The advancement of Probabilistic Constellation Shaping (PCS) is pivotal for high-capacity optical communication systems and the forthcoming 6G era. PCS aims to approach the Shannon limit, optimising signal efficiency and performance. However, phase noise from continuous-wave (CW) lasers significantly impacts system performance, especially in terms of bit error rate (BER). This paper introduces and evaluates phase noise estimation and correction using the Viterbi & Viterbi (V&V) algorithm at a 50 Gbaud symbol rate in dual-polarised high-capacity optical systems employing higher-order Quadrature Amplitude Modulation (QAM) schemes, such as 64-QAM and 256-QAM PCS. A comparative analysis with the Blind Phase Search (BPS) algorithm demonstrates the V&V algorithm’s ability to maintain BER of 10-5 and 10-4 for 64-QAM and 256-QAM PCS, respectively, under CW laser linewidth of 1 MHz. Extensive numerical results demonstrate that the V&V algorithm consistently meets the other analytical parameter requirements of the optical link under CW laser linewidths ranging from 10 kHz to 1 MHz. The implemented system design emphasises the V&V algorithm’s robustness in handling phase noise, highlighting its potential to enhance reliability and performance in high-capacity optical communication systems. The findings underscore the potential of our approach to meet the forthcoming requirements of optical links.

Photonic quantum information processing has emerged as a leading platform for demonstrating quantum advantage. Among these, Gaussian Boson Sampling (GBS) is a powerful model of quantum computation. However, practical GBS devices are intrinsically affected by fabrication imperfections, phase noise, and temporal drift, which distort output photon statistics and ultimately limit scalability and long-term stability. In this work, a noisy GBS device is numerically investigated using a 44 reconfigurable interferometer based on the Clements architecture. The interferometer is modeled using a multimode interference using 3D FDTD, yielding an extinction ratio of 47 dB and an insertion loss of 0.6 dB at 1550 nm. Noise and phase drift are incorporated through a Hamiltonian-based noise model. To quantify the impact of noise, graph decoding techniques were employed to characterize structural distortions in the sampled output distributions. Further, the fundamental limitations of static calibration in the presence of time-dependent drift were investigated. This work overcomes these limitations with an adaptive reinforcement-learning controller that can dynamically compensate for Hamiltonian drift and noise. Which maintains stable output statistics close to the target GBS distribution even under non-stationary perturbations. Finally, the potential applications of GBS, with the advantage of adaptive stabilization of GBS devices, were discussed.

This work presents a silicon-based antenna with directionality $\mathbf{9 6 \%}$ and compact size of $5.2 \mu \mathbf{m} \times 4.8 \mu \mathbf{m}$. It comprises subwavelength grating and periodic grating designed and optimized using FDTD and Genetic algorithm respectively. This work can be used in off-chip coupling, optical phased array applications.

This paper presents a compact, uniform power distribution and Monte Carlo-based fabrication tolerance analysis on a $1 \times 2$ silicon power splitter. Splitter with dimension $\mathbf{1. 7} \times \mathbf{1. 7} \bold symbol{\mu} \mathbf{m}$ achieves a low insertion loss of $\mathbf{0. 1 1 7 d B}$ and excellent uniformity of 0.0014 dB at the center wavelength of 1550 nm.

A broadband and ultracompact on-chip three-mode (de)multiplexer has been designed and demonstrated experimentally using a subwavelength grating-assisted asymmetric adiabatic coupler on the silicon-on-insulator platform. The device supports the (de)multiplexing of TE0, TE1, and TE2 modes for a broad bandwidth of 145 nm. The proposed device has a compact footprint of similar to 5 x 62 mu m(2). The fabricated device has a crosstalk of < -10 dB and insertion loss of <2.6 dB for wavelengths 1530 - 1675 nm (C-L-U band). The proposed three-mode (de)multiplexer is beneficial for mode division multiplexing and can be used for bandwidth enhancement in photonic network-on-chip systems.

This paper presents the design and demonstration of 1 × N (N = 2, 4) dual-mode optical switches on a silicon-on-insulator platform, optimized for mode division multiplexing (MDM). The switches utilize a multimode interference-based Mach-Zehnder interferometer combined with thermo-optic phase shifters for efficient mode control. For the elementary 1 × 2 switch, an insertion loss of less than 0.06 dB for the TE0 mode and 0.10 dB for the TE1 mode is achieved within the C-band, with crosstalk levels below − 30.5 dB for both modes. Scalability is demonstrated with a 1 × 4 switch, where the insertion loss is reduced to 0.61 dB for TE0 and 0.48 dB for TE1, and crosstalk is kept below − 37.9 dB for TE0 and − 35.5 dB for TE1 across all switching configurations. The switches are designed using the Lumerical Heat Solver module and the Eigenmode expansion method. With compact footprints of 6.5 × 750 μm² for the 1 × 2 switch and 15 × 1400 μm² for the 1 × 4 switch, these switches offer significant potential for intra-chip MDM systems and photonic integrated circuits.

