Soil nutrient availability is a critical determinant of plant health and productivity, strongly influenced by soil moisture dynamics, particularly the water-filled pore space (WFPS). Optimal nutrient uptake typically occurs near 50% WFPS, where a balanced presence of air and water promotes microbial activity, solute mobility, and efficient root absorption. Accurate monitoring of this moisture-nutrient interaction is essential for precision agriculture and sustainable land management. This work presents a highly sensitive, cost-effective and non-invasive hybrid single split ring resonator (HSSRR) sensor, fabricated on a Rogers RT/Duroid 5880 substrate with a thickness of 1.57 mm. The sensor is designed for simultaneous assessment of soil moisture and nutrients within the 2.4 GHz ISM band. The proposed split-ring topology enhances electric field confinement, achieving field intensities on the order of 104 V/m, thereby increasing sensitivity to changes in the surrounding dielectric environment. Experimental results show that the sensor exhibits a resonant frequency shift sensitivity of approximately 5.5% at ϵr’=10, with effective operation up to ϵr’=15. Importantly, a strong correlation is also established between WFPS and the inverse square of the resonant frequency, modelled by a third-order polynomial with a high coefficient of determination (R2=0.9951), reinforcing the sensor’s capability in capturing soil moisture variations through frequency-domain analysis. In addition, the sensor accurately quantifies dielectric loss through loss tangent (tanδ) measurements ranging from 0 to 0.52, demonstrating strong sensitivity to Nitrate-N concentration (0-100 ppm), particularly under elevated WFPS conditions. An analytical model is developed to estimate Nitrate-N concentration as a function of dielectric loss and WFPS, and is validated using controlled experimental data with quantified prediction uncertainty. These findings establish the HSSRR sensor as a robust platform for real-time, in-situ monitoring of soil moisture and Nitrate-N variability, supporting data-driven nutrient management, optimized irrigation practices, and sustainable agricultural decision-making.

The widespread use of pharmaceuticals has led to increasing concern over the environmental persistence and biological risks of paracetamol (PA). Its frequent detection in surface and drinking water highlights the need for sensitive, rapid, and on-site detection methods. In this study, we present the first application of a surface acoustic wave (SAW) sensor for PA detection. The sensor is functionalized with a nanocomposite of titanium dioxide nanoparticles and carboxylated multi-walled carbon nanotubes, combining SAW’s high sensitivity with nanomaterial-based molecular selectivity. A fully integrated platform is developed, featuring a microfluidic sampling module and automated real-time phase response acquisition. The system exhibited a clear linear relationship between phase shift and the logarithm of PA concentration over a broad range (100 nM–1 mM), achieving a sensitivity of 0.9799°/decade (R² = 0.9995) and a limit of detection (LoD) of 28.6 nM. The response time reached 3.26 s, and the device demonstrated good repeatability (RSD = 6.53

Accurate assessment of soil moisture content (SMC) and soil pH is crucial for optimizing agricultural productivity, maintaining environmental sustainability, and preserving soil ecosystem health. SMC influences plant growth and nutrient bioavailability, while soil pH regulates microbial activity, nutrient solubility, and overall soil fertility. Given their significance, developing precise, efficient, and real-time sensing technologies is essential. This work introduces a novel microstrip line-integrated spiral-resonator-based planar sensor with a truncated ground, engineered for high-sensitivity soil dielectric characterization. The sensor, specifically designed to operate at 2.4 GHz, is evaluated by examining its transmission coefficient (S-12), with emphasis on frequency displacement and variations in S-12 magnitude under loaded conditions. Experimental validation confirms that the sensor reliably estimates dielectric constant (& varepsilon;'(r)) from 1 to 15 and loss tangent between 0 and 0.2. Using these parameters, it quantifies SMC within 0%-20% with a low error of +/- 0.8%. For pH detection, two second-order polynomial models are used, producing outputs for acidic (pH: 3-6) and alkaline (pH: 8-10) ranges relative to neutrality (pH = 7). Thus, rather than providing a unique pH value, the sensor effectively indicates the degree of deviation from neutral soil conditions, demonstrating suitability for precision agriculture (PA) and environmental monitoring.

