A STUDY ON RAYLEIGH BACKSCATTERING NOISE IN SINGLE FIBER TRANSMISSION PON

A STUDY ON RAYLEIGH BACKSCATTERING NOISE IN SINGLE FIBER TRANSMISSION PON Joni Welman Simatupang, Preident Univerity, Bekai, Indoneia; Shu-Chuan Lin, National Taiwan Univerity of Science and Technology, Taipei, Taiwan Abtract In thi paper, we meaured the ditributed Rayleigh backcattering (RB) noie along the length of the fiber optic network by a certain method. Rayleigh backcattering noie which i generated by ome ditributed reflection of random index fluctuation along the optical fiber may caue evere degradation problem in bidirectional tranmiion performance of paive optical network (PON) ytem. Some experiment have been conducted to tudy the RB noie impairment by meauring the total detected backcattered power in ingle fiber tranmiion uing power meter. Then thee reult were extracted to find the RB noie a a function of fiber length. Common calculated reult that were publihed everywhere wa verified by our meaurement reult how that the average RB noie i about -32 db with about 1 db dicrepancy for 25-115 Km fiber tranmiion for about 0 dbm launched input optical power. The modulated DFB laer diode by 10 Gb/ data rate on-offkeying ignal (OOK) for amplitude modulation wa ued a an optical tranmitter. We believe that our imple architecture can be deployed to build a more complex ytem network for the future bidirectional tranmiion in the long reach wavelength diviion multiplexing-paive optical network (LRWDM-PON) ytem. Keyword: Rayleigh backcattering (RB) noie, optical fiber, paive optical network (PON), bidirectional tranmiion. Introduction The major motivation behind the ue of ilica optical fiber (Figure 1) i the large bandwidth offered by fiber optic communication ytem. However, intrinic lo hinder the utility of optical fiber to the maximum level [1]. So, it hould be treated in uch a way that it will not much degrade the performance of the ytem by certain method of reduction [2-]. Baically, there are three major loe mechanim in GeO 2 -doped fued ilica optical fiber: (1) intrinic and extrinic aborption loe, (2) elatic and inelatic cattering loe, (3) macro- and micro-bending loe. In thi reearch work, we focued our tudy on the elatic cattering loe only, in order to narrowing our cope. We hope that the reult of thi tudy will be ueful in the future for Rayleigh backcattering (RB) noie mitigation cheme in the bidirectional and loop-back tructure of WDM-PON tranmiion ytem. The ret of the paper i organized a follow. The econd part decribe the baic mechanim of cattering loe, it theoretical formula, and the RB noie decription in a bidirectional loop-back tranmiion ytem. The third part i given to the experiment and meaurement reult. Finally, the lat part conclude the main reult of the paper. Figure 1. Two kind of ilica optical fiber baed on their core/cladding diameter [1]. Baic Mechanim Elatic Scattering Loe The cattering of light may be thought of a the redirection of light that take place when an electromagnetic (EM) wave (i.e. an incident light ray) encounter an obtacle or non-homogeneity dicrete particle [5, 6]. When cattering particle are very mall compared to the wavelength of incident radiation, which i r < /10, the cattered intenity on both forward and backward direction are equal. Thi type of cattering i called the Rayleigh cattering. In thi type of cattering, the cattered intenity varie inverely a the fourth power of wavelength. For larger particle (r > /10), the angular ditribution of cattered intenity become more complex with more energy cattered in the forward direction. Thi type of cattering i called the Mie cattering. In Rayleigh and Mie cattering, both the cattered and incident radiation have the ame wavelength and hence, thi two cattering proce are called the elatic cattering. In elatic cattering (epecially Rayleigh cattering), the frequency (or the photon energy) of the cattering light will remain unchanged. The mechanim of thi cattering doen t caue the elimination or converion of optical ener- 11

