THORLABS EVOA800F User manual

EVOA800F & EVOA800A
Electronic Variable Optical
Attenuators
User Guide

Electronic Variable Optical Attenuators
TTN116996-D02
Table of Contents
Chapter 1Warning Symbol Definitions.....................................2
Chapter 2Safety ..........................................................................3
Chapter 3Introduction & Quick Start ........................................ 4
3.1.Introduction............................................................4
3.2.Features..................................................................4
3.3.FiberInterface&UtilityPanels................................5
3.4.QuickStartGuide....................................................6
Chapter 4Operating Instructions & Details..............................7
4.1.Overview.................................................................7
4.2.Powering&ChargingtheUnit.................................7
4.3.FiberConnections....................................................8
4.4.WavelengthSelection&Calibration........................8
4.5.AttenuationControl.................................................9
4.6.DigitalOutputPowerDisplay..................................9
4.7.ModulationInput&MonitorOutputConnections....9
4.8.PowerLock............................................................10
Chapter 5Maintenance & Repair .............................................11
Chapter 6Specifications...........................................................12
6.1.GeneralSpecifications...........................................12
6.2.MechanicalDrawings............................................13
Chapter 7Regulatory ................................................................14
Chapter 8Certificate of Compliance .......................................15
Chapter 9Thorlabs Worldwide Contacts................................16

Electronic Variable Optical Attenuators Chapter 1: Warning Symbol Definitions
Page 2 TTN116996-D02
Chapter 1 Warning Symbol Definitions
Below is a list of warning symbols you may encounter in this manual or on
your device.
Symbol Description
Direct Current
Alternating Current
Both Direct and Alternating Current
Earth Ground Terminal
Protective Conductor Terminal
Frame or Chassis Terminal
Equipotentiality
On (Supply)
Off (Supply)
In Position of a Bi-Stable Push Control
Out Position of a Bi-Stable Push Control
Caution: Risk of Electric Shock
Caution: Hot Surface
Caution: Risk of Danger
Warning: Laser Radiation
Caution: Spinning Blades May Cause Harm
Caution: ESD Sensitive Components

Electronic Variable Optical Attenuators Chapter 2: Safety
Rev A, November 14, 2016 Page 3
Chapter 2 Safety
CAUTION
The following statement applies to the products covered in this manual,
unless otherwise specified herein. The statement for other products will
appear in the accompanying documentation. Inputs and outputs must only
be connected with shielded connection cables.
Only with written consent from Thorlabs may changes to single
components be carried out or components not supplied by Thorlabs be
used.
This product has been tested and found to comply with the limits
according to IEC 61326-1 for using connection cables shorter than 3 meters
(9.8 feet).
This equipment has been tested and found to comply with the limits for a
Class B digital device, pursuant to Part 15 of the FCC Rules, and meets all
requirements of the Canadian Interference Causing Equipment Standard
ICES-003 for digital apparatus. These limits are designed to provide
reasonable protection against harmful interference in a residential
installation. This equipment generates, uses, and can radiate radio
frequency energy and, if not installed and used in accordance with the
instructions, may cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a
particular installation.
Thorlabs is not responsible for any radio television interference caused by
modifications of this equipment or the substitution or attachment of
connecting cables and equipment other than those specified by Thorlabs.
The correction of interference caused by such unauthorized modification,
substitution or attachment will be the responsibility of the user. The use of
shielded I/O cables is required when connecting this equipment to any and
all optional peripheral or host devices. Failure to do so may violate FCC
and ICES rules.
The safety of any system incorporating the equipment is the responsibility
of the assembler of the system.
If equipment is used in a manner not specified by the manufacturer, the
protection provided by the equipment may be impaired.
This instrument should be kept clear of environments where liquid spills or
condensing moisture are likely. It is not water resistant. To avoid damage
to the instrument, do not expose it to spray, liquids, or solvents.
The components inside this instrument are ESD sensitive. Take all
appropriate precautions to discharge personnel and equipment before
making any electrical connections to the unit.

