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Recent developments in 3D micromixers promise to accomplish satisfactory mixing for applications in microchemical process, biomicrofluidic analyses, μ-TAS, etc. However, the complicated 3D architecture employed to ensure thorough mixing might reduce fluid circulation due to the space for fluid flowing becomes narrow. In this study, we developed a single 3D multi-manifold micromixer composed of a double-Archimedes-screw for rapidly mixing within a short distance. Archimedes screw is well known for its fluid circulation under stable flow. The mixing strategy is based on split-and-recombination for increasing the interfacial area, and the 3D flow rotation for generating omnidirectional momentum-changes during the fluid propagation. With the spiral conformation, the Archimedes-screw micromixer (ASM) can substantially enhance fluid circulation. Numerical simulations used to help to design the optimal screw-turn show that satisfactory mixing efficiency can achieve at the distance of approximately twice the microchannel width. The ASM characteristics, such as pressure loss, ratio of cross-sections, and Reynolds number (Re) were evaluated. Experimental demonstration by an ASM fabricated by two-photon stereolithography showed mixing result in good agreement with the simulation findings.

In this paper, a semiconductor optical amplifier (SOA) based 1064 nm fiber ring laser with 63.56 dB optical signal-to-noise ratio (OSNR) is demonstrated. The stable performance is measured for six hours with lasing peak variation of ≤±0.115 dB and wavelength variation of ≤±0.006 nm. Combining the fiber ring laser with fiber Bragg gratings (FBGs), the SOA based fiber ring laser is applied to sense stretch, squeeze, and temperature variation. The results show high linearity, which is suitable for interpolation method prediction and evaluation. A large dynamic range of up to 10 km is also demonstrated for remote sensing applications.

The analysis of surface antigens on cells, especially red blood cells (RBCs), has attracted increasing attention due to the recognition of antigenic variation that can facilitate early diagnoses. This paper presents an alternative methodology to estimate the variation of surface antigen expressions using an optical cell-detachment technique to validate the binding of individual RBCs stuck on corresponding antibody-coated surfaces. The detachment tests were implemented by an optical tweezers with gradually decreasing laser powers associated with serial antibody dilutions. Then, the antigen expression variation was estimated based on the known antibody dilution folds. The B- and B3-types of RBCs were selected for the demonstration subjects. With the semi-quantitative analysis, the proposed methodology was successfully verified for evaluating the variation of the RBC surface antigen expressions. The analysis result shows good consistency with the literature’s findings.

Lattice structures are superior to stochastic foams in mechanical properties and are finding increasing applications. Their properties can be tailored in a wide range through adjusting the design and dimensions of the unit cell, changing the constituent materials as well as forming into hierarchical structures. In order to achieve more levels of hierarchy, the dimensions of the fundamental lattice have to be small enough. Although lattice size of several microns can be fabricated using the two-photon polymerization technique, sophisticated and costly equipment is required. To balance cost and performance, a low-cost high resolution micro-stereolithographic system has been developed in this work based on a commercial digital light processing (DLP) projector. Unit cell lengths as small as 100 μm have been successfully fabricated. Decreasing the unit cell size from 150 to 100 μm increased the compressive stiffness by 26%. Different pretreatments to facilitate the electroless plating of nickel on the lattice structure have been attempted. A pretreatment of dip coating in a graphene suspension is the most successful and increased the strength and stiffness by 5.3 and 3.6 times, respectively. Even a very light and incomplete nickel plating in the interior has increase the structural stiffness and strength by more than twofold.

The quantitative analysis of surface antigens on cells, especially red blood cells (RBCs), has attracted increasing attention due to the recognition of antigenic changes that can facilitate early diagnoses. This paper presents an alternative methodology developed using the optical cell-detachment technique to evaluate antibody-antigen interactions and quantitatively analyze the RBC surface antigen expression. RBC subtyping was used to verify the proposed detection principle based on a comparison of the bonding strengths between individual RBCs and antibody coatings. The bonding strengths were measured with serial antibody dilutions with gradually decreasing laser powers, for which a single cell was optically detached from the corresponding antibody-coated surface. With the quantitatively analysis, the proposed alternative methodology was verified as a highly sensitive technique for detecting antigen expression on the RBC surface.