gy, but imply force a part of optical wave ecaping from the waveguide. By contrat, during the inelatic cattering [timulated Brillouin cattering (SBS) arie when a trong optical ignal generate an acoutic wave that produce variation in the refractive index, and timulated Raman cattering (SRS) arie when there i an interaction between lightwave and the vibrational mode of ilica molecule], the frequency of the cattered light i hifted downward (The cattered wave i downhifted in frequency. It i called a Stoke wave after George Stoke, who found the frequency downhift in the proce of luminecence in the 19 th century). (0.76 0.51n) db ( / m) Km (1) The numerator could be ubtituted by C with value range from 0.70.9 [(db/km).m ]. So, the equation above will be implified to be: C (2) for =1550 nm, varie from 0.120.16 db/km. Actually, there i alo another formula to calculate the Rayleigh cattering loe in optical fiber [7]. For pure ilica gla an approximate equation for the Rayleigh cattering lo i given by thi equation: 0 ( ) 0 (3) where α 0 = 1.6 db/km at 0 = 850 nm. Thi formula predict cattering loe of 0.291 db/km at 1310 nm and 0.18 db/km at 1550 nm. A we can ee, all equation give the ame range value for, o either way can be ued to calculate the Rayleigh cattering loe in optical fiber. Rayleigh Backcattering Noie Meauring the ditribution of the light cattered in the backward direction a a function of fiber length down a fiber-optic aembly alo can be ueful in identifying break, bad plice, and non-reflective event [8]. Rayleigh backcattered light had benefited function in optical fiber enor [9-11], but optical loe due to Rayleigh backcattering (RB) in optical fiber have caued a coniderable problem in optical communication ytem. Some invetigation of noie due to RB have been preented in many area, uch a fiber-optic gyrocope baed on Rayleigh backcattering in a fiber-ring reonator [12], light backcattered from aborbing olution illuminated by a giant-pule ruby laer [13], the direct obervation of backcattering induced by idewall roughne in high-index contrat optical waveguide baed on total internal reflection [1], Rayleigh cattering act a an equivalent mirror which can generate high level of multiple reflection noie in lightwave ytem employing optical amplifier [15], in uing the backcattering fluctuation a fiber ignature [16], to etimate the optical lo in acrylic polymer by theoretical modification [17] and alo in bidirectional optical communication and wavelength-reue fiber ytem [18-22]. In a bidirectional ytem, data i tranmitted in both direction over a ingle fiber (Figure 2). If we compared with the unidirectional ytem, bidirectional ytem will reduce the number of fiber and enhance the efficiency of bandwidth uage twice by uing the ame wavelength for both downtream and uptream tranmiion in a wavelengthreue ytem. However, the ytem will be more enitive to RB effect and alo SBS and SRS and other fiber nonlinearitie due to the higher power level in the ytem. For bidirectional optical ytem which are employing ingle mode laer diode, RB noie may caue coniderable receiver enitivity degradation. In fact, typically RB lo of about -31 to about -33 db of the 0 dbm launched optical power to the 20 Km feeder fiber can t be avoided. RB in the tranmiion fiber mut be taken into account when we calculated the performance of the bidirectional tranmiion ytem, epecially in a wavelength-reue ytem (loop-back acce configuration or re-modulation cheme). Thu in thi cae, RB noie ha become a limiting factor that cauing ytem impairment in bidirectional optical communication. i INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY & SCIENCE VOLUME, NUMBER 3, MAY 2016 A Figure 2. A bidirectional tranmiion ytem with wavelength reue mechanim, where i = k. k Experiment and Reult Here, we performed experiment to verify the calculated reult that publihed everywhere, by adopted imple meaurement etup of PON (paive optical network) uptream tranmiion link [23] which i hown in Figure 3. The backcatter factor i the ratio of the backcattered power to the energy launched into the fiber, which i important in long-range fault location ince it determine the magnitude of the ignal and hence the range which the apparatu can cover. DFB laer diode wa modulated with 10 Gb/ data rate PRBS (peudo-random-binary-equence) 2 31-1 on-offkeying ignal (OOK) before injected into the ingle optical fiber. Optical circulator wa placed in between the laer ource and optical fiber to manage the data traffic of ignal get into and reflected back from the drop fiber tranmiion. Optical circulator i a non-reciprocal multi-port paive device that direct light equentially from port to port in only B 12

