In this work, we propose an optical fiber sensor based on a silica capillary section spliced between two sections of single mode fiber. One of the fusion splices is done with a transversal offset, to enable the creation of a Mach-Zehnder interferometer (MZI). Furthermore, the structure, monitored in transmission, also exhibits anti-resonant behavior. This effect is inhibited by submerging the sensor in liquid media, and the MZI becomes dominant. The sensor with a length of 3.75 mm presented a linear response to temperature with a sensitivity of 26.0 pm/°C. Combining this sensor with another with a length of 3.82 mm, in a parallel configuration where both sensors are placed under water, an interferometric pattern with a higher frequency modulated by a lower one is attained, which is produced by the Vernier effect. The sensor, although insensitive to refractive index variations, showed a maximum temperature sensitivity of 2.193 nm/°C, showcasing a magnification factor of 84.3. This sensor may find applications in different fields where an accurate measurement of temperature in liquid media is required, such as chemistry, pharmaceutical, and biological applications.
The early detection of different diseases is crucial for their successful treatment. Existing literature has established distinct volatile organic compound (VOC) profiles in organic samples that are associated with different disease conditions. These identified profiles hold significant potential for the development of rapid, non-invasive, and cost-effective disease screening tools, meeting the essential criteria for effective diagnostic measures.
2-propanol is a secondary alcohol that exhibits different associations with a variety of diseases across diverse organic samples. Notably, elevated levels of 2-propanol in urine samples have been linked to type II diabetes, whereas a decrease in its concentration is observed in cases of malignant biliary strictures. In feces, an increase in 2-propanol is associated with colorectal cancer. Furthermore, disturbances in 2-propanol levels in breath have been correlated with various types of cancers. These findings underscore the potential utility of 2-propanol as a biomarker for disease detection across multiple biological matrices.
In this study, we propose a sensor that combines a multimode interference structure with a molecularly imprinted polymer (MIP) functionalization. The multimode sensor is created by fusion splicing a coreless fiber section to a single-mode fiber (SMF). For coating the coreless fiber (CSF), the dip coating technique was utilized, employing a MIP with 2-propanol as the template, and separately, the corresponding non-imprinted polymer (NIP). Our findings reveal that the MIP demonstrates specificity for 2-propanol in the gas phase, showing a sensitivity of 13 pm/wt.% 2-propanol. In contrast, the corresponding NIP lacks sensitivity to 2-propanol. This outcome emphasizes the potential of our proposed sensor design for the selective detection of 2-propanol, thereby highlighting its applicability in gas phase analyses.
A growing human population and changing climatic conditions have made food safety a pressing issue to our society. While conventional methods for their analysis are accurate, sensitive, and selective, they are costly, time-consuming and require skilled technicians. Optical fibre sensors have emerged as a versatile alternative for the detection of these compounds with advantages over traditional methods. In this work, we propose a high-sensitivity multimode fibre sensor for RI measurement. Our sensor consists of a section of capillary tube spliced between two sections of SMF and was characterised in regard to its response to variations in RI in a range between 1.3329 and 1.3459 RIU. The resulting spectrum presented several frequencies and the measurements performed at 1558 nm provided a sensitivity of 423.6 nm/RIU, with a resolution of 9.71 x 10‑5 RIU. Further analysis of the spectrum using a low pass filter with a cutoff frequency of 0.06 nm-1 provided a maximum sensitivity of 1459.4 nm/RIU, with a resolution of 3.33 x 10-4 RIU.
Volatile organic compounds (VOCs) show great potential as biomarkers in non-invasive disease detection. We propose a cascaded Fabry-Perot (FP) fiber sensor for characterizing ethanol and 2-propanol. The sensor fabrication involves splicing a single mode fiber to a silica capillary (SC), followed by cleaving the SC. The SC tip is immersed in a PMMA solution and heated for rapid solvent evaporation, forming a dual cavity. The sensor was tested in the gas phase, using binary hydroalcoholic mixtures containing ethanol and 2-propanol. The response attained was nonlinear, with a maximum sensitivity of -133.7 pm/vol.% and -173.0 pm/vol.% for 2-propanol and the ethanol, respectively, in a range between 35-50 vol.%.
