TY - CONF A1 - Eisermann, René A1 - Rohwetter, Philipp A1 - Hicke, Konstantin ED - Chung, Youngjoo ED - Jin, Wei ED - Lee, Byoungho ED - Canning, John ED - Nakamura, Kentaro ED - Yuan, Libo T1 - Reducing sensitivity fading in C-OTDR by use of enhanced scattering fiber segments N2 - We have shown that for C-ODTR based DAS two UV-inscribed scattering segments within an optical fiber have a significant influence on the local sensitivity Fading characteristics. This method was experimental proven to be suitable for distributed dynamic strain measurement in a thermally unstable environment. Signal-to-noise ratio analyses for detecting a signal peak within the time-dependent spectra were performed. Results show an increase in SNR and additionally that the occurrence of total loss of sensitivity (SNR <1) could be decreased by a factor of six when compared to an untreated standard fiber. We have shown that for C-ODTR based DAS two UV-inscribed scattering segments within an optical fiber have a significant influence on the local sensitivity Fading characteristics. This method was experimental proven to be suitable for distributed dynamic strain measurement in a thermally unstable environment. Signal-to-noise ratio analyses for detecting a signal peak within the time-dependent spectra were performed. Results show an increase in SNR and additionally that the occurrence of total loss of sensitivity (SNR <1) could be decreased by a factor of six when compared to an untreated standard fiber. T2 - 25th International Conference on Fiber Optic Sensors CY - Jeju-City, Jeju, Republic of Korea DA - 24.04.2017 KW - Coherent Rayleigh OTDR, KW - Distributed acoustic sensing KW - Distributed vibration sensing KW - Fiber sensors KW - Quasi-distributed sensing KW - Rayleigh scattering PY - 2017 DO - https://doi.org/10.1117/12.2267659 SN - 0277-786X SN - 1996-756X VL - 10323 SP - 103239N-1 EP - 103239N-4 PB - SPIE CY - Bellingham, WA, USA AN - OPUS4-40642 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eisermann, René T1 - Reducing sensitivity fading in C-OTDR by use of enhanced scattering fiber segments N2 - We have shown that for C-ODTR based DAS two UV-inscribed scattering segments within an optical fiber have a significant influence on the local sensitivity Fading characteristics. This method was experimental proven to be suitable for distributed dynamic strain measurement in a thermally unstable environment. Signal-to-noise ratio analyses for detecting a signal peak within the time-dependent spectra were performed. Results show an increase in SNR and additionally that the occurrence of total loss of sensitivity (SNR <1) could be decreased by a factor of six when compared to an untreated standard fiber. T2 - 25th International Conference on Optical Fiber Sensors CY - Jeju-City, Jeju, Republic of Korea DA - 24.04.2017 KW - Coherent Rayleigh OTDR KW - Distributed acoustic sensing KW - Distributed vibration sensing KW - Fiber sensors KW - Quasi-distributed sensing KW - Rayleigh scattering PY - 2017 AN - OPUS4-40643 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lu, Xin T1 - Humidity response analysis of optical fibers with hygroscopic coatings based on Lamé’s equations N2 - Optical fibers with hygroscopic coatings are widely used for humidity sensing, where the coating expands upon absorbing water, inducing strain in the fiber. This strain is then used to determine humidity. However, previous studies have oversimplified the strain generation process. A comprehensive three-dimensional model of the mechanical interaction between the coating and the fiber is built based on Lamé’s equations. An analytical expression for the induced strain is derived. The proposed model predicts larger humidity-induced strain compared to the reported ones, given the same Young’s modulus or coefficient of humidity expansion for the coating. Interestingly, the effect of coating thickness on strain response are quite similar for both methods. Experimental validation using fibers with a polyimide coating shows strong agreement with the theoretical predictions. T2 - 29th International Conference on Optical Fiber Sensors CY - Porto, Portugal DA - 26.05.2025 KW - Distributed fiber sensing KW - Humidity sensors KW - Lamé’s equations KW - Reflectometry KW - Optical fiber sensors KW - Rayleigh scattering KW - Structural health monitoring PY - 2025 AN - OPUS4-63261 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liehr, Sascha T1 - Distributed Humidity Sensing in PMMA Polymer Optical Fibers N2 - The distributed measurement of relative humidity is a sought-after capability for a wide range of applications in civil engineering and structural health monitoring. We show that polymethyl methacrylate (PMMA) optical fi-bers can be employed as a sensor medium to conduct distributed humidity measurement by analyzing Rayleigh backscattering traces obtained by OTDR. We make use of the effect that water penetrates the fiber core and directly influences the local fiber attenuation and Rayleigh backscatter coefficient. We conducted distributed backscattering analysis for two different pulse wavelengths: 500 nm and 650 nm. The 650 nm results are susceptible to both, attenuation changes and backscatter changes, whereas backscatter results at 500 nm are not affected by humidity-induced attenuation and only exhibit a change of Rayleigh backscattered power as a function of humidity. The combined measurement and analysis of both parameters at these two wavelengths has the advantage that cross-sensitivities on backscatter change and attenuation, such as strain and tempera-ture changes, could be separated from the humidity response of the fiber. We present laboratory results for a humidity range between 30% and 90% for both pulse wavelengths: including step responses, humidity cycles and hysteresis analysis. In addition to the attenuation and backscatter coefficient dependence, we also analyze optical runtime changes as a function of humidity. POFs have the advantage that they can be directly embed-ded into materials such as concrete or soil to measure water content or localize water ingress. Standard step-index PMMA POFs can be used as a distributed relative humidity sensor up to 200 m distance. T2 - The 28th International Conference on Plastic Optical Fibers CY - Yokohama, Japan DA - 20.11.2019 KW - Distributed humidity sensor KW - PMMA KW - Rayleigh scattering KW - Polymer optical fiber KW - Distributed sensor KW - Optical fiber sensor KW - OTDR PY - 2019 AN - OPUS4-49868 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -