Abstract:  In order to improve the detection precision and increase the detection distance of the system, a APD
(Avalanche Photo Diode) detection circuit with better performance is designed. Firstly, the technical parameters
of photoelectric detector are analyzed. An avalanche diode with high responsiveness and wide bandwidth is
selected as the front end of the photoelectric conversion circuits. The multilevel amplification circuit with filtering
is designed, in which high precision and fast integrated operational amplification chip CLC425 is used.
Experimental results indicate that the circuit is stable and practicable. And it has the characteristics of fast
response speed, high precision and wide band (100 MHz), which can greatly improve the dynamic precision
and temperature range of Raman temperature system.

Key words: temperature measurement, avalanche photo diode(APD), detection of Raman scattering, fiber optic sensing