Optical circulators typically have three ports: an input, a common port and an output. The light from input port is guided out at the common port, while the light fed in from the common port can only emit from the output port. Optical circulators can be used to separate the light transmitted in opposite directions inside a single optical fiber. They are used together with fiber gratings components in multiplexing or sensoring systems, in bi-directional ommunications and in optical filter systems. We provide 3-port circulators with low insertion loss, high isolation and polarization insensitive performance. Advanced models include 4-port, wide band (C and L bands) and polarization maintaining circulators.