14,575 research outputs found
Triaxial digital fluxgate magnetometer for NASA applications explorer mission: Results of tests of critical elements
Tests performed to prove the critical elements of the triaxial digital fluxgate magnetometer design were described. A method for improving the linearity of the analog to digital converter portion of the instrument was studied in detail. A sawtooth waveform was added to the signal being measured before the A/D conversion, and averaging the digital readings over one cycle of the sawtooth. It was intended to reduce bit error nonlinearities present in the A/D converter which could be expected to be as much as 16 gamma if not reduced. No such nonlinearities were detected in the output of the instrument which included the feature designed to reduce these nonlinearities. However, a small scale nonlinearity of plus or minus 2 gamma with a 64 gamma repetition rate was observed in the unit tested. A design improvement intended to eliminate this small scale nonlinearity was examined
Wavelength conversion for WDM communication systems using four-wavemixing in semiconductor optical amplifiers
Four-wave mixing (FWM) in semiconductor optical amplifiers is an attractive mechanism for wavelength conversion in wavelength-division multiplexed (WDM) systems since it provides modulation format and bit rate transparency over wide tuning ranges. A series of systems experiments evaluating several aspects of the performance of these devices at bit rates of 2.5 and 10 Gb/s are presented. Included are single-channel conversion over 18 nm of shift at 10 Gb/s, multichannel conversion, and cascaded conversions. In addition time resolved spectral analysis of wavelength conversion is presented
Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of HF signals with microradian precision
Precision phase readout of optical beat note signals is one of the core
techniques required for intersatellite laser interferometry. Future space based
gravitational wave detectors like eLISA require such a readout over a wide
range of MHz frequencies, due to orbit induced Doppler shifts, with a precision
in the order of at frequencies between
and . In this paper, we present phase
readout systems, so-called phasemeters, that are able to achieve such
precisions and we discuss various means that have been employed to reduce noise
in the analogue circuit domain and during digitisation. We also discuss the
influence of some non-linear noise sources in the analogue domain of such
phasemeters. And finally, we present the performance that was achieved during
testing of the elegant breadboard model of the LISA phasemeter, that was
developed in the scope of an ESA technology development activity.Comment: submitted to Review of Scientific Instruments on April 30th 201
Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode
Chip-scale frequency comb generators have the potential to become key
building blocks of compact wavelength-division multiplexing (WDM) transceivers
in future metropolitan or campus-area networks. Among the various comb
generator concepts, quantum-dash (QD) mode-locked laser diodes (MLLD) stand out
as a particularly promising option, combining small footprint with simple
operation by a DC current and offering flat broadband comb spectra. However,
the data transmission performance achieved with QD-MLLD was so far limited by
strong phase noise of the individual comb tones, restricting experiments to
rather simple modulation formats such as quadrature phase shift keying (QPSK)
or requiring hard-ware-based compensation schemes. Here we demonstrate that
these limitations can be over-come by digital symbol-wise phase tracking
algorithms, avoiding any hardware-based phase-noise compensation. We
demonstrate 16QAM dual-polarization WDM transmission on 38 channels at an
aggregate net data rate of 10.68 Tbit/s over 75 km of standard single-mode
fiber. To the best of our knowledge, this corresponds to the highest data rate
achieved through a DC-driven chip-scale comb generator without any
hardware-based phase-noise reduction schemes
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