Browsing by Author "Ozdur, Ibrahim"

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94.8 Km-Range Direct Detection Fiber Optic Distributed Acoustic Sensor
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 01.01.2019) Uyar, Faruk; Onat, Talha; Unal, Canberk; Unal, Canberk; Ozdur, Ibrahim; Ozbay, Ekmel; 0000-0003-3552-1650; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
This 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. (C) 2019 The Author(s)
Absolute phase noise analysis of a harmonically modelocked semiconductor laser
(Optica Publishing Group (formerly OSA), 2017) Ozharar, Sarper; Ozdur, Ibrahim; 0000-0001-6452-0804; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Ozdur, Ibrahim
We have designed and built a fiber coupled semiconductor laser at 1550 nm, which is harmonically mode-locked at 10 GHz by an external RF oscillator. The absolute phase noise of the laser is measured and discussed for two different cavity lengths.
Amplitude noise suppression by intracavity phase modulation in a harmonically mode-locked laser
(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2018) Ozharar, Sarper; Ozdur, Ibrahim; 0000-0001-6452-0804; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
A fiber coupled semiconductor ring laser that employs both an amplitude and a phase modulator was built and actively harmonic mode-locked at a repetition rate of 10 GHz. The phase modulator was driven at the cavity fundamental frequency and its effects on the optical spectrum and the optical pulse train were analyzed. The intracavity phase modulation at the cavity fundamental frequency resulted in 40% lower optical pulse amplitude fluctuations and improved the stability of the optical spectrum. (C) 2018 Elsevier Ltd. All rights reserved.
Analysis of oscillator phase noise effect on high order QAM links
(SPRINGER, VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS, 2020) Bicici, Cagri; Ozdur, Ibrahim; Cerezci, Osman; 0000-0001-6624-4874; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
In this work, the effect of oscillator phase noise on the bit error rate (BER) for high order QAM communication systems is analyzed. Two high frequency oscillators are designed, built and tested to get real phase noise data, and a BER simulation of a 1024 QAM signal through a super-heterodyne frequency down-converter is implemented using the measured data from the two oscillators as local oscillator sources for the down-converter. A third frequency source is also added to the simulation to visualize the dramatic effect of phase noise on the system BER analysis.
A Direct Detection Fiber Optic Distributed Acoustic Sensor With a Mean SNR of 7.3 dB at 102.7 km
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA, 2019) Uyar, Faruk; Onat, Talha; Unal, Canberk; Kertelog, Tolga; Ozbay, Ekmel; Ozdur, Ibrahim; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
In this work, we present the experimental results of a direct detection phi-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 similar to 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 phi-OTDR based distributed acoustic sensor system.
The Effects of Intracavity Phase Modulation and Extracavity Optical Filtering on Amplitude Noise of Mode-Locked Pulse Trains
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 2018) Ozharar, Sarper; Ozdur, Ibrahim; 0000-0001-6452-0804; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
An actively mode-locked, fiber-coupled semiconductor ring laser that employs both a phase modulator and an amplitude modulator was built. The laser was mode locked by loss modulation at 10 GHz and the intracavity phase modulator was driven at the cavity fundamental frequency of 1.63 MHz. The effects of the intracavity phase modulation on the stability of the optical spectrum, the timing jitter, and the amplitude noise of the pulse train was analyzed. It was found that using this method, the amplitude fluctuation can be reduced by 40%, and the stability of the optical spectrum can be improved while keeping the phase noise of the system unchanged.
Field Test and Fading Measurement of a Distributed Acoustic Sensor System over a 50 km-long Fiber
(SPIE-INT SOC OPTICAL ENGINEERING, 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA, 2018) Uyar, Faruk; Kartaloglu, Tolga; Ozdur, Ibrahim; Ozbay, Ekmel; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
In this study, we present a direct detection distributed acoustic sensor based on phase-sensitive optical time domain reflectometer (phi-OTDR) with long sensing range and high signal-to-noise ratio (SNR), which is field-tested over a 50 km-long 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 phi-OTDR system exhibits a mean SNR of 22.5 dB at 50 km distance.
The Investigation of Rayleigh Backscattered Signal Statistics in a phi-OTDR System Incorporating Optical Pre-Amplifier
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 2020) Uyar, Faruk; Kartaloglu, Tolga; Ozbay, Ekmel; Ozdur, Ibrahim; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
We theoretically model and experimentally demonstrate the photon statistics of Rayleigh backscattered signal in a phi-OTDR based distributed fiber optical sensor in the presence of amplified spontaneous emission noise caused by optical pre-amplifier.
