Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 6 Articles
As one of the core devices for an electro-optic analog-to-digital converter (ADC), the\nMachâ??Zehnder (MZ) modulator plays an important role, and the output stability of the MZ\nmodulator has a decisive influence on the conversion accuracy of the ADC. This paper proposed a\npilot tone-based method to stabilize the bias point of the modulator. This method could obtain the\ncorresponding control voltage of the MZ modulator by adding a KHz-level dither tone to the bias\nend of the modulator and calculating the ratio of the first and second harmonic components. The\nexperimental results showed that the output optical power of the modulator was stable at 3.2 dB\nwhen the bias point of the modulator was set at the orthogonal point. Moreover, the fluctuation\nrange was not more than 0.15 dB, the first harmonic of the output signal was stable at 50.5 dB, and\nthe fluctuation range was not more than 0.6 dB. The proposed bias controller based on the field\nprogrammable gate array (FPGA) and digital signal processing (DSP) can stabilize the modulator\nbias point at the orthogonal point and with a relatively high locking accuracy....
In this paper, we propose a new versatile routing device that utilizes arrayed waveguide\ngratings (AWGs), optical switches, and optical circulators to implement reconfigurable optical add/drop\nmultiplexers (ROADMs), optical interleavers, and optical cross-connect (OXC).With the development of\ndense wavelength division multiplexing (DWDM) technology, ROADM and OXC technologies have also\nbeen put into practical use. Thus, the optical signal can be routed directly in the optical network according\nto its wavelength without the need for optical-electrical-optical (OEO) conversion. Although different\noptical network units (ONUs) have different bandwidth requirements, the use of optical interleavers has\nsuccessfully solved the connection problem between old and new systems. According to the numerical\nexperiments of static characteristics, the proposed routing device can effectively implement three different\nfunctionalities, thereby providing greater flexibility for fiber optic network applications....
AO (adaptive optics) systems have been extensively used to improve the beam quality in high-energy lasers; however, few studies\nhave focused on how much the beam quality could be improved. A novel evaluation criteria and factor is presented in this paper.\nThe factor, defined as power in ring (PIR), is expressed by distinguishing the low- and high-spatial frequency components in the\nfar-field laser intensity distribution. Beams with different PIR values are generated in our model, and then they are compensated\nby AO systems. Calculation result shows that the PIR factor could evaluate a laser beamâ??s improvement potential by an AO\nsystem quantitatively....
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Plasmodium falciparum (P. falciparum) malarial degree of infection, termed as parasite density (PD), estimation is vital for pointof-\ncare diagnosis and treatment of the disease. In this work, we present application of optical techniques: optical absorption and\nmultispectral imaging for P. falciparum malarial byproduct (hemozoin) detection in human-infected blood samples to estimate\nPD. The blood samples were collected from volunteers who were tested positive for P. falciparum infections (i-blood), and after\ntreatment, another set of blood samples (u-blood) were also taken. The i-blood samples were grouped based on PD (+, ++, +++,\nand ++++). Optical densities (ODs) of u-blood samples and i-blood samples at blood absorption bands of 405 nm, 541 nm, and\n577 nm showed different optical absorption characteristics. Empirical computation of ratio of the ODs for the blood absorption\nbands revealed reduction in the ODs with increasing PD. Multispectral images containing uninfected red blood cells (u-RBCs)\nand P. falciparum-infected red blood cells (i-RBCs) on unstained blood smear slides exhibited spectrally determined decrease in\nboth reflected and scattered pixel intensities and increase in transmitted pixel intensities with increasing PD. We further propose a\nlinear classification model based on Fisherâ??s approach using reflected, scattered, and transmitted pixel intensities for easy and\ninexpensive estimation of PD as an alternative to manual estimation of PD, currently, the widely used technique. Application of\nthe optical techniques and the proposed linear classification model are therefore recommended for improved malaria diagnosis\nand therapy....
In this work, we fabricated dual-band 800 Ã? 2 short-wave infrared (SWIR)\nindium gallium arsenide (InGaAs) focal-plane arrays (FPAs) using N-InP/i-In0.53Ga0.47As/N-InP\ndouble-heterostructure materials, which are often applied in ocean-color remote sensing.\nUsing narrow-band interference-filter integration, our detector-adopted planner structure produced\ntwo detection channels with center wavelengths of 1.24 and 1.64 microm, and a full-width half-maximum\n(FWHM) of 0.02 microm for both channels. The photoelectric characteristics of the spectral response,\nmodulation transfer function (MTF), and detectability of the detector were further analyzed. Our FPAs\nshowed good MTF uniformity with pixel operability as high as 100% for each 800 Ã? 1 linear array.\nPeak detectivity reached 4.39 Ã? 1012 and 5.82 Ã? 1012 cm.Hz1/2/W at 278 K, respectively, and response\nnonuniformity was ideal at 2.48% and 2.61%, respectively. As a final step, dual-band infrared detection\nimaging was successfully carried out in push-broom mode....
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