This paper presents a novel self-octuplexing substrate-integrated waveguide (SIW) cavity-backed slot antenna for eight-band wireless communication services. This antenna employs eight semi-elliptical-shaped slots on an octagonal SIW cavity with different lengths to radiate at eight different frequencies. The eight radiating frequencies are 2.7, 3, 3.3, 3.6, 3.9, 4.2, 4.5, and 4.72 GHz, with impedance matching is less than -10 dB. Each radiator is backed by an eighth-mode SIW cavity and excited by a 50 Omega microstrip line. A designed prototype of the antenna is fabricated and tested. It has more than 34 dB measured isolation among any two ports. The maximum measured antenna gains are 4.4, 4.19, 4.11, 4.03, 4.19, 4.28, 5.2, and 5.44 dBi at the respective operating frequencies. It has a measured cross-polarization level of below -24.2 dB in the boresight direction and a front-to-back ratio of more than 10.4 dB in all the bands. All the slots can be tuned independently to radiate at the desired frequency band. This antenna can easily be integrated with other planar circuits due to an unperturbed ground plane.

Material characterization utilizing electromagnetic planar sensors is a promising area within modern sensing technology. This work introduces a novel sensor design based on a microstrip line (MSL) structure coupled with three hexagonal-shaped complementary split-ring resonators (HCSRR) etched onto the ground plane. The primary purpose of the proposed sensor is to measure the dielectric constant of the material under test (MUT). The MSL-HCSRR sensor is specifically engineered to operate within the Industrial, Scientific, and Medical (ISM) frequency band centered at 2.4 GHz. The total dimensions of the sensor structure are optimized to 0.35 λ0 × 0.16 λ0 × 0.01 λ0. The interaction of electromagnetic waves with the MUT induces a shift in resonant frequencies, utilized for material characterization. The proposed MSL-HCSRR configuration exhibits an E-field distribution of about 1.15 x 104 V/m and hence, enhances the sensitivity of the sensor by inducing a resonance response that is influenced by the changing dielectric properties of the MUT. This approach enables precise and reliable characterization of materials, particularly those with varying dielectric constants.

A photonic crystal fiber sensor is designed and analyzed based on the interaction of guided light with plasmonic layer of Au deposited both externally and internally to undergo surface plasmon resonance (SPR). The sensor has eight microchannels with Au of thickness of 0.03 μm surrounding them. For internal metal deposition, Au layer of 0.03 μm is also deposited internally outside analyte filled in inner layer of PCF holes. The sensor is found to have maximum confinement loss of 642.38 dB/cm in the RI range of 1.35–1.45 RIU. The confinement loss peak at the resonating wavelength is utilized to detect analytes in wide detection range with maximum wavelength sensitivity of 250 nm/RIU and amplitude sensitivity of 7.77 RIU−1. The proposed sensor is also compared in performance with modified sensor design using dual plasmonic layers of Au and TiO2 in combination. The proposed sensor is found to outperform the dual layer plasmonic sensor in terms of both sensitivity and full width half maxima (FWHM) value and can be used to detect a number of biochemicals of both low and high refractive indices owing to its wide detection range.

This paper presents a theoretical investigation of a spectrally broad and tunable optical frequency comb to overcome the growing strains and effectively utilize the optical fiber network. The proposed Optical Frequency Comb (OFC) has high-quality frequency lines, whose parameters are analyzed with the initial line spacing of 10 GHz, offering the capability to tune the frequency spacing. The OFC constitutes two Dual Drive Mach-Zehnder Modulators (DDMZMs) and a phase modulator controlled by periodic radio frequency signals RF1 and RF2 respectively. The employed DDMZMs are configured deliberately, to focus on obtaining the low-duty cycle periodic signal, which automatically leads to the expansion of the spectrum. DDMZM1 changes the shape of the Gaussian periodic signal to produce output at the transition time of the input signal. DDMZM1 is connected to DDMZM2 by an optical delay line which gives a delay of approximately 25 ps. DDMZM2 is an intensity modulator that provides a very low-duty cycle Gaussian periodic signal. The phase modulator expands the spectrum by modulating the phase of the incoming signal. Therefore, the reported OFC exhibits tunability and broad spectrum with 86 frequency lines within a maximum power deviation of 2 dB. The OFC can be credibly used as a multichannel source in high-speed and flexible optical communication and all-optical computing systems.

