Research on Techniques for Light Modulation Detection; Part II: Frequency Demodulators

摘要

The results of a one-year program on the demodulation of frequency-modulated (FM) or phase-modulated (PM) light are presented. Theoretical and experimental studies were made both of direct demodulation and heterodyne demodulation. A technique employing conversion of FM to AM via a birefringent device with subsequent detection by a traveling-wave phototube is used for the demodulation method. The report deals with techniques and devices for converting FM (and PM) to AM at optical frequencies. Comprehensive analyses and discussions are given on two simple birefringent devices, the birefringent discriminator and the optical ratio detector, devices capable of converting FM to AM and PM to AM, respectively. The use of multicrystal devices in demodulators is treated. Included are two optical network synthesis techniques for realizing birefringent devices having arbitrarily specified transfer functions. The conclusions reached in this program are stated, and the major contributions are summarized.