FIBER OPTIC SENSORS

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FIBER OPTIC SENSORS:

F IBER O PTIC S ENSORS Presented by Sherry Joseph George S7 A R.No.42 COLLEGE OF ENGINEERING CHENGANNUR

Contents:

Contents What is OFS Basics of Optical fiber Principle Types of OFS Applications Advantages Conclusion COLLEGE OF ENGINEERING CHENGANNUR 2 Optical fiber sensors

FIBER OPTIC SENSORS?:

F IBER O PTIC S ENSORS? Optical fiber sensor : A sensor that measures a physical quantity based on its modulation on the intensity , spectrum , phase , or polarization of light traveling through an optical fiber. To measure physical parameters such as strain, temperature, pressure, velocity, and acceleration Optical fibers : strands of glass that transmit light over long distances (wire in electrical systems) Light : transmitted by continuous internal reflections in optical fibers (electron in electrical systems) 3 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

OPTICAL FIBRE:

OPTICAL FIBRE COLLEGE OF ENGINEERING CHENGANNUR 4 Optical fiber sensors

Total Internal Reflection:

Total Internal Reflection COLLEGE OF ENGINEERING CHENGANNUR 5 Optical fiber sensors

PRINCIPLE:

PRINCIPLE Procedure in Fiber optic sensor systems : Transmit light from a light source along an optical fiber to a sensor , which sense only the change of a desired environmental parameter . The sensor modulates the characteristics (intensity, wave length, amplitude, phase) of the light. The modulated light is transmitted from the sensor to the signal processor and converted into a signal that is processed in the control system. The properties of light involved in fiber optic censors: reflection, refraction, interference and grating 6 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

TYPE OF FIBER OPTIC SENSORS:

T YPE OF F IBER O PTIC S ENSORS Fiber optic censors can be divided by: Places where sensing happens Extrinsic or Hybrid fiber optic sensors Intrinsic or All-Fiber fiber optic sensors Characteristics of light modulated by environmental effect Intensity-based fiber optic sensors Spectrally-based fiber optic sensors Interferometeric fiber optic sensors 7 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

Extrinsic or Hybrid Fiber Optic Sensors:

Extrinsic or Hybrid Fiber Optic Sensors Consist of optical fibers that lead up to and out of a “ black box ” that modulates the light beam passing through it in response to an environmental effect. Sensing takes place in a region outside the fiber. 8 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

Intrinsic or All-Fiber Optic Sensors:

Intrinsic or All-Fiber Optic Sensors Sensing takes place within the fiber itself. The sensors rely on the properties of the optical fiber itself to convert an environmental action into a modulation of the light beam passing through it. 9 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

Typical Optical Fiber Sensing Mechanism:

Typical Optical Fiber Sensing Mechanism Light source Focus lens Transmission Measurement Sensing element Photo-detector COLLEGE OF ENGINEERING CHENGANNUR 10 Optical fiber sensors

Optical Transmitter:

Optical Transmitter Definition : a device that converts electrical signal into optical signal Lasers Fabry-Perot Lasers (FP) Distributed Feedback Lasers (DFB) Vertical Cavity Surface Emitting Lasers (VCSEL) Light Emitting Diodes (LED) Surface-Emitting LED (SLED) Edge-emitting LED (EELED) COLLEGE OF ENGINEERING CHENGANNUR 11 Optical fiber sensors

Optical Receiver:

Optical Receiver Definition : convert optical signal into electrical signal Types : p-i-n photodetector: photon-electron converter Avalance photodetector (APD): more sensitive for high speed systems COLLEGE OF ENGINEERING CHENGANNUR 12 Optical fiber sensors

Intensity-based Fiber Optic Sensors:

Intensity-based Fiber Optic Sensors Example1: Single fiber reflective sensor Light leaves the fiber end in a cone pattern, and strikes a movable reflector. The relationship between fiber-reflector distance and intensity of returned light Example 2: Bending the fiber As the deformer closes on the fiber, radiation losses increase and the transmitted light decreases. Depend on the principle that light can be modulated in i ntensity by an environmental effect . 13 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

Spectrally-based Fiber Optic Sensors:

Spectrally-based Fiber Optic Sensors Depend on the principle that a light beam can be modulated in wavelength by an environmental effect . Example: Black body radiation When the cavity rises in temperature, it starts to glow and act as a light source. Detectors in combination with narrow band filters are then used to determine the profile of the blackbody curve and in turn the temperature 14 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

Interferometeric Fiber Optic Sensors:

Interferometeric Fiber Optic Sensors The optical phase of the light passing through the fiber is modulated by the field to be detected. This phase modulation is then detected interferometerically , by comparing the phase of the light in the signal fiber to that in a reference fiber. Light is not required to exit the fiber at the sensor to interact with the field to be detected. In intensity based fiber optic censors, light has to leave the optical fiber to interact with the optical sensor at the end of the fiber, leading to substantial optical loss. Fabry-Perot, Sagnac, Mach-Zehnder and Nichelson, polarimetric, and grating interferometers 15 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

What Does F.O.S. Look Like?:

What Does F.O.S. Look Like? Strain Gage Embeddable Strain Gage Pressure Transducer Displacement Transducer Temperature Transducer 16 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

ADVANTAGES:

A DVANTAGES Immunity to electromagnetic interference (EMI) and radio frequency interference (RFI) All- passive dielectric characteristic: elimination of conductive paths in high-voltage environments Inherent safety and suitability for extreme vibration and explosive environments Tolerant of high temperatures (>1450 C) and corrosive environments Light weight, and small size High sensitivity 17 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

GENERAL USES:

G ENERAL U SES Measurement of physical properties such as strain, displacement, temperature, pressure, velocity, and acceleration in structures of any shape or size Monitoring the physical health of structures in real time Damage detection Used in multifunctional structures , in which a combination of smart materials, actuators and sensors work together to produce specific action 18 COLLEGE OF ENGINEERING CHENGANNUR Optical fiber sensors

Conclusion:

Conclusion Optical fiber sensors are superior to electric sensors in terms of sensitivity, immunity to EM radiation.. They can work at very high temperatures. Constantly evolving technology. It has got numerous applications. COLLEGE OF ENGINEERING CHENGANNUR 19 Optical fiber sensors

References:

References Fiber optical intensity sensors : SHI-KAY YAO , senior member , IEEE www.bluerr.com/images/Overview_of_FOS2.pdf Optical Fiber Communications : John M.Senior Fibre Optic Sensors and their applications Fidanboylu , K.a , , and Efendioglu , H. S.b a , Fatih University, Istanbul b Fatih University, Istanbul. www.bluerr.com/images/Overview_of_FOS2.pdf COLLEGE OF ENGINEERING CHENGANNUR 20 Optical fiber sensors

THANK YOU:

THANK YOU COLLEGE OF ENGINEERING CHENGANNUR 21