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Performance analysis of different modulation formats in 4-channel CATV transmission system using OADM
Optik 124 (2013) 6810–6814
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Performance analysis of different modulation formats in 4-channel CATV transmission system using OADM Amandeep Kaur Dhiman a,∗ , Taranvir Kaur b , Kamaljit Singh b , Kulwinder Singh a a b
Department of Electronics and Communication, Bhai Maha Singh College of Engineering, Sri Muktsar Sahib 152026, India Department of Electronics and Instrumentation, Sri Guru Granth Sahib World University, Fatehgarh Sahib, India
a r t i c l e
i n f o
Article history: Received 11 January 2013 Accepted 23 May 2013
a b s t r a c t In this paper we have analyzed the performance of different modulation formats for a four-channel WDM CATV system using optical ad drop multiplexers and the impact of frequency and wavelength on Q-value, and eye opening is observed for added and dropped channels at different lengths. © 2013 Published by Elsevier GmbH.
Keywords: Optical ad drop multiplexers (OADM) Return to zero (RZ) Non-return to zero (NRZ)
1. Introduction With the recent development optical networks require a variety of new features of which are security and reliability. Since the information carried by the optical carrier is too large and requires features that ensures the signal is always up to the user even in damage whatsoever [1,4]. To meet up the rapid development will require further improvements in the existing optical networks by using OADM (optical add–drop multiplexer). Optical multiplexers are specially designed for WDM (wavelength division multiplexing) systems. The demultiplexers undo the operation which the multiplexers have done. It separates the multiplicity of wavelengths into fiber and directs them to many fibers. Optical multiplexers are used to couple two or more wavelengths into a single fiber. If a demultiplexer and a multiplexer are properly aligned and placed back-to-back, it is clear that in the area between them, two individual wavelengths exist [9,10]. This presents an opportunity for an enhanced function, one in which individual wavelengths could be removed and also inserted. Such a function would be called an optical wavelength add and drop multiplexer/demultiplexer or we can say optical add–drop multiplexer (OADM). The OADM selectively removes (drops) a wavelength from a multiplicity of wavelengths in a fiber, and thus from the traffic on the particular channel. It then adds in the same direction of data flow the same wavelength, but with different data content. Mohammad Syuhaimi Ab-Rahman [1] proposed a paper to do improvements in the function of OADM devices by combining these two devices in parallel. This increases
the reliability of an optical network. Ahmed Nabih Zaki Rashed [2] discussed that the OADM based on DWDM (dense wavelength division multiplexing) technology is moving the telecommunications industry significantly closer to the development of optical networks. The OADM can be placed between two end terminals along any route and be substituted for an optical amplifier. Commercially available OADM allows carriers to drop and/or add up to multi channels between DWDM terminals. By deploying an OADM instead of optical amplifier, service providers can gain flexibility to distribute revenue-generating traffic and reduce costs associated with deploying end terminals at low traffic areas along a route. This paper has proposed OADM for high transmission bit rates at room temperature for best performance efficiency. It is observed that the decreased number of transmitted channels increased the optical transmitted power. Optical Add/drop comprised many optical passive devices such as Fiber Bragg grating, interference filters, circulators and Mach–Zehnder interferometer. Although add/drop filters including those devices have good operating performances, their cost is too expensive to apply for DWDM based optical networks [5,6]. Mohammad Syuhaimi Ab-Rahman [3,8] discussed that wavelength selective add–drop filter is required for adding and dropping a particular wavelength division multiplexing channel at each subscriber’s node in the WDM based optical networks. We came to our results with the help of Simulative analysis of integrated DWDM and MIMO-OFDM system with OADM was done recently for optical-OFDM system [11] and monitoring and compensation of optical telecommunication channels [12]. 2. Simulation setup
∗ Corresponding author. E-mail addresses: [email protected] (A.K. Dhiman), kamal [email protected] (K. Singh), Monga [email protected] (K. Singh). 0030-4026/$ – see front matter © 2013 Published by Elsevier GmbH. http://dx.doi.org/10.1016/j.ijleo.2013.05.094
The main function of an optical multiplexer is to couple two or more wavelengths into single fiber. OADMs are classified as
A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
6811
Fig. 1. Simple optical add–drop multiplexer [G.P. Aggrwal].
Fig. 3. Superimposed eye diagram of 4-channels.
Fig. 4. Superimposed eye diagram of inserted and dropped channel 2.
