Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low inse...Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.展开更多
On-chip diffractive optical neural networks(DONNs)bring the advantages of parallel processing and low energy consumption.However,an accurate representation of the optical field’s evolution in the structure cannot be ...On-chip diffractive optical neural networks(DONNs)bring the advantages of parallel processing and low energy consumption.However,an accurate representation of the optical field’s evolution in the structure cannot be provided using the previous diffraction-based analysis method.Moreover,the loss caused by the open boundaries poses challenges to applications.A multimode DONN architecture based on a more precise eigenmode analysis method is proposed.We have constructed a universal library of input,output,and metaline structures utilizing this method,and realized a multimode DONN composed of the structures from the library.On the designed multimode DONNs with only one layer of the metaline,the classification task of an Iris plants dataset is verified with an accuracy of 90%on the blind test dataset,and the performance of the one-bit binary adder task is also validated.Compared to the previous architectures,the multimode DONN exhibits a more compact design and higher energy efficiency.展开更多
Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one servi...Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one service is sent over the fiber at a time. However, many different services can be simultaneously conveyed in railway stations such as passenger information service, cellular phone, Wi-Fi... The objective of the work proposed in this paper is to demonstrate the potential benefits of transmitting radio signals over fiber in a railway environment. The main idea is to exploit the full capacity of the fiber by transmitting multiple services using the same fiber. Since, different services are operating in different frequency bands; we propose a new multiplexing technique called Mode Group Diversity Multiplexing （MGDM） to ensure the transmission of multiple services using the same fiber, without additional infrastructure. There are numerous advantages of the proposed technique, e.g., faster and reliable data exchange, high resolution video surveillance capability, high data rate information exchange in railway stations. We present, in this paper, the physical characteristics of optical fibers, performance of MGDM multiplexing technique, and the influence of the laser excitation conditions at the entrance of the fiber on the performances of the system.展开更多
Femtosecond laser fabrication technology has been applied to photonic-lantern mode(de)multiplexers owing to its 3D fabrication capability.Current photonic-lantern mode(de)multiplexer designs based on femtosecond laser...Femtosecond laser fabrication technology has been applied to photonic-lantern mode(de)multiplexers owing to its 3D fabrication capability.Current photonic-lantern mode(de)multiplexer designs based on femtosecond laser fabrication technology mostly follow a fibre-type photonic lantern design,which uses trajectory-symmetry structures with non-uniform waveguides for selective mode excitation.However,non-uniform waveguides can lead to inconsistent waveguide transmission and coupling losses.Trajectory-symmetry designs are inefficient for selective-mode excitation.Therefore,we optimised the design using trajectory asymmetry with uniform waveguides and fabricated superior ultrafast laser-inscribed photonic-lantern mode(de)multiplexers.Consistent waveguide transmission and coupling losses(0.1 dB/cm and 0.2 dB/facet,respectively)at 1550 nm were obtained on uniform single-mode waveguides.Based on the trajectory-asymmetry design for photonic-lantern mode LPa11 LPb11 LP01(de)multiplexers,efficient mode excitation(,,and)with average insertion losses as low as 1 dB at 1550 nm was achieved,with mode-dependent losses of less than 0.3 dB.The photonic-lantern design was polarisation-insensitive,and the polarisation-determined losses were less than 0.2 dB.Along with polarisation LPa11x LPa11y LPb11x LPb11y LP01xmultiplexing realised by fibre-type polarisation beam splitters,six signal channels(,,,,,LP01yand),each carrying 42 Gaud/s quadrature phase-shift keying signals,were transmitted through a few-mode fibre for optical transmission.The average insertion loss of the system is less than 5 dB,while its maximum crosstalk with the few-mode fibre is less than-12 dB,leading to a 4-dB power penalty.The findings of this study pave the way for the practical application of 3D integrated photonic chips in high-capacity optical transmission systems.展开更多
