2. Why use optical fibre?
Advantages
• Higher bandwidth than copper
• Smaller, lighter than copper
• Does not suffer from
electromagnetic interference
• Long distance communication
• Intrinsically safe
Disadvantages
• Cannot carry power
• Cost of equipment (test,
termination and transmission)
• Highly skilled to install optical
fibre
3. History of optical fibres
• 1870 John Tyndall showed that
light could be guided in a thin
stream of water.
• 1960 introduction of lasers 1962
introduction of semiconductor
lasers.
• 1970 introduction of glass that
gives loss of 20 dB/km giving low
enough loss for communications.
8. 62.5/125 mm Optical fibre
• Known as OM1
• Optical Multimode 1
• Core of optical fibre has diameter
of 62.5 mm (0.00625 cm)
• Cladding of optical fibre has
diameter of 125 mm (0.0125 cm)
9. 50/125 mm Optical fibre
• Either OM2 or OM3
• Optical Multimode 2 or
Optical Multimode 3-laser enhanced
• Core of optical fibre has diameter
of 50 mm (0.005 cm)
• Cladding of optical fibre has
diameter of 125 mm (0.0125 cm)
10. 9/125 mm Optical fibre
• Known as OS1
• Optical Single-mode 1
• Core of optical fibre has diameter
of 9mm (0.0009 cm)
• Cladding of optical fibre has
diameter of 125 mm (0.0125 cm)
11. Difference between multimode and
single mode optical fibre
• Multimode fibre; light can
take many paths down
the core of the optical
fibre e.g. m0, m1, m2 etc
• This is due to the large
size of the optical core
either 50 or 62.5 mm.
• Singlemode fibre; light
can only take one path
down the core of the
optical fibre.
• This is due to the small
size of the optical core of
9 mm.
Cladding
Core
Cladding
Core
Cladding
Cladding
m0
m1
m2
m0
12. Wavelength
Frequency [Hz]
102 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18
3000km 30km 300m 3m 3cm 0.3mm 3 mm 30nm 0.3nm
NF
range
HF
range
Microwaves
range
Optical
range
X / gamma
range
13. Wavelengths of light used (l)
• Wavelength is defined as the
distance between the one point of the
wave and the next corresponding
point on the wave.
• For multimode the main wavelengths
used are 850 nm (first window) and
1300 nm (second window).
• For singlemode the main
wavelengths used are 1310 nm
(second window) and 1550 nm (third
window).
• 1 nm is equivalent to 0.000001 mm
1 wavelength
Wavelength
Frequency [Hz]
102 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 10 17 10 18
3000km 30km 300m 3m 3cm 0.3mm 3 mm 30nm 0.3nm
NF
range
HF
range
Microwaves
range
Optical
range
X / gamma
range