Presentationaaaaaaa OptoElectronics a.pptx

Opto

1. OPTICAL SENSORS Submitted to : Dr. Poonam Syal Professor Deptt of Electrical Engineering NITTTR Chandigarh Presented by : Priya Ranjan (Roll 201513) & Sudipto Poddar (Roll 201516) 3rd Spell M.E Modular Batch 2020- EE Subject: Optoelectronic Instrumentation NITTTR Chandigarh

2. Contents Optical Sensors, Classifications/Types, Temperature Optical Sensor, Water Level Optical Sensor, Pressure Optical Sensor

3. Optical Sensors Electronic detectors that convert light rays into electronic signals. Detect EM radiation in the range- far IR to UV, i.e. λ in range 1mm - 1nm & f in range 3x10 11 Hz to 10 17 Hz Translates different parameters of light, into a form readable by an instrument.

4. Parameters of light being changed by the effect of temperature, pressure, spectrum, wavelength, etc.

5. Operating Principle- Information of measurand impressed onto the light beam in terms of intensity, phase, frequency, polarization, spectrum, etc. Fiber carries the light with the impressed information to a detector, where information is retrieved.

6. Classification of Optical Sensor On the basis of location of sensing element- 2 types- Intrinsic & Extrinsic sensor

7. I ntrinsic Sensor Uses optical fiber to carry the light beam, and the environmental effect impresses information onto the light beam in the fiber. Change takes place within the fiber. Used to measure temperature, pressure, humidity, acceleration, strain, pH, etc.

8. Extrinsic Sensor Optical fiber is simply used to carry light to and from external Transducer / Sensing system. Change takes place outside the fiber. Used to measure vibration, rotation, displacement, velocity, acceleration, torque, temperature, etc.

9. On basis of grating (wavelength modulation)- 4 types- Fiber Bragg Grating, Long Period Grating, Tilted Fiber Bragg Grating & Chirped Fiber Bragg Grating.

10. Fiber Bragg Grating (FBG) Grating is a periodic structure or perturbation in fiber material. Constructed in a short segment of optical fiber by exposing to UV. FBG- Excellent sensor elements, for measuring various parameters.

11. Refractive index of core is modulated periodically. Reflects particular wavelengths of light and transmits all others. Wavelength is given by, λ B = 2n Λ where n is the effective refractive index and Λ is the period of the refractive index modulation.

12. Long Period Fiber Grating (LPFG)- The period of an LPFG is much larger than the wavelength. LPFG are more economical to manufacture. Tilted Fiber Bragg Grating (TFBG) is a new kind of fiber-optic sensor.

13. Chirped Fiber Bragg Grating (CFBG)- The linear variation in the grating period, called a chirp, is used. The reflected wavelength changes with the grating period, broadening the reflected spectrum.

14. On the basis of principle of interference (Phase Modulation)- 4 types- Mach- Zehnder Interferometer, Michelson Interferometer, Fabry -Perot Interferometer, and Sagnac Interferometer.

15. Mach– Zehnder Interferometer Consists of two fiber-to-fiber couplers, separated by two optical fibers. Reference fiber and the Sensing fiber.

16. When a light wave is injected into two fibers, the power is split but the phase remains the same. Constructive interference will occur, giving the maximum intensity output. If the fibers experience different thermal or mechanical strains, destructive interference will occur, causing the output intensity to decrease.

17. Michelson Interferometer Single coupler and fibers with mirrored ends that reflect laser beams, which recombine at the coupler and are directed to the detector. One fiber is reference fiber, other is sensing fiber.

18. It functions much like an Mach- Zehnder Interferometer. Crucial difference is that the light propagating in its two arms is forced to interfere at the same coupler where it was split. It can also be made by using a two-core fiber.

19. Fabry -Perot Interferometer Does not require a reference fiber. Fiber presents two partially reflecting / transmitting mirrors. These mirrors cause the light to travel multiple passes inside the cavity. Magnifies the phase difference, doubling the sensitivity when compared with other interferometer.

20. Sagnac Interferometer Laser sent into a optical fiber coupler from both ends of the same optical fiber in a coiled configuration . Light travel along the fiber in both directions, and both directions become the sensing fibers. Fiber coil is rotated in an axis perpendicular to the coil plane. Light propagation time in one direction less while other path will more ( Sagnac effect). If the coil is kept stationary, light travels the same distance in both directions and no phase shift occurs.

