Fiber Loop Ringdown Gas Flow and Humidity Sensors

Fiber optics has been utilized in fiber optic, sensing technology, imaging optics, communications, etc. Fiber optic sensors have been developed to sense in many applications. In this thesis, fiber loop ringdown (FLRD) sensors were used to monitor two different physical sensors, such as gas flow and humidity. FLRD gas flow sensors were demonstrated. Two different sensor configurations were constructed to monitor airflow (AF). FLRD-AF sensor was based on micro-bending mechanism. The FLRD-AF sensor was able to detect AF in a range of 5 to 22.5 slpm. FLRD technique was also used to measure relative humidity (RH). A sensor was fabricated and replaced inside a chamber. The chamber provided with humidity reference and a humidity meter. The FLRD-RH was based on evanescent field mechanism. The RH and the temperature were monitored during the experiment. The FLRD-RH has a dynamic range of 4 to 100 percent

Photonic sensors based on flexible materials with FBGs for use on biomedical applications

This chapter is intended for presenting biomedical applications of FBGs embedded into flexible carriers for enhancing the sensitivity and to provide interference-free instrumentation.This work was fully supported by the Algoritmi’s Strategic Project UI 319-2011-2012, under the Portuguese Foundation for Science and Technology grant Pest C/EEI/UI0319/2011

Fibre-optic sensor technologies for humidity and moisture measurement

A review of the use of fibre-optic sensor technologies for humidity sensing is presented. The paper first provides a brief overview on the basic concept of what is meant by humidity and on conventional detection methods. This is followed by an extensive review on the various fibre-optic techniques reported for humidity sensing, covering both intrinsic and extrinsic sensor configurations

Адресный волоконно-оптический датчик для измерения относительной влажности в комплектных распределительных устройствах

