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We aim to achieve wavelength division multiplexing with a circular defect in two‐dimensional photonic crystal (CirD) laser that has an orthogonal lattice waveguide (OLW). In a simulation, we calculate the output extraction efficiency to discover a structure in which stronger optical output can be extracted for the CirD laser with OLW. Consequently, adjusting the edge face position and applying a semicircular port can strengthen the energy extracted from the edge face. This appears to be caused by changing the positional relationship between the standing wave mode and the edge face. Furthermore, the OLW‐W1 structure proposed in this report can achieve higher output extraction efficiency than the conventional OLW. The transmittance is enhanced by changing the structure near the edge face because this improves the matching of light speed in different media. [ABSTRACT FROM AUTHOR]

We propose a Dense Wavelength Division Multiplexing (DWDM) Demultiplexer for L band (1565–1635 nm) applications. The design comprises a Y-shaped branch, a circular ring cavity (CRC), a bus waveguide, and a drop waveguide. To simplify the fabrication process, a CRC cavity is used instead of a regular large ring resonator in the design. The diameter of the CRC cavity is 820 nm. Coupled mode theory is used to examine the behaviour of the proposed demultiplexer. Proposed design achieves a narrow resonant wavelength of 12.5 GHz with a 0.1 nm spectral linewidth, a high-quality factor of 15,789, and minimal cross-talk of − 85 dB between adjacent channels. The results confirm that there is a transmission peak at one of the output port, with simultaneous drop of transmission power i.e. zero, at other output port. Additionally, the results convey that the reflection is zero at the peak resonant wavelength for all channels. Further, the proposed design offers a fabrication tolerance of ± 1 nm for air hole and CRC radii at which the resonant wavelength and transmission would not be effected. [ABSTRACT FROM AUTHOR]

Photonic-integrated circuits based on erbium-doped thin film lithium niobate on insulator has attracted broad interests with insofar various waveguide amplifiers and microlasers demonstrated. Wideband operation facilitated by the broadband absorption and emission of erbium ions necessitates the functional integration of wavelength filter and multiplexer on the same chip. Here, a low-loss wavelength division multiplexer at the resonant pumping and emission wavelengths (∼1480 nm and 1530–1560 nm) of erbium ions based on angled multimode interferometer is realized in the erbium-doped thin film lithium niobate on insulator fabricated by the photolithography assisted chemomechanical etching technique. The minimum on-chip insertion losses of the fabricated device are <0.7 dB for both wavelength ranges, and a 3-dB bandwidth of >20 nm is measured at the telecom C-band. Besides, direct visualization of the multimode interference pattern by the visible upconversion fluorescence of erbium ions compares well with the simulated light propagation in the multimode interferometer. Spectral tuning of the wavelength division multiplexer by structural design is also demonstrated and discussed. [ABSTRACT FROM AUTHOR]

In this paper, two wavelength division multiplexing (WDM) optical communication systems employing an enhanced L-shape hybrid fiber amplifier (E-L-shape-HFA) are designed and simulated. Both scenarios utilize a combination of the second-order stimulated Raman scattering (SO-SRS) and a tunable optical filter (TOF) technique. One system consists of 16 channels, while the other has 23 channels. Three different frequency ranges: short band (S-band), conventional band (C-band), and long band (L-band) are covered. The integration of two techniques SO-SRS and TOF has been enhanced the system's performance to meet the tremendous development of the optical communication systems nowadays. The first scenario results achieved high average gain ( G av. ) of 35 dB and wide flat gain bandwidth of 75 nm expanded from 1520 to 1595 nm. In addition, the second scenario results achieved an ultra-wide flat gain bandwidth of 110 nm extended from 1515 to 1625 nm and G av. of 26 dB. Furthermore, a desirable average noise figure (NFav.) of 4 dB has been obtained for both scenarios at input signal power of − 25 dBm. Moreover, the system is examined and optimized at input signal power range from − 25 to 20 dBm a step of 5 dbm in terms of bit error rate (BER) and quality factor (Q-factor). [ABSTRACT FROM AUTHOR]

In this study, we report the successful development of a novel high-sensitivity intensity-based Surface Plasmon Resonance imaging (SPRi) biosensor and its application for detecting molecular interactions. By optimizing the excitation wavelength and employing a wavelength division multiplexing (WDM) algorithm, the system can determine the optimal excitation wavelength based on the initial refractive index of the sample without adjusting the incidence angle. The experimental results demonstrate that the refractive index resolution of the system reaches 1.77 × 10 − 6 RIU. Moreover, it can obtain the optimal excitation wavelength for samples with an initial refractive index in the range of 1.333 to 1.370 RIU and accurately monitor variations within the range of 0.0037 RIU without adjusting the incidence angle. Additionally, our new SPRi technique realized real-time detection of high-throughput biomolecular binding processes, enabling analysis of kinetic parameters. This research is expected to advance the development of more accurate SPRi technologies for molecular interaction analysis. [ABSTRACT FROM AUTHOR]

Measurement device independent quantum key distribution (MDI QKD) has attracted growing attention for its immunity to attacks at the measurement unit, but its unique structure limits the secret key rate. Utilizing the wavelength division multiplexing (WDM) technique and reducing error rates are effective strategies for enhancing the secret key rate. Reducing error rates often requires active feedback control of wavelengths using precise external references. However, for a multiwavelength laser, employing multiple references to stabilize each wavelength output places stringent demands on these references and significantly increases system complexity. Here, we demonstrate a stable, wavelength-tunable multiwavelength laser with an output wavelength ranging from 1270 to 1610 nm. Through precise temperature control and stable drive current, we passively lock the laser wavelength, achieving remarkable wavelength stability. This significantly reduce the error rate, leading to an almost doubling of the secret key rate compared to previous experiments. Furthermore, the exceptional wavelength stability offered by our multiwavelength laser, combined with the WDM technique, has further boosted the secret key rate of MDI QKD. With a wide wavelength tuning range of 5.1 nm, our multiwavelength laser facilitates flexible operation across multiple dense wavelength division multiplexing channels. Coupled with high wavelength stability and multiple wavelength outputs simultaneously, this laser offers a promising solution for a high-rate MDI QKD system. [ABSTRACT FROM AUTHOR]

