- Simple to make
- Low critical angle so tighter curve possible
- Easily scratched leading to light losses.
- Multi-path dispersion leads to sharp pulses becoming rounded and limits maximum rates of pulses.
Step Index Fibres
Cladding = Twenty-five micro meters
Core = Fifty to two-hundred micro meters
Cladding: Low refractive index
Core:High refractive index
- Relatively cheap to make
- Scratch resistant
- Multi-path dispersion
- Limits range and bandwidth.
Graded Index Fibres
Core = Fifty to one hundred micro meters.
Edge = Low refractive index
Centre = High refractive index
- Rays that travels straight through the centre of the fibre goes through more slowly. The rays that travels near the edges travel through more quickly so all the rays take the time the same time to travel regardless of the path they take. Thus preventing dispersion.
- Dispersion is prevented so fibres can be used for longer, higher bandwidth links.
- Difficult to make
- Dispersion can only be prevented at one wavelength.
Cladding = Low refractive index.
Core = High refractive index.
- Single path through the fibre so no dispersion.
- Expensive to make and needs tiny, more expensive lasers to get into the small core.
- Harder to connect as…