{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,28]],"date-time":"2026-03-28T16:59:26Z","timestamp":1774717166651,"version":"3.50.1"},"reference-count":37,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2021,6,23]],"date-time":"2021-06-23T00:00:00Z","timestamp":1624406400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>For almost a half-decade, the unique autocorrelation properties of Golay complementary pairs (GCP) have added a significant value to the key performance of conventional time-domain multiplexed fiber Bragg grating sensors (TDM-FBGs). However, the employment of the unipolar form of Golay coded TDM-FBG has suffered from several performance flaws, such as limited improvement of the signal-to-noise ratio (SNIR), noisy backgrounds, and distorted signals. Therefore, we propose and experimentally implement several digital filtering techniques to mitigate such limitations. Moving averages (MA), Savitzky\u2013Golay (SG), and moving median (MM) filters were deployed to process the signals from two low reflectance FBG sensors located after around 16 km of fiber. The first part of the experiment discussed the sole deployment of Golay codes from 4 bits to 256 bits in the TDM-FBG sensor. As a result, the total SNIR of around 8.8 dB was experimentally confirmed for the longest 256-bit code. Furthermore, the individual deployment of MA, MM, and SG filters within the mentioned decoded sequences secured a further significant increase in SNIR of around 4, 3.5, and 3 dB, respectively. Thus, the deployment of the filtering technique alone resulted in at least four times faster measurement time (equivalent to 3 dB SNIR). Overall, the experimental analysis confirmed that MM outperformed the other two techniques in better signal shape, fastest signal transition time, comparable SNIR, and capability to maintain high spatial resolution.<\/jats:p>","DOI":"10.3390\/s21134299","type":"journal-article","created":{"date-parts":[[2021,6,23]],"date-time":"2021-06-23T11:28:41Z","timestamp":1624447721000},"page":"4299","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Digital Filtering Techniques for Performance Improvement of Golay Coded TDM-FBG Sensor"],"prefix":"10.3390","volume":"21","author":[{"given":"Mohamed M.","family":"Elgaud","sequence":"first","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"},{"name":"College of Electrical and Electronic Technology, Benghazi 0021861, Libya"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1440-5434","authenticated-orcid":false,"given":"Mohd Saiful Dzulkefly","family":"Zan","sequence":"additional","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1638-2678","authenticated-orcid":false,"given":"Abdulfatah A. G.","family":"Abushagur","sequence":"additional","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"},{"name":"Department of Electrical and Electronic Engineering, Faculty of Engineering, Gharyan University, Gharyan 0021841, Libya"}]},{"given":"Abdulwahhab E.","family":"Hamzah","sequence":"additional","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"}]},{"given":"Mohd Hadri Hafiz","family":"Mokhtar","sequence":"additional","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4543-8383","authenticated-orcid":false,"given":"Norhana","family":"Arsad","sequence":"additional","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9060-0346","authenticated-orcid":false,"given":"Ahmad Ashrif","family":"A. Bakar","sequence":"additional","affiliation":[{"name":"Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Selangor, Malaysia"}]}],"member":"1968","published-online":{"date-parts":[[2021,6,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Kashyap, R. (2010). Fiber Bragg Gratings, Academic Press.","DOI":"10.1016\/B978-0-12-372579-0.00007-7"},{"key":"ref_2","unstructured":"Rajan, G. (2015). Optical Fiber Sensors: Advanced Techniques and Applications; Devices, Circuits, and Systems, CRC Press."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2643","DOI":"10.1364\/AO.40.002643","article-title":"Time-division multiplexing of large serial fiber-optic Bragg grating sensor arrays","volume":"40","author":"Cooper","year":"2001","journal-title":"Appl. Opt."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"29038","DOI":"10.1364\/OE.23.029038","article-title":"Distributed OTDR-interferometric sensing network with identical ultra-weak fiber Bragg gratings","volume":"23","author":"Wang","year":"2015","journal-title":"Opt. Express"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1109\/LPT.2013.2241046","article-title":"High performance time domain FBG dynamic interrogation scheme based on pulse coding","volume":"25","author":"Zaidi","year":"2013","journal-title":"IEEE Photon. Technol. Lett."