Abstract: A detection method of optical rotation measurement for small angle is proposed by the analysis of output signals. Two kinds of light signals are detected in the experiment. One is detected, after it is sent through the optically active solution and modulated by Faraday coil. The other is just modulated by Faraday coil. By measuring the width of the waveform of these signals, the optical rotation can be obtained. Meanwhile, based on the already built system, sugar solutions with different concentrations are prepared for measurement. The experimental results show that there is a good linear relation between the solution concentration and the optical rotation. The goodness for linear fitting is up to 0. 998. The resolving capability of optical rotation can reach 0.01 degree.

Key words: optical rotation, Faraday magneto-optic effect, small angle measurement