What are the different possibilities for delay distortion in fibre optic cabling?
The primary limitation of the signal bandwidth of optical fiber is dispersion. Dispersion, as the term is used in fiber optics, is when one component of the signal propagates faster than another component. This leads to narrow input pulses stretching in duration as they propagate along the fiber, causing the fiber to act as a low-pass filter on the signal.

The main forms of dispersion are

modal dispersion: When the different waveguide modes of multimode fiber propagate at different speeds along the z axis of the fiber. Modal dispersion is why multimode fiber has lower bandwidth-distance capability than singlemode fiber.

chromatic dispersion: When different wavelengths propagate at different speeds due to the material properties of the glass. 

polarization mode dispersion: When different polarizations of light propagate at different speeds due to slight imperfections in the symmetry of the waveguide (or due to deliberately induced asymmetry in polarization-maintaining fiber).