Herein,an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which in-cludes wavelength division multiplexing(WDM),polarization division multiplexing(PDM),space division mul...Herein,an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which in-cludes wavelength division multiplexing(WDM),polarization division multiplexing(PDM),space division multiplexing(SDM),mode division multiplexing(MDM)and orbital angular momentum multiplexing(OAMM).Multiplexing is a mech-anism by which multiple signals are combined into a shared channel used to showcase the maximum capacity of the op-tical links.However,it is critical to develop hybrid multiplexing methods to allow enhanced channel numbers.In this re-view,we have also included hybrid multiplexing techniques such as WDM-PDM,WDM-MDM and PDM-MDM.It is prob-able to attain N×M channels by utilizing N wavelengths and M guided-modes by simply utilizing hybrid WDM-MDM(de)multiplexers.To the best of our knowledge,this review paper is one of its kind which has highlighted the most prom-inent and recent signs of progress in multiplexing techniques in one place.展开更多
Recent reports from World Health Organization(WHO)show the impact of human negligence as a serious concern for road accidents and casualties worldwide.There are number of reasons which led to this negligence;hence,nee...Recent reports from World Health Organization(WHO)show the impact of human negligence as a serious concern for road accidents and casualties worldwide.There are number of reasons which led to this negligence;hence,need of intelligent transportation system(ITS)gains more attention from researchers worldwide.For achieving such autonomy different sensors are involved in autonomous vehicles which can sense road conditions and warn the control system about possible hazards.This work is focused on designing one such sensor system which can detect and range multiple targets under the impact of adverse atmospheric conditions.A high-speed Linear Frequency Modulated Continuous Wave(LFMCW)based Photonic Radar is proposed to detect multiple targets by integrating Mode division multiplexing(MDM).Reported results in terms of range frequency,Doppler frequency and range resolution are demonstrated using numerical simulations with the bandwidths of 1 and 4 GHz and under adverse atmospheric conditions carrying 75 dB/km of attenuation.To prove the effectiveness of the proposed photonic radar,moving targets are also demonstrated with different speed.System reported substantial range resolution of 15 cm using 1 GHz of bandwidth and 3 cm using 4 GHz of bandwidth.展开更多
Compact passive silicon photonic devices with high performance are always desired for future largescale photonic integration.Inverse design provides a promising approach to realize new-generation photonic devices,whil...Compact passive silicon photonic devices with high performance are always desired for future largescale photonic integration.Inverse design provides a promising approach to realize new-generation photonic devices,while it is still very challenging to realize complex photonic devices for most inverse designs reported previously due to the limits of computational resources.Here,we present the realization of several representative advanced passive silicon photonic devices with complex optimization,including a sixchannel mode(de)multiplexer,a broadband 90 deg hybrid,and a flat-top wavelength demultiplexer.These devices are designed inversely by optimizing a subwavelength grating(SWG)region and the multimode excitation and the multimode interference are manipulated.Particularly,such SWG structures are more fabrication-friendly than those random nanostructures introduced in previous inverse designs.The realized photonic devices have decent performances in a broad bandwidth with a low excess loss of<1 dB,which is much lower than that of previous inverse-designed devices.The present inverse design strategy shows great effectiveness for designing advanced photonic devices with complex requirements(which is beyond the capability of previous inverse designs)by using affordable computational resources.展开更多
Orbital angular momentum(OAM)beams,characterized by a helical phase structure and phase singularity,have emerged as a powerful resource for high-capacity optical communications through mode-division multiplexing(MDM)....Orbital angular momentum(OAM)beams,characterized by a helical phase structure and phase singularity,have emerged as a powerful resource for high-capacity optical communications through mode-division multiplexing(MDM).Traditional OAM multiplexing systems operating solely in the spatial domain face significant challenges,including increased system complexity,inter-modal crosstalk,and limited scalability.Recent advances have explored hybrid multiplexing schemes combining OAM with wavelength or polarization degrees of freedom,demonstrating Pbit/s level transmission capacities.However,these systems predominantly rely on continuous-wave lasers and external modulators,which constrain their