Design and Simulate Modern Fiber Optic Communication Systems

Module 9

 

Channel Multiplexing Techniques

 

(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: fiber_prop_wdm_dd.m

Simulation of linear and nonlinear fiber optic direct detection WDM system.

This source code calls the following functions:

(1)  tx_nrz_ook.m : modulates the optical carrier by OOK data.

(2) power_meter.m : calculates the average optical power in dBm units.

(3) eye_diagram.m : plots the eye diagram.

(4) fiber_prop.m : Propagation in optical fiber (takes into account fiber dispersion and loss).

(5) amp.m : multiplies the input signal by gain factor and adds noise (the amount of noise is controlled by n_{sp}).

(6) opt_rect_filt.m : Optical ideal band pass filter to demultiplex the cental channel.

(7) gauss.m : An electrical (low pass) second order Gaussian filter.

(8) computeq_mzm.m : calculates Q-factors.


Explore Further this Module:

9.1 Change the channel spacing from 30 GHz to 200 GHz. Observe the WDM spectrum. Does the performance degrade as the channel spacing decreases? Explain.

Note: To have a reliable estimate of Q-factor, the number of bits should be really large. The average Q-factor obtained by running the code several times is more reliable than that obtained by a single run.

9.2 Change the number of channels, N_{{c}} from 1 to 10. Keep the channel spacing at 50 GHz. Observe the WDM spectrum. Does the performance change when N_{{c}} increases beyond 3? Explain. Ignore nonlinear effects by setting the nonlinear coefficients close to zero.

9.3 Change the number of transmission fiber spans from 10 to 30. Keep N_{{c}} = 5 and channel spacing = 50 GHz. Plot the Q-factor vs transmission distance. Make sure that Q-factor is obtained by averaging over multiple runs and it is converging.

9.4 Design and simulate following WDM direct detection fiber optic system links:

28 Gb/s/channel, 50 GHz channel spacing, 8 channel, 20 span WDM fiber optic system link
10 Gb/s/channel, 25 GHz channel spacing, 16 channel, 40 span WDM fiber optic system link
40 Gb/s/channel, 100 GHz channel spacing, 8 channel, 20 span WDM fiber optic system link
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n Gb/s/channel, m GHz channel spacing, M channel, N span WDM fiber optic system link
Choose the desired values of n, m, M and N for simulations.

Simulate more:

Switch on to Nonlinearity to design and simulate nonlinear WDM fiber optic system links.

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Selected Simulated Results

Design and Simulation of Linear and Nonlinear Fiber Optic Direct Detection WDM Systems (Click to see the Results)

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Source Code: ofdm_qam.m

Simulation of linear and nonlinear fiber optic QAM-M coherent OFDM systems.

This source code calls the following functions:

(1) qam_ofdm_transmitter.m : performs the IFFT of the data sequence.

(2) power_meter.m : calculates the average optical power in dBm units.

(3) fiber_prop.m : Propagation in optical fiber (takes into account fiber dispersion and loss).

(4) amp.m : multiplies the input signal by gain factor and adds noise (the amount of noise is controlled by n_{sp}).

(5) opt_rect_filt.m : Optical ideal band pass filter to truncate the spectrum.

(6) AtoD_convert.m : Analog to digital converter. The resolution N_{res} should be specified.

(7) DtoA_convert.m : Digital to analog converter. The resolution N_{res} should be specified.

(8) ofdm_receiver : performs the FFT operation.

(9) ber_calc_qam_ofdm.m : calculates the symbol error rate.


Explore Further this Module:

9.4 Change the number of subcarriers from 64 to 2048. Keep the symbol rate fixed at 12.5 GBaud and keep the tmax (and tmin) fixed. Calculate symbol error rate in each case. Compare the computational time as a function of the number of subcarriers. Change the guard interval if necessary to preserve the carrier orthogonality.

9.5 Change the transmission distance from 1600 km to 3200 km. Change the launch power if necessary so that BER is in the range of  10^{-3} to 10^{-2}. Change the guard interval so that carrier orthogonality is preserved. Plot the symbol error rate as a function of the guard interval.

9.6 Change the resolution of the A to D (and D to A) converter from 2 bits to 8 bits and plot the symbol error rate as a function of the resolution.

9.7 Design and simulate following QAM-M coherent optical OFDM fiber optic system links:

10 Gb/s, 512 subcarrier, 40 span QAM-M CO-OFDM fiber optic system link
25 Gb/s, 1024 subcarrier, 20 span QAM-M CO-OFDM fiber optic system link
40 Gb/s, 2048 subcarrier, 10 span QAM-M CO-OFDM fiber optic system link
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n Gb/s, m subcarrier, N span QAM-M CO-OFDM fiber optic system link
Choose the desired values of n, m and N for simulations.

Simulate more:

Switch on to Nonlinearity to design and simulate nonlinear QAM-M CO-OFDM fiber optic system links.


Selected Simulated Results

Design and Simulation of Coherent QAM-M OFDM Fiber Optic Communication Systems (Click to see the Results)

 

 

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