the shipping carton should contain the items listed in Standard Contents.
Account for and inspect each item. In the event of a damaged instrument, write or call
OptoTest Corp, California.
Note: Be aware that accessories such as detector adapters, remote head detectors, and
high performance reference cables will be located inside a small box labeled “Accessories
Inside”. If this box is not included with the original shipment, contact OptoTest of their
nearest distributor.
Please retain the shipping container in case re-shipment is required for any reason.
Damaged In Shipment
All instruments are shipped F.O.B. Camarillo when ordered from OptoTest.
If you receive a damaged instrument you should:
1. Report the damage to your shipper immediately.
2. Inform OptoTest Corporation.
3. Save all shipping cartons.
Failure to follow this procedure may aect your claim for compensation.
Standard Contents
1. Model OP940 IL/RL Test Set
2. Power Cord (U.S. Shipments only)
3. USB A-B cable
4. Certicate of Calibration and if requested the Metrology Report
5. Instruction Manual(s)
6. CD/USB with applicable software and documentation (if ordered)
7. Detector Adapters (if applicable)

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OP940-SW
REMOTE HEAD PORT
IL/RL Test System
OP940
Notice Concerning Front Panel Connector
It is advised by OptoTest that the user connects a short SAVer cable to the front panel.
This cable must be angle polished on both ends and can range from 0.4m in length to
3m in length. The cable should be of reference quality and should stay on the unit even
during down time. One APC end of this cable is connected to the front panel and the
other end is where the reference cable would be connected. The sacrificial cable should
be replaced or repaired when its open connector becomes damaged. This cable and
additional accessories are listed in the care, cleaning and warranty booklet also included
in this shipment.
Keeping the front panel interface clean and contaminant-free is paramount to
good, repeatable insertion loss and return loss measurements, and minimizing the
amount of connections made to the front panel will limit the possibility of scratching or
contaminating the front panel connector.
Warming up the OP940
For the OP940 to reach equilibrium it is advised that the unit be allowed to warm-up
for approximately 15 minutes, so that the lasers and/or LEDs inside the unit can be
acclimated. Simply turning on the unit and allowing it to sit idle will not exercise both
lasers (for SM systems) or both LEDs (for MM systems). When initially turned on only
a single source is on. It is recommended that after the unit is turned on it is placed in
IL mode with the Dual option selected. This will switch the unit between both source
wavelengths allowing both sources to be warmed up concurrently.
The OP940 has a removable panel for the source connector. This will allow the customer
to re-polish the front panel connector if it gets damaged without having to send the unit
back to OptoTest. Please see the instructions included in this manual for removing the
source panel.

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OP940-SW
Definition of Specifications
Dynamic Range
The dynamic range, or measurement range, of the optical power meter spans from
the maximal power level the instrument can measure, without major saturation
to the detector, to the minimal power level where the thermal noise of the detector
becomes greater than the current produced by the incident light. For accurate power
measurements, it is NOT recommended to measure power levels at either end of the
dynamic range. (see Linearity). The dynamic range is measured by comparing the
absolute measured power against a reference power. When the difference between the
two exceeds 1dB either end of the dynamic
range has been reached.
Linearity
Photodetectors are, by nature, very linear over a wide range of optical input powers,
but the power meter electronics can affect the overall system linearity. The power meter
linearity is characterized and specified to know the measurement accuracy and linearity
over the full dynamic range. For accurate insertion loss measurements only power levels
that fall within the range with the best linearity (+/-0.05dB or better) should be measured.
Calibration Wavelength
The calibration wavelengths are the nominal wavelengths of the instruments calibration
points. The exact wavelength of each particular calibration is stated in the certificate of
calibration.
Calibration Traceability
The detector’s absolute calibration data is directly traceable to N.I.S.T. at the specified
calibration wavelength and the specified power level, typically -10dBm.

