improving spectral efficiency of the 8 x 112 …€¦ · akshay gapchup, ankit wani, ashish...

http://www.iaeme.com/IJECET/index.asp 60 [email protected]

International Journal of Electronics and Communication Engineering and Technology

(IJECET)

Volume 8, Issue 2, March - April 2017, pp. 60–66, Article ID: IJECET_08_02_009

Available online at http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=8&IType=2

ISSN Print: 0976-6464 and ISSN Online: 0976-6472

© IAEME Publication

IMPROVING SPECTRAL EFFICIENCY OF THE

8 X 112 GB/S PDM 16-QAM WDM SYSTEMS

Acharya Geeta Nilesh and Rohit B. Patel

E&C Dept., U. V. Patel College of Engineering, Ganpat University, Kherva-384012

ABSTRACT

We carried out simulative analysis to investigate the spectral efficiency of 8 X 112

Gb/s wavelength-division-multiplexed systems based on polarization-multiplexed 16

quadrature amplitude modulation format along with coherent detection and digital

signal processing. We employed SSMF fiber as a channel with pure EDFA

amplification. The WDM system was analyzed and compared by measuring

performance parameters with channel spacing 100 GHz,75 GHz, 50 GHz and 25 GHz

at a fixed length of 100 km at 0 dB power level.

Key words: Wavelength Division Multiplexing (WDM), DP 16-Quadrature

Amplitude Modulation Format (16-QAM ), Spectral Efficiency, Digital Signal

Processing (DSP).

Cite this Article: Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay

Thorat, The Phone Sat and Application, International Journal of Electronics and

Communication Engineering and Technology, 8(2), 2017, pp. 60–66.

http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=8&IType=2

1. INTRODUCTION

The Higher spectral efficiency of WDM systems has become a need in current approach of

high capacity tremendous growing traffics with high speed. There are several methods to

improve the spectral efficiency. One of the technique to correct the spectral efficiency (SE) is

to eliminate self- phase modulation and cross-phase modulation [1]. Multilevel coding is also

a technique to improve SE [2]. Very high SE can be obtained by utilizing methods for optical

pulse shaping. The reason is that higher data rate channels are possible to incorporate in super

channels. So very high data rate transmission and thereby very high SE could be achieved [3].

Advanced modulation formats can be utilized to improve SE of WDM systems. Recently

polarization multiplexing with 16 QAM is the most attractive spectrally-efficient modulation

format [2, 4-10]. By employing amplitude modulation and phase modulation along with the

polarization multiplexing is the technique to enhance spectral efficiency of WDM system. It is

observed that performance of WDM system in terms of SE could be raised from 2 bits/sec/Hz

in DP-QPSK to 4 bits/sec/ Hz in DP-16 QAM [11].

We have incorporated coherent detection with digital signal processing technique to

enhance spectral efficiency of WDM DP16 QAM by taking benefit of its capability to accept

Improving Spectral Efficiency of The 8 X 112 Gb/S PDM 16-QAM WDM Systems


advanced modulation formats like m array QAM and capability to deal with received optical

domain information in the electric field for enhancing spectral efficiency of WDM system

[2,8,9,12-14]. Because these capabilities of coherent detection with DSP technique associated

with DP 16 QAM modulation format, WDM system could be able to mitigate against non-

linear impairments and also make it possible to compensate electrical impairments effectively

as conventional optical domain methods[2, 15,16].

Reduction in channel spacing of WDM system is one of the technique to enhance spectral

efficiency. But performance in terms of Q factor remarkably deteriorates with increased

channel spacing due to four wave mixing and fiber nonlinearity [4,17].

In this paper, we have simulated and evaluated the performance of WDM system by

employing spectral efficient DP 16-QAM as advanced modulation format as well as coherent

detection along with DSP. We have also utilized the technique of reducing channel spacing to

increase the spectral efficiency of WDM system. The light source in the transmitter consists

of 8 channels with data rates 112 Gbps having 8 lasers as optical sources.

We have employed SSMF fiber with two EDFA by keeping parameter of EDFA gain

equal to 20 dB. WDM system was simulated and evaluated by keeping 100 GHz channel

spacing at 0 dB power level at fixed span length of 100 km. Then we reduce the channel

spacing of the system to 75 GHz, 50 GHz and 25 GHz with a same power level at the same

length and evaluate the system.

2. SIMULATION DESIGN

We have simulated our design in Optiwave, Version. 13, Optical Communication System

Design Software [18]. Simulation setup of the WDM DP 16 QAM optical system used is

depicted in Figure. 1.

Figure 1 8 X 112 Gb/s WDM-PDM 16-QAM system

Eight channel wavelengths are generated using separate laser light source at the

transmitter. They are multiplexed in WDM multiplexer. The output signal from WDM

multiplexer and carrier signal generated by pseudorandom bit sequence generator are applied

to DP 16 QAM modulator. The resulting optical spectrum containing eight 112-Gb/s PM 16-

QAM modulated signals is shown in Figure. 2 (a) to (d) for channel spacing 100 GHz,75

GHz, 50 GHz and 25 GHz at a fixed length of 100 km at 0 dB power levels respectively.

Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay Thorat

http://www.iaeme.com/IJECET/index.asp

(a)

(c)

Figure 2 Optical Spectrum of Modulated Signal at

75 GHz channel spacing (c) 50 GHz channel spacing (d) 25 GHz channel spacing

Modulated signal is launched

length 100 km and pure EDFA amplifier. Total gain obtained is 40 dB with two cascaded

EDFA. Parameters for optical span

• Optical Span Length

• Area effective of Fiber, Aeff :

• Reference Wavelength

• Attenuation ,α : 0.2

• Dispersion, D :

• Nonlinear coefficient :

• Gain of EDFA

At the receiver end, we incorporate p

processing. We utilized the advantage

format and in compensation of most of the

constellation diagram ( X-component

Figure. 3(a) to 3(d) for channel spacing



(b)

(d)

of Modulated Signal at Transmitter for (a) 100 GHz channel spacing (b)


launched to channel consisting of SSMF fiber as an


optical span design is as below: [19]

: 100 km

Aeff : 80 µm2

: 1550 nm

0.2 dB/km

16.75 ps/nm/km

1.3 1/ W.km

: 20 dB

At the receiver end, we incorporate phase diversity coherent receiver with digital signal

advantage of DSP in the reception of DP 16

format and in compensation of most of the nonlinear fiber impairments [14]. The resulting

omponent) at the output after digital signal processing is shown in

. 3(a) to 3(d) for channel spacing 100 GHz, 75 GHz, 50 GHz and 25 GHz respectively


[email protected]

for (a) 100 GHz channel spacing (b)


an optical span with


hase diversity coherent receiver with digital signal

of DP 16-QAM modulation

fiber impairments [14]. The resulting

) at the output after digital signal processing is shown in

100 GHz, 75 GHz, 50 GHz and 25 GHz respectively.

Improving Spectral Efficiency


(a)

(c)

Figure 3 Constellation diagram

(c) 50 GHz channel spacing (d) 25 GHz channel spacing

3. SIMULATION RESULTS

In this paper, we have simulated, evaluated and analyzed the optical WDM system for

different channel spacing, 100

0 dB power level. We have utilized BER analyzer and spectrum analyzers to obtain the

values of Q-factor, BER and log10 (SER) and optical spectrum. The WDM system

performance was evaluated in terms of these parameters. We have ca

efficiency for both values of the

(b) and (c) for parameters Q Factor, EVM and log10 (SER)

different channel wavelengths with

for 0 dB power level at span length of 100 km.

From Figure 4(a), it can be observed that maximum value of Q factor is achieved for 100

GHz channel spacing. The value

the channel spacing. The best value of Q factor achieved is 12.38284194 dB for 100 GHz

channel spacing at 193.5 THz wave

5.994140769 dB for 25 GHz channel spacing at

It can be observed from Figure

spacing is decreased. The maximum

channel spacing, i.e. for 25 GHz.

1.12 b/s/Hz is achieved for channel spacing 50 GHz, 75 GHz and 100 GHz respectively.



(b)

(d)

Constellation diagram at DSP for (a) 100 GHz channel spacing (b) 75 GHz channel spacing

(c) 50 GHz channel spacing (d) 25 GHz channel spacing

RESULTS

we have simulated, evaluated and analyzed the optical WDM system for

100 GHz,75 GHz, 50 GHz and 25 GHz at span length 100 km

We have utilized BER analyzer and spectrum analyzers to obtain the

factor, BER and log10 (SER) and optical spectrum. The WDM system

performance was evaluated in terms of these parameters. We have ca

the channel spacing. Resultant graphs are shown in

(b) and (c) for parameters Q Factor, EVM and log10 (SER) (X-Polarization)

different channel wavelengths with 100 GHz ,75 GHz, 50 GHz and 25 GHz channel

for 0 dB power level at span length of 100 km.

4(a), it can be observed that maximum value of Q factor is achieved for 100

alue of Q factor achieved deteriorates with decreasing values of

spacing. The best value of Q factor achieved is 12.38284194 dB for 100 GHz

channel spacing at 193.5 THz wavelength. The minimum value of Q

for 25 GHz channel spacing at 193.2 THz wavelength.

Figure 4(a) that value of spectral efficiency increases as channel

aximum spectral efficiency of 4.48 b/s/Hz is achieved for lowest

channel spacing, i.e. for 25 GHz. The spectral efficiency of 2.24 b/s/Hz

2 b/s/Hz is achieved for channel spacing 50 GHz, 75 GHz and 100 GHz respectively.

