Optical fibres in communication, engineering and medicine

What you will learn

Fibre applications, operation, benefits and limitations in three sectors.

Specification mapping: A2.2

Prerequisites: A2.1.4

Physical principles

In communication, an LED or laser converts electrical information into modulated light. Light pulses travel through a fibre and a photodetector converts received light back into an electrical signal. Fibres support high data rates and resist electromagnetic interference. Attenuation and pulse dispersion limit transmission distance or bit rate; receivers and repeaters or amplifiers address different aspects of these limitations.

In medicine, an endoscope carries illumination into the body and returns an image. A traditional image bundle must be coherent in the spatial sense: fibres retain the same relative positions at both ends. This differs from phase coherence of light. Modern instruments may instead place an electronic image sensor at the tip. Separate channels may carry tools or deliver laser treatment.

Engineering applications include inspecting inaccessible turbine or pipe interiors and sensing strain or temperature through changes in optical behaviour. Fibre inspection avoids some disassembly and can reach confined spaces. A measurement still needs calibration and an appropriate response range.

Compare alternatives by context: fibres are light, electrically insulating and hard to intercept without disturbing a link, but require careful connectors, bend control and optical conversion equipment. “Immune to electromagnetic interference” does not mean immune to physical damage, signal attenuation or every security risk.

Scientific diagram and interpretation

Light follows a schematic zigzag path inside a higher-index core. At each core–cladding reflection incidence must exceed the relevant critical angle. Not all incident rays are guided.

Worked examples and applications

Choose a link

A cable runs near high-current switching equipment. Fibre avoids electromagnetic pickup in the transmission medium, but the electrical transmitter and receiver still need suitable design.

Preserve an image

If fibres are randomly rearranged between the ends of a traditional imaging bundle, light still transmits but spatial information is scrambled. Retaining fibre order preserves the image.

Common misconceptions

An imaging bundle’s spatial coherence is not the same definition as phase coherence in interference.

Examination technique

For each benefit, name the physical reason and a limitation relevant to that application.

For an explanation, connect the physical cause to its effect. For a calculation, state the model, rearrange before substitution, retain intermediate digits, and finish with units. For a data question, refer to the actual readings and distinguish a trend from proof of a cause.

Check your understanding

Five questions. Choose an option, then Check Answer. Read the feedback and use Try Again to reset. Use Tab between controls, arrow keys within radio groups, and Enter or Space on buttons. These local practice answers are not saved.