Electronic Variable Optical Attenuators Chapter 3: Introduction & Quick Start
Page 4 TTN116996-D02
Figure 1 Front View
Chapter 3 Introduction & Quick Start
3.1. Introduction
The EVOA800F and EVOA800A are electronically controlled variable optical
attenuators (EVOAs) designed for single mode fiber applications. The control
knob allows analog adjustment of the attenuation, while the digital meter
reports the actual output power. A key feature is the Power Lock function,
which allows the user to lock the output power level by using the VOA as a
power stabilizer.
Optical fibers coupled to these EVOAs should be single mode over the
operating range of the EVOA (e.g. 780HP), and either FC/PC connectors
(Item # EVOA800F) or FC/APC connectors (Item # EVOA800A) are accepted.
The wavelength selector switch accesses calibrated settings for 785 nm and
852 nm, and also provides a position which the user can calibrate for any
wavelength from 780 nm to 980 nm.
The unit is battery powered and can last for hundreds of hours on a single
charge. Charging can be done through the utility side panel with either the
included external power supply or a USB mini-B cable (not included). The side
panel also provides an external modulation input and a power monitoring
output via SMA connectors.
3.2. Features
Digital Display
Wavelength
Selector: 785 nm,
852 nm, or Use
r
Bi-Stable Lock
Button
Fiber Bulkhead (2 Places)
2.0 mm Narrow Key
Label Indicates PC o
r
APC Compatibility
Utility
Panel
Power Adjustment
Knob Rocker
Power
Switch

Electronic Variable Optical Attenuators Chapter 3: Introduction & Quick Start
Rev A, November 14, 2016 Page 5
Figure 3 Utility Panel (Side View)
3.3. Fiber Interface & Utility Panels
Rocker Power Switch
2.1 mm Charging Jack
for Included Power
Supply
USB Mini-B
Charging Jack
Charging Indicators
Green: Fully Charged
Yellow: Charging
SMA Modulation
In
p
ut SMA Monitor
Output
User Wavelength
Calibration Pot
Output
Bulkhead
Input
Bulkhead
Connector Label
Figure 2 Fiber Interface Panel (Top View)

Electronic Variable Optical Attenuators Chapter 3: Introduction & Quick Start
Page 6 TTN116996-D02
3.4. Quick Start Guide
ESD CAUTION
The components inside these products are sensitive to electrostatic
discharge (ESD). Take all appropriate precautions, including grounding
personnel and equipment, before making any connections to the unit.
In the box, you should find the EVOA and its power supply with a 2.1 mm
coaxial plug that matches the power input jack on the side of the unit.
Follow these simple instructions to get started as quickly as possible:
1. Make sure the unit is sufficiently charged. It is shipped about 50%
charged. Using the included power supply, it typically takes 5 hours
to reach a full charge (starting from the “Low Battery” indicator) that
lasts for hundreds of hours.
2. Connect input and output fiber patch cables (single mode only)
to the bulkheads. Make sure they are clean. We recommend the
FCC-7020 Fiber Connector Cleaner and the FBC1 Bulkhead Cleaner
for fiber tips and bulkheads, respectively.
3. Select the desired wavelength with the selector knob. The unit is
factory calibrated for both 785 nm and 852 nm. Other wavelengths
in the 780 - 980 nm range can be user calibrated.
4. Turn the rocker power switch ON.
5. Adjust the attenuation to get the desired output power on the
digital display.
6. Press the Lock button to hold the power setting (optional). A
green LED will blink to indicate a successful lock. A red LED will blink
if the unit cannot find a lock.
7. Release the Lock button to make any further adjustments.
NOTE:
The insertion loss when coupling these types of smaller core, single
mode fibers can be well over 1dB at each connection. This is in addition
to the intrinsic insertion loss of the VOA and TAP components inside
the instrument. See Chapter 6 for full specifications.

Electronic Variable Optical Attenuators Chapter 4: Operating Instructions & Details
Rev A, November 14, 2016 Page 7
Chapter 4 Operating Instructions & Details
4.1. Overview
This chapter provides deeper details about the EVOA and its operation. To
get started with using the EVOA, refer instead to the Quick Start Guide
(Section 3.4).
The block diagram below (Figure 4) depicts the unit’s basic architecture. The
EVOA is controlled by analog electronics. The front panel provides a power
adjustment knob, a digital output power display, and Power Lock capability.
Figure 4 Basic Architecture of EVOA
Starting from the left of Figure 4: The light in the input fiber is coupled directly
into a MEMS-based variable optical attenuator (VOA), and the attenuated light
is sampled by a low-percentage tap. The tap output is sent into a photodiode
whose signal is used by the digital output power display, the Power Lock
control loop, and the SMA monitor output. The attenuation value can be
controlled by the manual power adjustment knob, the Power Lock control loop,
or the SMA modulation input.
When the power is switched off, the EVOA defaults to a mid-range attenuation
whose value is independent of the knob position.
4.2. Powering & Charging the Unit
The EVOA is powered by an internal rechargeable Li-ion battery which
provides approximately 300 hours of continuous operation on a full charge.
The battery’s internal circuits prevent full discharge after the Low Battery
indicator appears on the display. To charge the unit, use either the 2.1 mm
coaxial power cord that is included with the EVOA, or use a USB mini-B cable
and charger (not included). If the device continues to be used while the Low
Battery indicator is active, it will eventually be shut down by the battery’s safety
circuits.
The 2.1 mm coaxial power cord will provide 1 A of charging current and hence
the fastest charging time. In contrast, the charging current provided by a USB
cable is up to 500 mA, as determined by the power source. For example, some
Monitor
Output
Output
Fiber
Modulation
Input
Input
Fiber
Manual
Control
Digital
Display
Photodiode
Power Lock
Control Loop
TapVOA

