Gap loss

The losses tend to be proportional to the ratio of the core radius to the size of the gap or displacement.

Formulas, examples and graphs can be found at Fiber Optic Communication - Couplers and Connectors Gap loss can be reduced by filling the gap with a gel that matches the index of refraction of the fiber as closely as possible.

The light that crosses the gap and enters the next section of cable is broken up.

[2] Gap loss can be caused by many factors, but the most common is poorly fitted multi-sectional fiber optic cables.

If there is a break in a directly buried fiber optic line then usually there will simply be a loss of signal.