PURPOSE: To provide the optical isolator of a small size which is half the number of parts of the conventional coupler and is simple in optical axis adjustment.
CONSTITUTION: The multiplexer is provided with 4 pieces of optical fiber arrays 31-34, a double refraction crystal 4 provided on one side of one piece of lens 6, a halfwave plate 5 which exists between this lens 6 and the double refraction crystal 4 and covers half the area of the lens 6, a filter 36 which exists on the other one side of the lens 6 and reflects the light of a wavelength λ1, a flat planar magneto-optical crystal 7 determined in length in such a manner that the planes of polarization of incident light and exit light are varied by about (π/8+Nπ/4 (N=0, 1,...) by the magnetization on the other end face of the filter 36 and a reflection plate 37. The multiplexer is so constituted that incident light λ1 on the double refraction crystal 4 from the first optical fiber of the optical fiber array is reflected by the filter 36 and is made incident on the second optical fiber. The reflection plate 37 is so inclined that the incident light λ2 of the wavelength on the double refraction crystal 4 from the first optical fiber passes the halfwave plate 5 and is made incident on the third optical fiber.
KURATA NOBORU
HAYATA HIRONORI