one direction. Either it i port 1, port 2, and port 3 can be ued a input and output, depend on which direction the light come and goe. Power meter wa ued to meaure the total detected backcattered power becaue thi equipment can meaure the total output power preciely, rather than OSA (optical ignal analyzer). To avoid reflection, angle connector wa placed at the terminated end of the fiber. After the ignal entered the fiber through optical circulator, then the downtream (forward) ignal experience the cattering along the optical fiber due to fiber nonuniformitie when manufacturing time. Some amount of the cattering light then travelling back to the previou direction it goe before, which i then detected by power meter. Thi i the total backcattered power. The ret of the light ignal goe toward the angled connector and terminated with APC (angled phyical contact) connector. To ee the effect of Rayleigh backcattering in different ditance, we changed the length of fiber by cacading each pool with 10, 20, or 25 Km different length a available in Optical Network Laboratory (ONL)-03. Table 1 and 2 how the meaurement reult of total backcattered power a a function of input optical power and Rayleigh backcattering (RB) noie a a function of fiber length, repectively. For optical fiber ytem, laer ource ued almot excluively are emiconductor laer diode. LD Controller DFB LD PPG 10Gb/ (OOK Signal) Rayleigh Backcattering (RB) Optical Circulator Power Meter Drop Fiber: 25 115 Km Figure 3. Experimental etup to meaure the Rayleigh Backcattering (RB) noie in ingle fiber tranmiion. So, here we ued DFB (ditributed feedback) laer diode with the center wavelength,= 1538.2 nm and SMSR (ide mode uppreion ratio) 38 db. It wa biaed at current 5 ma and temperature controlled 20 o C ued for optical tranmitter, modulated by OOK ignal with 0.25 V tep (0.25 V, 0.5 V, 0.75 V) produced varied input optical power about ~0 dbm. The average Rayleigh backcattering noie from our experiment i about -32 db for different fiber length varie from 25-115 Km fiber length. Thi reult can be a proof that thi value i agreed or matched with our advanced prediction. Angled connector Table 1. Meaurement of total backcattered power a a function of input optical power. (Aumption: fiber connector and other equipment loe are negligible) OOK Signal Detected Backcattered Optical Power (dbm) Input Optical Power (dbm) 25 km 35 km 55 km 80 km 105 km 115 km (V) 0.25 0.77-32.236-31.998-31.862-31.87-31.85-31.829 0.50 0.808-32.206-31.970-31.836-31.81-31.812-31.808 0.75 0.829-32.196-31.956-31.819-31.799-31.797-31.795 Table 2. Meaurement of total Rayleigh backcattering (RB) noie a a function of fiber length. (Aumption: fiber connector and other equipment loe are negligible) OOK Signal Rayleigh Backcattering noie (db) (V) 25 km 35 km 55 km 80 km 105 km 115 km 0.25-33.010-32.772-32.636-32.621-32.619-32.603 0.50-33.01-32.778-32.6-32.622-32.620-32.616 0.75-33.025-32.785-32.68-32.628-32.626-32.62 13

Concluion Rayleigh backcattering phenomena i an intrinic lo or noie that alway preent (exit) in the tranmiion ytem. Bidirectional tranmiion i typically implemented in a loopback configuration in which the eed light and uptream ignal operate at the ame wavelength and travel in oppoite direction within the ame fiber. In our imple experiment, we ued different fiber length to repreent the different tranmiion link (vary from 25 Km to 115 Km). For tranmiion link longer than 20 Km, RB noie achieve about (average) -32 db depending on the input optical power for certain laer wavelength. We believe that our imple etup can be employed (extended) to build the complex architecture for future bidirectional acce network or long-reach WDM-PON ytem. Acknowledgment Author would like to thank Dr. San-Liang Lee for hi valuable dicuion and generoity in providing ome facilitie for u for doing ome experiment in ONL-03. Reference [1] K.. Tujikawa, K.. Tajima, and J. Zhou, Intrinic lo of optical fiber, Optical Fiber Technology Vol (11), pp. 319-331, 2005. [2] J. Prat, Rayleigh Back-cattering reduction by mean of Quantized Feedback Equalization in WDM-PON, Th.10.B.3, ECOC 2010, Torino, Italy. [3] J.-M. Lee, D.-W. Lee, S.-J. Park, and S.-K. Han, Reduction of Rayleigh Back-Scattering Noie Uing RF Tone in RSOA Baed Bidirectional Optical Link, JThA98.pdf, OFC/NFOEC 2008, USA. [] U. H. Hong, Cho, K. Y., Takuhima, Y., and Y. C. Chung, Effect of Rayleigh Backcattering in Long-Reach RSOA-Baed WDM-PON, OThG1.pdf, OSA/OFC/NFOEC 2010. [5] D. W. Hahn, Light Scattering Theory, July 2009. [6] Liebl, M., Blue Skie, Coffee Creamer, and Rayleigh Scattering, The Phyic Teacher, Vol (8), May 2010, pp. 300-301. [7] G. Keier, Optical Fiber Communication, Fouth Edition, Mc Graw Hill, 2010. [8] B. J. Soller, M. S. Wolfe, and M. E. Froggat, Polarization reolved meaurement of Rayleigh backcatter in fiber-optic component, OFC Technical Diget, paper NWD3, 2005. [9] D. K. Gifford, B. J. Soller, M. S. Wolfe, and M. E. Froggat, Ditributed Fiber-Optic Temperature Sening uing Rayleigh Backcatter, ECOC 2005. [10] K. Peter, Polymer optical fiber enor a review, Smart Mater. Struct. Vol (20), 