Single-mode couplers through end coatings on optical fibers

For designing coatings on fiber ends, one should take into consideration the particular illumination conditions that are due to the propagation of light in the fibers. In a single-mode fiber, the guided wave is strongly polarized and the state of polarization greatly depends on the constraints applied to the fiber. In this research, we use Thelen's formalism to search for a law of index alternation of a layer stack to reduce the polarization rate for a given incidence. We present some examples of calculated results for low-polarizing beam splitters and, after a short description of the manufacturing techniques used, we compare the theoretical results with the effective performances of the single-mode couplers realied.