Digital Variable Optical Attenuators (DVOAs)

Janis Valdmanis, Ph.D. Optics
Ultrafast Optoelectronics
General Manager

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Features

• PC Controlled and USB Powered
  • Control with GUI Software or Serial Commands
• Two Modes of Operation: Calibrated Attenuation or Manual
• Dark Mode VOA 
• SM Fiber Pigtail Output with FC/APC Connectors
  • Custom Units with FC/PC Connectors Available by Contacting Tech Sales
• Compact Size (4.28" x 1.10" x 2.35")

Thorlabs' DV Series Digital Variable Optical Attenuators (DVOAs) are fully PC-controlled attenuators of the optical power in fiber-optic cables. These digitally controlled instruments are capable of up to >30 dB optical attenuation from 980 to 1250 nm or >25 dB optical attenuation from 1250 to 1650 nm. They feature two operational modes, "Calibrated Attenuation" or "Manual", which provide attenuation control with a resolution down to .01 dB and a fast response time of <0.5 ms. The optical input and output ports are affixed with single-mode optical fiber pigtails and are terminated with FC/APC connectors. Custom units with FC/PC connectors are available upon request, please contact Tech Sales for more info.

The attenuators can both be powered and controlled via USB connection to a PC. A USB-ABL-60 USB 2.0 Type-A to Mini-B Cable with Locking Screw is included with each instrument. A RS-232 serial connection can also be used to send commands to the attenuator. However, if power is not provided by a USB connection to PC, a separate 5 V USB power supply must be used, such as the DS5 Regulated Power Supply.

Dark Mode VOA
When the DVOA is powered off or "disabled" the device operates at "full-dark" or maximum attenuation. Only once the DVOA is "enabled" will it exit maximum "full-dark" attenuation and go to its selected mode and set point.

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The DV Series housing can be mounted to Ø1/2" optical posts with the ECM225 Aluminum Clamp.

Software
The DigitalVOA Application software is a user-friendly GUI, which allows the user to select between the Calibrated Attenuation or Manual modes, set attenuation parameters, and enable or disable the instrument. Please see the Software tab for details and to download the software package. The USB and RS-232 port can both be used to connect to the GUI software. Additionally, the DVOAs can be operated without the software GUI by using SCPI-type serial commands; both the RS-232 and USB ports can be used in this case as well. In order to use the USB interface, the software package must still be installed as it also installs a custom Windows^® USB driver. When both the USB and RS-232 ports are connected, commands can be sent to either port and are executed in the order they arrive (to avoid confusion, it is recommended to send commands to only one port).

Mounting
The DVOAs can be post mounted with the ECM100 or ECM225 aluminum clamps. Multiple DVOAs can be stacked using the EPS225 plastic clamp.

Note: These attenuators are supplied with fiber-optic pigtails for ease of use and easy connector cleaning. The fiber coupling efficiency is highly dependent on connector quality, fiber type, and concentricity. All these parameters, plus the internal loss of the DVOA, contribute to the base insertion loss of the device that will be different for every user application. As a result, the calibrated attenuation is always relative to (or in addition to) the base insertion loss of the device in the user’s setup.

Digital Variable Optical Attenuator Panels

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DVOA Optical Panel
Callout	Description
1	FC/APC Connectors at Fiber Pigtails Narrow Key (2.0 mm) Input
2	FC/APC Connectors at Fiber Pigtails Narrow Key (2.0 mm) Output

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DVOA Electrical Panel
Callout	Description
1	Mini USB "B" with Locking Screw
2	Status LED
3	DB9 Connector (Female)

Software

Version 1.0.0

Click the link below to download the DigitalVOA Application Software.

Software for the DV Series Digital Variable Optical Attenuators

Control with the DigitalVOA Application
The DigitalVOA Application is designed for straightforward use of the DV Series instruments. This software GUI provides full control over the variable optical attenuators, allowing the user to select between the Calibrated Attenuation or Manual modes, set attenuation parameters, and enable or disable the instrument. The software requires a computer running Windows^® 10 or 11 operating systems.

Control via Serial Commands
Serial commands can also be used to control the DVOAs in either the Calibrated Attenuation or Manual modes, set attenuation parameters, receive instrument status, and disable or enable the attenuator. The commands can be sent from a computer running Windows^® 10 or 11 operating systems to the USB or RS-232 ports. Descriptions of each command are included in the manual. Note that the software GUI installer also installs the required driver for USB remote control. The installer is not required for remote control over the RS-232 interface.

DVOA Operation Modes

The images below are examples of the DigitalVOA Application software GUI when used to control the DV Series instrument. The Calibrated and Manual modes are summarized below, please see the manual for additional details. When the DVOA is connected via USB, the GUI will detect the individual instrument's information such as the product name and serial number as shown in the images below. The appropriate GUI is chosen by selecting the COM port associated with the desired DVOA model and serial number upon starting the software. This basic information will not be available when connecting via RS-232 and will be identifiable by COM port only. 

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Calibrated Attenuation: This operation allows the user to request a specific attenuation change, in dB, to be applied to the incoming optical signal. The maximum attenuation is shown on the left side of the scale, while the minimum attenuation is on the right. This mode utilizes the internal calibration points at specific wavelengths, which can be selected using the "Calibrated Wavelength (nm)" box (e.g., 1310, 1550, or 1590 nm). The user should pick the calibrated wavelength that most closely matches the applied wavelength for the best results.

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Manual: This operation allows the user to directly control the operating voltage of the internal VOA within its operational limits and step it manually using the on-screen buttons. The "Monotonic Limit" function will limit the voltage range so the actual attenuation changes monotonically with voltage. Outside the monotonic range, the user can drive the attenuator to discover the exact min or max attenuation voltage (which is slightly different for each unit).