Özet Metin
In this study, we have theoretically and experimentally analyzed gain clamping and gain spectrum flattening performance in L-Band EDFAs based on a lasing-controlled structure using a symmetrical FBG couple at C-Band. Its performance was compared with a single-stage bidirectionally pumped conventional L-Band EDFA design. By optimizing the reflection (Bragg) wavelength of the FBG, a wide gain-clamped dynamic range (33 dB) and a wide gainflattened spectrum (35 nm) were obtained at a maximum gain of 19.70 dB. Our results have shown that the experimental results are highly consistent with the theoretical and simulation results. Consequently, the proposed L-Band EDFA design using a lasing-controlled structure with FBGs can provide a wide gain clamped and gain flattened operation in the desired signal power levels.
Anahtar Kelimeler
L-EDFA, gain clamped/flatness, FBG
Özet Metin
In this study, we present the gain and noise figure performance improvement in L-band erbium-doped fiber amplifier (L-EDFA) provided by amplified spontaneous emission (ASE) reinjection through different configurations of 1533 nm band FBGs. The experimental results are compared with a single-stage bidirectionally pumped conventional L-EDFA design. It is shown that when the forward and/or the backward ASE noise is partly reinjected to L-EDFA using a double/single 1533 nm fiber Bragg gratings (FBG), the gain and noise figure performance of L-EDFA increases depending on the FBG configuration. The best gain and NF performance in our L-EDFA was achieved by reinjection of forward and backward ASE through FBG1 and FBG2 leading to an 4.5 dB increase in gain and 1 dB decrease in NF at 1585 nm and −30 dBm input signal power. The results show that both FBGs must be used at the same time to improve gain and NF performance in L-band EDFAs.
Anahtar Kelimeler
Erbium doped fiber amplifier Fiber Bragg grating Gain improvement L-band EDFA
Özet Metin
In this study, a precise optical fiber length measurement system is proposed. The measurement technique is based on the measurement of relative Fresnel reflected light intensity in a test fiber. Time delayed optical reflected pulses are obtained from a single nanosecond pulse injected at the input due to the difference in lengths of the reference and test fibers. The lengths of the different optical fibers have been measured with this technique with high resolution and fast response time. The measured results show that, the proposed technique has a comparable performance with the well-known length measurement systems.
Anahtar Kelimeler
Fresnel reflection, nanosecond pulse, optical fi ber length measurement, time delayed pulses.
Özet Metin
In this letter, a universal, simple, and stable all-fiber sensor system is proposed to measure the refractive index (RI) of liquids. The basic principle of the technique is based on the relative measurement of the Fresnel reflection from sensor probes. A quadruple of time-division multiplexed Fresnel reflected pulses are obtained from a single nanosecond input pulse owing to the latencies in fibers with different lengths. The measured RIs for the different liquids show that the proposed all-fiber RI sensor system enables linear and repeatable measurements. The performance of the system is compared with the previously published studies, and good agreement is observed, showing the accuracy of the measurements. The standard deviations of the measured RIs are obtained in a short-term measurement as 2.8 × 10−6 for distilled water, and in a long-term measurement as 2.99×10−5 for methanol, showing the high repeatability of the measurements.
Anahtar Kelimeler
Fresnel reflection, optical fiber sensor, refractive index sensing.
Özet Metin
The electrical arc technique is a flexible, easily applicable and cost-effective technique, in which fiber is written to form a grating structure using electrical arc-discharges during mechanical motion. In this study, an experimental set up is proposed to product long period fiber gratings (LPFG) and the design parameters that affect the process are investigated. After the first experimental study on production of a typical LPFG, the research is directed on smoothing the gain spectrum of erbium doped fiber amplifiers using LPFG. The research results and experimental findings demonstrate that LPFGs manufactured using electrical arc technique can provide positive a effect on smoothing the gain spectrum of an EDFA.
Anahtar Kelimeler
Long period fiber grating, electrical arc technique, EDFA gain.
