Patent ID: 10261246

Abstract:
A higher-order mode (HOM) fiber is configured as a polarization-maintaining fiber by including a pair of stress rods at a location within the cladding layer that provides for a sufficient degree of birefringence without unduly comprising the spatial mode profile of the propagating higher-order modes. Long-period gratings are used as mode couplers at the input and output of the PM-HOM fiber, where the gratings are formed by exposing areas of the core region orthogonal to the position of the stress rods. The diameter of the stress rods (D) and displacement of the rods from the center of the core region (R1) are controlled to yield a configuration with an acceptable birefringence and polarization extinction ratio (PER) within the HOM fiber, even in situations where the fiber is bent (a bend radius less than 50 cm).