If the optical fiber is not perfectly circular, will it misalign during splicing?
Yes, if optical fibers are not perfectly round or have geometric deformations, this will directly lead to core misalignment during fiber optic splicing (including mechanical connector mating and fusion splicing), resulting in significant insertion loss and degraded return loss.
In optical engineering, this type of misalignment due to geometric deformation is primarily determined by the following three related physical parameters:
- Cladding Non-circularity: The degree to which the cross-section of the cladding deviates from a perfect circle. It is typically defined as:
\text{Non-circularity} = \frac{D_{\max} - D_{\min}}{D_{\text{nominal}}} \times 100\%
where D_{\max} and D_{\min} are the maximum and minimum outer diameters of the cladding cross-section, respectively. - Core-to-cladding Concentricity Error: The deviation distance between the physical center of the core and the geometric center of the cladding. This is one of the most critical geometric indicators determining the insertion loss in single-mode fiber connections.
- Core Non-circularity: The extent to which the core cross-section is elliptical rather than perfectly circular.
I. Specific Impacts of Geometric Non-circularity on Different Connection Methods
1. Mechanical Connectors (e.g., FC/PC, FC/APC)
In fiber optic mechanical connectors, two fibers are inserted into a zirconia ceramic ferrule. The inner diameter of the ferrule (typically 125.5\ \mu\text{m}