Browsing by Author "Uyar, Faruk"
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Item Unknown 94.8 km-range direct detection fiber optic distributed acoustic sensor(Optical Society of America(OSA), 2019) Uyar, Faruk; Uyar, Talha; Ünal, Canberk; Kartaloğlu, Tolga; Özdur, İbrahim; Özbay, EkmelThis work demonstrates an ultra-long range direct detection fiber optic distributed acoustic sensor which can detect vibrations at a distance of 94.8 km with 10 m resolution along the sensing fiber.Item Unknown Development and characterization of a direct detection fiber optic distributed acoustic sensor(Bilkent University, 2018-09) Uyar, FarukPhase-sensitive optical time domain re ectometer (ø-OTDR) based distributed acoustic sensor (DAS) systems have attracted increasing attention in recent years due to their remarkable advantages in a wide range of industrial and military applications such as health monitoring and security of civil infrastructures, railways, oil and gas pipelines, borders, and so on. They measure vibrations and detect perturbations along a section of fiber. Different approaches have been adopted to realize the ø-OTDR systems and process the data from these sensors. In this thesis, a direct detection DAS based on ø-OTDR architecture with long sensing range and high signal-to-noise ratio (SNR) is demonstrated. Testing and characterization of critical system components is conducted before integrating them into the system. The results of laboratory tests are presented, in which the detected traces are successively analyzed in order to localize and investigate the perturbation events along the test fibers. The field tests are demonstrated with different external events such as digging, walking, and motor vibration. Considering the random nature of Rayleigh backscattered light and fading effect encountered in these tests, a new performance metric, which is Mean SNR, is proposed for assessing and comparing the system performances. Besides, statistical characteristics of the SNR of the vibration events in different distances for both laboratory tests and field tests is experimentally measured. The photon statistics of Rayleigh backscattered signal in a ø-OTDR based fiber sensor in the presence of amplified spontaneous emission noise is theoretically modeled and experimentally demonstrated, as well.Item Open Access A direct detection fiber optic distributed acoustic sensor with a mean SNR of 7.3 dB at 102.7 km(Institute of Electrical and Electronics Engineers Inc., 2019) Uyar, Faruk; Onat, Talha; Ünal, Canberk; Kartaloğlu, Tolga; Özbay, Ekmel; Özdür, İ.In this work, we present the experimental results of a direct detection π-OTDR based distributed acoustic sensor system. The system uses two cascaded acousto-optic modulators in order to generate optical pulses with very high extinction ratio and dual photodetector scheme for high dynamic range. The proposed schemes are investigated in detail and their performance enhancement is experimentally verified. Four piezoelectric based fiber stretchers are placed on a ~104 km single-mode test fiber at the distances of 1 km, 10 km, 87 km and 102.7 km and used for perturbation tests. The stretchers generated vibration signals which are analyzed to quantify the system performance. The signal-to-noise ratio (SNR) of vibration signals at the monitored distances is measured over the 12-hour recorded data within 34-second time windows considering the multi-point random interference of scattered light and fading phenomena. Using the 12-hour data, SNR histograms at four different locations are generated and mean SNR values are obtained. The signals received from 102.7 km has a maximum SNR of 24.7 dB and a mean SNR of 7.3 dB with a spatial resolution of 15 m. To the best of our knowledge, this is the highest-range reported direct detection π-OTDR based distributed acoustic sensor system.Item Unknown Field test and fading measurement of a distributed acoustic sensor system over a 50 km-long fiber(SPIE - International Society for Optical Engineering, 2018) Uyar, Faruk; Kartaloğlu, Tolga; Özdür, Ibrahim; Özbay, EkmelIn this study, we present a direct detection distributed acoustic sensor based on phase-sensitive optical time domain reflectometer (φ-OTDR) with long sensing range and