Wall thinning defects in steel pipes are usually localized and are difficult to detect using traditional sensors that have a small coverage and limited measuring range. A distributed fiber sensor, based on the Brillouin backscattering sensing system, has been demonstrated to be able to measure the strain and detect the defect in a pipe accurately. A 1.8 m pipe segment that contains artificial thinning from 13 to 60% of wall thickness at various positions was subjected to an internal pressure of 350 kgf/cm2. Hoop strain distribution along the whole pipe segment was monitored by a single optical fiber. The measured strains compared favorably with strain gauge results. The method proposed in this study shows promising results for the detection of the existence and location of wall thinning defects in long distance pressurized pipe.

By collecting information from the indictment and news media reports, this paper tries to probe into some aspects of the course of the rupture failure in the pipeline that is believed to have led to the 2014 Kaohsiung gas explosion incident. Through approximate finite element analysis and engineering assessment of a similar pipe segment, insight can be gained on the sequence of longitudinal and circumferential fracture, as well as the relationship between the degree of wall thinning and rupture pressure. Some of the deductions are found to corroborate the visual appearance of the rupture. Other deductions need further information from a detailed mapping of the wall thickness of the ruptured segment to substantiate. A mass transfer analysis for the leakage rate is recommended to help identify the approximate time of rupture. A detailed charting of the positions of corrosion damage and possible asphalt coating damage on the three pipe segments inside the culvert may provide further clues for identif...

Two-photon polymerization enables the extremely high resolution three-dimensional printing of micro-structures. To know the mechanical properties, and better still, to be able to adjust them is of paramount importance to ensuring the proper structural integrity of the printed products. In this work, the Young’s modulus is measured on two-photon polymerized micro-cantilever bars. Optimizing the scanning trajectory of the laser focus points is important in alleviating distortion of the printed bars. By increasing the laser power and decreasing the inter-voxel distances we can double the Young’s modulus. Post-curing with ultraviolet light can approximately quadruple the Young’s modulus. However, the resulting modulus is still only about 0.3% of that of the bulk polymerized material.

A wide-tuning range linear cavity C+L band tunable fiber laser is proposed in this paper. By using 3-point bending device to facilitate wavelength tuning of fiber Bragg gratings (FBGs), a scheme with two parallel strain-tunable FBGs (TFBGs) is demonstrated in L band operation. A large tuning range of over 22.5 nm with 0.1 nm precise resolution for each TFBG is obtained. The overlapping tuning range for two TFBGs is from 1564 to 1600.5 nm with 2 dB power variation. Using 10 M Erbium-doped fiber (EDF) and 100 mW pumping power, the stable lasing output power is measured at 1582.0 nm with threshold pump power and side mode suppression ratio (SMSR) of 10 mW and 50 dB, respectively. And the measured slope efficiency is 11.5% corresponding to quantum efficiency of 12.3%.

This study introduces an innovative micromachine that enables precise measurement of the flow rate at the micron scale (μl/min) in microfluidic channel. It is fabricated by the state-of-the-art technique of two-photon polymerization and consists of: a rod-spring, a water-drop-shaped frame, and an indicator situated inside a microfluidic channel. The indicator is deflected by the flowing fluid while restrained by the spring to establish an equilibrium indication according to the flow rate. In the practical tests, the flow successfully agitates the spring in a proper deflection. The relationship between the flow rate and the deflection angle was calibrated.

It has been shown that impact damage to composite materials can be revealed by embedded Fiber Bragg Gratings (FBG) as a broadening and splitting of the latter’s characteristic narrow peak reflected spectrum. The current work further subjected the impact damaged composite to cyclic loading and found that the FBG spectrum gradually submerged into a rise of background intensity as internal damages progressed. By skipping the impact, directing the impact to positions away from the FBG and examining the extracted fibers, we concluded that the above change is not a result of deterioration/damage of the sensor. It is caused solely by the damages initiated in the composite by the impact and aggravated by fatigue loading. Evolution of the grating spectrum may therefore be used to monitor qualitatively the development of the incurred damages.

We proposed and demonstrated a 100 km hybrid C+L band fiber amplifier in the bridge-type scheme. It is composed of a C-band erbium-doped fiber amplifier (EDFA) and an L-band Raman fiber amplifier (RFA) using double-pass dispersion compensators in a loop-back scheme. Dispersion slope mismatch is compensated precisely for all C+L band channels by writing fiber Bragg gratings (FBGs) at appropriate locations. Gain variation among multiple channels can be reduced to ±0.2 dB. The pump efficiency is improved by recycling the residual pump power. The C/L band WDM coupler which at merged point rejects C band amplified spontaneous emission (ASE) using L band coupler and vice versa. Both the simulation results and experimental measurements are realized in this paper. The hybrid EDFA/RFA may find vast applications in WDM long-haul systems and optical networks.

