Increasing incidents of cyber attacks and evolution of quantum computing poses challenges to secure existing information and communication technologies infrastructure. In recent years, quantum key distribution (QKD) is being extensively researched, and is widely accepted as a promising technology to realize secure networks. Optical fiber networks carry a huge amount of information, and are widely deployed around the world in the backbone terrestrial, submarine, metro, and access networks. Thus, instead of using separate dark fibers for quantum communication, integration of QKD with the existing classical optical networks has been proposed as a cost-efficient solution, however, this integration introduces new research challenges. In this paper, we do a comprehensive survey of the state-of-the-art QKD secured optical networks, which is going to shape communication networks in the coming decades. We elucidate the methods and protocols used in QKD secured optical networks, and describe the process of key establishment. Various methods proposed in the literature to address the networking challenges in QKD secured optical networks, specifically, routing, wavelength and time-slot allocation (RWTA), resiliency, trusted repeater node (TRN) placement, QKD for multicast service, and quantum key recycling are described and compared in detail. This survey begins with the introduction to QKD and its advantages over conventional encryption methods. Thereafter, an overview of QKD is given including quantum bits, basic QKD system, QKD schemes and protocol families along with the detailed description of QKD process based on the Bennett and Brassard-84 (BB84) protocol as it is the most widely used QKD protocol in the literature. QKD system are also prone to some specific types of attacks, hence, we describe the types of quantum hacking attacks on the QKD system along with the methods used to prevent them. Subsequently, the process of point-to-point mechanism of QKD over an optical fiber link is described in detail using the BB84 protocol. Different architectures of QKD secured optical networks are described next. Finally, major findings from this comprehensive survey are summarized with highlighting open issues and challenges in QKD secured optical networks.

Charcoal rot is one of the most destructive fungal diseases of soybean, caused by the pathogen called Macrophomina phaseolina. This disease thrives in warm and dry conditions, affecting the yield of soybean and other important agronomic crops. Existing methods used to screen the disease suffer from several drawbacks including, manual rating, low accuracy, high operating time, and high system complexity. To circumvent these drawbacks, we developed a laser biospeckle based sensor to characterize the charcoal rot in soybean crop. Applicability of the proposed sensor was tested to analyze three major aspects of plant disease management, viz. characterization of disease progression, early identification of disease symptoms, and analysis of genetic resistance of the given cultivar towards the disease. The experiments were conducted during Kharif season for two consecutive years (2019 and 2020) on two cultivars of soybean, namely, JS 90-41 and AMS-MB-5-18. The proposed sensor as well as standard rating protocol (i.e. measuring the length of necrosis) were used to analyze the extent of disease. To characterize the disease progression and the genetic resistance of different cultivars against M. phaseolina, two new metrics, charcoal rot severity index and disease susceptibility index were introduced. Biospeckle activity was found to be strongly correlated with the lesion length of infected plant stems (r = +0.96, p <; .01, two-tailed (for JS 90-41) and (r = +0.95, p <; .01, two-tailed (for AMS-MB-5-18) for the year 2019; and r = +0.97, p <; .01, two-tailed (for JS 90-41) and r = +0.93, p <; .01, two-tailed (for AMS-MB-5-18) for the year 2020). Experimental results clearly indicate that the proposed sensor can be used as an efficient tool to detect the disease in its early stages of pathogen development. This study provides insights into development and implementation of disease control measures for increasing soybean crop production.

Conventional biometric spoof detection sensors suffer from several problems, including complex and expensive sensor assembly, and design. They are susceptible to environmental perturbation, and are not robust against all types of spoof attacks. Further, for a secured biometric sensor, hierarchy of spoofing attempts (i.e. curious attempts, low-level attack and high level attack) needs to be precisely distinguished to perform different actions (e.g. a high level attack should be handled carefully). In this letter, we propose a novel three-level anti-spoof palmprint biometric sensor using low cost components and simple optical techniques (photography, fringe projection and biospeckle analysis). At the first level, to eliminate the unwanted curious users, a 2D image of the palmprint is captured and feature matching is performed. Next, the most prevalent low level attacks (photo and layered attacks) are detected using fringe projection profilometry. At the final level, a novel biospeckle index based on Subtraction average technique is introduced to quantify the liveliness map for eliminating high level attacks including fake prints and cadavers. Robustness of the biospeckle analysis against different possibilities to generate false activity (tremor, air flow and heat flow) is also been verified.

Biospeckle analysis is a useful tool for nondestructive characterization of different samples in diverse areas such as agriculture, engineering, biomedical imaging, medicine, and many more. In this paper, we present a single transform based framework to address three major aspects, viz. numerical quantification, sub-band decomposition and compression of biospeckle data. The discrete cosine transform (DCT) has been advantageously used to develop foundation for all three processing paradigms. First, an efficient method for numerical quantification of biospeckle activity using DCT has been developed. The salient features of the proposed strategy include its extreme simplicity, low complexity, and high accuracy. Furthermore, DCT has also been used in conjunction with the traditional processing methods to decompose and analyze the biospeckle activity associated with different sub-bands. The analysis allows isolation of different physiological and biological processes responsible for overall biospeckle behavior inside the specimen. DCT based image compression strategy to efficiently process the biospeckle data is also reported. Compression enables a way to faithfully process the biospeckle images with lower number of reconstruction coefficients and allows efficient storage and transmission. Performance evaluation and comparison of the proposed technique with the existing methods has been performed in both theoretical and experimental domains. To demonstrate practical utility of the proposed processing strategies blood coagulation process has been studied.

Fringe projection profilometry is one of the most widely used techniques for 3D shape measurement, including digital model generation, system identification, rapid prototyping, object replication, quality control, etc. In order to extract the desired profile information of the test object from the deformed fringe projected interferograms, in this paper, Hilbert transform based fringe analysis technique is utilized. Using analysis based on simulations, the efficiency of the proposed strategy is calculated. The retrieved results are compared with conventional single step as well as multi step phase extraction algorithms. Obtained results conclusively establish Hilbert transform to be optimum as compared to conventional techniques.

The measurement and testing of 3D profile plays a vital role in characterizing orthopaedic bone plates. As being implanted in human body, its shape must be accurately defined in order to avoid harmful side effects. In present communication, we report a low-cost, non-destructive measurement of 3D surface profile of titanium bone plate using fringe projection and automated interferogram analysis technique. Collimated light from a He-Ne laser is incident on a grating and the resultant sinusoidal pattern is projected on bone plate sample. Resulting deformed fringe pattern carries the information of the sample surface. For measurement of 3D topographic information, interferograms are recorded and analyzed using Fourier transform method. The proposed setup provides its feasibility of being non-contact, non-destructive, fast, low-cost and robust against environmental perturbations.