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FACULTYOF ENGINEERING
LABREPORT SUBMISSION COVERPAGE
ETN4106 OPTOELECTRONICS AND OPTICAL COMMUNICATIONS
TRIMESTER1,SESSION2017/2018
Student Name:Student ID:
Degree Major (please circle): / EE /LE / CE / TE / ME / OPE / MCE / NT
Declarationoforiginality:
Ideclarethat allsentences, results anddata mentioned in this report are from myown
work. All works derived from other authors havebeenlisted in the references.
Iunderstand that failureto do this is considered plagiarismandwillbepenalized.
Notethatcollaboration and discussions in conducting the experiments areallowed but copying and anyact of cheating in thereport, results and data arestrictlyprohibited
Student signature:
Experiment title: / OOC1 – FIBER LINK CHARACTERIZATION WITH OTDR
Experiment Date:
Table/PC No.:
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(Please get your lab instructor signature after they have verified your results)
FACULTY OF ENGINEERING
LAB SHEET
ETN4106 OPTOELECTRONICS AND OPTICAL COMMUNICATIONS
TRIMESTER 1 (2017/2018)
OOC1 – FIBER LINK CHARACTERIZATION WITH OTDR
*Note: On-the-spot evaluation is carried out during or at the end of the experiment. Students are advised to read through this lab sheet before doing experiment. Your performance, teamwork effort, and learning attitude will count towards the marks. At the end of the experiment, student must submit their individual lab report and the rubrics form to the lab technician.
OOC1 –Fiber Link Characterization with an OTDR
Objectives:
1.To determine the fiber's length and overall attenuation, including splices and connectors losses.
2.To demonstrate ghost and determine the real length of the fiber cable.
3.To locate faults, such as breaks, and to measure optical return loss.
Equipment:
1.JDSU MTS-6000 Compact Optical Modular Platform
2.Small single mode fiber optic cable reels have the following specification:
●Length: 2.2 km
●Att.1310nm: 0.34 dB/km.
●Att.1550nm: 0.19 dB/km.
3.9/125/250 UM single mode simplex PC/B01020036005/SP1 (Launcher cable with FC connectors)
4.FC adapters.
Theory:
An optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. An OTDR injects a series of optical pulses into the fiber under test. It also extracts, from the same end of the fiber, light that is scattered and reflected back from points in the fiber where the index of refraction changes. (This is equivalent to the way that an electronic time-domain reflectometer measures reflections caused by changes in the impedance of the cable under test.) The strength of the return pulses is measured and integrated as a function of time, and is plotted as a function of fiber length.
An OTDR may be used for estimating the fiber's length and overall attenuation, including splice and mated-connector losses. It may also be used to locate faults, such as breaks, and to measure optical return loss. In addition to required specialized optics and electronics, OTDRs have significant computing ability and a graphical display, so they may provide significant test automation. However, proper instrument operation and interpretation of an OTDR trace still requires special technical training and experience.
OTDRs are commonly used to characterize the loss and length of fibers as they go from initial manufacture, through to cabling, warehousing while wound on a drum, installation and then splicing. The last application of installation testing is more challenging, since this can be over extremely long distances, or multiple splices spaced at short distances, or fibers with different optical characteristics joined together. OTDR test results are often carefully stored in case of later fiber failure or warranty claims. Fiber failures can be very expensive, both in terms of the direct cost of repair, and consequential loss of service.
OTDRs are also commonly used for fault finding on installed systems. In this case, reference to the installation OTDR trace is very useful, to determine where changes have occurred. Use of an OTDR for fault finding may require an experienced operator who is able to correctly judge the appropriate instrument settings to locate a problem accurately. This is particularly so in cases involving long distance, closely spaced splices or connectors.
Ghosts:
If you are testing short cables with highly reflective connectors, you will likely encounter "ghosts" like in Figure 1. These are caused by the reflected light from the far end connector reflecting back and forth in the fiber until it is attenuated to the noise level. Ghosts are very confusing, as they seem to be real reflective events like connectors, but will not show any loss. If you find a reflective event in the trace at a point where there is not supposed to be any connection, but the connection from the launch cable to the cable under test is highly reflective, look for ghosts at multiples of the length of the launch cable or the first cable you test. You can eliminate ghosts by reducing the reflections.
Figure 1.OTDR "Ghost"
On very short cables, multiple reflections can be confusing. A cable that was tested with an OTDR can be deemed bad because it was broken in the middle. In fact it was very short and the ghosted image made it look like a cable with a break in the middle. The tester had not looked at the distance scale or he would have noted the "break" was at 40 meters and the cable was only 40 meters long. The ghost at 80 meters looked like the end of the cable to him.
Experimental Methodology:
Use the highly integrated platform MTS-6000 with single module slot and an intuitive graphical user interface (GUI) shown on a large 8.4 inch transreflectivecolour display (with an optional touch screen) to improve viewing under any condition. Then, connect the equipments as it appears in Figure 2 below, and continue with the following experimental procedure.
