PM Optical Circulator

Hi.
Polarization-Maintaining (PM) Optic Circulators are non-reciprocating, unidirectional, three-port devices that are used in a wide range of optical setups. Available with a center wavelength of 1064, 1310 (O-Band), or 1550 nm (C-Band), these circulators are designed to work with light that is launched into the slow axis. Choose from versions with no connectors, FC/PC connectors, or FC/APC connectors.An optical circulator is analogous to an electronic circulator and both perform similar functions. An optical circulator is a three-port device that allows light to travel in only one direction. A signal entering Port 1 will exit Port 2 with minimal loss, while a signal entering Port 2 will exit Port 3 with minimal loss. Light entering port 2 experiences a large amount of loss at port 1, and light entering port 3 experiences a large amount of loss at ports 2 and 1. Optical circulators are non-reciprocal devices. This means that any changes in the properties of the light caused by passing through the device are not reversed by traveling in the opposite direction.
You may refer to these links for the design of PM circulator. I hope it helps.
https://www.agiltron.com/pdfs/1500%20pm%20circulator.pdf
http://www.phoenixphotonics.com/website/products/documents/PolarizationMaintainingCirculator_v01401.pdf
http://www.acphotonics.com/products/Product%20files/Short%20Wavelength%20Circulator/980nm%20PM%20Circulator.htm

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Further i want to add that because of its high isolation and low insertion loss, optical circulators are widely used in advanced communication systems as add-drop multiplexers, bi-directional pumps, and chromatic dispersion compensation devices.The example to the left depicts the use of a circulator to drop an optical channel from a DWDM system using a Fiber Bragg Grating (FBG). The input DWDM channels are coupled into Port 1 of the device with a FBG device connected to Port 2. The single wavelength reflected from the FBG then reenters the circulator in port 2 and is routed accordingly to Port 3. The remaining signals pass through the FBG and exit on the top fiber.Circulators can also be used to send optical signal in two directions down a single fiber. A circulator is located at both ends of the fiber. Each circulator functions to add a signal in one direction while removing the signal in the other. See the example to the right.
Here are few more links which can prove very useful to you.
https://www.oplink.com/pdf/PMOC-S0067.pdf
http://www.lasercomponents.com/de/?embedded=1&file=fileadmin/user_upload/home/Datasheets/opto-link/cir-pm.pdf&no_cache=1
https://www.agiltron.com/pdfs/1500%20pm%20circulator.pdf

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