Optical Fiber Devices Research Articles

Preparation of Low-loss Ge15Ga10Te75 chalcogenide glass for far-IR optics applications

Ge15Ga10Te75 (GGT) glass shows good transparency between 2 and 25μm wavelengths, good chemical and thermal stability to be drawn into fiber, which appears to be a good candidate for developing far-IR fiber-optics devices, although there are strong absorption peaks caused by impurities in the glass. With the aim of decreasing the content of impurities and micro-crystal particles in prepared GGT glass samples, a rapid heating furnace and the fast distillation method based on vapor evaporation plus deposition under vacuum condition was adopted. Properties measurements including Differential Scanning Calorimeter (DSC), Vis–NIR and IR transmitting spectra were performed on the prepared glass samples. Dependence of optical loss on the types of oxygenic getters and their contents and glass quenching temperature was also studied. All these results show that the average optical losses of distilled glass samples were greatly improved by the designated purification processes. Besides, the quality of the glass samples can be improved with the optimized quenching temperature. In all, the optical loss of the glass can be reduced effectively. Minimum optical losses of 0.042dB/mm at 9μm and 0.037dB/mm at 12μm are obtained after a right purification process, which are the lowest loss of the GGT chalcogenide glass nowadays.

Introduction to the issue on biophotonics

The objective of this JSTQE Issue on Biophotonics is to highlight recent progress and trends in innovative biophotonics technology development. The papers published in this issue cover a broad range of advanced biophotonics areas summarized in the following sections: 1) bioimaging: optical coherence tomography and microscopy, nonlinear optical imaging, and novel multimodality imaging approaches; 2) biosensing: multifunctional biosensing, and novel biosensing approaches; 3) biophotonic science: mechanisms of light-cell and lighttissue interactions, advanced modeling methods in biophotonics, and light induced biophotonics effects; 4) biophotonic technology: advanced technologies in biophotonic diagnostics and therapeutics, infrared technology in biophotonics, and novel laser, biomedical and fiber optics tools and devices in biophotonics. These key research topics are highlighted as comprehensive overviews of the current status and future trends, as well as original results and recent developments in the field of biophotonics. This issue contains 33 papers, including 18 invited and 15 contributed papers authored by well-established research groups and promising scientists from all over the world. The invited papers include extended reviews on recent biophotonic developments and clinical applications in the areas of highresolution multispectral bioimaging, combined multifunctional microscopy, nonlinear deep tissue imaging, single molecule imaging, optical coherence elastography, cellular and molecular mechanisms of photobiomodulation, tissue optical clearing, clinical ultrafast laser surgery, infrared laser nerve stimulation, and novel tapered diode lasers for biophotonics. The contributed papers cover a broad variety of key biophotonic research areas including recently obtained original results on multimodal bioimaging and sensing, high resolution phase-sensitive magnetomotive optical coherence microscopy and elastography, and laser-assisted typing of polymorphic human genes.

Use of a Gum Elastic Bougie in a Penetrating Neck Trauma

The case of a patient with a zone II penetrating neck injury who was intubated successfully utilizing the gum elastic bougie (GEB) is reported. He presented at a forward operational base in Afghanistan with a shrapnel wound in his neck as well as a cough and hoarseness. There were two wounds on each side of his laryngeal cartilages. The patient's breathing rate gradually increased and labored inhalation developed while the aeromedical evacuation was delayed for tactical reasons. Subcutaneous emphysema and edema concealed the anatomical landmarks, making a cricothyrotomy unsafe, and no fiber optic devices were available on site. Intratracheal intubation was decided upon by the doctors involved. Because of the anticipated difficultly of intubation, the GEB was used from the outset. During direct laryngoscopy, edema, blood, and mucus concealed the anatomic reliefs of the larynx. The glottis was not visible. On the second attempt, "clicks" were clearly perceived and the tube was railroaded over the bougie. Finally, the patient was evacuated to an Afghan military hospital. In this report, the benefit-risk balance for the use of the GEB in penetrating neck trauma is discussed. Although the use of the GEB cannot be recommended in all cases of penetrating neck injury, it should be considered as an option. This technique is not without risk, but in very remote settings or hostile environments, especially when cricothyrotomy is not possible, it can be lifesaving.

