2.ijaest-vol-no-7-issue-no-1-investigations-on-scm-catv-transmission-link-with-and-without-fiber-bra

Investigations on SCM-CATV Transmission link with and without Fiber Bragg Grating

ASHISH MALHOTRA, NEERU MALHOTRA, LOVE KUMAR, AARTI KOCHHER

Department of Electronics and Communication DAV institute of Engineering and Technology

Jalandhar, India [email protected],[email protected],

Abstract: - In this paper, performance SCM-CATV transmission

link is compared with and without FBG on the basis of Eye

opening, BER, Q factor and Jitter. The technique is applied for

PSK data format which operates at data rate of 10Gbps for 8 RF

frequency ranging from 0.002 to 0.0034 THz with uniform

spacing of 0.0002 THz. Result are reported on different fiber

lengths from 20 to 100 km. The analysis shows that FBG

technique improved the performance of system as it is observed

the Eye opening of system is similar with FBG. The FBG vary the

BER from 1.41e-008 to 7.53e-006 and Q factor from 8.71e-004 to

8.04e-004 at 100 km

Keywords: - SCM-CATV, BER, Q- factor

I. INTRODUCTION

In the information age, we are seeing a relentless demand for networks of higher capacities at lower costs. Concepts for broadband systems have been discussed since a long time however, recently through buzzwords such as “internet”, “communication highway” and “multimedia”, The discussion about interactive broadband services, especially those for residential customers has been so accelerated worldwide that the society has become an information society. New approaches have been attempted for further development of broadband distribution services and applications. Over the past three decades, the advancements in optical fiber has undoubtedly improved and reshaped fiber-optic technology. Today, optical fibers are synonymous with the word „„telecommunication. An all optical connection for the residential customer is presented. It is based on a fiber sharing topology, providing telephony or ISDN and TV services. Two fibers per customer are provided, one carrying 40 TV channels, the other ISDN with Wavelengths of 1.55~ and 1.3~ respectively are used for these services. Erbium doped fiber amplifiers (EDFA) are used for TV distribution. The

telephony system employs SCM (subcarrier multiplex) and is designed for easy upgrading to 2 Mb/s per customer [1,3] Creation of a SCM-CATV link is the key step that will enable computer-mediated communications. It is a desirable alternative to the current fragile and bandwidth-limited Internet. It sidesteps the slow response of the telecommunications industry to data communications needs. . Optical subcarrier multiplexing (SCM) is a scheme where multiple signals are multiplexed in the radiofrequency (RF) domain and transmitted by a single wavelength. A significant advantage of SCM is that microwave devices are more mature than optical devices; the stability of a microwave oscillator and the frequency selectivity of a microwave filter are much better than their optical counterparts. In addition, the low phase noise of RF oscillators makes coherent detection in the RF domain easier than optical coherent detection [4]. In order to optimize the system performance, tradeoffs must be made between data rate per subcarrier, levels of modulation, channel spacing between subcarriers, optical power, and modulation indexes. A 10-Gb/s SCM test bed has been set up in which 4 2.5 Gb/s data streams are combined into one wavelength that occupies a 20-GHz optical bandwidth. OSSB modulation is used in the experiment [5,6]

Fig.1 Block diagram of SCM optical system

ASHISH MALHOTRA* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 7, Issue No. 1, 010 - 016

ISSN: 2230-7818 @ 2011 http://www.ijaest.iserp.org. All rights Reserved. 0

IJAEST

A popular application of SCM technology in fiber optic systems is analog cable television (CATV) distribution Because of the simple and low-cost implementation the 87% of the homes in the United States are already passed by a broad-band coaxial television (CATV) network, coaxial technology. Optical fiber offers a high bandwidth, low-loss transmission medium which has the potential to allow significant performance improvement in today‟s cable television networks.(7) The SCM CATV suffers from dispersion the FBG reduce the effect of dispersion. The Fiber Bragg Grating (FBG) is a fiber optic passive component exhibiting basic functional attributes of reflection and filtering. FBG‟s have replaced bulk optic mirrors & beam splitters in equipment which increases system stability and portability.FBG provide periodic perturbation of the refractive index along the fiber length which is formed by exposure of the core to an intense optical interference pattern. The formation of permanent gratings in an optical fiber was first demonstrated by Hill et al. in 1978 at the Canadian Communications Research Centre (CRC), Ottawa, Ont., Canada they Confirmed that a very narrowband Bragg grating filter had been formed over the entire 1-m length of fiber. This achievement, subsequently called “Hill gratings,” was an outgrowth of research on the nonlinear properties of Germania-doped silica fiber. It established an unknown photosensitivity of Germania fiber, which prompted other inquires, several years later, into the cause of the fiber photo-induced refractivity and its dependence on the wavelength of the light which was used to the form the gratings.[8,10]

II. SIMULATION SETUP

The Simulation setup for SCM-CATV transmission link shown in fig(1). The transmitter section having 8 RF frequencies ranging from 0.002 to 0.0034 THz with uniform spacing of 0.0002 THz. These channel are combined by using electric combiner. The 8 combined channel are optically modulated using MZ modulator and continuous Wave laser at optical carrier freq of 193.41 THz. A bias wave generator is used for providing biasing voltage of 2.5 au to MZ modulator. The optical fiber used as transmission media.