To address the next-generation communication needs, we present a new framework to improve channel capacity. This framework combines forward error correction (FEC) rate Low-Density Parity-Check (LDPC) coding with advanced enhancements like higher-order modulation and Probabilistic Constellation Shaping (PCS). Our method targets the growing demands of 6G and future technologies. We examine LDPC code rates of 5/6, 8/9, and 9/10 for a fixed block length of 64,800 using 64-QAM and 256-QAM signals. The system features approximate 150 Gbaud symbol rate, capable of generating LDPC coded signals for both modulation schemes. Performance analysis over an optical channel shows the system’s resilience, even with phase noise from a laser source with a higher linewidth. We determine an optimized Optical Signal to Noise Ratio (OSNR) to meet Bit Error Rate (BER) targets of 10-6 in an Additive White Gaussian Noise (AWGN) channel, ensuring strong performance. The study also explores information-theoretic metrics like Mutual Information (MI), Generalized Mutual Information (GMI), and Normalized GMI (NGMI) for both 64-QAM and 256-QAM signals. We compare the performance of PCS with uniformly distributed QAM signals, providing a thorough evaluation. Through detailed experimentation and analysis, this research offers valuable insights into the practicality and performance of the proposed system, marking a significant advancement in sophisticated optical communication systems for future networks.

A compact on-chip dual grating filter using sub wavelength and multimode waveguide grating-assisted contra directional mode conversion has been designed and demonstrated experimentally. The device features a multimode waveguide grating (MWG)-assisted contra-directional mode converter with apodized gratings for a high side lobe suppression ratio. The apodization is followed by an adiabatic subwavelength grating-assisted mode converter for output in the fundamental mode. The filter is designed to operate at a center wavelength of 1545 nm and has a 3 dB bandwidth as large as similar to 6 nm. The two stages of the filter have a side-lobe suppression ratio as high as >30 dB and a cross-talk low as < -30 dB. With the filter having a device footprint of only 450 x 40 m(2), it is suitable for photonic on-chip integrations and can be scaled up for designing wavelength division multiplexing systems for local area network applications.

Subwavelength grating waveguides (SWG) have emerged as a promising choice for developing highly sensitive and compact sensors on silicon on insulator platforms. SWG offers better sensitivity in comparison to other reported sensors because of their strong modal interactions within SWG segments. To detect glucose concentration variations in the blood, a highly sensitive subwavelength grating double slot waveguide (SWGDSW) structure is proposed in this study with a numerically estimated sensitivity (S) of around similar to 800 nm/RIU. Along with this effect of optimising structural parameters on transmission spectra is also analysed. Further, the performance and effectiveness of the proposed optimised structure are also demonstrated by contrasting with existing SWG-based configurations for biosensing applications.

This paper offers a 3dB optical power splitter based on silicon-on-insulator (SOI) technology that gives nine equal outputs (1×9) at C-band, nearly the wavelength of 1550 nm. The architecture employs cascaded 3×3 multimode interference (MMI) couplers on a 220 nm silicon core situated above a 2–3 μm buried oxide layer. The MMI configuration is fine-tuned using 3D finite-difference time-domain (FDTD) simulations. Initially, one input is divided into three via a 3 × 3 MMI, and then each of those three channels is further split into three additional channels using identical MMIs, resulting in a total of nine outputs. Each output has approximately 1/9th of the input. with minimal excess loss, 0.1 dB for 3 × 3 and 0.2 dB for 1 × 9.

We proposed a highly efficient non-uniform waveguide grating antenna for off-chip coupling in the C band. The waveguide grating antenna is optimized using the genetic algorithm to achieve high diffraction efficiency and compact size.