Cyclic fatigue of rotary endodontic instruments has been tested using different techniques while the results were normally compared in terms of a canal curvature radiusRand an angular extent of instrument insertionθ. In this work, the effects of canal geometry and analysis method have been investigated by finite element (FE) analysis. A highly simplified FE model has been proposed and verified experimentally. Results from a detailed finite element (FE) model and a simple geometric model are discussed in the light of the simplified model results. It was found that the commonly used (R,θ) alone cannot quantify the severity of bending. The diameters and taper development of the canal and the instrument also played important roles. The simple geometric model can give unacceptable errors and cannot only be employed forensically. The detailed finite element model is much more resource consuming than the current simplified model and the extra effort is not worthwhile if only the bending strain is needed for correlation and prediction of instrument fatigue life.

We proposed a remote pumped bidirectional C+L band fiber amplifier for wavelength division multiplexing passive optical network. A high-reflectivity pump reflector using three cascading fiber Bragg gratings is designed to reflect the residual pump power for L-band amplification. Both the gains for C-band and L-band are larger than 10.0 dB under −10 dBm launched power. Using the remote pumped bidirectional fiber amplifier, the power penalty is only 0.82 dB after 10 Gb/s, 24 km bidirectional transmission. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2553–2556, 2013

During clinical operation in root canals, NiTi endodontic rotary instruments are subjected to alternating tension and compression and are prone to accidental fracture without prior warning. Once broken, extracting the fractured part from the canal is difficult and is annoying to both the patient and the dentist. Warning of an imminent fracture during clinical use will be a great help to avoid medical and legal complications. To this end, a monitoring technique that involves the picking up and analysis of the stress wave signals due to the cutting and rubbing at the canal wall-instrument blade interface was investigated. Both the stress wave conducted through solid and the sound wave conducted in air were monitored. The former was picked up by a Fiber Bragg Grating (FBG) and the latter with a microphone. When cracking developed in a rotary instrument, we expect the natural vibration frequency of the instrument as well as the characteristics of cutting/rubbing with the canal wall change. From the raw signal intensity history, it is possible to differentiate whether the instrument is operating but there is no clue when a fatigue crack has initiated. By employing Fast Fourier Transform (FFT) on the signal, we can reveal the energy associated with different frequencies. With characteristic frequency we refer to the frequency that is associated with the highest signal intensity. It was found that the energy intensity of the characteristic frequency varied in a well-defined pattern during the process of fatigue testing of the rotary instrument. Towards the end of fatigue life, a large intensity spike of the characteristic frequency was observed and this was shown to be associated with the occurrence of a fatigue crack. It is hoped that with this information, the fatigue failure of rotary instruments can be closely monitored to avoid/alleviate the occurrence of unexpected fracture during clinical use.

Standard fatigue crack propagation (FCP) test placed strict requirement on specimen size. FCP rate in subsize specimen was found to be slightly but consistently slower than that in the standard specimens. Based on a critical study on two aluminum alloys and two steels, we found the lower rates can be attributed to the plane stress state in the miniature specimens being different from that in the standard specimens. By taking account of crack closure, the miniature specimen data are brought in line with the standard specimen results and may serve as an upper bound estimate of FCP properties.

A nearly single-frequency selection is realized in a linear-cavity fiber laser constructed using a Faraday rotator mirror (FRM) and a partial reflectance fiber Bragg grating (FBG) as the cavity ends. At 1552.46 nm wavelength, the measured optical signal-to-noise-ratio (OSNR) is 58.5 dB with a linewidth less than 400MHz obtained using a subring cavity and a polarization controller as the mode filters. The pumping efficiency is improved by 10% by recycling the residual pump power to the gain medium.

