Design of Passive Optical Network Monitoring System Based on Optical Frequency Domain Reflectometer using Various Types of Fiber Bragg Gratings

Design of Passive Optical Network Monitoring System Based on Optical Frequency Domain Reflectometer using Various Types of Fiber Bragg Gratings | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Design of Passive Optical Network Monitoring System Based on Optical Frequency Domain Reflectometer using Various Types of Fiber Bragg Gratings NANI FADZLINA NAIM, AHMAD FARIS AIMAN ASHA’ARI, SUZI SEROJA SARNIN, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8668065/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract This paper presents a centralized, simple, and cost-effective monitoring system for Point-to-Multipoint (P2MP) Passive Optical Networks (PON) based on the Optical Frequency Domain Reflectometry (OFDR) technique. A 1530 nm Distributed Feedback Laser (DFB) and a Light-Emitting Diode (LED) are evaluated as monitoring sources to assess performance and feasibility for low-cost deployment. Fiber Bragg Gratings (FBGs) with selected Bragg wavelengths and bandwidths are utilized as drop-fiber identifiers to enable customer-level localization and monitoring within the distribution network. The proposed FBG placement follows an OFDR-based configuration, where one FBG is positioned after the monitoring source, while additional FBGs are inserted along the distribution fibers. By leveraging the OFDR concept, the system operates with reduced monitoring source bandwidth requirements and enables the use of a low-cost receiver, implemented using a Radio Frequency (RF) spectrum analyzer. Experimental results demonstrate that the proposed centralized monitoring approach is capable of monitoring up to 32 customers, achieving a minimum downstream received power of − 25 dBm. Overall, the proposed system offers a practical and scalable monitoring solution for PON infrastructure with reduced hardware complexity and lower operational cost. Passive Optical Network Optical Frequency Domain Reflectometer Monitoring Fiber Bragg Grating Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. INTRODUCTION The Passive Optical Network (PON) has emerged as a key architecture for realizing Fiber-to-the-Home (FTTH) connectivity [ 1 ]. It is referred to as “passive” because only non-electronic optical components are placed between the Optical Line Terminal (OLT) situated at the Central Office (CO) and the Optical Network Units (ONUs) located at customer premises. In a conventional point-to-multipoint (P2MP) configuration, a single OLT at the provider’s central node serves multiple ONUs installed at user sites. Data transmitted downstream from the OLT travels through a feeder fiber and is then divided by an optical splitter, which distributes the optical signal power across several distribution fibers before reaching each ONU. In June 2014, the Institute of Electrical and Electronics Engineers (IEEE) ratified the Ethernet Passive Optical Network (EPON) under the IEEE 802.3ah standard. EPON, operating in a P2MP topology, has become one of the most widely implemented FTTH solutions worldwide [ 2 ], particularly in regions such as Japan, Korea, China, and Taiwan [ 3 ]. As network capacity continues to expand and infrastructure grows more sophisticated, maintaining a high level of quality of service (QoS) has become increasingly critical. Optical network monitoring has gained much importance in recent years. There were many researches on fiber fault monitoring system to ensure quality and reliability of fiber communication system [ 4 ]. Commercial monitoring technique employs an Optical Time Domain Reflectometer (OTDR) which is located at the central office for monitoring optical fibers. OTDR is a method that has been given various platform of development. However, this method is only suitable for monitoring feeder fiber as OTDR is only suitable for point-to-point (P2P) fault locating due to the single wavelength of short pulse OTDR signal [ 5 ]. Generally, optical network monitoring approaches are classified into two major categories: Optical Time-Domain Reflectometry (OTDR)–based and non-OTDR–based methods. The OTDR category includes techniques such as single-wavelength OTDR, tunable OTDR, and Brillouin OTDR, whereas non-OTDR methods comprise Optical Frequency-Domain Reflectometry (OFDR), optical coding, and reflective signal analysis [ 6 ]. Single wavelength OTDR is the commercial OTDR which requires the OTDR to be injected in upstream direction. However, this technique is only suitable for P2P monitoring and it also has the drawback of not being centralized [ 7 ]. In [ 8 ], tunable OTDR is deployed for network monitoring. However, this method is less favored due to high cost wavelength router and tunable laser source. Brillouin OTDR has been demonstrated by [ 9 ] whereas the material of the distribution fiber core is changed to a frequency shift fiber. The tremendous change of distribution fibers is less preferred due to high cost. In [ 10 ], embedded OTDR is also an improvement from conventional OTDR. This system uses optical transceiver modules for OTDR measurement. The demonstration discussed by the author from result generated by computer algorithm is for Point to Point network only. An optical coding–based PON monitoring system was proposed in [ 11 ]. In this approach, distinct encoders composed of Fiber Bragg Gratings (FBGs) were employed at each branch to serve as unique identifiers, which were subsequently decoded by a network recognition algorithm at the receiver. This method represented an enhancement over earlier optical decoding techniques and was reported to minimize power loss. The authors presented a spectral diagram illustrating the overall received signals; however, the spectral features corresponding to individual branches were not clearly distinguished. In addition, overlapping signals produced peaks of higher intensity, complicating interpretation. Consequently, this technique demands complex signal analysis. Another approach for PON monitoring employs a Self-Injection Reflective Semiconductor Optical Amplifier (SL-RSOA). In [ 12 ], the authors demonstrated a method that utilizes the existing upstream data signals for fault identification, thereby eliminating the need