Magnetochiral control of the light phase II: Proposal for a polarization-independent phase shifter

We here propose a fiber-optic device with which the phase of a guided light mode may be continuously changed without modifying the light polarization in any way. The fiber should be chiral, the core containing randomly oriented optically active molecules absorbing in the near–UV–vis region of the electromagnetic spectrum. The fiber would lengthwise be subdivided into two equal halves. One half should contain a given chiral molecular species, the other half the corresponding enantiomer. The guided light would run collinearly to an applied magnetic field generated by an electric coil. The polarization-insensitive phase modulation of the light inside the fiber would be due to the induced magnetochiral birefringence. Natural and magnetic optical activity would be compensated to zero.

Optical Monitoring and Detection of Spinal Cord Ischemia

Spinal cord ischemia can lead to paralysis or paraparesis, but if detected early it may be amenable to treatment. Current methods use evoked potentials for detection of spinal cord ischemia, a decades old technology whose warning signs are indirect and significantly delayed from the onset of ischemia. Here we introduce and demonstrate a prototype fiber optic device that directly measures spinal cord blood flow and oxygenation. This technical advance in neurological monitoring promises a new standard of care for detection of spinal cord ischemia and the opportunity for early intervention. We demonstrate the probe in an adult Dorset sheep model. Both open and percutaneous approaches were evaluated during pharmacologic, physiological, and mechanical interventions designed to induce variations in spinal cord blood flow and oxygenation. The induced variations were rapidly and reproducibly detected, demonstrating direct measurement of spinal cord ischemia in real-time. In the future, this form of hemodynamic spinal cord diagnosis could significantly improve monitoring and management in a broad range of patients, including those undergoing thoracic and abdominal aortic revascularization, spine stabilization procedures for scoliosis and trauma, spinal cord tumor resection, and those requiring management of spinal cord injury in intensive care settings.

All-digital signal-processing open-loop fiber-optic gyroscope with enlarged dynamic range

We propose and realize a new open-loop fiber-optic gyroscope (FOG) with an all-digital signal-processing (DSP) system where an all-digital phase-locked loop is employed for digital demodulation to eliminate the variation of the source intensity and suppress the bias drift. A Sagnac phase-shift tracking method is proposed to enlarge the dynamic range, and, with its aid, a new open-loop FOG, which can achieve a large dynamic range and high sensitivity at the same time, is realized. The experimental results show that compared with the conventional open-loop FOG with the same fiber coil and optical devices, the proposed FOG reduces the bias instability from 0.259 to 0.018 deg/h, and the angle random walk from 0.031 to 0.006 deg/h(1/2), moreover, enlarges the dynamic range to ±360 deg/s, exceeding the maximum dynamic range ±63 deg/s of the conventional open-loop FOG.

Load-insensitive temperature sensor based on azobenzene-chloroform-solution-filled microstructured optical fiber

A solid-core microstructured optical fiber is infiltrated with the Dispersed Yellow 7 and chloroform mixture solution, resulting in the appearance of several transmission dips with different temperature and axial load responses. The temperature- and load-dependent spectral characteristics of these dips have been investigated and the experimental results indicate that they are pretty temperature-sensitive, but insensitive to the variation of applied axial load. Such a compact fiber-optic device with electric perturbation immunity could be employed for load-insensitive temperature sensing with high sensitivity.

Numerical analysis of optical propagation characteristics of side-polished photonics crystal fiber

In order to design new all optical fiber devices based on side-polished photonics crystal fiber (SPPCF), we analyzed optical propagation characteristics of SPPCF with different polished parameters, such as residual radius R, polished length z along the PCF, and azimuth. The optical transmittance and the evolution of transverse mode along the SPPCF with a hexagonal arrangement of air hole on cross section were calculated and analyzed. The simulation shows that optical power transmittance in SPPCF decreases and oscillates with the increase of polishing length z. The evolutions of the transverse mode for different polishing azimuth become significant different from each other when the residual radius is polished to be less than 0.5 $$\upmu $$ m. In the polished area, the propagation mode $$\hbox {LP}_{01}$$ , which is originally launched at the input of SPPCF, will spread out and be coupled to high order propagation modes and radiation mode. The shorter the R is, the smaller the optical power transmittance of SPPCF will be. The optical transmittances of SPPCF as a function of R is very dependent on the polishing azimuth when R is in range from $$-$$ 0.5 to $$+$$ 0.5 $$\upmu $$ m The results will provide meaningful reference in design and fabrication of SPPCF-based devices.