An L-band tunable linear cavity fiber laser using a fiber Bragg grating (FBG) and wavelength reflector as cavity ends is investigated. A four-lamina composite device is used to facilitate tunable wavelength with 0.1-nm tuning resolution. Two strain-tunable FBGs are demonstrated with whole tuning range from 1574.5 to 1602.4 nm. A stable lasing output power at 1582.0 nm has 11.5 mW threshold pump power and 59 dB side-mode suppression ratio, respectively, using 10 M erbium-doped fiber and 100 mW pump power. The measured slope efficiency is 12.2% corresponding to 13.0% of quantum efficiency. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2681–2683, 2014

A distributed Brillouin fiber sensor was used to monitor the health of steel structures. We used this method on two steel beam specimens and longitudinal strain and cracks were detected well under different loads. The difference between the longitudinal strain measured by the distributed fiber sensor and that measured by strain gages is less than 4%. Traditional sensors or transducers that measure the average strain over a small region always miss cracks. The method proposed in this study gives very good results for the detection of cracks and the surrounding strain on a square pipe.

There are situations where baseline fatigue crack propagation (FCP) data are needed but the available material for its evaluation is far from enough to fabricate full sized standard specimens. Miniature specimen testing techniques have been proposed but published data seems to be slightly but consistently slower under the same stress intensity than that from standard specimen results. In this work, an aluminum alloy and a steel, which have vastly different mechanical behaviors, are used to generate different stress states and premature crack closure to allow the validity of miniature specimen FCP data to be critically examined.

The room temperature stiffness and strength of 6061 Al alloy fabricated by powder metallurgy (PM) are markedly improved by SiC reinforcement but such beneficial effects are lost at 300 °C. The fatigue crack growth resistance is in general improved by over-aging, the LT orientation and SiC reinforcement but decreased by rising temperature. As the fracture toughness decreases with increasing amount of reinforcement, the unreinforced alloy exhibited better crack growth resistance than the reinforced composites for growth rates greater than 5 × 10 −4 mm/cycle at all temperatures. The difference in growth resistance is discussed in terms of the microstructural and fractographic evidences.

A single-longitudinal-mode selection is realized in a linear-cavity fiber laser construction using a loop-back optical circulator and a partial reflectance fiber Bragg grating as the cavity ends. At 1551 nm wavelength, the measured signal-to-noise-ratio is 56 dB and with a line width less than 1 MHz obtained using multiple subring cavities as mode filters. The pumping efficiency is 10% improved by recycling the residual pump power to gain medium.

Fatigue fracture of rotary file inside the root canal of teeth is one of the important equipment failure modes in endodontic treatment. Knowing the curvature of a file in a root canal allows its bending strain and fatigue life to be estimated. This can help to avoid the highly undesirable fracture. Although the canal geometry can be revealed by X-ray radiograph, its 2-D nature may not correctly reflect the true curvature. Moreover, canal curvature is not equivalent to the curvature of an inserted file.

Experimental and numerical analyses have been carried out to demonstrate the feasibility and evaluate the limitation of using fiber Bragg gratings for impact source location on a cold-rolled aluminum plate. Within the area enveloped by a four-FBG-array, source location is reasonably accurate. Beyond that area, prediction error may not be acceptable. Numerical simulations show that such error may be attributed to the limitation of equipment resolution on the one hand, and angular insensitivity of the FBG on the other hand. Based on the results, it is reasoned that prediction accuracy can be improved by employing stronger light source, steeper filter response, and orthogonal rosettes instead of single axis FBGs.

An impact monitoring system using an array of fibre Bragg grating (FBG) sensors has been established on a wind turbine blade. The effect of sensor layout on detection capability has been investigated. The possibility to identify the location of an impact is also discussed. This preliminary work may shed some light on how to establish an optimal monitoring system with a minimum number of sensors while achieving an acceptable sensitivity and coverage. With such a system, the corresponding strain history and occurrence of local damage can be monitored, thus helping to narrow down the scope for detailed examination during an overhaul and enabling the integrity of a wind turbine blade to be more reliably assessed.

Some structures are vulnerable to localized internal damages incurred by impact of small objects. An impact monitoring system using fiber Bragg grating (FBG) sensors has been established. Its ability to detect very low to medium energy impacts has been demonstrated on an aluminum plate and a 22 m long wind turbine blade. Previous analysis of this technique showed that the accuracy by which an impact position can be located is limited by equipment noises and angular insensitivity of the FBG. By employing two intensity demodulation schemes with different demodulation sensitivities and ranges, we try to differentiate the relative importance of the above limiting effects. Based on the results, directions for further improvement on impact source locating accuracy will be discussed and the implication of applying such systems on large-scale structures will be examined.