for a separate monitoring source. The results successfully distinguished between normal and faulty fiber conditions. Although the study reported only a minor impact on upstream transmission, this approach remains suboptimal for fiber fault detection, as it still introduces degradation to certain system performance parameters. OFDR technique which is based on coherent detection has been presented by [ 13 ]. An interferometer (IF) unit is inserted at each drop fiber. The IF unit will create a distinct beat frequency that can be observed on the OFDR trace. An optical coding approach has been established by [ 14 ]. For this method, each branch is assigned a pseudo orthogonal code which is produced by an encoder. Any missing code indicates that there is fiber failure at the specific branch in the network. In the reflective-based monitoring technique described in [ 15 ], a micro-electromechanical system (MEMS) optical switch and a mirror are positioned before the Optical Network Unit (ONU). The mirror reflects the monitoring signal, while the MEMS optical switch modulates it to generate time-shifted pulses, producing a unique signal pattern for each branch. However, the implementation of a MEMS optical switch necessitates an electrical control signal, which contradicts the fundamental passive nature of a PON architecture. In this paper, a simulation of PON monitoring system employing OFDR concept has been conducted. Higher spatial resolution and sensitivity are the main advantages of OFDR [ 16 ]. Two monitoring sources have been simulated to test for suitability, a 1530 nm DFB and LED. FBGx is placed after the monitoring source. An FBG with specific Bragg wavelength is inserted before ONU for each drop fiber. This FBGs will act as an interferometer. The interferometer concept is by interfering two signals with distinct frequencies to create a beat signal [ 17 ]. The back reflection optical signals from the FBGs and FBGx will produce beat frequencies which appear as peaks using the RF Spectrum Analyzer. By employing OFDR concept, narrower bandwidth of monitoring source is required, and a lower cost receiver is used which is the Radio Frequency (RF) spectrum analyzer. Optical Frequency Domain Reflectometry (OFDR) serves as an effective approach for measuring back-reflection spectra in optical fiber systems. A standard OFDR setup comprises an optical source, a device under test, and a spectrum analyzer. In this monitoring configuration, Fiber Bragg Gratings (FBGs) are integrated as reflective sensing components, and the reflected optical signals are examined in the frequency domain using an RF spectrum analyzer. 2. DESIGN PRINCIPLES In this design, an optical network monitoring system is employed into Ethernet Passive Optical Network (EPON) as shown in Fig. 1 . A 1530 nm Distributed Feedback Laser (DFB) laser or Light Emitting Diode (LED) is used as the monitoring source. The monitoring signal will pass FBGx with Bragg wavelength of 1530nm, bandwidth of 0.02 nm and reflectivity of 10%. Monitoring signal will co-propagate with traffic signals at 1490 and 1550 nm. All the signals will pass through the feeder fiber of 10 km before reach the Fiber Distribution Cabinet (FDC) which is a 1x4 optical splitter. FDC is connected to Fiber Distribution Panel (FDP) via a distribution fiber. FDP is usually a 1X8 or 1X16 optical splitter. After FDP, there is drop fiber with length less than 250 m. Another FBGn is inserted before the Optical Network Unit (ONU) which is located at customer’s premise. There are two types of FBGn used in this design. If n is odd number, the FBG has bandwidth of 0.1 nm and reflectivity of 50%. If n is even number, bandwidth of the FBG is 0.015 nm and reflectivity of 50%. Two types of FBGs are used in order to optimize the limited bandwidth of the monitoring source. The back reflection optical signals from the FBGs and FBGx will produce beat frequencies which appear as peaks. The back reflection optical signals will also be amplified using an Erbium Doped Fiber Amplifier (EDFA) and can be observed as peaks using Radio Frequency (RF) Spectrum Analyzer. Beat frequency is calculated using formula (1) whereas \(\:\varDelta\:f\) is the beat frequencies between all branches in the RF spectrum analyzer. Centre wavelength of the FBGx, 1530nm is Lambda, \(\:\lambda\:\) . Delta lambda, \(\:\varDelta\:\lambda\:\) is the difference between FBGn and FBGx. C is the speed of light which is 299792458 m/s. $$\:\varDelta\:f=\:\frac{c(\varDelta\:\lambda\:)}{{\lambda\:}^{2}}$$ 1 3. RESULT AND DISCUSSION The simulation setup of this monitoring technique has been established. The simulation has been done using OptiSystem simulation software. In this monitoring technique, two monitoring sources are employed and tested, 1530 nm of DFB laser and LED. Each monitoring source will produce different FBGs spectra as shown in Fig. 2. As explained earlier, each drop fiber is represented by an FBG reflection spectrum that can be observed using an RF spectrum analyzer. Basically, one Bragg wavelength is represented by two FBGs reflection spectra with different bandwidth to optimize the optical bandwidth. Fig. 2 a) to e) demonstrate the FBGs reflection spectra for 4, 8, 16, 24 and 32, respectively using two types of monitoring sources. As can be seen in Fig. 2 a), there are two peaks which represent four drop fibers. The green line represents the spectrum when the monitoring source is DFB laser while blue line represents the spectrum when the monitoring source is DFB laser. From Fig. 2, it can be perceived that DFB laser as monitoring source produces higher Optical Signal to Noise Ratio (OSNR) rather than spectrum produced by LED. Thus, DFB laser has been chosen as the monitoring source as it will produce higher OSNR spectrum. Fig. 2 f) displays the FBGs reflection spectra during normal and faulty conditions. The dotted line denotes normal condition while the straight line represents faulty condition. From the figure, it can be realized that there are 8 peaks that denote 16 drop fibers or branches. By observing the faulty condition, it can clearly be seen that there are missing spectrum or faults at branch #3,4,5,8,11,12,13 and 16. For instance, the missing second peak denotes that there are fault for branch #3 and 4. On the other