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Polarization-Dependent Balanced Detector
Splitting Input for
The INT-POL-1300 is an integrated pair of balanced detectors that are used to analyze the S and P States of Polarization (SOP) of two input signals independently. This compact system is designed for polarization sensitive optical coherence tomography (OCT) applications, but it can be used in any application where the difference between two signals has to be analyzed with high sensitivity.
Functionality of Balanced Receivers
The S and P polarization states of the input are split using polarizing beamsplitters (PBS). The split inputs are directed into two balanced detectors, one for each SOP. These balanced photodetectors operate in the same manner as our PDB400 Series of OCT Balanced Detectors, they subtract the two optical input signals from each other resulting in the cancellation of common mode noise. This allows small changes on the signal path to be extracted from the interfering noise floor for each SOP.
These receivers are comprised of two balanced photodetectors and an ultra-low-noise, high-speed transimpedance amplifier. The advanced design allows an improved matching of the two balanced photodetectors to achieve an excellent common mode rejection, leading to better noise reduction. Furthermore, the balanced detectors have active low-pass filters to prevent aliasing effects and to suppress out of band noise effectively.
Optical signals are coupled to the photodiodes via two FC/APC input connectors. The unit has 6 electrical SMA output connectors 3 per polarization state, i.e. 3 for the S and 3 for the P polarization state. One of these 3 outputs provides the balanced signal and the other two are the power monitor outputs. The monitor outputs enable the control of the input power levels for each detector separately and can be used to adjust the input SOPs for each channel independently. The device is powered via an ±12 V DC input connector.
Packaging and Power Supply
The unit is housed in a rugged, shielded aluminum enclosure. The unit is powered from a ±12 Volts DC power supply which is included.
Thorlabs also offers Fiber-Based Interferometers, which feature an integrated balanced detector.