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This study presents two novel tunable erbium doped fiber ring laser (EDFRL) configurations based on loop EDFA design and double-pass EDFA design, respectively to achieve an ultra-wideband tuning range and stable single-longitudinal-mode lasing operation. A micro-electro-mechanical system (MEMS) based optical tunable band pass filter was utilized as the wavelength selection element. Output spectral and power characteristics of these EDFRLs were experimentally analyzed and discussed. The EDFRLs had moderate and stable output power level (~-3 dBm) over 70 nm tuning range that covers C+L band. Moreover, the proposed EDFRLs could also suppress the undesired multi-longitudinal-modes successfully and have a high (~60 dB) OSNR level in whole tuning range.
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Fiber ring laser Tunable laser source Erbium doped fiber
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EDFA,FBG
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optical fiber sensor
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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.
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Fresnel reflection, nanosecond pulse, optical fi ber length measurement, time delayed pulses.
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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.
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Long period fiber grating, electrical arc technique, EDFA gain.
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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.
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Fiber optic, Refractive index, Fresnel reflection, Refractometer
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In this study, we experimentally demonstrate a C+L band tunable erbium-doped fiber ring laser (EDFRL) based on a loop design of erbium-doped fiber amplifier (EDFA). With the proposed EDFRL architecture, the forward and backward amplified spontaneous emission (ASE) signals of a bi-directionally pumped loop EDFA are combined in a 3-dB coupler and redirected to the tunable ring laser through a wideband optical circulator. An optical tunable bandpass filter (TBPF) with a micro-electro-mechanical system (MEMS) is used in order to select lasing wavelength from a wide range from 1525 nm to 1610 nm. In this study, firstly, the length of erbium-doped fiber (EDF) is changed to optimize the laser output power and the tuning wavelength range while the output tap coupler ratio is 50%. The results have shown that six-meter of EDF has a wider tuning wavelength range and more stable laser output characteristics than 7.5 meters of EDF. Secondly, the effect of coupling ratio on the output power and tuning performance of EDFRL is investigated. As it is expected, the lasing output power of proposed EDFRL is higher at 50% output coupler tap ratio than 10% output coupler tap ratio. On the other hand, the wavelength tuning range is wider when the output tap coupler ratio is 10%. As a result, the proposed loop EDFA based EDFRL structure can be used in wideband optical transmission and sensor applications due to its 70 nm wide tuning range which covers C+L band and a high output power over 0 dBm.
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A compact tunable C+L band erbium-doped fiber ring laser (EDFRL) with micro-electro-mechanical system (MEMS) based optical tunable bandpass filter was developed. The effects of erbium-doped fiber (EDF) length, output coupling ratio and pump power levels on its spectral characteristics have been analysed and optimized experimentally. With the parameters of EDF length of 6 m, output coupler ratio of 90:10 and both pump powers of 120 mW, a moderate output power level (∼+4.5 dBm) and a wide wavelength tuning range (∼80 nm) covering both C- and L- bands have been achieved.
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Fiber ring laser, tunable laser source, erbium-doped fiber.
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Gain clamping performance in an L-Band EDFA based on a lasing structure using a symmetrical narrowband FBG couple, has been analyzed experimentally. By optimizing the peak reflection wavelength of the FBG, a high clamped gain (over 27 dB) was obtained with a 0.1 dB ripple and a ∼ 25 dB dynamic range at 1585 nm.
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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 PMD based 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.
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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.
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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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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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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.
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Erbiyum katkılı fiber yükselteçler, fiber Bragg ızgara (FBG), kazanç kenetleme, kazanç spektrumu düz
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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.
