Linear crosstalk in 4×4 semiconductor optical amplifier gateswitch matrix

We report a comprehensive crosstalk investigation of a packaged InGaAsP/InP 4×4 semiconductor optical amplifier gate switch matrix, experimentally as well as theoretically. For a fully loaded switch with the same wavelength on all four inputs, all possible switching combinations are analyzed, thus yielding realistic crosstalk figures. Coherent and incoherent crosstalk phenomena are identified, and a switch crosstalk less than -40 dB has been measured     

Modulation characteristic of waveguide-type optical frequency combgenerator

We report the modulation characteristics of a waveguide-type optical frequency comb generator (WG-OFCG) with the advantages of compactness, high modulation index and low driving power. The characteristics of the optical frequency comb (OFC) generated when the modulation index exceeds 2π are discussed. The power of the modulation sidebands was measured by the optical heterodyne method with an external-cavity laser as a local oscillator. The dependence of the modulation index of the WG-OFCG on the modulation frequency up to 40 GHz was measured. The generation span of the OFC at the modulation frequency detuned from an integer multiple of the free spectral range (FSR) is discussed     

A new erasing method for a single-voltage long-endurance flashmemory

A new method to erase a standard (double-poly, stacked-gate NOR-type) flash cell is proposed. The method, still using the tunneling mechanism to extract electrons from the floating gate, is based on the concept of keeping the electric field constant during the whole erasing operation. The new method has two main advantages with respect to the conventional one: (1) it does not depend on the supply voltage variation and (2) it allows a better reliability in terms of endurance-induced stress. Results have shown that flash device performances are greatly improved in terms of stability and endurance reliability up to one million cycles     

Communication network protocol for real-time distributed controland its LSI implementation

A new token-passing mechanism, priority token passing, which features real-time access and fast detection and recovery of transmission errors, is discussed in detail in comparison with standard token-passing protocols, and its large-scale integration (LSI)-oriented design concept is described. Priority token passing includes only a small performance overhead, due to its switching functions, which can change network topology from ring to broadcast medium. A token-holding node passes the token to another node after determining the successor through priority comparison. Errors occurring during token passing can, thus, be detected and corrected simply and promptly. Priority token passing has a simple hardware implementation, requiring only small additions to the frame control circuitry, and has a small implementation overhead. The priority token-passing protocol and two other important network communication functions, dual ring network reconfiguration and high-level data link control (HDLC) normal response mode-based message transmission, are designed as a single finite-state machine, and implemented into a compact LSI chip. This integrated instrument network (IINET) chip provides complete network communication services and requires only three additional external electronic components for operation     

A novel method for elimination of line-current harmonics insingle-stage PFC switching regulators

This paper studies a particular single-stage power-factor-correction (PFC) switching regulator employing a discontinuous-conduction-mode (DCM) boost-input cell and a continuous-current-mode (CCM) forward output cell. Although this single-stage PFC regulator can provide a reasonably high power factor when its PFC stage is operating in discontinuous mode, substantial reduction in line-current harmonics is possible by applying a suitable frequency-modulation scheme. This paper derives a frequency-modulation scheme and proposes a practical implementation using a simple translinear analog circuit. A quantitative analysis on the total harmonic distortion (THD) of the line current when the circuit is subject to a limited range of frequency variations is presented along with some considerations for practical design. Experimental data obtained from a prototype confirms the effectiveness of the proposed frequency-modulation scheme. The proposed analog translinear circuit allows custom integrated circuit implementation, making it a viable low-cost solution to the elimination of line-current harmonics in switching regulators     

Performance of the PAC optical packet network

For multiuser packet communications with unpredictable user demands (e.g., in a local or metropolitan area network), coordination and control of access to the frequency-division multiplexing (FDM) channels are difficult. B. Glance (J. Lightwave Technol., vol.10, pp.1323-1328, Sep 1992) proposed using a simple protection-against-collision (PAC) circuit to solve this media access problem and achieve full optical connectivity. The PAC system has the potential to interconnect hundreds of ports, each transmitting at several gigabits per second. Performance aspects of the PAC optical packet network are discussed here. The delay-throughout performance of this network is analyzed for uniform traffic patterns. The results show that in geographically distributed applications the maximum achievable throughput (normalized to the transmission rate) is typically between 0.4 and 0.5 per channel. In a centralized switch the (normalized) maximum achievable throughput can approach 0.8 per channel     

Pseudo-Strong Regularity Around a Set

A generalization of strong regularity around a vertex subset C of a graph Γ, which makes sense even if Γis non-regular, is studied. Such a structure appears, together with a kind of distance-regularity around C , when an spectral bound concerning the so-called predistance polynomial of C is attained. As a main consequence of these results, it is shown that a regular (connected) graph Γwith d + 1 distinct eigenvalues is distance-regular, and its distance- d graph Γ d is strongly regular with parameters a = c , if and only if the number of vertices at distance d from each vertex satisfies an expression which depends only on the order of Γand the different eigenvalues of Γ.     

Analysis of intensity interference caused by cross-phase modulationin dispersive optical fibers

Under a set of broadly justified simplifying assumptions, an analytical approach to the problem of cross phase modulation in optical fibers is presented. Simple analytical expressions describing intensity interference caused by cross-phase modulation (XPM) are derived. It turns out that within a physically realizable range of parameters the power penalties induced by XPM have a linear dependence on the power of the interfering signal. Examples of specific systems are presented and discussed     

Far-infrared pump-probe measurement of the lifetime of the 2p−1 shallow donor level in n-GaAs

The low temperature lifetime of electrons excited in the 2p^?1 donor level of n-GaAs has been studied in a far-infrared pump-probe experiment. The measurement has been carried out using a pulsed far-infrared molecular gas laser working at a wavelength of 292µm, with the sample in a magnetic field of 5.1 T, resonant with the 1s_o?2p^?1 transition. Two FIR pulses are sliced from one FIR-laser pulse by means of optical switching techniques using two Q-switched Nd:YAG lasers. The first pulse is used to saturate the transition, while the second pulse probes the return of the population in the excited state towards thermal equilibrium as a function of the time delay after the excitation pulse. The value of 350±50 ns found for the lifetime falls in line with CW saturation results on materials with other doping concentrations.