Abstract: The AM/FM converter of the present invention comprises an optical frequency modulation section which receives multi-channel AM video signals and outputs an optical-frequency-modulated optical signal beam; and an optical heterodyne detection section comprising an optical frequency oscillator composed of a semiconductor local laser which outputs a local oscillator optical beam having an optical frequency separated by a designated intermediate frequency, an optical coupler, and a photoelectric converter composed of a photodiode, which receives the optical signal beam and outputs an electrical batched FM modulation signal which is frequency-modulated and frequency-converted to the intermediate frequency. By means of this configuration, the invention offers an AM/FM converter wherein the frequency band is made considerably wider.

Abstract: A system for a Mach-Zender interferometer which eliminates amplitude modulation of the input light and determines the frequency modulation. Two photodetectors in series are used to receive two outputs of two arms of a Mach-Zender interferometer. The outputs of the photodetectors are summed. The path length difference is controlled by a heater which itself is controlled by a controller. The controller selectively controls the heater based on how much non-zero components are present in the output of the photodetectors.