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Hong-Ou-Mandel (HOM) interference is the foundation of quantum optics to test the degree of indistinguishability of two incoming photons, playing a key role in quantum communication, sensing, and photonic quantum computing. Realizing high-visibility HOM interference with massively parallel optical channels is challenging due to the lack of available natural optical references for aligning independent arrayed laser pairs. Here, we demonstrate 50 parallel comb-teeth pairs of continuous-wave weak coherent photons HOM interference using two independently frequency post-aligned soliton microcombs (SMCs), achieving an average fringe visibility over 46%. The frequencies of all comb-teeth pairs are long-term aligned by developing two sets of fully frequency-stabilized SMCs with independent reference and adjusting free spectral range beyond 100 kilohertz through perturbations in soliton state. The verification experiment proves the feasibility of constructing massively quantum information channels by co-opting classical wavelength division multiplexing optical communications, which paves the way for practical large-scale quantum communication systems. [ABSTRACT FROM AUTHOR]

To solve the problems of low detection efficiency and inability to adapt to distributed measurement in traditional detection methods, a water temperature field detection system based on a fiber Bragg grating string was designed. In this system, six fiber Bragg gratings with different center wavelengths are connected in series on a single fiber optic cable based on wavelength division multiplexing technology. The fiber Bragg grating string is encapsulated in stainless steel tube and vertically fixed in the measured water body of the fish pond. The space division multiplexing technology is employed to collect information from multiple fiber Bragg grating strings. Water temperature measurement experiments were conducted in the summer pond environment. The experimental results show that the daily variation curve of temperature in each water layer of the fish pond is relatively smooth and approximates a cosine function with a 24-hour period. In summer, the daily average water temperature in the pond is no more than 1°C higher than the average air temperature. The difference between the maximum and the minimum water temperature is approximately 2°C. During the daytime, the temperature gradually decreases from the surface to the deeper water layers, whereas at night, the temperature variation among the water layers is minimal. As depth increases, the amplitude of the water temperature curve oscillations gradually decreases, exhibiting exponential decay. However, the peak time gradually lags behind. There is a correlation between the temperatures of the water layers in the fish pond, and the smaller the distance between the water layers, the stronger the correlation. The experimental results obtained in this study are highly significant for real-time services in aquatic planting and aquaculture. Additionally, this measurement method can provide valuable reference and guidance for measuring temperature fields in other fluids. [ABSTRACT FROM AUTHOR]

The (1+1)-dimensional fractional coupled nonlinear Schrödinger equations (FCNLSEs) are investigated in this work. This model is important as it involves applications in allowing soliton wavelength division multiplexing and pulse propagation in two-mode optical fibers. This means it is important for the study of the dynamics of solitons in dispersive, inhomogeneous, nonlinear media, and, therefore, it is a tool of prime value for the development of advanced optical communication technologies. Beta space-time fractional derivative, which is important in dielectric polarization and electromagnetic systems, is used to evaluate the FCNLSE. We capitalize a modified version of the Sardar sub-equation method for the purpose of getting different soliton solutions. Solutions take the form of optical solitons, including dark, bright, periodic, peakons, compactons, and kink soliton solutions, formulated using exponential, trigonometric, and hyperbolic functions. To make our understanding of the physical meaning of these solutions richer, we apply advanced plotting techniques, examples of which are the three-dimensional (3D), two-dimensional (2D), contour, and density plots. Such plots provide a colorful overview of the dynamic behavior of the solutions obtained. The solutions do not only pinpoint the fact that the result is an effective and accurate method application, but they also set a high standard in further probing meaning in the numerous physical phenomena. These new solutions go beyond earlier studies in the literature by incorporating beta derivatives as a modeling tool for FCNLSE. The methodology applied here functions seamlessly and can be extended to address numerous advanced models in contemporary areas of science and engineering. The anticipated usefulness of the derived solutions in various scientific domains, particularly optics, is expected to make a valuable contribution to the fiber communication system in future research endeavors. [ABSTRACT FROM AUTHOR]

We demonstrated the coexistence of an S-band CV-QKD signal with fully loaded C+L-band classical signals for the first time. The secret key rate of the S-band QKD system was 986 kbps with the C+L-band WDM signals transmitted through a 20 km G.654.E fiber link. We also revealed that the S-band CV-QKD performance limiting factor under the C+L-band WDM condition is the spontaneous Raman scattering light similar to the C-band CV-QKD performance limiting factor, confirming the validity of estimating the wavelength dependency of the secret key rate under the WDM condition from the fiber loss and the spontaneous Raman scattering light power. These results show that the CV-QKD performance under the C+L band WDM conditions becomes comparable to that under the C-band WDM conditions by wavelength design in the S-band. [ABSTRACT FROM AUTHOR]

This paper compares and discusses two different types of Wavelength Division Multiplexing (WDM) Passive Optical Network (PON) configuration. First is with Semiconductor Optical Amplifier (SOA-WDMPON) and second is with Erbium Doped Fiber Amplifier (EDFA-WDM-PON). The performance of the system is measured by calculating Bit Error Rate (BER) for various values of bitrate and length of fiber. The novelty of the paper is that the results are obtained for higher bitrate up to 30 Gbps and higher fiber lengths up to 80 Km. Compared to previously published results this paper tries to achieve good BER and Q-factor. WDM-PON with four channels is designed, incorporating SOA and EDFA amplifiers to achieve optimized gain and noise performance. Unlike previous studies, this paper integrates recent innovations, such as quantum dot SOA and tunable EDFA, into a practical design that addresses critical challenges in high-speed optical networks, including scalability, signal integrity, and costeffectiveness. The importance of this paper is reflected in its comprehensive overview of stateof-the-art developments and its applicationoriented approach, offering valuable insights for optimizing optical amplification technologies for modern and future communication networks. [ABSTRACT FROM AUTHOR]