applicability in challenging environments,whereas pulsed lasers provide superior peak power,enhanced transmission robustness,and the potential for implementation of OAM lasers,which generally emit pulsed OAM beams.Here,we report an OAM-based spatiotemporal multiplexing(OAM-STM)technique that synergistically implements pulsed OAM beams with a diffractive deep neural network(D^(2)NN)and optical fiber delay lines to project spatial mode information into the temporal domain.This approach leverages the full potential of pulsed laser sources by activating the underutilized time dimension,thereby overcoming the repetition-rate bottleneck and enhancing channel throughput.We experimentally demonstrate an OAM-based spatiotemporal demultiplexer achieving demultiplexing speed limited only by the bandwidth of the photodiode if OAM generation is fast enough.In the meantime,the architecture is intrinsically compatible with high-repetition-rate OAM sources,offering the entire system the scalability to GHz rates.This work establishes a foundational framework for high-speed,all-optical,and high-capacity OAM-STM systems,with promising implications for free-space optical communication,underwater communication links,and other complex environments.展开更多
Optical interconnects based on photonic integrated circuits(PICs)are emerging as a pivotal technology to address the relentless surge in data traffic driven by compute-intensive applications.Combining mode-division mu...Optical interconnects based on photonic integrated circuits(PICs)are emerging as a pivotal technology to address the relentless surge in data traffic driven by compute-intensive applications.Combining mode-division multiplexing(MDM)with wavelength-division multiplexing(WDM)offers a compelling approach to significantly enhance the shoreline density of optical interconnects.However,existing on-chip MDM systems encounter considerable challenges in simultaneously achieving a large optical bandwidth,multi-band operation,and ultra-compactness,thereby limiting scalability as conventional telecom band resources become increasingly constrained.Here we introduce,to our knowledge,the first inverse-designed multi-band mode multiplexer(MUX)utilizing a digital metamaterial structure to support the first three-order TE modes.The proposed device features an ultra-compact footprint of 6μm×4.8μm and exhibits an exceptionally flat spectral response,with numerical simulations confirming spectral variations of less than 0.94 dB across the 1500–2100 nm range.Experimental results further validate its performance,demonstrating insertion losses below 4.3 dB and 4.0 dB,and crosstalk below−11.6 dB and−11.3 dB,within the 1525–1585 nm and 1940–2040 nm bands,respectively.Additionally,system-level optical interconnect experiments using a multi-band MDM circuit successfully achieve single-wavelength transmission rates of 3-modes×180 Gb∕s at the 1.55μm band and record-setting 3-modes×114 Gb∕s in the 2μm band.This work highlights the transformative potential of employing multi-band MDM technology to enhance bandwidth density and scalability,providing a robust foundation for next-generation high-capacity on-chip optical interconnects.展开更多
Mode-division multiplexing（MDM） has become an increasingly important technology to further increase the transmission capacity of both optical-fiber-based communication networks, data centers and waveguidebased on-ch...Mode-division multiplexing（MDM） has become an increasingly important technology to further increase the transmission capacity of both optical-fiber-based communication networks, data centers and waveguidebased on-chip optical interconnects. Mode manipulation devices are indispensable in MDM system and have been widely studied in fiber, planar lightwave circuits, and silicon and InP based platforms. InP-based integration technology provides the easiest accessibility to bring together the functions of laser sources, modulators, and mode manipulation devices into a single chip, making it a promising solution for fully integrated few-mode transmitters in the MDM system. This paper reviews the recent progress in InP-based mode manipulation devices, including the few-mode converters, multiplexers, demultiplexers, and transmitters. The working principle, structures, and performance of InP-based few-mode devices are discussed.展开更多