hand, there is only one spectrum which is FBG4 with bandwidth of 0.015 nm for the third peak. Thus, it means that there is missing FBG5 spectrum with bandwidth of 0.1nm which indicates a a fiber failure. Fig. 3 shows optical power received that is measured using an optical power meter before ONU versus number of customers. It is found that the power received at the ONU decrease as the number of customers growth. Assuming all drop fibers are occupied with ONUs, the number of customers is the same as the number of splitting ratios of the optical splitter. This power decrement is due to higher insertion loss of the optical splitter as the splitting ratio increase. The lowest power received is when the splitting ratio is 32 which is -25 dBm. The receiver sensitivity for ONU in EPON used in this simulation is -27 dBm [18]. Hence, this monitoring system is suitable to be used for up to 32 customers. The power budget between the OLT and ONU has also been calculated. The transmitted power from the OLT is 4 dBm [19]. As mentioned previously, the losses in the optical network is mainly due to the optical splitter. The insertion loss of the 1x4, 1x8, 1x12, 1x16, 1x24 and 1x32 optical splitters are 7, 10.3, 12.2, 13.6, 15.8 and 16.6 dB, respectively [20]. The receiver sensitivity used in this setup is -27 dBm. Fig. 4 shows the excess power margin versus number of customers. The excess power margin is getting lower as the number of customers increase as the losses incline as the number of splitting ratios growth. The excess power must be greater than zero for the network to be viable. It can be perceived that this system is capable to be deployed by roughly 50 customers. However, the system is only suitable to be deployed by 32 customers due to the available commercial optical splitter. Fig. 5 displays the power received of the first ONU versus Bit Error Rate (BER) performance of the network with the monitoring system (blue line) and without it (red line). It can be observed that both networks show that the BER is getting higher as the power received decrease. At lower power received, the network without the monitoring system has lower BER performance. It can also be perceived that there is a very slight difference of BER performance between both networks which is around 0.5 dB. Thus, it can be concluded that the monitoring system has a very minimal effect on the network performance which is negligible. CONCLUSION This paper presents the design of a monitoring framework for point-to-multipoint (P2MP) Passive Optical Networks (PONs). A Distributed Feedback Laser (DFB) operating at 1530 nm is selected as the monitoring light source due to its superior Optical Signal-to-Noise Ratio (OSNR) compared with a Light Emitting Diode (LED). Fiber Bragg Gratings (FBGs) with distinct Bragg wavelengths and bandwidths are employed to act as identifiers for each drop fiber. The configuration of these FBGs follows the principle of an Optical Frequency Domain Reflectometer (OFDR), in which one reference grating (FBGx) is positioned immediately after the monitoring source, while the remaining gratings are distributed along the network’s branches. By adopting the OFDR-based approach, a monitoring source with a narrower spectral width is sufficient, enabling the use of a cost-effective Radio Frequency (RF) spectrum analyzer as the receiver. The proposed system can effectively supervise up to 32 subscriber connections, maintaining a minimum received power of –25 dBm before the Optical Network Unit (ONU) and exhibiting negligible Bit Error Rate (BER) degradation when compared with a conventional PON without monitoring. Overall, this architecture provides a simple yet economical monitoring solution that requires only a low-bandwidth optical source. Declarations Author Contribution N.F. N., A. F. A. A. and A. A. A. B. wrote the main manuscript text. All authors reviewed the manuscript. Acknowledgement The authors would like to express their sincere appreciation to Universiti Teknologi MARA (UiTM), Malaysia, for the institutional support and research facilities that enabled this work. References H. S. Abbas and M. A. Gregory, “The next generation of passive optical networks: A review,” J. Netw. Comput. Appl., vol. 67, pp. 53–74, 2016. Paola Garfias, Lluís Gutiérrez, and Sebastià Sallent, "Enhanced DBA to Provide QoS to Coexistent EPON and 10G-EPON Networks," J. Opt. Commun. Netw. 4, 978-988 (2012) https://www.eetimes.com/document.asp?doc_id=1272066 M. M. Rad, K. Fouli, H. A. Fathallah, L. A. Rusch, and M. Maier, “Passive optical network monitoring: Challenges and requirements,” IEEE Commun. Mag., vol. 49, no. 2, pp. S45–S52, 2011. F. Caviglia and V. C. Di Biase, “Optical maintenance in PONs,” in 24th European Conf. on Optical Communication, 1998, vol. 1, pp. 621–625. Esmail, M. & H. Fathallah 2012. Physical Layer Monitoring Techniques for TDM-Passive Optical Networks: A Survey. Communications Surveys & Tutorials, IEEE PP(99): 1-16. “Maintenance & Troubleshooting of a PON Network with an OTDR,” JDS Uniphase Corporation, Application note January 2010. Kazumasa, O., S. Masakazu, H. Jun-Ichiro, B. Atsuhito, N. Takao & S. Kazuhiro 2000. Field trial of in-service individual line monitoring of PONs using a tunable OTDR Honda, N., D. Iida, H. Izumita & Y. Azuma 2009. In-Service Line Monitoring System in PONs Using 1650-nm Brillouin OTDR and Fibers With Individually Assigned BFSs. Lightwave Technology, Journal of 27(20): 4575-4582. H. Schmuck, J. Hehmann, M. Straub, and T. Pfeiffer, “Embedded OTDR techniques for cost-efficient fibre monitoring in optical access networks,” 2006 Eur. Conf. Opt. Commun. Proceedings, ECOC 2006, pp. 10–11, 2006. X. Zhou, F. Zhang, and X. Sun, “Centralized PON monitoring scheme based on optical coding,” IEEE Photonics Technol. Lett., vol. 25, no. 9, pp. 795–797, 2013. M. Thollabandi, K. W. Shim, S. Hann, and C. S. Park, “A surveillance technique based on spectral analysis of SL-RSOA for PS-PON,” 2008 IEEE PhotonicsGlobal Singapore, IPGC 2008, no. 1, pp. 2–4, 2008. Yuksel, K., M. Wuilpart, V. Moeyaert & P. Megret 2010. Novel Monitoring Technique for Passive Optical Networks Based on Optical Frequency Domain Reflectometry and Fiber Bragg Gratings. Optical Communications and Networking, IEEE/OSA Journal of 2(7): 463-468. Fathallah, H. & L. A. Rusch