Necessity Of Optical Amplifiers Computer Science Essay

Hybrid Raman and Erbium Doped Fiber Amplifiers ( HFAs ) are a engineering for future heavy wavelength-division-multiplexing ( DWDM ) multiterabit systems. HFAs are designed in order to maximise the transmittal length and to minimise the damages of fibre nonlinearities, and to heighten the bandwidth of Erbium Doped Fiber Amplifiers ( EDFAs ) .

This undertaking simulates and evaluates the public presentation of intercrossed Raman and Erbium-Doped Fiber Amplifiers in optical transmittal systems utilizing Optisystem package. Since the public presentation of the amplifier is influenced by the parametric quantity of Optical Signal-to-Noise Ratio ( OSNR ) , Bit Error Rate ( BER ) , and Noise Figure, the job brush in this undertaking is to happen the best design parametric quantity for maximal approachable transmittal distance utilizing the intercrossed amplifiers.

Optisystem package is used as the simulation tools for the whole undertaking. Optisystem package is based on realistic mold of fiber ocular communications systems and serves a broad scope of applications, therefore it is an ideal simulation tools for this undertaking.

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Aims

The aims of the undertaking are:

• to plan intercrossed Raman and Erbium Doped Fiber Amplifiers utilizing Optisystem package.
• to supply a design parametric quantity for maximal approachable transmittal distance in optical transmittal system utilizing the intercrossed Raman and Erbium Doped Fiber Amplifiers.
• to measure the public presentation of the Hybrid Raman and Erbium Doped Fiber Amplifiers based on the amplifier 's addition, Optical Signal-to-Noise Ratio ( OSNR ) , Bit Error Rate ( BER ) , Noise Figure, and etc.
• to analyse the fake informations obtained from Optisystem package.

Problem statement

Optical amplifiers have become a necessary constituent in long-haul fibre ocular systems due to the demand for longer transmittal lengths. The effects of scattering and fading can be minimized in long-haul optical systems due to the innovation of Semiconductor optical amplifiers ( SOAs ) , Erbium Doped Fiber Amplifiers ( EDFAs ) , and Raman optical amplifiers.

One of the defects of EDFAs is their non flat-gain features across a given optical spectrum. In peculiar, the addition degree is well less at the terminal of the L-band between about 1600 nanometer and 1620 nanometer. Fortunately, the addition degree of such amplifiers can be rendered well level across the L-band window by the usage of addition flattening filters which are optically coupled between the spirals of Er doped fibre. However, the usage of such filters consequences in a higher noise figure in the channels holding wavelengths in the 1600-1620 nanometer scope. The well higher noise figure in the 1600-1620 nanometer scope lowers the useable bandwidth available from such EDFA amplifiers.

Raman amplifiers similarly have non-flat addition features. A typical Raman addition degree curve has minimal additions at about 1570 nanometer, 1595 nanometer, and 1620 nanometer, and upper limits at 1585 nanometer and 1610 nanometer. A addition flattening filter can be applied to cut down this fluctuation but will merely be optimized at a individual operating addition value. Additionally, there is the desire to minimise the figure of addition blandishing filters in the system and the loss they incur.

Clearly, there is a demand to cut down the maximal Noise Figure in EDFA addition, every bit good as to further flatten the addition curve in Raman-type amplifiers in order to cut down signal losingss throughout the web.

The innovation is a intercrossed optical signal amplifier that reduces the maximal Noise Figure of an EDFA while flattening the addition of a Raman amplifier without compromising optical maser pump efficiency.

Therefore, this undertaking simulates and evaluates the public presentation of intercrossed Raman and Erbium Doped Fiber Amplifiers ( HFAs ) in optical transmittal systems to supply a design parametric quantity for maximal approachable transmittal distance utilizing the intercrossed amplifiers.

Scope

This undertaking will concentrate chiefly on the simulation of intercrossed Raman and Erbium Doped Fiber Amplifiers ( HFAs ) utilizing Optisystem package. The public presentation of the amplifier will be evaluated depend on amplifier 's addition, Optical Signal-to-Noise Ratio ( OSNR ) , Bit Error Rate ( BER ) , and Noise Figure obtained from the simulation of a individual manner fibre transmittal nexus. The fiction or development of intercrossed Raman and Erbium Doped Fiber Amplifiers ( HFAs ) will non be covered in this undertaking.