Q-Value at different modulation formats 35 30 25 20 15 10 5 0
channel 1
The different modulation formats have been compared for 4channel CATV transmission system in the terms of Q value, BER, eye opening, eye closure and jitter. In CATV transmission system we have 4-channel WDM transmitter by which we transmit different modulation format through 4 channels. We find Q-value, BER, eye opening, eye closure and jitter for different modulation format in each channel. Eye diagram for different modulation formats is given (Fig. 3). Electrical scope is used to view the eye diagram of channels. Electrical scope have bit rate 10 Gb/s. It is the bit rate of input signals. Electrical input is given to this component. This component simulates an oscilloscope for electrical signals. It collects data that will be available for eye diagrams (Figs. 4 and 5).
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
3. Results and discussion
NRZ Raised Cosine
channel 2
NRZ Rectangular
Q-Value (dB)
fixed-wavelength and as dynamically wavelength selectable OADMs. In fixed wavelength OADM, the wavelength has been selected and remains the same until human intervention changes it. In dynamically selectable wavelength OADM, the wavelength between the optical multiplexer may be dynamically directed from the outputs of the demultiplexer to any of the inputs to multiplexer. We use ideal optical add–drop multiplexer without optical loss and crosstalk. In simple OADM first component is optical splitter as shown in Fig. 1.This component implements a balanced splitter with the same attenuation on each output. If unbalanced splitter is required, simply follow the splitter with the proper attenuation on each side. If the attenuation is set to 0 dB, this component implements an ideal splitter without any insertion loss, i.e. a component perfectly splits the input signal. Optical filter simulates an optical fiber. In our experiment we use Raised-Cosine-Notch filter. Next component is optical combiner. This component implements a balanced combiner with the same attenuation on each input. If unbalanced combiner is required, simply precede the combiner with the proper attenuation on each input. If the attenuation is set to the default value 0 dB, the component implements an ideal combiner without any insertion loss, i.e. a component that perfectly adds the input signals (Fig. 2).
Channel 3 channel 4
Modulation Formats
Fig. 5. Q-value at different modulation formats in 4-CATV transmission channels.
Optsim simulates the Q-value. Q-value is the ratio of mean and standard deviation of received signals. To have good estimation of Q-value 100–200 bits are simulated so to have a good accuracy on the evaluation of the mean and standard deviation on the received signal. We can set the number of simulated bits at given bit rate (Fig. 6). The evaluation of the BER in optical system simulation is in general a nontrivial task. Error counting is usually impracticable, since the target BER is typically of the order of 109. Therefore to measure
Fig. 2. Germanized block diagram for CATV 4-channel transmission system [Senior].
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A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
Q-Value against Wavelength
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
channel 2 Channel 3 channel 4
45 40 35 30 25 20 15 10 5 0
Q-Value (dB)
channel 1
NRZ Rectangular
BER
BER at different modulation formats 6.00E-03 5.00E-03 4.00E-03 3.00E-03 2.00E-03 1.00E-03 0.00E+00
modulation format
Fig. 6. BER at different modulation formats in 4-CATV transmission channels.
NRZ rectangular NRZ raised cosine RZ rectangular RZ raised cosine RZ supergauss ian RZ soliton
1665.5 1620.5 1577.9 1537.4 1499 1199.2 Wavelength (nm)
Fig. 10. Q-value (inserted channel) against wavelength. channel 1
Q-Value against Wavelength
Channel 3
29
channel 4
modulation format
Fig. 7. Eye opening at different modulation formats in 4-CATV transmission channels.
28
RZ rectangular RZ raised cosine
24
RZ supergaussian
23 22
RZ soliton
21 1665.5 1620.5 1577.9 1537.4 1499 1199.2
8 7 6 5 4 3 2 1 0
Wavelength (nm) channel 1
Fig. 11. Q-value (dropped channel) against wavelength.
Channel 3 channel 4
ito n so l RZ
Q-value (dB)
re ct an NR gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
200 250
Q-Value against Frequency 29 28 27 26 25 24 23 22 21
180 185
so l
ito n
190
Z NR
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
NRZ Rectangular
195
Fig. 11 shows the Q-value of dropped channel (channel 2) from OADM against wavelength with decrease in wavelength the Qvalue of RZ raised cosine modulation format decreases from 28 to 26.2 dB. Fig. 12 shows the Q-value of inserted channel (channel 2) in OADM against frequency (THz) for different modulation formats. The diagram shows the Q-value at different frequencies. At all frequencies the Q-value for NRZ rectangular and NRZ raised cosine is rapidly decreasing. For other modulation formats the Q-value increases for all frequencies as shown above. Fig. 13 shows the Q-value of dropped channel (channel 2) from OADM against frequency (THz). The diagram shows the Q-value of
Channel 3
Fig. 9. Jitter at different modulation formats in 4-CATV transmission channels.