With the ever-growing demand for ultra-fast data transmission, ensuring the security of data transmission in optical networks has become paramount. Therefore, this manuscript proposes an all-optical data security system at a bit rate of 250 Gbps. The proposed system is an all-optical encryption-decryption system. An orthogonally polarized secure key (OPSK) is used to encrypt the signal at the transmitter, and the same key is used at the receiver to decrypt the encrypted signal. This system leverages OPSK, inducing cross-gain modulation in semiconductor optical amplifiers to cipher the input signal at the transmitter and decipher the encrypted signal at the receiver for the optical network. A high-quality (Q) factor of 39.91 dB and a good extinction ratio (ER) of 10.14 dB are obtained for the encrypted signal. Similarly, for the decrypted signal, good Q factor and ER of 22.59 dB and 11.42 dB, respectively, are obtained at a typical distance of 76.7 km for the operating speed of 250 Gbps, thereby validating its performance in ultra-high-speed optical networks.

Abstract A flexible optical communication network is needed to realize a backbone transport network for 6G communication and further higher generation communication technologies. However, the practical implementation of the higher generation network experiences some serious challenges due to the existing multicarrier generation technology i.e. an array of multiple discrete laser sources (less spectrally efficient, complex, bulkier and costlier). Recently, a multicarrier generation technique using the optical frequency comb has been extensively researched. It can reduce the complexity, cost, and size compared to the existing multicarrier generator. Moreover, it increases the utilization of available spectral efficiency due to its capability to tune the operating frequency and carrier spacing. So, considering these advantages, we reviewed the multiple optical frequency comb generation techniques, categorized as mode-locked laser, microresonator and electro-optic modulator based frequency combs. We identify the salient features of different frequency comb generation techniques by keeping the requirements of a flexible optical network in mind. We also reviewed the drawbacks and possible solutions proposed to improve the characteristics of the optical frequency comb. Further, we reviewed the optical frequency comb expansion techniques to broaden the spectrum of the optical frequency comb, which is the requirement in optical frequency comb suitable for communication applications. At last, we summarize the progress in the practical implementation of the optical frequency comb as a multichannel source in a flexible optical network.

Plasmonic Photonic Crystal Fiber (PCF) sensor has established a significant impact in the biomedical industry due to its capability of real-time monitoring with high sensitivity. This study proposes an efficient gold-coated dual-channel PCF sensor and its systematic geometrical investigation to detect six distinct types of cancer cells impacting various organs within the human body. The sensor achieves maximum wavelength sensitivity of 7928.57 nm/RIU and minimum wavelength resolution of 1.26 × 10− 5 for the detection of MCF-7 breast cancer cells. The sensor outperforms by providing a significant maximum Amplitude Sensitivity (AS) of -2856.7 RIU− 1 and minimum amplitude resolution of 3.5 × 10− 6 in the detection of MCF-7 cells, while the highest recorded Figure of Merit (FOM) is 282 RIU− 1 for MDA-MB-231 cells. The proposed sensor could prove to be an incredible photonic device that advances healthcare diagnostics and reduces mortality rates by facilitating the early identification of various cancerous cells.

