Measurement system for the noise equivalent power of avalanche diode based on virtual instruments

Lock-in amplifier is used to measure the noise voltage of APD (avalanche diode) under a specific operating frequency. And an oscilloscope is utilized to obtain the voltage of the APD optical modulated input. With the aid of an energy meter, the energy of the input modulated light is acquired for the measurement of the NEP (noise equivalent power) of the APD. To eliminate noise interference, some kinds of statistical methods such as the trimmed mean and the relative variance are adopted during the experiment. At the same time, the Labview software plays a vital role in designing the system for automatic test. Final results vividly prove that the designed system has a promising application with the excellent advantages of high measurement accuracy and control precision, good stability and reliability, high automation level and convenient operation.