Introduction to Fiber Optics Systems
Apparatus
Two light sources
A rail
VARIAC
DC voltage source
Three lenses
Filter
Four multimeters
Stands
Introduction
The optical pyrometers have been in existence for more than hundred years in use. Its basic function is to determine the temperature of a hot and glowing body by the virtue of matching its brightness to a calibrated light bulb. The human eye is used to match the brightness of the glowing bodies. The setup in figure 1 below shows the optical arrangement pyrometers.
Figure 1: Optical pyrometer (DeCusatis and DeCusatis, 10)
In this arrangement, the light intensity from the reference bulb 1 is regulated by varying the voltage V1 from 20 v which is dim to brightness to v1 = 120v, full brightness. There is a second bulb2 that is placed between the observer and the bulb 1. The bulb 2 is the object who temperature T2 is to be determined and therefore, its brightness can be regulated by changing the voltage v2 which in turn changes the current I2. If the temperature of bulb2 is higher than that of bulb 1, then the filament of bulb 2 will appear brighter on a dark background. For T2<T1, the filament of bulb 2 will appear to be dark on a darker background. When both temperatures are similar, filament in bulb 2 will become nearly invisible, dim from the background. The situation would be established from for twenty varied values of brightness for bulb 1. The bulb 1’s filament temperature can be approximated by equation 1 below
T1= I12RxδεA1/4 1 (Huang, 36)
Where σ is the Boltzmann constant is = 5.67 x 10-8 W. m-2. K-4
ε = emissivity of filament in bulb 1
A = is the light emitting surface area of the filament in bulb 1 and is equivalent to 8 x 10-5 M2
Rx is obtained from the relationship in equation 2 shown
Rx = V1/I1 .. 2
Safety and Care Notes
The light should not be touched since they may get too hot. Secondly, all the room lights should be put off to allow the acquisition of the sharpest image when viewing. As a rule, in the laboratory one should ask a question about something in case of any doubt.
Procedure
Getting familiar with the equipment used.
The setup for all the different components should be checked and one should make to understand all the VARIAC and DC voltage source connections, settings and operations. All the connections to the multimeter should be checked to ensure identification of the type of reading that is obtained from each one of them.
Procedure of Measurement
The following procedure is repeated for the voltage V1 from 20V to 110v in an interval of 5v each. Firstly, the voltage v1 on the VARIAC is set by measuring the voltage with the multimeter. The reading of the current, I1 is then taken and the Voltage v2 is adjusted until the filament in bulb 2 disappears in the background that is created by the light of bulb 1. This is followed by taking the readings of v1 and v2. After repeating the above procedure above for different values of v1, the equipment is turned off.
Results
Discussion
Calculation of Rx
= v1/I1 =
Calculation of T1
T1= I12RxδεA1/4
T1= I12Rx10135.67 x 8 1/4
A graph of I2 versus T1 is plotted as shown below
The graph above shows some variation in the form of a sinusoid wave. This is because of the variation of light intensity and the temperature. As the current increases, the temperature also increases but non-uniformly. This variation shows the difference between the temperature of the filament of bulb1 and the current supplied to bulb 2 (Kerr and Ivey, 24)
Sources of errors
The equipment used in measurements such as voltmeters and multimeters could be faulty, and this brings the unnecessary variation or inconsistency in the values. The other error could be through the incorrect taking of the readings. The unfamiliarity with the equipment is also a challenge that can cause errors due to blunders when carrying out the experiment.
Remedy to Errors
The same errors described above could be mitigated by ensuring that the equipment used in the measurement is in good working condition. This removes the unexpected zero errors. Ne should ensure proper familiarization with the equipment to do the experiment without making any blunders by following the procedure carefully. Another way of improving the results is through the frequent performance of the same experiment to gain confidence and acquire more accurate values.
Conclusion
The experiment was done by carefully following the outlined procedure to obtain the results plotted. The curve plotted shows some consistency in the values got from the experiment despite some deviations. The source of the little difference could be through faulty equipment used, carelessness in procedure and common mistakes. The same can be corrected by using some reliable accurate equipment, studying of equipment and steps widely and frequent experiment on same. Despite all the above, the aim of the experiment was achieved.
Work Cited
Kerr, Clive I., and Paul C. Ivey. "A Review of Purge Air Designs for Aeroengine-Based Optical Pyrometers". J. Turbomach. 124.2 (2002): 227. Web.
Kazovsky, Leonid. "Optical Fiber Communication Systems". Optical Engineering 36.11 (1997): 3223. Web.
Huang, Dexiu. "Fiber Optic Surface Plasmon Resonance Sensors for Imaging Systems". Optical Engineering 46.5 (2007): 054403. Web.
DeCusatis, Casimer, and Carolyn J. Sher DeCusatis. Fiber Optic Essentials. Amsterdam: Elsevier/Academic Press, 2006. Print.
Mitschke, F. Fiber Optics. Berlin: Springer, 2009. Print.
