Two types of optical circulator are examined, a perfectly circulating four-port optical circulator and three-port optical circulator. A three-port and four-port optical circulator designed based on Silicon on Insulator material. The recommend design was formed by coupling effect of waveguides to acquire reduce losses and compact size. The performance of both optical circulators has been decomposed using FDTD photonics simulation methods. The maximum size of three-port optical circulator is 16μm×21μm, and the maximum size of four-port optical circulator is 19μm×19μm. The effective wavelength range of optical circulator is 1.5μm-1.6μm. Proposed design can be used for future photonics integrated optical circuits and for speedy communication due to small size.