Submarine cables are equipped for use in fresh water or salt water. They must be protected against severe mechanical stress e.g. from boat anchors or fishing equipment.
photograph of a fiber-coupled diode laser

Figure 1: Photograph of fiber-coupled diode lasers from Coherent, having different kinds of fiber-optic cables. The image was kindly provided by Coherent.

For indoor cables, fire safety is an important aspect, whereas for outdoor cables, moisture resistance and temperature tolerance are factors of high interest. Special aerial/self-supporting cables, which can be exposed to wind and sunlight in free air (hanging on poles), must have a particularly high pulling strength and overall robustness, using some steel or aramid yarn.
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Outdoor cables could easily tolerate indoor conditions, but are often not allowed for indoor use (or only with certain restrictions) due to issues with fire protection.

The detailed construction for a fiber cable can be relatively sophisticated, optimized for an appropriate trade-off between strength, diameter, weight, fire resistance, cost and other possibly relevant properties. For example, the mechanical details can have an influence on polarization mode dispersion.