The advancement of future photonic integrated circuits for data center networks relies crucially on the development of highly efficient, low-power, and compact switches. This paper presents the design of non-blocking 4 x 4 and 8 x 8 silicon photonics switches intended using Multimode Interferometer (MMI)-Mach-Zehnder interferometer (MZI) structures. These proposed switches consist of 2 x 2 MMI-MZI switches realized by changing the phase of an optical signal using the thermo-optic effect. At 1550 nm, the proposed 2 x 2 switch exhibits an insertion loss of 0.04 dB and crosstalk of < 39.95 dB. Similarly, the C-band showcases an insertion loss of < 0.06 dB and crosstalk of < -33 dB. To support complex network topologies and enhance network efficiency, a data center network necessitates a higher quantity of port switches. The results show that at 1550 nm, the insertion loss for the 4 x 4 and 8 x 8 switches is 0.47 dB and 1.02 dB, respectively. Furthermore, the insertion loss for the C-band is < 0.50 dB and < 1.5 dB, respectively. The switches exhibit crosstalk of -37.59 dB and -34.67 dB at 1550 nm, respectively. Additionally, they demonstrate crosstalk of < -30 dB for the C-band. This suggests the potential for further scalability in terms of port counts. The switches are designed using the eigenmode expansion method, and the micro heater is designed with a finite element heat transfer solver. These advantages and excellent performance make the device a promising candidate for use in advanced communication systems and photonic integrated circuits.

Waveguide grating antenna with compact size and high diffraction efficiency remains a significant challenge in beam steering applications for integrated Optical Phased Arrays (OPA). Traditional waveguide grating antennas have large footprints, limiting antenna arrays' density. High diffraction efficiency is essential for effective signal transmission, making it a crucial aspect of antenna design. Optical antennas need higher diffraction efficiency, compact size, and broader field of view to achieve this. The proposed work aims to design a single-etch grating antenna on a silicon-on-insulator (SOI) platform that emits light off-chip. The methodology combines the initial grating antenna designed using Finite-difference time-domain (FDTD) simulations and optimizes it with a genetic algorithm. The proposed design uses a transverse spliced grating, Bragg reflectors, and bottom reflector to achieve an impressive upward diffraction efficiency of nearly 88% operating in C -band centered at 1550 nm. The size of the proposed antenna is 2.8 mu m and offers a wide far-field beam width of 38 degrees x 136 degrees. This work enables new advancements in integrated waveguide grating antenna development, with potential applications in free-space optical interconnects and on-chip optical phased arrays.

The high-capacity data transmission over an optical communication network is the bottleneck to meeting future communication needs due to the substantial growth in the data transmission requirements, which increased yearly at an average rate of more than 25%. The new generation 5G, beyond 5G and 6G proven to be the most promising technology to meet such high-capacity data transmission requirements. Also, 60 GHz (mm-wave) would be the most promising candidate for wireless high-capacity data transmission between multiple radio terminals. The optical domain techniques, such as coherent detection and optical heterodyning for generating 60 GHz (mm-wave) signals, are adequate, mature, and cost-effective solutions for high-capacity data transmission. We propose a 60 GHz radio over fibre (RoF) system design and its performance analysis which established a noteworthy 168 Gbits/s high-capacity data transmission using 64-Quadrature Amplitude Modulation, optical heterodyning, coherent detection, and advanced digital signal processing (ADSP) chain. The optimized version of the optical heterodyne technique generates a 60 GHz radio frequency signal for connecting various radio nodes over the wireless channel. The decisive and crucial part of the designed system is the ADSP chain which is effectively used to mitigate the impairments generated, and it also improves the signal spectral efficiency and results in long-distance data transmission. The proposed RoF system design and its performance analysis prove that the 28 Gbaud high-capacity data transmission is achieved for more than 172 km distance of Standard Single Mode Fiber.

In this paper, a new scheme is proposed to realize reconfigurable and multifunction optical logic gates (XOR, XNOR, NAND, and OR) using a Mach–Zehnder interferometer with a tunable thermo-optic phase shifter (TOPS). The reconfigurable optical logic gates are realized by tuning the phase of an optical signal using TOPS without changing the physical device structure. The logical input “0” or “1” is considered corresponding to the phase of the optical signal at TOPS. The logical output of the proposed device depends on the light intensity at output ports. The device is designed on silicon on insulator (SOI) platform and the simulation result shows that the on–off extinction ratio is greater than 37 dB at 1550 nm and >25 dB for the C-band. Moreover, it has a low insertion loss of 0.09 dB at a wavelength of 1550 nm and <0.8 dB for the C-band window. The proposed optical logic gates can be a promising logical device for programmable photonic integrated circuits.

