In most of senarios, the optical fiber resource is expensive and in shortage, cause of the advancing planning and constrction are not happening always, but the work of solution finding are happening always.

Here we are introducing one mature solution to achieve single fiber bi-directional WDM transmission. In this solution, the mux box integrate one important component, optic circulator,

Optic Circulators are non-reciprocating, one directional, three-port devices that are used in a wide range of optical setups and for numerous applications. Optical circulators have a center wavelength of 1064, 1310 (O-Band), or 1550 nm (C-Band), so DWDM is more generic solution for single fiber bi-directional transmission.

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 to Port 1 will exit Port 2 with minimal loss less than 1.0dB usually, while a signal entering Port 2 will exit Port 3 with the same minimal loss. Light entering port 2 experiences a large amount of loss at port 1, which is named directivity here and more than 50dB usually. 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.

Figure 1, the light path in the link with optic circulator

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. 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 below sample case.

Figure 2, Single fiber bi-directional WDM transmission

Another question is coming, once in the access side, from some important subscribers, several kilometers distance, there is one fiber only also, how to do the connections?

For more information, visit Etern Optoelectronics website: https://www.szetern.com, or email to: sales@szetern.com