Vol. 2 Number 7September 2013

Artic

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News Letter

newsletter@fiberoptika.com

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Chirped fiber bragg gratings for dispersion compensation Shweta Pant

Optical fiber playing the most active role in communication nowadays is definitely the fastest,

reliable and secure mode of communicating information. In addition it has an enormous capacity of

carrying information which we call technically as bandwidth. Optical fiber can carry information,

modulated or non-modulated, to thousands of kilometres without much loss. This feature of optical fiber is

what makes it most attractive for long haul communications.

The grey side of the optical fiber is loss due to dispersion which is most prominent among all the

losses occurring in the fiber communication. Dispersion is an effect which leads to the loss of information

as light travels through some distance. Dispersion is a phenomenon which causes the delay in the light

pulse and hence pulse broadening giving rise to the inter symbol interference (ISI) and eventually loss of

the signal. Hence dispersion is the most undesirable characteristic of an optical fiber. Amongst many type of

dispersion which effects optical fiber communication, chromatic dispersion is the dominant one.

Chromatic dispersion occurs due to the presence of a band of wavelengths (although narrow) in a light

beam passing through the fiber and the wavelength dependency of refractive index. Hence different

wavelengths experience different refractive indices which lead to their varying speeds and hence the

varying delay. This delay effect is commonly known as Chromatic dispersion. Many techniques have been

explored for reducing the dispersion effects. These include dispersion compensating fibers (DCF),

dispersion shifted fibers (DSF), dispersion flattened fibers, solitons and many others.

Chirped fiber Bragg grating is a promising solution for dispersion compensation. Chirp literally

means the varying sounds which birds used to produce and technically refers to the process of introducing

some kind of variation. In fibers, when gratings are made with varying grating period it is said to be chirped

fiber Bragg gratings. Chirped Fiber gratings could be in either increasing or decreasing grating period or

can even be with non-uniform grating periods according to the desired feature. Due to its varying grating

period over the fiber, the light travelling through it encounters different Bragg wavelengths leading to

reflection of different wavelengths with different delays. If this delay is somehow made to compensate the

delay due to chromatic dispersion in optical fibers, the output will be a complete dispersion free

communication system [1]. Chirped fiber gratings are used in WDM links so as to provide an efficient

communication system without dispersion [2].

References:[1] “Fiber Bragg Gratings: The dispersion compensation technology for 40G and 100G optical transport”, Fredrick Sjostrom, Electronic design.

[2] “Fiber Bragg Gratings for dispersion compensation in optical communication systems”, M. Sumetsky, B. J. Eggleton, Journal of optical and fiber communications report, September

2005, Volume 2, Issue 3.

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Front Panel Block

CIRCULATOR Block

This is a three-port optical circulator which acts as anonreciprocal device. If light is launched at Port 1, it will be passed to Port 2.Conversely if light is launched at Port 2 then instead of appearing at Port1, it will appear at Port 3 unlike in most of the optical devices.

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FIBER OPTIKA had attended 2 days Indian Technology Congress 2013 at NIMHANS Convention Center, Bangalore.Our Product LIGHT RUNNER & LIGHTSIM were displayed at the event.

Many Ent repreneurs , Researchers , Technologists, Academicians & Students had visited our stall. The products were liked and appreciated by the visitors.

A series of demonstrations of LIGHT RUNNER & LIGHTSIM were carried out at different Engineering Colleges and Institutes at Jaipur and Delhi . Both the products were well appreciated by the visitors.

Indian Technology Congress 2013On Advanced Communication Technologies

Faculty Development Programme

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Indian Technology Congress 2013

Light Runner Demonstrations at Delhi & Jaipur