This paper reports on the development of a distributed sensing floor using an optical fiber sensor. We introduce an alternative yet simple method to manufacture a distributed sensing floor. This method is based on Brillouin optical correlation domain analysis (BOCDA) technology, which can detect the strain deviation along a fiber caused by pressure events. With suitable computational algorithms, the distributed sensing floor is able to detect the presence of occupants and track them efficiently. In our tests, the success rate of location detection was 96%, and the estimation error for the weight of the occupant was plusmn5 kg. The spatial resolution could be tuned without having to also change the hardware architecture.

An impact monitoring system using an array of fibre Bragg grating (FBG) sensors has been established on a wind turbine blade. The effect of the locations and detection capability of the FBG have been investigated. The possibility to identify the location of an impact is also discussed. This preliminary work may shed some light on how to establish an optimal monitoring system with a minimum number of sensors while achieving the acceptable sensitivity and coverage. With such a system, the corresponding strain history and occurrence of local damage can be monitored, thus helping to narrow down the scope of more detailed examination during an overhaul and enabling the integrity of a wind turbine blade to be more reliably assessed and monitored.

Infiltrating foreign materials into a fatigue crack has been attempted in a number of works to suppress the progress of the crack. Previous works have been limited to through-the-thickness cracks in standard laboratory specimens. By forcing in from one surface and letting out from the other, it is relatively easier to transport foreign materials into a through-thickness crack. Part-through surface cracks are more common in practice. It will be more difficult to bring about a good infiltrant penetration to ensure effective crack growth suppression. In the current work, a special fixture has been developed to induce polymeric resin into a surface fatigue crack in a cylindrical rod. A good infiltrant penetration and crack growth retardation of more than one order of magnitude have been achieved. The relative merits of using the conventional crack closure concept and the one based on Paris et al.’s partial crack closure model to predict the resulting retardation have been investigated.

The influence of c content and its morphology on the impact and fatigue crack growth behavior of 2205 duplex stainless steel (DSS) welds were studied in this work. Short time post-heating was able to effectively raise the c content and the impact toughness of the weld. The variation in microstructures showed less influence on the fatigue crack growth rate (FCGR) of the steel plate and weld except in the low DK regime. In contrast, residual welding stresses played a more significant affection on the FCGR of the DSS weld than microstructural factors did. Plastic deformation induced martensitic transformation within a definitely thin layer was responsible for the difference in crack growth behavior between specimens in the low DK range. Coarse columnar structure was more likely to have tortuous crack path in comparison with the steel plate. � 2007 Elsevier Ltd. All rights reserved.

Slow-displacement rate tensile tests were carried out to investigate the effect of hydrogen embrittlement on notched tensile strength (NTS) and fracture characteristics of 2205 duplex stainless steel weld. The hydrogen embrittlement susceptibility of the specimens was correlated with microstructures of the fusion zone. The results indicated that all the specimens were susceptible to gaseous hydrogen embrittlement but to different degrees. The susceptibility decreased with increasing austenite content in the weld metal. The orientation with respect to the rolling direction had a great influence on the impact toughness of the base plate. Preheating before welding or changing the plasma-assisted gas from He to N2 could raise the content of the fusion zone and improve the impact toughness. In case of the post-weld heat-treated weld (PW), the presence of randomly oriented acicular and blocky in the fusion zone led to the highest impact energy and NTS among the specimens being tested. Scanning electron microscopy (SEM) fractographs revealed that all specimens underwent a significant change in fracture mode from ductile in air to quasi-cleavage fracture in H 2. © 2004 Elsevier B.V. All rights reserved.

We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.

In the evaluation of fatigue crack propagation properties, standard specimens such as the compact tension (CT) or center cracked specimens are commonly employed. However, these specimens are not applicable when the available material for testing is of a long axial length but small cross-sectional area. Surface cracked rod specimens may be used for this purpose. In the current work, to shed light on their applicability to the evaluation of fatigue crack propagation properties, surface cracked rod specimens were tested under axial tension. The development of the surface cracks was examined. Fatigue crack propagation data at the surface and in the deepest interior point of the surface cracks in different diameter rods were obtained. Comparison showed that rods with diameters of 8 mm and larger give fatigue crack propagation data similar to that given by compact tension specimens. For a 6 mm diameter rod specimen, growth rates were slightly higher than the standard if correlated in terms of ΔK but, fall in line with the standard, if crack closure was taken into account.

