EDFA Simulink Model for Analyzing Gain Spectrum and ASE by Stephen Pinter

1. EDFA Simulink Model for Analyzing Gain Spectrum and ASEby Stephen Pinter

2. Presentation Overview • Project objectives • Gain characteristics of EDFA • wavelength dependant gain • Gain flattening • non-uniform gain over the spectrum • implications

3. 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?

4. 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

5. 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?

6.  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

7. 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

8. Optimum Length • gain varies significantly over wavelength • two distinct peaks • 12m and 30m • first peak • 1520-1536nm • choose Lopt = 12m

9. Simulink Models • implementation of the ordinary nonlinear differential equation used for studying EDFA gain dynamics • rate equation • input/output

10. EDFA Gain • significant gain variation is visible • about 11dB gain difference in the range 1530nm-1560nm • How do we flatten the gain?

11. 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

12. 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

13. Thank You