You may have heard about LC fiber patch cables or MTP/MPO fiber cables while talking about fiber optic patch cables. There are few other special fiber patch cables apart from these cables for example mode conditioning patch cables. Here we will get to know about another special fiber patch cable that is polarization maintaining (PM) fiber patch cables.
PM Patch Cables
At first, we should know the basic definition of the Polarization maintaining patch cable. PM patch cords rely on a high-precision butt-style connection technique. By using male connectors with a positioning key, the PM axis orientation is maintained and a bulkhead female receptacle along with a tight tolerance keyway provides good repeatability in extinction ratios and insertion losses.
Need of PM Patch Cables
Stresses are induced in the fiber when a normal fiber is bent or twisted and the polarization state of light traveling through the fiber is changed due to this stress. Final output polarization will vary with the time if the fiber is subjected to any external perturbations, say changes in the fiber’s position or temperature. It is true for short lengths of fiber and in various applications that need a constant output polarization from the fiber; it is not at all valid.
Polarization maintaining splitter is developed to solve this problem. For two perpendicular polarizations traveling through the fiber, these fibers induce a difference in the speed of light. Two principal transmission axes within the fiber are created by this birefringence which is termed as the fast and slow axes of the fiber. By providing input light into a PM fiber there occurs linear polarization and orientation along with one of these two axes. The output light from the fiber will remain linearly polarized and is aligned with that axis, even when it is put to some kind of external stress. Polarization to at least 30dB at 1550 nm can be maintained by a one-meter long connectorized patch cord that is constructed with PM fiber when used properly. However, how well a PM fiber maintains polarization will depend on the input launch conditions into the fiber. The alignment between the polarization axis of the light with the slow axis of the fiber is the most important factor.
Main source: https://fibermart.jimdofree.com/
