Fiber Bragg gratings are made by periodically changing the refractive index in the core of an optical fiber using ultraviolet light exposure. This creates a filter that reflects a narrow band of wavelengths, while transmitting others. There are different types of gratings including uniform, apodized, and chirped. Fiber Bragg gratings have various applications including use in telecommunications as filters and dispersion compensators. They offer advantages such as flexibility, low loss, and ability to sense parameters that affect the grating pitch or refractive index.

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2. INTRODUCTION
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• Fibre grating is made by periodically changing the refraction
index in the glass core of the fiber.
• The refraction changes are made by exposing the fiber to the
UV-light with a fixed pattern.
Fig : Diagram of FBG

3. Working
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Fig: working of FBG

4. History Of FBG
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• First fibre grating: Hill ,1978 at CRC
• First holographically written Bragg grating:Meltz, 1989.
• First devices era 1990-1996:
• Kashyap,Russell,Reekje,Malo,Poumellec;Ar ion 244nm.
• Albert ,Dyer,Herman,excimer 1980.

5. Types of fiber bragg gratings
• Due to the change in the induced index change there are
several types of grating:
1 Uniform grating.
2 Apodized grating.
3 Chirped grating
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6. UNIFORM FBG APODIZED FBG
1.Here the grating is 1.the refractive index of the
uniform throughout grating approaches to
the core. Zero at the end of grating.
2 this is simplest 2 there is variation
type of of induced refractive
Bragg grating. Index change.
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7. Grating Waveforms
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• There are mainly two methods of fabrication:
1. Transverse Holographic Method.
2. Phase Mask Method.
FABRICATION OF FBG

9. TRANSVERSE HOLOGRAPHIC
METHOD
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Fig : Transverse holographic method

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APPLICATION OF FBG
• Telecommunication-Filters.
• Wavelength Division Multiplexing (WDM) systems.
• Pump laser.
• Gain flattening filters.
• Highly selective filters .
• Chromatic dispersion compensators .

11. FABRY-PEROT FILTER
• It consists of two FBGs with a cavity between them.
• It passes only particular frequencies for which the cavity is at
resonance.
• The spacing between these frequencies is called as free spectral
range.
• The bandwidth of the filter depends on the reflectivity.
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FABRY PEROT FILTER

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ADVANTAGES OF FP FILTER
• Bandwidth above 100MHz.
•Easy to manufacture.
• Low insertion loss.

14. APPLICATION SECTORS OF FBG
FIG : sectors of FBG
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15. ADVANTAGES OF FGB
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• Flexibility.
• Low insertion loss.
• Low cost.
• Low transmission loss.
• Electrically inert.
• Peak reflectivity in OFBG can BE AS HIGH 99%.

16. DEVOLOPING APPLICATIONS
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• Aerospace Applications.
• Bragg Grating Sensors in Marine Applications.
• Civil Engineering Structural Monitoring.
• Distributed strain sensors , small , robust.
• Medical Applications.
• Nuclear Power Industry.
• Power Transmission Lines.

17. CONCLUSION
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• FBGs have revolutionized the communication industry by
providing high performance, more reliable telecommunication
links.
• They reflect a very narrow band of frequency, but can be
designed to have more complex responses.
• They can sense parameters which vary the pitch or refractive
index of grating.

18. REFRENCES
1. Wei-Chong Du, Xiao-Ming Tao and HWa Yaw Tam: Fiber
Bragg Grating cavity sensor, IEEE nics technology
letters,vol.11,no.1,January 2013.
2. Turan Erdogan: Fiber Grating Spectra, Journal of
lightwavetechnology,vol.15,no.8,August 2012.
3. Kenneth O. Hill, Gerald Meltz: Fiber bragg grating
technology fundamentals and over view, Journal of light
wave, vol.18,no.5,August 2011.
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Thank
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