Optical fiber laser hydrophone which has more research potentiality and value owing to higher acoustic pressure sensitivity, smaller size and lower difficulty of multiplexing. However the detecting capacity to low frequency signal of optical fiber laser hydrophone will be limited because of the low frequency noise such as 1/f noise and thermal noise of optical fiber laser and pumped laser. In order to suppress these noises, the iterative discrete wavelet transformation algorithm was designed which used multi-scale trait of wavelet transform. The different spectral components of underwater acoustic signal were separated and the noises below 1kHz were eliminated on the basis of the target signal amplitude would not be weakened. The measured data acquisitive from anechoic tank showed that the algorithm reduced the noise below 1kHz nearly 50dB and the Signal to Noise Ratio(SNR) is improved from 55.23dB to 84.05dB.
Recent compressed sensing (CS) results show that it is possible to accurately reconstruct images from a small
number of linear measurements via convex optimization techniques. In this paper, according to the correlation analysis
of linear measurements for hyperspectral images, a joint sparsity reconstruction algorithm based on interband prediction
and joint optimization is proposed. In the method, linear prediction is first applied to remove the correlations among
successive spectral band measurement vectors. The obtained residual measurement vectors are then recovered using the
proposed joint optimization based POCS (projections onto convex sets) algorithm with the steepest descent method. In
addition, a pixel-guided stopping criterion is introduced to stop the iteration. Experimental results show that the proposed
algorithm exhibits its superiority over other known CS reconstruction algorithms in the literature at the same
measurement rates, while with a faster convergence speed.
After concluding the application of under-water optics, the development of under-water laser imaging technology is
reviewed. The main types of laser imaging technology are introduced, such as laser scanning imaging, distance selected
imaging, and three-dimensional technology. The respective imaging principle, characteristics and update status are
presented. Furthermore, the newest detecting technology, such as fiber optic hydrophone, under-water holograph and
under-water spectrum detecting technology are described in detail. The recent researching status and new application are