We propose a controllable topological add-drop filter based on magnetic–optical photonic crystals. This add-drop filter is composed of two straight waveguides and a hexagonal photonic crystal ring resonator. The waveguide and ring resonator are constructed by three different honeycomb magnetic–optical photonic crystals. The expanded lattice is applied with an external magnetic field so that it breaks time-reversal symmetry and the analogous quantum spin Hall effect simultaneously. While the standard one and the compressed one are not magnetized and trivial, the straight waveguide supports pseudospin-down (or pseudospin-up) one-way states when the expanded lattice is applied with an external magnetic field of +H (or −H). The ring resonator possesses multiple resonant modes which can be divided into travelling modes and standing modes. By using the travelling modes, we have demonstrated the function of the add-drop filter and realized the output port control by changing the direction of the magnetic field. Moreover, a large tunable power ratio from near 0 to 52.6 is achieved by adjusting the strength of the external magnetic field. The structure has strong robustness against defects due to the topological protection property. These results have potential in wavelength division multiplexing systems and integrated topological optical devices. [ABSTRACT FROM AUTHOR]

In this paper, we have proposed and demonstrated a 100 Gbps data transmission system over hybrid single mode fiber (SMF)-free space optics (FSO) link using optical comb lines in wavelength-division-multiplexing technique. A continuous wave laser, two dual drive Mach-Zehnder modulators and four electrical attenuators are employed to generate optical frequency comb lines (OFCL). The OFCL generator generates 52 comb lines by optimizing biasing voltages. The OFCL lines with a side mode suppression ratio of ∼ 50dB and flatness ∼∼ 0.01dB are generated and used as an optical carrier in the proposed system. The performance of the system is investigated in different weather conditions, such as clear weather, hazy weather, heavy rain, light fog, moderate fog, and heavy fog. [ABSTRACT FROM AUTHOR]

This paper simulates the relative performance of various artificial intelligence (AI) techniques when applied to nonlinear distortion compensation in wavelength division multiplexing (WDM) optical communication systems. These procedures are less complex than state-of-the-art compensation methods and do not necessitate prior knowledge about the properties of data in neighboring WDM channels, which can be practically challenging. In this study, Neural Networks (NNs) were integrated into both the transmitter and receiver sections of 3- and 5-channel WDM systems, and the resulting enhancement in performance (Q-factor) was assessed across varying levels of fiber nonlinearities. While the NN stage enhances the system performance, the improvement decreases as expected with the channel number and γ . Next, two-stage architectures that employ a transmitter side NN together with a classifier at the receiver side were modeled. For the systems examined in this paper simple decision tree structures, boosting, forests, extra trees, and multi-layer perceptron (MLP) classifiers all yielded enhanced system performance compared to simple chromatic dispersion compensation (CDC) with the only exception being Ada boosting which decreased the Q-factor for γ = 14 W - 1 k m - 1 . The outcomes of these investigations show that the most effective performance in highly nonlinear WDM systems is attained by employing two-stage systems, with the incorporation of random forest or extra tree AI methods at the receiver side yielding the highest results. [ABSTRACT FROM AUTHOR]

In this paper, a novel architecture of bidirectional underwater wireless optical communication (UWOC) system has been proposed to interconnect stationary and moving underwater sensor nodes for diverse applications. To achieve the bidirectional communication, wavelength division multiplexing (WDM) and remodulation approach have been used in this work. The proposed bidirectional UWOC system works at 40 Gbps data rate for both downlink (stationary node to moving node) and uplink (moving node to stationary node). Two distinct wavelengths of 532 nm and 531 nm have been used for uplink and downlink, the main attraction of the proposed architecture is that both the laser sources are placed at the stationary node. The moving node do not have any laser source and it remodulates the signal for sending data back to the stationary node. Because of this, the moving node contains lesser components which results in cost effectiveness, low power requirement and light weight. The proposed system successfully transmits the bidirectional information at a link range of 40 m under pure sea conditions in the presence of distinctive air bubble populations. The observed bit error rate (BER) values are 1.89 × 10− 13 and 1.19 × 10− 04 for the downlink and uplink respectively at a link range of 40 m, these BER values are under the acceptable forward error correction (FEC = 2 × 10− 3) limit. The proposed bidirectional UWOC system is beneficial for the development of a high-speed last-mile underwater solution. [ABSTRACT FROM AUTHOR]

Summary While wavelength division multiplexing (WDM) technology combines several wavelengths onto a single waveguide, the technology of mode division multiplexing (MDM) allows many orthogonal modes of the same wavelength to operate simultaneously without interchannel crosstalk. Thus, the hybrid WDM and MDM network in which the two above‐mentioned techniques cooperate could give a several‐fold increase in the overall network capacity. Constructing this network requires hybrid wavelength‐and‐mode multiplexers, especially ones with high integration and complementary metal‐oxide‐semiconductor (CMOS) compatibility. In this paper, we propose a design of a four‐mode triple‐band multiplexer that is capable of multiplexing up to 12 separate optical signal flows by utilizing four eigenmodes (TE0, TE1, TE2, and TE3) and three‐wavelength windows, which center at 1310, 1490, and 1550 nm. The device is on silicon‐on‐insulator (SOI) platform, consisting of four butterfly‐shaped multimode interference (MMI) couplers, four directional couplers, and a 4×1$$ 4\times 1 $$ cascaded asymmetric Y‐junction coupler. Via numerical simulations, the proposed design is verified to be able to operate effectively on the three aforementioned bandwidth slots with an optical conversion efficiency of over 93% in all functions. Moreover, it exhibits insertion loss less than 1.5 dB and crosstalk smaller than −16 dB within 25 nm bandwidth at each wavelength window. These results can affirm the success of wavelength–mode combination, which leads to a massive improve in the channel capacity on the same optical multiplexing system for optical telecommunications and photonics on‐chip interconnections. [ABSTRACT FROM AUTHOR]

