A multiplexed gas sensing network based on hollow-core photonic crystal fiber (HC-PCF) and active intra-cavity absorption spectrometry is designed and demonstrated experimentally. Sensing channels are extended to eight by using hybrid dense wavelength division multiplexing (DWDM) and time division multiplexing (TDM). What’s more, wavelength scanning technique combined with voltage gradient method are adopted in the designed sensing network, which improves the sensing efficiency at least five times when comparing with the whole scan. In experiment, by recording and analyzing the laser output intensity at acetylene absorption peaks of 1528.01 nm and 1530.37 nm, the minimum detection limit (MDL) of 30.16 ppmv and 26.28 ppmv are achieved, respectively. Therefore, the designed gas sensing network can realize detection of low-concentration gas with high capacity and efficiency.
We propose an ultra-wide detection range refractive index sensor based on surface plasmon resonance (SPR) with photonic crystal fiber (PCF). The analyte is injected into the central air hole of fiber core. The properties of refractive index sensing are investigated. Simulation results show that the proposed sensor has an ultra-wide detection range from 1.29 to 1.49. The refractive index wavelength sensitivities of x-polarized and y-polarized core mode are -4156.82 nm/RIU and -3703.64 nm/RIU respectively, and the linear fitting degrees are 0.99598 and 0.99236, respectively. The maximum x-pol amplitude sensitivity is -456.589RIU-1 . The maximum y-pol amplitude sensitivity is -1056.33RIU-1 . The designed refractive index sensor has a great potential in the fields of biology, chemistry, environment and medicine.
A localized surface plasmon resonance (LSPR) temperature sensor based on photonic crystal fiber (PCF) filled with liquid and silver nanowires is demonstrated both theoretically and experimentally. Simulation results show that a blueshift is appeared along with temperature increasing. The resonance wavelength and resonance intensity can be tuned effectively by adjusting the volume ratios of the liquid constituents. To investigate the sensor’s performance, a large temperature range from 25°C to 60°C is detected in experiment and the sensitivity of -2.08 nm/°C with figure of merit (FOM) 0.1572 is obtained. The all-fiber device with strong mechanical stability is easy to realize remote sensing by changing the downlead fiber length, also promising for developing a high sensitive, real-time and distribute fiber sensor in temperature sensing applications.
We propose a sensitivity-enhanced intracavity-absorption gas sensor based on the phenomenon of mode competition in the dual-wavelength ring fiber laser. The laser configuration possesses the sensing and reference wavelengths as 1530.372 nm and 1532.168 nm, respectively. When the hollow-core photonic crystal fiber (HC-PCF) is filled with 1000-ppmv acetylene, a sudden change on absorption intensity of more than 30 dB can be achieved by adjusting the optical loss in the laser cavities, resulting from the mode competition between the sensing and reference wavelengths. The minimum detectable acetylene concentration (MDAC) of 29.53 ppmv is obtained in experiment, one order of magnitude higher than former works.
A tunable single polarization filter based on high-birefringence photonic crystal fiber with silver wires symmetrically filled into cladding air holes is designed. The confinement loss of the unwanted polarized mode (x-polarized mode) at 1310- and 1550-nm bands are 371 and 252 dB/cm, whereas another mode confinement loss (y-polarized mode) at the corresponding wavelength as low as 14 and 10 dB/cm, respectively. Moreover, the 20-dB bandwidth can reach 179 (at the 1310-nm band) and 71 nm (at the 1550-nm band) for a propagation distance of 1 mm. The dispersion relations and polarization characteristics are analyzed in detail utilizing the finite element method. Numerical results show that by adjusting the pitch between two adjacent air holes, the diameters of cladding air holes or silver wires near the fiber core, the resonance wavelength and resonance strength can be tuned effectively, which is beneficial for tunable polarization filter devices in the communication wave bands.
We demonstrate an automatic channel-switched intracavity- absorption acetylene sensor via Sagnac loop filter based on the mode-competition in a ring fiber laser. When the photonic crystal fiber gas cell is filled with 1% acetylene, the corresponding absorption intensity can be ~14.0 dB and ~7.2 dB at 1532.83 nm and 1534.01 nm, respectively. Compared with the single transmission pass method, the sensitivity can be improved up to more than 10 times. It spends 50 seconds in scanning the absorption spectra through applying gradient voltage to the tunable F-P filter.
