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EDFA Simulink Model for Analyzing Gain Spectrum and ASE by Stephen Pinter. Presentation Overview. Project objectives Gain characteristics of EDFA wavelength dependant gain Gain flattening non-uniform gain over the spectrum implications. Project Objectives.
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EDFA Simulink Model for Analyzing Gain Spectrum and ASEby Stephen Pinter
Presentation Overview • Project objectives • Gain characteristics of EDFA • wavelength dependant gain • Gain flattening • non-uniform gain over the spectrum • implications
Project Objectives • Determine the optimum length for simulations • ASE not considered – optimum length is shorter when ASE taken into account • Expand the current EDFA Simulink model to show the gain over the entire 1550nm window • important to know gain in range 1530nm – 1560nm • Consider gain flattening, and • Integrate forward ASE into the EDFA model • Why Simulink?
Why use Simulink when an EDFA can be simulated using simulation tools such as OASIX or PTDS? • OASIX or PTDS • static model • input pump power is a static input internal to the EDFA module • Simulink • dynamic model • input pump power as well as other EDFA parameters can be easily modified
EDFA Gain characteristics • Significant equations governing EDFA dynamics • Output pump and signal power: • Quantities B and C characterize the physical EDFA and are given by: • To handle multiple signal wavelengths, Bs and Cs as well as the input signal must be multidimensional • Why?
and are wavelength dependant as shown in the figure • and are the absorption and emission coefficients, respectively • so, the quantities B and C are wavelength dependant • this relationship is how the wavelength dependency of the gain arises • EDFA gain ratio between the absorption and emission at a particular wavelength is critical in determining the gain
Note on Aspects of Simulation • when performing simulations on the EDFA model it is important to simulate all the wavelengths simultaneously instead of one at a time • EDFAs work in the nonlinear regime, so properties like linear superposition don’t hold true • when there are several channels in an EDFA there is an effect called gain stealing • the energy that each of the channels takes from the pump depends on the details of the emission and absorption spectra • before simulating the gain, the optimum length was determined
Optimum Length • gain varies significantly over wavelength • two distinct peaks • 12m and 30m • first peak • 1520-1536nm • choose Lopt = 12m
Simulink Models • implementation of the ordinary nonlinear differential equation used for studying EDFA gain dynamics • rate equation • input/output
EDFA Gain • significant gain variation is visible • about 11dB gain difference in the range 1530nm-1560nm • How do we flatten the gain?
Gain Flattening • using the equations shown earlier, I derived an equation relating the pump gain (GP) to the signal gain (GS) • the resultant equation is: • BP and CP are fixed, and BS and CS vary with wavelength • now GS can be fixed and GP for gain flatness can be obtained
for a GS of 30dB, GP should follow the curve shown in the figure • theoretical view of what the pump should be • practically, in order to get a different power at each wavelength might be difficult • something to be further analyzed