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This paper presents mercury (II) ions detection based on long period fiber grating (LPFG) sensor written on a single mode optical fiber by electrical arc induced technique that is suitable to be used for long term monitoring purpose. In the work, the LPFG was coated with both polyelectrolyte (PE) layers to enhance its sensitivity as well as a layer of gold nanoparticles (AuNP) for reaction to the mercury (II) ions. Experiments were conducted using double-pass configurations with mercury (II) ions concentrations varied between 0.5 ppm to 10 ppm. The results showed that the resonance wavelength of the PE–AuNP coated LPFG notch shifted to the longer wavelength, with a total shift of 1.34 nm and transmission power increment of 1.74 dBm over a period of 5 h. The results were then compared with uncoated as well as PE-only coated LPFGs, where no significant changes in resonance wavelength and transmission power were observed for these LPFGs. A novel PE–AuNP coated LPFG sensor that is suitable to be used for in-situ, long term and remote monitoring has been successfully demonstrated and tested for the detection of mercury (II) ions in water.

This is a study on double-pass intensity-based hybrid Long Period Fiber Grating (LPFG)and Fiber Bragg Grating (FBG) sensor configuration where a fiber sensor network was constructed with multiple sensing capability. The sensing principle is based on interrogation of intensity changes of the reflected signal from an FBG caused by the LPFG spectral response to the surrounding perturbations. The sensor network developed was tested in monitoring diesel adulteration of up to a distance of 8 km. Kerosene concentration from 0% to 50% was added as adulterant into diesel. The sensitivity of the double-pass hybrid LPFG-FBG sensor over multiple points was>0.21 dB/% (for adulteration range of 0–30%) and >0.45 dB/% from 30% to 50% adulteration. It is found that the sensitivity can drop up to 35% when the fiber length increased from 0 km to 8 km (for the case of adulteration of 0–30%). With the multiple sensing capabilities, normalized FBG's reflected power can be demodulated at the same time for comparison of sensitivity performance across various fiber sensors.

This paper presents a systematic review on the long-period fiber grating (LPFG) formed by the electric arcing method. The basic concept of LPFG and the background of the electric arcing method are thoroughly discussed. The paper also discussed on the methods to improve the sensitivity of LPFG towards external perturbations. The LPFG has been reported to have potential usage as sensor, thus a section of the paper has focused on some application of arc-induced LPFG as sensors.

We demonstrated a method to enhance the sensitivity of a hybrid arc-induced Long Period Fiber Grating (LPFG)–Fiber Bragg Grating (FBG) system using a double-pass configuration for refractive index (RI) sensing. The sensing principle is based on the interrogation of the reflected signal variation of an FBG caused by the shifting of the LPFG's resonant wavelength by changes in the surrounding medium. Standard oil with RI values ranging from 1.39 to 1.49 was used to monitor the RI response of the sensor in single-pass and double-pass configurations. Comparison of both configurations showed that the double-pass configuration utilizing an optimize-coupled LPFG has a sensitivity of 870.6 dB/RIU as compared to the single-pass configuration which has a sensitivity of 457.3 dB/RIU in the index range of 1.43–1.46.

This paper presents the detection of mercury (II) ions based on a novel hybrid Long Period Fiber Grating (LPFG)-Diffusive Gradient in Thin Films (DGT) sensor system. The fundamental design of the hybrid sensor combines the features of a gold nanoparticles-coated LPFG embedded within a DGT structure. The main function of the DGT structure is to overcome the weakness of LPFG sensor by providing a durable housing for the protection of the fiber sensor, thereby allowing near real-time, in situ as well as long-term monitoring of mercury (II) ions in water. Experiments were conducted with mercury (II) solutions with concentrations ranging from 0.5 ppm to 10.0 ppm in order to study the sensing ability of the hybrid sensor. The performance of this hybrid sensor was then compared with an open structure sensor, in which the membrane filter and gel layers of DGT device were not included. Results showed that the response rate of the hybrid structure was lower than the open structure, i.e., 0.0049- and 0.0078-a.u./min, respectively in 2.0 ppm mercury (II) solution. This has proven that the presence of the structure of DGT has prolonged the movement of the mercury (II) ions towards the innermost Polyelectrolyte-Gold nanoparticles (PE-AuNP) coated LPFG sensor. Furthermore, the brittle LPFG sensor was well protected by the DGT structure. This mechanism makes the proposed LPFG-DGT sensor system suitable to be used for long-term and near real-time monitoring of water bodies due to the prolonged lifespan.