To overcome the capacity crunch of optical communications based on the traditional single-mode fiber(SMF), different modes in a few-mode fiber(FMF) can be employed for mode division multiplexing(MDM). MDM can also be ...To overcome the capacity crunch of optical communications based on the traditional single-mode fiber(SMF), different modes in a few-mode fiber(FMF) can be employed for mode division multiplexing(MDM). MDM can also be extended to photonic integration for obtaining improved density and efficiency, as well as interconnection capacity. Therefore, MDM becomes the most promising method for maintaining the trend of "Moore’s law" in photonic integration and optical fiber transmission. In this tutorial, we provide a review of MDM works and cutting-edge progresses from photonic integration to optical fiber transmission, including our recent works of MDM low-noise amplification, FMF fiber design, MDM Si photonic devices, and so on. Research and application challenges of MDM for optical communications regarding long-haul transmission and short reach interconnection are discussed as well. The content is expected to be of important value for both academic researchers and industrial engineers during the development of next-generation optical communication systems,from photonic chips to fiber links.展开更多
Published online:14 August 2023 A matrix-vector multiplication(MVM)optical signal processor based on mode division multiplexing(MDM)was proposed and demon-strated in the current work,which is composed of a mode multip...Published online:14 August 2023 A matrix-vector multiplication(MVM)optical signal processor based on mode division multiplexing(MDM)was proposed and demon-strated in the current work,which is composed of a mode multiplexer,a multimode beam splitter,a mode demultiplexer,a modulator ar-ray and combiners.In addition,the characteristics of MDM obviate the need for multiple wavelengths and therefore multiple laser light sources are unneeded,which greatly reduces the complexity and cost.A 4×4 MDM-MVM was realized on a standard silicon-on-insulator(SOI)platform.Combined with the off-chip light source and photode-tectors(PDs),4-level modulation has been demonstrated,and each level of the output signal could represent 2 bits of information.展开更多
We experimentally transmit eight wavelength-division-multiplexing(WDM)channels,16 quadratic-amplitude-modulation(QAM)signals at 32-GBaud,over 1000 km few mode fiber(FMF).In this experiment,we use WDM,mode division mul...We experimentally transmit eight wavelength-division-multiplexing(WDM)channels,16 quadratic-amplitude-modulation(QAM)signals at 32-GBaud,over 1000 km few mode fiber(FMF).In this experiment,we use WDM,mode division multiplexing,and polarization multiplexing for signal transmission.Through the multiple-input-multiple-output(MIMO)equalization algorithms,we achieve the total line transmission rate of 4.096 Tbit/s.The results prove that the bit error rates(BERs)for the16QAM signals after 1000 km FMF transmission are below the soft-decision forward-error-correction(SD-FEC)threshold of2.4×10^(-2),and the net rate reaches 3.413 Tbit/s.Our proposed system provides a reference for the future development of high-capacity communication.展开更多
This study presents a high-accuracy,all-fber mode division multiplexing(MDM)reconstructive spectrometer(RS).The MDM was achieved by utilizing a custom-designed 3×1 mode-selective photonics lantern to launch disti...This study presents a high-accuracy,all-fber mode division multiplexing(MDM)reconstructive spectrometer(RS).The MDM was achieved by utilizing a custom-designed 3×1 mode-selective photonics lantern to launch distinct spatial modes into the multimode fber(MMF).This facilitated the information transmission by increasing light scattering processes,thereby encoding the optical spectra more comprehensively into speckle patterns.Spectral resolution of 2 pm and the recovery of 2000 spectral channels were accomplished.Compared to methods employing single-mode excitation and two-mode excitation,the three-mode excitation method reduced the recovered error by 88%and 50%respectively.A resolution enhancement approach based on alternating mode modulation was proposed,reaching the MMF limit for the 3 dB bandwidth of the spectral correlation function.The proof-of-concept study can be further extended to encompass diverse programmable mode excitations.It is not only succinct and highly efcient but also well-suited for a variety of high-accuracy,high-resolution spectral measurement scenarios.展开更多
We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by ...We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by the scattering of guided waves to free space with respect to different modes. According to different mode numbers, these guided modes have different responses to the multiplexed hologram, and then give rise to different holographic images in reconstructions. In experiments, we show two kinds of MDMHs based on TM0∕TE0 and TE0∕TE1 modes as examples. Our approach could enrich the holography method that favors on-chip integration.展开更多