July 2007. Code-division multiplexing for in-service out-of- band monitoring of live FTTH-PONs. JOURNAL OF OPTICAL NETWORKING 6(7): 819- 829. Sun-Chien, K., L. Shu-Chuan & H. Yin-Hsun 2011. A fiber fault monitoring design for PON system using reflective signal. OptoeElectronics and Communications Conference (OECC), 2011 16th, hlm. 555-556. B. Huttner, B. Gisin, O. Guinnard, N. Gisin, R. Passy, and J. P. Von der Weid, “Optical frequency domain reflectometer for characterization of optical networks and devices,” ComTec, vol. 77, no. 1, pp. 20–23, 1999. A. Reza, S. Tofighi, M. Bathaee, and F. Farm, “Optical Fiber Interferometers and Their Applications,” Interferom. - Res. Appl. Sci. Technol., 2012. http://cdatatec.com/product-item/fd600-104-series-epon-onu-includes-wi-fi/#tab-id-2 http://cdatatec.com/product-item/4pon-gepon-olt-fd1204s/ http://quoau.com/fiber-optic-splitter-types-1u-19-rack-mount-plc-fiber-splitter/ Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 12 May, 2026 Reviewers agreed at journal 22 Apr, 2026 Reviewers agreed at journal 23 Mar, 2026 Reviewers invited by journal 09 Mar, 2026 Editor assigned by journal 22 Feb, 2026 Submission checks completed at journal 26 Jan, 2026 First submitted to journal 22 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8668065","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":603900028,"identity":"775c206c-5475-495d-889e-b1f15fd20399","order_by":0,"name":"NANI FADZLINA NAIM","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/klEQVRIiWNgGAWjYJCCAxUMzAx8zEDWBwYJsIgEQS1ngFrYgFoYZzBISBClhQGsBUgz80BV49Vizn724IEDNdb2bOy8Bz/btlnU6TYwH7zNw7AtsQGHFsuevIQDB46lM7Mx8yVL57ZJSJgdYEu25mG4jVOLwYEcg8Mf2A6zsTHzGEC18JhJ49Vy/o3BgQP/DvMAtRj/tgRr4f+GX8uNHIMDB9sOSwC1mEkzQmxhI6AFaMvBvnQDkBbLnnMSktsOsxlbzjG4bYzbYTnGHw58s7bn5z9jfONHWR2/2fHmhzfeVNyWxaUFC2AGG8XgSIIWKLAnWccoGAWjYBQMVwAA8rBSlXjL/8sAAAAASUVORK5CYII=","orcid":"","institution":"FAKULTI KEJURUTERAAN ELEKTRIK(FKE)","correspondingAuthor":true,"prefix":"","firstName":"NANI","middleName":"FADZLINA","lastName":"NAIM","suffix":""},{"id":603900029,"identity":"e78fd3c1-e936-4a07-91f5-a43aa3eb8b54","order_by":1,"name":"AHMAD FARIS AIMAN ASHA’ARI","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN ELEKTRIK(FKE)","correspondingAuthor":false,"prefix":"","firstName":"AHMAD","middleName":"FARIS AIMAN","lastName":"ASHA’ARI","suffix":""},{"id":603900030,"identity":"1d517b46-3ca2-4a31-b074-7b58ee4e63d8","order_by":2,"name":"SUZI SEROJA SARNIN","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN ELEKTRIK(FKE)","correspondingAuthor":false,"prefix":"","firstName":"SUZI","middleName":"SEROJA","lastName":"SARNIN","suffix":""},{"id":603900031,"identity":"89dbb4dc-ea72-4a7c-beb4-1757f38d9be3","order_by":3,"name":"AZITA LAILY YUSOF","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN ELEKTRIK(FKE)","correspondingAuthor":false,"prefix":"","firstName":"AZITA","middleName":"LAILY","lastName":"YUSOF","suffix":""},{"id":603900032,"identity":"2dfe2920-0ed5-44fe-8eb6-e43bf7ac6d3a","order_by":4,"name":"NORSUZILA YA’ACOB","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN ELEKTRIK(FKE)","correspondingAuthor":false,"prefix":"","firstName":"NORSUZILA","middleName":"","lastName":"YA’ACOB","suffix":""},{"id":603900033,"identity":"e05eedec-a76a-46aa-8cd8-52d5d5a37e56","order_by":5,"name":"WAN NORSYAFIZAN WAN MUHAMAD","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN ELEKTRIK(FKE)","correspondingAuthor":false,"prefix":"","firstName":"WAN","middleName":"NORSYAFIZAN WAN","lastName":"MUHAMAD","suffix":""},{"id":603900034,"identity":"d848bbed-5f41-4198-874b-e36a7faf1b63","order_by":6,"name":"AHMAD ASHRIF A. BAKAR","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN DAN ALAM BINA","correspondingAuthor":false,"prefix":"","firstName":"AHMAD","middleName":"ASHRIF A.","lastName":"BAKAR","suffix":""},{"id":603900035,"identity":"3eabb367-dbfa-4a9e-8f83-94a72db5387c","order_by":7,"name":"MOHD SAIFUL DZULKEFLY ZAN","email":"","orcid":"","institution":"FAKULTI KEJURUTERAAN DAN ALAM BINA","correspondingAuthor":false,"prefix":"","firstName":"MOHD","middleName":"SAIFUL DZULKEFLY","lastName":"ZAN","suffix":""}],"badges":[],"createdAt":"2026-01-22 09:53:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8668065/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8668065/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104505200,"identity":"34524ae5-ed29-47fc-bab3-a400130c8f48","added_by":"auto","created_at":"2026-03-12 14:41:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":52990,"visible":true,"origin":"","legend":"\u003cp\u003ePassive Optical Network (PON) architecture with monitoring technique based on Optical Frequency Domain Reflectometer (OFDR). OLT is Optical Line Terminal, SMF is single mode fiber, ONU is Optical Network Unit, C is coupler, OC is Optical Circulator and EDFA is Erbium Doped Fiber Amplifier.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8668065/v1/06686992705680aa25e2c537.png"},{"id":104505177,"identity":"0e5f4132-0e96-4fc5-8b38-95cdeda1b479","added_by":"auto","created_at":"2026-03-12 14:41:36","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":565296,"visible":true,"origin":"","legend":"\u003cp\u003eThe FBGs reflection spectra which represent a) 4 ONUs b) 8 ONUs c) 16 ONUs d) 24 ONUs e) 32 ONUs and f) 16 ONUs with drop fibers failure at branch #3,4,5,8,11,12,13,16\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8668065/v1/4a592b7d0716ec54d7cb7a92.jpeg"},{"id":104505195,"identity":"f500ed31-def3-4855-aa9d-fb604273b270","added_by":"auto","created_at":"2026-03-12 14:41:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":21540,"visible":true,"origin":"","legend":"\u003cp\u003eDownstream signal at 1490 nm power received at ONU versus number of users\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8668065/v1/0b5206d5e5621c0b8f9d1578.png"},{"id":104505234,"identity":"a043f0a0-ecb3-44bc-8b08-0eb7630e9731","added_by":"auto","created_at":"2026-03-12 14:41:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":16222,"visible":true,"origin":"","legend":"\u003cp\u003eExcess power margin of traffic signal versus number of users\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8668065/v1/b00974a844e391bd4f98fb25.png"},{"id":104505216,"identity":"cc6b14ea-c52b-407a-87d0-aa649efc3505","added_by":"auto","created_at":"2026-03-12 14:41:47","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":29712,"visible":true,"origin":"","legend":"\u003cp\u003eThe comparison of Bit Error Rate (BER) between the networks with and without monitoring system\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8668065/v1/3fff65d323ce0ed388c83074.png"},{"id":104505242,"identity":"4e1c23f6-aa53-4c3a-8a00-fc9b9e9a97ec","added_by":"auto","created_at":"2026-03-12 14:41:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":970689,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8668065/v1/c103e347-eb4f-4460-a6c4-0dbb300a5bb6.