Spatial optical transmitter based on on/off keying line coding modulation scheme for optimum performance of telecommunication systems

Indonesian Journal of Electrical Engineering and Computer Science
Vol. 21, No. 1, January 2021, pp. 305~312
ISSN: 2502-4752, DOI: 10.11591/ijeecs.v21.i1.pp305-312  305
Journal homepage: http://ijeecs.iaescore.com
Spatial optical transmitter based on on/off keying line coding
modulation scheme for optimum performance of
telecommunication systems
Hazem M. El-Hageen1
, Aadel M. Alatwi2
, Ahmed Nabih Zaki Rashed3
1,2
Electrical Engineering Department, University of Tabuk, Saudi Arabia
1
Egyptian Nuclear & Radiological Regulatory Authority, Egypt
3
Electronics and Electrical Communications Engineering Department, Menoufia University, Egypt
Article Info ABSTRACT
Article history:
Received Apr 11, 2020
Revised Jul 8, 2020
Accepted Jul 15, 2020
This study has presented a spatial optical transmitter based on on off keying
line coding modulation scheme for the optimum performance of
telecommunication systems. The encircled flux versus fiber core radius, the
3D graph for fiber mode versus core radius, and the signal power level in
dBm versus wavelength through coarse wavelength division multiplexing
with a fiber length of 20 km are presented and discussed in detail. The total
power measured in W and dBm as well as the signal power amplitude level
obtained through the infinite impulse response (IIR) filter based on both Z
domain and pole/zero coefficient filter types are illustrated clearly. Signal
gain, noise figure, maximum Q factor, and received power are also clarified
against bit rates for various modulation line coding schemes.
Keywords:
Line coding
On off keying
Optimum performance
Signal gain
Telecommunication system This is an open access article under the CC BY-SA license.
Corresponding Author:
Ahmed Nabih Zaki Rashed
Faculty of Electronic Engineering,
Menoufia University
Gamal Abd El-Nasir, Qism Shebeen El-Kom
Shibin el Kom, Menofia Governorate, Egypt
E-mail: zakirashed73355@gmail.com
1. RELATED WORKS
The information revolution is geared towards presenting, analyzing, and transporting information
with high efficiency. It relies on communication networks to transport information while computers are used
to present, analyze, and process data. Today, various data types are transmitted over communications
networks, namely, text, audio, images, computer data, videos, and so on. Therefore, the network must be
equipped with the requirements of all types of information and the communication networks must be
independent of the information type [1-6]. The networks that support various information types are called
multimedia networks. Huge amounts of high-speed multimedia data are being produced, so the design of
multimedia networks must be capable of handling this. Among the most important specifications that must be
met is the high bit rate for real-time video services [7-12].
Optical fiber links comprise the best solution for implementing multimedia networks for fixed user
locations. The development of manufacturing technology for detectors and light sources has attracted
considerable attention, as they are key to the development of optical communication systems [13-19]. The
use of fiber to implement local area networks (LANs) has increased. Consequently, common LANs such as
Ethernet, token bus, token ring, and star have been implemented using optical fiber, which bestows numerous