Magnetic-particle based signal amplification method integrated with mobile-devices for low cost biosensing
(ELSEVIER SCIENCE BV, SARA BURGERHARTSTRAAT 25, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2017) Mzava, Omary; Tas, Zehra; Lafci, Vahit Can; Cakar, Mehmet Akif; Ozdur, Ibrahim; Icoz, Kutay; AGÜ, Mühendislik Fakültesi, Mühendislik Bilimleri Bölümü;
We present a signal amplification method for biosensing applications using magnetic particles. In this method, mobile devices and simple spherical glass beads are used as a low-cost microscope to detect magnetic particles. Magnetic particles have two main functions; 1) conventionally capture, separate and transport target molecules 2) form magnetic dipoles under an applied external magnetic field to attract other magnetized particles. When magnetic particles accumulate and form a cluster, the corresponding pixel area in the image taken by the simple microscope is increased resulting in signal amplification. Current focus of new generation biosensor research is to increase the sensitivity levels of the devices to compete with current lab analysis tools while inherently having other advantages such as being low-cost, portable and simple. Biosensors based on micro/nano magnetic particles use various measurement techniques and amplification methods. In order to fully benefit from the advantages of micro/nano technology based systems, measurement set up must be also portable and have high sensitivity. Mobile devices and applications are taking place in medical fields and have high potential for future. In this work mobile devices are employed as measurement setups for the magnetic particle based sensing and signal amplification. The amplification method is not based on bimolecular binding thus cost efficient. After the images of the magnetic particles are taken, these images are sent to cloud computing for analysis by the mobile device. Matlab codes run on cloud servers for processing the images. Finally results are received and displayed on the mobile device. The mobile device based imaging system is able to detect 7 mu m size particles within a 1500 mu m x1500 mu m area and magnetic bead accumulation resulted in at least 5-fold signal amplification. The applied magnetic field is approximately 15 mT and the cost of the system excluding mobile device is under 20 cents. The method is promising for immunomagnetic bead assisted biosensors. (c) 2016 The Authors. Published by Elsevier Ltd.
Photonic-lantern-based coherent LIDAR system
(OPTICAL SOC AMER, 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA, 2015) Ozdur, Ibrahim; Toliver, Paul; Woodward, Ted K.; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
In this work, a photonic-lantern-based coherent LIDAR system is experimentally demonstrated and the voltage signal-to-noise ratio improvement is analyzed. A voltage signal-to-noise ratio (SNRV) improvement of 2.8 is demonstrated experimentally for photonic-lantern-based coherent receivers relative to single-mode coherent receivers. The voltage signal-to-noise ratio improvement is obtained when other parameters are kept constant. We have also analyzed the effect of random optical power distribution among the single-mode fibers. We found that the distribution does not significantly impact the SNRV improvement. The mean value of voltage signal-to-noise ratio improvement is found to be similar to 2.4. (C) 2015 Optical Society of America
RF injection locked 18 GHz regeneratively mode-locked semiconductor laser
(OPTICAL SOC AMER, 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA, 2018) Oran, Abdullah; Ozharar, Sarper; Can, Gokhan; Olcer, Ibrahim; Ozdur, Ibrahim; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
In this manuscript, a semiconductor based fiber ring cavity mode-locked laser regeneratively driven at 18 GHz is presented. The optical spectrum of the laser is centered at 1578 nm. The laser is RF injection locked via an external source at 18 GHz. The phase noise of the mode-locked laser is measured and the integrated timing jitter was found to be 10.8 fs (from 100 Hz to 20 MHz) and 13.3 fs (from 100 Hz to Nyquist frequency). The integrated amplitude fluctuation (from 100 Hz to 20 MHz) was less than 0.02%. The laser phase and amplitude noise responses to various injected RF power levels were also investigated. The injection RF power has significant effect on the phase noise and the best jitter value is around 40 dB lower than the cavity regenerated RF power. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
RF phase noise filtering properties of an actively mode-locked laser
(WILEY, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA, 2018) Mbonde, Hamidu; Ozharar, Sarper; Ozdur, Ibrahim; 0000-0001-6452-0804; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
In this article, we are presenting the experimental results and theoretical analysis of radio frequency (RF) phase noise filtering properties of a high Q cavity actively driven mode-locked laser. The experimental results show that, the phase noise of a 10 GHz RF tone can be filtered by at least 10 dB at 200 kHz offset frequency. A theoretical analysis on the limits of phase noise filtering due to the spontaneous emission and the frequency mismatch between the laser cavity modes and the synthesizer frequency is also included.
A Simple Method for Enhancing the SNR in Direct Detection (p-OTDR based Distributed Acoustic Sensors
(IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 2020) Uyar, Faruk; Kartaloglu, Tolga; Unal, Canberk; Ozbay, Ekmel; Ozdur, Ibrahim; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü
A simple and effective method for increasing the SNR and range in fp-OTDR based direct -detection distributed acoustic sensors is proposed and experimentally verified. The proposed method results in 11 dB SNR improvement at 66 km. (fD 2020 The Author(s)
Simultaneous low noise radio frequency tone and narrow linewidth optical comb generation from a regeneratively mode-locked laser
(SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA, 2014) Ozdur, Ibrahim; Ozharar, Sarper; Delfyett, Peter J.; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
A regeneratively mode-locked laser with simultaneous low noise radio frequency (RF) tone and optical comb generation is presented. The laser does not need any external RF signal and emits a pulse train at similar to 10 GHz repetition rate with a 1.5-ps optical pulse width after compression. The generated RF tone has a signal-to-noise ratio of 121 dB/Hz and an RF fluctuation of 10(-9) over 0.1 s. The optical frequency comb spacing is also at similar to 10 GHz and the optical comb tooth has a linewidth of <1 kHz. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)