LOCAL OSCILLATOR AND ITS USE

摘要

PROBLEM TO BE SOLVED: To provide a local oscillator having a stabilized frequency, having small number of constituents and less electric consumption which is not affected by constituent variation and changes in environment. SOLUTION: This local oscillator generates high frequent signals in narrow band that are mixed directly with first received signals that are generated from a first avalanche photodiode by the light information being made incident into first avalanche photodiode (APD2) that is biased in the opposite direction. The local oscillator is set in a high frequency resonance circuit in which the depletion layer capacitance (CAPD) of first avalanche photodiode (APD2) is controllable. Resonance frequency of this resonance circuit that forms high frequency signals is to be decided by a selective adjustment of a control unit that is activated by reference oscillator 6.