In recent years, high-performance thin-film lithium niobate (TFLN) electro-optic (EO) modulators boost the fast development of highly integrated, low loss, and large comb spacing EO frequency combs. Furthermore, ultra-short optical pulse trains (USOPTs) can be generated by the temporal domain compression of the optical frequency comb, which play an essential role in photonic sampling analog-to-digital conversion. Here, we demonstrate a flat and broadband EO frequency comb based on a packaged TFLN chip including a monolithic integrated intensity modulator, a phase modulator, and edge couplers. The 25 comb lines with a power fluctuation less than 3 dB are presented successfully. Moreover, we obtain a 10 GHz repetition rate USOPT, the pulse width of which is compressed to 2.67 ps. Our device may find its applications in the fields of ultrafast measurement, wavelength-division-multiplexing optical communication, or high-precision photonic sampling. [ABSTRACT FROM AUTHOR]

On-chip ultra-wideband optical waveguide amplifiers are crucial for short-distance optical interconnections that utilize wavelength division multiplexing (WDM) technology. Silicon optical amplifiers still face significant challenges due to the indirect-band-gap nature and low rare earth solubility of silicon. This paper prepared a series of Er3+-Tm3+ co-doped La 2 O 3 –Al 2 O 3 glasses that are expected to be used in on-chip ultra-broadband optical waveguide amplifiers by aerodynamic levitation (ADL) technique, and further studied their luminescence characteristics and energy transfer process. Research results indicate that the glass composition 5Er 2 O 3 -0.6Tm 2 O 3 -43.4La 2 O 3 –51Al 2 O 3 is an optimal optical waveguide amplifier host material due to its excellent luminescence properties and ultra-broadband flat photoluminescence spectrum extending up to 440 nm. Moreover, positive gain can be obtained with a population ratio greater than 0.2, which further illustrates its feasibility as a matrix material for ultra-broadband optical waveguide amplifiers. The advancement of this material is expected to significantly aid in the fabrication and progress of next-generation ultra-wideband optical waveguide amplifiers. [ABSTRACT FROM AUTHOR]

Full-colour-sorting metalens using few nanostructured layers have recently generated considerable interest as high-sensitivity colour image sensors because of their reliability and high resolution. Based on the guided mode resonance principle and propagation phase modulation, a full-colour-sorting metalens is designed, which can theoretically obtain any wavelength of light from the incident white light and realize arbitrary wavelength focusing with the same focal length in the visible range. Without the loss of generality, we propose a prototype of such metalens used for sorting blue, green and red light from the visible spectrum commonly used in practical applications. The maximum focussing efficiency is over 50% with a relatively high numerical aperture of 0.7. The proposed full-colour-sorting metalens can be used in many applications, such as colour mixing, colour holography, colour filtering, wavelength division multiplexing and so on. [ABSTRACT FROM AUTHOR]

This paper presents a study of a 32×10 Gbps Radio over Fiber and Wavelength Division Multiplexing (RoF-WDM) full-duplex system that uses Phase Modulators and a Dual-Port Mach-Zehnder Modulator (PMs-DPMZM) for bidirectional data transfer. The system employs Millimeter-Wave (MMW) signaling over optical fiber and focuses on selecting a technology that provides high transmission capacity per wavelength, improved spectral efficiency, and resistance against optical transmission impairments. The proposed method was validated using simulation results to confirm the efficiency of the proposed system in generating a 40 GHz signal and efficiently detecting and modulating the RF signals. The results demonstrate that the system exhibits strong resistance against dispersion, non-linear effects, and noise, delivering satisfactory performance for distances of up to 220 km. By analyzing the input power, the paper establishes a relationship between input power and signal quality, revealing that an optimal power of 0 dBm leads to an improved Quality Factor (QF) and reduced transmission errors. Furthermore, the evaluation of received optical power indicates the power level required to maintain an acceptable error rate, approximately -20.9690 dBm for downstream data transfer and -20.7245 dBm for upstream data transfer at the BER limit. The simulation performance also demonstrates the transmission efficiency achieved through a high Polarization Mode Dispersion (PMD) coefficient of up to 0.8. The analytical calculations conducted in this work provide valuable insights for optimizing and enhancing the performance of RoF-WDM networks.

The forthcoming wireless networks must integrate to a high density of end-user devices while ensuring a superior quality of service. It is imperative to devise solutions that reduce the density of wireless access points and associated costs, while simultaneously ensuring security and privacy throughout propagation. Herein, a novel dual-band photodetector with high selective responsivities in distinct visible and near-infrared (NIR) band is developed as an optical signal receiver. The receiver has an unprecedented fast switch speed > 500 kHz between different operation modes. Leveraging this fast switch speed, a high-speed Multiple-Input-Single-Output (MISO) system is developed, fusing spectrum resources from visible to infrared bands. The system achieves a data rate of 600 Kbps in the visible channel and 500 Kbps in the NIR channel, with a sum rate of 1.1 Mbps. This is the highest single-channel data rate and sum rate among reported dual-band photodetectors. Additionally, two previously overlooked mechanisms, the Subtraction and Addition modes, are studied in detail. The four operation modes are developed to establish a novel physical encryption method in terms of arithmetic relation. The dual-channel coupled link can support a data rate of 200 Kbps, significantly enhancing communication security. [ABSTRACT FROM AUTHOR]

High speed motors are widely used in industrial applications owing to their unique features, such as compact framework, high performance, and high reliability. Based on the finite volume method and numerical heat transfer theory, this study establishes a stator-air gap-rotor model, and the flow and heat transfer in the air gap between the stator and rotor in a high speed motor are investigated with high pressure natural gas as the cooling medium. Meanwhile, the "radial tri-vortex partition, alternating axial distribution" feature of the turbulent Taylor-Couette vortex in the air gap of the motor is determined. Then, the optimal structural parameters which can realize the heat transfer enhancement of motor air gap are obtained. Finally, an optical fiber grating temperature measurement system based on the wavelength division multiplexing technology is utilized to attain the temperature distributions on the stator and rotor surfaces. The simulation results are compared with the experimental data to evaluate the simulation method's precision. [ABSTRACT FROM AUTHOR]