A number of governing documents and by-laws of the Russian Federation, branch ministries, departments and companies have introduced the use of measuring relative air humidity, elements insulation, and SF6 into operation and maintenance process of complete switchgear. A wide range of high-precision laboratory instruments has been developed to implement these measurements. However, as a rule, these are scheduled measurements to be carried out once or twice a quarter, although the constant on-line monitoring of humidity is concerned in both the production and scientific circles of the energy industry. The possibility of on-line monitoring appeared with the advent of fiber-optic object-based passive networks for collecting information and the possibility of forming interrogation channels in them, which is provided for by the development of the Smart Grid Plus concept. Fiber optic sensors, single in their physical layer structure with passive optical networks, are highly robust and resistant to high electromagnetic fields, typical of those generated in a switchgear, and are designed to operate in harsh environments. Among their broad class, fiber optic sensors on Bragg gratings, which differ from others by direct measurement methods, have significant advantages. In particular, an increase or decrease in relative humidity will lead to a corresponding change in the wavelength of the sensing source reflected from the grating, which can be measured with an accuracy of sixth place from its absolute value.This paper proposes to consider a two-element sensor of relative humidity of a parallel structure, which differs from the existing ones by using address fiber Bragg gratings made in SMF-28 fiber. One of the gratings has a polyimide-replaced quartz shell, synthesized using a reductant fiber coating, and a completely multiplicative response to temperature and deformation caused by humidity. The second grating is recorded in a standard fiber and responds only to temperature. It is possible to include an additional third grating with a partially etched cladding, which can be used for refract metric measurements of the amount of condensed moisture on the elements of a complete switchgear. All the gratings are identical, have, as a rule, the same Bragg wavelength after manipulating their claddings, but they have differing unique addresses, which are formed by recording two transparency windows in each of the gratings with different difference frequency space. The transparency windows correspond to phase p-shifts symmetrically located at the same distance from the center of each grating. The structure obtained makes it possible to record information of the measurement conversion at the said difference frequencies in the radio range, which significantly increases the speed of relative humidity measurements and their accuracy by an order of magnitude more. In addition to what has been said, it is possible to note the capability for building a network of these sensors in series arranged in switchgear devices, with a different radiofrequency address group being used in each of them.Рядом руководящих документов и подзаконных актов Российской Федерации, отраслевых министерств, ведомств и компаний измерение относительной влажности воздуха, изоляции элементов, элегаза введено в практику процесса эксплуатации и обслуживания комплектных распределительных устройств. Разработан широкий спектр высокоточных лабораторных приборов, которые используются для реализации указанных измерений. Однако, как правило, данные измерения проводятся планово, один-два раза в квартал, хотя о постоянном онлайн мониторинге влажности речь идет как в производственных, так и научных кругах энергетической отрасли. Возможность онлайн мониторинга появилась с появлением волоконно-оптических объектовых пассивных сетей сбора информации и возможности формирования в них сенсорных каналов, что предусмотрено также развитием концепции «Smart Grid Plus». Волоконно-оптические датчики, единые по структуре физического уровня с пассивными оптическими сетями, обладают высокой помехоустойчивостью, не подвержены влиянию мощных электромагнитных полей, характерных для создаваемых в комплектных распределительных устройствах, предназначены для работы в жестких условиях эксплуатации. Среди их широкого класса существенными преимуществами обладают волоконно-оптические датчики на брэгговских решетках, которые отличаются от других прямыми методами измерений. В частности, увеличение или уменьшение относительной влажности приведет к соответствующему изменению отраженной от решетки длины волны зондирующего источника, которая может быть измерена с точностью до шестого знака от ее абсолютного значения.В данной работе предложен к рассмотрению двухсенсорный датчик относительной влажности параллельной структуры, отличающийся от существующих использованием адресных волоконных брэгговских решеток, выполненных в волокне SMF-28. Одна из решеток имеет замененную полиимидом кварцевую оболочку, синтезированную с помощью восстановителя покрытия волокна, и полный мультипликативный отклик к температуре и деформации, вызванной влажностью. Вторая – представляет собой решетку, записанную в стандартном волокне, и реагирует только на температуру. Возможно включение дополнительной третьей решетки с частично вытравленной оболочкой, которая может быть применена для рефрактометрических измерений количества конденсированной влаги на элементах комплектного распределительного устройства. Все решетки идентичны, имеют, как правило, одинаковую длину волны Брэгга, после манипуляции над их оболочками, но отличаются уникальным адресом, который формируется записью двух окон прозрачности в каждой из решеток с различным разностным частотным пространством. Окна прозрачности соответствуют фазовым p-сдвигам, симметрично расположенным на одинаковом расстоянии от центра каждой из решеток. Полученная структура позволяет регистрировать информацию измерительного преобразования на указанных адресных разностных частотах в радиодиапазоне, что существенно повышает быстродействие измерений относительной влажности и их точность еще на порядок. В дополнение к сказанному можно отметить возможность построения сети указанных датчиков в последовательно расположенных комплектных распределительных устройствах, при этом в каждом из шкафов будет использована другая радиочастотная адресная группа

Fiber bragg gratings for medical applications and future challenges: A review

In the last decades, fiber Bragg gratings (FBGs) have become increasingly attractive to medical applications due to their unique properties such as small size, biocompatibility, immunity to electromagnetic interferences, high sensitivity and multiplexing capability. FBGs have been employed in the development of surgical tools, assistive devices, wearables, and biosensors, showing great potentialities for medical uses. This paper reviews the FBG-based measuring systems, their principle of work, and their applications in medicine and healthcare. Particular attention is given to sensing solutions for biomechanics, minimally invasive surgery, physiological monitoring, and medical biosensing. Strengths, weaknesses, open challenges, and future trends are also discussed to highlight how FBGs can meet the demands of next-generation medical devices and healthcare system

