Wavelength Division Multiplexing Research Articles

Optimization and analysis of apodized fiber Bragg grating properties for quasi-distributed sensing

An apodized fiber Bragg grating (FBG) is introduced with a proposed apodization function for the effective quasi-distributed sensing estimation of the temperature and the strain. FBG features such as reflectivity, side lobes, and bandwidth have been optimized for the designed apodized grating to upgrade the effectiveness of FBG for properly measuring the variations in the Bragg wavelength. Based upon the simulation, a comparative analytical study on FBG properties with different apodization function profiles has been demonstrated to achieve the optimum profile with high reflectivity, narrow bandwidth and minimal range of side lobes for quasi-distributed sensing estimation of parameters. A strong linearity has been noted for the sensitivity of designed FBG with different apodization profiles for the temperature and the strain estimation subsequently. It has been reported that the obtained sensitivity of measurands for the FBG with proposed apodization profile are higher as compared with the other profiles. The wavelength division multiplexing (WDM) based quasi-distributed network of four optimized FBGs have been implemented for different apodization profiles to illustrate the impact of apodization to prevent overlapping between neighbouring FBG spectrums in the sensing network with spatial resolution of 2 nm. The maximal detectable temperature/strain sensitivity estimation of 153 °C/1439 μϵ have been obtained for the proposed apodized FBG along with minimal detectable temperature/strain ranges of −102 °C/−1345 μϵ in the quasi-distributed network. The achieved ranges with optimum resolution can be implemented effectively in quasi-distributed based sensing application for condition observation of civil infrastructures in any complex circumstances.

Wavelength detection of serial WDM ultra-short fiber Bragg grating sensor networks based on a CCD interrogator using deep belief networks and sparrow search algorithm

In this paper, in order to make fiber Bragg grating spectra easier to overlap, it is proposed to use ultra-short fiber Bragg grating to build a sensor network, and for serial wavelength division multiplexing (WDM) fiber Bragg grating (FBG) sensor networks using charge-coupled device (CCD) interrogator as data acquisition devices, an efficient method for measuring strain sensor signals is presented, which combines a deep belief network (DBN) with the sparrow search algorithm (SSA). The FBG sensor network uses serial WDM connectivity, negating the need for optical switches and reducing latency of the whole sensor system. The application of a low-precision, low-resolution CCD interrogator as the data acquisition device enhances the model's generalizability and facilitates its implementation in real-world projects. DBN, a generative graphical model in machine learning, for learning features from overlapping spectra of FBGs and build the center wavelength detection model. SSA is a swarm intelligence algorithm, for optimizing the hyperparameters of the DBN model. Experimental results show that even using spectral data collected by a CCD interrogator, the DBN-SSA model can achieve good demodulation accuracy and speed, with an optimal root mean square error of 1.68pm and a single inference time of 1.4 ms. In summary, the demodulation system offers a dependable and effective solution for FBG sensor networks with limited data precision.

Silicon‐photonic four‐mode triple‐band multiplexing device for hybrid wavelength/mode division multiplexing networks

SummaryWhile 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 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.

Arrayed electro-optic modulators for novel WDM multiplexing

In this paper, a novel silicon-on-chip integrated 4 × 1 wavelength division multiplexing (WDM) multiplexer has been developed. This is the first time that the multiplexer design incorporates arrayed electro-optical modulators with crosstalk cancellation. The design utilizes two types of electro-optic modulators in each channel. The first modulator, based on 1D-PhCNBC, extracts the desired wavelengths from the WDM spectrum. The second modulator, based on coupled hybrid plasmonics, acts as a switch to eliminate crosstalk of the desired optic wavelength signal at the multiplexer output. By combining the advantages of electro-optical modulators and crosstalk cancellation techniques, we anticipate that our proposed design contributes to the advancement of WDM multiplexing technology and facilitates the implementation of efficient and compact optical communication systems. Additionally, this synergy enables enhanced performance, reduced signal interference, and improved signal quality, leading to more reliable and high-speed data transmission in optical networks. The functionality of the device is theoretically simulated using 3D-FDTD (Finite-Difference Time-Domain) method.

Spatial and mode selective switch for orbital angular momentum mode division multiplexing.

In analogy to a wavelength selective switch in wavelength-division multiplexing (WDM) optical fiber communication systems, a spatial and optical mode selective switch (SMSS) would be an important component in future ultrahigh capacity optical fiber communication systems based on space and mode division multiplexing. In this work, a free-space SMSS for orbital angular momentum (OAM) mode-division multiplexing (MDM) is proposed and experimentally demonstrated. The SMSS consists of a separating part for transforming OAM modes to spatial modes and a recombining part for selecting and recombining the modes to any spatial channel. The SMSS is able to implement strictly non-blocking switching between a total of 36 SDM/MDM channels configured as four spatial channels each supporting nine OAM mode channels.