This work presents the design and application of a square patch sensor, modified with a centrally positioned circular slot, fabricated on Rogers RT/duroid substrate with a relative permittivity (is an element of(r) )$ of 2.2. The sensor demonstrates a reflection coefficient of -47.36 dB at an operating frequency of 2.4 GHz. This design is employed to investigate the dielectric properties of soil as a function of varying moisture content (MC) across different soil textures. A comprehensive characterization of sandy loam and clay loam soils is performed to capture the dielectric variations as MC changes, demonstrating the dynamic interactions between free and bound water molecules within the soil matrix. Experimental measurements are conducted by systematically adjusting the MC from 0% to 17% in both soil types. Results indicate that sandy loam soil consistently exhibits a higher $\epsilon _{r}$ than clay loam soil at comparable moisture levels. Notably, at an MC of 17%, the $\epsilon _{r}$ of sandy loam soil is observed to be 19% greater than that of clay loam. These findings highlight the significant impact of soil texture and water distribution on soil moisture characteristics, underscoring the role of free water content as a determining factor. A fourth-order polynomial equation is derived to accurately model the MC %, demonstrating a high degree of fit with a coefficient of determination R-2=0.9605$ . Additionally, a linear relationship is observed between plant-available water (PAW) and MC, with notable variations between sandy loam and clay loam soils. This analysis provides valuable insights into the dependency of soil moisture retention and availability on soil texture, presenting a useful approach for soil moisture estimation and agricultural water management.

Heavy metals (HM) contamination in water poses a serious threat to agricultural sustainability, environmental safety, human and animal health. HM contaminants like lead, cadmium, copper, and mercury can accumulate in crops, soil, and water systems, entering the food chain and impacting ecological balance. These HM containments are one of the main causes of life threating diseases. This research addresses the need for a high-precision, photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor integrated with spectroscopy analysis, which is capable of detecting HM traces in water.

In this paper, we demonstrate a tunable optical frequency comb (OFC) to meet the growing internet traffic demands in optical communication systems. The proposed design utilizes a dual-drive Mach–Zehnder modulator controlled by a periodic radio frequency (RF) signal to generate a tunable OFC. The spectral bandwidth and maximum power deviation are then enhanced by exploiting the self-gain modulation induced inside a semiconductor optical amplifier (SOA). To do this, the SOA is operated in a deep saturation region by actively controlling its various parameters, such as injection current, confinement factor, differential gain, and effective area. Further characteristic parameters of the comb are improved by controlling the extent of interference using an interferometric structure that incorporates two SOAs, working in the deep saturation region, and two 3 dB directional couplers. The resultant is a flat and spectrally broad OFC, which comprises 73 frequency comb lines with a maximum power deviation of 2.65 dB within the spectral bandwidth of ∼1.34 THz. Various metrics of the OFC have been analyzed, such as spectral flatness (or flatness index), mean power, power standard deviation, spectral entropy, and normalized entropy.

Soil assessment provides valuable insights into its overall quality, particularly regarding its capacity to retain moisture and deliver essential nutrients. The amount of moisture in the soil has a significant impact on its dielectric behavior, and this effect is further influenced by the presence of organic matter content (OMC), which enhances water storage, distribution, and ion exchange. When OMC levels change, key dielectric properties such as relative permittivity, conductivity, and loss factors also shift, ultimately influencing the soil's electromagnetic behavior and offering clearer insights into the interactions between soil, water, and organic matter. This work proposes a low-profile microwave planar sensor with dimensions of 24x10x0.79 mm3, implemented using a Minkowski fractal geometry-based defective ground structure (DGS), for characterizing the dielectric properties of soil. The sensor is designed to analyze the complex relative permittivity of the soil and works in the transmission domain. The research demonstrates that soil with a similar texture but different proportions of organic matter exhibits differences in the real and imaginary parts of the complex relative permittivity as the moisture content (MC) varies from 0% to 20%. Soil with low OMC has a higher epsilon ' r and lower dielectric losses compared to soil with high OMC. The proposed sensor offers high frequency detection resolution (FDR) and sensitivity of about 23.85 MHz and 0.994%, respectively, for a maximum relative permittivity ( epsilon '(r) ) of 55. A mathematical model is developed to estimate the soil's relative permittivity and dielectric losses, along with a third-order polynomial to estimate the MC as a function of frequency.

