Comparison of optical and electrical links

The choice of transmission medium is an important criterion in the design phase of a communication system. The transmission medium can be copper for coaxial cables and twisted pairs, silica or plastic for optical fibers, or air for microwave or free-space links. When designing a communication system, it is essential to define the performance required of the transmission medium: communication distance, bandwidth and electromagnetic immunity are all factors that characterize these media. However, the choice is not an easy one, given the variety of media and their advantages and/or disadvantages.

This article compares electrical links with optical links, both guided and unguided. Although optical transmissions are widely used in telecommunications, they suffer from certain prejudices which this article will attempt to clarify and dispel. After a comparison of the system characteristics of transmission media, guided and free-space transmissions will be analyzed point by point according to their fields of application.

The abbreviations used in the text are explained in the table 1 .

Readers are invited to consult the following articles in the Techniques de l'Ingénieur collection:

• Optical fibers for telecommunications [E 7 110] of the Telecoms Treaty;

• Fiber optic transmission systems [TE 7 115] of the Telecoms Treaty;

• Passive optical network [TE 7 119] of the Telecom Treaty ;

• Submarine fiber optic cables [E 7 555] of the Telecom Treaty ;

• Microwave links [E 7 520] of the Telecoms Treaty;

• Optical interconnections in this treatise;

• Optical connectors .

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