1. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
ECE-641 FIBER OPTICS AND OPTICAL COMMUNICATIONS WINTER CLASS PROJECT COMPARATIVE STUDY ON CWDM AND DWDM PRESENTER: FREDRICK KETANGENYI INSTRUCTOR: DR. TIM KURZWEIG
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

2. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
PRESENTATION OUTLINE
1: OVERVIEW
2: MEANING OF WDM.
3: IMPLEMENTATION OF DWDM.
4: IMPLEMENTATION OF CWDM.
5: DIFFERENCES BETWEEN CWDM AND DWDM.
6: CONCLUSION.
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

3. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
1: PAPER OVERVIEW THIS PAPER BRINGS TO LIGHT ONE OF THE MANY METHODS AVAILABLE IN THE QUEST TO PUSH MORE DATA THROUGH EXISTING SIGNAL TRANSMISSION LINES. THIS IS WAVELENGTH DIVISION MULTIPLEXING - WDM, WHICH IN ESSENCE IS ANALOGOUS TO FDM(frequency division multiplexing) SINCE EVERY FREQUENCY CORRESPONDS TO A DIFFERENT WAVELENGTH. DISCUSSION IS ON THE CHARACTERISTICS OF DWDM AND CWDM, WHICH HAVE BEEN DERIVED FROM WDM , AND FACTORS BEHIND THEIR DIFFERENT APPLICATIONS IN OPTICAL NETWORKS.
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

4. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
2: WHAT IS WDM ?
IT IS A MULTIPLEXING TECHNIQUE THAT ENABLES MANY OPTICAL SIGNALS, EACH OF DEFFERENT WAVELENGTH TO PROPAGATE DOWN A SINGLE FIBER.
WDM OVERLAYS SIGNALS ONTO A SINGLE MODE FIBER OPERATING ON WAVELENGTH CENTERED AT 1550nm. THE WAVELENGTHS ARE WIDE SPREAD WITH 2 TO 16 CHANNELS IN NORMAL DEPLOYMENTS. DISTANCE IS LIMITED TO 100km.
FILTERS ARE USED IN MULTIPLEXING(add) AND DEMULTIPLEXING(drop) OF OPTICAL SIGNALS.
FIGURE-1 BELOW IS A SCHEMATIC OF A BASIC WDM SYSTEM WITH .
Fig.-1
Wavelength Multiplexing by a filter.
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

5. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
2-1: COMPONENTS OF WDM
A BASIC WDM SYSTEM CONSISTS OF THE FOLLOWING COMPONENTS:
i) AN OPTICAL LASER(transmitter) .
ii) AN OPTICAL DETECTOR(receiver)
iii) OPTICAL FILTERS FOR MULTIPLEXING(add) AND DEMULTIPLEXING(drop)-OADM.
iv) OPTICAL AMPLIFIER FOR DISTANCE EXTENSION.
OPTICAL LASER AND OPTICAL DETECTOR ARE INTEGRATED INTO ONE TRANSCEIVER, THUS OPERATING AT THE SAME WAVELENGTH.
FIGURE-2 SHOWS THE COMPONENTS OF A WDM SYSTEM.
Fig.-2 : A WDM system.
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

6. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
3 : IMPLEMENTATION OF WDM BY DWDM
DENSE-WDM IS THE SUMPERIMPOSITION ON A SINGLE FIBER, OF MANY OPTICAL SIGNALS A DIFFERENT WAVELENGTHS(lambda), CLOSELY SPACED AT 0.8nm - 2nm.
DWDM DELIVERS DATA RATES OF UP TO 10Gbps(OC-192) OVER A FIBER, WITH CURRENT SYTEMS SUPPORTING OVER 128lambdas. WINDOW OF OPERATION IS BETWEEN 1530nm and 1560nm,
COOLED LASERS ARE USED IN ORDER TO PREVENT WAVELENGTH DRIFTS THAT WOULD EVENTUALLY CAUSE INTERFERENCE AMONG THE DENSELY PACKED WAVELENGTHS.
A NON-ZERO DISPERSION SHIFTED FIBER CENTERED AT 1545nm IS USED AND OPTICAL AMPLIFIERS AND REGENERATORS ARE USED ALONG THE ROUTE.
DWDM IS STANDARDISED BY ITU-T RECOMMENDATION G FOR USE IN LONG HAUL TRANSMISSION.
Figure-3 on the right depicts a pair of mux/demux with ILAs between the two ends.
Fig.-3
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

7. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
4 : IMPLEMENTATION OF WDM BY CWDM
IN COURSE-WDM THE WAVELENGTHS ARE SPACED FARTHER APART WITH CHANNEL SEPARATIONS OF 20nm BEING DEPLOYED.
UNCOOLED LASERS ARE USED AS SOURCE , THUS ALLOWING WAVELENGTHS TO DRIFT WITHOUT FEAR OF INTERFERENCE. THE WIDE CHANNEL SEPARATION PROVIDES THE LAXITY.
THE WAVELENGTH WINDOW IS EXTENDED TO BETWEEN 1270nm and 1610nm.
DATA RATES OF UP TO 2.5Gps WITH A TRANSMISSION DISTANCE LIMITED TO ABOUT 31km. 18 DIFFERENT CHANNELS ARE SUPPORTED BY CWDM.
CWDM IS REGULATED BY ITU-T RECOMMENDATION G
Figure-4 on the left shows an
8 channel CWDM system
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

8. 5: DIFFERENCE BETWEEN CWDM AND DWDM CWDM DWDM
USES UNCOOLED LASERS FOR SIGNAL LAUNCH.
PACKS LESS WAVELENGTHS, CURRENTLY UP TO 32.
MOSTLY PASSIVE COMPONENTS ARE EMPLOYED, LIMITING ITS APPLICATION TO ETHERNET- WANs.
DATA RATES ARE LOWER, UP TO 2.5Gbps(OC-48).
WIDER WINDOW OF OPERATION, 1270nm TO 1610nm.
USES THERMALLY CONTROLED(cooled) LASERS FOR SIGNAL LAUNCH.
PACKS MORE WAVELENGTHS PER FIBER TRANSMISSION CHANNEL, UP TO 128.
ACTIVE COMPONENTS ARE USED, THUS CAN EXTEND DISTANCE FOR LONG HAUL TRANSMISSION.
DATA RATES ARE COMPARABLY HIGHER TO THE ORDER OF 10Gbps(OC-192)
WINDOW OF OPERATION IS BETWEEN 1530nm AND 1560nm.
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM

9. ECE 641 PROJECT: STUDY ON CWDM AND DWDM
6: CONCLUSION
BOTH CWDM AND DWDM DELIVER MORE DATA RATE THAN THE BASIC WDM.
HOWEVER, THESE TWO TECHIQUES HAVE DIFFERENT APPLICATIONS IN THE OPTICAL NETWORK, MAINLY DUE TO THEIR DIFFERENCE IN IMPLEMENTATION.
THE DWDM IS PREFERRED FOR LONG HAUL TRANSMISSION SYSTEMS WHERE AS CWDM IS MOSTLY PREFERRED FOR MAN/WAN IMPLEMENTATIONS.
THE REASONS FOR THIS CLASSIFICATION IS BASED ON TWO REASONS:
i) ECONOMIC AND BUDGETARY- IT IS NOT FEASIBLE TO DEPLOY CWDM FOR LONG HAUL SINCE THIS WILL REQUIRE LOTS OF ACTIVE COMPONENTS ALONG THE WAY JUST TO DELIVER A FEW NUMBER OF CHANNELS. ALSO UNCOOLED FIBER IS CHEAPER COMPARED TO THERMAL CONTROLED FIBER USED FOR DWDM. ON THE OTHER HAND, IT IS OF FEASIBLE TO DEPLOY DWDM FOE LAONG HAUL.
ii) IMPELEMENTATION/TECHNOLOGY - THE USE OF UNCOOLED LASERS MAKES CWDM IMPOSSIBLE FOR LONG HAUL SINCE THE WIDE SEPARATION BETWEEN THE SIGNALS WILL EVENTUALLY CAUSE INTERFERENCE.
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ECE 641 PROJECT: STUDY ON CWDM AND DWDM