We are at the edge of another industrial revolution, namely the information age.
Although we may have not noticed, the amount of information generated by humanity is doubling every few months. In order to respond to such a huge demand for information modern communications relies on fast digital optical fiber systems which are fast emerging as dominant transmission medium within the major industrialized societies.
Even in advanced fiber optics systems longer spans of fiber with higher bit rates are desired. Researchers have been constantly struggling since the development of optical fiber in early 60’s to achieve the dream seen with it’s developments but without much success till a couple of years back.
Optical communication system are no longer the pipedreams of the future with the advent of this new data transmission scheme in optics which has facilitated to transmit data at rates in excess of 50 Gb/s, at a distance of 19000 kms requiring no repeaters and with no errors. At this rate one bibble could be sent to everyone on earth- people--- in just 10 days.
The new technique utilizes something called “SOLITON PULSES”.
Optical Solitons are essentially “stable pulses” that travel without changing their shape: they do not disperse and robustly resist perturbations in the physical medium that supports them. They represent one of the most exciting and fascinating concepts in modern communications, arousing special interest due to their potential applications in Optical Fiber Communication.
With this presentation I have tried to focus on the explicit integration of analytical and experimental methods in non linear optics specially “Optical Soliton Communication”.
What Is A Soliton Pulse?
Soliton is a bell shaped pulse of light -- of sufficient intensity and correct wavelength traveling through a non linear optical fiber. They are very short pulses of light that show the peculiar characteristic of maintaining their pulse width in the presence of chromatic dispersion as they propagate in the optical fiber.
Solitons, and any encoded information they carry have a strong resistance to interferences.Solitons are essentially “stable pulses” that travel without changing their shape: they do not disperse and robustly resist perturbations in the physical medium that supports them.
Properties of Soliton:
* Solitons have very short pulse duration, a single soliton is only 1 picosecond long (1 million millionth of a second). They have high stability and can propagate independently along its course forever.
* Solitons can exist when dispersion and non linearity effect of the fiber counteract one another as a result they propagate without deterioration over many thousands of kilometers.
* Soliton dynamics are governed by the Nonlinear Schrodinger Equation. Split-step Fourier Method can be applied to efficiently numerically solve the Nonlinear Schrodinger equation.
* During collision between two soliton pulses, they pass through each other, coming out of the interaction retaining their identities. Since these pulses behave more like particles than waves, they are named as solitons.
* Since solitons are non linear waves, the Principle of Superposition does not hold due to the fact that the wave's sprrd depends on the amplitude.
* Recently solitons that have decayed, had been revitalized, restored and relaunched following a stage of amplification.
Propagation Of Optical Soliton
An optical soliton is created in a optical fiber due to the interaction between two contradictory properties of the wave exhibited while transmission -- “Dispersion” and “Non linear effects".
The medium for transmission of optical signal is the optical fiber which is a dielectric medium since it is made of glass. The physical principle used for this transmission is “Total Internal Reflection” which states that when light travels from one medium to another whose index of refraction is lower, there is a critical angle of incidence below which the light will be totally reflected back in the first medium with no light penetrating the interface.
Generation Of Optical Soliton
For optical soliton pulses the fiber dispersion and nonlinearity can under certain circumstances cancel each other thus allowing the solitons to remain undistorted over long distances. One important aspect in this context is the generation of jitter and chirp free short optical pulses at high bit rates and in the 1550 nm region where optical fibers have the lowest loss.
Transmission Of Optical Soliton
The most promising application of soliton theory is in the field of optical communication. Optical solitons proves to be an elegant method to overcome the dispersion of fiber and exploit the nonlinearity.
DWDM (Dense Wavelength Division Multiplexing)
Dispersion Managed Solitons
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