OCSim Modules: Module 14


OCSim Modules

Modern Fiber Optic Communication Systems Simulations with Advanced Level Matlab Modules

 

Module 14

 

Dual Polarization CO-OFDM Fiber Optic Communication Systems

 

(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.

 

Main Module

ofdm_qam_vec.m

Simulation of a FIBER OPTIC  QAM-M CO-OFDM communication system with dual polarization and PMD compensation. This module takes into account (1) dispersion, (2) nonlinearity, (3) PMD and (4) random coupling between polarizations in the fibers.


This Module calls the following Sub Modules and Components:

(1) qam_ofdm_transmitter_vec.m
Models the dual polarization OFDM transmitter.

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

(3) fiber_prop_vec.m
Propagation of dual polarization signal in OPTICAL FIBER. The model takes into account the (1) dispersion, (2) nonlinearity, (3) PMD and (4) random coupling between polarizations in the fibers.

(4) amp_vec.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_vec.m
Models the dual polarization OFDM receiver.

(9) ber_calc_qam_ofdm.m
Calculates the symbol error rate.

(10) const_diagram_ofdm.m
This function plots the constellation diagram for optical OFDM. FFT is performed on the OFDM symbol in each frame before plotting the constellation diagram.

(11) const_diagram_ofdm_direct.m
This function plots the constellation diagram for optical OFDM without taking FFT of each frame.

(12) mzm_iq.m
Calculates outputs of IQ modulators (MZM-I and MZM-Q Mach-Zehnder modulators) in OFDM.

 

Explore Further this Module:

14.1 For fiber optic DP-QAM-16 Coherent OFDM, Keep the symbol rate fixed at 12.5 GBaud, number of subcarriers = 256 and average power = -3 dBm. Choose the second order dispersion as 17 ps/nm/km (or -21 ps.ps/km) and set the nonlinear coefficient to zero. Calculate the symbol error rate as the number of samples in the guard interval (which is proportional to the duration of guard interval) changes from 16 to 48. Observe that the symbol error rate decreases as the duration of the guard interval increases. This is because the OFDM symbols in the neighboring frames interfere due to dispersion and the large guard intervals helps to mitigate the ISI due to dispersion.  Plot the symbol error rate as a function of the duration of guard interval.

14.2 For fiber optic DP-QAM-16 Coherent OFDM, Keep the symbol rate fixed at 12.5 GBaud, number of subcarriers = 256 and number of samples in the guard interval = 32. Choose the second order dispersion as 17 ps/nm/km (or -21 ps.ps/km) and set the nonlinear coefficient to zero. Change the launch power from -8 dBm to 1 dBm at a step of 1 dBm and plot the symbol error rate SER (or bit error rate) as a function of launch power. Observe that the SER decreases as the launch power increases due to the fact that the OSNR increases with the launch power.

14.3 Repeat 14.2 with the nonlinear coefficient = 1.1e-3. Change the launch power from -8 dBm to 1 dBm at a step of 1 dBm and plot the symbol error rate SER (or bit error rate) as a function of launch power.  Now observe that the SER decreases initially (in the linear regime). However, at higher launch powers (nonlinear regime), SER increases due to distortions caused by the fiber nonlinearity.

14.4 For fiber optic DP-QAM-16 Coherent OFDM, Keep the symbol rate fixed at 12.5 GBaud, number of subcarriers = 256 and number of samples in the guard interval = 32. Launch power = -3dBm. Choose the second order dispersion as 17 ps/nm/km (or -21 ps.ps/km) and set the nonlinear coefficient to zero.   Change the PMD parameter Dpp from 0.1 ps/sqrt(km) to 3 ps/sqrt(km) and plot the symbol error rate as a function of the PMD parameter. Observe that the SER without equalization is very large. However, after the PMD equalization, the SER is nearly constant (or a slight increase) showing that the equalizer effectively removes the degradations caused by PMD.

14.5 Repeat 14.1, 14.2, 14.3 and 14.4 with number of segments to 2, 4, 6, 8, 10, 12, 14, …. and observe the constellation diagrams at Rx. One segment is equal to 80km of fiber length.

14.6 Simulate fiber optic DP-QAM-M OFDM systems for other QAM-M modulations eg., QAM-2 (BPSK), QAM-4 (QPSK), QAM-8, QAM-32, QAM-64, QAM-128, QAM-256, …… .

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Selected Simulated Results Using this Module


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1. Fiber Optic Coherent OFDM Communication System (Full Simulation Setup)

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Block Diagram of an Optical OFDM System

Opt. mod.= optical modulator, P/S = parallel to serial, S/P = serial to parallel

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Simulation Setup – 1

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4. Fiber Optic Coherent OFDM Communication System (Transmitter)

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Block Diagram of an Optical OFDM Transmitter

S/P = serial to parallel, P/S = parallel to serial, DAC = digital to analog converter
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Simulation Setup – 2
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5. Fiber Optic Coherent OFDM Communication System (IQ Modulator)

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Block diagram of an Optical IQ modulator

MZM = Mach-Zehnder modulator, DAC=digital to analog converter

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Simulation Setup – 3

 


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fig-6_fiber-optic-dp-co-ofdm_rx

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Block Diagram of a Dual Polarization Optical OFDM Receiver

S/P = serial to parallel, ADC = analog to digital converter, DSP = digital signal processing

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Simulation Setup – 4

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.fig-7_fiber-optic-dp-co-ofdm_constellation_tx

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Constellation Diagram at Tx

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


.fig-8_fiber-optic-dp-co-ofdm_constellation_output-of-fo-link

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Constellation Diagram at the Output of FO Link

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


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fig-9_fiber-optic-dp-co-ofdm_contellation_seg-2

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Constellation Diagram after CD and PMD Equalization with no. of fiber segments 2 (160 km)

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


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fig-10_fiber-optic-dp-co-ofdm_constellation_seg-4

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Constellation Diagram after CD and PMD Equalization with no. of fiber segments 4 (320 km)

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


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fig-11_fiber-optic-dp-co-ofdm_constellation_seg-8

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Constellation Diagram after CD and PMD Equalization with no. of fiber segments 8 (640 km)

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


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fig-12_fiber-optic-dp-co-ofdm_constellation_seg-10

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Constellation Diagram after CD and PMD Equalization with no. of fiber segments 10 (800 km)

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


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fig-13_fiber-optic-dp-co-ofdm_constellation_seg-12

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Constellation Diagram after CD and PMD Equalization with no. of fiber segments 12 (960 km)

(Dual Polarization QAM-16 CO-OFDM Fiber Optic Communication Systems)

 


 

fig-14_fiber-optic-dp-co-ofdm-communication-system_pmd-equalization

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 Simulating PMD Equalization for the Optical OFDM System

    (PMD parameter = 1 ps/sqrt(km))

(Dual Polarization CO-OFDM Fiber Optic Communication Systems)

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OCSim Modules details can be seen by clicking the pages below:

OCSim Modules Overview | OCSim Modules (1-17) in the Package

Module (1a) | Module (1b) | Module (1c) | Module (2a) | Module (2b) | Module (2c) | Module (3a) | Module (3b) | Module (4a) | Module (4b) | Module (4c) | Module (4d) | Module (5) | Module (6a) | Module (6b) | Module (7) | Module (8a) | Module (8b) | Module (8c) | Module (9a) | Module (9b) | Module (10) | Module (11a) | Module (11b) | Module (12) | Module (13) | Module (14) | Module (15) Module (16) Module (17)


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