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This work addresses the tailoring spectral response of grating-assisted co-directional couplers (GADCs) in the context of wavelength filtering for fiber-to-the-home (FTTH) applications. Design methods for spectral response engineering by means of coupling profile apodization-type weighting techniques and also more advanced rational transfer functions fitting a predefined spectral window template are presented. Modeling results based on coupled mode theory are then applied for the design and experimental fabrication of InGaAsP/InP GADCs targeting 1.3+/1.3− µm diplexer application in FTTH access networks. The experimental results are found to be in good agreement with the modeling predictions. The design tools presented are quite general and can be easily adapted to other technology platforms, such as silicon photonics for the use of GADCs as add-drop wavelength division multiplexers. The field of parity–time symmetry is another avenue where these types of gain–loss-assisted GADCs as active components are of interest for switching applications, and the design methods presented here may find utility. [ABSTRACT FROM AUTHOR]

To achieve high data rate, futuristic wavelength division multiplexing passive optical network (WDM-PON) has pursued due to capability of multiplexing individual wavelength. This paper illustrates the possibility of different data rates along with distance to solve the challenges for next-generation WDM-PON systems. It is superior to present PON design due to rapid progress in different passive components for access network. In this paper, recent progress such as 20 Gb/s (gigabits per second) to 80 Gbps. WDM-PON technology has been carried out. Due to recent development in PON systems, demonstration of 80 Gbps (10 Gbps per wavelength * 8) based WDM-PON system with simplified and optimized design for last mile is presented. The simulation results have been compared to demonstrate the effect of the results achieved. At last, better quality (Q)-factor of 3.46, low value of BER (bit error rate) i.e., 2.48 × 10−11 with reach of 80 km whereas high value of Q-factor of 22.16, eye height of 4.75 and BER of 3.61 × 10−10 has achieved successfully using WDM-PON system. [ABSTRACT FROM AUTHOR]

A system is represented that uses 20 nm of channel spacing and unequal channel spacing along with four different types of transmission fibers on subcarrier multiplexing–wavelength division multiplexing (SCM/WDM) based radio over fiber (RoF) link. These five different kinds of fibers have been analyzed offering different propagation parameters. In case of 20 nm of channel spacing the performance of the link is improved by 35.32% with the use of True wave fiber. In this paper, 8 channel SCM–WDM based RoF based model is simulated and analyzed with different type of optical fibers covering distance of 10 km. A comparison of Q-factor at different optical power and different optical lengths has been made. Q-factor, bit error rate and eye diagrams have been examined for assessing the performance of the model. [ABSTRACT FROM AUTHOR]

In recent times, there has been enormous growth in internet-based applications such as online entertainment platforms, video conferencing and voice over internet protocol (VoIP) applications which might be the trend in future. In order to support such bandwidth-hungry applications, the speed of the network should be enhanced. Increasing the infrastructure of the network requires heavy investment. Another alternative to increase the capacity of the network is to use dense wavelength division multiplexing (DWDM) which also results in increased costs as the lasers and other equipment needed for generation of wavelengths are required. In this work, an alternative cost effective technique is used to create a DWDM scenario using optical flat comb source (OFCS) by combining amplitude modulator (AM) and single drive mach zehnder modulator (SD-MZM). The spectral lines generated using this procedure can be used in Passive Optical Network (PON) as input sources. In this paper, 51 flat spectral lines are generated and transported over a distance of 100 km which are also capable of supporting a data rate of greater than 10 Gbps in a single spectral line. [ABSTRACT FROM AUTHOR]

This research focuses on the integration of an opto-satellite system based on Free Space Optical Communication (OWC) within DVB-RCS2 chains, implementing 16-QAM modulation techniques and Optical Time Division Wavelength Multiplexing (OTDMWDM). A co-simulation framework combining the MATLAB and OptiSystem environments is adopted to evaluate the system's performance. Key performance indicators, such as Bit Error Rate (BER) and Q factor, are meticulously analyzed to quantify the effectiveness of the proposed approach. The results obtained demonstrate notable improvements in transmission reliability and signal quality, highlighting the potential of OWC to optimize DVB-RCS2 standards. This study significantly contributes to the development of innovative solutions in the field of satellite communications, paving the way for more efficient and resilient systems. [ABSTRACT FROM AUTHOR]

Wavelength division multiplexing (WDM) is one of the emerging technologies for data transmission in 5G access network assembly between the antenna unit (AU) and the distribution unit (DU). Here, in this work, we evaluate and analyze a dense wavelength division multiplexing (DWDM) — passive optical networks (PONs) employing erbium–ytterbium-doped fiber amplifier (EYDFA) + Raman hybrid optical amplifier (HOA) using two modulation schemes — modified duobinary return to zero (MDRZ) and differential phase shift keying (DPSK) for alternate channels, where the channel count has been varied from 8 to 40. The system has been analyzed over the wavelength span of 1550–1558.8 nm with a channel spacing, input power and data rate of 25 GHz, 0 dB and 40 Gb/s, respectively. An average gain, gain ripple and optical signal-to-noise ratio (OSNR) of 20.87, 0.95 and 30 dB, respectively have been observed in the case of HOA along with the achievement of Q-factor of up to 9 at the receiving end of the system. The DPSK-modulated channels result in higher values of gain and OSNR along with lower gain ripple as compared to MDRZ channels making the proposed system a good option for 5G access network applications. [ABSTRACT FROM AUTHOR]