},{"key":"ref_6","first-page":"575","article-title":"Capacity of wavelength and time division multiplexing for quasi-distributed measurement using fiber BRAGG gratings","volume":"13","author":"Fajkus","year":"2015","journal-title":"Adv. Electr. Electron. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"471","DOI":"10.1364\/OL.38.000471","article-title":"High-performance hybrid Raman\/fiber Bragg grating fiber-optic sensor based on simplex cyclic pulse coding","volume":"38","author":"Taki","year":"2013","journal-title":"Opt. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"167089","DOI":"10.1109\/ACCESS.2019.2953512","article-title":"Improving the signal-to-noise ratio of time domain fiber BRAGG grating sensor based on hybrid simplex and golay coding technique","volume":"7","author":"Elgaud","year":"2019","journal-title":"IEEE Access"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"25330","DOI":"10.1364\/OE.27.025330","article-title":"Noise resilient quasi-distributed sensing with an interferometric-noise-suppressing Golay coded optical source","volume":"27","author":"Fu","year":"2019","journal-title":"Opt. Express"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1109\/JLT.2005.859437","article-title":"Optimization of SNR improvement in the noncoherent OTDR based on simplex codes","volume":"24","author":"Lee","year":"2006","journal-title":"J. Lightw. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1109\/50.17729","article-title":"Real-time long range complementary correlation optical time domain reflectometer","volume":"7","author":"Nazarathy","year":"1989","journal-title":"J. Lightw. Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3338","DOI":"10.1109\/JLT.2012.2215578","article-title":"A dual golay complementary pair of sequences for improving the performance of phase-shift pulse BOTDA fiber sensor","volume":"30","author":"Zan","year":"2012","journal-title":"J. Lightw. Technol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"094025","DOI":"10.1088\/0957-0233\/24\/9\/094025","article-title":"The use of Walsh code in modulating the pump light of high spatial resolution phase-shift-pulse Brillouin optical time domain analysis with non-return-to-zero pulses","volume":"24","author":"Zan","year":"2013","journal-title":"Meas. Sci. Technol."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Hassan, K.N.A.K., Elgaud, M., Su\u2019Ait, M.S., Bakar, A.A.A., and Zan, M.S.D. (2018, January 9\u201311). Signal to noise improvement ratio of TDM-FBG sensor based on golay complementary codes. Proceedings of the 2018 IEEE 7th International Conference on Photonics (ICP), Langkawi, Malaysia.","DOI":"10.1109\/ICP.2018.8533179"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"447","DOI":"10.1016\/j.yofte.2017.06.007","article-title":"Improvement of signal to noise ratio of time domain mutliplexing fiber Bragg grating sensor network with Golay complementary codes","volume":"36","author":"Elgaud","year":"2017","journal-title":"Opt. Fiber Technol."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Zan, M.S.D., Elgaud, M.M., Abushagur, A.A.G., Hamzah, A.E., Teo, J.W.S., Kiew, W.Y., Mokhtar, M.M., Arsad, N., and Bakar, A.A.A. (June, January 12). Spatial resolution enhancement of time domain multiplexing fiber Bragg grating sensor by employing differential golay codes. Proceedings of the 2020 IEEE 8th International Conference on Photonics (ICP), Kota Bharu, Malaysia.","DOI":"10.1109\/ICP46580.2020.9206502"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2002","DOI":"10.3390\/s21062002","article-title":"Bakar cantilever beam with a single fiber bragg grating to measure temperature and transversal force simultaneously","volume":"21","author":"Abdulfatah","year":"2021","journal-title":"Sensors"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Zaidi, F., Nannipieri, T., and Di Pasquale, F. (2015, January 20\u201322). High performance fiber optic sensor based on self referenced FBGs and high-speed dual-wavelength pulse coding. Proceedings of the Fifth Asia-Pacific Optical Sensors Conference International Society for Optics and Photonics, Jeju, Korea.","DOI":"10.1117\/12.2184148"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"70","DOI":"10.1109\/LPT.2010.2089676","article-title":"A quasi-distributed sensing network with time-division-multiplexed fiber Bragg gratings","volume":"23","author":"Wang","year":"2011","journal-title":"IEEE Photon. Technol. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"670","DOI":"10.1364\/OE.25.000670","article-title":"TDM interrogation of intensity-modulated USFBGs network based on multichannel lasers","volume":"25","author":"Rohollahnejad","year":"2017","journal-title":"Opt. Express"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1752","DOI":"10.1109\/LPT.2009.2032780","article-title":"Time delay measurements as promising technique for tilted fiber Bragg grating sensors interrogation","volume":"21","author":"Pisco","year":"2009","journal-title":"IEEE Photon. Technol. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"7171","DOI":"10.1364\/OE.21.007171","article-title":"Time-frequency analysis of long fiber Bragg gratings with low reflectivity","volume":"21","author":"Sancho","year":"2013","journal-title":"Opt. Express"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"17882","DOI":"10.1364\/OE.16.017882","article-title":"Quasi-distributed refractometer using tilted Bragg gratings and time domain reflectometry","volume":"16","author":"Caucheteur","year":"2008","journal-title":"Opt. Express"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"536","DOI":"10.1080\/09500340.2021.1925764","article-title":"Flat frequency comb generation employing cascaded single-drive Mach\u2013Zehnder modulators with a simple analogue driving signal","volume":"68","author":"Fadhel","year":"2021","journal-title":"J. Mod. Opt."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1109\/TIT.1961.1057620","article-title":"Complementary series","volume":"7","author":"Golay","year":"1961","journal-title":"IEEE Trans. Inf. Theory"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Pitas, I., and Venetsanopoulos, A.N. (1990). Nonlinear Digital Filters, Springer Science and Business Media LLC.","DOI":"10.1007\/978-1-4757-6017-0"},{"key":"ref_27","unstructured":"Ling, W.-K. (2007). Nonlinear Digital Filters: Analysis and Applications, Academic Press. [1st ed.]."},{"key":"ref_28","unstructured":"Smith, S.W. (2003). Digital Signal Processing: A Practical Guide for Engineers and Scientists, Newnes."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1573","DOI":"10.1139\/v95-195","article-title":"Application of median filtering to noisy data","volume":"73","author":"Stone","year":"1995","journal-title":"Can. J. Chem."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Lai, E. (2004). Practical Digital Signal Processing for Engineers and Technicians, Newnes.","DOI":"10.1016\/B978-075065798-3\/50009-6"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Kordestani, H., and Zhang, C. (2020). Direct use of the Savitzky-Golay filter to develop an output-only trend line-based damage detection method. Sensors, 20.","DOI":"10.3390\/s20071983"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"669","DOI":"10.1063\/1.4822961","article-title":"Savitzky-Golay smoothing filters","volume":"4","author":"Press","year":"1990","journal-title":"Comput. Phys."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1016\/j.dsp.2011.11.004","article-title":"Time-domain analysis of the Savitzky-Golay filters","volume":"22","author":"Quan","year":"2012","journal-title":"Digit. Signal Process."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1109\/82.486465","article-title":"Weighted median filters: A tutorial","volume":"43","author":"Yin","year":"1996","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_35","unstructured":"(2011). IEEE Standard for Transitions, Pulses, and Related Waveforms, IEEE."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Hamzah, A.E., Zan, M.S.D., Elgaud, M., Fadhel, M.M., Alwash, S.A., Abushagur, A.A., Mokhtar, M.H.H., Azeman, N.H., bin Mohd Ali, S.H., and Bakar, A.A.A. (June, January 12). Signal generation using system on chip for coded fiber Bragg grating sensor. Proceedings of the 2020 IEEE 8th International Conference on Photonics (ICP), Kota Bharu, Malaysia.","DOI":"10.1109\/ICP46580.2020.9206478"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Nordin, N.D., Zan, M.S.D., and Abdullah, F. (2020). Comparative analysis on the deployment of machine learning algorithms in the distributed brillouin optical time domain analysis (BOTDA) Fiber sensor. Photonics, 7.","DOI":"10.3390\/photonics7040079"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/13\/4299\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:22:23Z","timestamp":1760163743000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/13\/4299"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,6,23]]},"references-count":37,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2021,7]]}},"alternative-id":["s21134299"],"URL":"https:\/\/doi.org\/10.3390\/s21134299","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,6,23]]}}}