Working of Fiber Optic Cables

Working of Fiber Optic Cables

• Light from a laser enters at one end of the fibre striking the surface of the glass at an angle greater than the critical angle.
• Total internal reflection occurs at the glass surface and the light cannot escape until it reaches the other end of the fibre.
• Both visible light and infra-red can be used as they can travel long distances in glass with very little being absorbed.
• The plastic coating prevents scratches on the glass surface which can allow the light to escape from the side of the fibre.

	Single Mode	Multi Mode	Plastic
Diameter	8.3 to 10 microns	50 to 100 microns	>0.5 millimeter
Wavelength	1310 to 1550nm	850 to 1300nm	650 to 850nm
Bandwidth	Infinite	10 to 100mbs	2Ghz
Cost	More	Moderate	Less
Size	Smaller	Moderate	Larger
Loss	0.5dB per Km	3dB per Km	0.15-0.2dB per meter