Avalanche photodiode detection system enables X-ray communication up to 10 Mbps

As the core part of the X-ray communication (XCOM) system, the X-ray detector directly affects the data rate and bit error ratio (BER) performance. An avalanche photodiode (APD) with fast response time and high intern gain is chosen as the detector sensor to improve the data rate of XCOM. A three-stage fast preamplifier using radio frequency amplifier chips is designed to amplify the weak signal from the APD sensor. The bit synchronization signal acquisition and signal judgment modules are established to demodulate the detected pulse X-ray signals. The single photon pulse response and signal-to-noise ratio characteristic of the APD detector are tested. The pulse response width is only 25 ns. The BER characteristic with 211,709-bit pseudo-random sequence and the eye diagram of the XCOM system based on the developed APD detector are evaluated. Results show that the BER is zero at the data rate lower than 6 Mbps and reaches 1.98 x 10-4 at 10 Mbps under 55 kV anode voltage, 1.58 A filament current, and a 10 cm air channel. The designed APD detector increases the data rate of XCOM from the level of 1 Mbps to 10 Mbps, indicating its potential application for a higher data rate.