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Design of Passive Optical Network Monitoring System Based on Optical Frequency Domain Reflectometer using Various Types of Fiber Bragg Gratings","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eThe Passive Optical Network (PON) has emerged as a key architecture for realizing Fiber-to-the-Home (FTTH) connectivity [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. It is referred to as \u0026ldquo;passive\u0026rdquo; because only non-electronic optical components are placed between the Optical Line Terminal (OLT) situated at the Central Office (CO) and the Optical Network Units (ONUs) located at customer premises. In a conventional point-to-multipoint (P2MP) configuration, a single OLT at the provider\u0026rsquo;s central node serves multiple ONUs installed at user sites. Data transmitted downstream from the OLT travels through a feeder fiber and is then divided by an optical splitter, which distributes the optical signal power across several distribution fibers before reaching each ONU. In June 2014, the Institute of Electrical and Electronics Engineers (IEEE) ratified the Ethernet Passive Optical Network (EPON) under the IEEE 802.3ah standard. EPON, operating in a P2MP topology, has become one of the most widely implemented FTTH solutions worldwide [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], particularly in regions such as Japan, Korea, China, and Taiwan [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. As network capacity continues to expand and infrastructure grows more sophisticated, maintaining a high level of quality of service (QoS) has become increasingly critical.\u003c/p\u003e \u003cp\u003eOptical network monitoring has gained much importance in recent years. There were many researches on fiber fault monitoring system to ensure quality and reliability of fiber communication system [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Commercial monitoring technique employs an Optical Time Domain Reflectometer (OTDR) which is located at the central office for monitoring optical fibers. OTDR is a method that has been given various platform of development. However, this method is only suitable for monitoring feeder fiber as OTDR is only suitable for point-to-point (P2P) fault locating due to the single wavelength of short pulse OTDR signal [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Generally, optical network monitoring approaches are classified into two major categories: Optical Time-Domain Reflectometry (OTDR)\u0026ndash;based and non-OTDR\u0026ndash;based methods. The OTDR category includes techniques such as single-wavelength OTDR, tunable OTDR, and Brillouin OTDR, whereas non-OTDR methods comprise Optical Frequency-Domain Reflectometry (OFDR), optical coding, and reflective signal analysis [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSingle wavelength OTDR is the commercial OTDR which requires the OTDR to be injected in upstream direction. However, this technique is only suitable for P2P monitoring and it also has the drawback of not being centralized [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], tunable OTDR is deployed for network monitoring. However, this method is less favored due to high cost wavelength router and tunable laser source. Brillouin OTDR has been demonstrated by [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] whereas the material of the distribution fiber core is changed to a frequency shift fiber. The tremendous change of distribution fibers is less preferred due to high cost.\u003c/p\u003e \u003cp\u003eIn [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], embedded OTDR is also an improvement from conventional OTDR. This system uses optical transceiver modules for OTDR measurement. The demonstration discussed by the author from result generated by computer algorithm is for Point to Point network only.\u003c/p\u003e \u003cp\u003eAn optical coding\u0026ndash;based PON monitoring system was proposed in [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In this approach, distinct encoders composed of Fiber Bragg Gratings (FBGs) were employed at each branch to serve as unique identifiers, which were subsequently decoded by a network recognition algorithm at the receiver. This method represented an enhancement over earlier optical decoding techniques and was reported to minimize power loss. The authors presented a spectral diagram illustrating the overall received signals; however, the spectral features corresponding to individual branches were not clearly distinguished. In addition, overlapping signals produced peaks of higher intensity, complicating interpretation. Consequently, this technique demands complex signal analysis.\u003c/p\u003e \u003cp\u003eAnother approach for PON monitoring employs a Self-Injection Reflective Semiconductor Optical Amplifier (SL-RSOA). In [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], the authors demonstrated a method that utilizes the existing upstream data signals for fault identification, thereby eliminating the need for a separate monitoring source. The results successfully distinguished between normal and faulty fiber conditions. Although the study reported only a minor impact on upstream transmission, this approach remains suboptimal for fiber fault detection, as it still introduces degradation to certain system performance parameters.