Spectral-Coding-Based Compressive Single-Pixel NIR Spectroscopy in the Sub-Millisecond Regime

In this contribution, we present a high-speed, multiplex, grating spectrometer based on a spectral coding approach that is founded on principles of compressive sensing. The spectrometer employs a single-pixel InGaAs detector to measure the signals encoded by an amplitude spatial light modulator (digital micromirror device, DMD). This approach leads to a speed advantage and multiplex sensitivity advantage atypical for standard dispersive systems. Exploiting the 18.2 kHz pattern rate of the DMD, we demonstrated 4.2 ms acquisition times for full spectra with a bandwidth of 450 nm (5250–4300 cm−1; 1.9–2.33 µm). Due to the programmability of the DMD, spectral regions of interest can be chosen freely, thus reducing acquisition times further, down to the sub-millisecond regime. The adjustable resolving power of the system accessed by means of computer simulations is discussed, quantified for different measurement modes, and verified by comparison with a state-of-the-art Fourier-transform infrared spectrometer. We show measurements of characteristic polymer absorption bands in different operation regimes of the spectrometer. The theoretical multiplex advantage of 8 was experimentally verified by comparison of the noise behavior of the spectral coding approach and a standard line-scan approach.

Image processing method based on aerospace monitoring

The paper considers a digital image processing method that provides efficient transmission, redistribution and storage of aerospace environmental monitoring videographic information. The requirement to increase the monitoring efficiency, if necessary, to carry out regular monitoring of changes in the image field of the observed object is especially relevant when describing spatially aligned sets of images obtained after multi-zone, multi-time and multi-polarization shooting. In many remote sensing applications, the processing efficiency reflects the degree of reduction in the volume of transmitted, described, analyzed and stored videographic information. The computational processing of digital images based on the coordinate survey scheme is presented. The method can be used to perform the procedure for decoding images in order to solve the problem of classifying objects of interest, analyzing images. Such characteristics of binary objects as a spatial boundary and a contour were used as deciphering signs. These features make it possible to describe the shape of an object, its geometric parameters and search for images with specific spatial structures. The processing method is realized by executing efficient algorithms for coding an image on a discrete grid by means of a chain code and spectral coding based on the fast discrete Hartley transform. The result of processing comes down to minimizing the number of such basic computational operations as multiplication, addition, transferring, as well as reducing the time and capacitive complexity of the program, and reducing the redundancy of the initial data. An example of an effective representation and description of a segmented image of an object is given. The proposed method makes it possible to expand the technical capabilities of more efficient transmission and processing of images for solving problems in the field of remote sensing.

Multi Spectral Coding in RADAR Signal Conditioning using Recurrent Spectral Mapping

Observed varying interference in radar signal processing limits the accuracy of target detection. Signal processing approaches using spectral coding are used in computing the Doppler. The spectral processing are however computationally slower due to large processing coefficients. In this paper, a new selective process for spectral bands is proposed using recurrent band mapping to derive a scale level selection in radar processing. A stopping criterion developed, limits the additional computation overhead in radar signal processing, and reduces the delay in computation of decision making. The simulation of the proposed approach validates the Doppler profile and delay parameter under different data rate and fractional order of receiving signal.

Spectral coding performance under free space optical medium

<span> This paper focus on performance of code Zero Correlation-Correlation (ZCC) in free space optical communication. The ZCC code has a superior characteristic which eliminate the overlapping code between any users. Due to this high class characteristic, the code improves the performance of the conventional code in free space optical environment. In this paper the analysis performance of bit error rate is considering the avalanche (APD) noise, thermal noise and multiuser interference. The result shows that ZCC code improve the performance of conventional code in term of number of users, power received and data bit rate.</span>

Enhanced Performances of W/S SAC-OCDMA System Using LDPC Code

In an incoherent optical code division multiple access (OCDMA) system using amplitude spectral coding (SAC), which exceeds 1.5 Gbps, it is difficult or impossible to make a transmission with a bit error rate better than 10–9. For this, it is necessary to associate an error correction code (ECC) to the SAC-OCDMA system. In this paper, we proposed an architecture of a two-dimensional SAC-OCDMA system (spectral (w) and spatial (s)) using multi-diagonal code (MD) as spreading code and low-density parity check code (LDPC) as ECC. According to the properties of the MD code and the proposed architecture, the phase induced intensity noise is eliminated, which has improved the performance of the system. The theoretically results shows that LDPC/2D-SAC-OCDMA allowing more than 40 users to be multiplexed compared to a non-coded 2D SAC-OCDMA system. This combination allowed us to increase the cardinality of the LDPC/SAC-OCDMA (W/S) system without using an optical hard limiter.