 ISSN: 2502-4752
Indonesian J Elec Eng & Comp Sci, Vol. 21, No. 1, January 2021 : 305 - 312
306
advantages. When the signal is optoelectronically regenerated or amplified [20-28], the network is classified
as an active broadcast network such as a token ring; otherwise, it is a passive broadcast network such as an
Ethernet or a token bus [29-37].
2. MODEL DESCRIPTION AND RESEARCH METHOD
Figure 1 shows the proposed simulation model for this study. User-defined sequence generators
generate a stream of bits, and all the bits are encoded with a hyperbolic secant pulse generator. The spatial
optical transmitter has the following technical specifications: frequency=1550 nm, power=0 dBm, on off
keying modulation type, power ratio array=1, extinction ratio=10 dB, and linewidth=10 MHz. The interaction
between the encoded electrical signal and the light signal happens through LiNbO3 modulators.
Figure 1. The simulation model for this study
These modulators are used to modulate the electro-optic signals. The modulated signal is directed to
the coarse wavelength division multiplexing (CWDM) with a fiber length of 20 km. The signal power, noise
power, input/output light signal-to-noise ratio, signal gain, and noise figure are determined using the dual-
port WDM analyzer. EDFA is used to compensate for the losses due to the attenuation in the fiber cable.
Fabry-Perot light filters are used to filter the original signal from any unwanted noise parts. The Fabry-Perot
light filters have the following technical specifications: frequency=193.1 THz, bandwidth=250 GHz, and free
spectral range=500 GHz. The light PIN photo-detectors convert the light signal to electrical form, which it is
later filtered by the infinite impulse response (IIR) filter. The encircle flux analyzer measures the electric
field distribution with the fiber core radius. The spatial visualizer measures the available number of modes in
the fiber with its configuration. The signal power level is measured with the time period by an optical
spectrum analyzer.

Indonesian J Elec Eng & Comp Sci ISSN: 2502-4752 
Spatial optical transmitter based on on/off keying line coding … (Hazem M. El-Hageen)
307
3. PERFORMANCE ANALYSIS WITH DISCUSSIONS
The maximum Q factor, minimum BER, and received power are measured through the BER
analyzer and the optical power meters, respectively. Based on the data in Table 1, the simulation results are
measured and clarified. Moreover, the encircle flux analyzer measures the electric field distribution with the
fiber core radius. The spatial visualizer measures the available number of modes in the fiber with its
configuration.
Table 1. Variables used in this work
Variables Value/Unit
Frequency 193.1 THz
Power 0 dBm
Transmission bit rate 10 Gb/s, 40 Gb/s, 100 Gb/s
Extinction ratio 10 dB
Fiber optic CWDM length 20 km
EDFA amplifier length 5 m
Optical filter bandwidth 250 GHz
PIN receiver responsivity 1 A/W
PIN receiver dark current 10 nA
Figure 2 shows the signal power level in dBm versus wavelength through the CWDM with a fiber
length of 20 km. The maximum signal power is -9.78205 dBm while the minimum noise power is -104.296
dBm. Figure 3 presents the encircled flux versus the fiber core radius through the CWDM with a fiber length
of 20 km. At a fiber core radius of 2 μm, the encircled flux reaches 20% but at a fiber core radius of 8 μm,
the encircled flux reaches 80%. In addition, at fiber core radii of 10 μm and 20 μm, the encircled flux reaches
100%. Figure 4 demonstrates the 3D graph for fiber mode versus core radius through the CWDM fiber with a
length of 20 km. The mode field Gaussian intensity distribution through the fiber core radius is from 10 μm
to 20 μm from the x axis. The polar power polarization in the x direction is shown in Figure 4.
Figure 5 indicates the total power measured in W and dBm through the IIR filter based on the Z
domain coefficient filter type. The total power is 277.158 μW or -6.437 dBm. Figure 6 demonstrates the total
power measured in W and dBm through the IIR filter based on the pole/zero coefficient filter type. The total
power is 544.784 μW or -2.638 dBm.
Figure 2. The signal power level in dBm versus wavelength through the CWDM fiber with a length of 20 km

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Figure 3. The encircled flux versus fiber core radius through the CWDM fiber with a length of 20 km
Figure 4. The 3D graph for fiber mode configuration versus core radius through the CWDM fiber with a
length of 20 km
Figure 5. The total power measured in W and dBm
through the IIR filter based on Z domain coefficient
filter type
Figure 6. The total power measured in W and
dBm through the IIR filter based on pole/zero
coefficient filter type

