Design and Simulate Modern Fiber Optic Communication Systems

Module 3

 

Lasers

 

(1) Use the Existing Modules / Components for Your Research Papers, Research Projects, Theses and Lab Simulation Experiments.
(2) Modify the Modules / Components to the Next Level for Your Research Papers, Research Projects and Theses.
(3) Integrate Different Modules / Components in the OCSim Package to Realize Your Own Fiber Optic Communication Systems.
(4) Modify the Modules for Co-Simulations with the Third Party Commercial Optical Communication Systems Softwares.

 

Source Code: laser_diode.m

The laser rate equations are numerically solved to obtain the photon density and carrier density. The first and second columns of the output are photon density and carrier density, respectively.

This source code calls the following function:
rate_eqn.m – solves the laser rate equations.

Explore Further this Module:

3.1 Choose a drive current I_{0} to be more than the threshold current. Plot the carrier density as a function of time. Under stead state conditions (large T), compare the carrier density with the threshold carrier density N_{th}. Provide explanation. Compare the power generated under steady state conditions with the analytical calculations.

3.2 Choose a drive current that is less than the threshold current. Plot the power generated as a function of time. Is the generated power significant? Explain your findings.

3.3 Change the drive current from I_{0} from I_{th} (threshold current) to 2 I_{th} with a suitable increment and plot the steady state power generated (at tfinal) as a function of the drive current. This curve is known as P-I curve.

Note: At larger drive currents, tolerances for ode45 may have to be changed.

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Source Code: laser_diode_pulse.m

The laser rate equations for pulses in a laser diode are simulated to obtain the photon density and carrier density.

This source code calls the following function:
rate_eqn_pulse.m: solves the laser rate equations for pulses in a laser diode.

Explore Further this Module:

3.4 Use a current pulse instead of the dc current (with a suitable DC bias so that the laser is biased above threshold). Let the first pulse be located at 5 ns with T0 (as defined in the code, rate_eqn_pulse.m) = 3ns. Modify the code to introduce three current pulses corresponding to a bit pattern of ’1101’ of a 100 Mb/s signal. Plot the output power (and also electron density) as a function of time. Explain any distortions you observe in the plot of optical power vs time. Are the optical power pulses broader than the current pulses?

3.5 Repeat (3.4) for a bit pattern of ’1101’ of a 200 Mb/s signal. Can you transmit 200 Mb/s signal using this laser diode? Provide explanation.

 

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