Design and Simulate Modern Fiber Optic Communication Systems

Module 12


Optical PAM-M Transmitters


(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: optical_tx_pam.m

This source code simulates optical signal field by modulating the laser light of PAM-M (M = 2, 4, 8, 16, ..) data through MZ nonlinear modulators. This also generates unequal voltage amplitude levels for MZ nonlinear modulator so that the power levels signals in optical domain are equidistant. This gives the same eye heights in the eye diagram of PAM-M.

This source code calls the following functions:

(1) Pam_modulation.m: The laser light is modulated by PAM-M data. The number of symbols M can be specified by the user.

(2) time_diagram.m: Plots the time diagram.

(3) eye_diagram_pow: Plots the eye diagram. The Y-axis is optical power.

(4) power_meter.m: Calculates the average power in dBm.

(5) gauss.m: A Gaussian bandpass filter is introduced. The half-bandwidth (‘bw’) should be specified.

Explore Further this Module:

12.1 Roll-off factor ‘a’ determines how steep the pulse edge is. It takes values between 0 and 1 (a = 0 -> rectangular pulse). Modify the code by changing the roll-off factor from 0 to 0.9 and plot the time diagram, eye diagram and spectrum for M=4.

12.2 Change M from 4 to 16 with a step of 4 and plot the time diagram, eye diagram and spectrum. Choose a suitable roll-off factor , say ‘a’ = 0.6.

12.3 Change the duty cycle from 1 to 0.5 (corresponding to RZ 50% duty cycle) and repeat 12.1 and 12.2.

12.4 Change the bandwidth of the bandlimiting filter from 0.5*symbol rate to 4*symbol rate. Observe the change in the amount of noise in the eye diagram after the bandlimiting filter.

12.5 Design and simulate following PAM-M single channel optical transmitters with MZ nonlinear modulator:

PAM-4 single channel optical transmitters
PAM-8 single channel optical transmitters
PAM-16 single channel optical transmitters
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PAM-M (choose any value of M) single channel optical transmitters

Selected Simulated Results

Simulation of an Optical PAM-M (M = 2,4,8,16, ….) Transmitter consisting of an Optical MZ Nonlinear PAM-M  Modulator (Click to See the Results)



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