The receiver consists of low-noise programmable-gain pre-amplifier and precision logarithm detectors. The energy of optical beam is converted to an electrical signal using a wide-band PIN photodiode (800 nm – 1800 nm). To improve noise performance and eliminate background radiation effect, each optical beam must be modulated using on-off keying. The receiver also contains a non-linear feedback compensation loop to eliminate DC background current through photodiode. The detector unit contains accurate frequency filters (40 kHz and 60 kHz center frequencies with 5 kHz bandwidths), which can separate two individual optical channels. The separation between channels is better than 80 dB. Due to a logarithm measuring chain, the dynamic range of each channel is equal to 100 dB (50 dB optical). The designed PCBs with potential shielding allow further suppression of surrounding EM noise.

This unique measuring equipment was developed upon the financial support of Czech Grant Agency under grant no. MPO FR-TI4/148 and it is used to 2-D power distribution measurements of optical beams.