Figure 2. Using MTS-6000 OTDR to locate faults or breaks
Figure 3. MTS-6000 ports
Figure 4. Controls of the interface module
Experimental Procedure:
A.Determining and comparing fibre attenuations at different wavelengths
1.Connect one reel of optical fibre (reel A) to the plug in module of the ODTR as shown in Figure 2.
2.Press the On/Off key as shown in Figure 4.
3.Press the Setup key as shown in Figure 4.
4.On the Acquisition menu, select Mode and click on Auto. For Laser, click on All.
5.Press Start/Stop key to start the laser.
6. The result of the measurement will appear in the Results page.
B.Identifying ghost
- Ghost will be shown in the result of the measurement obtained in part A.
C.Determining the lengths and attenuations of cascaded fibres
1.Using an FC connector, connect reel A in part A to another reel of optical fibre (reel B).
2.Press the Setup key as shown in Figure 4.
3.On the Acquisition menu, select Mode and click on Auto. For Laser, click on 1550 nm.
4.Press Start/Stop key to start the laser.
5. The result of the measurement will appear in the Results page.
D.Locating breaks and measuring total loss
1.Using reels A and B from part C, press the Setup key as shown in Figure 4.
2.On the Acquisition menu, select Mode and click on Fault Locator. For Laser, click on 1550 nm.
3.Press Start/Stop key to start the laser.
4. The result of the measurement will appear in the Results page.
Name: / StudentID:Date: / LabGroup: / Table No.
Major (please circle):EE/CE/MCE/ME/TE/OPE/NT
Results and Discussion:
Part A(Cognitive – Analysis, Level 4)
(6 marks: The marks will be converted to 4 marks under rubric criteria 2)
1.(a) Sketch separately the plots of loss (dB) against length (km) for both wavelengths 1310 nm and 1550 nm. In your plots,
(i) show the value of the slope [1 mark], and
(ii) write the distance of all the pulses detected on the x-axis [2 marks].
(b)What are the attenuations of the fibre at 1310 nm and 1550 nm? [1 mark]
(c)Compare the attenuation of the fibre at 1310 nm and 1550 nm [1 mark].
(d) If the attenuation is due to Rayleigh scattering, explain your answerin 1(c) above [1 mark].
Part B (Cognitive – Evaluation, Level 6)
(4 marks: The marks will be converted to 4 marks under rubric criteria 3)
2.(a)Explain using your own words what you understand by ghost [1 mark].
(b) Identify the ghost in your plots in 1(a) above by labelling the ghost . [1 mark]
(c) Explain how you know that the pulse(s) in 2(b) is/are ghost(s) [1 mark].
(d)Explain how ghost can mislead an OTDR user [1 mark].
Part C(Cognitive – Analysis, Level 4)
(5 marks: The marks will be converted to 4 marks under rubric criteria 4)
3.(a) Sketch the plot of loss (dB) against length (km) for wavelength 1550 nm. In your plot,
(i) show the values of the two slopes [1 mark], and
(ii) write the distance of all the pulses detected on the x-axis [1.5 marks].
(b) Compare your plot in 3(a) with the plot in 1(a) for wavelength 1550 nm. Explain whythere is an additional pulse(this does not refer to the ghost) in the 3(a) plot [1 mark].
(c) What are the lengths of reel A and reel B, and the total length of both reels [1.5 marks]?
Part D(Cognitive – Evaluation, Level 6)
(9 marks: The marks will be converted to 4 marks under rubric criteria 5)
4.(a) What are the total fibre length and total loss as shown by the Fault Locator[1 mark]?
(b)Using the measurement of 3(a)(i) and 3(c), calculate the fibre loss due to its attenuation (in dB) for reels A and B [2 marks].
(c)Using the total loss in 4(a) and the calculated fibre attenuations in 4(b), estimate the loss due to the FC connector between reels A and B [1 mark].
(d) Reels C, D, E, and F are of lengths 2 km, 3 km, 4 km, and 5 km respectively. The four optical fibre reels are connected successively using FC connectors but reels E and F are not connected properly and results in a break. The function Fault Locator is used with wavelength 1550 nm.
(i)Sketch the plot of loss (dB) against length (km) that will be shown by the Fault Locator.Show all the pulses and their distance. [You can omit the ghost.] [1.5 marks]
(ii)What will be the total fibrelength shown by the Fault Locator [0.5 marks] ?
(iii)If each FC connector has a loss of 0.3 dB, and the fibre attenuation at 1550 nm is the same as in 1(b) above, what will be the total loss shown by the Fault Locator [3 marks]?
Conclusion: (Cognitive – Evaluation, Level 6)
(7 marks: The marks will be converted to 4 marks under rubric criteria 6)
1.Which transmission window is a better choice in terms of fibre attenuation, the second or the third window? Why? [2 marks]
2.Give two disadvantages of the OTDR you use in this experiment [2 marks].
3.List three uses of OTDR related to this experiment [3 marks].