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relative humidity detection using fiber optics technologies

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relative humidity detection using fiber optics technologies

  2. 2.  Motivation  Introduction to Relative Humidity  Field of research  Sensor design using Fiber Bragg Grating  Humidity Sensor Using Fiber bend technique  Comparative chemical study  Comsol Multiphysics  Optics implementation using Comsol  Simulation Results  Future Scope  References 2 Table of Contents: 2/9/2015
  3. 3. OBJECTIVE / MOTIVATION  Fiber is already used in  90% of long distance telephony (Communication).  Most of the LAN(computer networks) connections.  WHY OPTICAL FIBER ??  Economic  Speed - We transmit signals at Gigabits per second speed.  Very much effective for long distance communications.  Freedom from interference  Security 3 2/9/2015
  4. 4.  What is Relative Humidity ?? - It is nothing but the amount of water vapor present in air expressed as percentage. • MATHEMATICALLY : Relative Humidity = Pw / P*w  A HYGROMETER is a device used for measuring the humidity of air. 4 2/9/2015
  5. 5. Our field of research is : Relative Humidity Sensor using Optical Fiber technologies. 5 Application : Forecasting Applications of Relative Humidity Used as human breath rate monitor in medical fields Structure health monitoring test mostly by using concrete blocks Humidity control in textile application 2/9/2015
  6. 6. FIBER BRAGG GRATING (FBG)… 6 2/9/2015 • Why FBG ??? Several methods to measure RH including resistive, capacitive and hygrometric ones. Drawbacks :  high cost  need for maintenance  inability to use in hazardous and explosive nature environments ( as electromagnetic inference immunity is required). • Optical Fiber Sensors overcomes these disadvantages. • Also has possibility of multiplexing a large number of different sensors (temperature, displacement, pressure, pH value, humidity, high magnetic field and acceleration).
  7. 7. 2/9/2015 7 • Transducer layer used for RH : organo-silica based material. • strong adhesion to the optical fiber that swells in the presence of distinct RH levels. • Di-Ureasil Layer and Sensor Setup… • Di-Ureasil is formed by poly ether chains with average molecular weight of 600mol inv. Covalently linked to a siliceous inorganic skeleton by urea bridges . • It is also can be written as d-U(600). • d-U(600) layers were deposited on FBG using a homemade dip- coating system at room temperature by immersing the FBG vertically in d-U(600) solution at a velocity of 1.4mm per sec. • Then kept in oven and kept at 50 degrees. For 40hrs. As a result the coating reveals a strong adhesion to the optical fiber and mechanical stability. • Then the sensors are identified as
  8. 8. 2/9/2015 8
  9. 9. • The sensors response is temperature dependant due to thermal expansion of fiber and coating . • So it is compulsory the compensation Were encapsulated and being inserted into a stainless steel tube 15cm long with internal diameter of 2mm. • The tube has been punctured in the area of the coated optical fiber to allow the sensitive materials to be exposed to the ambient humidity 2/9/2015 9
  10. 10. FIBER BEND BASED HUMIDITY SENSOR 10 A highly sensitive all fiber humidity sensor is demonstrated Working Principle – Use of hygroscopic material to modulate light Bend radius of 10mm-15mm is taken Advantages -reduces risk of fibre breakage -high sensitivity with greater radius Hygroscopic material – polyethylene Oxide(PEO) Advantages - high range of RI variation wrt humidity - high adhesiveness Benefit of using this method – simple structure and low cost Sensitivity and time response was studied using an experiment as shown… 2/9/2015
  11. 11. EXPERIMENTAL SETUP 11 2/9/2015
  14. 14. Sensor has very fast response as shown above, around 785msec(from 70%-90%) 14 2/9/2015
  15. 15. CHITOSAN & AGAROSE  Chitosan derived from Chitin.  Source of Chitin  Deacetylation of Chitin gives Chitosan and soluble in dilute acidic solutions below pH 6.0  Thin films fabricated from solutions of chitosan and acetic acid have refractive indices approximately 1.45 and there is nearly no absorption (300 to 2700) nm.  Agarose,a polysaccharide obtained from the cell walls of some species of red algae or seaweed.  Agarose, made up of subunits of the sugar galactose. Chemical Comparison 2/9/2015 15
  16. 16. PRINCIPLE : The materials used as the functional cladding layer in the sensing region are Chitosan and Agarose, which swells in the presence of water without dissolving at room temperature. The variation in the refractive index (n) of these swelling polymers with respect to humidity (H) is obtained from Lorenz-Lorenz relation as 2/9/2015 16
  18. 18. COMSOL MULTIPHYSICS SIMULATIONS 18 Engineering simulation software that enables you to create accurate models . Why COMSOL? Conception and Understanding Enables innovation Design and Optimization Achieve the highest possible performance Testing and Verification Virtual testing much faster 2/9/2015
  19. 19. OPTICS IMPLEMENTATION USING COMSOL 19 OBJECTIVE To create a 2-D model to demonstrate the phenomenon of Refraction and total internal reflection and simulate it. MATERIALS USED Air and Glass The model was designed using electromagnetic waves in Frequency domain Boundary conditions were applied on the model as shown in the next slide.. 2/9/2015
  20. 20. glass air 2-D model of Air and glass Applying Boundary conditions Way for EM waves To enter boundary 20 2/9/2015
  21. 21. SIMULATION RESULTS 21 Phenomena of total internal Simulated results after exporting the model Shows variation in wave behavior at different heights(angles) 2/9/2015
  22. 22. Phenomena of refraction 22 2/9/2015
  23. 23. FUTURE SCOPE 23 After a comparative study between different techniques used in humidity sensing, we are to use the best parameters to design a highly efficient sensor. Determine the right hygroscopic material to be used From the simulated model ,we can implement it to demonstrate the effect of light travelling through the core 2/9/2015
  24. 24. REFERENCES 1. Sandra F. H. Correia,Paulo Antunes,Edison Pecoraro,Patricia P. Lima,Humberto Varum,Luis D. Carlos,Rute A. S. Ferreira and Paulo S. Andree,” Optical Fiber Relative Humidity Sensor Based on a FBG with a Di- Ureasil Coating”,June 2012, 2. Jinesh Mathew,Yuliya Semenova,Ginu Rajan, Pengfei Wang, Gerald Farrell ,” Improving the sensitivity of a humidity sensor based on fiber bend coated with a hygroscopic coating ”, April 2011 3. Jinesh Mathew, K. J. Thomas, V. P. N. Nampoori and P. Radhakrishnan,” A Comparative Study of Fiber Optic Humidity Sensors Based on Chitosan and Agarose”, October 2007, 4. Fiber Optic Communications by Joseph C.Palais,4th Edition ,2002 5. 2/9/2015 24