OCSim Modules: Module 17


OCSim Modules

Modern Fiber Optic Communication Systems Simulations with Advanced Level Matlab Modules

 

Module 17

 

Long Haul – WDM – Polarization Multiplexed QAM-M Fiber Optic Coherent 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

fiber_prop_vec_wdm_qam.m

This module simulates Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic coherent communication systems with (1) loss (2) nonlinearity (3) second order dispersion and (4) third order dispersion effects in N spans of single mode fibers and N in-line amplifiers. The Module includes (i) SPM and XPM Compensators (ii) Digital Back Propagation Technique (DBP) and (iii) Optical 90 degree Hybrid and Receiver Noise.
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This Module calls the following Sub Modules and Components:

(1) amp_vec.m
Inline amplifier is realized using this function. This amplifies the polarization multiplexed signal.

(2) ber_calc_qam.m
Calculates the BER by comparing the received bit pattern with the transmitted bit pattern.

(3) constellation_diagram.m
Plots the constellation.

(4) down_sample_CD.m
The number of samples per symbol for modeling the fiber optic system may be different from that used in DSP. This code provides down-sampling of the received signal by a factor that is suitable for DSP processing. 

(5) fiber_prop_vec_no_rot.m 
This code solves the Manakov equations using a split-step Fourier scheme.

(6) gauss.m 
A Gaussian bandpass filter is introduced. The half-bandwidth (‘bw’) should be specified. This could also be used as a low pass filter and in this case, ‘bw’ is the 3-dB bandwidth.

(7) norm_spectrum.m 
This function plots the normalized spectrum of the signal. 

(8) opt_rect_filt.m 
Rectangular filter is introduced to demultiplex the central channel. The half-bandwidth (f_0) should be specified.

(9) power_meter.m
Calculates the average power in dBm.

(10) power_meter_vec.m
Calculates the average power in dBm of the polarization multiplexed signal.

(11) QAM_modulator_nyquist.m
This code generates the QAM data. Arbitrary QAM-M can be generated. For example, when XX=4 and YY=4, we get QAM-16. When XX=8 and YY=8, we get QAM-64. This code can also generate QPSK data by setting XX=2 and YY=2. Nyquist pulses are generated with arbitrary roll-off factors.

(12) DBP.m : This function realizes DBP. DBP can be turned on/off using DBP_flag.

(13) Q_dB-calc.m : This function calculates Q-factor (dB). This code assumes that the noise is Gaussian and projects the Q-factor based on BER.

(14) coherent_rx.m : This function realizes a balanced IQ receiver. An optical 90 degree hybrid with in-phase and quadrature outputs is implemented. The output of 90 degree hybrid passes through the array of photo-detecrors [2]. Shot noise and thermal noise are introduced.

(15) fiber_optic_link.m : This function realizes the fiber optic link consisting of N fiber spans and N amplifiers. This function calls fiber_prop_vec_no_rot.m to realize fiber propagation and amp_vec.m to realize inline amplifier. Fiber propagation can be turned on/off using the fiber_prop_flag.

(16) Transmitter_realization.m : This is not a function. This code realizes the WDM transmitter. The computational time to realize the WDM transmitter increases with the number of channels. Sometimes, it is a good idea to generate the transmitter data only once and save it so that multiple fiber optic link runscan be done using the stored data. Use tx_realization_flag to turn on/off the transmitter realization part.

(17) init_parameter_file.m : This is not a function. All the system and signal parameters are specified here.

 

Explore Further this Module:

17.1. Pick XX=4 and YY=4 so that the QAM-16 data is generated. Symbol rate = 28 GSym/s, no. channels = 5, channel spacing = 50 Ghz. The range of launch power is -6 dBm to 0 dBm with an increment of 1 dBm. Let the transmission distance be 20X80 km. Plot the launch power vs BER after the CD compensation (before any type of nonlinear compensation), after simple XPM compensation with and without DBP. Calculate the transmission performance improvement (in terms of improvement in Q(dB)) due to DBP, if any.

17.2. Repeat experiment 17.1 by changing the distance from 15X80 km to 30X80 km with an increment of 3X80 km. Pick the optimal launch power in each case and plot the distance vs BER. Also, plot distance vs Q(dB).

17.3. Repeat experiment 17.1 and 17.2 with a single channel. Adjust the range of distances if needed. Compare the performance improvement using DBP for a single channel and for a 5 channel WDM system.

17.4. Pick XX=8 and YY=8 so that the QAM-64 data is generated. Repeat Experiment 17.1 and 17.2. Adjust the total transmission distance so that the BER is in the range of 1e-3 to 5e-2.
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Selected Simulated Results Using this Module 


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Normalized WDM Spectrum at the Transmitter

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

 


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Constellation Diagram of Central Channel at the Transmitter

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

 


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k-factor vs BER

(Total nonlinear phase accumulated over the fiber optic link due to SPM is k times
nonlinear phase. k depends on the system parameters such as CD and loss and
hence, it needs to be optimized)

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

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Constellation Diagram After Linear Equalizer Without Digital Back Propagation (DBP)

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

 


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Constellation Diagram After Digital Back Propagation (DBP)

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

 


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Constellation Diagram After Digital Back Propagation (DBP) and Nonlinear Compensation

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

 


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Normalized Spectrum at the Receiver before Demultiplexer

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent Communication Systems)

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Normalized Spectrum at the Receiver After Demultiplexer

(Long Haul WDM Polarization Multiplexed (PM) QAM-M Fiber Optic Coherent 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)


OCSim Modules Brochure 2018 | OCSim Modules Selected Publication References | OCSim Modules Application Examples |

OCSim Modules Selected Simulated Results OCSim Modules Videos       

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