190
Fig. 12. Q-value (inserted channel) against frequency.
channel 2
modulation format
185
Modulation format
channel 1
channel 4
180
RZ
Jitter at different modulation formats 0.03 0.025 0.02 0.015 0.01 0.005 0
Q-Value against Frequency
Z
a realistic BER it should be necessary to simulate 1010 bits, a quantity that is not a reasonable value in software simulation. Optsim provides two different components to estimate the transmission performance. Both of them are based on the estimation of some statistical parameters, i.e. Q-value and BER (Fig. 7). The eye opening is the difference between the minimum values of the samples related to logic “1” and the maximum value related to logic “0”, measured at the sampling instant (Fig. 8). The eye closure is defined as by 10 log10 [(average opening)/(opening)]. Eye opening and eye closure values depend on the sampling instant and on the decision threshold. Therefore the eye opening may be evaluated by using the optimum values for sampling instant and decision threshold (i.e. to obtain highest Q or lowest BER) (Fig. 9). The jitter value is the standard deviation of the received RZ signal maximum with respect to the specified sampling instant. The signal maximum depends on the decision threshold; therefore the jitter may be evaluated by using optimum values of the sampling instant and decision threshold (i.e. to obtain highest Q and lowest BER). Fig. 10 shows the Q-value of inserted channel (channel 2) in OADM against wavelength. With decrease in wavelength and Q-value of RZ raised cosine modulation format increases from 25–30 dB. The Q-value of other modulation formats remains almost same as shown in above diagram.
NR
Fig. 8. Eye closure at different modulation formats in 4-CATV transmission channels.
45 40 35 30 25 20 15 10 5 0
Q-Value (dB)
modulation format
re ct an NR gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
channel 2
NRZ Rectangular
Eye Closure (dB)
NRZ raised cosine
25
Eye Closure at different modulation formats
Jitter (ns)
NRZ rectangular
27 26
Q-Value (dB)
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
channel 2
NRZ Rectangular
Eye Opening (au)
Eye Opening at different modulation formats 0.005 0.004 0.003 0.002 0.001 0
modulation format
Fig. 13. Q-value (dropped channel) against frequency.
195 200 250
0.003
RZ raised cosine
0.002
RZ supergauss ian
0.001
RZ soliton
185 190
NR
1666 1620 1578 1537 1499 1199
Fig. 17. Eye opening (dropped channel) against frequency.
Fig. 14. Eye opening (inserted channel) against wavelength.
Eye Opening against Wavelength
Jitter against Wavelength 0.03
0.007
NRZ rectangular
0.006 0.005
NRZ raised cosine RZ rectangular
0.004
RZ raised cosine
0.003
RZ supergauss ian
0.002 0.001
0.025
Jitter (ns)
RZ soliton
NRZ rectangular NRZ raised cosine
0.02
RZ rectangular
0.015
RZ raised cosine
0.01
RZ supergauss ian
0.005
0
RZ soliton
0 1666 1620 1578 1537 1499 1199
1666 1620 1578 1537 1499 1199
Wavelength (nm)
Wavelength (nm)
Fig. 15. Eye opening (dropped channel) against wavelength.
Jitter against Wavelength 0.025 NRZ rectangular
jitter (ns)
0.02
NRZ raised cosine 0.015
RZ rectangular RZ raised cosine
0.01
RZ supergauss ian 0.005
RZ soliton
0 1666 1620 1578 1537 1499 1199 Wavelength (nm)
Fig. 19. Jitter (dropped channel) against wavelength.
ito n so l RZ
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
200 250
NR
0.025 0.02 0.015 0.01 0.005 0
NR
250
so l
ito n
190
Z
200
185
RZ
195
180
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
190
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n RZ so lito n
195
Fig. 20. Jitter (inserted channel) against frequency.