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OP940-SW
Absolute Accuracy
The absolute accuracy specification includes the total measurement uncertainties
involved in the calibration process including the transfer of the absolute power standard
from N.I.S.T. Contact OptoTest for the detailed chain of uncertainties.
Optical Power Meter, Channel Performance
For multichannel instruments, the power meter circuit converts and digitizes the optical
power level with the given sampling interval. Changes in light levels such as modulation
will be averaged within that sampling interval.
Instrument, Warm up Time
Optical power meters, in general, do not need any warm-up time unless the instrument
has to acclimate to a changing environment. In order to calibrate the instrument or to
perform stable measurements, the instrument should be acclimated for 15 minutes for
each 5ºC of temperature differential. For example if the instrument was stored at 18ºC
and brought into an environment of 28ºC the instrument should be allowed to warm up
for 30 minutes.
Responsivity of InGaAs Detectors Responsivity of Silicon Detectors
Note that other detector types are available such as IN5 (5mm InGaAs) IN10 (10mm InGaAs)
as well as WSR (wide spectral range) and might exhibit a different spectral responsivity.
Definition of Specifications
Spectral Responsivity
Depending on the detector type, InGaAs (Indium Gallium Arsenide) or Silicon, the
spectral responsivity is the efficiency of the detector to convert optical power into
electrical current and it varies with wavelength.

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OP940-SW
Definition of Specifications
Recommended Recalibration Period
This is the recommended time period for re-calibration in order to maintain accurate
specifications. The recommendation is made based upon statistics on detector aging;
however it is up to the metrology policies and procedures within each company to
define the calibration cycles on optical power meters.
Optical Power Meter, Fiber Compatibility
The amount of areal coverage of the detector, or the portion of the light emitted from
the fiber being measured, depends on the mechanical features of the optical interface,
the active area of the detector and the numerical aperture (NA) of the fiber. A fiber
with a large NA, for example 100/140 multimode fiber, might not under-fill a small area
detector hence the absolute power reading will be less than actual.
Return Loss Range
The lower end of the return loss (low return loss = high reflection) defines the level where
the instrument is saturated by large reflections. The higher end of the return loss (high
return loss = very weak reflections) is given by capability of the instrument to amplify and
resolve reflection out of the noise floor.
Return Loss Accuracy
The Return Loss Accuracy is measured using an optical variable attenuator
connected to a >98% reflector. The insertion loss of the attenuator is initially
quantified against a reference optical power meter. The actual attenuation is
then used to calculate the generated reflection, where the resulting reflection
= 2x (variable attenuation + insertion loss of attenuator) + reflector coefficient.
Accuracy of return loss measurements can also be affected by the reference cable and
any excessive losses at the front panel interface.

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OP940-SW
Definition of Specifications
Reference Cable
The reference cable is the cable with which the DUTs will be measured against. Typically
reference cables are required to be of a defined quality with a specified connector/
endface polish.
Instrument, Environmental
Operating Temperature: This is the temperature range in which the instrument will
conform to the specifications after the specified warm up time.
Storage Temperature: This is the temperature range at which the instrument can
be stored with the power off without any damage or any loss of specification to the
instrument. It is required that the instrument be brought back to within the operating
temperature range before it is turned on.
Humidity: The relative non-condensing humidity levels allowed in the operating
temperature range.

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OP940-SW
LCD Color Display
Removeable
Feet
Control Buttons
Home Button Source
Connectors
Remote
Head Port (BNC)
Remote
Head Detector
Removable
Source Panels
REMOTE HEAD PORT
IL/RL Test System
OP940
Power Button
(Keyed)
Nomenclature
Nomenclature

