Active Communication Company Limited (ACCL) stand at the forefront of IT infrastructural developments within the United Kingdom. Their gifted team is constantly called upon to improve network capabilities throughout corporate, commercial, industrial and educational outlets.
One optical fibre is made up of the following:
Core– The centre of the Fibre, constructed of thin glass through which the light travels
Cladding– surrounds the core to reflects the light back into the core
Buffer coating– Protection from damage and moisture is provided by a plastic coating
Hundreds or thousands of optical fibers are arranged in bundles in Fibre Optic Cables. The bundles are then protected by the jacket of the cable.
Optical fibers come in two types:
Single-mode fibers~ smaller cores, approx 3.5 x 10-4 inches in diameter which transmit infrared laser light with wavelength equal to 1,300 to 1,550 nanometers.
Multi-mode fiberslarger cores, approx 2.5 x 10-3 inches in diameter which transmit infrared light at wavelength equal to 850 to 1,300 nm, using light-emitting diodes, commonly referred to as LED’s.
Some optical fibers can be made from plastic. These fibers have a larger core of 1mm in diameter and transmit visible red light with wavelength equal to 650nm using LEDs.
To put fibre optic cabling into perspective, the human eye is sensitive to light whose wavelength is in the range of about 400 nanometers (millionths of a meter) to 700 nanometers. For fiber optics with glass fibers, we use light in the infrared region which has wavelengths longer than visible light, typically around 850, 1300 and 1550 nm. We use infrared because the weakening of the fiber is much less at those wavelengths.
Two factors cause weakening of glass optical fibers, absorption and scattering. Scattering is caused when light bounces off molecules in the glass. Absorption is caused by minute amounts of water vapor in the glass creating water bands.
Fiber optic transmission wavelengths are determined by two factors: longer wavelengths in the infrared for less scattering in the glass fiber and at wavelengths which are between the absorption bands. The normal wavelengths are 850, 1300 and 1550 nm.
So if the weakening is less in longer wavelengths why don’t we make them even longer? The infrared wavelengths travel between light and heat, at longer wavelengths close temperatures becomes background noise, disturbing the signals.
Summary
So to summarise the three prime wavelengths for fiber optics, 850, 1300 and 1550 nm drive everything we design or test. Multimode fiber is designed to operate at 850 and 1300 nm, while single-mode fiber optic cable is optimized for 1310 and 1550 nm.