In this study,we proposed and experimentally demonstrated an electro-optic modulator with a small footprint and high modulation efficiency,achieved through the utilization of a mode-folded phase shifter with lumped el...In this study,we proposed and experimentally demonstrated an electro-optic modulator with a small footprint and high modulation efficiency,achieved through the utilization of a mode-folded phase shifter with lumped electrodes.The threemode phase shifter recycles the light three times with different waveguide modes while leading to a pronounced tightening of the optical field confinement.We experimentally obtained a 3.7-times improvement in the modulation efficiency.A low V_(π)L for thin-film lithium niobate(TFLN)Mach-Zehnder modulators of 1 V·cm is realized with a device footprint of 2.7 mm×0.6 mm(0.5 mm for the phase shifter).Even greater improvements in modulation efficiency can be expected through the incorporation of additional modes.展开更多
The design, fabrication and characterization of a fundamental/first-order mode converter based on mul- timode interference coupler on InP substrate were reported. Detailed optimization of the device parameters were in...The design, fabrication and characterization of a fundamental/first-order mode converter based on mul- timode interference coupler on InP substrate were reported. Detailed optimization of the device parameters were investigated using 3D beam propagation method. In the experiments, the fabricated mode converter realized mode conversion from the fundamental mode to the first-order mode in the wavelength range of 1530-1565 nm with ex- cess loss less than 3 dB. Moreover, LPol and LP11 fiber modes were successfully excited from a few-mode fiber by using the device. This InP-based mode converter can be a possible candidate for integrated transceivers for future mode-division multiplexing system.展开更多
Mode-and polarization-division multiplexing are new promising options to increase the transmission capacity of optical communications.On-chip silicon polarization and mode handling devices are key components in integr...Mode-and polarization-division multiplexing are new promising options to increase the transmission capacity of optical communications.On-chip silicon polarization and mode handling devices are key components in integrated mode-and polarization-division multi-plexed photonic circuits.In this paper,we review our recent progresses on silicon-based polarization beam splitters,polarization splitters and rotators,mode（de）multiplexers,and mode and polarization selective switches.Silicon polarization beam splitters and rotators are demonstrated with high extinction ratio,compact footprint and high fabrication tolerance.For on-chip mode multiplexing,we introduce a low loss and fabrication tolerant three-mode（de）multiplexer employing sub-wavelength grating structure.In analogy to a conventional wavelength selective switch in wavelength-division multi-plexing,we demonstrate a selective switch that can route mode-and polarization-multiplexed signals.展开更多
We propose an alternative approach to compensation of intermodal interactions in few-mode optical fibers by means of digital backpropagation.Instead of solving the inverse generalized multimode nonlinear Schr?dinger e...We propose an alternative approach to compensation of intermodal interactions in few-mode optical fibers by means of digital backpropagation.Instead of solving the inverse generalized multimode nonlinear Schr?dinger equation,we accomplish backpropagation of the multimode signals with help of their near-field intensity distributions captured by a camera.We demonstrate that this task can successfully be handled by a deep neural network and provide a proof of concept by training an autoencoder for backpropagation of six linearly polarized[LP]modes of a step-index fiber.展开更多
We propose a transfer-learning multi-input multi-output(TL-MIMO)scheme to significantly reduce the required training complexity for converging the equalizers in mode-division multiplexing(MDM)systems.Based on a built ...We propose a transfer-learning multi-input multi-output(TL-MIMO)scheme to significantly reduce the required training complexity for converging the equalizers in mode-division multiplexing(MDM)systems.Based on a built three-mode(LP01,LP11a,and LP11b)multiplexed experimental system,we thoughtfully investigate the TL-MIMO performances on the three-typed data,collecting from different sampling times,launching optical powers,and inputting optical signal-to-noise ratios(OSNRs).A dramatic reduction of approximately 40%–83.33%in the required training complexity is achieved in all three scenarios.Furthermore,the good stability of TL-MIMO in both the launched powers and OSNR test bands has also been proved.展开更多
基金supported in part by the ZTE Industry-University-Institute Cooperation Funds.
文摘Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.
基金supported by the National Natural Science Foundation of China (Grant No.62135009)the Beijing Municipal Science and Technology Commission,Administrative Commission of Zhongguancun Science Park (Grant No.Z221100005322010).