Jitter (ns)
185
Z
190
Jitter against frequency
180
NR
185
Modulation formt
Eye Opening Against Frequency 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0
180
Z
Jitter (ns)
Jitter against frequency 0.03 0.025 0.02 0.015 0.01 0.005 0
NR
different modulation formats at different frequencies. At 185 THz RZ raised cosine has maximum value of 28 dB. Fig. 14 shows the eye opening of inserted channel (channel 2) in OADM against wavelength at 1620 nm wavelength RZ soliton modulation format has maximum value 0.006 a.u. NRZ raised cosine modulation format has lowest eye opening. Fig. 15 shows the eye opening of dropped channel (channel 2) from OADM. RZ soliton has lowest eye opening at 1620 nm wavelength. Fig. 16 shows the eye opening of inserted channel (channel 2) in OADM against frequency. The diagram shows the eye opening of different modulation formats at different frequencies. At 185 THz RZ soliton has maximum eye opening. Fig. 17 shows the eye opening of dropped channel (channel 2) from OADM against frequency. At 180 THz RZ raised cosine has maximum eye opening. Fig. 18 shows the jitter value of inserted channel (channel 2) in OADM against wavelength. RZ soliton has minimum jitter value as shown in the diagram. Fig. 19 shows the jitter value of dropped channel (channel 2) from OADM. RZ soliton has minimum jitter value as shown in the diagram. Fig. 20 shows the jitter value of inserted channel (channel 2) in OADM against frequency. Above diagram shows the jitter value of different modulation formats at different frequencies. RZ soliton
Fig. 18. Jitter (inserted channel) against wavelength.
NR
Eye Opening (a.u)
0.008
Eye Opening (a.u)
250
Modulation format
Wavelength (nm)
NR
195 200
Z
0
180
ito n
RZ rectangular
so l
NRZ raised cosine
0.004
RZ
NRZ rectangular
0.005
Eye Opening against Frequency 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0
NR
Eye Opening (a.u)
0.006
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re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
Eye Opening against Wavelength 0.007
Eye Opening (a.u)
A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
Modulation format
Modulation format
Fig. 16. Eye opening (inserted channel) against frequency.
Fig. 21. Jitter (dropped channel) against frequency.
195 200 250
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A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
Q-Value (dB)
Q-Value against Distance 45 40 35 30 25 20 15 10 5 0
Channel 1 Channel 2 Channel 3 Channel 4 Inserted Channel
modulation format has maximum Q-value, that is 40 dB. When this channel has dropped from OADM has 25 dB Q-value. RZ soliton has maximum eye opening. Jitter value of RZ Raised Cosine is increases with increase in wavelength. Jitter remains same for other modulation formats with increase in wavelength. Q-value decreases with increase in fiber length.
Dropped Channel
References 50
100
150
Distance (Km)
Fig. 22. Q-value against distance.
has the minimum jitter value at all frequencies as shown in the diagram. Fig. 21 shows the jitter value of dropped channel (channel 2) from OADM against frequency. RZ modulation formats have less jitter value as shown in the diagram. Fig. 22 shows the Q-value against distance. Q-value decreases as we increase the distance as shown in above diagram. At 150 km channel 3 has less Q-value. 4. Conclusion Different modulation formats have been compared for 4channels of CATV transmission system. Q-value (dB) is decreased due to fiber non-linearities. The better Q-value is provided by the RZ Rectangular modulation format in channel 2. RZ Raised Cosine have high BER rate. NRZ Rectangular gives the better performance because it has high eye opening and less eye closure. This paper concluded that with decrease in wavelength there is no change in Q-value of Inserted channel 2 in OADM. NRZ Rectangular
[1] M.S. Ab-Rahman, Parallel connected optical add drop multiplexers (PC-OADM) extend the features of optical communication system, J. Appl. Sci. Res. 7 (2011) 1633–1639. [2] Ahmed Nabih Zaki Rashed, Optical add drop multiplexer (OADM) based on dense wavelength division multiplexing technology in next generation optical networks, Int. J. Multimedia Ubiquit. Eng. 7 (2012). [3] M.S. Ab-Rahman, et al., Low cost encoding devices for optical code division multiple access system, Am. J. Eng. Appl. Sci. 2 (2009) 317–323. [4] Ab-bou, et al., Performance evaluation of dispersion managed optical TDMWDM transmission system in the presence of SPM, XPM and FWM, J. Opt. Commun. 28 (2007) 221–224. [5] P.S. Andre, et al., Optical add–drop multiplexer based on fiber Bragg gratings for dense wavelength division multiplexing networks, J. Opt. Commun. 17 (2002) 333–339. [6] P.S. Andre, et al., Selective wavelength transparent optical add–drop multiplexer based on fiber Bragg gratings, J. Opt. Commun. 24 (2006) 222–229. [8] M.S. Ab-Rahman, et al., The hybrid protection scheme in hybrid OADM/OXC/MUX, Aust. J. Basic Appl. Sci. 2 (2008) 968–976. [9] A. Abd El-Naser, Mohammed, et al., Important role of optical add drop multiplexers (OADM) with different multiplexing techniques in optical communication networks, Int. J. Computing 9 (2010) 152–164. [10] A. Abd El- Naser, Mohammed, et al., High transmission bit rate of thermal arrayed waveguide grating (AWG) module in passive optical networks, Int. J. Comput. Sci. Inf. Security 1 (2009) 13–22. [11] K.S. Bhatia, R.S. Kaler, T.S. Kamal, R. Randhawa, Simulative analysis of integrated DWDM and MIMO-OFDM system with OADM, Optik (2012), http://dx.doi.org/10.1016/j.ijleo.2011.11.081. [12] K.S. Bhatia, R.S. Kaler, T.S. Kamal, R. Kaler, Monitoring and compensation of optical telecommunication channels by using optical add drop multiplexers for optical OFDM system. Copyright © 2012 De Gruyter. doi:10.1515/joc-20120001.
