Long Haul Nonlinear QPSK Fiber Optic Communication Systems with Chromatic Dispersion and Self Phase Modulation Compensations through Digital Signal Processing

OCSim Modules

Modern Fiber Optic Communication Systems Simulations with Advanced Level Matlab Modules

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Module 13

 

Nonlinear Coherent QPSK Fiber Optic Communication Systems

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Long Haul Nonlinear QPSK Fiber Optic Communication Systems with Chromatic Dispersion and

Self Phase Modulation Compensations through Digital Signal Processing


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

fiber_prop_nonlinear_coherent_qpsk.m

Compensation of Chromatic Dispersion (CD) and Self Phase Modulation (SPM) in a Long Haul Nonlinear Coherent QPSK Fiber Optic Communication System through Digital Signal Processing (DSP).


This Module calls the following Sub Modules and Components:

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

(2) constellation_diagram.m
Plots the constellation.

(3) tx_nrz_psk.m
The cw signal is modulated by an PSK data. To realize QPSK modulation, tx_nrz_psk.m is called twice, for the in-phase and quadrature components.

(4) fiber_prop.m
Solves the Nonlinear Schrödinger Equation (NLSE) using a split-step Fourier scheme.

(5) amp.m
Inline amplifier is realized using this function.

(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) raised_cosine.m
Raised cosine function in time domain

(8) down_sample_CD.m
This function does down-sampling with number of sample per symbol = down_sample_factor. For example, if down_sample_factor = 4, it means the number of samples per symbol at the receiver after down-sampling = 4.

(9) ber_calc_qpsk.m
Calculates the BER by comparing the received bit pattern with the transmitted bit pattern.


Explore Further this Module:

13.1 Turn off the nonlinearity (set ‘gam’=0) and plot the BER as a function of transmission distance. Choose the launch power (av_power_dBm = -6 dBm). Change the transmission distance from 120X80 km to 240X80 km. Change the number of bits, if needed. Observe that BER increases with distance.

13.2 Repeat 13.1 at a higher launch power (say – 3 dBm). Observe that BER is lower than that in 13.1 since higher launch power implies better performance in a linear system.

13.3 Turn on the nonlinearity (set ‘gam’=1.1 W ^{-1} km ^{-1}).  Fix the transmission distance as 150X80 km. Change the launch power from -8 dBm to 3 dBm (with an increment of 2 dBm) and plot the BER vs launch power. Observe that the BER decreases initially (linear regime) and then starts to increase (nonlinear regime).

13.4 Repeat 13.3 for a different transmission distance say 100X80 km. Adjust the number of bits to get a reliable estimate of BER.

13.5 Design and simulate following coherent QPSK fiber optic system links with digital signal processing:

28 GBaud, 20 span coherent QPSK fiber optic system link
10 GBaud, 60 span coherent QPSK fiber optic system link
28 GBaud, 20 span Nyquist pulse coherent QPSK fiber optic system link
10 GBaud, 60 span Nyquist pulse coherent QPSK fiber optic system link
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n GBaud, N span coherent QPSK fiber optic system link
n GBaud, N span Nyquist pulse coherent QPSK fiber optic system link
Choose the desired values of n and N for simulations.

Simulate more:

Modify to DP-QPSK optical Communication systems. Scientific and Programing support is available for modifying to DP-QPSK optical systems.

 

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Selected Simulated Results Using this Module

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Fig.1_Constellation Diagram at the Transmitter

 

Constellation Diagram at the Transmitter

(Long Haul QPSK Fiber Optic Communication Systems)

 

 

Fig.2_Constellation Diagram at the End of the Fiber Optic Link

 

Constellation Diagram at the End of the Fiber Optic Link

(Long Haul QPSK Fiber Optic Communication Systems)

 

 

Fig.3_Constellation Diagram After the CD Compensation

 

Constellation Diagram After the CD Compensation

(Long Haul QPSK Fiber Optic Communication Systems)

 

 

Fig.4_Constellation Diagram After the SPM Compensation

 

Constellation Diagram After the SPM Compensation

(Long Haul QPSK Fiber Optic Communication Systems)

 

 

Fig.5_Constellation Diagram After the Low Pass Filter

 

 Constellation Diagram After the Low Pass Filter

(Long Haul QPSK Fiber Optic Communication Systems)

 

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

OCSim Modules Overview | OCSim Modules (1-18) 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) | Module (18)


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