Photonic radar, a cornerstone in the innovative applications of microwave photonics, emerges as a pivotal technology for future Intelligent Transportation Systems (ITS). Offering enhanced accuracy and reliability, it stands at the forefront of target detection and recognition across varying weather conditions. Recent advancements have concentrated on augmenting radar performance through high-speed, wide-band signal processing–a direct benefit of modern photonics' attributes such as EMI immunity, minimal transmission loss, and wide bandwidth. Our work introduces a cutting-edge photonic radar system that employs Frequency Modulated Continuous Wave (FMCW) signals, synergized with Mode Division and Wavelength Division Multiplexing (MDM-WDM). This fusion not only enhances target detection and recognition capabilities across diverse weather scenarios, including various intensities of fog and solar scintillations, but also demonstrates substantial resilience against solar noise. Furthermore, we have integrated machine learning techniques, including Decision Tree, Extremely Randomized Trees (ERT), and Random Forest classifiers, to substantially enhance target recognition accuracy. The results are telling: an accuracy of 91.51%, high sensitivity (91.47%), specificity (97.17%), and an F1 Score of 91.46%. These metrics underscore the efficacy of our approach in refining ITS radar systems, illustrating how advancements in microwave photonics can revolutionize traditional methodologies and systems. [ABSTRACT FROM AUTHOR]

The Compact Morpho‐Molecular Microscopy (CM3) is proposed and demonstrated for multi‐functional imaging and characterization of living cells and material structures by simultaneously offering quantitative phase imaging (QPI), dispersion characterization, and fluorescence imaging. The compactness and stability of CM3 are realized by propagating lasers of different wavelengths in specially treated optical fibers and fiber‐based beam splitters and wavelength division multiplexers, as well as simplifying the detection scheme through Fourier‐space multiplexing and implementing a single camera for both QPI and fluorescence imaging. Quantitative phase maps of two wavelengths are retrieved from a multiplexed interferogram, and a synthesized wavelength phase map is derived to guide the height profiling of samples with extended depth. With the wavelength resolved phase maps, a physical model is derived to obtain sample dispersion parameters, which further enables us to quantify the hemoglobin concentration of red blood cells in real time. By inserting an appropriate emission color filter, fluorescence imaging is realized using the same camera, which significantly broadens the cell imaging applications of CM3. As a cost‐effective and multifaceted imaging method, CM3 may find many promising applications in live‐cell imaging and material characterization. [ABSTRACT FROM AUTHOR]

This paper presents a 4-channel demultiplexer totally based on a two-dimensional photonic crystal with silicon air holes and defects with the advent of a graphene sheet, in multiplexing systems that use Dense Wavelength Division Multiplexing. Methods that incorporate Plane Wave Expansion and finite difference time domain are used, as they have significant efficiency to generate the photonic hollow modes of the demultiplexer and analyze the global distribution and transmission, respectively. Parameters of transmission overall performance, maximum quality factor, spectral width, crosstalk, and channel spacing of the demultiplexer are very important statistics to confirm the overall performance of the device, whose values are about 92%, 1944.3, 0.9 nm, − 60 dB and 0.1 nm, respectively, whose consequences are problem to the validation of the requirements of the Dense Wavelength Division Multiplexing device (ITU.G.694.1). The proposed demultiplexer includes a bus or linear waveguide with graphene to guide the slight wave and 4 resonant cavities wherein graphene is placed withinside the center to select out the wavelength in a hexagonal lattice form of dielectric air holes in air. The bus waveguide transmits slight into the resonant hole area and exits through the respective falling waveguide. [ABSTRACT FROM AUTHOR]

In this paper, a novel technique to mitigate the effects of Four Wave Mixing (FWM) in Dense wavelength division multiplexing (DWDM) Radio over Fiber (RoF) system is introduced. Using Offset Quadrature Phase Shift Keying (OQPSK) modulation, the FWM effect in an 8-channel DWDM system is mitigated to a great extent. With a data rate of 10 Gbps per channel, this system can provide a total capacity of 80 Gbps. The performance of this system is compared with different modulation techniques such as Non-return-to-zero (NRZ), Duobinary, Modified Duobinary, Alternate mark inversion (AMI) and Integrated-alternate mark inversion (I-AMI). Performance analysis is done using FWM power, FWM efficiency, optical signal-to-noise ratio (OSNR), received power, bit error rate (BER) and eye diagrams. A comparative analysis of the proposed system is also done with other previously published works. The results prove that the proposed OQPSK system is superior in mitigating FWM effect with better performance. [ABSTRACT FROM AUTHOR]

Wavelength selective switches (WSSs) are essential elements for wavelength division multiplexing (WDM) optical networks, as they offer cost-effective, high port-count and flexible spectral channel switching. This work proposes a new hybrid WSS architecture that leverages the beam shaping and steering features of uniform silicon nitride-based end-fire optical phased arrays (OPAs). By introducing beamforming to a WSS system, the spectral channels on the liquid crystal on silicon (LCoS) panel can be tailored and arranged properly, depending on the optical configuration, using the beam control capabilities of OPAs. Combining 3D-FDTD and ray tracing simulations, the study shows that, by reducing the input beam dimensions with proper sizing of the OPAs, the WSS design with a null-steering OPA layout and 4 × No switch size features increased spectral resolution. This extensive beamforming study on the steering-enabled layout reveals the acquirement of an even higher input channel number, matching the 8 × No WSS scheme, with flexible channel routing on the LCoS panel. Such implementation of beamsteerers can unlock an extra degree of freedom for the switching capabilities of hybrid WSS devices. The results show great promise for the introduction of OPAs in WSS systems and provide valuable insight for the design of future wireless communication links and WDM systems. [ABSTRACT FROM AUTHOR]

Several types of silicon-nanowire-based optical demultiplexers (DeMUXs) for use in short-reach targeted datacenter applications were proposed and their spectral responses were experimentally verified. First, a novel 100-GHz-spaced 16λ polarization-diversified optical DeMUX consisting of 2λ delayed interferometer (DI) type interleaver and 8λ arrayed waveguide gratings will be discussed in the spectral regimes of C-band, together with experimental characterizations showing static and dynamic spectral properties. Second, a novel 800-GHz-spaced 8λ optical DeMUX was targeted for use in LR (long reach) 400 Gbps Ethernet applications. Based on multiple cascade-connected DIs, by integrating the extra band elimination cutting area, discontinuous filtering response was analytically identified with a flat-topped spectral window and a low spectral noise of <−20 dB within an entire LR-8 operating wavelength range. Finally, a 20-nm-spaced 4λ coarse wavelength division multiplexing (CWDM)-targeted optical DeMUX based on polarization diversity was experimentally verified. The measurement results showed a low excessive loss of 1.0 dB and a polarization-dependent loss of 1.0 dB, prominently reducing spectral noises from neighboring channels by less than −15 dB. Moreover, TM-mode elimination filters were theoretically analyzed and experimentally confirmed to minimize unwanted TM-mode-oriented polarization noises that were generated from the polarization-handling device. The TM-mode elimination filters functioned to reduce polarization noises to much lower than −20 dB across the entire CWDM operating window. [ABSTRACT FROM AUTHOR]

