How is fiber optic communication used in industries?
What is fiber-optic technique?
General Optical Fiber Communication System
• Two main categories of optical fiber used in fiber-optic communications are multi-mode optical fiber and single-mode optical fiber.
• A range of different sensors can be used, either temporarily hung-off in the well or permanently installed as part of the well construction.
• They provide distributed measurements, are passive, potentially low-cost, have a long service life and a small form-factor.
• As displayed in Figure a), an optical fibre typically consists of three layers . The light propagates in the core, guided by the contrast in refractive index between the core and the surrounding cladding.
Need of fiber optic optic communication
Fiber optic communication system has emerged as most important communication system. Compared to traditional system because of following requirements :
In long-haul transmission system, there is a need of low loss transmission medium
There is a need of compact and least weight transmitters and receivers
There is a need for an increased span of transmission
There is a need of increased bit rate-distance product. A fiber optic communication system fulfills these requirements, hence most widely accepted.
Basic block diagram of optical fiber communication
system consists of following important blocks:
- Information channel
The coupler feeds power into the information channel. For an atmospheric optical system, the channel coupler is a lens used to collimate the light emitted by the source and direct this light towards the receiver. The coupler must efficiently transfer the modulated light beam from the source to the optical fiber. The design of the channel coupler is an important part of the fiber system due to the possibility of large losses
The information channel is the route between the transmitter and the receiver. In fiber optic communications, the channel is a fiberglass or plastic. Desirable characteristics of the information channel include low attenuation and wide cone angle of light acceptance. Optical amplifiers increase the power levels of weak signals. Amplifiers are needed in very long links to provide sufficient power to the receiver. The repeaters can be used only for digital systems. They convert the weak and distorted optical signals into electrical and then regenerate the original pulse trains for greater transmission.
Another important property of the information channel is the propagation time of the poles traveling along it. A signal that propagates along a fiber normally contains a range of optical frequencies and divides its power along several ray trajectories. This results in a distortion of the propagation signal. In a digital system, this distortion appears as an extension and deformation of the pulses. The dispersion is so large that the adjacent pulses begin to overlap and become unrecognizable as separate bits of information
The information that is transmitted is detector. In the fiber system, the optical wave is converted into an electric current by means of a photodetector. The current developed by the detector is proportional to the power in the incident optical wave. The output current of the detector contains the information transmitted. This detector output is filtered to eliminate constant polarization and then amplify. x The important properties of photodetectors are their small size, economy, long service life, low power consumption, high sensitivity to optical signals and rapid response to rapid variations in theoretical power.
Signal processing includes filtering, amplification. Proper filtering maximizes the ratio of signal to unwanted power. For a digital system decision circuit is an additional block. The bit error rate (BER) should be very small for quality communications.
The electrical form of the message emerging from the signal processor are transformed into a soud wave or visual image. Sometimes these signals are directly usable when computers or other machines are connected through a fiber system.
Advantages of Optical Fiber Communication
- Wide bandwidth
The light wave occupies the frequency range between 2 x 1012 Hz to 3.7 x 1012 Hz.Thus the information carrying capability of fiber optic cables is much higher.
- low losses
Fiber optic cables offers bery less signal attenuation over long distances. Typically it isless than 1 dB/km. This enables longer distance between repeaters.
- Immune to cross talk
Fiber optic cables has very high immunity to electricaland magnetic field. Since fiberoptic cables are non-conductors of electricity hence they do not produce magnetic field.Thus fiber optic cables are immune to cross talk between cables cause dby magnetic induction.
- interference immune
Fiber optic cables are immune to conductive and radiative interferences caused by electrical noise sources such as lighting, electric motors, fluorescent lights.
- light weight
As fiber cables are made of silica glass or plastic which is much lighter than copper or aluminium cables. Light weight fiber cables are cheaper to transport.
- Small sizes
The diameter of fiber is much smaller compared to other cables, therefore fiber cable is small in size, requires less storage space.