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Performance analysis of different modulation formats in 4-channel CATV transmission system using OADM Amandeep Kaur Dhiman a,∗ , Taranvir Kaur b , Kamaljit Singh b , Kulwinder Singh a a b
Department of Electronics and Communication, Bhai Maha Singh College of Engineering, Sri Muktsar Sahib 152026, India Department of Electronics and Instrumentation, Sri Guru Granth Sahib World University, Fatehgarh Sahib, India
a r t i c l e
i n f o
Article history: Received 11 January 2013 Accepted 23 May 2013
a b s t r a c t In this paper we have analyzed the performance of different modulation formats for a four-channel WDM CATV system using optical ad drop multiplexers and the impact of frequency and wavelength on Q-value, and eye opening is observed for added and dropped channels at different lengths. © 2013 Published by Elsevier GmbH.
Keywords: Optical ad drop multiplexers (OADM) Return to zero (RZ) Non-return to zero (NRZ)
1. Introduction With the recent development optical networks require a variety of new features of which are security and reliability. Since the information carried by the optical carrier is too large and requires features that ensures the signal is always up to the user even in damage whatsoever [1,4]. To meet up the rapid development will require further improvements in the existing optical networks by using OADM (optical add–drop multiplexer). Optical multiplexers are specially designed for WDM (wavelength division multiplexing) systems. The demultiplexers undo the operation which the multiplexers have done. It separates the multiplicity of wavelengths into fiber and directs them to many fibers. Optical multiplexers are used to couple two or more wavelengths into a single fiber. If a demultiplexer and a multiplexer are properly aligned and placed back-to-back, it is clear that in the area between them, two individual wavelengths exist [9,10]. This presents an opportunity for an enhanced function, one in which individual wavelengths could be removed and also inserted. Such a function would be called an optical wavelength add and drop multiplexer/demultiplexer or we can say optical add–drop multiplexer (OADM). The OADM selectively removes (drops) a wavelength from a multiplicity of wavelengths in a fiber, and thus from the traffic on the particular channel. It then adds in the same direction of data flow the same wavelength, but with different data content. Mohammad Syuhaimi Ab-Rahman [1] proposed a paper to do improvements in the function of OADM devices by combining these two devices in parallel. This increases
the reliability of an optical network. Ahmed Nabih Zaki Rashed [2] discussed that the OADM based on DWDM (dense wavelength division multiplexing) technology is moving the telecommunications industry significantly closer to the development of optical networks. The OADM can be placed between two end terminals along any route and be substituted for an optical amplifier. Commercially available OADM allows carriers to drop and/or add up to multi channels between DWDM terminals. By deploying an OADM instead of optical amplifier, service providers can gain flexibility to distribute revenue-generating traffic and reduce costs associated with deploying end terminals at low traffic areas along a route. This paper has proposed OADM for high transmission bit rates at room temperature for best performance efficiency. It is observed that the decreased number of transmitted channels increased the optical transmitted power. Optical Add/drop comprised many optical passive devices such as Fiber Bragg grating, interference filters, circulators and Mach–Zehnder interferometer. Although add/drop filters including those devices have good operating performances, their cost is too expensive to apply for DWDM based optical networks [5,6]. Mohammad Syuhaimi Ab-Rahman [3,8] discussed that wavelength selective add–drop filter is required for adding and dropping a particular wavelength division multiplexing channel at each subscriber’s node in the WDM based optical networks. We came to our results with the help of Simulative analysis of integrated DWDM and MIMO-OFDM system with OADM was done recently for optical-OFDM system [11] and monitoring and compensation of optical telecommunication channels [12]. 2. Simulation setup
∗ Corresponding author. E-mail addresses: [email protected] (A.K. Dhiman), kamal [email protected] (K. Singh), Monga [email protected] (K. Singh). 0030-4026/$ – see front matter © 2013 Published by Elsevier GmbH. http://dx.doi.org/10.1016/j.ijleo.2013.05.094
The main function of an optical multiplexer is to couple two or more wavelengths into single fiber. OADMs are classified as
A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
6811
Fig. 1. Simple optical add–drop multiplexer [G.P. Aggrwal].
