Single-Stage Grid-Connected Forward Microinverter with Boundary Mode Control

This paper presents a microinverter to be integrated into a solar module. The proposed solution combines a forward converter and a constant off-time boundary mode control, providing MPPT capability and unity power factor in a single-stage converter. The transformer structure of the power stage remains as in the classical DC-DC forward converter. Transformer primary windings are utilized for power transfer or demagnetization depending on the grid semi-cycle. Furthermore, bidirectional switches are used on the secondary side allowing direct connection of the inverter to the grid. Design considerations for the proposed solution are provided, regarding the inductance value, transformer turns ratio and frequency variation during a line semi-cycle. The decoupling of the twice the line frequency power pulsation is also discussed, as well as the maximum power point tracking (MPPT) capability. Simulation and experimental results for a 100W prototype are enclosed

Bandlimited Airy Pulses for Invariant Propagation in Single-Mode Fibers

By spectral analysis, and using joint time-frequency representations, we present the theoretical basis to design invariant bandlimited Airy pulses with an arbitrary degree of robustness and an arbitrary range of single-mode fiber chromatic dispersion. The numerically simulated examples confirm the theoretically predicted pulse partial invariance in the propagation of the pulse in the fiber.

Pulse shortening of gain switched single mode semiconductor lasers using a variable delay interferometer

We propose a pulse shaping and shortening technique for pulses generated from gain switched single mode semiconductor lasers, based on a Mach Zehnder interferometer with variable delay. The spectral and temporal characteristics of the pulses obtained with the proposed technique are investigated with numerical simulations. Experiments are performed with a Distributed Feedback laser and a Vertical Cavity Surface Emitting Laser, emitting at 1.5 µm, obtaining pulse duration reduction of 25-30%. The main asset of the proposed technique is that it can be applied to different devices and pulses, taking advantage of the flexibility of the gain switching technique.

Control of gating mode by a single amino acid residue in transmembrane segment IS3 of the N-type Ca2+ channel

N-type Ca2+ channels can be inhibited by neurotransmitter-induced release of G protein βγ subunits. Two isoforms of Cav2.2 α1 subunits of N-type calcium channels from rat brain (Cav2.2a and Cav2.2b; initially termed rbB-I and rbB-II) have different functional properties. Unmodulated Cav2.2b channels are in an easily activated “willing” (W) state with fast activation kinetics and no prepulse facilitation. Activating G proteins shifts Cav2.2b channels to a difficult to activate “reluctant” (R) state with slow activation kinetics; they can be returned to the W state by strong depolarization resulting in prepulse facilitation. This contrasts with Cav2.2a channels, which are tonically in the R state and exhibit strong prepulse facilitation. Activating or inhibiting G proteins has no effect. Thus, the R state of Cav2.2a and its reversal by prepulse facilitation are intrinsic to the channel and independent of G protein modulation. Mutating G177 in segment IS3 of Cav2.2b to E as in Cav2.2a converts Cav2.2b tonically to the R state, insensitive to further G protein modulation. The converse substitution in Cav2.2a, E177G, converts it to the W state and restores G protein modulation. We propose that negatively charged E177 in IS3 interacts with a positive charge in the IS4 voltage sensor when the channel is closed and produces the R state of Cav2.2a by a voltage sensor-trapping mechanism. G protein βγ subunits may produce reluctant channels by a similar molecular mechanism.

Energy level statistics for models of coupled single-mode Bose-Einstein condensates

We study the distribution of energy level spacings in two models describing coupled single-mode Bose-Einstein condensates. Both models have a fixed number of degrees of freedom, which is small compared to the number of interaction parameters, and is independent of the dimensionality of the Hilbert space. We find that the distribution follows a universal Poisson form independent of the choice of coupling parameters, which is indicative of the integrability of both models. These results complement those for integrable lattice models where the number of degrees of freedom increases with increasing dimensionality of the Hilbert space. Finally, we also show that for one model the inclusion of an additional interaction which breaks the integrability leads to a non-Poisson distribution.

All-Raman amplified transmission at 40 Gbit/s in standard single mode fibre

We investigate a 40 Gbit/s all-Raman amplified standard single mode fibre (SMF) transmission system with the mid-range amplifier spacing of 80-90 km. The impact of span configuration on double Rayleigh back scattering (DRBS) was studied. Four different span configurations were compared experimentally. A transmission distance of 1666 km in SMF has been achieved without forward error correcting (FEC) for the first time. The results demonstrate that the detrimental effects associated with high pump power Raman amplification in standard fibre can be minimised by dispersion map optimisation. © 2003 IEEE.

Strain and temperature sensitivity of a single mode polymer optical fiber

We have measured the optical phase sensitivity of fiber based on poly(methyl methacrylate) under near-single-mode conditions at 632.8 nm wavelength. The elongation sensitivity is 131±3×105 rad m-1 and the temperature sensitivity is -212±26 rad m-1 K-1. These values are somewhat larger than those for silica fiber and are consistent with the values expected on the basis of the bulk polymer properties.

