D-shaped Single Mode Fibers Research Articles

Nano-Photonic Crystal D-Shaped Fiber Devices for Label-Free Biosensing at the Attomolar Limit of Detection.

Maintaining both high sensitivity and large figure of merit (FoM) is crucial in regard to the performance of optical devices, particularly when they are intended for use as biosensors with extremely low limit of detection (LoD). Here, a stack of nano-assembled layers in the form of 1D photonic crystal, deposited on D-shaped single-mode fibers, is created to meet these criteria, resulting in the generation of Bloch surface wave resonances. The increase in the contrast between high and low refractive index (RI) nano-layers, along with the reduction of losses, enables not only to achieve high sensitivity, but also a narrowed resonance bandwidth, leading to a significant enhancement in the FoM. Preliminary testing for bulk RI sensitivity is carried out, and the effect of an additional nano-layer that mimics a biological layer where binding interactions occur is also considered. Finally, the biosensing capability is assessed by detecting immunoglobulin G in serum at very low concentrations, and a record LoD of 70 aM is achieved. An optical fiber biosensor that is capable of attaining extraordinarily low LoD in the attomolar range is not only a remarkable technical outcome, but can also be envisaged as a powerful tool for early diagnosis of diseases.

Design a D-shaped single mode fiber SPR sensor with a composite nanostructure of HMM/monolayer graphene for DNA hybridization detection

The detection of DNA sequence hybridization has taken on a critical importance for the research of life science, microbiology, and environmental science. In this paper, a D-shaped single mode fiber (SMF) SPR sensor with a composite nanostructure of hyperbolic metamaterials (HMM)/monolayer graphene was developed for DNA detection. The dispersion relation of the Bloch wave in HMM and the energy conversion between modes in plasma resonance were confirmed through calculation and simulation. During the experiment, the metamaterial combined with a monolayer graphene composite structure exhibited the sensitivity and quality factor of 5000 nm/RIU and 40 RIU−1, respectively. The sensor based on the optimal parameters was adopted to detect the hybridization of DNA molecules, and the affinity and reaction rates of DNA molecular hybridization were analyzed based on molecular reaction kinetics. As revealed by the results of this study, the sensor had the advantages of miniaturization, low cost, and specificity detection, which could serve as a novel sensor for DNA hybridization detection from visible light to near infrared region.

Low-cost wearable device based D-shaped single mode fiber curvature sensor for vital signs monitoring

A low-cost wearable pulse and respiratory monitoring system based on D-shaped single mode fiber (SMF) curvature sensor is proposed and investigated. The curvature sensing performance of D-shaped SMFs with different transmission loss are tested and analyzed, and the sensitivity up to − 7.208%/m−1. The D-shaped optical fiber structure is encapsulated by polydimethylsiloxane (PDMS) and implanted in a wrist strap, which realizes good wearability and comfort in the process of human pulse monitoring. The system adopts laser source module and signal acquisition module for integrated and miniaturized design, and real time signal acquisition using Field-Programmable Gate Array (FPGA). The real-time monitoring of pulse signal intensity and frequency before and after exercise was realized. The results show that pulse intensity increased after exercise, with a 10%− 30% increase in pulse frequency, which is consistent with the results in medical theory. In addition, the D-shaped SMF encapsulated by PDMS also was implanted into the belt, which also successfully applied to the monitoring of respiratory signals under quiet and walking conditions.

Graphene/PVA coated D-shaped fiber for sodium nitrate sensing

A graphene/Polyvinyl alcohol (PVA) coated D-shaped fiber structure for sensing sodium nitrate solutions is proposed in this paper. D-shaped single mode fiber (SMF) coated with graphene/PVA was used as a sensor for sodium nitrate liquid solutions with the concentration range of 1–7%. After monitoring the output power and spectral transmission characteristics of the sensor, the graphene/PVA coated sensor showed an improved performance over the uncoated structure. The evanescent mode of the side-polished fiber and the interaction between the nitrate ions and the coating graphene improved the sensor’s performance. The graphene/PVA coated sensor had sensitivity and linearity of 0.390 dBm/% and 99% compared to the uncoated sensor sensitivity and linearity of 0.117 dBm/% and 98% respectively. This shows the advantage of using D-shaped fiber coated with graphene and PVA to detect sodium nitrate concentrations.

