Figure shows the schematic diagram of a fiber optic communication system. The major components of an optical fiber communication system are
i. The optical transmitter
ii. The optical fiber
iii. The optical receiver
PRINCIPLE:
Basically, a fiber optic system converts an electrical signal to an infrared light signal. This signal is transmitted through an optical fiber. At the end of the optical fiber, it is reconverted into an electric signal
Optical fibres used as transmission medium to compensate for losses during transmission repeatrs or optical amplifier can be used at regular intervals. Required characteristics are low dispersion, lower fibre non linearity, low attenuation, high optical signal to noise ratio, large repeater span.
Optical detector detects and convert optical signal to proportional electrical signal.
Eg: Photo diodes, Photo transistors etc
Requirements are sensitive at operating wavelength, requirements are sensitive at operating wavelength, low power consumption and operating voltage, fast response active area match fibre parameter, temperature stability small size and cost capability of internal gain, low noise.
Repeaters and Optical Amplifier:
To compensate for signal degradation in long distance convert optical signal to electrical signal, restores the signal used then converting back to optical signal for further transmission. This method increases cost, complexity and reduces operational bandwidth. Optical amplifiers simply amplify the optical signal. They provide improved SNR due to all optical domain operation.
Fibre Couplers and Fibre Connectors are used to distribute light from main fibre into one or more branches of fibres and to convert one fibre with another.
Advantages of Optical Fibre Communication:
• Wider Bandwidth
• Small Size and weight
• Electrical Isolation
• Immunity to interference and cross stock (free from EMI, RFI, EMP)
• Signal Security
• Low transmission loss
• Flexibility
• System Reliability
