An optical fiber based immunosensing platform formed by two identical chirped long period gratings (CLPGs) for sensitive and label-free detection of Escherichia coli (E. coli) is presented. The proposed immunosensor having two CLPGs with an inter-grating space (IGS) works like a Mach-Zehnder interferometer. The important feature of this sensor is that by changing the refractive index (RI) induced phase at the IGS region, a corresponding shift in resonance wavelength can be realized without affecting the actual grating region. Additionally, the confining bandwidth of the interference fringes promotes greater resolution in the resonance wavelength analysis of the transmission spectrum. The main aim of this study was the specific and rapid detection of the E. coli bacteria in phosphate buffer saline (detection range: 10 cfu/ml to 60 cfu/ml) by using the bio-functionalized IGS region as a sensing probe of the dual CLPG structure. The observed detection limit was 7 cfu/ml. For specificity analysis, Salmonella typhimurium and Staphylococcus aureus were tested and no significant shift in resonance wavelength was observed. In addition, the proposed immunosensor has the ability to selectively detect E. coli in real samples including lake water. The high specificity, good sensitivity to ambient RI, and robustness of the developed sensing platform will open a new avenue in optical immunosensing technology, and cascaded long CLPG sensors can contribute significantly to the detection of pathogenic bacteria in water and food samples.

Image-based fusion is a state-of-the-art process to extract vital information by combining the two or more images acquired from different satellite sensors. Recently launched (September 26, 2016) Indian Space Research Organization’s (ISRO) Ku-band (13.5 GHz)-based Scatterometer Satellite (SCATSAT-1) as an active microwave sensor can offer the day–night, all-weather monitoring services, which are not possible with the optical-based visible and infrared remote sensing satellites. Therefore, the fusion of optical and microwave data offers the cloud-free detection of Earth surface transitions and helps in emergency response to natural hazards, security, and defense. The objectives of the proposed framework are: 1) nearest neighbor-based fusion (NNF) of ISRO’s SCATSAT-1 and National Aeronautics and Space Administration’s (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) optical data; 2) generation of thematic maps using artificial neural network (ANN)-based classification of the fused data; 3) detection of spatiotemporal variations via postclassification comparison (PCC)-based change detection; 4) cross-referencing with well-defined fusion methods, i.e., Gram–Schmidt (GS), Brovey transformation (BT), and Ehlers; and 5) impact analysis of clouds on the input dataset and fusion methods. This study has been conducted over the Western Himalayas to estimate the snow cover changes under cloudy conditions with two datasets, i.e., winter and monsoon. The experimental outcomes confirm the efficacy of the proposed framework in the effective removal of clouds, generation of classified maps, and change maps. The present study includes an exhaustive list of applicative situations for cloud-free monitoring using freely and daily-based SCATSAT-1 and MODIS datasets.