In this paper, the theoretical model of spontaneous Raman scattering (SpRS) in few-mode fiber (FMF) is discussed. The influence of SpRS on quantum key distribution (QKD) in FMF is evaluated by combining wavelength division multiplexing (WDM) and space division multiplexing (SDM) techniques. On this basis, an improved ring-assisted FMF is designed and characterized; the transmission distance can be increased by up to 54.5% when choosing different multi-channels. The effects of forward and backward SpRS on QKD are also discussed. [ABSTRACT FROM AUTHOR]

In dispersion-managed links with mid-span spectral inversion (MSSI) systems, the symmetry of the cumulative dispersion profile is important for compensating the distorted wavelength division multiplexing (WDM) signals. The triangular dispersion map has antipodal symmetry with respect to the midway optical phase conjugator (OPC). A triangular dispersion map is proposed in this paper that has a singularity in which the lengths of the optical fibers that contribute to forming the cumulative dispersion profile are determined randomly. We analyzed three types for randomly determining and deploying the length of optical fibers to form the triangular dispersion map. We confirmed that triangular dispersion maps combined with MSSI systems are more advantageous for distorted WDM channel compensation than traditional uniform dispersion maps are. In particular, the dispersion map created via the “random-inverse” scheme, which randomly arges the optical fiber lengths of each span before the midway OPC while reversing the arrangement of the optical fiber lengths in the sections after the midway OPC, results in the best compensation. [ABSTRACT FROM AUTHOR]

The rapid increase in Internet usage has led to a growing demand for bandwidth. Optical microring resonators (MRRs) are emerging as a promising solution to meet this need. MRRs generate optical frequency combs (OFCs) that provide multiple wavelengths with high phase coherence, enabling communication via wavelength division multiplexing (WDM). Spectrum allocation methods, such as the Routing, Modulation Level, and Spectrum Assignment (RMLSA) approach, play a crucial role in executing this strategy efficiently. While current algorithms have improved allocation efficiency, further development is necessary to optimize network performance. This paper presents an integer linear programming (ILP)-based method for network resource allocation, aiming to maximize the number request and the bandwidth assigned to each. The proposed approach offers a flexible cost function that prioritizes system constraints such as transmission distance and bandwidth requirements, resulting in significant improvements to the bandwidth blocking rate (BBR). By integrating multilevel modulation and using wavelengths generated by MRRs, this method efficiently handles up to 1075 requests, achieving a BBR of zero. This dynamic and adaptable allocation strategy ensures optimal resource utilization, enhancing overall network performance. [ABSTRACT FROM AUTHOR]

【Objective】The Array Waveguide Grating Router (AWGR) constructed in the form of an N×N matrix has optical parallelism and wavelength routing capabilities. It can simultaneously transmit N signals on different channels, and has advantages of good scalability, low latency, and wide bandwidth. Combined with tunable harmonic light sources, it can achieve fast optical switching, which is one of the potential technical solutions for the next generation of optical switching data center networks. In order to solve the problems of high crosstalk, additional coupling loss, polarization sensitivity, and non-uniformity of existing AWGR that may affect practical applications, this paper studied AWGR with 4×4 channels and 12×12 channels respectively to further expand the scale of data centers and improve the data exchange speed.【Methods】The basic design parameters were calculated using simulation software, and the AWGR design process was analyzed and studied. The Beam Propagation Method (BPM) was used for simulation. At the same time, performance optimization is carried out by adding a conical waveguide tap structure at the connection between the flat waveguide and the strip waveguide, increasing the spacing between the input and output waveguides.【Results】The simulation results show good performance parameters: 4×4 AWGR insertion loss of -0.714 dB, crosstalk of -35.556 dB, loss non-uniformity of 1.907 dB; 12×12 AWGR insertion loss of -0.294 dB, crosstalk of -36.019 dB, loss non-uniformity of 3.428 dB. The designed device chips are then fabricated and tested on the optical platform. The test results indicate: 4×4 AWGR insertion loss of -2.586 dB, crosstalk of -29.473 dB, loss non-uniformity of 1.921 dB; 12×12 AWGR insertion loss of -3.692 dB, crosstalk of -23.874 dB, loss non-uniformity of 3.873 dB.【Conclusion】This article investigates the performance optimization in areas such as crosstalk and non-uniformity of losses, accumulating experience for subsequent design iterations and further improving the performance parameters.

Ring resonators are crucial in silicon photonics for various applications, but conventional designs face performance trade‐offs. Here a third‐order polynomial interconnected circular (TOPIC) bend is proposed to revolutionize the ring designs fundamentally. The TOPIC bend has a unique feature of continuous curvature and curvature derivative, which is theoretically derived to be essential for waveguide loss optimization. With the TOPIC bend, the silicon ring resonators demonstrated here have achieved three records to the best of our knowledge: the smallest radius (0.7 μm$\mathrm{\mu m}$) for silicon rings resonating with single guided mode, the lowest thermal tuning power (5.85 mW/π${\pi}$) for silicon rings with FSR≥${\rm FSR}\ge$3.2 THz, and the first silicon ring‐based WDM 32×$\mathrm{\times }$100 GHz filter. The filter has doubled the channel amount compared to the state of the art, and meanwhile achieved low insertion loss (1.91 ±$\pm$ 0.28 dB) and low tuning power (283 GHz mW−1${\rm mW}^{-1}$). Moreover, the TOPIC bend is not limited to ring applications, it can also be used to create bends with an arbitrary angle, with the advantages of ultra‐compact radius and heater integration, which are expected to replace all circular bends in integrated photonics, greatly reducing system size and power consumption. [ABSTRACT FROM AUTHOR]