Due to the massive rise in the adoption of user applications having ultra speed along with the evolution of 5G/6G networks and the Internet of Things (IoT) framework, the requirement of ultra transmission rates has raised concerns for service providers and researchers across the globe. Consequently, a high-speed framework has become the necessity of today’s communication network and the research community is carrying out intensive research in this field globally. In this work, we have proposed a hybrid wavelength division multiplexing (WDM) based single-mode fiber (SMF)-free space optical (FSO) link employing multiple input multiple output (MIMO) transmission. The proposed hybrid design supports a channel length of 20 km (SMF) + 1.51 km (FSO) + 20 km (SMF) and we have examined the system performance for supporting a diverse range of optical network units (ONUs). The proposed model has demonstrated promising results for supporting a large number of ONUs at the receiver section while ensuing bit error rate of 10^-9 .

A U-slot located symmetrically at the centre of the patch has been utilized to enhance the patch antenna's operating bandwidth compared to the standard conventional patch. The operating frequency range of the circumferential patch antenna is from 8.61 to 11.43 GHz, while the axial patch covers the frequency range 8.71 to 11.33 GHz (covering X band). The antenna shows excellent gain with minimal variation in both E and H-planes across the operating frequency range. Moreover, the antenna achieves less than -10 dB sidelobe levels in both E and H-planes across all frequencies and configurations. The co and cross-polarization plots are also depicted to show the excellent polarization purity of the antenna for the planar and cylindrical conformal configurations. The antenna may be suitable for airborne applications where the conformability to the Arial host body is of prime importance.

In this research, a new model of the photonic crystal fiber (PCF) biosensor, which uses the surface plasmon resonance (SPR) principle, is presented, with a focus on effectively identifying various cancerous cells in the human body. We specifically targeted six different types of cells, namely, Basal, Hela, Jurkat, PC 12, MDA MB 231, and MCF 7, which are linked to skin, cervical, blood, adrenal gland, and two types of breast cancers. The biosensor works by detecting shifts in resonance wavelength (RW) between healthy and infected cells. Our exploration involved a dual-mode investigation, considering both transverse magnetic (TM) and transverse electric (TE) polarization. The wavelength sensitivities ( S_W ) of 4000, 3333.33, 6071.42, 6428.57, 8428.57, and 13,571.42 nm/RIU and 3520, 2916.66, 5000, 7142.85, 8571.42, and 12,857.14 nm/RIU, and amplitude sensitivities ( S_A ) of 2482, 6124, 9773, 13,452, 15,289, and 18,651 RIU−1 and 1467, 2683, 5845, 7243, 10,089, and 16,864 RIU−1, are obtained for TM and TE polarizations, respectively. A sensor resolution ( S_R ) of the order 10−6 is achieved for both polarizations. Owing to its high sensing parameters and a novel combination of materials, the proposed dual-mode PCF SPR sensor shows significant promise as a valuable tool for perceiving cancer cells, potentially aiding in the early detection and management of various forms of cancer.

This article presents a proposal for a conformal, miniature microstrip antenna with wideband capability for use in implantable and ingestible devices on the Internet of Medical Things (IoMT) for biotelemetry applications. The antenna is designed to perform for medical implant communication system (MICS 402–405 MHz) band inside the human skin tissue. The wideband feature of the proposed design also supports performing well inside various tissues environments. The co-planar structure of the antenna widens its bandwidth; as a result, antenna resonance performance has become tissue independently. ${L}$ and ${U}$ slots are used to increase the radiation element length of an antenna. The antenna has been made using a single metallic layer on Roger RT/Duriod 6010 substrate. Furthermore, the antenna performance is also investigated by conforming to the antenna design with a radius of 5 mm. The proposed antenna is fabricated and tested inside artificial human skin mimicking phantoms. The antenna prototype has a volume size of 79.4 mm3, and its performance has been analyzed based on the reflection coefficient, radiation pattern, and specific absorption rate (SAR) value. The proposed design offers 134 and 142 MHz of bandwidth for planar and conformal design, respectively, with a maximum realized gain of −32.95 and −33.77 dBi, respectively, in homogeneous tissue. Finally, the proposed antenna is compact, wideband, and complies with SAR safety standard limits of up to 2.54-mW power. The investigated facilitates closer results concerning the numerical model.