Continuous-wave ultraviolet light induced fiber Bragg gratings in few- and single-mode microstructured polymer optical fibers

Reported are observations and measurements of the inscription of fibre Bragg gratings in two different types of microstructured polymer optical fibre: few-moded and endlessly single mode. Contrary to FBG inscription in silica microstructured fibre, where high energy laser pulses are a prerequisite, we have successfully used a low power CW laser source operating at 325nm to produce 1-cm long gratings with a reflection peak at 1570 nm. Peak reflectivities of more than 10% have been observed.

870nm Bragg grating in single mode TOPAS microstructured polymer optical fibre

We report the fabrication and characterization of a fiber Bragg grating (FBG) with 870 nm resonance wavelength in a single-mode TOPAS microstructured polymer optical fiber (mPOF). The grating has been UV-written with the phasemask technique using a 325 nm HeCd laser. The static tensile strain sensitivity has been measured as 0.64 pm/µstrain, and the temperature sensitivity was -60 pm/°C. This is the first 870nm FBG and the first demonstration of a negative temperature response for the TOPAS FBG, for which earlier results have indicated a positive temperature response. The relatively low material loss of the fiber at this wavelength compared to that at longer wavelengths will considerably enhance the potential utility of the TOPAS FBG.

Band-limited airy pulses for invariant propagation in single mode fibers

By spectral analysis, and using joint time-frequency representations, we present the theoretical basis to design invariant band-limited Airy pulses with an arbitrary degree of robustness, and an arbitrary range of single mode fiber chromatic dispersion. The numerically simulated examples confirm the theoretically predicted pulse partial invariance in the propagation of the pulse in the fiber.

PMD tolerance of 288 Gbit/s Coherent WDM and transmission over unrepeatered 124 km of field-installed single mode optical fiber

Low-cost, high-capacity optical transmission systems are required for metropolitan area networks. Direct-detected multi-carrier systems are attractive candidates, but polarization mode dispersion (PMD) is one of the major impairments that limits their performance. In this paper, we report the first experimental analysis of the PMD tolerance of a 288Gbit/s NRZ-OOK Coherent Wavelength Division Multiplexing system. The results show that this impairment is determined primarily by the subcarrier baud rate. We confirm the robustness of the system to PMD by demonstrating error-free performance over an unrepeatered 124km field-installed single-mode fiber with a negligible penalty of 0.3dB compared to the back-to-back measurements. (C) 2010 Optical Society of America

Full-field electronic dispersion compensation of a 10 Gbit/s OOK signal over 4 x 124 km field-installed single-mode fibre

We experimentally demonstrate the use of full-field electronic dispersion compensation (EDC) to achieve a bit error rate of 5 x 10(-5) at 22.3 dB optical signal-to-noise ratio for single-channel 10 Gbit/s on-off keyed signal after transmission over 496 km field-installed single-mode fibre with an amplifier spacing of 124 km. This performance is achieved by designing the EDC so as to avoid electronic amplification of the noise content of the signal during full-field reconstruction. We also investigate the tolerance of the system to key signal processing parameters, and numerically demonstrate that single-channel 2160 km single mode fibre transmission without in-line optical dispersion compensation can be achieved using this technique with 80 km amplifier spacing and optimized system parameters.

All-fiber normal-dispersion single-polarization passively mode-locked laser based on a 45°-tilted fiber grating

An all-fiber normal-dispersion Yb-doped fiber laser with 45- tilted fiber grating (TFG) isto the best of our knowledgeexperimentally demonstrated for the first time. Stable linearly-chirped pulses with the duration of 4 ps and the bandwidth of 9 nm can be directly generated from the laser cavity. By employing the 45 TFG with the polarization-dependent loss of 33 dBoutput pulses with high polarization extinction ratio of 26 dB are implemented in the experiment. Our result shows that the 45 TFG can work effectively as a polarizerwhich could be exploited to singlepolarization all-fiber lasers.

Microchannels in conventional single-mode fibers

Microchannels are fabricated into conventional single-mode fibers by femtosecond laser processing and chemical etching. Fabrication limitations imposed by the fiber geometry are highlighted and resolved through a simple technique without compromising fabrication flexibility. A microfluidic fiber device consisting of a 4 μm wide microchannel that intersects the fiber core for refractive index sensing is further demonstrated. © 2006 Optical Society of America.

All-fiber normal-dispersion single-polarization passively mode-locked laser based on a 45°-tilted fiber grating

An all-fiber normal-dispersion Yb-doped fiber laser with 45- tilted fiber grating (TFG) isto the best of our knowledgeexperimentally demonstrated for the first time. Stable linearly-chirped pulses with the duration of 4 ps and the bandwidth of 9 nm can be directly generated from the laser cavity. By employing the 45 TFG with the polarization-dependent loss of 33 dBoutput pulses with high polarization extinction ratio of 26 dB are implemented in the experiment. Our result shows that the 45 TFG can work effectively as a polarizerwhich could be exploited to singlepolarization all-fiber lasers.