Quantum clock synchronization (QCS) can measure out the high-precision clock difference among distant users, which breaks through the standard quantum limit by employing the properties of quantum entanglement. Currently, the wavelength division multiplexed QCS network has been demonstrated with a spontaneous parametric down-conversion entangled photon source. In this paper, we propose a more efficient QCS network scheme with the wavelength multicasting entangled photon source, which can decrease at least 25% of wavelength channel consumption under the identical network scale. Afterwards, a four node QCS network is demonstrated, where the wavelength multicasting entangled photon source is utilized with dual-pumped four-wave mixing silicon chip. The experimental results show that the measured time deviation is 3.4 ps with an average time of 640 s via the multiple fiber links of more than 10 km. [ABSTRACT FROM AUTHOR]

An eight‐channel local‐area‐network wavelength division multiplexing silicon photonic transceiver is designed within a 5 mm × 5 mm chip area. This integrated chip is composed of a set of perfectly vertical grating couplers, interleaved angled‐MMI wavelength division (de)multiplexers, silicon E‐O modulators, and germanium waveguide photodetectors. The multiplexer exhibits an IL of (4.5–5.8) dB and average crosstalk ≈−20 dB. Due to the limited bandwidth of the 2‐D GC, the IL of the demultiplexer is 5.17 dB at minimum, with a channel nonuniformity of 5.53 dB. The EO modulator and germanium waveguide PD exhibit 3‐dB bandwidths of 45 and 47 GHz, respectively. With a customized fiber array packaged, a back‐to‐back data transmission capacity of 1.56 and 1.42 Tb/s with BERs below the SD‐FEC limit is demonstrated for the transmitter and receiver, respectively. By connecting the transmitter and receiver, the dynamic performance of the transceiver chip is characterized, and the total data capacity of eight wavelength channels is 1.18 Tb/s. To show the advantage of transmission distance, 2 and 10 km SMF transmission experiments are also carried out. Through close integration with matched electronic circuits, the data capacity of this transceiver chip can be potentially boomed to 1.6 Tb/s. [ABSTRACT FROM AUTHOR]

Near‐infrared II (NIR‐II, 900–1880 nm) fluorescence confocal microscopy offers high spatial resolution and extensive in vivo imaging capabilities. However, conventional confocal microscopy requires precise pinhole positioning, posing challenges due to the small size of the pinhole and invisible NIR‐II fluorescence. To simplify this, a fiber optical wavelength division multiplexer (WDM) replaces dichroic mirrors and traditional pinholes for excitation and fluorescence beams, allowing NIR‐IIb (1500–1700 nm) fluorescence and excitation light to be coupled into the same optical fiber. This streamlined system seamlessly integrates key components—excitation light, detector, and scanning microscopy—via optical fibers. Compared to traditional NIR‐II confocal systems, the fiber optical WDM configuration offers simplicity and ease of adjustment. Notably, this simplified system successfully achieves optical sectioning imaging of mouse cerebral blood vessels up to 1000 µm in depth. It can discern tiny blood vessels (diameter: 4.57 µm) at 800 µm depth with a signal‐to‐background ratio (SBR) of 5.34. Additionally, it clearly visualizes liver vessels, which are typically challenging to image, down to a depth of 300 µm. [ABSTRACT FROM AUTHOR]

Nowadays, as the ever-increasing demand for more powerful computing resources continues, alternative advanced computing paradigms are under extensive investigation. Significant effort has been made to deviate from conventional Von Neumann architectures. In-memory computing has emerged in the field of electronics as a possible solution to the infamous bottleneck between memory and computing processors, which reduces the effective throughput of data. In photonics, novel schemes attempt to collocate the computing processor and memory in a single device. Photonics offers the flexibility of multiplexing streams of data not only spatially and in time, but also in frequency or, equivalently, in wavelength, which makes it highly suitable for parallel computing. Here, we numerically show the use of time and wavelength division multiplexing (WDM) to solve four independent tasks at the same time in a single photonic chip, serving as a proof of concept for our proposal. The system is a time-delay reservoir computing (TDRC) based on a microring resonator (MRR). The addressed tasks cover different applications: Time-series prediction, waveform signal classification, wireless channel equalization, and radar signal prediction. The system is also tested for simultaneous computing of up to 10 instances of the same task, exhibiting excellent performance. The footprint of the system is reduced by using time-division multiplexing of the nodes that act as the neurons of the studied neural network scheme. WDM is used for the parallelization of wavelength channels, each addressing a single task. By adjusting the input power and frequency of each optical channel, we can achieve levels of performance for each of the tasks that are comparable to those quoted in state-of-the-art reports focusing on single-task operation. We also quantify the memory capacity and nonlinearity of each parallelized RC and relate these properties to the performance of each task. Finally, we provide insight into the impact of the feedback mechanism on the performance of the system. [ABSTRACT FROM AUTHOR]

We numerically demonstrate the dispersion map configured by random-based residual dispersion per span (RDPS) applied into the mid-span spectral inversion (MSSI) system to mitigate the impact of chromatic dispersion and the fiber nonlinearity in wavelength division multiplexed (WDM) signals. The dispersion map proposed was a scheme in which the RDPS of all optical fiber spans in the front section of the midway optical phase conjugator (OPC) are randomly selected, and the arrangement order of the RDPS in the rear section is inverted from that of the front section. Numerical simulations were performed by evaluating the compensation of the distorted 960 Gb/s WDM signal as a function of the variation of the DCF length and the SMF length, which are involved in determining RDPS. It was confirmed that the compensation effect of the proposed dispersion maps has improved compared to the conventional dispersion map since the dispersion maps examined in this paper have antipodal symmetry around the midway OPC. In particular, it was confirmed that the method of randomly determining the RDPSs by varying the DCF length slightly improved system performance compared to the variation of SMF lengths. We also found that the feature of the RDPS random distribution patterns can achieve excellent compensation for the distorted WDM signal through 50 iterations. [ABSTRACT FROM AUTHOR]

