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Electronic Variable Optical Attenuators (EVOAs), Fiber Coupled, with Power Lock


  • Manual and Electronic Control of Optical Power in Fiber
  • Modulation Input and Monitor Output with 1 kHz Bandwidth
  • Power Lock Mode Stabilizes Output for Long-Term Measurements
  • Two Wavelength Range Options

Electronic VOA Block Diagram

EVOA1550F 

1250 to 1625 nm,
 FC/PC Version 

Related Items


Please Wait
Power Lock On
Click for Details

When Power Lock is active, the indicator LED next to the lock button blinks green.
EVOA Quick Links
Item # Wavelength Range Connector
EVOA800A 780 - 980 nm FC/APC
EVOA800F FC/PC
EVOA1550A 1250 - 1625 nm FC/APC
EVOA1550F FC/PC

Features

  • Wavelength Range Options:
    • 780 nm to 980 nm
    • 1250 nm to 1625 nm 
  • Maximum Attenuation Greater than 25 dB Using MEMS-Based Approach 
  • Input Power up to 200 mW
  • In-Line Fiber Optic Power Monitor with Calibrated Reading Displayed
  • Power Lock Mode Stabilizes Output When Desired
  • Li-Ion Rechargeable Battery with 300 hour Lifetime from Full Charge

Thorlabs' Electronic Variable Optical Attenuators (EVOAs) offer in-line tabletop control of the optical power in a single mode optical fiber, including the ability to lock the optical output power at a user-defined level. These EVOAs provide attenuation of up to at least 25 dB, which can be continuously tuned using either a rotary knob or an external control voltage applied via an SMA connector (maximum frequency of 1 kHz). To attenuate the light, an internal MEMS mirror adjusts the coupling ratio between the input and output fibers. The output power is displayed on the front in mW.

The displayed output power is calculated from the signal read from a low-percentage internal optical tap and wavelength-specific calibration settings. The wavelength selector knob, shown in the photo to the right, is used to choose among one user-calibrated and two factory-calibrated settings. The factory-calibrated settings correspond to 785 nm and 852 nm for the EVOA800 models and 1310 nm and 1550 nm for the EVOA1550 models. The user can also calibrate for any wavelength within the operating range of the EVOA by using a single mode laser, an accurate power meter, and the trimpot on the side utility panel, shown in the photo below. The procedure is described in Section 4.4 of the manuals for the EVOA800 models and EVOA1550 models, and the user's custom calibration setting is accessed by turning the wavelength selector knob to USER.

These EVOAs are designed for use with optical fiber that is single mode within the operating range of the EVOA, and either FC/APC or FC/PC connectors are accepted. An example of single mode optical fiber that may be used with the EVOA800 models is 780HP, while SMF-28 is an option for the EVOA1550 models. For ease of operation, our EVOAs are powered by a Li-ion battery that typically lasts up to 300 hours from a full charge. This battery can be recharged using a USB mini-B connector or the included 5 V power adapter.

Power Lock
Unique to Thorlabs' EVOAs, Power Lock provides automated stabilization of the optical output power. Simply adjust the EVOA to the desired power level and engage the Lock button. This mode has a 1% settling time of <0.5 seconds, making it ideal for correcting slow drifts that occur over long-term measurements. For additional details, please see the Power Lock tab above.

Top of EVOA
Click to Enlarge

The top of the EVOA contains two bulkheads for FC/PC or FC/APC connectors and a label indicating the connector interface. Four rubber feet prevent the EVOA from sliding when it is lying on a surface.
Side of EVOA
Click to Enlarge

The side of the EVOA provides USB mini-B and power adapter connectors for recharging, two SMA connectors for modulation input and monitor output, and a trimpot for power calibration at user-selected wavelengths.
EVOA Block Diagram
Click to Enlarge