Özet Metin
Measurement of refractive index which is one of the distinctive properties of materials is commonly used in many fields such as industrial and biomedical applications. From the refractive index measurement methods, the one based on fiber optic stands out with their provided advantages. In this study, firstly a simple, reliable and sensitive Fresnel reflection based fiber optic refractometer was setup, then the refractive indexes of various liquids were measured using this setup at different times. When the measurement results are compared with the results taken with a reference Abbe Refractometer, the deviation ratio was found to be less than %1.
Anahtar Kelimeler
Fiber optic, Refractive index, Fresnel reflection, Refractometer
Özet Metin
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Özet Metin
In long-haul and high-bit-rate optical fiber transmission systems Polarization Mode Dispersion (PMD) is one of the main reasons for pulse broadening. In order to reduce PMDbased problems, current studies rely on novel PMD compensators and low-PMD fiber productions. In this paper, after describing theoretical information about PMD and optical fiber spinning process, different spin profiles are examined. Comparative analysis of spin profiles is made and spin parameters giving successful results for low-PMD fibers are obtained for each spin profile. Simulation results show that for fixed spin period of 1 m 2.76 turns/m and 5.64 turns/m are proper spin amplitude values for sinusoidal and amplitude modulated (AM) spin profiles, respectively, while 3.40 turns/m and 3.75 turns/m are recommended spin amplitudes for triangular and trapezoidal spin profiles, respectively. Using these parameters, related spin profiles give better differential group delay (DGD) reduction results individually.
Anahtar Kelimeler
Özet Metin
Fiber optical sensors have become popular among the current sensor technologies due to their some advantages. In this study, the sensitivity and selectivity of reflection type fiber optical sensors are investigated using the sensing materials of CuPc, H2Pc, CoPc and PVP synthesized by TÜBİTAK Marmara Research Centre Sensor Group. The developed fiber optical volatile organic compounds (VOC) sensors are used to detect some common industrial VOC such as O-Xylene, Acetone, Chloroform, Trichloroethylene, Acetonitrile and Propanol. The basic principle of the sensor structure is based on the optical reflections occurring from the sensing layer at the fiber end which depends on the amount of VOC absorbed. The relative changes in the reflected power depending on the refractive index change in the nano cavity interferometrical sensing layer was analyzed through the simulations and then experimentally measured for four types of optical fiber VOC sensors.
Anahtar Kelimeler
Optical Fiber Sensors, VOC Sensor, Optical Thin Films.
Özet Metin
Measurement of refractive index which is one of the distinctive properties of materials is commonly used in many fields such as quality control of food industry, biomedical applications, biochemical analysis and measurement of environmental pollution. From the refractive index measurement methods, the one based on fiber optic stands out with their provided advantages. In this study, firstly, a simple, reliable and highly sensitive Fresnel reflection based fiber optic refractometer was setup, then the refractive indexes of various liquids were measured using this setup at different times. When the measurement results are compared with material science data sheet (MSDS) values, the percent error was found to be less than %1. Moreover, the long term stability of ethanol’s refractive index was examined and the refractive index variation of salt-water was obtained as a function of the salt concentration.
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Özet Metin
Optical fiber technology is widely used in sensor applications as well as its usage in communication systems due to their important advantages. In this study, a novel and simple optical fiber sensor structure has been developed by coating the surface of a multimode optical fiber ST connector with a PVP (polyvinylpyrrolidone) thin film which is sensitive to different volatile organic compounds (VOCs). Depending on the type and the amount of VOC sensed, Fresnel reflection occurring at the sensor coating changes. The proposed sensor structure based on this fundamental principle was tested using a wavelength independent optical experimental setup. The results obtained have shown that the developed sensor structure can widely be used in various industrial applications due to their high selectivity, sensitivity and reproducibility performance to detect and measure the different VOCs such as acetone, acetonitrile, propanal, oXylene and trichloroethylene.
