PURPOSE: To improve the stability or an optical isolator against the variance of temperature or wavelength. CONSTITUTION: This optical isolator 10 is composed of a Farady rotator 12 arranged between a pair of polarization selecting elements 14 and 16. A Farady device having an angleθof rotation smaller than conventional 45 deg. is utilized to improve isolation as a function of the variance of temperature or signal wavelength. Linear reduction ofθis accompanied with some signal loss but linearly increases the stability against temperature and wavelength.
