University of Baghdad college of engineering electronics & comm.dept .

1. University of Baghdadcollege of engineering electronics & comm.dept. Optical fiber as pressure senor Student name: ZaianbRaad

2. Introduction • A fiber optic sensor is a sensor that uses optical fiber as the sensing element. • Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber so that the quantity to be measured modulates the intensity, phase, polarization, wavelength or transit time of light in the fiber

3. Introduction • This optical fiber sensor measures pressure and sends the measurements to the user via an optical fiber. • An optical fiber pressure sensor for measuring a pressure on the basis of an optical power loss depending on a configuration change of an optical fiber.

4. Optical fiber pressure sensor techniques • In general optical fiber pressure sensor use two types of techniques to measure the pressure, such as: • Fabry-Perrot • Fiber Bragg

5. Fabry-Pérot • Working on the principal of light reflection between two reflecting surfaces. • light source is injected and guided into a multimode optical fiber. • This light is then bounced through two reflecting surfaces a large number of times until it reaches the sensing tip. • Light escaped during this process is encoded, providing the measurements for the physical parameter.

6. Fiber Bragg grating(FBG) • A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. • This is achieved by creating a periodic variation in the refractive index of the fiber core, which generates a wavelength specific dielectric mirror. • A fiber Bragg grating can therefore be used inoptical filter to block certain wavelengths, or as a wavelength-specific reflector.

7. Fiber brag grating structure

8. Fiber optic pressure sensor operation

9. Pressure sensor operation Pressure sensor is consist of • . An optical fiber • glass tube fiber spacer are bonded in the center opening of the sensing element using epoxy. • The optical gap between the bottom of the diaphragm and the end face of the fiber is a Fabry-Perot cavity.

10. Optical fiber pressure sensor operation • light interference resulting from the internal reflection of light at the fiber end face (R1) and reflected light off of the bottom surface of the diaphragm (R2) is used to monitor the optical path length. • The optical gap varies with diaphragm deflection, which in turn varies with applied pressure. • The reference port on the bottom of the sensing element acts as a vent through which air can pass to maintain a constant pressure on the reference side of the diaphragm.

11. Pressure sensor operation • The light beam is reflected back and forth between the fiber end face and mirror, but at each reflection only a small fraction of the light is transmitted

12. OFPS Advantages • immunity to electromagnetic interference • wide range of potential measured • high resolution • remote sensing capability • high reliability

13. THE END