Fig. 3. Superimposed eye diagram of 4-channels.
Fig. 4. Superimposed eye diagram of inserted and dropped channel 2.
Q-Value at different modulation formats 35 30 25 20 15 10 5 0
channel 1
The different modulation formats have been compared for 4channel CATV transmission system in the terms of Q value, BER, eye opening, eye closure and jitter. In CATV transmission system we have 4-channel WDM transmitter by which we transmit different modulation format through 4 channels. We find Q-value, BER, eye opening, eye closure and jitter for different modulation format in each channel. Eye diagram for different modulation formats is given (Fig. 3). Electrical scope is used to view the eye diagram of channels. Electrical scope have bit rate 10 Gb/s. It is the bit rate of input signals. Electrical input is given to this component. This component simulates an oscilloscope for electrical signals. It collects data that will be available for eye diagrams (Figs. 4 and 5).
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
3. Results and discussion
NRZ Raised Cosine
channel 2
NRZ Rectangular
Q-Value (dB)
fixed-wavelength and as dynamically wavelength selectable OADMs. In fixed wavelength OADM, the wavelength has been selected and remains the same until human intervention changes it. In dynamically selectable wavelength OADM, the wavelength between the optical multiplexer may be dynamically directed from the outputs of the demultiplexer to any of the inputs to multiplexer. We use ideal optical add–drop multiplexer without optical loss and crosstalk. In simple OADM first component is optical splitter as shown in Fig. 1.This component implements a balanced splitter with the same attenuation on each output. If unbalanced splitter is required, simply follow the splitter with the proper attenuation on each side. If the attenuation is set to 0 dB, this component implements an ideal splitter without any insertion loss, i.e. a component perfectly splits the input signal. Optical filter simulates an optical fiber. In our experiment we use Raised-Cosine-Notch filter. Next component is optical combiner. This component implements a balanced combiner with the same attenuation on each input. If unbalanced combiner is required, simply precede the combiner with the proper attenuation on each input. If the attenuation is set to the default value 0 dB, the component implements an ideal combiner without any insertion loss, i.e. a component that perfectly adds the input signals (Fig. 2).
Channel 3 channel 4
Modulation Formats
Fig. 5. Q-value at different modulation formats in 4-CATV transmission channels.
Optsim simulates the Q-value. Q-value is the ratio of mean and standard deviation of received signals. To have good estimation of Q-value 100–200 bits are simulated so to have a good accuracy on the evaluation of the mean and standard deviation on the received signal. We can set the number of simulated bits at given bit rate (Fig. 6). The evaluation of the BER in optical system simulation is in general a nontrivial task. Error counting is usually impracticable, since the target BER is typically of the order of 109. Therefore to measure
Fig. 2. Germanized block diagram for CATV 4-channel transmission system [Senior].
6812
A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
Q-Value against Wavelength
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
channel 2 Channel 3 channel 4
45 40 35 30 25 20 15 10 5 0
Q-Value (dB)
channel 1
NRZ Rectangular
BER
BER at different modulation formats 6.00E-03 5.00E-03 4.00E-03 3.00E-03 2.00E-03 1.00E-03 0.00E+00
modulation format
Fig. 6. BER at different modulation formats in 4-CATV transmission channels.
NRZ rectangular NRZ raised cosine RZ rectangular RZ raised cosine RZ supergauss ian RZ soliton
1665.5 1620.5 1577.9 1537.4 1499 1199.2 Wavelength (nm)
Fig. 10. Q-value (inserted channel) against wavelength. channel 1
Q-Value against Wavelength
Channel 3
29
channel 4
modulation format
Fig. 7. Eye opening at different modulation formats in 4-CATV transmission channels.