Compared with high spectrum efficiency faster-than-Nyquist (FTN) backbone network, an enhanced carrier phase recovery based on dual pilot tones is more sensitive to capital cost in FTN metropolitan areas as well as inter-datacenter optical networks. The use of distributed feedback (DFB) lasers is a way to effectively reduce the cost. However, under high symbol rate FTN systems, equalization-enhanced phase noise (EEPN) induced by a DFB laser with large linewidth will significantly deteriorate the system performance. What is worse, in FTN systems, tight filtering introduces inter-symbol interference so severe that the carrier phase estimation (CPE) algorithm of the FTN systems is more sensitive to EEPN, thus it will lead to a more serious cycle slip problem. In this paper, an enhanced carrier phase recovery based on dual pilot tones is proposed to mitigate EEPN and suppress cycle slip, in which the chromatic dispersion (CD)-aware Tx and LO laser phase noise is estimated, respectively. Offline experiments results under 40 Gbaud polarization multiplexing (PM) 16-quadrature amplitude modulation (QAM) FTN wavelength division multiplexing (FTN-WDM) systems at 0.9 acceleration factor, 5 MHz laser linewidth, and 500 km transmission demonstrate that the proposed algorithm could bring about 0.65 dB improvement of the required SNR for the normalized generalized mutual information of 0.9 compared with the training sequence-based cycle slip suppression carrier phase estimation (TS-CSS) algorithm. [ABSTRACT FROM AUTHOR]

The work presents a brief introduction of fiber optical sensors and focuses on multiparameter grating sensor for measurements of strain, temperature, pressure, acceleration, etc. Two-channel and three-channel fiber Bragg grating (FBG) are designed and simulated using MOD-Grating software, and the reflectivity obtained is 64.8% and 90%, respectively, for both the channels. A wavelength division multiplexed (WDM) optical data transmission system based on fiber Bragg gratings can be developed using the simulation model's precise and accurate results. The total reflectivity of two-channel optical fiber is 64.8%. In the three-channel FBG, reflectivity of fiber increases from 85 to 90%. The grating sensors are passive elements with two main attributes that are electromagnetic interference (EMI) and multiplexing capability. The presented work gives novel applications of FBG in wavelength division multiplexed optical network. Our design parameters will be helpful for manufacturing and setting up communication channel link in industrial applications in more efficient way. [ABSTRACT FROM AUTHOR]

The exponential growth of data from sensors and internet‐connected devices has challenged traditional electronic computing, particularly in processing speed and power efficiency. Optical information processing, with its inherent high speed and parallelism, offers a promising solution. Moreover, optical processing is vital for developing all‐optical networks, where all‐optical imaging is essential. In this paper, a novel all‐optical imaging technique that leverages in situ anion exchange reactions between perovskite nanocrystals to create an array of pixels with tunable emission wavelengths is proposed. This method enables the conversion of UV light, whether transmitted or reflected by an object, into the visible spectrum, thereby establishing a direct correlation between spectral and spatial information. By employing wavelength division multiplexing (WDM), the approach reduces the dimensionality of information acquisition from two dimensions to one, enhancing imaging speed. This innovation paves the way for significant advancements in all‐optical imaging and image processing, offering new possibilities for faster and more efficient imaging technologies. [ABSTRACT FROM AUTHOR]

With the increasing amount of data in railway communication system, the conventional wireless high-frequency communication technology cannot meet the requirements of modern communication and needs to be improved. In order to meet the requirements of high-speed signal processing, a high-speed communication signal processing method based on visible light is developed and studied. This method combines the adaptive equalization algorithm with deep learning and is applied to railway communication signal processing. In this research, the wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM) techniques are used, and fuzzy C equalization algorithm is used to softly divide the received signals, reduce signal distortion and interference suppression. The experimental results showed that increasing the step size could reduce the equalization effect, while increasing the modulation parameter will increase the bit error rate. Through deep learning to achieve channel equalization, visible light communication could effectively mitigate multi-path transmission and reflection interference, thereby reducing the bit error rate to the level of 0.0001. Under various signal-to-noise ratios, the system using the channel compensation method achieved the lowest bit error rate. This outcome was achieved by implementing hybrid modulation scheme, including Wavelength division multiplexing (WDM) and direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) techniques. It has been proved that this method can effectively reduce the channel distortion when the receiver is moving. This study develops a dependable communication system, which enhances signal recovery, reduces interference, and improves the quality and transmission efficiency of railway communication. The system has practical application value in the field of railway communication signal processing. [ABSTRACT FROM AUTHOR]

Fiber optic communications have made great strides, and it is now the foundation of our telecommunications and data networking infrastructures. Due to its beneficial characteristics, including low attenuation, a large bandwidth, and immunity to electromagnetic interference, optical fiber is frequently acknowledged as a superior transmission medium. Optical fibers have been widely used to create high speed lines that can transmit either a single wavelength channel or many wavelength channels using wavelength division multiplexing due to their special features (WDM). The maximum speed of commercial fiber-optic cables was only 2.5 Gb/s and can be extended to 1 Tb/s for short and medium distance. The study clarifies the possible transmission distance for different transmission media silica/plastic optical fibers with various optical fiber window transmissions versus environmental ambient temperature variations. The study demonstrated the bad effects of the temperature effects on the optical fiber transmission media (silica/plastic fibers) for various transmission windows. [ABSTRACT FROM AUTHOR]