The optical modulated signal travel through the fiber length of the system varied from 20-100 km for investigate the performance of system. A 15dB optical gain is provided by using EDFA to minimize the effect of attenuation of the signal. The EDFA amplify the optical modulated signal. Splitter split the optical signal into two equal parts. The one part fed to receiving section through FBG and one directly fed to Receiver. The receiving section having PIN photodiode at frequency 193.41THz to convert optical signal to electrical

signal this electrical signal is filtered by using Bessel filter. The various electrical and optical visualize has been used in simulation setup to analyze the performance of SCM-CATV Transmission link system.

Fig.2 SCM-CATV Transmission Links Simulation setup

III. SIMULATION RESULT

The simulation results for SCM-CATV Transmission link are categorized in three parts

1) Without FBG 2) With FBG 3) Comparison between without and with FBG

1. WITHOUT FBG

The Investigation of SCM-CATV Transmission link has been reported on the basis of EYE diagram, scattering diagram, BER, Jitter and Q Value at different fiber lengths

Fig. 3a


ISSN: 2230-7818 @ 2011 http://www.ijaest.iserp.org. All rights Reserved. Page 11

IJAEST

Fig. 3b

Fig. 3c

Fig. 3d

Fig. 3e

Fig-3(a) Eye diagram at 20Km, (b) Eye Diagram at 40Km, (c) Eye Diagram at 60km (d) Eye Diagram at 80 Km ( e) Eye Diagram at 100 Km Due to span losses, the eye opening of system degrades as the fiber length increases. The maximum and minimum value of eye opening is 3.08e-006 at 20 km and 2.42e- 007 at 100 km without using FBG.

Fig. 4a

Fig 4b

Fig. 4c



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0

0.0000001

0.0000002

BER

Distance

Fig. 4d

Fig. 4e

Fig-4a) scattering diagram at 20 Km, ( b) Scattering Diagram at 40 Km, (c) Scattering Diagram at 60 Km (d) Scattering Diagram at 80 Km , (e) Scattering Diagram at 100 Km

Fig.5 BER value at Fiber length 20,40,60,80 and 100 Km

Fig-6 Jitter at Fiber length 20,40,60,80 and 100 Km

Fig-7 Q-value at Fiber length 20,40,60,80 and 100 Km The BER, Jitter and Q-factor increases as the Fiber length increases due to span loses. Minimum and maximum value of BER is 1.1e-008 and 2.3e-037.Minimum and maximum value of Jitter is 4.3 and 4.7.Minimum and maximum value of Q-factor is 4 and 13.

2. WITH FBG

The Investigation of SCM-CATV Transmission link has been reported on the basis of EYE diagram, scattering diagram, BER, Jitter and Q Value at different fiber lengths from 20 km to 100 km.

Fig.8a



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Fig.8b

Fig.8c

Fig.8d

Fig. 8e

Fig-2( a) Eye diagram at 20 Km, b) Eye Diagram at 40 Km, c) Eye Diagram at 60 d) Eye Diagram at 80 Km, e) Eye Diagram at 100 Km Due to span losses, the eye opening of system degrades as the fiber length increases. The maximum and minimum value of eye opening is 3.08e-006 at 20 km and 2.42e-007 at 100 km without using FBG

Fig. 9a

Fig. 9b

Fig. 9c



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02468

101214

20Km

40KM

60Km

80Km

100Km

Q-v

alu

e

Distance

Fig 9d

Fig. 9e

Fig 9(a) Scattering diagram at 20 Km, (b) Scattering diagram at 40 Km, (c) Scattering diagram at 60 Km (d) Scattering diagram at 80 Km,(e) Scattering diagram at 100 Km

Fig-10 BER value at Fiber length 20,40,60,80 and 100 Km

Fig- 11 Jitter at Fiber length 20,40,60,80 and 100 Km

Fig- 12 Q-value at Fiber length 20,40,60,80 and 100 Km

The BER decreases with length the Minimum and maximum value of BER is 1.3e-023 and 7.53e-006 , Q-factor decreases as the Fiber length increases the Minimum and maximum value of Q-value is 12.850 and 20.081.The value of jitter fluctuates initially between 20 to 60 km then it starts decreasing as length is increased.