A numerical study of a surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) filled with core-shell Ag-Au nanocomposite materials for measurement of refractive index of the analyte is presented. Considering the design flexibility and improved optical properties of the core-shell bimetallic nanocomposite materials, the proposed sensor is demonstrated to achieve high spectral sensitivity, high detection accuracy, and sensing spectra tuning ability. Meanwhile, the existence of the gold shell can protect the silver core from oxidation, which means high system stability and long lifetime. Based on numerical simulations, the influences of structural parameters of the sensor on sensing properties are discussed. Furthermore, the parameters are optimized by analyzing the simulation results to achieve better performance. It is observed that a high average spectral sensitivity of 5940 nm/RIU with the resolution of 1.68×10−5 RIU in the sensing range of 1.33 to 1.38 can be achieved.
We demonstrate a temperature sensor based on surface plasmon resonances supported by a six-hole microstructured optical fiber (MOF). The air holes of the MOF are coated with a silver layer and filled with a large thermo-optic coefficient liquid mixture (ethanol and chloroform). The use of all six fiber holes and their relatively large size should facilitate the coating of the silver and the filling of the liquid mixture. Temperature variations will induce changes of coupling efficiencies between the core-guided mode and the plasmonic mode, thus leading to different loss spectra that will be recorded. The refractive index of the liquid mixture is close to that of the MOF material, which will enhance the coupling efficiency and the sensitivity. Our numerical results indicate that temperature sensitivity as high as 5.6 nm/K can be achieved and that the most sensitive range of the sensor can be tuned by changing the volume ratios of ethanol and chloroform.
An analysis of highly birefringence low losss index-guiding phptonic crystal fiber composed of different
sized circular air-holes in cladding and adjacent to the two ellipital air-holes x-diraction in the first inner rings is
carried out in this work using voul fector finite element method.The birefringence properities in terms of various
parameters,e.g,pitch length,air-hole size and ellipticity ratio are calculated.Form the numerical results confirm that
the size control of these air holes and pitch length is the key to reaching high model birefringnce.The proposed
struture at wavelength 1.55μm shows a birefringence of up to 3.02x10-2 and at the same time can get the
confinement loss of less than 1.9x10-7dB/m, which is a reference significance in useful to dessign temperature
sensors.
A subwavelength core microstructured optical fiber (MOF) temperature sensor based on infiltration with chloroform is
proposed. Fiber core is surrounded by three large holes which can facilitate the infiltration of the chloroform. The
refractive index of chloroform is sensitive to the temperature of the environment. Mode loss of the guided mode caused
by index change of chloroform is obtained by solving Maxwell’s equation with finite element method (FEM), and is
used as a criterion for sensitivity estimation. The relationship between the sensitivity of temperature sensor and the core
diameter of MOF is investigated. Our simulation results show that the subwavelength core MOF is very promising for
developing a linear response to temperature sensor of significantly reduced core size.
A study of polymer photonic crystal fiber (PCF) sensor coated with smart composite materials for measurements of refractive index of analyte is presented in this paper. The proposed sensor combines the characteristics of polymer PCF and composite material, which can make the confinement loss lower than the silica PCF duo to the double interaction of the polymer and silver film. The results obtained in this study demonstrate that polymer PCF sensors coated with composite material and with the polymer PCF’s advantages, the sensor’s feasibility can be improved further and it can be applied in a broad field, especially in biosensing platforms.
KEYWORDS: Gas sensors, Photonic crystal fibers, Finite element methods, Signal attenuation, Sensors, Absorption, Refractive index, Optoelectronics, Information technology, Optical fibers
A hollow-core photonic crystal fiber (HC-PCF)-based gas sensor is proposed and numerically investigated through the finite element method. To obtain higher relative sensitivity coefficient γ and the better sensing properties of the gas sensor, the floriated structure of the central hole of HC-PCF is optimized. Numerical investigation shows that γ is high and relatively stable to changes of the diameter of air holes in a wide range of wavelength of 1.5-1.7μm, which is very beneficial for sensor fabrication. A lower confinement loss and the flatness are also exhibited with the HC-PCF. And the highest γ of 0.9998 of the floriated structure of the central hole can be obtained than the circular ones of 0.9435 at the wavelength of 1.56μm.