Topological photonic crystals have great potential in the application of on-chip integrated optical communication devices. Here, we successfully construct the on-chip transmissible topological edge states using one-dimensional Su–Schrieffer–Heeger (SSH) photonic crystals with defect cavities on silicon-on-insulator slab. Different coupling strengths between the lateral modes and diagonal modes in photonic crystal defect cavities are used to construct the SSH model. Furthermore, two photonic SSH-cavity configurations, called α and β configurations, are designed to demonstrate the topological edge states. Leveraging the capabilities of photonic crystal transverse electric modes with on-chip transmission, we introduced a waveguide to excite a boundary defect cavity and found that the transmission peak of light, corresponding to the topological edge state, can be received in another boundary defect cavity, which is caused by the tunnel effect. Moreover, the position of this peak experiences a blue shift as the defect cavity size increases. Therefore, by tuning the size of the SSH defect cavity, on-chip wavelength division multiplexing function can be achieved, which is demonstrated in experiments. The ultrafast response time of one operation can be less than 20 fs. This work harmonizes the simplicity of one-dimensional SSH model with the transmissibility of two-dimensional photonic crystals, realizing transmissible on-chip zero-dimensional topological edge states. Since transmission peaks are highly sensitive to defect cavity size, this configuration can also serve as a wavelength sensor and a reconfigurable optical device, which is of substantial practical value to on-chip applications of topological photonics. [ABSTRACT FROM AUTHOR]

This research investigates the integration of free-space optics (FSO) with fiber Bragg grating (FBG) sensors in self-healing ring architectures, aiming to improve reliability and signal-to-noise ratio in temperature sensing within sensor systems. The combination of FSO's wireless connectivity and FBG sensors' precision, known for their sensitivity and immunity to electromagnetic interference, is particularly advantageous in demanding environments such as aerospace and structural health monitoring. The self-healing architecture enhances system resilience, automatically compensating for failures to maintain consistent monitoring capabilities. This study emphasizes the use of intensity wavelength division multiplexing (IWDM) to manage the complexities of increasing the multiplexing number of FBG sensors. Challenges arise with the overlapping spectra of FBGs when multiplexing several sensors. To address this, a hybrid approach combining an unsupervised autoencoder (AE) with a convolutional neural network (CNN) is proposed, significantly enhancing the accuracy and efficiency of sensor signal detection. These advancements signify substantial progress in sensor technology, validating the effectiveness of the AE-CNN hybrid model in refining FBG sensor systems and underscoring its potential for robust and reliable applications in critical sectors. [ABSTRACT FROM AUTHOR]

In the present work, orthogonal frequency division multiplexing (OFDM) is combined with wavelength division multiplexing-passive optical networks (WDMPONs) to obtain the combined benefits of both technologies for overall system improvement. performance of five OFDM signals using WDM is analyzed. An optical system is designed using the OFDM signal, and its performance is analyzed using various matrices like bit error rate (BER) and Q-factor under the effect of varying laser power. Mapping of OFDM signals is done using 16-QAM modulation. The system shows an enhancement in the performance by increasing the laser power but up to some limit, and efficient results are obtained in the 70–130 mW laser power range. [ABSTRACT FROM AUTHOR]

This paper focused on the novel design of receiver side of wavelength division multiplexing passive optical network (WDM-PON). It serves the need for a dramatic change in demand for high data rate beyond 10 gigabits per second (Gbps) at the last mile for a larger coverage area or distance. This increase in demand for higher bandwidth is due to the emerging future technologies like Internet of things (IoT), silicon on chip (SoC), cloud computing, machine learning (ML), and artificial intelligence (AI). Simulation results demonstrated for the different coverage areas which compare the bit error rate (BER), quality (Q)-Factor, and eye height as per the guidelines of ITU-T. It has been predicted that the proposed WDM-PON design supports up to a distance of 60 km. Results have been verified for 40 km, 50 km, 60 km, and 70 km, respectively, at 100 GHz frequency spacing with acceptable BER and better quality (Q)-factor as defined by ITU. [ABSTRACT FROM AUTHOR]

Four‐Wave Mixing (FWM) is one of the non‐linear phenomena affecting long‐reach communication systems and high bandwidth. Research communities use simulation tools for parameter optimization. Unfortunately, such a simulation is time‐consuming and requires more time as the number of channels increases. This paper proposes two fast implementations of Dense Wavelength Division Multiplexing (DWDM) system, limited by FWM and the intrinsic Amplified Spontaneous Emission (ASE) noise of optical amplifiers employed in each segment. Additionally, this work compares the efficiency and speed improvement of the proposed parallelization model versus an earlier sequential model. We present the computational complexity analysis of sequential and parallel models. The paper considers two different parallel implementations: a multicore processor using Open MultiProcessing (OpenMP) and Compute Unified Device Architecture (CUDA), which is based on the use of a Graphics Processing Unit (GPU). Results show that parallelism using CUDA improves by up to 70 times the simulation performance compared to the sequential model. Parallelism with CUDA is up to 15 times compared to OpenMP using 12 logical processors. It is possible to simulate an increased number of channels within our parallel execution, which was impractical in the sequential simulation. [ABSTRACT FROM AUTHOR]

The operation of a four-channel multiplexer, utilizing multimode interference (MMI) wavelength division multiplexing (WDM) technology, can be designed through the cascading of MMI couplers or by employing angled MMI couplers. However, conventional designs often occupy a larger footprint, spanning a few millimeters, thereby escalating the energy power requirements for the photonic chip. In response to this challenge, we propose an innovative design for a four-channel silicon nitride (Si3N4) MMI coupler with a compact footprint. This design utilizes only a single MMI coupler unit, operating within the O-band spectrum. The resulting multiplexer device can efficiently transmit four channels with a wavelength spacing of 20 nm, covering the O-band spectrum from 1270 to 1330 nm, after a short light propagation of 22.8 µm. Notably, the multiplexer achieves a power efficiency of 70% from the total input energy derived from the four O-band signals. Power losses range from 1.24 to 1.67 dB, and the MMI coupler length and width exhibit a favorable tolerance range. Leveraging Si3N4 material and waveguide inputs and output tapers minimizes light reflection from the MMI coupler at the input channels. Consequently, this Si3N4-based MMI multiplexer proves suitable for deployment in O-band transceiver data centers employing WDM methodology. Its implementation offers the potential for higher data bitrates while maintaining an exemplary energy consumption profile for the chip footprint. [ABSTRACT FROM AUTHOR]