21. It measures rotation with high precision, such as the rotation of the earth around its axis. The sensitivity for rotation measurement depends on the area covered by the coil multiplied by the number of turns.

22. On the basis of operating region of sensing element- Point Sensor & Distributed Sensor

23. In Point Sensor type, transducers are placed at the end of optical fiber. Both intrinsic & extrinsic can work as point type. In Distributed Sensor type, sensor operates over distribution of points i.e. sensor is a long series of sensors. Only intrinsic can work as distributed type.

24. Applications Following are the applications of optical sensors: Used in remote sensing satellite. Used in imaging, Quality and Process Control applications, Medical instruments, Airspace, Civil and Oil industry, Environment monitoring, Biochemical analyses, Gas leak or other monitoring in hazardous environments

25. Advantages Immune to electro-magnetic interference and hence ideal to be employed in microwave environment. Very high sensitivity, range and resolution compared to non optical sensors. Wider dynamic range. Completely passive and hence used in explosive environment. Small in size and light in weight. Contd.

26. Resistant to high temperatures and chemically reactive environment. Hence ideal for harsh environment. Used to monitor wide range of physical as well as chemical parameters. Provides complete electrical insulation from high electrostatic potential. Multiplexed/distributed sensors provide measurements at large number of distributed points.

27. Disadvantages Interference from multiple effects. Sensor used for pressure/strain measurement is very sensitive to temperature variation. Different types of losses involved in optical domain. Absorption loss, scattering loss, coupler loss, insertion loss, reflection loss, impurity loss etc.

28. Fiber-Optic Temperature Sensors Based on the light absorption/ transmission properties of Gallium Arsenide ( GaAs ). The effects of temperature variations on the crystal are well known and predictable. GaAs crystal is placed at the measurement end of the fiber-optic temperature sensor.

29. As the crystal’s temperature increases, its transmission spectrum (i.e., the light that is not absorbed) shifts to higher wavelengths. Transmission jumps from 0% to 100% at a specific wavelength called the absorption shift. The relationship between the temperature and the specific wavelength at which the absorption shift takes place is very predictable.

30. The three temperatures shown here are in ºC.

31. Applications Motors– ensure the motor itself does not overheat. Home Appliances– kettles, toasters, washing machines, dishwashers and coffee machines, all contain temperature sensors. Computers– temperature sensors to ensure the system does not overheat. Industrial Equipment– temperature sensors used within these applications will need to be robust. Warming Electrical Radiators– used to control the heat on electric radiators. Exhaust Gas Monitoring on Vehicles– vehicle temperature sensors need to be highly reliable and durable to ensure performance is not compromised in this harsh environment. 3D Printed Chocolates –used to monitor the temperature of the melted chocolate for 3D printing.

32. Advantages Immunity from nearby EM (electromagnetic) and stray radiation. Used where safety is a concern. Offers greater accuracy (+/- 1 o ) and faster response time (~2 sec). Light in weight and compact in size. Cheaper due to low manufacturing cost. Supports wide temperature range of measurement from -10  o C to 300  o C. GaAs offers better wavelength variation with temperature.

33. Disadvantages Different types of optical temperature sensors will have different temperature range of operation and their accuracy of measurements also vary. Also, it depends on their construction and materials used. Complex to develop measurement systems using fiber optic sensors. Users require training before they start using such sensors. Some fiber optic temperature sensors are expensive.

34. Optical Liquid Level Sensor Uses an infra-red LED and phototransistor accurately positioned at the base of the sensor’s tip. When the tip is in air, infra-red light reflects internally round the tip to the phototransistor providing good optical coupling between the two. When the sensor’s tip is immersed in liquid, the infra-red light escapes from the tip causing a change in the amount of light at the phototransistor which changes the output.