Microalgae dual-head biosensors for selective detection of herbicides with fiber-optic luminescent O2 transduction

The microalgal species Dictyosphaerium chlorelloides (D. c.) was immobilized into porous silicone films and their photosynthetic activity was monitored with an integrated robust luminescent O2 sensor. The biosensor specificity towards a particular pesticide has been achieved by manufacturing a fiber-optic dual-head device containing both analyte-sensitive and analyte-resistant D. c. strains. The latter are not genetically modified microalgae, but a product of modified Luria–Delbrück fluctuation analysis followed by ratchet selection cycles. In this way the target herbicide decreases the O2 production of the analyte-sensitive immobilized strain without affecting the analyte-resistant population response; any other pollutant will lower the O2 production of both strains. The effect of the sample flow-rate, exposure time to the herbicide, biomass loading, biosensor film thickness, intensity of the actinic light, illumination cycle, and temperature on the biosensor response has been evaluated using waterborne simazine as test bench. The biosensing device is able to provide in situ measurements of the herbicide concentration every 180min. The biosensor limit of detection for this herbicide was 12μgL−1, with a working range of 50–800μgL−1. The biosensor specificity to simazine has been assessed by comparing its response to that of isoproturon.

Fabrication and Optical Characterization of Strain Variable PDMS Biconical Optical Fiber Taper

We demonstrate a promising fabrication technology and basic optical characteristics of prepared strain variable polydimethylsiloxane (PDMS) biconical optical fiber taper. For its preparation, silicone elastomer Sylgard 184 was used. Strain dependence of the PDMS fiber taper shows up to 140% elastic elongation. In the process of elongation of the PDMS fiber taper, the measured intermodal interference points to its employment for different sensor applications and opens new areas for developing various types of strain variable PDMS optical fiber devices.

The Servo Control System of Fabrication System for Optical Fiber Gratings Written Online

Nowadays, as a new type of optical fiber devices, with flexible structure characteristic and steady frequency-selecting performance among the key support device areas of optic fiber technology, Fiber Bragg Grating (FBG) is rapidly developed as an very important basic device.Therefore, the study of phase mask plate which will be good for the mass production of the optical fiber gratings is becoming a central issue. The appearance of phase mask plate technology makes the industrialized production of fiber optical gratings with a stable wavelength possible. This paper based on the optical fiber gratings written online is mainly about the study of related servo control system. By the design of the servo control system of phase mask plate, we will get the ideal purposes that phase mask plate is precisely positioned, torque of plate is increased and the time of picking any plate is undifferentiated.

Fiber Bragg gratings for microwave photonics subsystems

Microwave photonics (MWP) is an emerging filed in which photonic technologies are employed to enable and enhance functionalities in microwave systems which are usually very challenging to fulfill directly in the microwave domain. Various photonic devices have been used to achieve the functions. A fiber Bragg grating (FBG) is one of the key components in microwave photonics systems due to its unique features such as flexible spectral characteristics, low loss, light weight, compact footprint, and inherent compatibility with other fiber-optic devices. In this paper, we discuss the recent development in employing FBGs for various microwave photonics subsystems, with an emphasis on subsystems for microwave photonic signal processing and microwave arbitrary waveform generation. The limitations and potential solutions are also discussed.