Magnetic Weyl semimetal shows intriguing properties in both fundamental physics and potential applications. However, the complex relationship between nonreciprocal transmission and magnetic field manipulation in magnetic Weyl semimetal systems has not been generally clarified and fully utilized. Here, a universal Chirality–Wavevector–Magnetic field (C‐K‐B) relation is established in the magnetic Weyl semimetal system, which completely describes the spin topological band and its intrinsic polarization output in full space orientation under an arbitrary magnetic vector. This relation can provide complete guidance for the device design of nonreciprocal spin manipulation. Coupling this nonreciprocal mechanism with the photonic spin Hall effect of the geometric phased metasurface, a magnetic Weyl semimetal metasurface is constructed in the terahertz (THz) range, The experiments demonstrate the flexible THz beam steerings in a broad spatial dispersion range of ±25–±55° with four different working modes by only altering the biased magnetic vectors. Moreover, all these beam steering processes are accompanied by nonreciprocal isolating transmission with the isolation ratio reaching 27 dB. This C‐K‐B relation and active nonreciprocal beam steering devices are expected to prompt magneto‐optical devices and systems combined with echo isolation function in beam scanning, wavelength division multiplexing, and spin multiplexing. [ABSTRACT FROM AUTHOR]

In this paper, a spectrally efficient silicon photonics phase‐diverse direct‐detection receiver based on asymmetric self‐coherent detection is proposed. The receiver is hardware efficient and composed of only two photodiodes and two analog‐to‐digital channels to accurately recover complex double‐sideband signals by leveraging an optimized integrated silicon racetrack resonator with near‐ideal phase responses. Moreover, the periodicity of the resonator response enables the receiver to support multi‐channel transmission such as dense wavelength‐division multiplexing. The receiver circuit is fabricated and characterized. In 40‐km transmission experiments, a record net electrical spectral efficiency of 7.10 bit s−1 Hz−1 per wavelength and per polarization is achieved, where a net 208‐Gb s−1 32QAM transmission is demonstrated using 29.3‐GHz electrical bandwidth. Furthermore, the receiver achieves net 220‐Gb s−1 16QAM transmissions in 14 channels from 1527 to 1550 nm with 205‐GHz spacing, and a maximum 240‐Gb s−1 net capacity at a single channel. Such a performance is reached with only standard coherent digital signal processing stacks including all‐linear equalization. [ABSTRACT FROM AUTHOR]

The utilization of Free Space Optical (FSO) systems in upcoming 5G or beyond systems is appealing due to its secure transmission, unlicensed spectrum, and higher information rate. Despite the various advantages of the FSO system, long-range communication transmission is inadequate because the effectiveness of FSO systems is significantly impaired by environmental phenomena such as scintillation, fog, haze, and rain. This research intends to improve the FSO module's effectiveness in terms of channel capacity and long-range communication. The present research has employed a hybrid technique that integrates multiple-beam, Erbium-doped fiber amplifier amplification and Homodyne detection methodologies within a wavelength division multiplexing FSO system to achieve the desired outcome. The channel model employed in this study is the Gamma–Gamma model, and the framework is evaluated using various strategies including single beam (SB1 × 1), four beams (MB4 × 4), and eight beams (MB8 × 8). The findings indicate that optimal performance has been achieved through the utilization of MB8 × 8. A channel capacity of 320 Gb/s has been observed across a range of 1.6–12 km, with variations in transmission distance attributed to external environmental factors. The link effectiveness is evaluated through the calculation of the Bit Error Rate, Q factor and Eye Height analysis. [ABSTRACT FROM AUTHOR]

In ITU-T standards, auxiliary management and control channels (AMCCs), as defined, facilitate the rapid deployment and efficient management of wavelength division multiplexing passive optical network (WDM-PON) systems. The super-imposition of an AMCC introduces additional interference to a PON signal, resulting in the degradation of the performance of the overall transmission. In prior research, we proposed employing a Gaussian mixture model (GMM) to fit a baseband-modulated AMCC signal. Following the analysis of the interference model and the distribution characteristics of received signal errors, we propose a combined optimization method for a transmitter and receiver in this paper. This method, grounded in probabilistic shaping (PS) techniques, optimizes the probability distribution of the transmitted signal based on the AMCC interference model, with the objective of reducing the error rate in PON signal transmission. We have validated this approach within a 50G-PON experimental system by utilizing PAM4 modulation. The experimental results demonstrate the effectiveness of this method for mitigating the impact of baseband-modulated AMCC, thereby reducing the error rate in PON signal transmission. The approach presented in this paper can further minimize the performance degradation introduced by baseband-modulated AMCC in WDM-PON systems, enhancing the efficiency of WDM-PON deployment. [ABSTRACT FROM AUTHOR]

High‐dimensional multiplexing technology is of importance in the on‐chip photonic interconnections and challenging to design within ultracompact footprint. Herein, high‐dimensional demultiplexers are proposed and demonstrated to enable wavelength‐division and mode‐division simultaneously. The functional regions of digital metamaterials are obtained by inverse design individually and are cascaded to work as high‐dimensional demultiplexers. The gradient‐based inverse design is carried out with an efficient method combining finite‐element method, density method, and method of moving asymptotes. The performances are simulated by 3D finite difference time domain with silicon‐on‐insulator configuration. The proposed demultiplexer with four‐channel has ultracompact footprint of 4.1 × 3.65 μm2. Its average transmission efficiency is 38.7% and contrast ratios are higher than 13.0 dB. Besides, the proposed demultiplexer with six‐channel has a footprint of 4.55 × 5.55 μm2. Its average transmission efficiency is 24.3% and contrast ratios are higher than 11.8 dB. [ABSTRACT FROM AUTHOR]