OPTICA APPLICATA; 03/2017; ISSN 1429-7507

Heavy metal contaminant in the water aquifers is an environmental threat. In present study, by utilizing a broadband supercontinuum (SC) laser source, detection of the contaminants is achieved through emission of broad spectrum of lights. By measuring the amount of light transmitted through the water sample, the presence of heavy metal contaminants is thus determined. A statistical analysis is conducted to analyze the performance of water contaminants detection. Interactive effects between three independent factors namely wavelength of the SC source, concentration of the heavy metal contaminants and input power are examined. Optimal operational conditions are obtained along with longer wavelength, lesser concentration of contaminants and lower power source. Under these conditions, high detection rate could be achieved with a transmittance value at 0.751.

Common mode current induced on cable attached to a PCB has been a well-known source of unintentional radiated emissions. The coupling mechanism of the common mode current to the cable can be divided into two types: voltage-driven and current-driven. In voltage-driven mechanism, the common mode current is induced by electric fleld that couples from traces on PCB to the cable. Previous work showed that these radiated emissions can be estimate based on the self-capacitance of the trace and the signal return plane but the method is only reasonably accurate at lower frequency. This paper develops a model which gives an extended frequency range up to 800MHz. The formulation for the equivalent common-mode voltage source is improved by taking into account the driving point impedance of the cable which behaves as a wire antenna. The radiated emissions estimated by the improved model match well with the values from 3D electromagnetic simulation of the original PCB with attached cable. It represents an improvement compared to earlier model by 11dB at 400MHz to 16dB at 700MHz for board size of 10cm £ 16cm and cable length of 3m. Similar improvements are obtained for other combinations of board size and cable length. The results show that the cable length is an important factor, in addition to the board area as suggested by earlier work, in determining the magnitude of the equivalent common-mode voltage source. Resonant of the wire antenna afiects not only the radiated electromagnetic fleld but also the common- mode voltage source magnitude due to varying antenna impedances.

We report a compact, all fiber, 150 ps picosecond fiber Master-Oscillator-Power-Amplifier (MOPA) that is capable of producing a maximum average output power of 2.16 W with peak power excessing 10 kW. The output from the MOPA is coupled into a PCF fiber, generating a broad continuum with spectrum bandwidth spanning from 600 nm to 1700nm.

This paper describes a fully packaged 4times4 optical crosspoint switch device with its core switch chip based on Bristol's unique active vertical coupler switching technology. Demonstration of several advanced switching functions using this device are described. These include on-chip header/label detection, optically addressed optical unicast switching, optical multicast switching, and packet-level dynamic power equalization. These experiments highlight the unique performance, versatility, and rich application potential of the switch matrix device

This paper investigates a novel optical multicast scheme without excess optical splitting loss to be realized using an active vertical coupler (AVC)-based optical switch matrix, due to the optical gain available in the AVC switch cells. Theoretical analysis and computer simulation have been carried out regarding the operational principle and switching characteristics of this scheme. Computer simulation further suggests that the amplified spontaneous emission (ASE)-limited scalability of the scheme can be as high as more than 40. Experiments using an existing 4 /spl times/ 4 switch-matrix device successfully demonstrated the predicted multicast switching operation. Measured switching characteristics and the optical signal-to-noise ratio (OSNR) values are in good agreement with simulation predictions. High switched-signal Q-factor values of 1-to-2 and 1-to-3 multicasting configurations indicate that the scale of the multicasting scheme can be further increased significantly.

Multiradio wireless mesh networks use mesh routers with multiple radio interfaces to improve network capacity. The attainable network capacity is dependent on how various channels (i.e., frequency bands) are assigned to each radio interface to form a mesh network with minimum interference. The channel assignment must fulfill the constraints that the number of channels assigned to a router is at most the number of interfaces on the router, and the resultant mesh network remains connected. This is a nondeterministic polynomial-time hard (NP-hard) problem. In this chapter, we investigate artificial immune algorithms that use greedy channel assignment to obtain feasible solutions, and use the clonal selection principle to improve the solutions. For practical considerations, small population size and small number of generations are used. By considering different mutation operators and clonal selection algorithms, several variants are evaluated. Through extensive simulations, we show that our proposal outperforms a genetic algorithm, a graph-theoretic algorithm, and a Tabu-based algorithm proposed for the same problem. In addition, the variant developed based on B-cell algorithm (BCA) and using a simple random-swapping mutation operator performs the best.

