Optical Solitons

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1. INTRODUCTION

Existence of solitons in nonlinear optical fibres was first predicted by Hasegawa and Tappert in 1973 and its experimental verification came in 1980. Ever since, both experimental and the theorotical physicists have shown keen interest in this topic due to its versatile applications. Optical solitons are formed due to the balance between the group velocity dispersion and the self phase modulation in the anomalous dispersion regime, and the governing wave equation is the.Nonlinear Schrodinger (NLS) equation. Optical solitons can exist in various systems like photonic crystal fibres, bulk materials like photorefractive materials, photopolymers, etc. What follows is an introduction to optical soiltons and their applications. The optical soliton is shown in the following fig.1


Need Of Optical Soliton:


Ok, let’s start with the point which is why we need to develop optical communication systems. Well, we can start by pointing out that the recent increases in internet use have lead to a high demand for communication services. At the moment, unprecedented (has never happened) amounts of information are being transferred over the internet. As a consequence, we need higher and higher transmission rates - especially with the transmission of audio and video files -. For instance, in order to remain competitive, internet providers always need to increase their bit rates (that is the amount of data that they can transmit per second). Unfortunately, the old analogue devices which carry information along copper cables using electrons now have great difficulty in responding to such a huge demand for information. This is mainly due to the fact that they are too slow and too noisy compared to fibre-optic systems. Indeed, these digital optical systems can reach much higher bit rates than electronic devices.

Problems inherent in the propagation of optical pulses along a fibre.
As a matter of fact, propagating optical waves along a fibre is not that simple. (Theoretically, a single optical fibre can transmit up to 25 Tera Bits (1012) per second, which in practice is impossible to achieve). One must take into account three physical phenomena that can distort the optical signals, namely: light loss, dispersion and non-linearity. These effects inevitably restrict the overall performance of fibre-optic systems.

1.2.2 The problem of linear light loss.

We can note that, even though, light is supposed to be trapped inside the fibre core, light loss still does occur. Moreover, additional fibre loss occurs at the connection between two adjacent fibres (given that this connection is never perfect : part of the light is reflected back towards the source). The problem of linear loss is one of the limiting factors of optical transmission techniques, but fortunately, it can be corrected by regenerating the signal power periodically along its path. To that purpose, we make use of amplifiers.


6. CONCLUSION
In this seminar I have presented the concept of optical soliton .Soliton may exist if there is a balance between opposing linear and nonlinear effects. Their interesting and nonintuitive properties make them candidates for various application s in physics.
The canceling of dispersive broadening of pulses makes temporal soli- tons suitable for ultra long haul high bit rate optical communication. On the other hand, the particle-like behavior in interactions, makes possible the use of solitons for ultra fast optical logical devices. It is clear that solitons will play a major role in the next generation of optical communication system.
Also understood need of optical soliton and various application through this paper.