3. Comparison between without and with FBG

Table:-1 SCM-CATV Transmission Link Without FBG

0

5E-10

1E-09

BER

Distance (Km)

Paremeters

/distance

20

KM

40

KM

60 km 80KM 100

KM

BER 1.06e-025

2.27e-025

1.21e-012

5.22e-012

1.41e-006

Q-Value

(db)

13.41 16.85 17.10 20.41 20.35

Jitter

(ns)

5.283 5.538 4.70 5.60 5.15

Eye-

Opening

1.21e-004

1.22e-004

1.25e-004

1.29e-004

8.71e-004

0

5

20Km

40KM

60Km

80Km

100Km

Jitt

er

Distance



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Table:-2 SCM-CATV With FBG The comparison Analysis of SCM-CATV transmission link without and with FBG shown in table 1 and 2.The system is compaired on the baises of eye opening BER,Q Factor and jitter. The analysis shows that FBG technique improved the performance of system and provide the improved values.

IV CONCLUSION: -

The analysis of SCM-CATV Transmission link with and without FBG as in table 1 and 2 shows that FBG technique improved the performance of system, This technique vary the BER from 1.06e-025 to 1.30e-023 at 20km and 1.41e-008 to 7.53e-006 at 100km, While the Q-factor varied from 20.354db to 20.081db at 20 km and 13.410db to 12.850db at 100km.The eye opening vary from 1.21e-004 to 1.12e-004 at 20km and 8.71e-004 to 8.04e-004.The jitter vary from 5.283ns to 5.535ns at 20km and 5.152ns to 4.94ns at 100 km.

V REFERENCES:-

1 Gerhard Gobl, Carl Lundquist, Bernd Hillerich, Mark Perry(1989), “Fibre to the Residential Customer” IEEE Journal of Selected Areas in Communication.

2 Kyoungsoo Kim, Jaehoon Lee, and Jichai Jeong,(2009)” Performance Limitations of Subcarrier Multiplexed WDM Signal Transmissions Using QAM Modulation” Journal of Lightwave Technology, vol.27,no.18

3 Yogesh Chaba and R.S. Kaler (2010) “Comparison of various dispersion compensation techniques at high bit rates using CSRZ format” ”, Optics Communications, vol. 121, pp. 813-817. .

4 Brooks, J. L. Maurer, G. S. and Becker, R. A. (1993), “ Implementation and evaluation of dual parallel linearization system for SCM system”, Journal of Light wave Technology, vol.11, pp. 34-41.

5 Zhu, B. Huang, R. Allen, C. T. (2002), “Subcarrier multiplexing for high speed optical transmission”, Journal of Lighwave Technology ,vol 20, 3, pp. 417-427.

6 E. A. Flood, “Demonstration of 20 Gbits/s subcarrier multiplexed transmission system.” Electronics Letters vol. 38, no. 9, April 2002.

7 Chiddix, J. A. loar, H. Pangrac, M. Williamson, L. D. Wolfe, R .W. (1990 ), “AM video on fiber in CATV system”, IEEE Journal of Selected Areas in Communication, vol. 8 , 7 , pp. 1229-1239

8 Hill, K. O. and Meltz, G. (1997), “Fiber grating technology and overview”, Journal of Lightwave Technology, vol. 15, 8, pp. 1263-1276.

9 Yeh, C. and Chi, S. (2005), “Utilizations of fiber Bragg gratings and Fabry–Perot lasers for fast wavelength switching technique”, Optics Communications, vol. 256, 1-3, pp. 73-77.

10 Ngo, N. Q. Li, S. Y. Binh, L. N and Tjin, S. C. (2006), “A phase-shifted linearly chirped fiber Bragg grating with tunable bandwidth”, Optics Communications, vol. 260, 2, pp. 438-44.

11 Brooks, J. L. Maurer, G. S. and Becker, R. A. (1993), “ Implementation and evaluation of dual parallel linearization system for SCM system”, Journal of Light wave Technology, vol.11, pp. 34-41.

Paremeters

/distance

20

KM

40

KM

60 km 80KM 100

KM

BER 1.30e-023

2.24e-012

1.61e-011

4.62e-006

7.53e- 006

Q-Value

(db)

20.081 16.833 16.451 13.031 12.850

Jitter

(ns)

5.535 4.427 5.299 5.260 4.94

Eye-

Opening

1.12e-004

1.12e-004

1.16e-004

1.11e-004

8.04e-004



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