Optical PAM-M Transmitters

OCSim Modules

Modern Fiber Optic Communication Systems Simulations with Advanced Level Matlab Modules

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Module 12

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Optical PAM-M Transmitters


Company Researchers & Developers

Integrate the Modules with your in-house and Commercial Software & Hardware Products

 

(1) Use the Existing Modules / Components for Your Research & Development.
(2) Modify the Modules / Components to the Next Level for Your Research & Development.
(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.

 

Main Module

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 Module calls the following Sub Modules and Components:

(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.m
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

 

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Selected Simulated Results Using this Module

 

 

fig-1_block-diagram-of-optical-pam-m-transmitter

 

Block Diagram of Optical PAM – M Transmitter

 

 

Fig.2_Time Diagram

 

Time Diagram of Optical PAM – 4 Transmitter

 

 

Fig.3_Eye Diagranm BEFORE and AFTER Bandlimiting Filter

 

Eye Diagram BEFORE and AFTER Bandlimiting Filter of Optical PAM – 4 Transmitter

 

 

Fig.4_Spectrum BEFORE and After Bandlimiting Filter

 

Spectrum BEFORE and After Bandlimiting Filter of Optical PAM – 4 Transmitter

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