OPTICAL ISOLATOR

PROBLEM TO BE SOLVED: To obtain an optical isolator of a water-proof type which obviates the occurrence of the deterioration in optical characteristics and has reliability even when an immersion test is carried out. SOLUTION: This optical isolator is constituted by mounting an optically non-reciprocal part composed of polarizers 1a and 3a and magnetic garnets 2a and 4a which are Faraday rotators on the inside of holders 5a and 5a' to form an assembly section, covering the outer peripheral part of the assembly section with a molding material 6a and tubing 7a in this order and mounting glass plates 9a and 9a' to the flanks perpendicular to an optical axis. The assembly section is hermetically sealed by the molding material, the tubing and the glass plates.