Undertaking outcomes

It is expected that at the terminal of the undertaking, a design parametric quantity for maximal approachable transmittal distance utilizing the intercrossed amplifiers can be obtained.

Methodology

This undertaking starts with the searching of beginning and information respect loanblend Raman and Erbium Doped Fiber Amplifiers ( HFAs ) . The beginning and information are acquired from diary, mention books, e-Books, magazine and cyberspace. The circuit conventional diagram of intercrossed Raman and Erbium Doped Fiber Amplifiers ( HFAs ) is determined from the diary and simulate utilizing Optisystem package. All the parametric quantity likes amplifier 's addition, Optical Signal-to-Noise Ratio ( OSNR ) , Bit Error Rate ( BER ) , and Noise Figure that determines the public presentation of the HFAs is analyzed. The simulation procedure is repeated until the design parametric quantity for maximal approachable transmittal distance utilizing the intercrossed amplifiers can be obtained.

Thesis structure

Chapter 1: The first chapter provides a general inspiration for the undertaking. It includes the overview of undertaking ; the aims of undertaking, job statement, range of the undertaking and undertaking results.

Chapter 2: Undertaking 's background is illustrated in this chapter. By and large, this chapter summaries the literature reappraisal that have been studied. The construct and theory of the circuit conventional diagram of intercrossed Raman and Erbium Doped Fiber Amplifiers ( HFAs ) that is used for simulation will be explained in this chapter.

Chapter 3: The 3rd chapter is discussed about the methodological analysis of the undertaking. The method, stuffs and processs used to carry on the undertaking in accomplishing the aims of the undertaking is explained in inside informations.

Chapter 4: The chapter four will show all the simulation consequence from the Optisystem package. All the graphs and tabular arraies obtained from the simulation will be discussed in inside informations.

Chapter 5: The last chapter will reason all the findings and consequences obtained throughout the undertaking. The consequences will be evaluated based on the findings and the aims of the undertaking. Recommendations for future surveies besides will be included in this chapter.

Chapter 2 lITERATURE REVIEW

Optical amplifiers

Optical amplifiers have become a necessary constituent in long-haul fibre ocular systems due to the demand for longer transmittal lengths. The effects of scattering and fading can be minimized in long-haul optical systems due to the innovation of Semiconductor optical amplifiers ( SOAs ) , Erbium Doped Fiber Amplifiers ( EDFAs ) , and Raman optical amplifiers.

Optical Amplifier has three applications:

• Supporter
• In-line
• Pre-Amplifier

The transmittal side of the nexus is operated by a supporter amplifier, having a high input power, medium optical addition, and high end product power. The supporters are designed to magnify aggregative optical input power to make extension.

The center of an optical nexus is operated by an inline amplifier. It acts as a medium to moo input power, high end product power, high optical addition, and a low Noise Figure. It is designed for optical elaboration on the chief optical nexus between two web nodes.

The having terminal of an optical nexus is operated by a pre-amplifier. It functions as a medium to moo input power, medium end product power, and medium addition. Pre-amplifiers are besides designed for optical elaboration to counterbalance for the losingss in a demultiplexer located near the optical receiving system.

Semiconductor Optical Amplifiers

Semiconductor optical amplifiers ( SOAs ) really are laser rectifying tubes, with fibre attached to both terminals and do non hold terminal mirrors. The optical signal can comes from either side of the fibre, amplified by the semiconducting material optical amplifiers ( SOAs ) , and the signal comes out from the 2nd fibre. They are typically made in little bundle, and work for 1310 nanometer and 1550nm systems. Besides, the decreased size of the SOAs makes it an advantage over regenerators of EDFAs by conveying bidirectional. However, the disadvantage of SOAs includes polarisation dependance, high-coupling loss, and a higher noise figure. Figure 1 demonstrates the rudimentss of a semiconducting material optical amplifier.

Erbium Doped Fiber Amplifier ( EDFA )

Erbium Doped Fiber Amplifier ( EDFA ) is an optical amplifier that uses an optical fibre as a addition medium to magnify an optical signal. Rare-earth component Er ions Er3+ dope the nucleus of the optical fibre. There are three possible results for the signal photon, if a optical maser signal with a wavelength between 1520 and 1570 nanometer, and a 974 pump optical maser are fed into an erbium-doped fibre at the same time.