Today, in passive optical networks (PON) the major issue is call blocking and it is getting worse as there is an increase in the number of connection requests but the wavelength channels in fiber links are limited. In this research, greedy-based priority routing and wavelength assignment traffic grooming (GPRWATG) technique is proposed aimed at reducing call blockage. In this scheme, to avoid optical–electrical–optical correspondence, firstly the grooming of connection requests with same source destination (s–d) is performed. According to the priority of these groomed connection requests, wavelength assignment and routing is assigned. This approach not only addresses the call blocking issue but also aligns with industry demands for improved network infrastructure. The proposed work performance is analyzed for blocking probability (BP), congestion, and its performance is compared with the non-priority-based routing and wavelength assignment traffic grooming (NPRWATG) and priority-based routing and wavelength assignment traffic grooming (PRWATG) schemes. The proposed method has 23.6 % lower congestion as compared to PRWATG and 21 % lower congestion as compared to NPRWATG. Also, the BP of GPRWATG is 26 % less than PRWATG and 21 % less than NPRWATG. Thus, it can be analyzed that by using the proposed technique, the BP as well as the congestion of the network altogether is reduced in comparison to the existing state-of-art techniques. [ABSTRACT FROM AUTHOR]

An orthogonal frequency division multiplexed-radio over free space optics (OFDM-RoFSO) communication system with dual multiplexing is proposed. Eight input data streams are transmitted simultaneously by using wavelength division multiplexing (WDM) at level 1 and polarization division multiplexing (PDM) at level 2. Input data streams 1–4 and 5–8 are assigned with same set of carrier frequencies i.e. 193.1 THz, 193.3 THz, 193.5 THz and 193.7 THz and separate polarization levels (X and Y polarized) before transmitting through RoFSO link. A total data rate of 160 Gbps (4 × 2 × 20 Gbps) is achieved in this design. With proposed system, channel performance is evaluated under the influence of atmospheric attenuation and turbulence conditions while measuring system BER, Q-factor, SNR and received power etc. The effect of channel crosstalk is analysed for WDM-PDM dual multiplexed design while considering single input single output (SISO) and multiple input multiple output (MIMO) FSO configurations. The overall analysis predicts that a higher transmission rate and improved capacity levels can easily be achieved with dual multiplexed system. [ABSTRACT FROM AUTHOR]

In this article, the comb wavelength division multiplexing passive optical network (Comb WDM-PON) system has been simulated. Simulation models were created in VPI photonics. The proposed system employs 140 Gbps for seven comb lines. Analytical modelling and simulations are performed for a flat comb source with seven comb lines, variable channel spacing, and a center wavelength. As a result, the performance of the comb WDM-PON system that utilizes a single differential Mach–Zehnder (DiffMZ) modulator comb source is also investigated using different comb line numbers. The total capacity of the system increases as the number of comb lines increases. However, the system performance is degraded. Data rates of 80 Gbit/s can be achieved at the threshold bit error rate of BER (1 × 10−9), over a transmission distance of 200 km using 4 comb lines with a multi-diagonal (MD) code for 4 OLTs. [ABSTRACT FROM AUTHOR]

This paper is successfully demonstrated simulative comparison and investigation of 32 channels with 0.8 nm frequency spacing bidirectional wavelength division multiplexing passive optical network (WDM-PON) having 640 and 320 GB/s data rate in downstream and upstream transmission by using CRZ-DPSK/NRZ modulation formats respectively. The maximum reach of the system has been configured to 100 km by employing different post-dispersion compensation techniques such as EDC, DCF, OPC, and FBG in uplink and downlink transmission for compensate the effect of chromatic dispersion in propagating channel. An EDFA optical amplifier is placed after DCF for boosting the amplitude of weak signals downstream. Apart from this, the RSOA amplifier is installed at the ONT end for reflecting and re-modulates the same wavelengths to the CO terminal without using any external optical light source. The performance comparison of distinct compensation schemes are evaluated in terms of BER, Q factor, and Eye diagrams. It has been observed that the FBG and DCF are more robust compensation techniques as compared to EDC and OPC in the bidirectional WDM-PON. The maximum satisfying value of BER has been observed in downlink and uplink transmissions are 10−26 and 10−13 for FBG and DCF respectively. [ABSTRACT FROM AUTHOR]

This work outlined the integrated role between vertical cavity surface emitting laser diodes with Gaussian pulse generators and Ideal erbium doped fiber amplifier (EDFA) for the self-phase modulation instability management, as well as the signal/NP level (Power level [PL]) with the spectral frequency is simulated after wavelength division multiplexing (WDM) fiber at length of 10 km based third order Gaussian pulse generators. The light power variations against temperature after WDM fiber is also studied at length of 10 km based various order Gaussian pulse generators. Electrical received power (ERP) variations against temperature is clarified after avalanche photo diode (APD) photodetectors based various order Gaussian pulse generators. The study emphasis the bad effects of the increase of the temperature, and higher Gaussian pulse generators order on the signal power levels. [ABSTRACT FROM AUTHOR]

An all-optical crosstalk suppression scheme is desirable for wavelength and space division multiplexing optical networks by improving the performance of the corresponding nodes. We put forward a scheme comprising double-stage semiconductor optical amplifiers (SOAs) for wavelength-preserving crosstalk suppression. The wavelength position of the degenerate pump in the optical phase conjugation (OPC) is optimized for signal-to-crosstalk ratio (SXR) improvement. The crosstalk suppression performance of the double-stage SOA scheme for 20 Gb/s quadrature phase shift keying (QPSK) signals is investigated by means of simulations, including the input SXR range and the crosstalk wavelength deviation. For the case with identical-frequency crosstalk, the double-stage SOA scheme can achieve equivalent SXR improvement of 1.5 dB for an input SXR of 10 dB. Thus, the double-stage SOA scheme proposed here is more suitable for few-mode fiber systems and networks. [ABSTRACT FROM AUTHOR]