Fiber Bragg Gratings for Medical Applications and Future Challenges: A Review

[EN] In the last decades, fiber Bragg gratings (FBGs) have become increasingly attractive to medical applications due to their unique properties such as small size, biocompatibility, immunity to electromagnetic interferences, high sensitivity and multiplexing capability. FBGs have been employed in the development of surgical tools, assistive devices, wearables, and biosensors, showing great potentialities for medical uses. This paper reviews the FBG-based measuring systems, their principle of work, and their applications in medicine and healthcare. Particular attention is given to sensing solutions for biomechanics, minimally invasive surgery, physiological monitoring, and medical biosensing. Strengths, weaknesses, open challenges, and future trends are also discussed to highlight how FBGs can meet the demands of next-generation medical devices and healthcare system.This work was supported in part by INAIL (the Italian National Institute for Insurance against Accident at Work), through the BRIC (Bando ricerche in collaborazione) 2018 SENSE-RISC (Sviluppo di abiti intelligENti Sensorizzati per prevenzione e mitigazione di Rischi per la SiCurezza dei lavoratori) Project under Grant ID10/2018, in part by the UCBM (Universita Campus Bio-Medico di Roma) under the University Strategic HOPE (HOspital to the PatiEnt) Project, in part by the EU Framework Program H2020-FETPROACT-2018-01 NeuHeart Project under Grant GA 824071, by FCT/MEC (Fundacao para a Ciencia e Tecnologia) under the Projects UIDB/50008/2020 - UIDP/50008/2020, and by REACT (Development of optical fiber solutions for Rehabilitation and e-Health applications) FCT-IT-LA scientific action.Lo Presti, D.; Massaroni, C.; Leitao, CSJ.; Domingues, MDF.; Sypabekova, M.; Barrera, D.; Floris, I.... (2020). Fiber Bragg Gratings for Medical Applications and Future Challenges: A Review. IEEE Access. 8:156863-156888. https://doi.org/10.1109/ACCESS.2020.3019138S156863156888

Optical fibre Sensor for Simultaneous Temperature and Relative Humidity Measurement: Towards Absolute Humidity Evaluation

Temperature and humidity are essential parameters in monitoring the health of patients in critical care. An optical fibre sensor has been developed for simultaneous measurement of relative humidity (RH) and temperature at a single optical fibre tip based on the reflected intensity. Combining these measurements enables absolute humidity values to be obtained. The fibre tip is first modified with a coating of poly(allylamine hydrochloride) (PAH) / silica nanoparticles (SiO2 NPs) for relative humidity (RH) measurement and then coated with thermochromic liquid crystal (TLC) for temperature measurement. Experimental results demonstrate that the RH and temperature sensitivity are respectively 0.43%/RH% (intensity at a wavelength of 650nm) from 55 - 90% RH (R2=0.973) and 3.97 nm/°C from 28 – 46 °C (R2>0.99). Moreover, the proposed sensor has low crosstalk between each of the sensing parameters, with a response time of 3.1s temperature (30 – 38 °C) and 13.2s for relative humidity (20 – 80 %). In comparison to grating based optical fibre sensors the proposed sensor is low-cost with a simple manufacturing process which has the potential to find widespread use in healthcare applications