1. stimulated soaking up: signal photon excites an erbium ion from the province E1 to a higher degree E2 and go annihilated in the procedure
2. stimulated emanation: signal photon stimulates an Er ion at province E2 to disintegrate to E1, bring forthing another indistinguishable photon. Thus the signal is amplified.
3. signal photon can propagate unaffected through the fibre. In the mean while, self-generated emanation ever occurs between degree E2 and degree E1.

The population inversion os achieved between the energy degree E2 and E1 of erbium-doped fibre when pump optical maser power is high plenty. Thus, the input laser signal passing through the fibre is so amplified. The erbium-doped fibre and pump optical maser can be used to build an optical amplifier, viz. erbium-doped fibre amplifier ( EDFA ) .Pump optical maser could besides magnify the self-generated emanation. Therefore, ASE is ever present in EDFA, and it 's the chief beginning of noise in these amplifiers.

Advantages of EDFA are as follows:

• It provides high power transportation efficiency from pump to signal power.
• Large addition.
• It is polarization-insensitive.
• High end product power.
• No matching loss to the transmittal fibre.
• A individual EDFA can supply addition for multiple wavelengths at the same time.

The disadvantages of EDFA are Derive holding wavelength dependence. The difference addition will be obtained when usage with wavelength division multiplexing.

Raman Optical Amplifier

The Raman optical amplifier consists of a length of addition fibre combine with a pump assembly. The pump assembly contains a brace of pump optical maser rectifying tubes. The end product of a brace of orthogonally polarized pump-diode optical masers offers backward-propagating pump power in the transmittal fibre. Due to the higher-energy ( shorter wavelength ) pump photons scatter off the quiver manners of the optical fibre 's lattice matrix and coherently add to lower-energy ( longer wavelength ) signal photons, forward-propagating signals achieve addition in the fibre.

There are two types of Raman amplifier: distributed and distinct Raman amplifier. A distributed Raman amplifier is one in which the transmittal fibre is utilized as the addition medium by multiplexing a pump wavelength with signal wavelength, while a distinct Raman amplifier use a dedicated, shorter length of extremely nonlinear fibre to supply elaboration.

The advantages of Raman amplifier are:

• Ultrawide bandwidth elaboration.
• Low noise.
• No particular fibre is required.
• Suppressed nonlinearities public presentation in transmittal systems.

Hybrid Raman and Erbium-Doped Fiber Amplifier ( HFAs )

Hybrid Raman and Erbium Doped Fiber Amplifiers ( HFAs ) is a combination of Raman optical amplifier and Erbium Doped fiber amplifier. So, in order to understand HFAs, the feature of Raman optical amplifier and Erbium Doped fiber amplifier is study individually. The characteristic that is being study include operation, advantage and disadvantage of the amplifiers as discuss in the paragraph above. The constellation of intercrossed Raman and Erbium Doped Fiber Amplifiers is assuring for high capacity WDM transmittal. The amplifiers yield high-gain, low noise, and high end product power that via media for long distance transmittal.

Type I: Hybrid Raman and Erbium Doped Fiber Amplifier ( HFAs ) recycling residuary Raman pump in a cascaded EDF subdivision located after a scattering compensatingfiber ( DCF ) . Type I showed a addition of 20.8 dubnium at 1556 nanometer. The minimal Noise Figure of Type I was about 7.5 dubniums.

Type II: The difference between TypeII with Type Iis that the HFAs recycling residuary Raman pump in a cascaded EDF subdivision located prior to a DCF. The addition of Type II was 21 dubnium at 1556 nanometer. The minimal Noise Figure ofType II wasapproximately5 dubnium.

Type Three: Raman assisted EDFA. The peak addition wavelength of TypeIIIwas found to be at 1532 nanometer and the addition was 19 dubnium. The minimal Noise Figure of Type III was about 8 dubnium.

Type II has the larger addition and smaller Noise Figure as comparison to Type I and Type III.Thus, the Type II circuit will be used for simulation in Optisystem package.

Performance of optical amplifier

In the designation of the public presentation of an optical amplifier, some features have been defined. For illustration: addition, noise, optical signal/noise ratio ratio ( OSNR ) , bit error rate, and eye-pattern.