In this study, a tailored hybrid sensing configuration integrating fiber Bragg grating and intrinsic Fabry-Perot interferometer is presented. It enables simultaneous discrimination and tracking of internal temperature and pressure changes within 18650 Li-ion batteries (LiBs). The battery undergoes rigorous cycling tests at different operating conditions and a comparison between them is presented. The optical fiber sensors instrumented into the LiB reveal, throughout overall cycling tests, a compelling correlation between internal and external temperature behavior. The application of systematic Incremental Capacity Analysis derivative curves during battery operation exposes crucial insights into the relationship between pressure and temperature physical parameters, and their electrochemical behavior. This optical sensing approach contributes in this way to a nuanced understanding of internal LiB dynamics, with implications for their optimizing performance and safety in diverse applications.
A Fabry Perot (FP) based fiber sensor for multiparameter measurement is proposed. The sensor is constituted by a short section of a hollow square core fiber (HSCF) spliced between a single mode fiber and a long section of a silica capillary tube. In a reflection scheme, several FP cavities are enhanced in different areas of the HSCF. In a single 439 μm long sensing head, three FP cavities are excited. Using the Fourier band-pass filter method, each cavity was individually monitored towards variations of pressure, temperature, and curvature. The maximum sensitivities of (3.23 ± 0.04) nm/MPa, (9.6 ± 0.3) pm/°C, and (-32 ± 1) pm/m-1 were obtained for pressure, temperature, and curvature, respectively within a measurement range of 0.4 MPa, 110°C, and 9 m-1. The distinct responses of the FP cavities to the measurands allow for a triple-hybrid application of the sensor towards simultaneous measurement of pressure, temperature, and curvature. The proposed sensor is robust with simple fabrication and small dimensions, revealing promising to be employed in a wide range of applications where the measurement of several physical parameters is required.
In this work, an inline sensor based on a double antiresonant hollow core fiber is proposed for the simultaneous measurement of refractive index and temperature. The fiber, consisting of four silica capillaries with wall thickness of ~1.5 μm and a cladding with a thickness of ~36.5 μm, is spliced between two sections of single mode fiber. The spectral behavior, measured in transmission, results from the combination of different frequencies which enable the discrimination between the two parameters. The sensing head is subjected to refractive index measurements using aqueous solutions with different concentrations of ethanol. For a sensor with a length of ~10 mm, and considering the lower frequency signal, the sensitivity to refractive index is 389.6 nm/RIU, whereas for the higher frequency, the sensitivity attained is 2.8 nm/RIU. On the other hand, the sensing head presented a sensitivity to temperature of 25.5 pm/K and -27.6 pm/K for the higher and lower frequencies, respectively.
A reflective fiber optic sensor based on multimode interference for the measurement of relative humidity (RH) is proposed and experimentally demonstrated. The proposed probe is fabricated by fusion-splicing, approximately 30 mm long coreless fiber section to a single mode fiber. A hydrophilic agarose gel is coated on the coreless fiber, using the dip coating technique. When the incident light comes from the SMF to the CSF, the high-order modes are excited and propagate within the CSF. These excited modes interfere with one another as they propagate along whole CSF length, giving rise to a multimode interference (MMI). Since the effective refractive index of the agarose gel changes with the ambient relative humidity, as the environmental refractive index changes, the propagation constants for each guided mode within the CSF will change too, which leads to shifts in the output spectra. The proposed sensor has a great potential in real time RH monitoring, exhibiting a large range of operation with good stability. For RH variations in the range between 60 %RH and 98.5 %RH, the sensor presents a maximum sensitivity of 44.2 pm/%RH, and taking in consideration the interrogation system, a resolution of 1.1% RH is acquired. This sensor can be of interest for applications where a control of high levels of relative humidity is required.
