We have developed a polarizationhyphen;independent optical circulator for optical transmission systems whose overall dimensions are 25times;18times;18 mm3. The insertion losses and the isolations of the circulator are about 2.0ndash;2.2 and 20ndash;21 dB, respectively, at a 1.3hyphen;mgr;m wavelength. The circulator consists of lsquo;lsquo;polarization separatorsrsquo;rsquo; on either side of a Faraday rotator and a lgr;/2 retardation plate. The polarization separator separates the incident beam into two polarized parallel beams with orthogonal linear polarizations. The separation of the two beams is 3.2 mm. The Faraday rotator consists of a yttriumhyphen;ironhyphen;garnet (YIG) crystal and Smhyphen;Co permanent magnets. The size of the YIG block is 2.25 mm lengthtimes;4.5 mm widthtimes;1.5 mm thick. The halfhyphen;wave plate of the circulator is made of a white mica.
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