Addition

Gain is an of import parametric quantity in amplifiers that measures the elaboration per unit length of fibre. Additions are runing conditions and stuff used dependance. Difference wavelength has difference addition for all stuffs. For a low input powers, the end product power is relative to the addition times the length of fibre: Poutput = Pinput A- Gain A- Length.

The addition may saturate at high input powers. So, the end product power may merely increase in little fraction as input power addition. Basically the optical amplifier has run out of the power it needs to bring forth more end product.

Noise

By and large, optical amplifiers will add spontaneously emitted or scattered photons to the signal during the elaboration procedure, and this will do the signal/noise ratio ratio ( SNR ) degrade accordingly. A parameter Noise Figure ( NF ) , which is defined as the SNR ratio between input and end product quantify the SNR degradation.NF= SNRin / SNRout

The self-generated emanation can be reduced by an optical filter during pattern. Therefore, the SNR by and large will be dependent on the bandwidth of the optical filters and the spectral power distribution of the self-generated emanation from the amplifier. The self-generated emanation, which is emitted from the amplifier input terminal, may come in the signal beginning ( a semiconducting material optical maser ) , where it can ensue in public presentation perturbations. Therefore, so as to avoid extra noise in the system, it is ever needed to include isolation between amplifier and light beginning.

Signal-to-Noise Ratio

Signal-to-noise ratio can entree the public presentation of optical amplifiers, where it defines by the ratio of end product signal to the background noise. The higher the signal-to-noise ratio indicates the quality of the signal is higher. This means that the public presentation of the amplifier is good.

Bit Error Rate

The digital input and end product signals are compared utilizing spot error rates ( or ratio ) measurings to measure what fraction of the spots are received falsely. Bit error rates offer a quantitative measuring of signal quality. The typical acceptable spot error rate is 10-9.

Eye-Pattern

The other ways to measure rapidly the noise public presentation of an optically amplified system are through the usage of `` oculus forms '' displayed on the CRO. By the superposition of a random sequence of many 1s and 0 spot, such oculus forms are generated. This give a more qualitative position of the noise impressed on the digital transmittal form.  The end product amplitude is the extremum to top out electromotive force output.Jitter is the divergence of the pulsations signal from their ideal places in clip, measured in picoseconds.

Optical fibre

There are two types of fibre, which is individual manner fibre ( SMF ) and multimode fibre ( MMF ) .Light travel in a consecutive line and typically has a nucleus size of 8 or 10 micrometers doing by a individual manner fibre that has a really little nucleus. It has unlimited bandwidth that can travel unrepeated for over 80 kilometers, depending on the type of conveying equipment. Single manner fibre has immense information capacity, more than multimode fibre.

Multimode fibre supports multiple waies of visible radiation and has a much larger nucleus comparison to individual manner fibre. The nucleus size of multimode fibre is typically 50 or 62.5 micrometers. The light travels down a much larger way in multimode fibre, leting the visible radiation to travel down several waies or manners.

Since individual manner fibre is used for long distance transmittal, it will be discuss in more inside informations in the undermentioned paragraph.

Single Mode Fiber ( SMF )

Light is non reflected or refracted within single-mode fibre, but travels merely along the axis of the nucleus .

Modal scattering does non be in single-mode fibre since merely one manner is propagated. However, single-mode fibre is capable to other causes of pulse distributing such as chromatic scattering.

Chromatic dispersion

Chromatic scattering is the phenomenon wherein different spectral constituents of the familial lasersignal travel at different speeds in the fibre, geting at different times at the receiving system. It occurs because optical maser beginnings emit a scope of wavelengths: a primary individual wavelength and a narrow scope of secondary wavelengths on either side of this primary wavelength, as shown in Figure 2.6. The different wavelengths travel at somewhat different velocities through the fibre, and hence arrived at the receiving system at different times. This causes distributing, or scattering, of the standard pulsation. As the length of fibre additions, the difference in arrival times besides increases and the pulsations become wider. The end product pulses finally become identical from their neighbours and spot mistakes occur.

The bandwidth of a fibre decreases as chromatic scattering additions. Fewer spots can be transmitted in a given clip period because each spot will be wider and hence occupy a longer bit period. Chromatic scattering is the chief performance-limiting factor for single-mode fibre.

