Core Concentricity

The core-cladding concentricity defines the relative position of the core with respect to the cladding in an optical fiber offering a clear indication of how well centred is the fiber core within the cladding of the fiber.The core-cladding concentricity is one of the most important factors affecting the loss of a joint (splice or connection point) between two optical fibers. The core centre should be as close as possible to the central axis of the fiber. This means that if the fibers on both sides of the joint have their cores perfectly centred, then the alignment of the fibers will be much easier and the splice loss significantly lower.

If both fibers have a core-cladding concentricity of (for example) one micron, then the maximum offset possible between the two cores when the fibers are cladding-aligned is two microns creating an optical loss proportional to this offset and the core dimensions. In a fusion-splice, this optical loss is minimized by effectively aligning the fiber cores rather than their claddings. In connectors, each connector ‘half’ is rotated relatively to a reference during its manufacture reaching an optimum position closest to the geometric centre of the connector body.


Related Terms: Cladding, Connector Types, Core , Core Concentricity