文摘On-chip diffractive optical neural networks(DONNs)bring the advantages of parallel processing and low energy consumption.However,an accurate representation of the optical field’s evolution in the structure cannot be provided using the previous diffraction-based analysis method.Moreover,the loss caused by the open boundaries poses challenges to applications.A multimode DONN architecture based on a more precise eigenmode analysis method is proposed.We have constructed a universal library of input,output,and metaline structures utilizing this method,and realized a multimode DONN composed of the structures from the library.On the designed multimode DONNs with only one layer of the metaline,the classification task of an Iris plants dataset is verified with an accuracy of 90%on the blind test dataset,and the performance of the one-bit binary adder task is also validated.Compared to the previous architectures,the multimode DONN exhibits a more compact design and higher energy efficiency.
文摘Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one service is sent over the fiber at a time. However, many different services can be simultaneously conveyed in railway stations such as passenger information service, cellular phone, Wi-Fi... The objective of the work proposed in this paper is to demonstrate the potential benefits of transmitting radio signals over fiber in a railway environment. The main idea is to exploit the full capacity of the fiber by transmitting multiple services using the same fiber. Since, different services are operating in different frequency bands; we propose a new multiplexing technique called Mode Group Diversity Multiplexing （MGDM） to ensure the transmission of multiple services using the same fiber, without additional infrastructure. There are numerous advantages of the proposed technique, e.g., faster and reliable data exchange, high resolution video surveillance capability, high data rate information exchange in railway stations. We present, in this paper, the physical characteristics of optical fibers, performance of MGDM multiplexing technique, and the influence of the laser excitation conditions at the entrance of the fiber on the performances of the system.
基金supported by the National Natural Science Foundation of China(NSFC)(62125503,62261160388)the Natural Science Foundation of Hubei Province of China(2023AFA028)the Innovation Project of Optics Valley Laboratory(OVL2021BG004).
文摘Femtosecond laser fabrication technology has been applied to photonic-lantern mode(de)multiplexers owing to its 3D fabrication capability.Current photonic-lantern mode(de)multiplexer designs based on femtosecond laser fabrication technology mostly follow a fibre-type photonic lantern design,which uses trajectory-symmetry structures with non-uniform waveguides for selective mode excitation.However,non-uniform waveguides can lead to inconsistent waveguide transmission and coupling losses.Trajectory-symmetry designs are inefficient for selective-mode excitation.Therefore,we optimised the design using trajectory asymmetry with uniform waveguides and fabricated superior ultrafast laser-inscribed photonic-lantern mode(de)multiplexers.Consistent waveguide transmission and coupling losses(0.1 dB/cm and 0.2 dB/facet,respectively)at 1550 nm were obtained on uniform single-mode waveguides.Based on the trajectory-asymmetry design for photonic-lantern mode LPa11 LPb11 LP01(de)multiplexers,efficient mode excitation(,,and)with average insertion losses as low as 1 dB at 1550 nm was achieved,with mode-dependent losses of less than 0.3 dB.The photonic-lantern design was polarisation-insensitive,and the polarisation-determined losses were less than 0.2 dB.Along with polarisation LPa11x LPa11y LPb11x LPb11y LP01xmultiplexing realised by fibre-type polarisation beam splitters,six signal channels(,,,,,LP01yand),each carrying 42 Gaud/s quadrature phase-shift keying signals,were transmitted through a few-mode fibre for optical transmission.The average insertion loss of the system is less than 5 dB,while its maximum crosstalk with the few-mode fibre is less than-12 dB,leading to a 4-dB power penalty.The findings of this study pave the way for the practical application of 3D integrated photonic chips in high-capacity optical transmission systems.
基金financially supported by the Russian Foundation for Basic Research(grant No.18-29-20045)for WDM,MDM and hybrid WDM-MDM,WDM-PDM sectionsthe Russian Science Foundation(grant No.21-79-20075)for PDM,OAMM and hybrid PDM-MDM sectionsthe Ministry of Science and Higher Education of the Russian Federation under the FSRC"Crystallography and Photonics"of the Russian Academy of Sciences(the state task No.007-GZ/Ch3363/26)for comparative analysis.