In this paper, we use new extended generalized Kudryashov and improved tan (ϑ 2) expansion approaches to investigate Kerr law nonlinearity in the extended Gerdjikov–Ivanov equation in a dense wavelength division multiplexed system. These methods rely on a traveling wave transformation and an auxiliary equation. These approaches successfully extract trigonometric, rational and hyperbolic solutions, along with some appropriate conditions imposed on parameters. To explain the dynamics of soliton profiles, a graphical description of newly discovered solutions is also presented, which exhibits distinct physical significance. The considered methods are recognized as useful and influential tools for creating solitary wave solutions to nonlinear problems in the mathematical sciences. [ABSTRACT FROM AUTHOR]

This study presents an innovative inline metasurface design for selective wavelength transmission and focusing. When integrated into optical fibers, it improves the stability and compatibility with techniques like wavelength division multiplexing and phase modulation. Precise parameters, determined through analytical calculations and simulations, allow for the design of multifunctional lenses within the optical fiber platform. The numerical results demonstrate unmodulated transmission for specific wavelengths, while others exhibit standing wave focusing with a 0.67 μm beam radius and a 0.31 μm depth of focus. This technology holds promise for applications in quantum experiments, sensing, and optical communication. [ABSTRACT FROM AUTHOR]

This study proposes and presents a new central office (CO) for the optical metro access network (OMAN) with an affordable and distinctive switching system. The CO's foundation is built upon a novel optical multicarrier (OMC) generation technique. This technique provides numerous frequency carriers that are characterized by a high tone-to-noise ratio (TNR) of 40 dB and minimal amplitude excursions. The purpose is to accommodate multiple users at the optical network unit side in the optical metropolitan area network (OMAN). The OMC generation is achieved through a cascaded configuration involving a single phase and two Mach Zehnder modulators without incorporating optical or electrical amplifiers or filters. The proposed OMC is installed in the CO of the OMAN to support the 1.2 Tbps downlink and 600 Gbps uplink transmission, with practical bit error rate (BER) ranges from 10−3 to 10−13 for the downlink and 10−6 to 10−14 for the uplink transmission. Furthermore, in the OMAN's context, optical fiber failure is a main issue. Therefore, we have proposed a possible solution for ensuring uninterrupted communication without any disturbance in various scenarios of main optical fiber failures. This demonstrates how this novel CO can rapidly recover transmission failures through robust switching a and centralized OLT. The proposed system is intended to provide users with a reliable and affordable service while maintaining high-quality transmission rates. [ABSTRACT FROM AUTHOR]

An enhanced transmission is presented in a multiple‐input‐multiple‐output (MIMO) dense‐wavelength division multiplexed (DWDM) free‐space‐optical (FSO) communication link using diversity coding techniques under the effect of turbulent weather phenomenon. The findings show good performance with an (8 channels × 2.5 Gbps data rate/channel) 20 Gbps 1500 m transmission distance. The bit‐error‐rate (BER), outage probability (OP), and signal‐to‐noise ratio (SNR) of the diversity combining techniques using maximum‐ratio combining (MRC), selection combining (SC), and equal‐gain combining (EGC) technique are evaluated in this work. The obtained results illustrate that Alamouti, space‐time coding (STC), space‐time block coding (STBC), space‐time trellis code (STTC), orthogonal STBC (O‐STBC), and quasi‐orthogonal STBC (QO‐STBC) on the minimum mean‐square‐error, and MRC are worth implementing on the DWDM‐FSO wireless communication systems. The mitigation of atmospheric turbulence is achieved using MIMO diversity combining techniques coding. The simulation results for diversity coding techniques using QO‐STBC/STTC and SC/MRC in the MIMO‐DWDM FSO communication system can improve BER performance, OP, and SNR. The MRC exhibits the lowest OP and BER when compared with the SC and EGC. The numerical results demonstrate that the FSO communication link using DWDM QO‐STBC/STTC improves the power penalty at both BER values under varying atmospheric turbulence conditions for ST, MT, and WT, in comparison to FSO systems without DWDM QO‐STBC/STTC diversity coding techniques. [ABSTRACT FROM AUTHOR]

A novel non-volatile optical filter with a large bandwidth (BW) and extinction ratio (ER) tunability is first experimentally demonstrated by introducing an all-optical phase change of Ge2Sb2Te5 (GST). The Si-GST hybrid device promises flexible multi-level regulation of essential filter parameters in an ultra-compact footprint of 30 μ m × 13 μ m. Ultra-low power consumption is realised on account of the saving of external static power that is required in other electric-optic or optic-optic-driven filters. The GST is loaded onto two triple-waveguide directional couplers located at the coupling regions of an add-drop microring resonator. By initiating the GST phase transition with pump optical pulses, the transmitted optical power to the cross port of the triple-waveguide coupler is adjustable, hence influencing the coupling efficiency states of the microring filter. Consequently, a tunable on-off ER from 0.7 dB to 18.2 dB and a tunable BW from 0.6 nm to 3.3 nm are experimentally obtained with the aid of optically manipulating the crystallization degree of GST. Our device potentially enables the realisation of high-density photonic integrated circuits, especially in dense wavelength division multiplexing networks. [ABSTRACT FROM AUTHOR]

Optical domain–wall (DW) solitons have attracted considerable attention for their special applications in wavelength-division multiplexing and signal processing in optical communications. In this study, we construct a dispersion-managed fiber laser with a composite filtering effect composed of nonlinear polarization rotation (NPR) filtering and Lyot filtering for achieving dual-wavelength domain–wall dark–bright pulses. Our optical-domain dark–bright pulse is characterized by even, though it has two optical wavelength components, still has the same repetition frequency. The phenomenon of dual-wavelength dark and bright pulses occurs by adjusting the composite filtering, and the dark and bright pulses can be separated by continuing the filtering. Our work presents a novel approach to achieve dual-wavelength domain–wall dark–bright pulses. [ABSTRACT FROM AUTHOR]