M WDM Systems

[email protected]

spacing (b) 75 GHz channel spacing

we have simulated, evaluated and analyzed the optical WDM system for

at span length 100 km and

We have utilized BER analyzer and spectrum analyzers to obtain the

factor, BER and log10 (SER) and optical spectrum. The WDM system

performance was evaluated in terms of these parameters. We have calculated spectral

Resultant graphs are shown in Figure.4 (a),

Polarization) respectively for

50 GHz and 25 GHz channel spacing

4(a), it can be observed that maximum value of Q factor is achieved for 100

of Q factor achieved deteriorates with decreasing values of

spacing. The best value of Q factor achieved is 12.38284194 dB for 100 GHz

length. The minimum value of Q factor achieved is

4(a) that value of spectral efficiency increases as channel

4.48 b/s/Hz is achieved for lowest

efficiency of 2.24 b/s/Hz, 1.493 b/s/Hz and

2 b/s/Hz is achieved for channel spacing 50 GHz, 75 GHz and 100 GHz respectively.



Figure 4 (a) Q-Factor as a function

for 100GHz, 75 GHz, 50 GHz and 25GHz Channel Spacing

Figure 4 (b) EVM as a function

100GHz, 75 GHz, 50 GHz and 25GHz Channel Spacing

Figure 4 (c) Log (SER) as a

system for 100GHz, 75 GHz, 50 GHz and

0

5

10

15

19

3.1

19

3.1

75

Q F

act

or

(dB

)

Channel Wavelength (THz)

100 GHz ,75 GHz, 50 GHz and 25 GHz spacing at

Power 0 dBm with SSMF fiber at 100 km (X

00.10.20.3

19

3.1

19

3.1

75

EV

M




-6

-4

-2

0

19

3.1

19

3.1

75

Log

of

SE

R


Comparision of Log estimated SER for

100 GHz ,75 GHz, 50 GHz and 25 GHz

spacing at Power 0 dBm with SSMF fiber



ction of Channel wavelength for 8 X 112 Gb/s PDM 16


ction of Channel wavelength for 8 X 112 Gb/s PDM 16

100GHz, 75 GHz, 50 GHz and 25GHz Channel Spacing

as a function of Channel wavelength for 8 X 112 Gb/s PDM 16


19

3.2

5

19

3.3

25

19

3.4

19

3.4

75

19

3.5

5

19

3.6

25

19

3.7

19

3.7

75


Comparision of Q Factor (dB) for



Polarization) POWER = 0

dBm,

Spacin 100 GHz

POWER = 0

dBm,

Spacin 75 GHz1

93

.17

5

19

3.2

5

19

3.3

25

19

3.4

19

3.4

75

19

3.5

5

19

3.6

25

19

3.7

19

3.7

75


Comparision of EVM for



Polarization) POWER = 0

dBm,

Spacin 100 GHz

POWER = 0

dBm,

Spacin 75 GHz

19

3.2

5

19

3.3

25

19

3.4

19

3.4

75

19

3.5

5

19

3.6

25

19

3.7

19

3.7

75


Comparision of Log estimated SER for

100 GHz ,75 GHz, 50 GHz and 25 GHz

spacing at Power 0 dBm with SSMF fiber

at 100 km (X Polarization)POWER = 0

dBm,

Spacin 100 GHz

POWER = 0

dBm,

Spacin 75 GHz


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112 Gb/s PDM 16-QAM system


112 Gb/s PDM 16-QAM system for

112 Gb/s PDM 16-QAM

25GHz Channel Spacing

POWER = 0

Spacin 100 GHz

POWER = 0

Spacin 75 GHz

POWER = 0

Spacin 100 GHz

POWER = 0

Spacin 75 GHz

POWER = 0

Spacin 100 GHz

POWER = 0

Spacin 75 GHz



From Figure 4(b) and (c), It can be observed that minimum values of EVM and log10

(SER) can be achieved for 100 GHz channel spacing. Values of EVM and log10 (SER) are

increases, as channel spacing is decreased. The minimum values of 0.175004523 for EVM

and -1.677703194 for log10 (SER) are achieved for 25 GHz channel spacing at 193.275 THz.

It can be observed that better result of Q factor, EVM, and log10 (SER) can be achieved at a

higher value of channel spacing. At the same time, lowering of channel spacing gives the

better result of spectral efficiency.

4. CONCLUSION

The 8 X 112 DP 16 QAM WDM system is analyzed over SSMF fiber length 100 km 0 dB

power levels for 100GHz, 75 GHz, 50 GHz and 25GHz channel spacing. We achieved

12.38284194 dB of maximum Q factor at 100 GHz channel spacing as compared to

5.994140769 dB at 25 GHz at channel spacing at the same span length and power level. We

can achieve 106 % improvement in Q factor by increasing channel spacing from 25 GHz to

100 GHz. The system can perform best at higher channel spacing because nonlinearity and

dispersion could be compensated better with increasing channel spacing.

We have improved the spectral efficiency of DP 16 QAM WDM system by reducing

channel spacing. It is observed that performance of WDM system in terms of SE could be

raised from 1.2 bits/sec/Hz to 4.48 bits/sec/ Hz by reducing channel spacing from 100 GHz to

25 GHz.

It can be seen that at a higher value of channel spacing, the system performs better but at

the same time, spectral efficiency deteriorates. So trade-off should be made in choosing

higher or lower value of channel spacing as per requirement.

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improving spectral efficiency of the 8 x 112 …€¦ · akshay gapchup, ankit wani, ashish...

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