An Optical Fiber-Based Gating Device for Prospective Mouse Cardiac MRI

Prospective synchronization of MRI acquisitions on living organisms involves the monitoring of respiratory and heart motions. The electrocardiogram (ECG) signal is conventionally used to measure the cardiac cycle. However, in some circumstances, obtaining an uncorrupted ECG signal recorded on small animals with radio frequency (RF) pulses and gradient switching is challenging. To monitor respiratory motion, an air cushion associated with a pressure sensor is commonly used but the system suffers from bulkiness. For many applications, the physiological gating information can also be derived from an MR navigated signal. However, a compact device that can simultaneously provide respiratory and cardiac information, for both prospective gating and physiological monitoring, is desirable. This is particularly valid since small volume coils or dedicated cardiac RF coil arrays placed directly against the chest wall are required to maximize measurement sensitivity. An optic-based device designed to synchronize MRI acquisitions on small animal's respiratory and heart motion was developed using a transmit-receive pair of optical fibers. The suitability of the developed device was assessed on mice ( n = 10) and was based on two sets of experiments with dual cardiac and respiratory synchronization. Images acquired with prospective triggering using the optical-based signal, ECG, and the pressure sensor during the same experiment were compared between themselves in the first set. The second set compared prospective technique using optical-based device and ECG to a retrospective technique. The optical signal that was correlated to both respiratory and heart motion was totally unaffected by radiofrequency pulses or currents induced by the magnetic field gradients used for imaging. Mice heart MR images depict low-visible motion artifacts with all sensors or techniques used. No significant SNR differences were found between each series of image. Full fiber-optic-based signal derived from heart and respiratory motion was suitable for prospective triggering of heart MR imaging. The fiber optic device performed similarly to the ECG and air pressure sensors, while providing an advantage for imaging with dedicated cardiac array coils by reducing bulk. It can be an attractive alternative for small animal MRI in difficult environments such as limited space and strong gradient switching.

Analysis and characterization of Er–Yb codoped-depressed inner cladding fiber

A 125 μm-diameter erbium-ytterbium-codoped single-mode fiber is reported. The utilization of depressed inner cladding guarantees the improvement of trade-off between the effective area and bending sensitivity compared to step-index profiles. Changes of cutoff wavelength, effective area, and macrobend loss under the influence of various structural parameters, and the balancing selection of core radius and subsidence layer width are investigated systematically. For the laboratory-made depressed inner cladding fiber, a macrobend loss of 0.06 dB/loop for a bending radius as tight as 10 mm was achieved, while maintaining an effective area of 164.22 μm² with intact single-mode properties at 1550 nm. The maximum small signal gain was achieved at 40.9 dB, and the gain fluctuation was less than 1 dB at the C-band. The fiber is suitable for high-power, small, portable, and handy optical fiber devices.

Exciting the optical response of nanowire metamaterial films on the tip of optical fibres

AbstractThis Letter reports on the assembly on the tip of an optical fibre of a metamaterial film fabricated by a self‐assembly bottom‐up method, composed of silver nanowires embedded in an alumina matrix. By illuminating the film through the fibre in a reflection configuration, we observe experimentally the optical response of the metamaterial in agreement with theoretical predictions and interpreted as the excitation of surface plasmon‐polaritons in the cylindrical surface of the nanowires. These results pave the way for low‐cost optical fibre devices that incorporate metamaterial films.magnified imageMicrographs of a nanowire metamaterial film mounted on the tip of an optical fibre (left) and top‐view of the sample in a transmission configuration (right). The red colour results from the absorption of the other optical wavelengths by the plasmon modes in the metamaterial.(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

MICRO-SCALE METHOD FOR SEPARATION AND QUANTIFICATION OF ATENOLOL AND HYDROCHLOROTHIAZIDE BY SEQUENTIAL INJECTION CHROMATOGRAPHY

A microscale stopped-flow separation manifold, which is termed sequential injection chromatograph (SIC), was exploited for separating and quantifying atenolol and hydrochlorothiazide. A short C18 separation column (4.6 × 25 mm) with a monolithic structure was used to offer a rapid and sufficient separation. Microscale fiber optic spectrometric devices were coupled with the SIC manifold for UV detection at 220 nm. The proposed SIC method was optimized, validated, and applied to both formulations single and binary mixture. The mobile phase composition (MPC) was optimized using the 23 full-factorial design approach while other conditions were optimized using the univariate approach. The optimum MPC was 40 µmol/L phosphate:methanol:acetonitrile (85:7.5:7.5, v/v/v) at pH 3.0. Other optimum conditions were 40 µL/s for flow rate and 40 µL for sample volume. Satisfactory separation with a resolution of 1.6 and numbers of theoretical plates of more than 630 was achieved. The interesting features of the proposed SIC method are the microliter-scale of the consumed volume of mobile phase (3.50 mL) and high sample frequency (23 samples/hr).