Metal-organic framework functionalized polymer coating for fiber optical methane sensors

Functional polymer coating integrated with optical fiber is an intriguing approach to develop low-cost point and distributed fiber sensors for large-scale applications. This paper presents the development of gas-sensitive coatings for both single-mode and multi-mode optical fibers through the application of polymer/nanocrystalline metal-organic frameworks (MOFs) composites as methane sensors for monitoring natural gas infrastructure. Silicone polymers based on PDMS with optimized optical and mechanical properties were developed as host materials for the well-known metal organic framework ZIF-8. Integration of ZIF-8 nanocrystals within the PDMS polymer modified the physical properties of the material and led to an enhancement of the CH4 solubility and permeability of the resulting film. The refractive indices, viscosities, and mechanical properties of the ZIF-8 functionalized polymers were optimized by adjusting the ZIF-8/polymer weight ratio and subsequently used as the fiber coating. Both multi-mode and single-mode optical fibers coated with the MOF-functionalized polymers showed scaled changes in transmitted power upon exposure to various concentration of CH4 in a N2 carrier gas. The variations in transmitted power through the fiber were the result of changes in evanescent wave interactions with the sensor coating due to shifts in the polymer cladding refractive index upon CH4 sorption. A methane detection limit of 1 % in nitrogen was achieved using both multimode fiber and D-shaped single mode fibers. Overall, our paper presents a low-cost approach to perform point and distributed sensing for CH4 through an innovative method of functional polymer material integration on optical fiber sensor platforms.

Gold grating assisted SPR based D-shaped single mode fiber for detection of liquid refractive index

In this paper, a surface plasmon resonance based D-shaped single mode fiber sensor with a gold grating over the polished fiber surface, is analyzed by finite element method for refractive index sensing. Benefitted from the localized surface plasmon resonance effect of gold grating, the proposed sensor achieves a reasonably good wavelength sensitivity of 7590 nm/RIU for the refractive index range varying from 1.34 to 1.38 and the corresponding resolution is 1.31 × 10−5 RIU. Furthermore, the maximum amplitude sensitivity of the sensor is calculated to be 676.08 RIU−1. The good sensing performance, low cost and simple structure makes this sensor a potential candidate for application in the areas of food processing, environmental monitoring and biochemical analysis.

Study on polarization properties of graphene coated D-shaped fiber**Project supported by the National Natural Science Foundation of China (Grant Nos. 61575170, 61575168, and 61475133), the Basic Research Project of Hebei Province, China (Grant No. 16961701D), the Natural Science Foundation of Hebei Province, China (Grant No. F2016203392), the Provincial College and University Natural Science Foundation of Hebei, China (Grant No. QN2016078),

The optical properties of graphene coated D-shaped single mode fiber and photonic crystal fiber are numerically analyzed. Enhancement of the graphene-light interaction is found in graphene coated D-shaped photonic crystal fiber, which introduces a tunable polarization of the D-shaped fiber by changing the chemical potential of the coated graphene. An optimal polarizer model is demonstrated with the extinction ratio of 66.26 dB/mm and the insertion loss of 9.4 dB/mm. The modulator extinction ratios of the TE mode and TM mode are 11.5 dB and 5 dB, respectively, with a device length of 100 μm. This paper provides a theoretical reference for the optical property research of the graphene fiber.

Bending and Orientational Characteristics of Long Period Gratings Written in D-Shaped Optical Fiber

Long period gratings (LPGs) were written into a D-shaped single-mode fiber. These LPGs were subjected to a range of curvatures, and it was found that as curvature increased, there was increasingly strong coupling to certain higher order cladding modes without the usual splitting of the LPGs stopbands. A bend-induced stopband yielded a spectral sensitivity of 12.55 nm/spl middot/m for curvature and 2.2/spl times/10/sup -2/ nm/spl deg/C/sup -1/ for temperature. It was also found that the wavelength separation between adjacent bend-induced stopbands varied linearly as a function of curvature. Blue and red wavelength shifts of the stopbands were observed as the sensor was rotated around a fixed axis for a given curvature; thus, in principle, this sensor could be used to obtain bending and orientational information. The behavior of the stopbands was successfully modeled using a finite element approach.