309
Figure 7 and Figure 8 show the signal power amplitude level through the IIR filter based on both Z
domain and pole/zero coefficient filter types. Based on the Z domain coefficient filter type, the maximum Q
factor is 13.44 and the minimum BER is 1.59 x 10-44
; these results are obtained using the IIR filter (Figure 7).
Meanwhile, based on the pole/zero coefficient filter type, the maximum Q factor is 14.216 and the minimum
BER is 3.44 x 10-46
; these results are obtained using the IIR filter (Figure 8).
Figure 9 presents the signal gain against transmission data rate for different line coding schemes.
For on-off line coding, the signal gain is 27.65 dB at 10 Gb/s, 13.46 dB at 40 Gb/s, and 9 dB at 100 Gb/s.
Meanwhile, for NRZ line coding, the signal gain is 24.65 dB at 10 Gb/s, 9.54 dB at 40 Gb/s, and 4.765 dB at
100 Gb/s. As the transmission bit rate increases, the signal gain decreases.
Figure 7. The signal power amplitude level through the IIR filter based on Z domain coefficient filter type
Figure 8. The signal power amplitude level through the IIR filter based on pole/zero coefficient filter type

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Figure 9. The signal gain against transmission data rate for different line coding schemes
Figure 10 indicates the noise figure against the transmission data rate for different line coding
schemes. For on-off line coding, the noise figure is 1.12 dB at 10 Gb/s, 2.56 dB at 40 Gb/s, and 4 dB at 100
Gb/s. Meanwhile, for NRZ line coding, the noise figure is 3.765 dB at 10 Gb/s, 5 dB at 40 Gb/s, and 7 dB at
100 Gb/s. As the transmission bit rate increases, the noise figure increases.
Figure 11 presents the maximum Q factor against the transmission data rate for different line coding
schemes. For on-off line coding, the maximum Q factor is 13.44 at 10 Gb/s, 4.88 at 40 Gb/s, and 1.65 at 100
Gb/s. Meanwhile, for NRZ line coding, the maximum Q factor is 10.23 at 10 Gb/s, 3.12 at 40 Gb/s, and
0.6754 at 100 Gb/s. As the transmission bit rate increases, the maximum Q factor decreases.
Figure 12 shows the received power against the transmission data rate for different line coding
schemes. For on-off line coding, the received power is 0.666 μW at 10 Gb/s, 0.49 μW at 40 Gb/s, and 0.44
μW at 100 Gb/s. Meanwhile, for NRZ line coding, the received power is 0.646 μW at 10 Gb/s, 0.489 μW at
40 Gb/s, and 0.4 μW at 100 Gb/s. As the transmission bit rate increases, the received power decreases.
Figure 10. The noise figure against transmission data rate for different line coding schemes
Figure 11. Max. The maximum Q factor against transmission data rate for different line coding schemes
0
5
10
15
20
25
30
10 Gb/s 40 Gb/s 100 Gb/s
Transmission Data Rates (Gb/s)
Signal
Gain
(dB)
On Off line coding
NRZ line coding
0
1
2
3
4
5
6
7
10 Gb/s 40 Gb/s 100 Gb/s
Noise
Figure
(dB)
On Off line coding
NRZ line coding
0
2
4
6
8
10
12
14
10 Gb/s 40 Gb/s 100 Gb/s
Max.
Q
Factor
On Off line coding
NRZ line coding

311
Figure 12. The received power against transmission data rate for different line coding schemes
4. CONCLUSION
We have simulated an on-off line coding modulation technique for a spatial optical transmitter
through a CWDM fiber with a length of 20 km for the optimum performance of telecommunication
broadcasting systems. The optimum transmission data rates are achieved at 40 Gb/s with acceptable
maximum Q factor, minimum BER, maximum signal gain, minimum noise figure, and maximum received
power. The signal power amplitude level and total power are measured through the IIR filter based on both
Z domain and pole-zero coefficient filter types. The encircled flux and 3D graph for fiber mode configuration
versus core radius through a CWDM fiber with a length of 20 km are also clarified in the graphs.
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10 Gb/s 40 Gb/s 100 Gb/s
Received
Power
(mW)
On Off line coding
NRZ line coding

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