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OP940-SW
Displays the optical power incident on the selected detector
References IL and performs IL measurements
References RL and performs RL measurements at up to two
positions
Page 1
Page 1
User Inter face
How to Navigate the User Interface
At startup, the unit will load the mode which has been selected as the Startup Mode
in the Settings screen. To change mode screens, press the Hbutton and the unit will
transition to the Mode Select screen.
Mode Select Screen
On the Mode Select screen, Buttons 1, 2, and 3will select operation modes for the
unit such as OPM, IL, RL, ILRL, Dual ILRL, Scan, and Settings. Buttons 4and 5
will navigate backward and forward, respectively, through the pages of mode screens.
Pressing the H button on the Mode Select screen will put the unit back into the mode
that it was in most recently.
The Mode Select screen functions as a home screen for the unit. Operators can use
the Mode Select screen as a point of reference for the user interface or if they need to
change Operation Modes.
The unit’s Mode Select screen deploys several modes. Each page has three selections
to choose from and the page number is indicated on the bottom of the screen by the
placement of the wedge as seen in the figure below.
Below is a brief description of the operation modes on each page of the Mode Select
Screen:

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OP940-SW
How to Navigate the User Interface
User Inter face
Page 3Page 2
Allows certain settings—such as pass/fail criteria and
measurement adjustment factors—to be changed and saved on
the unit
Shows current settings and system information
Page 3
Displays Insertion Loss and Return Loss measurements for
one wavelength at a time. Both measurement types can be
referenced from this screen as well
Displays Insertion Loss and Return Loss measurements for
two wavelengths at a time. Both measurement types can be
referenced from this screen as well
Creates OTDR-style scans to help locate large reflections in test
setups. This can be used to diagnose problems encountered
in IL and/or RL measurement including bad connections, fiber
damage, and dirt
Page 2

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OP940-SW
How to Navigate the User Interface
Operation Mode Screens
When the unit is in one of its operation screens, the buttons will operate largely the same.
Buttons 1, 2, 3, and 4 will select options such as reference cycles and wavelength/
channel switching. Button 5will cycle through the pages of these procedures and
options before wrapping back to the first page. Pressing the HButton in an operation
screen will bring the unit back to the Mode Select Screen and pressing it while in a
procedure screen, such as for IL or RL reference, will take the unit back to the root
screen for that operation mode.
User Inter face

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OP940-SW
Front Panel Operation
OPM Mode
This mode controls the optical power meter on the unit, but not the source. OPM mode
supports all the functions of a state-of-the-art optical power meter such as multiple
wavelength calibrations, absolute mode (dBm), and relative mode (dB).
This is a preferred mode for performing measurements using an external optical source.
The indicators below the power reading visually depict the measured power in terms of
the current gain stage of the detector and whether the unit is measuring on the high or
low end of that gain stage.
The unit, by default, operates in “Auto Range” mode meaning that it will find the gain stage
in which it will be able to most accurately measure the optical power.
However, the unit has an option to operate in “Range Hold” mode wherein it will remain in
the same gain stage regardless of the power incident on the detector.
Note: In “Range Hold” one should not be operating at the high or low end of the range.
This will increase the error of the measurement.
OPM Mode

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OP940-SW
Displays on-screen context help for this mode screen
Returns to page 1
Returns to the Home Screen
Front Panel Operation
Page 2
Changes the selected wavelength for the power meter
Switches the display between absolute (dBm) and relative (dB)
measurement modes. The active mode will be in yellow
Performs a measurement of the current optical power and
stores it. The unit will then measure the optical power relative
to the reference power. A loss in power will be displayed as a
negative value
Prevents the unit from changing gain stages on its detector. This
option is good if the user is measuring within a limited range of
optical power as the accuracy will suffer if the power is not within
the optimal limits for that gain stage
Advances to the next page of options
Returns to the Home Screen
Page 1
OPM Mode
Page 1 Page 2

