•Principles and structures were introduced and discussed;•Advantages and disadvantages of different sensors were compared and analyzed;•Future development of HCF gas sensors was prospected.
Gas ...sensors play an important role in the increasing trend of industrial automation in recent years. Hollow core microstructured optical fibers have become a popular material for gas sensors because of their unique structure and excellent performance. In this paper, the hollow-core microstructured optical fiber gas sensors are divided into two types (interferometric type and absorptive type) according to the sensing principle. The corresponding principles and structures are introduced and discussed respectively. We focus on the research progress and key performance of hollow core microstructured optical fiber based gas sensors reported in the past 10 years to compare and discuss their advantages and disadvantages, as well as their future development prospects.
Mode division multiplexing (MDM) systems using orbital angular momentum (OAM) modes can recover the data in D different modes without recourse to full (2D × 2D) multiple input multiple output (MIMO) ...processing. One of the biggest challenges in OAM-MDM systems is the mode instability following fiber propagation. Previously, MIMO-free OAM-MDM data transmission with two modes over 1.1 km of vortex fiber was demonstrated, where optical polarization demultiplexing was employed in the setup. We demonstrate MDM data transmission using two OAM modes over 1.4 km of a specially designed ring core fiber without using full MIMO processing or optical polarization demultiplexing. We demonstrate reception with electrical polarization demultiplexing, i.e., minimal 2 × 2 MIMO, showing the compatibility of OAM-MDM with current polarization demultiplexing receivers.
The direct exposure of volatile organic compounds (VOCs) is widely related to several adverse health effects. Therefore, an accurate amount of its usage is necessary required depending on the ...threshold limit. There have been a variety of sensors developed to measure an amount of VOC for safety use. Optical fiber-based VOC sensors offer huge advancements in technologies to overcome several limitations from the convectional VOC sensors that appeared over the past decade. Real-time monitoring and detection of VOCs are important to maintain a safe and healthy domestic/industrial environment. The optical fibers are highly-sensitive and widely applied to several ranges of parameters including gas sensing, and have also been used to monitor VOCs at the sub-ppm range. Recognizing the major developments in the field of the optical fiber, this article aims to review the recent progress in VOC monitoring, resulting in a wide range of sensing configurations are being discussed. Additionally, the article highlights the advantages, limitations, and future possibilities in this area.
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We report a novel fiber-optic hybrid-structured Fabry-Perot interferometer (HSFPI) based on large lateral offset splicing for simultaneous measurement of strain and temperature with advantages of ...high sensitivity, low cost, and easy fabrication. The high-strain sensitivity of 28.95 pm/με and low-temperature sensitivity of 0.54 pm/°C are obtained for air cavity, and strain sensitivity of 28.95 pm/με is over five times compared to the current HSFPI (5.18 pm/με). In addition, strain and temperature sensitivities of silica cavity are, respectively, 1.59 pm/με and 12.71 pm/°C. Thus, due to the different sensitivities of air cavity and silica cavity to strain and temperature, this structure can be used to concurrently measure strain and temperature.
A review of the current status of humidity sensors based on optical fiber gratings (OFGs) is presented. Humidity monitoring and its control are gaining importance in several fields including ...industrial processes and health. This review aims at giving an overview of the major developments over the last decades and categorizing the recent progress in humidity sensors based on the OFGs functionalization. This review describes the measurement principle of these sensors, their metrological properties, the materials used to functionalize OFGs, and the factors which influence the sensors' response.
An optical fiber humidity sensor based on filmy black phosphorus quantum dots- polyvinyl alcohol (BPQDs-PVA) gel sandwiched between two sections of single-mode fibers (SMFs) is proposed. The ...BPQDs-PVA compound serves as Fabry-Perot (FP) cavity that directly perceives external humidity variations and modulates the reflection spectrum. Based on the excellent hygroscopicity of BPQDs-PVA compound, the humidity sensor achieved a humidity sensitivity of 0.2259 nm/%RH in the range of 42-57 %RH, and an ultra-high humidity sensitivity of 12.4307 nm/%RH in the range of 57-60 %RH. The maximum instability of the sensor is 0.02 %RH, and the response/recovery time are 0.78s/1.24s, respectively. Easy fabrication process, low cost, good stability and high sensitivity make it has great potential in fields which need accurate humidity monitor and control.
We propose a novel polymer optical fiber (POF) sensing system based on fiber Bragg gratings (FBGs) to measure foot plantar pressure. The plantar pressure signals are detected by five FBGs, in the ...same piece of cyclic transparent optical polymer (CYTOP) fiber, which are embedded in a cork insole for the dynamic monitoring of gait. The calibration and measurements performed with the suggested system are presented, and the results obtained demonstrate the accuracy and reliability of the sensing platform to monitor the foot plantar pressure distribution during gait motion and the application of pressure. This architecture does not compromise the patient's mobility nor interfere in their daily activities. The results using the CYTOP fiber showed a very good response when compared with solutions using silica optical fibers, resulting in a sensitivity almost twice as high, with excellent repeatability and ease of handling. The advantages of POF (e.g., high flexibility and robustness) proved that this is a viable solution for this type of application, since POF's high fracture toughness enables its application in monitoring patients with higher body mass compared with similar systems based on silica fiber. This study has demonstrated the viability of the proposed system based on POF technology as a useful alternative for plantar pressure detection systems.
We present baria-silica erbium-doped fibers (Ba-EDF) for extending the bandwidth of L-band EDFAs beyond 1620 nm. Using a combination of modified chemical vapor deposition (MCVD) process and ...solution-doping technique, we demonstrate low loss (<10 dB/km at 1200 nm) fiber cores with BaO concentration of 1-3 mol% and Er 3+ concentration of 8×10 24 m -3 . We show that the optical properties and EDFA performance are positively affected by increasing the BaO content. Namely, when we increase the BaO concentration from 1.3 to 3 mol%, we observe a reduction of pair-induced quenching that correlates with a bi-exponential luminescence decay with a dominant 15.5 ms lifetime component. Furthermore, the slight modifications of absorption/ emission coefficients point to a red-shift of the signal excited state absorption and consequently, to a moderate extension of the L-band gain to longer wavelengths (1622 nm).
A two-dimensional (2D) vector vibration sensor is designed and fabricated by using an optical fiber double-clamped beam with four-core fiber Bragg gratings and a mass block which is glued in the ...middle of fiber. Vectorial acceleration perpendicular to the fiber can be measured using two mutually orthogonal FBG-pairs in the four-core fiber to obtain the 2D vibrating information. The experimental results show that the sensor possesses a 2D vectorial acceleration sensitivity of 345 pm/g in the flat response region of 5-30 Hz, and it is temperature insensitive, compact, and cascadable. Both resonance frequency and sensitivity can be improved by optimizing the length and weight of the free-fiber. The proposed sensor has the potential applications for dynamic monitoring in oil exploration, seismic exploration, heart rate monitoring.
Many interesting phenomena in twisted fiber have been reported. In this letter, the twisted single-mode fiber (TSMF) was proposed and studied. It was fabricated by CO2 splicer. Experiments and robust ...cladding modes resonant theoretical model demonstrated it has transmission dips of long-period gratings. Besides, the light in core will scatter into cladding due to disturbance in core. It will cause multimode interference. A tangential direction theoretical model was put forward to test the experiment characteristic, and was in good agreement with experiment results. In addition, some performance of physical parameters, such as temperature and bending loss response of TSMF are also analyzed. The results indicate that TSMF is a good candidate in sensing and the telecommunication fields.
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