Fiberoptic microneedle device facilitates volumetric infusate dispersion during convection‐enhanced delivery in the brain

A fiberoptic microneedle device (FMD) was designed and fabricated for the purpose of enhancing the volumetric dispersal of macromolecules delivered to the brain through convection-enhanced delivery (CED) by concurrent delivery of sub-lethal photothermal hyperthermia. This study's objective was to demonstrate enhanced dispersal of fluid tracer molecules through co-delivery of 1,064 nm laser energy in an in vivo rodent model. FMDs capable of co-delivering fluids and laser energy through a single light-guiding capillary tube were fabricated. FMDs were stereotactically inserted symmetrically into both cerebral hemispheres of 16 anesthetized rats to a depth of 1.5 mm. Laser irradiation (1,064 nm) at 0 (control), 100, and 200 mW was administered concurrently with CED infusions of liposomal rhodamine (LR) or gadolinium-Evans blue-serum albumin conjugated complex (Gd-EBA) at a flow rate of 0.1 µl/min for 1 hour. Line pressures were monitored during the infusions. Rodents were sacrificed immediately following infusion and their brains were harvested, frozen, and serially cryosectioned for histopathologic and volumetric analyses. Analysis by ANOVA methods demonstrated that co-delivery enhanced volumetric dispersal significantly, with measured volumes of 15.8 ± 0.6 mm(3) for 100 mW compared to 10.0 ± 0.4 mm(3) for its fluid only control and 18.0 ± 0.3 mm(3) for 200 mW compared to 10.3 ± 0.7 mm(3) for its fluid only control. Brains treated with 200 mW co-delivery exhibited thermal lesions, while 100 mW co-deliveries were associated with preservation of brain cytoarchitecture. Both lethal and sub-lethal photothermal hyperthermia substantially increase the rate of volumetric dispersal in a 1 hour CED infusion. This suggests that the FMD co-delivery method could reduce infusion times and the number of catheter insertions into the brain during CED procedures.

Effect of metalizing nickel on the spectrum of fiber Bragg grating

Metal coating can provide fiber Bragg grating (FBG) effective protection and improve the FBG sensor's performance in harsh environ- ments. However, the metalizing can impact the optical properties of the FBG. As a result, the sensor accuracy of FBG will lower. The reason for the effect is the stress produced in the metalizing. In this study, we coated the FBG by the electroless-electroplating method. The common changes of the FBG's spectrum after the metalizing were apparent side-lobes and reduced peak loss, and the hysteresis error for temperature sensor was more than 3.5°C. To reduce the deformation of the FBG's spectrum in the metalizing, we analyzed the origin of stress, calculated the FBG's refractive index perturbation due to the thermal stress, and simulated the spectrums of FBG under different stress distributions. On the basis of this, we developed a stress control technology. After using the technology, the optical properties of the metal-coated fiber Bragg gratings have been retained, and their hysteresis errors for temperature sensors were less than 1.5°C. The results showed good repeatability. The study can be used for regulating metalizing processes, and for pro- viding valuable information for metalizing other optical fiber devices. © 2013

Dynamic micro-air-bubble drifted in a liquid core fiber Fabry-Pérot interferometer for directional fiber-optic level meter

We propose a dynamic, directional, and miniature fiber-optic level meter based on a micro-air-bubble drifted in a liquid-core fiber Fabry-Pérot interferometer. The proposed in-fiber level meter can detect the non-horizontal/horizontal state of an object/structure and also be able to discriminate the test structure inclining to the clockwise or counterclockwise directions by measuring the spectral responses of the proposed optical fiber device. Dynamic drifting of the micro air bubble in the tilted condition has been recorded which investigates the drifted directions correlated closely with the tilted directions in the fiber level meter.

Fiber Optic Hybrid Device for Simultaneous Measurement of Humidity and Temperature

A novel fiber optic hybrid device for simultaneously measuring temperature and relative humidity (RH) is proposed and demonstrated in this paper. The device is composed of a fiber Bragg grating (FBG) and a reflection type photonic crystal fiber interferometer (PCFI) infiltrated with humidity sensitive material Agarose. The Agarose infiltrated PCFI is used to monitor the RH and an in-line FBG is used to monitor the temperature. The temperature is measured by detecting the shift in the Bragg wavelength and the humidity is measured by monitoring the change in the optical power of the reflected spectrum. The sensor shows a temperature sensitivity of 9.8 pm/°C and an optical power variation of >7 dB for an RH change of 75%, with less cross sensitivity.