Electronic Variable Optical Attenuators Chapter 4: Operating Instructions & Details
Page 8 TTN116996-D02
USB chargers (e.g., for phones or tablets) will provide a maximum of 500 mA,
while others (e.g., those on a PC) will be as low as 100 mA. All charging rates
are sufficient to power the device while simultaneously charging the battery,
but charging will take longer at lower currents.
Two LEDs on the side utility panel indicate the charging status of the unit. A
yellow LED indicates that charging is in progress, while a green LED indicates
that charging is complete. If both LEDs are lit, there is a battery fault. Please
contact Thorlabs’ tech support ([e-mail]) if this occurs.
When the power is switched on, the attenuation will be set at the value
determined by the position of the manual power adjustment knob. If this value
is not known, we recommend rotating it completely counterclockwise before
switching the power on. This will ensure maximum attenuation.
When the power is switched off, a voltage remains on the internal VOA, such
that there will still be mid-range attenuation even when the power is off. This
is a precautionary feature that uses virtually no current, as the EVOA is an
ultra-low current device. This feature does not drain the battery meaningfully
faster than the battery itself would lose charge otherwise.
4.3. Fiber Connections
The fiber patch cable input and output bulkheads (see Figure 2) are both FC
style. They may be ordered with PC- or APC-style internal connectors:
Item # EVOA800F has FC/PC connectors.
Item # EVOA800A has FC/APC connectors.
The fiber patch cable and connectors should be cleaned whenever a
connection is made. Note that the insertion loss when coupling these types of
smaller core, single mode fibers can be well over 1 dB.
4.4. Wavelength Selection & Calibration
The digital output power display gives the calibrated output power at the
wavelength indicated by the selector knob. The first and second knob
positions are for 785 nm and 852 nm, while the third position (labeled “USER”)
can be calibrated by the user for any wavelength in the 780 - 980 nm operating
range. The user calibration trimpot is located on the side utility panel.
To calibrate the USER position on the knob, the following tools are required:
A single mode laser source at the desired wavelength,
An accurate power meter for that wavelength,
Input and output fiber patch cables, and
A small flathead screwdriver to adjust the trimpot.

Electronic Variable Optical Attenuators Chapter 4: Operating Instructions & Details
Rev A, November 14, 2016 Page 9
Follow these simple steps to calibrate the USER position:
1. Switch the wavelength selector knob to the USER position.
2. Send an optical input into the input bulkhead at the wavelength of
interest. We recommend an input power of a few mW for the best
accuracy.
3. Rotate the manual power adjustment knob completely clockwise to
set it at minimum attenuation.
4. Attach the power meter to the output fiber patch cable. (Make sure
the power meter is set to the correct wavelength.)
5. Adjust the user calibration trimpot so that the power value on the
digital display agrees with the value shown on the power meter.
6. At this point, we recommend making a note of the user wavelength
and placing a piece of tape over the trimpot to prevent accidental
adjustments.
4.5. Attenuation Control
The user can control the attenuation using two analog methods.
The first and simplest method is to rotate the manual power adjustment knob
on the front panel (see Figure 1). This knob provides the full range of
attenuation. Rotating it clockwise increases the output power, while rotating it
counterclockwise decreases the output power. The knob has ten full rotations.
The second method is to apply a voltage to the SMA modulation input on the
side utility panel (see Figure 3). This input allows for modulation from DC to 1
kHz. See Section 4.7, Modulation Input & Monitor Output Connections, for
details.
4.6. Digital Output Power Display
The digital output power display uses the signal from the tap output (see
Section 4.1) to calculate the calibrated output power before the tip, in mW, at
785 nm, 852 nm, or the user wavelength. The display offers 4.5 digits of
resolution (the leftmost digit has a maximum value of 1). The display range
will auto-scale for low or high input power, and changes over at about 15 mW.
The digital display also has a Low Battery warning that indicates when the
battery needs to be charged. The warning appears while there is still sufficient
charge remaining for the Li-ion battery not to degrade.
4.7. Modulation Input & Monitor Output Connections
The side utility panel (see Figure 3) provides two SMA connectors: an input
for analog modulation and an output for power monitoring.