Development of Novel Fiber Optic Humidity Sensors and Their Derived Applications

The main focus of this thesis is on the design and development of novel fiber optic devices for relative humidity (RH) sensing with emphasis on high sensitivity, a wide humidity range, low temperature dependence, fast response time and good stability.Novel RH sensors based on fiber bends are fabricated by coating the surface of the buffer stripped bent fiber with selected hygroscopic materials such as Polyethylene oxide or Agarose. It is shown that the Polyethylene oxide coated device has a high sensitivity in a narrow RH range while the Agarose coated fiber bend shows a linear RH sensitivity in a wide RH range. Both of these sensors demonstrate a fast response (in the order of milliseconds) to RH variations. The limitations of fiber bend based humidity sensors are also discussed in the thesis. A novel RH sensor based on a reflection type photonic crystal fiber interferometer (PCFI) is presented which does not rely on the use of any hygroscopic material. The operating principle of a PCFI sensor based on the adsorption and desorption of water vapour at the silica-air interface within the PCF capillaries is discussed. The demonstrated sensor shows a good RH sensitivity in the higher RH range. Furthermore this RH sensor is almost temperature independent and can also be used in a high temperature and high pressure environment for humidity sensing.In order to improve the sensitivity of a reflection type PCFI over a wider RH range an alternative sensor is developed by infiltrating the microholes of the PCF with the hygroscopic material Agarose. The demonstrated novel sensor has a good sensitivity, a fast response time and a compact size. The temperature dependence of the device is also investigated. A novel hybrid device based on Agarose infiltrated PCFI interacting with a fiber Bragg grating is also presented which can simultaneously measure RH and temperature.A novel RH sensor based on a transmission type photonic crystal fiber interferometer coated with Agarose is also presented and discussed. This structure is used to study the effect of Agarose coating thickness in such a sensor on the RH sensitivity. It is demonstrated that the RH sensitivity of the sensor has a significant dependence on the thickness of the coating. An experimental method is also demonstrated to select an optimum coating thickness to achieve the highest sensitivity for a given RH sensing range. The sensor with the highest demonstrated sensitivity shows a linear response in the RH ranges of 40-80 % and 80-95 % with a sensitivity of 0.57 nm/%RH and 1.43 nm/%RH respectively.Finally, a comparison of the four RH sensing devices is presented, based on their size, operating range, RH sensitivity, temperature dependence and response time, in the context of selecting suitable devices for end-user applications. Two examples of applications are presented: dew sensing and breathing monitoring. The reflection type PCFI which does not use any hygroscopic material is selected for dew sensing and the dew response of the device is presented and discussed. Finally a novel breathing sensor based on the Agarose infiltrated PCFI is developed, which due to its immunity to interference from electric and magnetic fields, is suitable for breath monitoring of patients during medical procedures such as a magnetic resonance imaging scan

SnO2-MOF-Fabry-Perot optical sensor for relative humidity measurements

In this paper, a new optical fiber sensor for relative humidity measurements is presented and characterized. The sensor is based on a SnO2 sputtering deposition on a microstructured optical fiber (MOF) low-finesse Fabry-Pérot (FP) sensing head. The feasibility of the device as a breathing sensor is also experimentally demonstrated. The interrogation of the sensing head is carried out by monitoring the Fast Fourier Transform phase variations of the FP interference frequency. This method substitutes the necessity of tracking the optical spectrum peaks or valleys, which can be a handicap when noise or multiple contributions are present: therefore, it is low-sensitive to noise and to artifacts signal amplitude. The sensor shows a linear behavior in a wide relative humidity range (20%–90% relative humidity) in which the sensitivity is 0.14 rad/%; the maximum observed instability is 0.007 rad, whereas the highest hysteresis is 5% RH. The cross correlation with temperature is also considered and a method to lower its influence is proposed. For human breathing measurement, the registered rising and recovery times are 370 ms and 380 ms respectively.The authors are grateful to A. Ortigosa, D. Erro, Dr. M. Bravo and Dr. R.A. Perez-Herrera. We also thank the Spanish Government projects TEC2013-47264-C2-2-R, TEC 2016-76021-C2-1-R, TEC2016-78047-R, TEC2016-79367-C2-2-R, Innocampus and the Cost Action MP 1401, as well as to the AEI/FEDER Funds

Recent advances in biomedical photonic sensors: a focus on optical-fibre-based sensing

In this invited review, we provide an overview of the recent advances in biomedical pho tonic sensors within the last five years. This review is focused on works using optical-fibre technology, employing diverse optical fibres, sensing techniques, and configurations applied in several medical fields. We identified technical innovations and advancements with increased implementations of optical-fibre sensors, multiparameter sensors, and control systems in real applications. Examples of outstanding optical-fibre sensor performances for physical and biochemical parameters are covered, including diverse sensing strategies and fibre-optical probes for integration into medical instruments such as catheters, needles, or endoscopes.This work was supported by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (PID2019-107270RB-C21/AEI/10.13039/501100011033), and TeDFeS Project (RTC-2017- 6321-1) co-funded by European FEDER funds. M.O. and J.F.A. received funding from Ministerio de Ciencia, Innovación y Universidades of Spain under Juan de la Cierva-Formación and Juan de la Cierva-Incorporación grants, respectively. P.R-V. received funding from Ministerio de Educación, Cultura y Deporte of Spain under PhD grant FPU2018/02797