28
RZ rectangular RZ raised cosine
24
RZ supergaussian
23 22
RZ soliton
21 1665.5 1620.5 1577.9 1537.4 1499 1199.2
8 7 6 5 4 3 2 1 0
Wavelength (nm) channel 1
Fig. 11. Q-value (dropped channel) against wavelength.
Channel 3 channel 4
ito n so l RZ
Q-value (dB)
re ct an NR gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
200 250
Q-Value against Frequency 29 28 27 26 25 24 23 22 21
180 185
so l
ito n
190
Z NR
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
NRZ Rectangular
195
Fig. 11 shows the Q-value of dropped channel (channel 2) from OADM against wavelength with decrease in wavelength the Qvalue of RZ raised cosine modulation format decreases from 28 to 26.2 dB. Fig. 12 shows the Q-value of inserted channel (channel 2) in OADM against frequency (THz) for different modulation formats. The diagram shows the Q-value at different frequencies. At all frequencies the Q-value for NRZ rectangular and NRZ raised cosine is rapidly decreasing. For other modulation formats the Q-value increases for all frequencies as shown above. Fig. 13 shows the Q-value of dropped channel (channel 2) from OADM against frequency (THz). The diagram shows the Q-value of
Channel 3
Fig. 9. Jitter at different modulation formats in 4-CATV transmission channels.
190
Fig. 12. Q-value (inserted channel) against frequency.
channel 2
modulation format
185
Modulation format
channel 1
channel 4
180
RZ
Jitter at different modulation formats 0.03 0.025 0.02 0.015 0.01 0.005 0
Q-Value against Frequency
Z
a realistic BER it should be necessary to simulate 1010 bits, a quantity that is not a reasonable value in software simulation. Optsim provides two different components to estimate the transmission performance. Both of them are based on the estimation of some statistical parameters, i.e. Q-value and BER (Fig. 7). The eye opening is the difference between the minimum values of the samples related to logic “1” and the maximum value related to logic “0”, measured at the sampling instant (Fig. 8). The eye closure is defined as by 10 log10 [(average opening)/(opening)]. Eye opening and eye closure values depend on the sampling instant and on the decision threshold. Therefore the eye opening may be evaluated by using the optimum values for sampling instant and decision threshold (i.e. to obtain highest Q or lowest BER) (Fig. 9). The jitter value is the standard deviation of the received RZ signal maximum with respect to the specified sampling instant. The signal maximum depends on the decision threshold; therefore the jitter may be evaluated by using optimum values of the sampling instant and decision threshold (i.e. to obtain highest Q and lowest BER). Fig. 10 shows the Q-value of inserted channel (channel 2) in OADM against wavelength. With decrease in wavelength and Q-value of RZ raised cosine modulation format increases from 25–30 dB. The Q-value of other modulation formats remains almost same as shown in above diagram.
NR
Fig. 8. Eye closure at different modulation formats in 4-CATV transmission channels.
45 40 35 30 25 20 15 10 5 0
Q-Value (dB)
modulation format
re ct an NR gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
channel 2
NRZ Rectangular
Eye Closure (dB)
NRZ raised cosine
25
Eye Closure at different modulation formats
Jitter (ns)
NRZ rectangular
27 26
Q-Value (dB)
RZ Soliton
RZ Super Gaussian
RZ Raised Cosine
RZ Rectangular
NRZ Raised Cosine
channel 2
NRZ Rectangular
Eye Opening (au)
Eye Opening at different modulation formats 0.005 0.004 0.003 0.002 0.001 0
modulation format
Fig. 13. Q-value (dropped channel) against frequency.
195 200 250
0.003
RZ raised cosine
0.002
RZ supergauss ian
0.001
RZ soliton
185 190
NR
1666 1620 1578 1537 1499 1199
Fig. 17. Eye opening (dropped channel) against frequency.
Fig. 14. Eye opening (inserted channel) against wavelength.
Eye Opening against Wavelength
Jitter against Wavelength 0.03
0.007
NRZ rectangular
0.006 0.005
NRZ raised cosine RZ rectangular
0.004
RZ raised cosine
0.003
RZ supergauss ian
0.002 0.001
0.025
Jitter (ns)
RZ soliton
NRZ rectangular NRZ raised cosine
0.02
RZ rectangular
0.015
RZ raised cosine
0.01
RZ supergauss ian
0.005
0
RZ soliton
0 1666 1620 1578 1537 1499 1199
1666 1620 1578 1537 1499 1199
Wavelength (nm)
Wavelength (nm)
Fig. 15. Eye opening (dropped channel) against wavelength.
