KEYWORDS: Digital signal processing, Signal processing, Discrete wavelet transforms, Wavelets, Image compression, JPEG2000, Data storage, Data processing, Space operations, Image processing
Nowadays, with the development of space exploration technologies, satellites and other spacecraft have undertaken more important and complicated space science missions, which require powerful processing capabilities to conduct large amounts of probe data real-time processing and analysis. However, the raw data generation rate of space exploration is always far beyond space transmission ability, so orbit compression for original data is an essential technology. Digital Signal Processors (DSPs) with powerful signal processing capabilities have been widely used in various information processing spacecraft systems. However, the utilization of full DSPs’ performance potential depends on parallelism of programs. Based on the C6000, a series of commercial high performance DSP processors, the paper implement the entire discrete wavelet transform module in JPEG2000 image compression algorithm with linear assembly language. Combined with characteristics of DSP instruction sets and features of specific programs, we optimize programs and improve the execution performance by an order of magnitude than previous.
The upper limit of dynamic range (ULDR) of the fiber optic interferometric sensors (FOIS) based on the digital
heterodyne demodulation scheme is investigated in this paper. According to the analysis of the demodulation process, the
ULDR is restricted by two factors: the heterodyne frequency and the digital orthogonal demodulation algorithm. We
discuss the influence of both the factors on the ULDR respectively in detail and give the total ULDR of the FOIS system.
Experiments with the different delayed heterodyne scheme are conducted to verify the theoretical analysis and the results
are consistent with the analysis conclusion.
This paper presents a demodulation scheme using phase-generated carrier (PGC) for a fiber Fabry-Pérot interferometric (FFPI) sensor with high finesse. The FFPI is constructed by a polarization maintaining fiber ring resonator with dual-coupler (PMDC-FRR), which can eliminate the polarization induced fading phenomenon. Compared with the former phase demodulation methods, the PGC scheme in this paper does not assume a two-beam interferometric approximation for the Fabry-Pérot cavity, and can work at arbitrary value of finesse in theory. Two PMDC-FRRs with reflective coefficients of 0.5 and 0.9 are made in experiments for demodulation. Both the single-frequency and the wideband signals are successfully demodulated from the transmission intensities using the PGC demodulation scheme. The experimental results demonstrate that the PGC demodulation scheme is feasible for the FFPI sensor with high finesse. The effects of the reflective coefficient and the intensity loss to the finesse are also discussed.
A signal demodulation scheme based on heterodyne technique is demonstrated, which can help fiber-optic hydrophone
system meet the demand of large dynamic range and large scale multiplexing. Optical system based on the heterodyne
demodulation is given. Reference signal in the demodulation procedure is obtained from the optical heterodyne output,
which is quite different from other reported heterodyne techniques. This method not only simplifies RF electronics, but
also eliminates the effects of frequency shift vibration generated by the acoustic-optic modulators. Demodulation
algorithm is presented and the maximum signal processing capability is analyze. Experiments are carried out and the
results show that a signal with a frequency of 1kHz and amplitude of 40rad could be demodulated without distortion
when the heterodyne frequency is 64kHz. The same signal is demodulated using PGC scheme with a modulating
frequency equal to the heterodyne frequency, and the result shows distortion. Comparing the two demodulation methods
verifies that the system we have designed works well and is more suitable for the detection of large signal. Besides, this
architecture of system offering advantage of easy to be time-division multiplexed. Together with wavelength-division
multiplexing, it demonstrates the potential for the fiber-optic hydrophone to achieve large-scale arrays with high dynamic
range.
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