A hybrid sensor based on microstructured hollow core fiber is proposed for the simultaneous measurement of strain and temperature. The fiber, consisting of four silica capillaries with wall thickness of ~1 μm and a cladding with a thickness of ~26 μm, is spliced between two sections of single mode fiber. Using a low arc discharge power to splice the two fibers, a Fabry-Perot interferometer is formed. In this situation, light travels in the hollow core and the behavior of a twowave interferometer is observed. However, when the power of the arc discharge is increased, the structure near the splice area changes, generating new interferometric paths and giving rise to a different spectral response. In this work, sensors with a single degenerated area are analyzed. In such case, both Fabry-Perot and Michelson interferometers are created and different sensitivities to strain and temperature are obtained. The different spectral frequencies are analyzed, enabling the discrimination between the two parameters. For a sensor with a length of ~385 μm, strain sensitivities of 2.46 pm/με and -0.52 pm/με are obtained for the Fabry-Perot and for the Michelson interferometer, respectively. Regarding temperature, a sensitivity of 1.81 pm/°C was attained for the former, whereas for the last the sensitivity was of 42.23 pm/°C. Keywords: Hyb
There is a set of important selection criteria in the design of fiber optic sensors that determine the compromise between design complexity and performance. Optical fiber sensors not only withstand high temperatures, but they can also operate in different chemical and aqueous media allowing measurements in areas not otherwise accessible. A Fabry-Perot cavity based on an air bubble created in a multimode fiber section is proposed. The air bubble is formed using only cleaving and fusion splicing techniques. The parameters used to produce the microcavities were found empirically. Two different configurations are explored: an inline cavity formed between two sections of MMF, and a fiber tip sensor. In the last, after the air bubble is created, a cleave is made near the cavity, after which the sensor is subjected to several electrical arcs to reshape the cavity and obtain a thin diaphragm. The inline sensor, with a length of ~297 μm, was used to measure strain and presented a sensitivity of 6.48 pm/με. Regarding the fiber tip sensor, it was subjected to glycerin/water mixture variations, by immerging the sensing head in several solutions with different concentrations of water in glycerin. In this case, the sensor had a length of ~167 μm and a diaphragm thickness of ~20 μm. As expected, with the increase of the external medium refractive index, the sensor visibility decreased. Furthermore, a wavelength shift towards red was observed, with a sensitivity of 7.81 pm/%wt. Both devices exhibited low dependence to temperature (<1.8 pm/°C).
In this work, an optical fiber sensing network has been developed to assess the impact of different environmental conditions on lithium batteries performance through the real time thermal monitoring. The battery is submitted to constant current charge and different discharge C-rates, under normal and abusive operating conditions. The results show that for the discharge C-rate of 5.77C, the LiB under cold and dry climates had 32.5% and 27.2% lower temperature variations, when compared with temperate climates, respectively. The higher temperature shift detected in the temperate climate was related to the battery better performance regarding discharge capacity and power capabilities.
A Fabry-Perot interferometer based on an array of soda-lime glass microspheres is proposed for temperature sensing. The microspheres are introduced in a hollow-core silica tube using a tapered fiber tip. After the insertion of each microsphere the sensor is subjected to temperature measurements. The sensor exhibits non-linear behavior and a dependence on the number of microspheres is observed. A maximum sensitivity of 11.13 pm/°C is achieved, when there is only one microsphere inside the capillary structure.
A Fabry-Perot air bubble microcavity fabricated between a section of single mode fiber and a multimode fiber is proposed. The study of the microcavities growth with the number of applied arcs is performed. The sensors are tested for lateral load and strain, where sensitivities of 0.32 nm/N and 2.11 nm/N and of 4.49 pm/με and 9.12 pm/με are obtained for the 47 μm and 161 μm long cavities, respectively. The way of manufacturing using a standard fusion splicer and given that no oils or etching solutions are involved, emerges as an alternative to the previously developed air bubble based sensors.
A curvature sensor based on a Fabry-Perot interferometer is proposed. A capillary tube of silica is fusion spliced
between two single mode fibers, producing a Fabry-Perot cavity. The light propagates in air, when passing through
the capillary tube. Two different cavities are subjected to curvature and temperature. The cavity with shorter length
shows insensitivity to both measurands. The larger cavity shows two operating regions for curvature measurement,
where a linear response is shown, with a maximum sensitivity of 18.77pm/m-1 for the high curvature radius range.
When subjected to temperature, the sensing head produces a similar response for different curvature radius, with a
sensitivity of 0.87pm/°C.