\u003c/p\u003e \u003cp\u003eOFDR technique which is based on coherent detection has been presented by [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. An interferometer (IF) unit is inserted at each drop fiber. The IF unit will create a distinct beat frequency that can be observed on the OFDR trace. An optical coding approach has been established by [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. For this method, each branch is assigned a pseudo orthogonal code which is produced by an encoder. Any missing code indicates that there is fiber failure at the specific branch in the network. In the reflective-based monitoring technique described in [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], a micro-electromechanical system (MEMS) optical switch and a mirror are positioned before the Optical Network Unit (ONU). The mirror reflects the monitoring signal, while the MEMS optical switch modulates it to generate time-shifted pulses, producing a unique signal pattern for each branch. However, the implementation of a MEMS optical switch necessitates an electrical control signal, which contradicts the fundamental passive nature of a PON architecture.\u003c/p\u003e \u003cp\u003eIn this paper, a simulation of PON monitoring system employing OFDR concept has been conducted. Higher spatial resolution and sensitivity are the main advantages of OFDR [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Two monitoring sources have been simulated to test for suitability, a 1530 nm DFB and LED. FBGx is placed after the monitoring source. An FBG with specific Bragg wavelength is inserted before ONU for each drop fiber. This FBGs will act as an interferometer. The interferometer concept is by interfering two signals with distinct frequencies to create a beat signal [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The back reflection optical signals from the FBGs and FBGx will produce beat frequencies which appear as peaks using the RF Spectrum Analyzer. By employing OFDR concept, narrower bandwidth of monitoring source is required, and a lower cost receiver is used which is the Radio Frequency (RF) spectrum analyzer.\u003c/p\u003e \u003cp\u003eOptical Frequency Domain Reflectometry (OFDR) serves as an effective approach for measuring back-reflection spectra in optical fiber systems. A standard OFDR setup comprises an optical source, a device under test, and a spectrum analyzer. In this monitoring configuration, Fiber Bragg Gratings (FBGs) are integrated as reflective sensing components, and the reflected optical signals are examined in the frequency domain using an RF spectrum analyzer.\u003c/p\u003e"},{"header":"2. DESIGN PRINCIPLES","content":"\u003cp\u003eIn this design, an optical network monitoring system is employed into Ethernet Passive Optical Network (EPON) as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. A 1530 nm Distributed Feedback Laser (DFB) laser or Light Emitting Diode (LED) is used as the monitoring source. The monitoring signal will pass FBGx with Bragg wavelength of 1530nm, bandwidth of 0.02 nm and reflectivity of 10%. Monitoring signal will co-propagate with traffic signals at 1490 and 1550 nm. All the signals will pass through the feeder fiber of 10 km before reach the Fiber Distribution Cabinet (FDC) which is a 1x4 optical splitter. FDC is connected to Fiber Distribution Panel (FDP) via a distribution fiber. FDP is usually a 1X8 or 1X16 optical splitter. After FDP, there is drop fiber with length less than 250 m. Another FBGn is inserted before the Optical Network Unit (ONU) which is located at customer\u0026rsquo;s premise. There are two types of FBGn used in this design. If n is odd number, the FBG has bandwidth of 0.1 nm and reflectivity of 50%. If n is even number, bandwidth of the FBG is 0.015 nm and reflectivity of 50%. Two types of FBGs are used in order to optimize the limited bandwidth of the monitoring source. The back reflection optical signals from the FBGs and FBGx will produce beat frequencies which appear as peaks. The back reflection optical signals will also be amplified using an Erbium Doped Fiber Amplifier (EDFA) and can be observed as peaks using Radio Frequency (RF) Spectrum Analyzer.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBeat frequency is calculated using formula (1) whereas \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:f\\)\u003c/span\u003e\u003c/span\u003e is the beat frequencies between all branches in the RF spectrum analyzer. Centre wavelength of the FBGx, 1530nm is Lambda, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\lambda\\:\\)\u003c/span\u003e\u003c/span\u003e. Delta lambda, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:\\lambda\\:\\)\u003c/span\u003e\u003c/span\u003e is the difference between FBGn and FBGx. C is the speed of light which is 299792458 m/s.\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\varDelta\\:f=\\:\\frac{c(\\varDelta\\:\\lambda\\:)}{{\\lambda\\:}^{2}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"3. RESULT AND DISCUSSION","content":"\u003cp\u003eThe simulation setup of this monitoring technique has been established. The simulation has been done using OptiSystem simulation software. In this monitoring technique, two monitoring sources are employed and tested, 1530 nm of DFB laser and LED. Each monitoring source will produce different FBGs spectra as shown in Fig. 2.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs explained earlier, each drop fiber is represented by an FBG reflection spectrum that can be observed using an RF spectrum analyzer. Basically, one Bragg wavelength is represented by two FBGs reflection spectra with different bandwidth to optimize the optical bandwidth. Fig. 2 a) to e) demonstrate the FBGs reflection spectra for 4, 8, 16, 24 and 32, respectively using two types of monitoring sources. As can be seen in Fig. 2 a), there are two peaks which represent four drop fibers. The green line represents the spectrum when the monitoring source is DFB laser while blue line represents the spectrum when the monitoring source is DFB laser. From Fig. 2, it can be perceived that DFB laser as monitoring source produces higher Optical Signal to Noise Ratio (OSNR) rather than spectrum produced by LED. Thus, DFB laser has been chosen as the monitoring source as it will produce higher OSNR spectrum. Fig. 2 f) displays the FBGs reflection spectra during normal and faulty conditions. The dotted line denotes normal condition while the straight line represents faulty condition. From the figure, it can be realized