Erbium Doped Fiber Amplifier (EDFA) for C-Band Optical Communication System

International Journal of Engineering & Technology IJET-IJENS Vol:12 No:04 48

1214104-8383-IJET-IJENS © August 2012 IJENS I J E N S

Erbium Doped Fiber Amplifier (EDFA)

for C-Band Optical Communication System

M.A.Othman , M.M. Ismail , M.H.Misran ,M.A.M.Said and H.A.Sulaiman

Abstract— One distinct feature of an optical fiber is that there

is a wide spectral region where signals are transmitted in

optical fiber. Since most light sources used in high-capacity

optical communication systems emit narrow wavelength or lessthan 1nm, whilst most full-spectrum fibers for communication

application operates in C-band. Thus, the paper reviews the

technology of optical amplifier in telecommunication network

applications. The main scope of this paper is to implementErbium Doped Fiber Amplifier (EDFA) in the range of C-band.

The gain and noise figure at each changes of both length and

pump power are observed, simulated by using OptiSystem

software. The EDFA optical amplifier is inserted in theWavelength Division Multiplexing (WDM) system to trigger in

various inputs at different wavelength in the range between

1538 to 1565nm.

Index Term-- component; EDFA, WDM, fiber length, pump

power, gain, noise figure.

M.A.Othman is serving in

Centre for Telecommunication Research and Innovation

Fakulti Kej. Elektronik dan Kej. Komputer

Universiti Teknikal Malaysia Melaka

76100 Durian Tunggal, Melaka, Malaysia

[email protected]

M.M. Ismail is serving in

Centre for Telecommunication Research and Innovation

Fakulti Kej. Elektronik dan Kej. KomputerUniversiti Teknikal Malaysia Melaka


[email protected]

M.H.Misran is serving in

Centre for Telecommunication Research and InnovationFakulti Kej. Elektronik dan Kej. Komputer


76100 Durian Tunggal, Melaka, [email protected]

M.A.M.Said is serving in

Centre for Telecommunication Research and InnovationFakulti Kej. Elektronik dan Kej. Komputer



[email protected]

H.A.Sulaiman is serving inCentre for Telecommunication Research and Innovation

Fakulti Kej. Elektronik dan Kej. Komputer


76100 Durian Tunggal, Melaka, [email protected]

I. I NTRODUCTION

Optical amplifiers have been essential elements for highcapacity, long-lifespan and multiple connection of optical forcommunication network applications, since it compensatesloss through transmission of information via transmissionmedium, the passive components and the power division forconnectivity of multiple points[1]. WDM is basically a fiberoptical transmission technique, which multiplexes manysignals of different wavelength and is capable of providingdata capacity in excess of hundreds of gigabit per second overthousands of kilometers in a single mode fiber. At the present,most countries in the world have implemented Internetinfrastructure by means of WDM systems to provide high

bandwidth and a high-speed Internetservice.

Optical amplifiers applies in general application such as in-line optical amplifiers, preamplifier and power or boosteramplifier, plus devotes its crucial applications to carryinformation at long distances of more than 100 km, which has

been an important criteria for telecommunication application.

Today, most optical amplifiers have presented advancedcomplex systems and reduce usage of repeaters to couple onefiber cable to another in order to reduce loss in transmission,despite the earlier version introduce simpler andstraightforward system. All optical amplifiers functions toincrease the power level of incident light through a stimulatedemission or optical power transfer process[2]. Theseamplifiers are widely used in WDM networks with largerchannel numbers, which requires higher total pump power.The optical pumps usually are of semiconductor laser atoutput range of 20 – 33 dBm, in which, might expose tohazards such as eye and skin damage risks and possibility offiber explosion in case the beam are excessive and spreadthrough edges of fiber, thus lead to fiber fuse effect as well.The other challenge that might be faced by the optical systemdesign is the noise generation of amplifiers, not only that; ithas to deal with non-linear optical cross-talk in transmissionfibers [3].

Optical amplifiers mostly help in extending power budget,thus reduces number of connectivity points. Opticalamplifiers also are designed to lessen the effects of dispersionand attenuation, which allows improved performance forlong-haul optical systems. The amplifier system also replacesthe old technology of electronic regeneration systems throughconversion from electrical to optical(E – O) and conversion ofoptical to electrical(O – E) to carry information for longdistance communication.

This paper project shows several differences in gain and noisefigure in different pump power in milliwatt. Two transmitter



points provides 32 ports, with variety of wavelength at rangeof 1538nm until 1565nm. This paper also analyzes thesuitable fiber length in EDFA and the pump power to use inthe designed WDM system. The distinct difference alsodetermines the most suitable photodetectors to be used at thereceiver point of the optical amplifier circuit.

II. METHOD A NALYSIS

The software Optisystem is used as a simulation tool tosimulate the design for EDFA in the WDM system. Thesystem consists of two input transmitter (16-channel WDMtransmitter each),ideal multiplexer, two isolators, a pumplaser, erbium doped fiber, demultiplexer, two photodetectorPIN filter, two photodector APD, optical power meter, opticalspectrum analyzer, low pass Bessel and 3R regenerator . Thechannel of WDM transmitter technique using non-return tozero (NRZ) modulation format will be constructed.