In this work, a Fabry-Perot optical fiber sensor for the measurement of strain at extreme temperatures is proposed. The cavity is formed by splicing a short section of a silica tube between two sections of single mode fiber. The tube, with a cladding ~14 μm thick and a hollow core, presents four small rods, of ~20 μm in diameter each, positioned in in diametrically opposite positions. This design ensures higher mechanical stability of the tube. Strain measurements are performed over a wide range of temperatures, until 900 °C. Some of the annealing effects are addressed in this study.
In this work a novel optical fiber sensor based on silica microspheres array is proposed. Different sensing heads are presented and compared, differing on the number of microspheres. These structures, ranging from arrays of one to five, are spliced in series. The sensor is subjected to different physical parameters, such as strain, temperature, refractive index and bending. Depending on the number of microspheres the sensitivities to strain and bending are different. The sensor also presents a high sensitivity to temperature of 20.3 pm/°C.
In this paper it is proposed an interrogation system based on OTDR for fiber loop mirror intensity sensors. The system has been characterized in order to obtain its maximum dynamic range. The technique demonstrated good linearity with a – 13.3 dB/mm slope. A 0.027 mm resolution was achieved. The proposed interrogation system permits multiplexing of around 10 sensors and showed to be an alternative technique for multiplexing and remote sensing.
A torsion active sensor based on a figure-of-eight configuration is presented. The interferometric fiber loop mirror, composed by a section of photonic crystal fiber, also acts as a sensing element. When torsion is applied over a range of 180°, a sensitivity of 7.13 pm/degree is achieved. Besides, this configuration can also be used to measure optical power variations and it presents low sensitivity to temperature.
A Fabry-Pérot microcavity tip temperature sensor based on a special design double-cladding optical fiber is proposed. The produced fiber has pure silica core and outer cladding and a silica ring doped with phosphorous. The whole ring region is removed by chemical etching post-processing. Consequently, light will be guided in the core region. In a first step, the double-cladding optical fiber is spliced to single mode fiber. Afterwards, the tip is etched in a solution of 48% hydrofluoric acid. The inner cladding will be etched faster, and the core becomes suspended and surrounded by air. The Fabry-Pérot microcavity tip sensor is subjected to temperature, and a linear sensitivity of 14.6 pm/°C is obtained.
In this work, a simple real-static nanostrain sensor based on a Bragg grating structure is presented. The setup is
constituted by a narrow linewidth laser as light source, an optical circulator and a photodetector. The sensing head is
formed by a chirped Bragg grating inscribed in a standard single mode fiber (SMF-28) by the phase technique. The fiber
face end is cleaved and coated with a silver mirror, obtaining a Fabry-Perot interferometer. It is observable that the
fringes period increases along the grating, due to the chirp spectrum (0.4 nm/cm) characteristics. The laser is fixed in one
slope region of the fringe pattern. When strain is applied, the optical power changes linearly. A sensitivity of 5.72 μW/με
in a range of 2 με . The sensing head resolution is 70 nε for a measurement step of 875 nε.
In this work, a high-birefringent Sagnac loop interferometer torsion sensor is presented. The sensing head is
inserted between the output ports of a high-birefringent coupler and it is formed by a section of standard
single mode fiber. The sensing head characterization is done for torsion, temperature and strain
measurements. The spectral response of this sensing head presents two interferometers, which are dependent
on the light polarization states. Interference occurs due to the different lengths of the coupler output arms.
This configuration allows the exclusion of a polarization controller, since it is possible to manipulate directly
the polarization of light that travels inside the coupler. When the sensing head is subjected to torsion, it is
possible to observe a beat between the two interferometers. In this case, there is a simultaneous π/4 excitation
of the two polarization states in the splices region. The torsion sensitivity is related to the sensing head length.
The sensor response is periodic and the twist range can be from -2π to 2π. The sensor is unaffected by
temperature and strain variations. This configuration is simple and when compared to the conventional
configuration, the polarization controller is suppressed. The setup can be used in specific applications, such as
in mechanical engineering.
A highly-birefringent photonic bandgap Bragg fiber loop mirror sensor is proposed. Thanks to the Bragg
fiber geometry, one can observe the group birefringence and the bandgap fiber in the transfer function.
The sensing head presented different sensitivities for strain and temperature measurements. Using the
matrix method, both the physical parameters can be discriminated. It is important to highlight that this
Bragg fiber presents sensitivity to temperature of ~5.75 nm/ºC, for the group birefringence measurand.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.