Electronic Variable Optical Attenuators Chapter 4: Operating Instructions & Details
Page 10 TTN116996-D02
The modulation input allows the user to control the attenuation by applying an
AC or DC voltage of up to 4.9 V. AC drive signals of up to 1 kHz can be used
for high-speed modulation of the output power. Note that for the modulation
input to use the full attenuation range of the unit, the manual control knob must
be fully rotated clockwise to the maximum power (minimum attenuation)
setting. This is because the external input simply adds voltage to the internal
VOA (shown in Figure 4), which is biased at almost 0 V at minimum
attenuation.
The monitor output provides a voltage that is proportional to the output power.
The conversion gain is 20 mV/mW, which results in a full-scale voltage of 4 V
for 200 mW of output power. The monitor circuit has a response bandwidth of
1 kHz minimum / 2 kHz typical.
4.8. Power Lock
Power Lock is a unique feature that locks the output power at a user-defined
level. When this mode is active, the EVOA will continuously adjust the
attenuation in order to keep the output power constant as the input power
changes. This is ideal for use in long-term measurements where the optical
power needs to be fixed.
When the Lock button is engaged (see Figure 1), the Power Lock control
circuit will designate the output power on the digital display as the output
power setpoint. This circuit has a maximum bandwidth of 1 Hz.
Note that pushing the button may cause a slight offset in the output power,
which is due to the resolution of the sample-and-hold circuit. If the manual
power adjustment knob is rotated while Power Lock is active, then
disengaging the button will cause the output power to jump to the value
determined by the knob.
The indicator LED next to the Lock button will flash green intermittently when
Power Lock is active and successfully holding the output power constant. If
the EVOA loses the lock, then the indicator light will flash red. This typically
indicates that the input power has changed significantly enough that the
EVOA can no longer successfully compensate.
If this occurs, but then the input power returns to the original range, the control
circuit will reengage the lock and the indicator will flash green. If the lock does
not reestablish, then disengage the Lock button, rotate the manual knob to
the desired output power, and engage the button again.
Power Lock performs best when the input fluctuations are confined to within
reasonable limits. In order for it to maintain the output power at the setpoint
and respond to changes in input power quickly, the input power must always
be greater than the sum of the output power and the EVOA insertion loss. As
a rule of thumb, if the input power is 2X the output power setpoint, the 1%
settling time (i.e., the time until the output power returns to within 1% of the
setpoint) is <0.5 seconds. For smaller ratios, the 1% settling time will increase,
but the power will still stabilize.

Electronic Variable Optical Attenuators Chapter 5: Maintenance & Repair
Rev A, November 14, 2016 Page 11
Chapter 5 Maintenance & Repair
The EVOA should not require regular maintenance. If necessary, the housing
can be cleaned using a soft cloth moistened with a mild glass cleaner. Do not
use chemical solvents or harsh cleaning solutions on the display, and do not
spray cleaning solutions directly onto the unit.
The EVOA does not contain any user-repairable components. If malfunctions
occur, please contact Thorlabs’ technical support
([email protected]). Do not disassemble the unit. There are no user-
serviceable components inside.
The end faces of any fiber patch cables being connected to the EVOA should
be cleaned every time a connection is made. Use, for example, Thorlabs’
FCC-7020 Fiber Connector Cleaner (sold separately). The end faces of the
EVOA’s internal connectors can be easily damaged by dirty fiber ends, and if
damage occurs, the unit will need to be returned to Thorlabs for repair.
The EVOA’s internal connectors can be cleaned using, for example, Thorlabs’
FBC1 Fiber Bulkhead Cleaner (sold separately). The FBC1 allows the internal
connector to be cleaned without removing it from the unit.
Figure 5 FCC-7020 Fiber Connector Cleaner
Figure 6 FBC1 Fiber Bulkhead Cleaner