The two input of the system is 16 equalized wavelengthmultiplexed signals in the wavelength region of12nm(1538nm-1550nm) and 15nm(1550nm-1565nm) withfrequency spacing is 0.8nm and 1nm. The power of eachchannel is -26dBm. The optical isolator is also used toachieve stable amplifier operation, which functioned to

blocks the reflected light into the amplifier. In order to pumpthe erbium ions up to an upper energy level, there are several

proper pump wavelength bands. So, the pumping at 980nm isused to excite the doped atoms to a higher energy level.Otherwise, reflected ASE would reduce the populationinversion, hence reducing the gain and increasing the noisefigure. The output isolator prevents light from outputreflections re-entering in the EDFA.

The receivers generally consist of a photodetector APD, photodetectorPIN, low pass Bessel filter and BER analyzer.The photodetector convert the optical signals to electronicsignals which a processed to extract information. Thecharacteristic of a photodetector is low noise preamplifier andother associated circuitry. Two photodetectors use are PIN

photodiodes and avalanche photodiodes(APDs).Photodetector PIN performs conversion from opticalto electrical domain. An avalanche photodiode (APD) is set tocapture the signal with the highest level. Low Pass BesselFilter is limits the noise power. Besides, BER Analyzer is auniversal visualization component for performance indicators,which analyzed and show the BER, Q-Factor, Eye Height andthe threshold. Finally, the system is connected and simulated.

III. R ESULTS AND DISCUSSIONS

The pump power is varied to measure the output power for

the different fiber length at a constant input power of -

26dBm. The result is shown in Figure 1. It is observed thatwhen the pump power increased, the output power increased

as well. The optimum value of the fiber length is found to be

7m. The fiber length of 7m is set as the reference length. Inorder to find the suitable value of pump power, the gain and

noise figure (NF) for the multichannel amplification is

investigated at different pump powers. Figure 2 show the

gain variation of each channel for different pump powers at a

constant input power of -26dBm, whereas Figure 3 show the NF variation of each channel for different pump powers at a

constant input power of -26dBm. The gain is directly

proportional to the pump power whereas the NF is inversely proportional to the pump power. As the pump power

increases, the gain increases. But, the NF decreases as the

pump power increases. The pump power of 50mW has low

gain and higher NF, which show that it does not offer good

performance for the system. By comparing Figure 3 and

Figure 4, pump power of 250mW is chosen due to its highgain and low NF. Figure 5 show the bit error rate (BER)

pattern at channel 14 in the first WDM transmitter forAPD

with shot noise, APD without shot noise, PIN with shot noiseand PIN without shot noise.

Fig. 1. Variation of output power along the fiber length for different pump

power at a constant input power.

Fig. 2. Gain variation of -26dBm per channel amplification for different pump powers.

Fig. 3. NF variation of -26dBm per channel for different pump powers.



APD with shot noise APD without shot noise

PIN with shot noise PIN without shot noise

Fig. 4. BER pattern

The minimum BER obtained for APD without shot noise isthe same as PIN without shot noise, while the APD and PINwith noise give the slightly higher value of BER. The averageof the BER for this system is 10-8 which shows an acceptable

performance for the WDM system. Although the eye patternlook the same, but the eye height is different. The eye heightof APD is larger than PIN photodector, which means that thesignal through PIN photodetector encountered more distortionthan the signal through APD photodetector. Therefore, the

photodetector of APD is more suitable in this designedsystem.

IV. CONCLUSIONS

The objectives of this project has been achieved where theresult analysis suggest that the optimum length of EDFA

fiber length will be 7m since it gives a highest output power

to WDM system compare to other value of length, a pump

power value of 250mW since this value can be supplied intoWDM system while providing a high gain and low NF. In

preamplifier, the signal is suggested to be as high as can so it

can travel further with using fewer repeaters to regain thesignal back.Even though this research stated the highest gain and lowest

NF that possible can be achieved, in real life the value might be very different. This is because of an occurrences of otherlosses such as thermal noise, dispersions such as cablesplicing effect and cable bending effect that will give a hugecontribution in lower value of gain and higher NF in thesignal compare to this project achievement.

ACKNOWLEDGMENT

Authors would like to thank Universiti Teknikal MalaysiaMelaka for their support in term of financing to this project.

R EFERENCES

[1] Paul Urquhart, Oscar Garcia Lopez, “Optical Amplifiers forTelecomunication”, IEEE, 2007

[2] Gerd Kaiser, “Optical Fiber Communication”, McGraw HillInternational Edition 2010, pp 398 – 421.

[3] J. Hansryd, P.A. Andrekson, M. Westlund, J. Li, P.-O.Hedekvist, S,A,"Fiber-Based Parametrics and their Applications", IEEE SelectedTopics in Quantum Electronics, 8 (3), 506-520, (2002

[4] E. Desurvire, "Erbium-Doped Fiber Amplifiers: Principles andApplications", Wiley, (1994).

[5] Dr. Neena Gupta Inderpreet Kaur, "A Novel approach for performanceimprovement of DWDM systems using TDFA-EDFA configuration,"IJECT, vol. I, no. 1, December 2010.

Erbium Doped Fiber Amplifier (EDFA) for C-Band Optical Communication System

Documents

Transcript of Erbium Doped Fiber Amplifier (EDFA) for C-Band Optical Communication System