Compact Balanced Amplified Photodetectors

Features

• InGaAs Balanced Photodetectors with 400 MHz or 2.5 GHz Bandwidth
• Wavelength Range:
  • PDB771C and PDB781CAC: HI1060 Fiber, 980 - 1625 nm
  • PDB770C and PDB780CAC: SMF-28 Ultra, 1260 - 1625 nm
• Surface Mount Component (Solders Directly to PCB)
• Small Footprint: 45.0 mm x 25.0 mm x 7.0 mm
• Evaluation Board with SMA Outputs Available
• FC/APC-Terminated Versions Available from Stock
• Bandwidth, Gain, and Connector Type Customization Options Available; Contact Tech Support for Details

Thorlabs' Compact Balanced Amplified Photodetectors are high-speed InGaAs detectors with a small footprint specifically designed for OEM applications. With a common mode rejection ratio (CMRR) of >20 dB, these detectors are ideal for techniques requiring high sensitivity, such as LIDAR, OCT, and optical frequency domain reflectometry. Detectors operate over the 980 nm to 1625 nm or 1260 nm to 1625 nm wavelength ranges and are available with bandwidths of 400 MHz or 2.5 GHz. Detailed performance specifications can be found by clicking on the blue info icons () in Tables G1.1 and G2.1.

Each detector consists of two well-matched photodiodes and an ultra-low-noise, ultra-low-distortion, high-speed transimpedance amplifier. To act as a balanced receiver, the compact detector subtracts the two optical input signals from each other, which results in the cancellation of common mode noise. This allows small changes in the signal path to be extracted from the interfering noise floor. Each unit also includes two monitor outputs for measuring the individual optical input power levels, as well as low-frequency modulated signals up to 150 kHz. Please see the Operation tab for more details.

Featuring an HI1060 fiber, the PDB771C and PDB781CAC detectors operate over the 980 nm to 1625 nm wavelength range and are optimized for use at 1060 nm. The PDB770C and PDB780CAC compact balanced detectors include an SMF-28 Ultra fiber and are suitable for use in the 1260 nm to 1625 nm wavelength range, with optimized performance at 1310 nm. Each detector module has two fiber leads with Ø900 µm buffer jackets, where one photodiode has a yellow buffer and the second has white for easy identification. The two fibers are 50 cm long and matched in length to <1 mm (with connectors), which ensures the equal optical path lengths needed for common mode noise suppression. Detectors with narrow key FC/APC connectors are available from stock; units with other connector types are available by contacting Tech Support.

Mounting and External Connection
We also offer an evaluation board for mounting and accessing the output signals from these balanced amplified detectors. This board features a pre-defined footprint for soldering the detector in place, SMA connectors for signal output, and connections for a power supply. Included with each PDBEVAL1 board is an RKMF3 connector cable for connecting the Thorlabs LDS12B ±12 VDC Power Supply (not included). Alternatively, each detector's surface mount package can be soldered to a custom PCB; please see the Pin Diagrams tab for more information about the external pin connections. Please refer to the detector's spec sheet for complete instructions on connecting and operating each device.

Please note that the components inside these modules are ESD sensitive. Take all appropriate precautions to discharge personnel and equipment before making any electrical connections to the unit. All soldering must be done by hand; a reflow oven will damage the device.

Packaged Balanced Amplified Photodetectors
Thorlabs also offers balanced amplified photodetectors with fast monitor outputs in shielded aluminum enclosures for out-of-the-box detection solutions. These detectors are available with bandwidths up to 2.5 GHz and have a >20 dB CMRR.

Operation

Thorlabs' Balanced Amplified Photodetectors consists of two well-matched photodiodes and an ultra-low-noise, high-speed transimpedance amplifier (TIA) that generates an output voltage (RF OUTPUT) proportional to the difference between the photocurrents in the two photodiodes (i.e., the two optical input signals). Additionally, each unit has two 150 kHz monitor outputs (MONITOR+ and MONITOR-) to observe the optical input power levels at each photodiode separately. These outputs are low-frequency outputs and cannot be used to measure an RF modulation on the signal.