Jitter against Wavelength 0.025 NRZ rectangular
jitter (ns)
0.02
NRZ raised cosine 0.015
RZ rectangular RZ raised cosine
0.01
RZ supergauss ian 0.005
RZ soliton
0 1666 1620 1578 1537 1499 1199 Wavelength (nm)
Fig. 19. Jitter (dropped channel) against wavelength.
ito n so l RZ
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
200 250
NR
0.025 0.02 0.015 0.01 0.005 0
NR
250
so l
ito n
190
Z
200
185
RZ
195
180
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
190
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n RZ so lito n
195
Fig. 20. Jitter (inserted channel) against frequency.
Jitter (ns)
185
Z
190
Jitter against frequency
180
NR
185
Modulation formt
Eye Opening Against Frequency 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0
180
Z
Jitter (ns)
Jitter against frequency 0.03 0.025 0.02 0.015 0.01 0.005 0
NR
different modulation formats at different frequencies. At 185 THz RZ raised cosine has maximum value of 28 dB. Fig. 14 shows the eye opening of inserted channel (channel 2) in OADM against wavelength at 1620 nm wavelength RZ soliton modulation format has maximum value 0.006 a.u. NRZ raised cosine modulation format has lowest eye opening. Fig. 15 shows the eye opening of dropped channel (channel 2) from OADM. RZ soliton has lowest eye opening at 1620 nm wavelength. Fig. 16 shows the eye opening of inserted channel (channel 2) in OADM against frequency. The diagram shows the eye opening of different modulation formats at different frequencies. At 185 THz RZ soliton has maximum eye opening. Fig. 17 shows the eye opening of dropped channel (channel 2) from OADM against frequency. At 180 THz RZ raised cosine has maximum eye opening. Fig. 18 shows the jitter value of inserted channel (channel 2) in OADM against wavelength. RZ soliton has minimum jitter value as shown in the diagram. Fig. 19 shows the jitter value of dropped channel (channel 2) from OADM. RZ soliton has minimum jitter value as shown in the diagram. Fig. 20 shows the jitter value of inserted channel (channel 2) in OADM against frequency. Above diagram shows the jitter value of different modulation formats at different frequencies. RZ soliton
Fig. 18. Jitter (inserted channel) against wavelength.
NR
Eye Opening (a.u)
0.008
Eye Opening (a.u)
250
Modulation format
Wavelength (nm)
NR
195 200
Z
0
180
ito n
RZ rectangular
so l
NRZ raised cosine
0.004
RZ
NRZ rectangular
0.005
Eye Opening against Frequency 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0
NR
Eye Opening (a.u)
0.006
6813
re ct an gu la Z r ra ise d co si ne RZ re ct an gu RZ la ra r ise d c os RZ in su e pe rg au ss ia n
Eye Opening against Wavelength 0.007
Eye Opening (a.u)
A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
Modulation format
Modulation format
Fig. 16. Eye opening (inserted channel) against frequency.
Fig. 21. Jitter (dropped channel) against frequency.
195 200 250
6814
A.K. Dhiman et al. / Optik 124 (2013) 6810–6814
Q-Value (dB)
Q-Value against Distance 45 40 35 30 25 20 15 10 5 0
Channel 1 Channel 2 Channel 3 Channel 4 Inserted Channel
modulation format has maximum Q-value, that is 40 dB. When this channel has dropped from OADM has 25 dB Q-value. RZ soliton has maximum eye opening. Jitter value of RZ Raised Cosine is increases with increase in wavelength. Jitter remains same for other modulation formats with increase in wavelength. Q-value decreases with increase in fiber length.
Dropped Channel
References 50
100
150
Distance (Km)
Fig. 22. Q-value against distance.
has the minimum jitter value at all frequencies as shown in the diagram. Fig. 21 shows the jitter value of dropped channel (channel 2) from OADM against frequency. RZ modulation formats have less jitter value as shown in the diagram. Fig. 22 shows the Q-value against distance. Q-value decreases as we increase the distance as shown in above diagram. At 150 km channel 3 has less Q-value. 4. Conclusion Different modulation formats have been compared for 4channels of CATV transmission system. Q-value (dB) is decreased due to fiber non-linearities. The better Q-value is provided by the RZ Rectangular modulation format in channel 2. RZ Raised Cosine have high BER rate. NRZ Rectangular gives the better performance because it has high eye opening and less eye closure. This paper concluded that with decrease in wavelength there is no change in Q-value of Inserted channel 2 in OADM. NRZ Rectangular
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