文摘Herein,an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which in-cludes wavelength division multiplexing(WDM),polarization division multiplexing(PDM),space division multiplexing(SDM),mode division multiplexing(MDM)and orbital angular momentum multiplexing(OAMM).Multiplexing is a mech-anism by which multiple signals are combined into a shared channel used to showcase the maximum capacity of the op-tical links.However,it is critical to develop hybrid multiplexing methods to allow enhanced channel numbers.In this re-view,we have also included hybrid multiplexing techniques such as WDM-PDM,WDM-MDM and PDM-MDM.It is prob-able to attain N×M channels by utilizing N wavelengths and M guided-modes by simply utilizing hybrid WDM-MDM(de)multiplexers.To the best of our knowledge,this review paper is one of its kind which has highlighted the most prom-inent and recent signs of progress in multiplexing techniques in one place.
基金This research project is supported by the Second Century Fund(C2F)Chulalongkorn University,Thailand.This research work is also funded by TSRI Fund(CU_FRB640001_01_21_8)+1 种基金The authors also would like to thank Taif University Researchers supporting project number(TURSP-2020/228)Taif University,Taif,Saudi Arabia.
文摘Recent reports from World Health Organization(WHO)show the impact of human negligence as a serious concern for road accidents and casualties worldwide.There are number of reasons which led to this negligence;hence,need of intelligent transportation system(ITS)gains more attention from researchers worldwide.For achieving such autonomy different sensors are involved in autonomous vehicles which can sense road conditions and warn the control system about possible hazards.This work is focused on designing one such sensor system which can detect and range multiple targets under the impact of adverse atmospheric conditions.A high-speed Linear Frequency Modulated Continuous Wave(LFMCW)based Photonic Radar is proposed to detect multiple targets by integrating Mode division multiplexing(MDM).Reported results in terms of range frequency,Doppler frequency and range resolution are demonstrated using numerical simulations with the bandwidths of 1 and 4 GHz and under adverse atmospheric conditions carrying 75 dB/km of attenuation.To prove the effectiveness of the proposed photonic radar,moving targets are also demonstrated with different speed.System reported substantial range resolution of 15 cm using 1 GHz of bandwidth and 3 cm using 4 GHz of bandwidth.
基金supported by the National Major Research and Development Program(Grant No.2018YFB2200200)the National Science Fund for Distinguished Young Scholars(Grant No.61725503)+3 种基金the National Natural Science Foundation of China(Grant Nos.62175216,61961146003,91950205)Zhejiang Provincial Natural Science Foundation(Grant No.LR22F050001)The Fundamental Research Funds for the Central UniversitiesThe Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(Grant No.2021R01001).
文摘Compact passive silicon photonic devices with high performance are always desired for future largescale photonic integration.Inverse design provides a promising approach to realize new-generation photonic devices,while it is still very challenging to realize complex photonic devices for most inverse designs reported previously due to the limits of computational resources.Here,we present the realization of several representative advanced passive silicon photonic devices with complex optimization,including a sixchannel mode(de)multiplexer,a broadband 90 deg hybrid,and a flat-top wavelength demultiplexer.These devices are designed inversely by optimizing a subwavelength grating(SWG)region and the multimode excitation and the multimode interference are manipulated.Particularly,such SWG structures are more fabrication-friendly than those random nanostructures introduced in previous inverse designs.The realized photonic devices have decent performances in a broad bandwidth with a low excess loss of<1 dB,which is much lower than that of previous inverse-designed devices.The present inverse design strategy shows great effectiveness for designing advanced photonic devices with complex requirements(which is beyond the capability of previous inverse designs)by using affordable computational resources.
基金supported by the National Natural Science Foundation of China(no.62275167,62405287,61905147,92250304)the Natural Science Foundation of Zhejiang Province(no.LZYQ25F050001)the Key R&D Program of Zhejiang(no.2024SSYS0014).