The multi-wavelength laser array is crucial for high-capacity silicon photonic systems based on (dense) wavelength division multiplexing technology. However, realizing 8-wavelength or more laser arrays is challenging solely by adjusting the grating period due to the large wavelength spacings of about 12–20 nm. In this letter, we report a 16-wavelength heterogeneously integrated quantum dot distributed feedback laser array with varying silicon waveguide width and grating period. The effective refractive index of gratings is calculated by eigenmode expansion method. Considering the power reflectivity, normalized coupling coefficient and manufacturing process of gratings, the etch depth and duty cycle of gratings are optimized to 10 nm and 0.8, respectively. When the grating period is fixed at 198 nm and the silicon waveguide widths are 560 nm, 590 nm, 615 nm, and 635 nm, respectively, the corresponding lasing wavelengths are 1310.72 nm, 1311.26 nm, 1311.80 nm, and 1312.31 nm, respectively, and the wavelength spacing of adjacent laser units is about 100 GHz (0.57 nm). Furthermore, by adjusting the grating period between 196 and 202 nm with 2 nm spacing of grating period, the number of lasing wavelengths is increased to 16, and the range of lasing wavelengths is broadened to 1298.03–1337.44 nm. This work provides an excellent solution for realizing multi-wavelength heterogeneously integrated III-V/Si distributed feedback laser arrays and expanding the number of wavelengths, thereby advancing the development of high-capacity silicon photonic systems. [ABSTRACT FROM AUTHOR]

Recent advancements in high-order topological insulators have heralded new opportunities for the innovation and utilization of optical devices. This paper presents a composite asymmetric C4 photonic crystal to achieve multifunctional, robust topological states. Through detailed analysis of the fine changes in the topological bandgap induced by distortion parameters, we facilitate the realization of topological edge states in wavelength division multiplexing applications. We utilize both trivial and nontrivial properties of the topological bandgap to precisely manipulate zero-dimensional angular states, one-dimensional topological boundary states, and two-dimensional body states. Through simulations and experimental results, our advanced asymmetric C4 photonic crystal structure demonstrates superior robustness for the transmission of topological edge states. Our research paves the way for the deployment of more robust topological boundary state transmission systems and advances the application potential of higher-order topological states. [ABSTRACT FROM AUTHOR]

In long-haul WDM (wavelength division multiplexing) optical communication systems utilizing the DP-16QAM modulation scheme, traditional methods for removing chaos have exhibited poor performance, resulting in a high bit error rate of 10 − 2 between the original signal and the removed chaos signal. To address this issue, we propose DeepChaos+, a machine learning-based approach for chaos removal in WDM transmission systems. Our framework comprises two key points: (1) DeepChaos+ automatically generates a dataset that accurately reflects the features of the original signals in the communication system, which eliminates the need for time-consuming data simulation, streamlining the process significantly; (2) it allows for the training of a lightweight model that provides fast prediction times while maintaining high accuracy. This allows for both efficient and reliable signal reconstruction. Through extensive experiments, we demonstrate that DeepChaos+ achieves accurate reconstruction of the original signal with a significantly reduced bit error rate of approximately 10 − 5 . Additionally, DeepChaos+ exhibits high efficiency in terms of processing time, facilitating fast and reliable signal reconstruction. Our results underscore the effectiveness of DeepChaos+ in removing chaos from WDM transmission systems. By enhancing the reliability and efficiency of chaotic secure channels in optical fiber communication systems, DeepChaos+ holds the potential to improve data transmission in high-speed networks. [ABSTRACT FROM AUTHOR]

This work addresses the optimized planning of survivable optical 5G Xhaul access networks employing passive Wavelength Division Multiplexing (WDM) technologies. Specifically, it focuses on the reliability of optical transmission paths connecting remote radio sites to a central hub ensured by using a novel, cost-effective, flexible, and dedicated path protection (DPP-F) scheme, protecting against single-link failures. The proposed DPP-F network protection approach allows for switching of individual wavelengths or the complete multiplexed WDM signal, flexibly applying the best switching option according to given traffic demands. Concurrently, it enables traffic aggregation on the transmission paths from the end and intermediate nodes to minimize the overall network deployment cost. The problem of selecting primary (working) and backup (protection) paths, together with the selection of the best switching and traffic aggregation options, is modeled and solved as a mixed-integer linear programming (MILP) optimization problem. To evaluate the cost savings achieved with DPP-F, we compare it with two reference DPP schemes based on switching the entire multiplexed WDM signal (DPP-M) and individual wavelengths (DPP-W). Numerical experiments conducted across a wide range of network scenarios reveal, among other things, that DPP-F's performance is at least as good as that of the reference methods, bringing significant cost savings (from several to tens of percent) in most of the analyzed network scenarios. [ABSTRACT FROM AUTHOR]

A dense wavelength division multiplexing (DWDM) system improves the capacity of an optical communication system. On the other hand, nonlinear effects are critical issues that limit the performance of the DWDM system. The nonlinear effects of self-phase modulation, cross-phase modulation, and four-wave mixing affect optical communication's capacity. This paper focuses on mitigating the nonlinear effect of cross-phase modulation in the DWDM system with a suitable technique. [ABSTRACT FROM AUTHOR]

Radio-over-fiber (RoF) is a technology in which radio frequency (RF) signals are distributed from central station to remote antenna units using fiber. Wavelength division multiplexing (WDM) is a technique in which different data streams are allowed to be sent parallely over a single fiber at different frequencies for increasing bandwidth. Hence, RoF combined with WDM technology is a prominent solution for many applications. In this article, we have designed an 8-channel 40 Gbps WDM-RoF system for future generation networks. The performance of the system has been evaluated using a simulator and then compared with a 4-channel existing system. A dispersion compensating fiber with a dispersion value at −85 ps/nm/km is used for combating nonlinearity. The simulated 8-channel WDM-RoF system has been analyzed by varying bit rate, input power, number of loops (transmission span), and channel spacing using performance parameters such as Q-factor and BER. It has been observed that the performance of the network improved as the channel spacing increased from 50 to 200 GHz. Moreover, the system performance is reliable up to 200 km. [ABSTRACT FROM AUTHOR]