Electronic Variable Optical Attenuators Chapter 6: Specifications
Page 12 TTN116996-D02
Chapter 6 Specifications
6.1. General Specifications
Item # EVOA800F EVOA800A
Fiber Interfaces 2.0 mm Narrow Key
FC/PC
2.0 mm Narrow Key
FC/APC
Wavelength Range 780 - 980 nm
Input Power 200 mW (Max)
Absolute Maximum: 250 mW
Attenuation
(not including fiber coupling loss)
Minimum: 1 dB (Typ.)
Maximum: >25 dB
Return Loss ≥40 dB
Digital Display Resolution 4.5 Digits, Auto-Ranging
Digital Display Accuracy 5% (Typ.); 10% (Max)
Internal Fiber 780HP
Fiber Coupling Loss 1.0 - 1.5 dB (Typ.) at each Connector
Modulation Input
Input Voltage 0 V to 4.9 V
Absolute Maximum: 5.0 V
Input Impedance High Z
Bandwidth DC to 1 kHz (Typ.)
Connector Female SMA
Monitor Output
Conversion Gain 20 mV/mW
Output Impedance High Z
Bandwidth DC to 1 kHz (Min)
DC to 2 kHz (Typ.)
Connector Female SMA
Battery Specifications
Battery Life 300 h (Typ.) from Full Charge
Battery Charge 3000 mAh
Battery Charging Time 5 h (Typ.) from 2.1 mm Coaxial Barrel Jack
Battery Charging Input Power 5 VDC; Up to 1 A
Battery Charging Connectors 2.1 mm Coaxial Barrel Jack (1 A)
Female USB Mini-B Connector (Up to 500 mA)
Physical Specifications
Dimensions 166.9 mm x 93.2 mm x 55.2 mm
(6.57" x 3.67" x 2.17")
Operating Temperature 10 to 40 °C
Storage Temperature 0 to 50 °C
Relative Humidity 5% to 85% RH (Non-Condensing)

Electronic Variable Optical Attenuators Chapter 6: Specifications
Rev A, November 14, 2016 Page 13
6.2. Mechanical Drawings
3.1 mm
(0.12")
55.2 mm
(2.17")
166.9 mm
(6.57")
161.0 mm
(6.34")
87.0 mm
(3.43")
93.2 mm
(3.67")

Electronic Variable Optical Attenuators Chapter 7: Regulatory
Page 14 TTN116996-D02
Chapter 7 Regulatory
As required by the WEEE (Waste Electrical and Electronic Equipment
Directive) of the European Community and the corresponding national laws,
Thorlabs offers all end users in the EC the possibility to return “end of life”
units without incurring disposal charges.
This offer is valid for Thorlabs electrical and electronic equipment:
Sold after August 13, 2005
Marked correspondingly with the crossed out
“wheelie bin” logo (see right)
Sold to a company or institute within the EC
Currently owned by a company or institute
within the EC
Still complete, not disassembled and not
contaminated
As the WEEE directive applies to self contained
operational electrical and electronic products, this end of
life take back service does not refer to other Thorlabs products, such as:
Pure OEM products, that means assemblies to be built into a unit by
the user (e.g. OEM laser driver cards)
Components
Mechanics and optics
Left over parts of units disassembled by the user (PCB’s, housings
etc.).
If you wish to return a Thorlabs unit for waste recovery, please contact
Thorlabs or your nearest dealer for further information.
Waste Treatment is Your Own Responsibility
If you do not return an “end of life” unit to Thorlabs, you must hand it to a
company specialized in waste recovery. Do not dispose of the unit in a litter
bin or at a public waste disposal site.
Ecological Background
It is well known that WEEE pollutes the environment by releasing toxic
products during decomposition. The aim of the European RoHS directive is to
reduce the content of toxic substances in electronic products in the future.
The intent of the WEEE directive is to enforce the recycling of WEEE. A
controlled recycling of end of life products will thereby avoid negative impacts
on the environment.
Wheelie Bin Logo

Electronic Variable Optical Attenuators Chapter 8: Certificate of Compliance
Rev A, November 14, 2016 Page 15
Chapter 8 Certificate of Compliance

Electronic Variable Optical Attenuators Chapter 9: Thorlabs Worldwide Contacts
Page 16 TTN116996-D02
Chapter 9Thorlabs Worldwide Contacts
For technical support or sales inquiries, please visit us at
www.thorlabs.com/contact for our most up-to-date contact information.
USA, Canada, and South America
Thorlabs, Inc.
sa[email protected]
[email protected]
Europe
Thorlabs GmbH
[email protected]
France
Thorlabs SAS
[email protected]
Japan
Thorlabs Japan, Inc.
[email protected]
UK and Ireland
Thorlabs Ltd.
[email protected]
[email protected]
Scandinavia
Thorlabs Sweden AB
[email protected]
Brazil
Thorlabs Vendas de Fotônicos Ltda.
[email protected]
China
Thorlabs China
[email protected]

www.thorlabs.com