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In this paper, four sliding mode control surfaces are designed to optimize the performance of the controller for switching power supplies. The influence of the on-resistance change in the switching power supply and the designed sliding function on the system settling time and stability is analyzed. This article takes the switching buck converter as an example to verify and compare the proposed sliding mode control surfaces.

This paper presents a self-healing fiber grating sensor system and demonstrates its effectiveness. The self-healing function is constructed by using a primary ring architecture incorporated with several ring sub-networks. To enhance the sensing signal when a breakpoint suddenly occurs in the network, we employ a fiber-ring laser-based sensor system. The network survivability of an 11-point FBG sensor is experimentally examined. The proposed fiber grating sensor system can increase the reliability of a sensing network. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 441–444, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10633

The propagation of a nonlinear ultrashort pulse in a photonic bandgap structure is investigated by using the finite-difference time-domain method. The simulation results show that an ultrashort pulse near the bandgap edge can propagate through a nonlinear fiber Bragg grating, even if the broadband spectrum of this ultrashort pulse overlaps the whole forbidden band of the grating. It is also shown that the time delay of such an ultrashort solitary wave is proportional to its detuning wavelength from the exact Bragg resonance.

We propose a novel fiber Bragg grating (FBG) sensor system using a linear-cavity fiber laser scheme with a distributed Raman amplifier as a gain medium. The inhomogeneous broadening property of the distributed Raman amplifier is used for multiwavelength operation. The experiment shows that such a linear-cavity fiber Raman laser can provide a stable output with an optical signal-to-noise ratio over 50 dB even if the FBG is located at a 25-km remote sensing position. The feature of our proposed fiber laser can facilitate a long-distance or a large-scale fiber sensor system and can be easily extended for multipoint sensing applications.

We propose an intensity and wavelength-division multiplexing (IWDM) fiber Bragg grating (FBG) sensor system using a tunable multiport fiber ring laser. The different output powers of a multiport fiber laser are used to address the information reflected from the sensing FBGs, even if the Bragg wavelengths of the FBGs connected at different laser output ports are identical. We describe the operation principle and experimentally demonstrate a three-port fiber sensor. For the IWDM technique, our proposed fiber grating sensor system can enhance the sensing capacity, signal-to-noise ratio, and sensing resolution.

In this letter, we present a hybrid star-ring architecture for a highly reliable fiber Bragg grating (FBG) sensor system and demonstrate its effectiveness. The main trunk of the proposed sensor network is star topology and the sensing branches comprise a series of concatenated ring subnets. The weakness in reliability of the star network is overcome by the ring subnets with a self-healing function based on the reconfigurable optical switches between each subnet. To enhance the signal-to-noise ratio (SNR) of the sensor system, we adopt a linear-cavity FBG laser scheme to construct our proposed hybrid star-ring architecture. Such a fiber-laser scheme results in the SNR over 48 dB for the sensor network. The network survivability of a ten-point FBG sensor is experimentally examined. It is shown that the proposed FBG sensor system can increase the reliability of a sensing network.

A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode (FP-LD) is proposed and demonstrated. By adding an FP-LD incorporated with a tunable bandpass filter within the ring cavity, the fiber laser can lase two wavelengths simultaneously because of the self-seeded mechanism. This dual-wavelength output exhibits a good performance having the optical side-mode suppression ratio over 31 dB. The wavelength-tuning range of this tunable dual-wavelength fiber laser can be up to 9 nm.

A simple fiber-Bragg-grating (FBG) sensor system based on a linear-cavity fiber laser is proposed and experimentally demonstrated. The lasing wavelength shift resulting from the temperature variation on this sensing element is discriminated by two FBGs. These two FBGs, acting as wavelength discriminators, are used to increase the real-time measurement range for monitoring the temperature variation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 15–17, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10810

We present a novel fiber-laser-based sensor network with self-healing function and demonstrate its effectiveness. The network survivability and capacity for a multipoint sensor system are enhanced by adding switches in a self-healing ring architecture. The fiber laser adopted in this system is a linear-cavity fiber Bragg grating (FBG) laser leading to the signal-to-noise ratio over 52 dB for the sensor network. The network survivability of a ten-point FBG sensor is experimentally examined. The experimental results show that the proposed system can facilitate reliable sensing networks for a large-scale and multipoint smart structure.

