Electrocircuit design and application in continuous-wave cavity ring-down spectroscopy system

For the convenient application of continuous-wave cavity ring-down spectroscopy (CW-CRDS), a compact measure system based on the DSP technique is presented. The DSP system is capable of signal adjustment, high-speed signal acquisition, and data processing. It is used to replace a test system composed of high-speed A/D card and computer in the traditional CW-CRDS measure system, to obtain and fit the ring-down signal. The fastest acquisition speed of the DSP system can reach 80 MHz with the A/D resolution of 16 bits, thus it can obtain the ring-down signal and determine the ring-down time accurately. Experiments show that the DSP system can achieve the noise-equivalent (RMS) absorption coefficient of about 1.0×10-8 cm-1 in an optical feedback CW-CRDS system, and its repeatability at a sing