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Özet Metin
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Özet Metin
Erbiyum katkılı fiber yükselteçler (EDFA), optik haberleşme sistemlerinde önemli rol oynamaktadır. Ancak, yoğun dalgaboyu bölmeli çoğullama (DWDM) sistemlerinde, yüksek kapasiteli bilgi iletim ihtiyacını karşılamak için EDFA’ların çalışma bandgenişliklerinin klasik-banttan (C-Band), uzun-dalgaboyu bandına (L-Band) genişletilmesine ihtiyaç vardır. DWDM sistemlerinde, optik kanalın eklenmesi ya da çıkarılması durumunda, EDFA kazancı dolayısıyla optik kanalların çıkış gücü değişebilmektedir. Eğer EDFA’da herhangi bir kazanç kontrol mekanizması kullanılmazsa, bu durum haberleşme sisteminin genel performansında dalgalanmalara yol açmaktadır. Bu sebeple, giriş kanallarının gücü, dalgaboyu veya sayısının değişimlerine dirençli kazanç kenetlemeli ve kazanç spektrumu düzleştirilmiş genişband EDFA tasarımları gerekmektedir. Bu çalışmada, C-bandında simetrik FBG çifti kullanılarak gerçekleştirilen lazer kavite kontrollü L-band EDFA’nın kazanç kenetleme ve kazanç spektrumu düzleştirme performansı teorik ve deneysel olarak analiz edilmiş ve tek katlı çift yönlü pompalamalı klasik L-Band EDFA tasarımı ile kıyaslanmıştır. Kazanç kenetlemeli ve kazanç spektrumu düzleştirilmiş L-Band EDFA tasarımında kullanılan FBG çiftinin Bragg yansıtma dalgaboyu optimize edilerek, geniş bir kazanç kenetlemeli dinamik aralık (~33 dB) ve düzleştirilmiş kazanç spektrumu (~35nm) 19.70 dB’lik ortalama kazanç değeri ile elde edilmiştir. Çalışmada elde edilen deneysel sonuçlar, teorik analiz sonuçları ile oldukça uyumludur. Sonuç olarak, genişband çok kanallı fiber optik haberleşme sistemlerinde ihtiyaç duyulan kazanç kenetlemeli ve düzgün kazanç spektrumlu L-Band kazancın önerilen L-Band EDFA tasarımıyla yüksek performanta gerçekleştirilebileceği anlaşılmıştır.
Anahtar Kelimeler
Erbiyum katkılı fiber yükselteçler, fiber Bragg ızgara (FBG), kazanç kenetleme, kazanç spektrumu düz
Özet Metin
Fiber optik sistemler günümüzde, haberleşme sistemlerinde olduğu kadar sensör teknolojilerinde de önemli bir uygulama alanına sahiptir. Fiber optik sensörler hızlı tepki verme, yüksek duyarlılık, elektriksel izolasyon, uzaktan algılamada düşük sinyal kaybı, küçük ebatlı olma gibi özellikleri sayesinde klasik sensörlere göre gelişen teknolojide ön plana çıkmaktadırlar. Bu çalışmada, çok modlu fiber optik ST konnektörlerin yüzeyi endüstriyel uygulamalarda kullanılan farklı uçucu organik bileşenlere duyarlı ftalosiyanin ve PVP tabanlı çeşitli malzemeler ile kaplanarak yeni fiber optik sensör yapıları elde edilmiştir. Algılanan gazın cinsi ve miktarına göre sensör yüzeyindeki optik Fresnel yansıması ve diğer interferometrik yansımalarda değişim meydana gelmektedir. Öncelikli olarak geliştirilen dört farklı sensör tipi için, uçucu organik bileşenlere karşı duyarlı olup olmadığı yapılan ön çalışmalar ile test edilmiştir. Elde edilen olumlu sonuçlardan sonra universal bir ölçüm düzeneği geliştirilerek ppm gaz miktarına göre dört farklı sensör tipinin farklı uçucu organik bileşenlere karşı tepkileri ölçülmüştür. Alınan sonuçlar irdelendiğinde değişen uçucu organik bileşen miktarına bağlı olarak, sensörlerin farklı seçicilik ve duyarlılıkta tepkiler verdiği gözlemlenmiştir.
Anahtar Kelimeler
Fiber optik sensör, Fresnel yansıması, uçucu organik bileşen sensörü, gaz sensörü.