17pp. 2011. [11] S. T. Kreger, A. K. Sang, D. K. Gifford, and M. E. Froggatt, Ditributed train and temperature ening in platic optical fiber uing Rayleigh catter, Proc.of SPIE Vol (7316), pp.1-8, 2009. [12] A. Kung, J. Budin,, L. Thevenaz, and Ph. A. Robert, Rayleigh Fiber Optic Gyrocope, IEEE Photonic Technology Letter, Vol (9), pp. 973-975, 1997. [13] C. W. Cho, N. D. Foltz, D. H. Rank, and T. A. Wiggin, Stimulated Thermal Rayleigh Scattering in Liquid, Phyical Review, Vol (175), pp. 271-275, 1968. [1] F. Morichetti, Roughne Induced Backcattering in Optical Silicon Waveguide, Phyical Review Letter, Vol (10), pp. 1-, 2010. [15] J. L. Gimlett, M. Z. Iqbal, N. K. Cheung, A. Righetti, F. Fontana, and G. Grao, Obervation of Equivalent Rayleigh Scattering Mirror in Lightwave Sytem with Optical Amplifier, IEEE Photonic Technology Letter, Vol (2), pp. 211-213, 1990. [16] M. Brodky, J. Oh, M. Tur, and P. S. Henry, Rayleigh backcattering from optical fibercould it be ued to identify individual fiber?, Optical Society of America (OSA), 2010. [17] J. K. Kim, and D. H. Suh, Etimation on the optic lo for acrylic polymer by theoretical modification, Journal of Fluorine Chemitry, Vol (125), pp. 369-375, 200. [18] S.-K. Liaw, S.-L. Tzeng, and Y.-J. Hung, Rayleigh backcattering induced power penalty on bidirectional wavelength-reue fiber ytem, Optic Communication 188, pp. 63-67, 2001. [19] R. K. Staubli, and P. Gyel, Crotalk Penaltie Due to Coherent Rayleigh Noie in Bidirectional Optical Communication Sytem, Journal of Lighwave Technology, Vol (9), pp. 375-380, 1991. [20] J. W. Simatupang, Simulation and Analyi of Rayleigh Backcattering Effect in 105 Km Long- Reach RSOA-baed Hybrid WDM/TDM PON Tranmiion, Jurnal Teknologi Indoneia LIPI, 36 (1), pp. 1-9, 2013. [21] M. Xu, Y.-C. Chi, J. Wang, L. Cheng, F. Lu, Md. I. Khalil, C.-T. Tai, G.-R. Lin, and G.-K. Chang, Wavelength Sharing and Reue in Dual-Band WDM-PON Sytem Employing WRC-FPLD, IEEE Photonic Technology Letter, Vol. 27 (17), pp. 1821-182, 2015. INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY & SCIENCE VOLUME, NUMBER 3, MAY 2016 1

[22] J. W. Simatupang and S.-L. Lee, Tranfer matrix analyi of backcattering and reflection effect on WDM-PON ytem, Opt. Exp., Vol. 21 (23), pp. 27565-27577, Nov. 2013. [23] J. J. Martinez, I. Garce, M. A. Loada, A. Lopez, and A. Villafranca, Analyi of backcattered optical ignal in narrow pectrum remote feeding ingle-fibre link employing RSOA, ECOC 2007. broadband local acce network, WDM-PON, emiconductor optoelectronic device, and high peed optical tranmiion ytem. Now, Dr. Lin i working and doing reearch with Mackay Memorial Hopital of Taipei, Taiwan. Biographie JONI WELMAN SIMATUPANG wa born in Padangidimpuan, North Sumatera, Indoneia. He received Bachelor degree in Electrical Engineering from the Univerity of Indoneia (UI) Depok, Wet Java, in 2003. Since October 2003, he worked for four year in Perkanta Jakarta Foundation, an NGO (non-governmental organization) where doing diciplehip and leaderhip training for Chritian tudent fellowhip in univerity and alo high chool in Indoneia. After that, in 2007 he joined the Device Semiconductor Optoelectronic then the Optical Network Laboratory (ONL) Group of Electronic and Computer Engineering (ECE) Department for graduate program where he finihed hi Mater and PhD degree in Electronic Engineering from National Taiwan Univerity of Science and Technology (NTUST) - Taiwan Tech, Taipei, Taiwan under the uperviion of Prof. San-Liang Lee in 2009 and 201, repectively. Currently, Dr. Joni i teaching at the Electrical Engineering Study Program, Faculty of Engineering, Preident Univerity, Bekai, Indoneia. Hi reearch interet include the bidirectional wavelength diviion multiplexing paive optical network (Bidi WDM-PON), optical injection locking (OIL), emiconductor laer optoelectonic, biophotonic, light emitting diode (LED), renewable energy reource, and mart ytem. Hi recent work are mainly focued on bidirectional ingle-fiber ingle-wavelength (SFSW) tranmiion over conventional, cro-eeding, and longreach WDM-PON ytem. He maybe reached a correponding author at joniwmtp@preident.ac.id. SHU-CHUAN LIN wa born in Taipei, Taiwan. She received the B.S., M.S., and Ph.D. degree in Electronic Engineering from the Department of Electronic Engineering and the Graduate Intitute of Electro-Optical Engineering, National Taiwan Univerity of Science and Technology (NTUST), Taipei, Taiwan, in 1998, 2000, and 2008, repectively. Since 2008 until 2011, he ha been a potdoctoral fellow with the Department of Electronic Engineering, NTUST. Her reearch interet include 15