The 3D laser direct-writing technology is aimed at the modeling of arbitrary three-dimensional (3D) complex microstructures by scanning a laser-focusing point along predetermined trajectories. Through the perspective technique, the details of designed 3D structures can be properly fabricated in a microchannel. This study introduces a direct reading flow meter and a 3D passive mixer fabricated by laser direct writing for microfluidic applications. The flow meter consists of two rod-shaped springs, a pillar, an anchor, and a wedge-shaped indicator, installed inside a microfluidic channel. The indicator is deflected by the flowing fluid while restrained by the spring to establish an equilibrium indication according to the flow rate. The measurement is readily carried out by optical microscopy observation. The 3D passive Archimedes-screw-shaped mixer is designed to disturb the laminar flow 3D direction for enhancing the mixing efficiency. The simulation results indicate that the screw provides 3D disturbance of streamlines in the microchannel. The mixing demonstration for fluids flowing in the micrchannel approximately agrees with the simulation result. Thanks to the advantage of the laser direct writing technology, this study performs the ingenious applications of 3D structures for microchannels.

Mechanical properties characterization is needed in many industrial applications yet sufficient amount of material for fabricating standard-sized testing specimens is often not available. Techniques for testing miniaturized specimen must be adopted. Much effort has been made to develop techniques for impact, fracture toughness and tensile properties of sub-sized specimens. Work on the testing of fatigue properties is more limited. In this study, fatigue crack propagation behavior is evaluated from the growth of surface crack in a cylindrical rod under tension. Rods of various lengths and diameters were tested. As the size of the rod specimen is reduced, the fatigue crack growth rate tends to increase when correlated using the stress intensity factor range. This increase is explained largely by the decrease in the degree of premature crack closure in the small specimens. Valid fatigue crack growth data can be obtained among the specimens examined except on the crack growth on the surface of the smallest specimen, which has a length of 26 mm and diameter of 8 mm. Even so, valid data can still be elucidated on the latter specimen if the interior growth is considered. The dimensions of the latter specimen allow fatigue properties to be evaluated using broken remnants from impact or other test specimens.

This work aims at assessing the use of embedded fiber Bragg grating to monitor the internal damage evolution in polymeric composite during fatigue loading . The results suggested that the embedded FBGs have good potentials to detect the appearance of damage and to differentiate the damage types. The evolution in light spectrum during fatigue may be divided into four stages when compared against X-ray, C-scan and optical microscope (OM) results. These stages are associated with (1) matrix cracking in 90o lamina; (2) fiber splitting in the ±45o laminae; (3) fiber splitting in the 0o lamina ; and (4) delamination.

Cyclic loading during service may induce sub-surface defects in polymeric composite materials. These insidious defects may grow and eventually lead to catastrophic failures. The current work aims at exploring the possibility of using embedded fiber Bragg grating to monitor damage evolution. Fatigue damage evolution in Graphite/Epoxy coupons having a [−45/90/+45/0] 2s lay-up sequence with a central circular hole subjected to cyclic loading is evaluated. This study suggested that the embedded fiber bragg gratings have good potentials to detect the appearance of damage. It is hoped that this methodology can be further developed as an online condition monitoring technique for safety-critical structures, thereby improving the safety and reliability of composite structures.

The thermal drift coefficient of the Bragg wavelength of fiber Bragg grating (FBG) is unacceptably high when the FBG is used as a wavelength reference or a wavelength‐selective passive component, especially in a dense wavelength division multiplexing (DWDM) system. A light, small and robust carbon fiber reinforced polymeric composite structure is proposed to compensate for the temperature induced wavelength drift in FBG. It has been shown to be able to reduce the temperature induced wavelength shift of a fiber Bragg grating from 10 pm/°C to below 1 pm/°C. Stability in long term performance over a two month period has also been demonstrated. A fabrication route that leads to optimal compensation performance has also been proposed.

The performance of long period fiber grating (LPFG) sensors written in single cladding and double cladding fibers have been compared by using a fast responding interrogation system based on intensity modulation. Temperature and dynamic strain monitoring using this system have been demonstrated. This system is capable of resolving strain to 0.2 and 0.4 μe at a loading frequency of 20 Hz, and temperature resolution to 0.02 and 0.19 °C by using LPFG in the single cladding (SC-LPFG) and double cladding (DC-LPFG), respectively.