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OP940-SW
Toggles the OP725 between A B and B A directions and
updates the screen to reflect the reference values for the
appropriate direction (only in Bidirectional Mode)
Displays on-screen context help for this mode screen
Returns to page 1
Returns to the Home Screen
Front Panel Operation
IL Mode
IL mode is designed to measure insertion loss for one or two wavelengths at
one time, while allowing the user to toggle between any of the source wavelengths. It
also allows the quick referencing of both wavelengths (for example 1310nm and 1550nm)
and consecutive measuring of insertion loss on components at both wavelengths. IL
measurements will be displayed as positive values. References perfomed in this mode will
carry over to ILRL and Dual ILRL modes.
Page 2
Changes the selected wavelength for Insertion Loss
measurements (only active for Single and FTTX options)
Navigates to the IL Reference screen
Toggles between measuring one wavelength and measuring two
wavelengths at the same time. Single wavelength mode has a
faster update speed
Displays on-screen pass/fail results based on Settings defined by
the user in the Settings mode
Advances to the next page of options
Returns to the Home Screen
Page 1
IL Mode
Page 1 Page 2
A
B
B
A

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OP940-SW
Front Panel Operation
RL Mode
RL mode is designed to measure return loss for two wavelengths at one time. It allows
for quick referencing of two wavelengths and simultaneous measuring of return loss of
reflective events at both wavelengths. Additionally one also has the ability to reference to
and measure return loss of the second connector of the DUT.
RL Mode
Page 1 Page 2
Changes the return loss wavelength-pair for units with more than
two wavelengths
Navigates to the RL Reference screen
Moves to the next reflection position and begins taking
measurements at that point once reference is complete
Displays on-screen pass/fail results based on Settings defined by
the user in the Settings mode
Advances to the next page of options
Returns to the Home Screen
Page 1
Toggles the OP725 between A B and B A directions and
updates the screen to reflect the reference values for the
appropriate direction (only in Bidirectional Mode)
Toggles whether the RL Zero correction is active. The RL Zero
correction is set on the RL Ref screen and will reset to 0.00dB
each time the unit is powered down
Displays on-screen context help for this mode screen
Returns to page 1
Returns to the Home Screen
Page 2
A
B
B
A

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OP940-SW
Front Panel Operation
ILRL Mode
ILRL mode is designed to measure insertion loss and return loss for one wavelength
simultaneously. It allows the quick referencing of both IL and RL and will display
live results for both measurements at one wavelength. IL measurements will be displayed
as positive values.
Changes the selected wavelength for both measurements
Begins the IL Reference procedure
Begins the RL Reference procedure
Displays on-screen pass/fail results based on Settings defined by
the user in the Settings mode
Advances to the next page of options
Returns to the Home Screen
Page 1
ILRL Mode
Page 1 Page 2
Toggles the OP725 between A B and B A directions and
updates the screen to reflect the reference values for the
appropriate direction (only in Bidirectional Mode)
Toggles whether the RL Zero correction is active. The RL Zero
correction is set on the RL Ref screen and will reset to 0dB each
time the unit is powered down
Displays on-screen context help for this mode screen
Returns to page 1
Returns to the Home Screen
Page 2
A
B
B
A

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OP940-SW
Front Panel Operation
Dual ILRL Mode
Dual ILRL mode is designed to measure insertion loss and return loss for two
wavelengths simultaneously. It allows the quick referencing of both IL and RL
and will display live results for both measurements at two wavelengths. IL measurements
will be displayed as positive values.
Dual ILRL Mode
Page 1 Page 2
Changes the selected wavelength for both measurements
(applicable for FTTX systems only)
Navigates to the IL Reference screen
Navigates to the RL Reference screen
Displays on-screen pass/fail results based on Settings
defined by the user in the Settings mode
Advances to the next page of options
Returns to the Home Screen
Page 1
Toggles the OP725 between A B and B A directions and
updates the screen to reflect the reference values for the
appropriate direction (only in Bidirectional Mode)
Toggles whether the RL Zero correction is active. The RL Zero
correction is set on the RL Ref screen and will reset to 0dB
each time the unit is powered down
Displays on-screen context help for this mode screen
Returns to page 1
Returns to the Home Screen
Page 2
A
B
B
A