EVOA Block Diagram

EVOA Mechanical Drawing
Mechanical Drawing
Item # EVOA800A EVOA800F EVOA1550A EVOA1550F
Wavelength Range 780 to 980 nm 1250 to 1625 nm
Fiber Interfacesa FC/APC FC/PC FC/APC FC/PC
Input Power 200 mW (Max)
Absolute Maximum: 250 mW
Attenuationb Minimum: 1 dB (Typ.)
Maximum: >25 dB
Return Loss ≥40 dB
Fiber Coupling Loss 1.0 to 1.5 dB at Each Connector (Typ.) 0.3 dB at Each Connector (Typ.)
Digital Display Resolution 4.5 Digits, Auto-Ranging
(Leftmost Digit has a Maximum Value of 1)
Digital Display Accuracy 5% (Typ.)
10% (Max)
Calibration Set Points 785 nm, 852 nm, and User-Defined 1310 nm, 1550 nm, and User-Defined
Internal Fiber 780HP SMF-28
  • 2.0 mm Narrow Key
  • Not Including Fiber Coupling Loss
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.)a
Connector Female SMA
  • The modulation input accepts sine waves, square waves, and other shapes, but it will not respond to frequency components greater than 1 kHz.
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 6.57" x 3.67" x 2.17"
(166.9 mm x 93.2 mm x 55.2 mm)
Operating Temperature 10 to 40 °C
Storage Temperature 0 to 50 °C
Relative Humidity 5% to 85% RH (Non-Condensing)
Power Lock Off
Click for Details

If Power Lock cannot stabilize the input power at the designated setpoint, the indicator LED blinks red.
Power Lock On
Click for Details

When Power Lock is active, the indicator LED next to the lock button blinks green.

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, 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.

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. The green and red LEDs are shown in the images to the right.

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 at least 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, as shown by the plots below. For smaller ratios, the 1% settling time will increase, but the power will still stabilize.

Performance Graphs

Positive Steps
Click to Enlarge

The graph above shows the qualitative behavior of the Power Lock 1% settling time. Power Lock provides fast 1% settling times as long as the input power/output power ratio is at least 2X. As the input power approaches the sum of the output power and the EVOA insertion loss, the settling time will increase, but the power will still stabilize. The asymptote at 1.2X shown above will vary from device to device and is set by the minimum insertion loss (1 dB typical ≈ 20%).
Positive Steps
Click to Enlarge

The 1% settling time for an increase in input power is generally short. (This plot contains experimentally measured data, and the output power setpoint was 1 mW.)
Negative Step
Click to Enlarge

When the input power suddenly drops by a large amount, the 1% settling time increases, but the power still stabilizes. (This plot contains experimentally measured data, and the output power setpoint was 1 mW.)

Modulation Input

SMA Female

SMA-female

Input Voltage: 0 V to 4.9 V
Input Impedance: High Z
Bandwidth: DC to 1 kHz (Typ.)

Monitor Output

SMA Female

SMA-female

Conversion Gain: 20 mV/mW
Output Impedance: High Z
Bandwidth: DC to 1 kHz (Min); DC to 2 kHz (Typ.)

Charging

USB Mini-B Female

USB Mini-B

Voltage: 5 VDC
Current: Up to 500 mA; Determined by
Power Source

Charging

2.1 mm Coaxial Barrel Jack

SMA-female

Voltage: 5 VDC
Current: 1 A


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780 to 980 nm Wavelength Range

  • In-Line Fiber Optic Power Monitor for 785 nm, 852 nm, or User-Calibrated Wavelength
  • Maximum Attenuation of >25 dB
  • Input Power up to 200 mW
  • FC/APC and FC/PC Versions Available

These EVOAs are designed for use with optical fiber that is single mode within the operating range of the EVOA. An example of single mode optical fiber that may be used with the EVOA800 models is 780HP.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
EVOA800A Support Documentation
EVOA800AElectronic Variable Optical Attenuator with Power Lock, FC/APC, 780 to 980 nm
$1,994.00
Today
EVOA800F Support Documentation
EVOA800FElectronic Variable Optical Attenuator with Power Lock, FC/PC, 780 to 980 nm
$1,994.00
Today

1250 to 1625 nm Wavelength Range

  • In-Line Fiber Optic Power Monitor for 1310 nm, 1550 nm, or User-Calibrated Wavelength
  • Maximum Attenuation of >25 dB
  • Input Power up to 200 mW
  • FC/APC and FC/PC Versions Available

These EVOAs are designed for use with optical fiber that is single mode within the operating range of the EVOA. An example of single mode optical fiber that may be used with the EVOA1550 models is SMF-28.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
EVOA1550A Support Documentation
EVOA1550AElectronic Variable Optical Attenuator with Power Lock, FC/APC, 1250 to 1625 nm
$1,892.00
Today
EVOA1550F Support Documentation
EVOA1550FElectronic Variable Optical Attenuator with Power Lock, FC/PC, 1250 to 1625 nm
$1,892.00
Today
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