A high-resolution fiber Bragg grating (FBG) sensor sys- tem using a linear-cavity fiber laser scheme is proposed and numerically studied. The proposed sensor system can improve the sensing accuracy by using a discriminating FBG pair in conjunction with a fiber laser scheme. This FBG sensor system can resolve the temperature up to 0.0005°C theoretically and can be applied for strain sensing and tem- perature sensing with high precision. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 323-325, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop. 10450

We present a technique for accurate size and distribution measurements of micro-particles based on angular and spectral resolved far field scattering patterns combined with coherent backscattering characterization. This technique is potentially suitable for biosensing applications.

This paper presents the analytic solutions of self-induced transparency with transverse variations in resonant media by a self-consistent power series approximation method. We solve the Maxwell-Bloch equations by retaining all integral terms from the inhomogeneous broadening and the second-derivative terms with respect to distance and time. The lowest-order approximation is presented in detail. We discuss the characteristics of the distortionless pulses that propagate in an inhomogeneously broadening medium. It is shown that the group velocity and peak power of the self-induced transparency solitons could be represented in terms of the pulse width, the angle between phase velocity and group velocity, and the basic material parameters of the resonant medium. The chirping of the soliton is also discussed.

We theoretically show that a self-induced transparency (SIT) soliton and a Bragg soliton can coexist in a nonlinear photonic band gap (PBG) medium doped uniformly with inhomogeneous-broadening two-level atoms. The Maxwell-Bloch equations for the pulse propagating through such a uniformly doped PBG structure are derived first and further reduced to an effective nonlinear Schr\"odinger equation. This model describes an equivalent physical mechanism for a Bragg-soliton propagation resulting from the effective quadratic dispersion balancing with the effective third-order nonlinearity. Because the resonant atoms are taken into account, the original band gap can be shifted both by the dopants and the instantaneous nonlinearity response originating from an intense optical pulse. As a result, even if a SIT soliton with its central frequency deep inside the original forbidden band, it still can propagate through the resonant PBG medium as long as this SIT soliton satisfies the effective Bragg-soliton propagation. An approximate soliton solution describing such coexistence is found. We also show that the pulse width and group velocity of this soliton solution can be uniquely determined for given material parameters, atomic transition frequency, and input central frequency of the soliton. The numerical examples of the SIT soliton in a one-dimensional ${\mathrm{As}}_{2}{\mathrm{S}}_{3}$-based PBG structure doped uniformly with Lorentzian line-shape resonant atoms are shown. It is found that a SIT soliton with \ensuremath{\sim}100-ps width in such a resonant PBG structure can travel with the velocity being two orders of magnitude slower than the light speed in an unprocessed host medium.

This paper presents the analyzed results of damping improvement of common-mode torsional oscillations of a power system containing series-capacitor compensation using a superconducting magnetic energy storage (SMES) unit. The studied power system consists of two sets of nonidentical turbine-generators connected to an infinite bus through a common series-capacitor compensated line. A unified approach based on modal control theory is employed to design a proportional-integral-derivative (PID) damping controller using speed deviations of both generators as stabilizing signals. A frequency-domain approach based on eigenvalue analyses and a time-domain approach based on nonlinear model simulations under disturbance conditions are both performed. It can be concluded from the simulated results that the proposed SMES can effectively stabilize common-mode torsional oscillations.

We numerically study the characteristics of a nonlinear pulse that propagates through a one-dimensional photonic bandgap (PBG) structure uniformly doped with two-level atoms. The numerical model adopted is the coupled system of nonlinear coupled-mode equations and atomic Bloch equations. The simulation results show that a self-induced transparency (SIT) soliton and a gap soliton can coexist in a nonlinear PBG structure uniformly doped with resonant atoms. Although this mixed state, known as a SIT-gap soliton, near the PBG edge has been theoretically predicted, we numerically show that such a solitary wave still exists even if its central frequency is located deep inside the PBG. The propagating characteristics of the SIT-gap soliton are also discussed.