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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
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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
Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay Thorat
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(b)
(d)
of Modulated Signal at Transmitter for (a) 100 GHz channel spacing (b)
75 GHz channel spacing (c) 50 GHz channel spacing (d) 25 GHz channel spacing
launched to channel consisting of SSMF fiber as an
length 100 km and pure EDFA amplifier. Total gain obtained is 40 dB with two cascaded
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
Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay Thorat
for (a) 100 GHz channel spacing (b)
75 GHz channel spacing (c) 50 GHz channel spacing (d) 25 GHz channel spacing
an optical span with
length 100 km and pure EDFA amplifier. Total gain obtained is 40 dB with two cascaded
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
http://www.iaeme.com/IJECET/index.asp
(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.
Improving Spectral Efficiency of The 8 X 112 Gb/S PDM 16-QAM WDM Systems
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(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
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.
Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay Thorat
http://www.iaeme.com/IJECET/index.asp
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
Channel Wavelength (THz)
100 GHz ,75 GHz, 50 GHz and 25 GHz spacing at
Power 0 dBm with SSMF fiber at 100 km (X
-6
-4
-2
0
19
3.1
19
3.1
75
Log
of
SE
R
Channel Wavelength (THz)
Comparision of Log estimated SER for
100 GHz ,75 GHz, 50 GHz and 25 GHz
spacing at Power 0 dBm with SSMF fiber
Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay Thorat
http://www.iaeme.com/IJECET/index.asp 64 [email protected]
ction of Channel wavelength for 8 X 112 Gb/s PDM 16
for 100GHz, 75 GHz, 50 GHz and 25GHz Channel Spacing
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
for 100GHz, 75 GHz, 50 GHz and 25GHz Channel Spacing
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
Channel Wavelength (THz)
Comparision of Q Factor (dB) 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 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
Channel Wavelength (THz)
Comparision of EVM 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
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
Channel Wavelength (THz)
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
Akshay Gapchup, Ankit Wani, Ashish Wadghule and Akshay Thorat
112 Gb/s PDM 16-QAM system
for 100GHz, 75 GHz, 50 GHz and 25GHz Channel Spacing
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
Improving Spectral Efficiency of The 8 X 112 Gb/S PDM 16-QAM WDM Systems
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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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