Radio over fiber (ROF) is a very attractive technology for the increasing demand for flexibility and transmission capacity and due to its high bandwidth and low attenuation, it offers an economic advantage. The wavelength division multiplexing (WDM) is used to multiplex the different wavelengths signals within a single optical fiber. In this paper, WDM-ROF system is analysed with different filters using an optisystem. Results were compared using max Q factor, min BER, and eye height parameters. [ABSTRACT FROM AUTHOR]

Security postulates of visible light communication (VLC) is a paramount area of consideration due to its deployment in military, businesses, and residential establishments. Optical code division multiplexing (OCDMA) is prominent multiples access technique to serve multiple users and offer better security as compared to other available techniques such as wavelength and time division multiplexing (TDM). Wavelength conversion, multicode keying, optical logic gates, and quantum key distribution are some of the widely used security enhancement techniques but come at high cost and greater complexity. Zero cross correlation codes (ZCC) with integration of time dimension is an ultimate solution to the complex security improvement techniques but conventional two dimensional (2D) ZCC codes has an utmost issue of adjacent weights (W) and time (t) in the code which can be easily decoded by eavesdropper. Therefore, in this work, a novel weight managed ZCC (WMZCC) OCDMA code is presented with the non-adjacent W and t in the code matrix for making authentic information decoding difficult. Proposed 2D-WMZCC codes are investigated for 5 users at 100 Gbps over VLC link length of 5 m using polarization division multiplexed (PDM) quadrature phase shift keying (QPSK) and digital signal processing in terms of log symbol error rate (log SER), Q factor and bit error rate (BER). Further, a detailed comparison of 2D-WMZCC codes is performed with existing 2D diagonal identity matrix (DIM) codes and results revealed that former one exhibits better security than later OCDMA code. [ABSTRACT FROM AUTHOR]

FSO is the best communication medium for data transmission because of its high bandwidth, effective deployability and maximum transmission data rates with very high security. In this research paper an optical network model has been designed in the optisystem for different modulation schemes with WDM to enhance the capacity of the system. Attenuations for different weather conditions in Dehradun have been calculated and the performance has been evaluated accordingly. The performance is analysed in terms of BER (Bit Error Rate), maximum Q-factor, and eye height for each of the modulation schemes at different transmission distances and different weather attenuations. Analysis comprehends that the polarization shift keying is the best modulation technique for the WDM-FSO communication network among all. Thus, we suggest a model for an optical communication network using WDM and PolSK modulation scheme for Dehradun (Uttarakhand), where internet service is not very easy due to its extreme weather variations and got the excellent performance. [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]

Free space optical (FSO) systems offer an attractive and cost-effective solution for providing communication services in remote regions, as they allow secure transmission without the need for licensing and with lower deployment costs. However, the performance of FSO systems can be significantly impacted by atmospheric turbulences, creating considerable challenges to their deployment. To meet the expanding bandwidth requirements in optical networks, dense wavelength division multiplexing (DWDM) has emerged as a viable option. The development of a 400-Gbps DWDM-FSO system with advanced modulation formats is the subject of this paper. To ensure efficient energy conservation in such a system, power consumption needs to be minimized while maintaining performance level; this calls for optimization of different components within the system. The system is made up of 10 channels and each channel can transmit data at 40 Gbps. Various modulation schemes like carrier-suppressed return-to-zero, modified duo binary return-to-zero, differential phase shift keying, and duo binary return-to-zero are studied for their impact on system performance parameters Q-factor and bit error rate (BER) in C-band around 1550 nm wavelengths. The assessment is also extended to the effects that changing FSO length, input power, and data rate have on these two parameters as well as an evaluation regarding how differing atmospheric conditions influence the FSO system's effectiveness. [ABSTRACT FROM AUTHOR]

Summary Even with existing methodologies, dynamic resource allocation, service inconsistency, operational costs, and excess energy/power consumption in optical access networks remain the key challenges for the next‐generation passive optical network (NG‐PON) design and development. This paper introduces a novel method for analyzing energy/power consumption in time and wavelength division multiplexed (TWDM) passive optical networks (PONs) with a ring‐based topology. We propose subscriber‐based channel allocation models (CAMs) for on‐demand services, allocate bandwidth dynamically, and evaluate their downstream power consumption. To determine the necessary optical devices for the various CAMs, we investigate subscriber take‐up rates by optimizing the utilization of optical components based on active subscribers. Implementing a novel Poisson distribution‐based network traffic model addresses energy‐related concerns and explores optimization techniques to minimize power and improve energy efficiency. With a take‐up rate of 64 active subscribers, simulation results show significant power consumption reductions ranging from 62.2 to 67.7%, achieved by the proposed subscriber‐based architecture models with varying subscriber counts, when compared with the conventional model. The model with the most subscribers (2048 subscribers) saves the most energy by reducing power consumption to 292 W from the conventional model's (2048 subscribers) 440 W. Furthermore, the model with the most subscribers saves 33.4% of energy, outperforming other subscriber‐based architecture models without affecting QoS even during peak hours of the day. These numerical results show that TWDM‐PONs with the most subscribers exhibit improved energy efficiency than the conventional and other proposed subscriber‐based architecture models. [ABSTRACT FROM AUTHOR]