Optical Fibres

Transmission > Optical Fibres

For Transmitting Information by an Optical Fiber, the Information should first be converted to an Optical Signal and reconverted at the Destination, Figure 1.

Figure 1: Light Beam Propagates through an Optical Fiber

In practice, the Optical Signal Attenuates during Transmission over Optical Fiber. The Attenuation depends on the Wavelength of the Light Beam, Figure 2. The Transmission Windows refer to the Wavelength Regions that offer low Optical Attenuation.

Figure 2: The Attenuation-Wavelength Curve and the Transmission Windows of an Optical Fiber

From Figure 2 and Table 1, Infrared Light with Wavelengths of 850 nm, 1,310 nm and 1,550 nm is mostly used. Therefore, the most common devices used as the Light Source in Optical Transmitters are the Light Emitting Diode (LED) and the Laser Diode (LD). They operate in the Infrared Radiation (750nm to 1mm) of the Electromagnetic Spectrum so that their Light Output is usually invisible to the human eye.

Window RangeOperating Wavelength
First Window800 nm – 900 nm850 nm
Second Window1,260 nm – 1,360 nm1,310 nm
Third Window1,500 nm – 1,600 nm1,550 nm

Table 1: Transmission Windows Ranges and Operating Wavelengths of the Optical Fiber

Optical Fibers are replacing Copper Wires to become an important Transmission Medium. Optical Fibers offer over 1,000 times as much Bandwidth as a Copper Wire, and can support Transmission at Gigabits per second.

Transmission > Optical Fibres