Physics to system-level modeling of silicon-organic-hybrid nanophotonic devices

The continuous growth in data volume has sparked interest in silicon-organic-hybrid (SOH) nanophotonic devices integrated into silicon photonic integrated circuits (PICs). SOH devices offer improved speed and energy efficiency compared to silicon photonics devices. However, a comprehensive and accurate modeling methodology of SOH devices, such as modulators corroborating experimental results, is lacking. While some preliminary modeling approaches for SOH devices exist, their reliance on theoretical and numerical methodologies, along with a lack of compatibility with electronic design automation (EDA), hinders their seamless and rapid integration with silicon PICs. Here, we develop a phenomenological, building-block-based SOH PICs simulation methodology that spans from the physics to the system level, offering high accuracy, comprehensiveness, and EDA-style compatibility. Our model is also readily integrable and scalable, lending itself to the design of large-scale silicon PICs. Our proposed modeling methodology is agnostic and compatible with any photonics-electronics co-simulation software. We validate this methodology by comparing the characteristics of experimentally demonstrated SOH microring modulators (MRMs) and Mach Zehnder modulators with those obtained through simulation, demonstrating its ability to model various modulator topologies. We also show our methodology's ease and speed in modeling large-scale systems. As an illustrative example, we use our methodology to design and study a 3-channel SOH MRM-based wavelength-division (de)multiplexer, a widely used component in various applications, including neuromorphic computing, data center interconnects, communications, sensing, and switching networks. Our modeling approach is also compatible with other materials exhibiting the Pockels and Kerr effects. To our knowledge, this represents the first comprehensive physics-to-system-level EDA-compatible simulation methodology for SOH modulators.

Turbidity-tolerant underwater wireless optical communications using dense blue–green wavelength division multiplexing

Underwater wireless optical communication (UWOC) has demonstrated high-speed and low-latency properties in clear and coastal ocean water because of the relatively low attenuation ‘window’ for blue–green wavelengths from 450 nm to 550 nm. However, there are different attenuation coefficients for transmission in ocean water at different wavelengths, and the light transmission more seriously deteriorates with fluctuations in the water turbidity. Therefore, traditional UWOC using a single wavelength or coarse blue–green wavelengths has difficulty tolerating variations in water turbidity. Dense wavelength division multiplexing (WDM) technology provides sufficient communication channels with a narrow wavelength spacing and minimal channel crosstalk. Here, we improve the UWOC in clear and coastal ocean water using dense blue–green WDM. A cost-effective WDM emitter is proposed with directly modulated blue–green laser diodes. Dense wavelength beam combination and collimation are demonstrated in a 20-metre underwater channel from 490 nm to 520 nm. Demultiplexing with a minimum channel spacing of 2 nm is realized by an optical grating. Remarkably, our WDM results demonstrate an aggregate data rate exceeding 10 Gbit/s under diverse water turbidity conditions, with negligible crosstalk observed for each channel. This is the densest WDM implementation with a record channel spacing of 2 nm and the highest channel count for underwater blue–green light communications, providing turbidity-tolerant signal transmission in clear and coastal ocean water.

Beam swinging coherent Doppler wind lidar utilizing wavelength switching through a single telescope.

We have developed a new, to the best of our knowledge, beam swinging coherent Doppler wind lidar (BS-CDWL) by employing a wavelength switching method using mass-produced components for wavelength division multiplexing (WDM) optical communication systems. This BS-CDWL also has a single and position-to-angle conversion telescope for multiple LOS measurement which contributes to cost-effectiveness. Preliminary wind sensing result is shown with measurable range of up to 350 m.

Wavelength Division Multiplexing in Visible Light Communications Using Fluorescent Fiber Antennas

Wavelength Division Multiplexing in Visible Light Communications Using Fluorescent Fiber Antennas

New design of all-optical multi-channel wavelength division multiplexer based on 2D PC waveguide structures with square rods

New design of all-optical multi-channel wavelength division multiplexer based on 2D PC waveguide structures with square rods

Full C- and L-band covered second-order OAM mode generator based on a thinned helical long-period fiber grating

A full C- and L-band covered second-order orbital-angular-momentum (OAM) mode generator has been proposed and experimentally demonstrated, which is realized by using a helical long-period fiber grating (HLPG) but inscribed in a thinned four-mode fiber. By optimizing the design of grating period and fiber diameter of the proposed HLPG, an ultra-broadband rejection filter with a depth of ∼23 dB, a bandwidth of ∼156 nm @-10 dB (ranging from 1522 nm to 1678 nm) and a bandwidth of ∼58 nm @-20 dB (ranging from 1574 nm to 1632 nm), has been successfully obtained as a typical sample. To the best of our knowledge, this is the first demonstration of such ultra-broadband second-order OAM mode generator by using only one fiber component, i.e., the thinned HLPG. In addition, the proposed generator is less polarization-dependent and less temperature-sensitive than those of the conventional HLPGs, which is believed to be considerably helpful to find potential applications of the device itself in wavelength division multiplexing (WDM) and OAM mode division multiplexing (MDM) optical fiber communication systems.