We report a novel detection technique for two types of common heavy metal contaminants in water, copper sulphate and ferric chloride, by analyzing the transmittance measurement of a supercontinuum laser source onto the samples.

This paper describes a 1.06μm all-fiber based pulsed laser source incorporating an agile Field Programmable Gate Array (FPGA) based driver board, which has the capabilities to generate pulses with arbitrary shapes and controllable bursts. Optical pulse durations tunable from picoseconds to nanoseconds, as well as pulse frequency adjustments from 1kHz to 1MHz can be achieved. An average optical power of 1W can be obtained from the amplified system with the output optical pulses optimized by reshaping the input pulses using this agile waveform tailoring method.

Dynamic per-packet output power equalization is demonstrated in a 4 /spl times/ 4 active vertical coupler-based optical crosspoint packet switch, achieving response time of

We demonstrate the use of an integrated 4 /spl times/ 4 InGaAsP-InP active vertical coupler optical crosspoint switch matrix to detect optical labels and to further switch variable length optical packets at rate of 10 Gb/s. Label detection sensitivity is assessed. Switched payload Q-factor and power penalty measurements have been carried out. Power penalty of less than 1.5 dB is found.

Multicasting packet-switching characteristics are achieved with an integrated 4/spl times/4 optical crosspoint switch matrix based on active vertical coupler switch cells. Q-factor analysis confirms the flexibility of such a device to perform different kinds of optical packet switching applications.

This paper describes our 1.06um pulsed laser source which has the capability to generate pulses with tunable durations from picoseconds to nanoseconds. This is made possible through the use of a high speed Field Programmable Gate Array (FPGA) board to generate the required pulses/ any arbitrary waveforms. The FPGA codes are specially designed to generate very fast rise/fall times waveforms with the flexibility to vary both the pulse duration and pulse frequency in real time. These custom defined waveforms are then used to generate high intensity laser pulses when connected to a 1064nm fiber laser source. These tunable pulsed laser sources have potential industrial applications in precision laser micro machining, where the high thermal intensity of the laser pulses can be used to perform ablation, cutting, drilling or annealing of processed materials. Furthermore, by able to tailor the shape of the delivered laser pulses, this will lead to reduction in processing time, improves the efficiency of material removal and the quality of the end product. Our custom board can generate arbitrary tailored pulses as short as 200ps and the longest pulse is 200ns. The pulse repetition rate can be tuned from 20 kHz to 1MHz.

An asymmetric tapered Long Period Fiber Grating (LPFG) was fabricated using an ignition coil based electric arcing fabrication system. The angle measurement of LPFG imaging using Matlab confirms the asymmetric tapered LPFG formation. Characterization of the asymmetric tapered Long Period Fiber Grating was done to test its sensitivity with respect to changes in the surrounding refractive index and temperature for LPFG at 900 nm to 1000 nm and 1500 nm to 1600 nm wavelength ranges. The fabricated asymmetric tapered LPFG performance is comparable with LPFG fabricated by fusion splicer but with less gratings and higher transmission loss.

The close correlation between the Gross Domestic Product (GDP) of a country and the availability of the broadband services has intensified the growth of the broadband access in all the continents in the world. This has put further pressure on the frequency spectrum available to support the rising demand. Optical fiber broadband technology which has the capacity to carry high volume of traffic at extremely high speed is the obvious choice to fulfill the demand. However its implementation cost and time have inhibited the widespread installation especially at the front end of the broadband access network. Wireless mesh network with its relatively short set up time and comparatively lower cost has been identified as a suitable technology to support the fiber backbone in providing front end connections to the mobile clients. The number of clients that can be served by the wireless segment of this hybrid communication system is inundated by spectrum limitation, unpredictable weather conditions, radio interferences and transmission power regulated by the authority. Many innovations have been used to extend the limited resources so as to maximise the number of mobile clients that can be supported by the wireless mesh network. This paper surveys the innovations with respect to radio channel, network topology, routing strategy and channel assignment that have been proposed to improve the performance of the wireless mesh network and suggest some areas for further work.