This article studies the Gerdjikov-Ivanov equation with Kerr law nonlinearity in dense wavelength division multiplexed systems and establishes new chirped optical solitons. The approaches used are trial equation method and the complete discriminant system for polynomial method, which are rigorously mathematically derived and calculated, rather than based on certain conditional assumptions. As a result, we obtain nineteen exact solutions and corresponding chirps whose types and quantities are more abundant than existing results, and the outcomes give the equation more profound physical significance. We give the topological stability analysis of the parameters of the solutions. Finally, we draw three-dimensional and two-dimensional graphs of modules of exact solutions and their chirps to verify the existence of solutions and understand their characteristics by taking specific parameters. [ABSTRACT FROM AUTHOR]

On-chip optical dispersion compensation and wavelength division multiplexing/demultiplexing (WDM) are highly demanded functions for optical communications. In this work, we proposed a multichannel dispersion compensation structure based on chirped multimode grating within a counter-directional coupler (CMG-CDC). Simultaneous wavelength division multiplexing and demultiplexing can be realized within a compact footprint. A device design for four-channel CMG-CDC at the C/L (1530–1565 nm) band is presented with a channel spacing of 20 nm assisted by a grooved multimode waveguide structure. The average dispersion for all channels is about −2.25 ps/nm with a channel bandwidth of about 3.1 nm. The device is highly compact and highly scalable, which makes it rather convenient for increasing the group velocity dispersion (GVD) and channel number, indicating flexible applications for versatile systems, including typically coarse wavelength division multiplexer four-lane (CWDM4) transceivers. [ABSTRACT FROM AUTHOR]

In today's world, optical fiber networks are susceptible to numerous cyber-attacks and conventional key distribution techniques that are limited by the growing computational power. By introducing Quantum Key Distribution (QKD) into optical networks, it is possible to leverage existing fiber infrastructures and apply wavelength division multiplexing (WDM) for effective secret key deployments to improve optical-layer security. Security is a major challenge during key exchange in QKD, at that same time restricted number of network resources also have a big concern recently. Thus a wavelength resources as well as security enhancement is performed through Time Continuous Compactness (TCC) based wavelength allocation algorithm with African Vulture Optimization (AVO) based BB84 protocol for quantum keys distribution. In this model, the dual secret key assembly is done through the KP (Key pool) and VKP (Virtualization Key Pool) assembly for storing the data in the SDN server, which can be accessed later using the user authentication. The data from the sender is encrypted using the AES-RC4 algorithm for transmitting to the receiver at the data channel. This designed model is evaluated and compared with the existing model based on the parameters such as key generation and eavesdropping rate. The attained key generation and eavesdropping rate (64 byte) of the proposed AVO-QKD model is 0.41 s and 0.45 Bps/Hz. These attained values of the proposed model are greater than the existing model. Thus, the Dual Secret Key virtualization through TCC based Wavelength Allocation and BB84 protocol in QKD over Optical Networks secures and allocates resources better than other techniques. [ABSTRACT FROM AUTHOR]

In this paper, a 40 GHz wavelength division multiplexing communication system-based optical frequency comb generator (WDM–OFCG) is design and investigated via OptiSystem software. The proposed design produced up to 25 channels with constant channel spacing of 40 GHz and average power of –10.84 dBm. The generated comb is spread over approximately 8 nm, ranging from 1546.17 to 1553.85 nm. In addition, the generated comb is employed as a multiwavelength laser source to carry information with a bit rate of 375 Gbps over a 120 km link distance. This represents an efficient evaluation to the proposed design since the achievable bit rate product repeater distance (BL) is about 45,000 (Gbps.km). [ABSTRACT FROM AUTHOR]

The evolution of Internet and communication systems is exponentially increasing the complexity in communication networks. This paved the way for the incorporation of artificial intelligence (AI), machine learning (ML), and recently deep learning (DL), in various aspects so as to improve the intelligence in communication networks. As DL techniques are superior on finding solutions to complex problems, they are been utilized for optical network applications. This paper aims to review the progress of AI in optical communication and the advancements from ML to DL. The paper also presents a review of nine research papers that utilized conventional DL techniques along with their contribution in optical and wavelength division multiplexing (WDM) networks. Toward the end of this paper, the DL algorithm is studied and its performance parameters are compared to evaluate the simulation outputs of its variants. The comparative analysis shows that in future, improvements in the outputs of WDMs can be made by applying DL-based algorithms. [ABSTRACT FROM AUTHOR]

Objective In recent years, there has been an explosive growth in data communication traffic. To address the demands for high-speed, high-capacity data transmission and the diversification of network application scenarios, 100 Gbit/s and Beyond (B100 Gbit/s) Dense Wavelength Division Multiplexing (DWDM) hybrid networking has gradually gained attention as an efficient solution. This paper conducts an analysis of the requirements, key technologies, and practical case studies of B100 Gbit/s DWDM hybrid networking to provide technical support and guidance for constructing high-capacity and efficient communication networks. Methods This paper first elucidates the requirements for the development of B100 Gbit/s DWDM hybrid networks, including the need for network capacity expansion and support for complex network architectures. Next, it focuses on introducing the key technologies of B100 Gbit/s DWDM hybrid networking, including constellation shaping, spectrum shaping, and flexible grid techniques. To support bitrate design in hybrid networking, a method for Optical Signal-to-Noise Ratio (OSNR) calculation in cascaded Erbium-Doped Fiber Amplifier (EDFA) communication systems is presented, utilizing parameters such as channel configuration information, signal optical power after transmitter, gain and noise parameters of EDFAs, to progressively calculate the output OSNR for each wavelength along the entire link. Finally, in conjunction with a foreign network case study and based on actual OSNR evaluation findings, a rational hybrid rate network design is performed, demonstrating the practical application of B100 Gbit/s DWDM hybrid networking in engineering projects. Results By employing B100 Gbit/s DWDM hybrid network, after flexibly configuring transmission rates and bandwidths according to OSNR evaluations, the deployment of hybrid rate networks at 200, 600 and 800 Gbit/s is achieved. This approach fulfills the high-capacity requirements of core sites while accommodating the long-distance, extensive span requirements of edge sites. Furthermore, network upgrades and expansion were smoothly accomplished within a three-year period. Conclusion Empirical evidence demonstrates that B100 Gbit/s DWDM networking effectively enhances network capacity, flexibility, and spectrum resource utilization. Moreover, it provides room for the continuous evolution of the networks, serving as a vital methods to advance the development of high-capacity optical transmission networks. [ABSTRACT FROM AUTHOR]