Enhancing the performance of mode-pairing quantum key distribution by wavelength division multiplexing

Mode-pairing quantum key distribution (MP-QKD) holds great promise for the practical implementation of QKD in the near future. It combines the security advantages of measurement device independence while still being capable of breaking the Pirandola–Laurenza–Ottaviani–Banchi bound without the need for highly demanding phase-locking and phase-tracking technologies for deployment. In this work, we explore optimization strategies for MP-QKD in a wavelength-division multiplexing scenario. The simulation results reveal that incorporation of multiple wavelengths not only leads to a direct increase in key rate but also enhances the pairing efficiency by employing our novel pairing strategies among different wavelengths. As a result, our work provides a new avenue for the future application and development of MP-QKD.

Multipoint temperature measurement system composed of fiber-optic Fabry–Perot interference sensors and a wavelength-division multiplexing filter

A multipoint optical-fiber remote temperature measurement system was developed using reflection-type sensors consisting of a Fabry–Perot interference (FPI) structure with good temperature characteristics combined with a wavelength-division multiplexing (WDM) filter. The FPI sensor was fabricated using a short temperature-sensing region sandwiched between single-mode fibers. FPI optical fibers and a WDM filter functioned as the temperature sensors and wavelength-selective optical source using an amplified spontaneous emission light source, respectively. This system was operated in a dense WDM configuration using an arrayed waveguide wavelength filter.

Design and performance analysis of OAM‐based multidimensional multiplexing RoF‐PON integrated access system

AbstractThe unique advantage of orbital angular momentum (OAM) provides a novel approach to breaking through the limitations of high‐capacity and long‐distance transmission in the conventional radio‐overfiber passive optical network (RoF‐PON) hybrid access network. Introducing the OAM division multiplexing (OAM‐DM) based on Laguerre–Gaussian (LG) beams into the RoF‐PON, an innovative multidimensional system architecture is proposed, which integrates with polarization‐division multiplexing (PDM), wavelength‐division multiplexing (WDM), and orthogonal frequency‐division multiplexing (OFDM) technologies. Successful long‐distance transmission of both the downstream 40 GHz radio OFDM signal and the upstream 40 Gbps on‐off keying (OOK) signal over 80 km are achieved. Additionally, at the optical network unit side, low‐cost upstream carrier re‐modulation technology and flexible access for both wired and wireless signals are realized. The proposed RoF‐OAM‐DM‐PDM‐WDM‐OFDM‐PON architecture offers a dependable solution for high‐capacity and low‐cost future communication systems, holding great importance in achieving flexible access networks.

Dense Wavelength Division Multiplexing (DWDM) in IT Networks: A Leap Beyond Synchronous Digital Hierarchy (SDH)

The evolution of telecommunications has seen significant milestones, notably the shift from Synchronous Digital Hierarchy (SDH) to Dense Wavelength Division Multiplexing (DWDM). This transition marks a pivotal advancement in the performance of Information Technology (IT) networks, offering unparalleled improvements in bandwidth, scalability, and efficiency. DWDM technology enables the simultaneous transmission of multiple data streams across a single optical fiber by using different wavelengths of light, significantly enhancing data throughput and network capacity. This article delves into the technical foundations of DWDM, compares its performance enhancements over SDH systems, and explores its impact on modern IT network infrastructure.

Cost minimization of multi-class demands groomed over multi-rate OTN interfaces considering WDM-layer constraints

This paper introduces a practical comprehensive approach to optimize the cost of installed Optical Transport Network (OTN) interfaces, as well as the required number of wavelengths in the substrate Wavelength Division Multiplexing (WDM) optical network. The approach assumes grooming variable-bit-rate traffic demands on multi-rate OTN interfaces. We propose an Integer Linear Programming (ILP) formulation to address the combined problem of OTN interface deployment, virtual-network formation, traffic grooming on the established distinct-capacity virtual paths, and virtual network embedding on the WDM physical substrate. The presented model focuses on mitigating the capital expenditure required to deploy OTN interfaces, usually the most costly element in the network, as well as minimizing the required number of wavelengths in the Routing and Wavelength Assignment (RWA) problem, contributing to the overall reduction in network costs and ensuring open capacity for future expansions. As the RWA problem is NP-hard and involves significant computational costs, we also propose a multi-step heuristic approach to tackle larger network instances more efficiently. In this approach, the optimization steps for the OTN design and the RWA solutions are conducted independently. For the OTN-layer planning, the optimum ILP formulation (OTN-ILP) is maintained, so that the optimum solution for the cost of installed interfaces on the OTN layer is guaranteed. The RWA problem is proposed through either an ILP formulation (RWA-ILP) or a heuristic approach. The RWA-ILP model can find the same or slightly superior number of wavelengths compared to the optimum solution of the Integrated ILP formulation, but it can provide results in reasonable times only for small networks. On the other hand, the heuristic RWA is able to run any network size, but it requires more wavelengths compared to the RWA-ILP model.