Mixed integer linear programs for minimum cost FiWi deployment and survivability of the resultant network under nodes failure are formulated and evaluated. Number of potential installation sites determines the network's feasibility and survivability.

Most simultaneous switching output noise (SSO) validation of high speed interfaces such as PCIe, SATA, USB, Core logic etc is approached on a case to case basis. It's not always clear when these interfaces are put in a common validation eco-system and stressed concurrently, what will be the functionality and performance limiter. This paper describes a new methodology that maximizes the power supply noise droop of each High Speed I/O interfaces; by implementing a concurrent test in exercising PCIe, SATA and USB to actively transmit data on all the lanes on the electrical board; and at the same time; exerting power gate/ungate noise onto the chip to serve as a natural aggressor from the core logic into the I/O interfaces. To make matter worst, a test package is designed to merge all of these high speed interfaces and core logic power rail as one common power rail on the package so that the injected and coupling noise were maximized. The on-die noise measurements were measured and results were compiled and conclude the findings of this new methodology.

This paper focuses on the power delivery network (PDN) characterization of high speed IC; particularly focusing on the on-chip capacitance (Cdie). Three packages were used to examine how Cdie would vary when selected power rails were merged on package. The first package carries isolated power rails where each and every power rails are separated. The second package combines IO power rails which were adjacent to each other, and the third package combined all common voltage power rails across the entire chip. The Cdie contributed from each I/O buffers as well as Core were measured and compared with the Cdie on the first package design; where all power rails were isolated. It was found that not 100% of the Cdie is visible when the power rails were merged. For example: the design allocated 100nF of Cdie in the silicon; however, only 66nF is measured on a merged-power-rail-package as oppose to 100nF Cdie is measured on the standard standalone-power-rail-package design. As much as 15% – 44% Cdie was found missing on a merged power rails compare to the original Cdie build in. This paper will describe a methodology to measure and characterize the Cdie, and propose a design guideline to suggest the best way to design a package to ensure that the Cdie is properly leveraged across when a power rail merger is implemented.

Dynamic output power equalisation for Next Generation Optical Access is demonstrated in an optical crosspoint switch, achieving response time of < 100 ns and output power levels within plusmn0.3dB for IPDR of 5 dB between consecutive optical bursts.

We experimentally demonstrate optical packet switching with less than 8 ns switching speed for a 10 Gb/s RZ payload and a 155 Mb/s NRZ label using a 4x4 optical crosspoint switch (OXS) matrix. The wavelength dependence of the OXS is also investigated in terms of the receiver sensitivity and the output OSNR. Very good switching performance can be achieved from 1535 nm to 1561 nm. Our results suggest that the OXS can be a promising device for switching future high speed impulse coded signals.

This paper describes a fully packaged 4x4 optical crosspoint switch (OXS) device and several of its application demonstrations. The core switch chip is based on Bristol’s unique active vertical coupler (AVC) switching technology. The 4x4 switch is pigtailed with 4-fibre lensed arrays using a Si V-groove technique. The packaged device is further interfaced via an electronic decoder/driver circuitry. Several novel experimental demonstrations are carried out, including optically addressed optical uni-cast routing, optical multicast routing, and packet level automatic gain control (AGC). These experiments highlight the unique performance and versatility of the AVC OXS device.

Dynamic per-packet output power equalisation is demonstrated in an optical crosspoint packet switch, achieving response time of

All optical multicast characterisation of an AVC based 4/spl times/4 optical switch matrix, which agreed with the modelling result, is reported. 10 Gb/s optical packet switching/multicasting operation in real time without optical split loss has been demonstrated.

Analysis of HTTP traffic through server logs is able to provide information about student behaviour to complement survey results for Web-based courses. A number of scripts were written to extract information from the logs, including hit counts and session counts. Different representations of summary results are shown. The captured user behaviour information is compared to student evaluation data, and the difference between the two sets of the data is discussed. Merits and limitations of this study are also discussed.