We propose and numerically characterize a design for a photonic crystal fiber based surface plasmonic resonance sensor for an aqueous environment. The coupling properties of the plasmonic modes and core-guided mode are investigated comprehensively by the finite element method. The sensor consists of selectively filled with silver nanowires analyte channels, which enhance the phase matching between the core-guided mode and plasmonic mode. Compared with the entirely filled structure, the selectively filled sensor design demonstrates lower transmission loss and better sensitivity, which is 2800nm/RIU (refractive index unit). Moreover, the resonance wavelength has an increase with the analyte index increase, and the increasing trend of wavelength separation with index change is linear.
We propose a novel surface plasmon resonance sensor design based on a grapefruit photonic crystal fiber. In such a
sensor, phase matching between plasmon and a core mode is achieved by introducing microstructure into the fiber core.
Using the finite element method, the confinement loss of the fiber is calculated to measure the sensitivity of the sensor.
Simulation results show that this kind of sensor has an excellent effect, with the amplitude resolution to be as low as
2.88×10-5 RIU and the spectral resolution to be 6.67 ×10-5 RIU.
We propose a novel surface plasmon resonance sensor design based on a grapefruit photonic crystal fiber. In such a
sensor, phase matching between plasmon and a core mode is achieved by introducing microstructure into the fiber core.
Using the finite element method, the confinement loss of the fiber is calculated to measure the sensitivity of the sensor.
Simulation results show that this kind of sensor has an excellent effect, with the amplitude resolution to be as low as
2.88×10−5 RIU and the spectral resolution to be 6.67 ×10−5 RIU.
Using the finite element method to simulate THz photonic crystal fiber(PCF)transmission and sensing characteristics.
According to solid TPCF guidance, the refractive index, attenuation and relativity sensitivity were analyzed. And we
analyzed firstly the transformation of PCF hole-shape to the influence of sensing on THz wave region. Then we simulate
and calculate THz high density polyethylene PCF(HDPE-PCF) some parameters, at last the design considerations were given.
Optical fiber sensors (OFS) play an important role in modern intellectualized sensing system. A novel optical fiber sensor based on single mode fiber laser is proposed in this paper. The basic elements of the novel fiber laser sensor (FLS) is based in the fact that the output power of fiber laser is influenced by the loss which caused by the absorption loss of analyte in evanescent field of the fiber. The action of the fiber laser sensor is theoretical investigated using two-level system rate equations. The function which contacted the output power of the fiber laser and the absorption loss of analyte is build upon the complex refraction index of the analyte and the loss of the resonant cavity of the fiber laser though evanescent field. The relative sensitivity of the fiber laser sensor is given finally.
Multicast services have been increasingly used by many multimedia applications. As one of the key techniques to support multimedia applications, the rational and effective multicast routing algorithms are very important to networks performance. When switch nodes in networks have different multicast capability, multicast routing problem is modeled as the degree-constrained Steiner problem. We presented a genetic algorithm, named DCGA, for the degree-constrained
case in multimedia communications. The algorithm is used to generate degree-constrained multicast trees with bandwidth and end to end delay bound. Simulations over random networks were carried out to compare the performance of the proposed algorithm. Experimental results show that DCGA has better ability in balance load among the nodes in networks, and has capability of finding unsaturated links and (or) unsaturated nodes to generate multicast trees than BMSTA. Moreover, the proposed algorithm can generate multicast tree with lower cost in any networks and can also achieve optimal multicast tree rapidly with the smaller group size.
We present a theoretical study of optical bistability and differential amplification, arising as a consequence of the nonlinear Kerr effect in mutually coupled nonlinear microcavity resonators. The dependence of the bistability and differential amplification on various parameters of the coupling range and the resonators is investigated. Multiple closely spaced bistability of the internal intensity in the microresonator is found with appropriate parameters. The results may be useful for a complex logic, memory or switch operation system.
We present a theoretical study of a double microcavity resonators system with absorption or gain. The output intensity and the power intensity inside the microresonator are derived. Some interesting features and their possible application are discussed. The results may be useful for modulator, amplifier, laser and sensor.
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