Mitigating attenuation effects in free-space optics using WDM under variable atmospheric conditions

Abstract This research delves into the optimization of wavelength division multiplexing (WDM) within free space optical (FSO) communication systems, aiming to enhance the system’s resilience against atmospheric disruptions. FSO communication, known for its high bandwidth capabilities in unlicensed frequency bands, often encounters reliability issues due to weather-related signal degradation. By integrating a novel WDM-FSO approach, this study seeks to extend the operational range by using switching technique, thereby ensuring consistent and reliable communication. The introduction of a sophisticated switching and fork mechanism is pivotal in this context, facilitating dynamic signal routing and the strategic placement of optical amplifiers to counteract the impact of weather fluctuations and geographical challenges on signal integrity. This system, engineered to support a data transmission rate of 25 Gbps, caters to the needs of applications requiring high bandwidth. Through rigorous performance evaluation based on the Q-factor and BER under various atmospheric conditions, the effectiveness of the WDM-FSO system is demonstrated. The findings are detailed through graphs and tables, providing a comprehensive understanding of the system’s performance. This study makes a significant contribution to the field of wireless optical communication by presenting an optimized WDM-FSO system capable of overcoming weather-related obstacles especially at places where weather conditions are changed very frequently, marking a step forward in establishing more reliable FSO communication networks.

Optical Add-Drop Multiplexers: Enhancing High Transmission Bit Rates in Next-Generation Communication Networks

The development of optical networks in the telecommunications sector is becoming much closer by considering the help of an Optical Add Drop Multiplexer (OADM) based on a novel technology called Wavelength Division Multiplexing (DWDM). The objective of the current study to examine high transmission bit rates for next-generation optical communication networks using the technology of OADM Based on DWDM. Artificial neural networks (ANNs) were developed via MATLAB software to predict three main parameters in this filed such as transmitted signal power (PT), transmitted signal bandwidth (B.Wsig), and transmission bit rate capacity (Bsh) at different fiber cable lengths, such as L=200, 250, and 300 km. The ANNs results showed that, standard error (SE) for predicting PT as a function of the number of transmitted channels (Nch) was 0.115 mW, 0.095 mW and 0.077 mW, for 200, 250 and 300 km, respectively. Additionally, the SE for predicting B.Wsig was 0.067 GHz, 0.051 GHz and 0.040 GHz for 200, 250 and 300 km, respectively. Lastly, the SE for predicting Bsh was 1.665, 1.311 Gbit/sec and 1.076Gbit/sec for 200, 250 and 300 km, respectively. The SE for predicting PT as a function of the Signal Wavelength (λ) was 0.116, 0.096 and 0.079 mW for 200, 250 and 300 km, respectively. Additionally, the SE for predicting B.Wsig was 0.067, 0.052 and 0.052 GHz for 200, 250 and 300 km, respectively. Lastly, the SE for predicting Bsh was 1.688, 1.417 and 1.110 Gbit/sec for 200, 250 and 300 km, respectively. The low SE in ANNs demonstrated the efficiency, motivating further advancements in optimizing network performance for high-bit-rate transmission.

On-chip wavelength division multiplexing by angled multimode interferometer fabricated on erbium-doped thin film lithium niobate on insulator

Abstract 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.

A metasurface-based full-color circular auto-focusing Airy beam transmitter for stable high-speed underwater wireless optical communications

Due to its unique intensity distribution, self-acceleration, and beam self-healing properties, Airy beam holds great potential for optical wireless communications in challenging channels, such as underwater environments. As a vital part of 6G wireless network, the Internet of Underwater Things requires high-stability, low-latency, and high-capacity underwater wireless optical communication (UWOC). Currently, the primary challenge of UWOC lies in the prevalent time-varying and complex channel characteristics. Conventional blue Gaussian beam-based systems face difficulties in underwater randomly perturbed links. In this work, we report a full-color circular auto-focusing Airy beams metasurface transmitter for reliable, large-capacity and long-distance UWOC links. The metasurface is designed to exhibits high polarization conversion efficiency over a wide band (440-640 nm), enabling an increased data transmission rate of 91% and reliable 4 K video transmission in wavelength division multiplexing (WDM) based UWOC data link. The successful application of this metasurface in challenging UWOC links establishes a foundation for underwater interconnection scenarios in 6G communication.