that there are 8 peaks that denote 16 drop fibers or branches. By observing the faulty condition, it can clearly be seen that there are missing spectrum or faults at branch #3,4,5,8,11,12,13 and 16. For instance, the missing second peak denotes that there are fault for branch #3 and 4. On the other hand, there is only one spectrum which is FBG4 with bandwidth of 0.015 nm for the third peak. Thus, it means that there is missing FBG5 spectrum with bandwidth of 0.1nm which indicates a a fiber failure. \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFig. 3 shows optical power received that is measured using an optical power meter before ONU versus number of customers. It is found that the power received at the ONU decrease as the number of customers growth. Assuming all drop fibers are occupied with ONUs, the number of customers is the same as the number of splitting ratios of the optical splitter. This power decrement is due to higher insertion loss of the optical splitter as the splitting ratio increase. The lowest power received is when the splitting ratio is 32 which is -25 dBm. The receiver sensitivity for ONU in EPON used in this simulation is -27 dBm [18]. Hence, this monitoring system is suitable to be used for up to 32 customers. \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe power budget between the OLT and ONU has also been calculated. The transmitted power from the OLT is 4 dBm [19]. As mentioned previously, the losses in the optical network is mainly due to the optical splitter. The insertion loss of the 1x4, 1x8, 1x12, 1x16, 1x24 and 1x32 optical splitters are 7, 10.3, 12.2, 13.6, 15.8 and 16.6 dB, respectively [20]. The receiver sensitivity used in this setup is -27 dBm. Fig. 4 shows the excess power margin versus number of customers. The excess power margin is getting lower as the number of customers increase as the losses incline as the number of splitting ratios growth. The excess power must be greater than zero for the network to be viable. It can be perceived that this system is capable to be deployed by roughly 50 customers. However, the system is only suitable to be deployed by 32 customers due to the available commercial optical splitter. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFig. 5 displays the power received of the first ONU versus Bit Error Rate (BER) performance of the network with the monitoring system (blue line) and without it (red line). It can be observed that both networks show that the BER is getting higher as the power received decrease. At lower power received, the network without the monitoring system has lower BER performance. It can also be perceived that there is a very slight difference of BER performance between both networks which is around 0.5 dB. Thus, it can be concluded that the monitoring system has a very minimal effect on the network performance which is negligible.\u0026nbsp;\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThis paper presents the design of a monitoring framework for point-to-multipoint (P2MP) Passive Optical Networks (PONs). A Distributed Feedback Laser (DFB) operating at 1530 nm is selected as the monitoring light source due to its superior Optical Signal-to-Noise Ratio (OSNR) compared with a Light Emitting Diode (LED). Fiber Bragg Gratings (FBGs) with distinct Bragg wavelengths and bandwidths are employed to act as identifiers for each drop fiber. The configuration of these FBGs follows the principle of an Optical Frequency Domain Reflectometer (OFDR), in which one reference grating (FBGx) is positioned immediately after the monitoring source, while the remaining gratings are distributed along the network\u0026rsquo;s branches. By adopting the OFDR-based approach, a monitoring source with a narrower spectral width is sufficient, enabling the use of a cost-effective Radio Frequency (RF) spectrum analyzer as the receiver. The proposed system can effectively supervise up to 32 subscriber connections, maintaining a minimum received power of \u0026ndash;25 dBm before the Optical Network Unit (ONU) and exhibiting negligible Bit Error Rate (BER) degradation when compared with a conventional PON without monitoring. Overall, this architecture provides a simple yet economical monitoring solution that requires only a low-bandwidth optical source.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eN.F. N., A. F. A. A. and A. A. A. B. wrote the main manuscript text. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to express their sincere appreciation to Universiti Teknologi MARA (UiTM), Malaysia, for the institutional support and research facilities that enabled this work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eH. S. Abbas and M. A. Gregory, \u0026ldquo;The next generation of passive optical networks: A review,\u0026rdquo; J. Netw. Comput. Appl., vol. 67, pp. 53\u0026ndash;74, 2016.\u003c/li\u003e\n\u003cli\u003ePaola Garfias, Llu\u0026iacute;s Guti\u0026eacute;rrez, and Sebasti\u0026agrave; Sallent, \u0026quot;Enhanced DBA to Provide QoS to Coexistent EPON and 10G-EPON Networks,\u0026quot; J. Opt. Commun. Netw. 4, 978-988 (2012)\u003c/li\u003e\n\u003cli\u003ehttps://www.eetimes.com/document.asp?doc_id=1272066\u003c/li\u003e\n\u003cli\u003eM. M. Rad, K. Fouli, H. A. Fathallah, L. A. Rusch, and M. Maier, \u0026ldquo;Passive optical network monitoring: Challenges and requirements,\u0026rdquo; IEEE Commun. Mag., vol. 49, no. 2, pp. S45\u0026ndash;S52, 2011.\u003c/li\u003e\n\u003cli\u003eF. Caviglia and V. C. Di Biase, \u0026ldquo;Optical maintenance in PONs,\u0026rdquo; in 24th European Conf. on Optical Communication, 1998, vol. 1, pp. 621\u0026ndash;625.\u003c/li\u003e\n\u003cli\u003eEsmail, M. \u0026amp; H. Fathallah 2012. Physical Layer Monitoring Techniques for TDM-Passive Optical Networks: A Survey. Communications Surveys \u0026amp; Tutorials, IEEE PP(99): 1-16.\u003c/li\u003e\n\u003cli\u003e\u0026ldquo;Maintenance \u0026amp; Troubleshooting of a PON Network with an OTDR,\u0026rdquo; JDS Uniphase Corporation, Application note January 2010.\u003c/li\u003e\n\u003cli\u003eKazumasa, O., S. Masakazu, H. Jun-Ichiro, B. Atsuhito, N. Takao \u0026amp; S. Kazuhiro 2000. Field trial of in-service individual line monitoring of PONs using a tunable OTDR\u003c/li\u003e\n\u003cli\u003eHonda, N., D. Iida, H. Izumita \u0026amp; Y. Azuma 2009. In-Service Line Monitoring System in PONs Using 1650-nm Brillouin OTDR and Fibers With Individually Assigned BFSs. Lightwave Technology, Journal of 27(20): 4575-4582.