SL Paper 3
The refractive index of a material is the ratio of the speed of light in a vacuum , to the speed of light in the material or .
The speed of light in a vacuum is 2.99792 × 108 m s-1. The following data are available for the refractive indices of the fibre core for two wavelengths of light:
Outline the differences between step-index and graded-index optic fibres.
Determine the difference between the speed of light corresponding to these two wavelengths in the core glass.
An input signal to the fibre consists of wavelengths that range from 1299 nm to 1301 nm. The diagram shows the variation of intensity with time of the input signal.
Sketch, on the axes, the variation of signal intensity with time after the signal has travelled a long distance along the fibre.
Explain the shape of the signal you sketched in (b)(ii).
A signal consists of a series of pulses. Outline how the length of the fibre optic cable limits the time between transmission of pulses in a practical system.