35. Applications Tank level measurement Used for leak detection Used to detect the level of liquids with suspended solids

36. Advantages Compact No moving parts Used for high temperature and pressure applications Can detect less amount of liquid Immune to electromagnetic interference Used in an explosive environment Used for high and low intermediate level detection in large and small tanks

37. Disadvantages The probe could erode during time.  It can only determine if liquid is present or not present.  If variable levels are required, (e.g. 25%, 50%, 100%, etc.) each requires an additional sensor. They are invasive and it is because the sensor is in contact with the process liquid. Reading could take time due to bubbles, coating, or tanks that are mirrored.

38. Optical Pressure Sensors Detect a change in pressure through an effect on light. It is a mechanical system that blocks the light as the pressure increases. Also, the measurement of phase difference allows very accurate measurement of small pressure changes.

39. Increase in pressure cause the source of light to be progressively blocked. The sensor then measures the change in light received. Pressure moves diaphragm and the attached opaque vane blocks light from the LED. Fall in light intensity detected by photodiode and gives measurement of pressure. It also needs a reference photodiode, which is never blocked by the vane. A fiber is sandwiched between a pair of toothed plates to induce micro bending. When pressure is applied to these toothed pairs, there is a change in the power at output end. Other fiber-optic sensors use interferometry to measure changes in the path length and phase of light caused by changing pressure.

40. Very sensitive optical measurements can be done by using interferometry, measuring the change of phase between light that has taken two different paths. There are two common types of pressure sensor that use interferometry. These are the Fabry -Perot interferometer (FPI) and Fiber Bragg grating (FBG). FPI is one of the best optical sensor technologies. It is simple, accurate and easily scaled for different sizes and pressure ranges. An FBG is an intrinsic sensor that has a regular series of reflective structures in the fiber that are affected by stretching or squashing the fiber. This causes the wavelengths of the reflected light to change.

41. Applications Very useful in harsh environments. Oil and gas industry. Conditions in a oil well can easily reach 20 KPsi and 185º C. Optical sensors continue to perform well under these extremes. Sensors are made of non-toxic materials makes them very well suited to medical applications. There are many places in the body where measuring pressure can be important for diagnosis, long-term monitoring or during treatment. The immunity to EM interference is valuable when pressure needs to be monitored during MRI scans. A Fabry -Perot sensor can be used to accurately monitor pressure at a specific location in the body and is typically introduced via a catheter. Bottle and equipment leak detection, Air blades, compressed air pressure monitoring, industrial flow monitoring, filter pressure monitoring, duct air flow, gas detection, pneumatic controls, mine safety instrumentation, suction check in pick and place applications such as the printed circuit boards and semiconductor process equipment.

42. Advantages The small size and flexibility of fiber-optic sensors means they can be deployed in locations that would be hard to access with other techniques. Because the amount of movement needed is very small, hysteresis and repeatability errors are very low. The fact that the sensing element itself is passive and does not need a power supply enables the sensors to be used in a wide range of applications where getting power to the sensor could be a problem. This also eliminates signal transmission problems due to parasitic capacitance, electromagnetic interference, etc.

43. Disadvantages Intensity based sensors are not very sensitive to temperature change because the measurement and reference detectors are affected equally. On the other hand, their small size can mean they are not as robust as other sensor types. Their high sensitivity can also make them more sensitive to acoustic or mechanical vibration.

44. Topic: A Magnetically Controlled Wireless Optical Oxygen Sensor for Intraocular Measurements Name of Researchers: Olgac Ergeneman , Student Member, IEEE, Gorkem Dogangil , Student Member, IEEE, Michael P. Kummer , Student Member, IEEE, Jake J. Abbott, Member, IEEE, Mohammad K. Nazeeruddin , and Bradley J. Nelson, Senior Member, IEEE. Research Paper

45. Abstract The influence of oxygen on various eye diseases is not completely understood and intraocular oxygen measurements are essential for better diagnosis and treatment. A magnetically controlled wireless sensor device is proposed for minimally invasive intraocular oxygen concentration measurements. This device will make it possible to make measurements at locations that are currently too invasive for human intervention by integrating a luminescence optical sensor and a magnetic steering system. The sensor works based on quenching of luminescence in the presence of oxygen. Results of the oxygen sensor together with magnetic and hydrodynamic characterization of the sensor platform are presented to demonstrate the concept. In order to use this sensor for intraocular applications, the size of the sensor must be reduced, which will require an improved signal-to-noise ratio.

46. Thank You