\u003c/li\u003e\n\u003cli\u003eH. Schmuck, J. Hehmann, M. Straub, and T. Pfeiffer, \u0026ldquo;Embedded OTDR techniques for cost-efficient fibre monitoring in optical access networks,\u0026rdquo; 2006 Eur. Conf. Opt. Commun. Proceedings, ECOC 2006, pp. 10\u0026ndash;11, 2006.\u003c/li\u003e\n\u003cli\u003eX. Zhou, F. Zhang, and X. Sun, \u0026ldquo;Centralized PON monitoring scheme based on optical coding,\u0026rdquo; IEEE Photonics Technol. Lett., vol. 25, no. 9, pp. 795\u0026ndash;797, 2013.\u003c/li\u003e\n\u003cli\u003eM. Thollabandi, K. W. Shim, S. Hann, and C. S. Park, \u0026ldquo;A surveillance technique based on spectral analysis of SL-RSOA for PS-PON,\u0026rdquo; 2008 IEEE PhotonicsGlobal Singapore, IPGC 2008, no. 1, pp. 2\u0026ndash;4, 2008.\u003c/li\u003e\n\u003cli\u003eYuksel, K., M. Wuilpart, V. Moeyaert \u0026amp; P. Megret 2010. Novel Monitoring Technique for Passive Optical Networks Based on Optical Frequency Domain Reflectometry and Fiber Bragg Gratings. Optical Communications and Networking, IEEE/OSA Journal of 2(7): 463-468.\u003c/li\u003e\n\u003cli\u003eFathallah, H. \u0026amp; L. A. Rusch July 2007. Code-division multiplexing for in-service out-of- band monitoring of live FTTH-PONs. JOURNAL OF OPTICAL NETWORKING 6(7): 819- 829.\u003c/li\u003e\n\u003cli\u003eSun-Chien, K., L. Shu-Chuan \u0026amp; H. Yin-Hsun 2011. A fiber fault monitoring design for PON system using reflective signal. OptoeElectronics and Communications Conference (OECC), 2011 16th, hlm. 555-556.\u003c/li\u003e\n\u003cli\u003eB. Huttner, B. Gisin, O. Guinnard, N. Gisin, R. Passy, and J. P. Von der Weid, \u0026ldquo;Optical frequency domain reflectometer for characterization of optical networks and devices,\u0026rdquo; ComTec, vol. 77, no. 1, pp. 20\u0026ndash;23, 1999.\u003c/li\u003e\n\u003cli\u003eA. Reza, S. Tofighi, M. Bathaee, and F. Farm, \u0026ldquo;Optical Fiber Interferometers and Their Applications,\u0026rdquo; Interferom. - Res. Appl. Sci. Technol., 2012.\u003c/li\u003e\n\u003cli\u003ehttp://cdatatec.com/product-item/fd600-104-series-epon-onu-includes-wi-fi/#tab-id-2\u003c/li\u003e\n\u003cli\u003ehttp://cdatatec.com/product-item/4pon-gepon-olt-fd1204s/\u003c/li\u003e\n\u003cli\u003ehttp://quoau.com/fiber-optic-splitter-types-1u-19-rack-mount-plc-fiber-splitter/\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"photonic-network-communications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pnet","sideBox":"Learn more about [Photonic Network Communications](http://link.springer.com/journal/11107)","snPcode":"11107","submissionUrl":"https://submission.nature.com/new-submission/11107/3","title":"Photonic Network Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Passive Optical Network, Optical Frequency Domain Reflectometer, Monitoring, Fiber Bragg Grating","lastPublishedDoi":"10.21203/rs.3.rs-8668065/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8668065/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper presents a centralized, simple, and cost-effective monitoring system for Point-to-Multipoint (P2MP) Passive Optical Networks (PON) based on the Optical Frequency Domain Reflectometry (OFDR) technique. A 1530 nm Distributed Feedback Laser (DFB) and a Light-Emitting Diode (LED) are evaluated as monitoring sources to assess performance and feasibility for low-cost deployment. Fiber Bragg Gratings (FBGs) with selected Bragg wavelengths and bandwidths are utilized as drop-fiber identifiers to enable customer-level localization and monitoring within the distribution network. The proposed FBG placement follows an OFDR-based configuration, where one FBG is positioned after the monitoring source, while additional FBGs are inserted along the distribution fibers. By leveraging the OFDR concept, the system operates with reduced monitoring source bandwidth requirements and enables the use of a low-cost receiver, implemented using a Radio Frequency (RF) spectrum analyzer. Experimental results demonstrate that the proposed centralized monitoring approach is capable of monitoring up to 32 customers, achieving a minimum downstream received power of \u0026minus;\u0026thinsp;25 dBm. Overall, the proposed system offers a practical and scalable monitoring solution for PON infrastructure with reduced hardware complexity and lower operational cost.\u003c/p\u003e","manuscriptTitle":"Design of Passive Optical Network Monitoring System Based on Optical Frequency Domain Reflectometer using Various Types of Fiber Bragg Gratings","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-12 14:40:23","doi":"10.21203/rs.3.rs-8668065/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-12T18:52:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80503428259870817417043827871174449523","date":"2026-04-22T20:18:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"115283454278084973546790205913010430499","date":"2026-03-23T10:50:50+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-09T15:28:28+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-22T13:54:18+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-27T04:18:13+00:00","index":"","fulltext":""},{"type":"submitted","content":"Photonic Network Communications","date":"2026-01-22T09:23:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"photonic-network-communications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pnet","sideBox":"Learn more about [Photonic Network Communications](http://link.springer.com/journal/11107)","snPcode":"11107","submissionUrl":"https://submission.nature.com/new-submission/11107/3","title":"Photonic Network Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"86b75973-3287-4cd6-8d87-26560e0cdffd","owner":[],"postedDate":"March 12th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-12T18:52:20+00:00","index":22,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-12T14:40:23+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-12 14:40:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8668065","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8668065","identity":"rs-8668065","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}