2 Channel Wavelength Division Multiplexing Systems

8/4/2019 2 Channel Wavelength Division Multiplexing Systems

1/21

2 CHANNEL WAVELENGTH DIVISION

MULTIPLEXING SYSTEMS


2/21

Aim:

simulating two 2- channel WDM System and

compute Bit error rate in different scenarios

Software used:

Optsim


3/21

Wavelength division multiplexing (WDM)

is a fiber-optic transmission technique that

employs light wavelengths to transmit data

parallel-by-bit or serial-by-character.


4/21

WAVELENGTH DIVISION MULTIPLEXING

COARSE WDM (C-WDM) DENSE WDM (D-WDM)

Both CWDM and DWDM are enhanced versions of WDM -

they support more channels than legacy WDM. But they are still WDM.

CWDM allows 8 channels.

DWDM allows 16 and above


5/21

LINEAR AND NON LINEAR EFFECTS SEEN

IN WDM

Two general types of dispersion affect DWDM systems.

1. Chromatic Dispersion, is linear2. Polarization Mode Dispersion (PMD), is nonlinear.

Linear effects such as attenuation and dispersion can be

compensated, but nonlinear effectsaccumulate.


6/21

2-CHANNEL WDM :10 Gbps link FOR 10km


7/21

Specificatons:1) Data source generate data of Bit rate 10 Gbps.

2) Two Direct modulated lasers modulated binary modulation

format like NRZ

DM laser 1 have central emission frequency at 1550nm,

optical power 3dBm & FWHM line width 10 MHz.DM Laser 2 have central emission frequency at 1310 nm,

optcal power 3dBm & FWHM line width 10 MHz.

3) Multiplexer is used to combine the signals.

4) single mode optical fiber of 10 km long is used.


8/21

5) Two Gaussian filters are used after the fiber.

Optical filter 1 is centered at 1550nm,-3dB,and BW of 10 GHz.

Optical filter 2 is centered at 1310nm,-3dB,and BW of 10 GHz.6) Optical Power Normalisers are used which average the

optical power and send it to the Compound receiver.7) Compound receiver consists of photodetectors,

pre-amplifiers,filters.Photodetectors are used at receiver side to convert opticalsignal into electrical signal.Bessel electrical filter is used in the compound receiver.Bessel electrical filter is low pass type, having number ofpoles 5,bandwidth as 10 GHz.


9/21

RESULTS AND ANALYSIS

EYE DIAGRAM AFTER 10km FOR 10 Gbps LINKFOR UPPER CHANNEL AT 1550 nm


10/21

EYE DIAGRAM AFTER 10km FOR 10 Gbps LINK

FOR LOWER CHANNEL AT 1310 nm


11/21

FOR THE ABOVE SIMULATED SYSTEM,BER IS

COMPUTED.THE RESULTS ARE SHOWN IN THE

FOLLOWING TABLE.

S.NO DISTANCE TYPE OF

LASER

DATA

RATE

OPERATING

WAVELENGTH

BIT ERROR RATE(BER)

1. 10km DM 10Gbps 1550nm 9.8125x10-7

2. 10km DM 10Gbps 1310nm 5.4654x10-11


12/21

From the table it is seen that at 1310nm,the BER

is better than the BER at 1550nm.This means thatlower channel transmits signal with lessattenuation than the upper channel which hassuffered from distortion effects like dispersion, and

non linear effects like SRS, SBS,FWM,etc and sohigher bit rate.


13/21

. 2-CHANNEL WDM :10 Gbps link FOR 40km


14/21

Specificatons:1) Data source generate data of Bit rate 10 Gbps.

2) Two Continuous Wave (CW)semiconductor lasers externally

modulated by binary modulation format like NRZ

CW laser 1 have central emission frequency at 1550nm,

optical power 3dBm & FWHM line width 10 MHz.

CW Laser 2 have central emission frequency at 1310 nm,

optical power 3dBm & FWHM line width 10 MHz.

Here external modulation is carried out by amplitude Dual arm

Mach Zehnder modulator .Mach Zehnder modulator has

maximumtransmissivity ,offset voltage of 0.5V & extinction ratio of 20dB

3) Multiplexer is used to combine the signals.

4) single mode optical fiber of 40 km long is used.


15/21

5) Two Gaussian filters are used after the fiber.

Optical filter 1 is centered at 1550nm,-3dB,and BW of 10 GHz.

Optical filter 2 is centered at 1310nm,-3dB,and BW of 10 GHz.6) Optical Power Normalisers are used which average the

optical power and send it to the Compound receiver.7) Compound receiver consists of photodetectors,

pre-amplifiers,filters.Photodetectors are used at receiver side to convert opticalsignal into electrical signal.Bessel electrical filter is used in the compound receiver.Bessel electrical filter is low pass type, having number ofpoles 5,bandwidth as 10 GHz.


16/21



LASER

DATA RATE OPERATING

WAVELENGTH

BIT ERROR

RATE(BER)

1. 40km CW,EXTERNALMODULATION

10Gbps 1550nm 5.3190x10-35

2. 40km CW,EXTERNAL

MODULATION

10Gbps 1310nm 8.8691x10-25

From the table it is seen that at 1550nm,the BER is better than theBER at 1310nm.Hence, the upper channel performs better.


17/21

. 2-CHANNEL WDM :10 Gbps link FOR

100km


18/21


EYE DIAGRAM AFTER 100km FOR 10 Gbps LINKFOR UPPER CHANNEL AT 1550 nm


19/21

EYE DIAGRAM AFTER 100km FOR 10 Gbps LINKFOR LOWER CHANNEL AT 1310 nm


20/21

FOR THE ABOVE SIMULATED SYSTEM,BER IS COMPUTED.THERESULTS ARE SHOWN IN THE FOLLOWING TABLE.


LASER

DATA

RATE

OPERATING

WAVELENGTH

BIT ERROR

RATE(BER)

1. 100km CW,EXTERNAL

MODULATION

10Gbps 1550nm 2.322x10-2

2. 100km CW,EXTERNAL

MODULATION

10Gbps 1310nm 6.6208x10-2

From the table it is seen that at 1550nm and at 1310nm, the BER is very very poor

and it is an inefficient transmission. The signal is attenuated and affected by the

non linear effects which are clearly visible from eye diagram where the eye is

poorly open.The performance can be improved if optical power boosters like

EDFA are used.


21/21

CONCLUSION

The principle of WDM, development of WDM

technology, its advantages and the linear and

non linear effects seen in WDM systems are

discussed briefly. Thus the two channel WDM

systems are designed intuitively and the

simulations are carried out and the

performance of the systems are analyzed with

the eye diagrams and with the obtained BER.

Date post:	07-Apr-2018
Category:	Documents
Upload:	akshit-gangwal
View:	228 times
Download:	0 times

2 Channel Wavelength Division Multiplexing Systems

Documents