Despite the availability of effective hepatitis B vaccinations, the hepatitis B virus remains a serious global health concern. It is expected that early detection could aid in initiating therapy before the infection progresses to liver damage. A silicon nanowire rectangular optical waveguide has been demonstrated theoretically to detect the surface antigen of hepatitis B "HBsAg" based on label-free surface sensing using finite-element method-based COMSOL Multiphysics. Different procedural segments of the biomarker detection have been mimicked on the surface of a waveguide as adlayers to investigate the device theoretically. Initially, the parameters of the waveguide have been optimized to provide a large interaction of light and bio-analyte, i.e., to provide high sensitivity. The analyses are first performed at the waveguide level based on the light-analyte interaction. Furthermore, performances of the sensor have been obtained by incorporating this waveguide structure in the sensing arm of the Mach-Zehnder interferometer. The device structure shows ultra-high surface sensitivities such as phase surface sensitivity of 7.03×2πrad/nm and MZI surface sensitivity of 3421.89 µW/nm with an excellent detection limit of 2.92×10-3pg/mm2 for HBsAg detection. The proposed device can measure the HBsAg concentration as low as 0.00973 ng/mL, which is significantly low to detect the infection in an early stage.

A biosensor for detecting DNA hybridization via refractive index sensing has been demonstrated using a subwavelength grating (SWG) waveguide. Waveguide dimensions are selected by parametric optimizations to increase the mode-analyte overlap with considerations of typical silicon-on-insulator fabrications technology. DNA layer is added with a linker layer on silicon pillars of the SWG waveguide to optimize and detect the DNA hybridization. Some essential characteristics such as mode overlap factor, change in effective refractive index, waveguide sensitivity, and shift in resonance wavelength are computed for the different dimensional parameters of the SWG waveguide in DNA hybridization along with mode field intensity and normalized power using the finite element method. The DNA hybridization is shown by variation in normalized power of interacting light in cladding region of the waveguide for 0% to 100% fractional change of dsDNA and ssDNA. Waveguide sensitivity, shift in resonance wavelength, device sensitivity, and intrinsic limit of detection are obtained to similar to 0.157, 7.01, 605 nm/RIU, and 1.30 x 10(-4) RIU, respectively, for the optimized structure of SWG waveguide in sensing of DNA hybridization, which could be suitable aspects for detecting DNA hybridization.

A mode insensitive mode power splitter (MPS) based on multimode interference has been designed using silicon on insulator. The device supports fundamental and first-order transverse electric (TE) and fundamental transverse magnetic (TM) mode (TE0, TE1, and TM0) having minimum excess loss of 0.06 dB at input of 1550 nm wavelength, and less than 0.5 dB for a broad wavelength of 1410–1690 nm. Moreover, the proposed mode splitter has a low mode dependent loss (MDL) of 0.02 dB at 1550 nm and supports broad bandwidth of 280 nm having MDL <0.4 dB. The proposed MPS can be a useful mode division multiplexing component for optical networks.

The grating has a significant role in sensing applications. Similarly, the grating-assisted coupler has excellent potential in chemical sensing applications. The power coupling between two closely coupled waveguide couplers can be significantly tuned by incorporating grating between them. The grating has been taken of silica material with sinusoidal shape in variation. The grating layer is assumed to be embedded within the sensing layer while considering a changeable effective refractive index depending on the sensing layer substances. In the present paper, grating assisted directional coupler has been numerically analysed using its own developed MATLAB-based algorithm of finite difference method (FDM) scheme. FDM method has been applied to solve the Eigenvalue equation to obtain allowed Eigenvalues and corresponding Eigen vectors (TE and TM cases). In FDM, the analysis domain has been fine discretized into the mesh of 1-D equal spacing for reasonable accurate computation results. In experimental validation, Fibre Bragg grating (FBG) has been suspended between two high refractive index coupler regions, which act as a power coupling zone. Also, the coupling length has been changed from 5 to 20 $$\upmu$$ m for tuning purposes and then optimized for grating parameters viz. length, period, etc. The whole structure is 2-Dimensional (x and y directions) with invariant in the y-direction.

The optical orthogonal frequency division multiplexing (OFDM) is proven to be a most promising technology for the next-generation high-capacity and ultra-wide bandwidth 5G communication systems. 60 GHz millimeter-wave (mm-wave) frequency band is also becoming a most popular upcoming frequency spectrum due to today’s available dense frequency spectrum used for mobile, multimedia, and data communication, etc. We propose a system comprised of 60 GHz radio-over-fiber (RoF) model using optimized optical frequency quadrupling, coherent detection, channel estimation, and carrier phase correction techniques for ultra-wide bandwidth 16-quadrature amplitude modulation (QAM) OFDM baseband signal. The proposed RoF system’s outcomes have shown relatively better bit error rate (BER) of 3.1 × 10–3 to enable successful transmission of 110 Gbps data for more than 105 km optical link comprising of standard single-mode fiber (SSMF). System performance and obtained results show a potential to fulfill the requirements of 5G and cellular communication system.