Dispersion-compensating fibre ( DCF )

By utilizing a really sophisticated fibre profile, it is possible to minimise scattering over the full wavelength scope from 1300 to 1550 nanometer, at the disbursal of really high loss ( around 2 dB/km ) ; this is known as scattering compensatingfiber. This fibre is designed with negative scattering features, so that when used in series with conventional fibre it will `` undisperse '' the signal. Dispersion-compensating fibre has a much narrower nucleus than standard single-mode fibre, which makes it susceptible to nonlinear effects.

Multimode Fiber vs. Single-mode Fiber

Single manner fibre will be used for this undertaking as the transmittal medium since it is used for long distance transmittal, typically 10 kilometers to 100 kilometers.

Chapter 3 Methodology

This chapter is mentioned about the attack and method used to measure the public presentation of Hybrid Raman and Erbium Doped Fiber Amplifiers.Content of this chapter include the method usage to roll up the informations, informations analysis and factor considered when taking the attack and method.

This undertaking starts with the rubric that is provided by the supervisor. The rubric of the undertaking is public presentation rating of Hybrid Raman and Erbium Doped Fiber Amplifiers ( HFAs ) . By understanding the undertaking range and demands, a thorough reappraisal on specific subjects were done.

The input to the HFAs is signal power and pump power. The public presentation of HFA is evaluated based on end product power, optical Signal-to-Noise Ratio ( OSNR ) , and Bit Error Rate that can be obtained from the simulation consequence of Optical Spectrum Analyzer. The simulation procedure is repeateduntil the maximal end product power, maximal optical Signal-to-Noise Ratio is obtained and the Bit Error Rate is smaller than 10-9.

The different value of input and end product value from simulation consequence will be tabular in tabular array and compared to supply a design parametric quantity for maximal approachable transmittal distance utilizing the intercrossed amplifiers.

There are different types of optical simulation package available in the market. For illustration: ModeSYS, OptSim, OptiSPICE, and Optisystem. OptiSystem is an advanced optical communicating system simulation bundle for the design, proving and optimisation of virtually any type of optical nexus in the physical bed of a wide spectrum of optical networks.The OptiSystem Component Library includes 100s of constituents that enable users to come in parametric quantities that can be measured from existent devices. Therefore, Optisystem package will be usage to imitate and measure the public presentation of the Hybrid Raman and Erbium Doped Fiber Amplifiers. However, the execution of HFAs into Optisystem package will merely be start at PSM 2.

Chapter 4 Preliminary result

Discussion

From through reading and research, the circuit that will be utilizing for the simulation is as in Figure 2.3, Type II of single-pump dispersion-compensating Hybrid Raman and Erbium-Doped Fiber Amplifier ( HFAs ) .

From Figure 2.3, the intercrossed amplifier recycling residuary Raman pump with a cascaded EDF subdivision located prior to a scattering compensatingfiber ( DCF ) . The Raman pump beginning consists of two optical maser rectifying tubes runing at 1455 nanometer and 1465 nanometer, severally. By uniting the two pump wavelengths with a inactive pump combiner, a entire power of up to 500mW was available. Since individual manner fibre is used for long distance transmittal, and the chromatic scattering is the chief performance-limiting factor for single-mode fibre. Therefore, a 12.6 kilometer DCF with 0.55 dB/km fading at a wavelength 1550 nanometer was used to counterbalance the fading. The 12.6 kilometers DCF with a group speed scattering of -98 ps/nm/km at 1550 nanometer can supply sufficient scattering for counterbalancing a 70 kilometer long individual manner fibre based transmittal p. By simulation, it is expected to acquire a addition of 21 dubnium and Noise Figure of 5 dubnium.

Decision

At the terminal of the undertaking, it is expected to supply a design parametric quantity for maximal approachable transmittal distance utilizing the Hybrid Raman and Erbium Doped Fiber Amplifiers. Some of the restraints that limit the maximal transmittal distance are pump power, signal power, type and length of fibre used. The public presentation of the HFAs will be evaluated based on the amplifier 's addition, Optical Signal-to-Noise Ratio ( OSNR ) , Bit Error Rate ( BER ) and Noise Figure obtained from the simulation consequence. A addition of 21 dubnium, Noise Figure of 5 dubnium, and bit error rate less than 10-9 should be obtained in simulation consequence.

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