high signal-to-noise ratio (SNR), which is field-tested over a 50 kmlong fiber. Due to the random nature of Rayleigh backscattered light and fading phenomena, it is hard to characterize the performance of the system. For this reason, the performance of our sensor is specified in a statistical manner in which the mean SNR is determined using the histograms of the SNR. The SNR values are measured for identical acoustic signals in five different days, total of 48 hours and the SNR histograms are obtained for fiber distances of 100 m, 12 km, 21 km, 30 km, 40 km and 50 km. The system is field-tested using external disturbances that are generated from a 50-Hz vibrator. The SNR values are extracted from the power spectral density (psd) of the collected data over the monitored fiber span. Our results show that the φ-OTDR system exhibits a mean SNR of 22.5 dB at 50 km distance.Item Open Access An investigation of fidelity regions in the dual-pulse 𝝓-OTDR systems(The Optical Society, 2021) Yıldız, Muhammed Kaan; Uyar, Faruk; Kartaloǧlu, Tolga; Ozdur, İ. T.; Özbay, EkmelThe dual-pulse interrogation enables the phase extraction from the intensity of the backreflection signal in 𝜙-OTDR systems. We investigate the high and low fidelity regions in the back-reflected signal by analyzing the system response to external disturbances.Item Open Access The investigation of Rayleigh backscattered signal statistics in a φ-OTDR system incorporating optical pre-amplifier(IEEE, 2020) Uyar, Faruk; Kartaloğlu, Tolga; Özbay, Ekmel; Özdur, İbrahimWe theoretically model and experimentally demonstrate the photon statistics of Rayleigh backscattered signal in a ϕ-OTDR based distributed fiber optical sensor in the presence of amplified spontaneous emission noise caused by optical pre-amplifier.Item Open Access A parity-time-symmetric optoelectronic oscillator with polarization multiplexed channels(Institute of Physics Publishing Ltd., 2022-04-05) Özgün, E.; Uyar, Faruk; Kartaloğlu, Tolga; Özbay, Ekmel; Özdür, İ.In this manuscript, we experimentally demonstrate a parity-time-symmetric optoelectronic oscillator (OEO) with polarization multiplexed channels. We obtained a microwave single-mode oscillation at 9.5 GHz with phase noise values of −116.2 and −122.3 dBc Hz−1 at 10 kHz offset frequencies, and side mode suppression values below −68 and −75 dBc Hz−1, by utilizing a 1 km long and 5 km long single mode fiber delay lines, respectively. Our experimental results suggest that parity-time-symmetric OEOs with polarization multiplexed channels are simple and cost-efficient alternatives to their more complex counterparts.Item Open Access The pulse shape effect on signal-to-noise ratio for φ-OTDR systems(Optica Publishing Group, 2021) Uyar, Faruk; Nehir, Anıl; Kartaloğlu, Tolga; Özbay, Ekmel; Özdur, İ.We experimentally investigate the effect of the probe pulse shape on the performance of φ-OTDR based distributed vibration sensors by comparing the SNR values for rectangular, Gaussian and triangular pulses.Item Open Access A Simple method for enhancing the SNR in direct detection φ-OTDR based distributed acoustic sensors(IEEE, 2020) Uyar, Faruk; Kartaloğlu, Tolga; Ünal, Canberk; Özbay, Ekmel; Özdur, İbrahimA simple and effective method for increasing the SNR and range in φ-OTDR based direct-detection distributed acoustic sensors is proposed and experimentally verified. The proposed method results in ~11 dB SNR improvement at 66 km.Item Open Access A simple parity-time-symmetric optoelectronic oscillator based on all-fiber coupling(The Optical Society, 2021) Özgün, Ege; Uyar, Faruk; Kartaloǧlu, Tolga; Özbay, Ekmel; Ozdur, İ. T.We experimentally demonstrate a simple parity-time-symmetric optoelectronic oscillator based on all-fiber coupling with single-mode microwave oscillation at 9.5 GHz possessing a phase noise value of −116.2 dBc/Hz at 10 kHz offset.Item Open Access Spatial resolution analysis of dual-pulse ϕ-OTDR systems(Optica Publishing Group, 2021) Yıldız, Muhammed Kaan; Uyar, Faruk; Kartaloğlu, Tolga; Özbay, Ekmel; Özdur, İ.This work analyzes the spatial resolution of the dual-pulse -OTDR systems by changing the dual-pulse parameters and demonstrates that the spatial resolution corresponds to half of the fiber region occupied by the dual-pulse train.