文摘Orbital angular momentum(OAM)beams,characterized by a helical phase structure and phase singularity,have emerged as a powerful resource for high-capacity optical communications through mode-division multiplexing(MDM).Traditional OAM multiplexing systems operating solely in the spatial domain face significant challenges,including increased system complexity,inter-modal crosstalk,and limited scalability.Recent advances have explored hybrid multiplexing schemes combining OAM with wavelength or polarization degrees of freedom,demonstrating Pbit/s level transmission capacities.However,these systems predominantly rely on continuous-wave lasers and external modulators,which constrain their applicability in challenging environments,whereas pulsed lasers provide superior peak power,enhanced transmission robustness,and the potential for implementation of OAM lasers,which generally emit pulsed OAM beams.Here,we report an OAM-based spatiotemporal multiplexing(OAM-STM)technique that synergistically implements pulsed OAM beams with a diffractive deep neural network(D^(2)NN)and optical fiber delay lines to project spatial mode information into the temporal domain.This approach leverages the full potential of pulsed laser sources by activating the underutilized time dimension,thereby overcoming the repetition-rate bottleneck and enhancing channel throughput.We experimentally demonstrate an OAM-based spatiotemporal demultiplexer achieving demultiplexing speed limited only by the bandwidth of the photodiode if OAM generation is fast enough.In the meantime,the architecture is intrinsically compatible with high-repetition-rate OAM sources,offering the entire system the scalability to GHz rates.This work establishes a foundational framework for high-speed,all-optical,and high-capacity OAM-STM systems,with promising implications for free-space optical communication,underwater communication links,and other complex environments.
基金National Key Research and Development Program of China(2023YFB2905700)National Natural Science Foundation of China(62235005,61925104,62171137).
文摘Optical interconnects based on photonic integrated circuits(PICs)are emerging as a pivotal technology to address the relentless surge in data traffic driven by compute-intensive applications.Combining mode-division multiplexing(MDM)with wavelength-division multiplexing(WDM)offers a compelling approach to significantly enhance the shoreline density of optical interconnects.However,existing on-chip MDM systems encounter considerable challenges in simultaneously achieving a large optical bandwidth,multi-band operation,and ultra-compactness,thereby limiting scalability as conventional telecom band resources become increasingly constrained.Here we introduce,to our knowledge,the first inverse-designed multi-band mode multiplexer(MUX)utilizing a digital metamaterial structure to support the first three-order TE modes.The proposed device features an ultra-compact footprint of 6μm×4.8μm and exhibits an exceptionally flat spectral response,with numerical simulations confirming spectral variations of less than 0.94 dB across the 1500–2100 nm range.Experimental results further validate its performance,demonstrating insertion losses below 4.3 dB and 4.0 dB,and crosstalk below−11.6 dB and−11.3 dB,within the 1525–1585 nm and 1940–2040 nm bands,respectively.Additionally,system-level optical interconnect experiments using a multi-band MDM circuit successfully achieve single-wavelength transmission rates of 3-modes×180 Gb∕s at the 1.55μm band and record-setting 3-modes×114 Gb∕s in the 2μm band.This work highlights the transformative potential of employing multi-band MDM technology to enhance bandwidth density and scalability,providing a robust foundation for next-generation high-capacity on-chip optical interconnects.
基金Project supported by the State Key Development Program for Basic Research of China(No.2014CB340102)the National Key Research&Development(R&D)Plan(No.2016YFB0402301)the National Natural Science Foundation of China(No.61335009)
文摘Mode-division multiplexing（MDM） has become an increasingly important technology to further increase the transmission capacity of both optical-fiber-based communication networks, data centers and waveguidebased on-chip optical interconnects. Mode manipulation devices are indispensable in MDM system and have been widely studied in fiber, planar lightwave circuits, and silicon and InP based platforms. InP-based integration technology provides the easiest accessibility to bring together the functions of laser sources, modulators, and mode manipulation devices into a single chip, making it a promising solution for fully integrated few-mode transmitters in the MDM system. This paper reviews the recent progress in InP-based mode manipulation devices, including the few-mode converters, multiplexers, demultiplexers, and transmitters. The working principle, structures, and performance of InP-based few-mode devices are discussed.
基金supported by the National Key R&D Program of China (No. 2018YFB1801804)the National Natural Science Foundation of China (NSFC) (Nos. 61935011, 61875124, and 61675128)
文摘To overcome the capacity crunch of optical communications based on the traditional single-mode fiber(SMF), different modes in a few-mode fiber(FMF) can be employed for mode division multiplexing(MDM). MDM can also be extended to photonic integration for obtaining improved density and efficiency, as well as interconnection capacity. Therefore, MDM becomes the most promising method for maintaining the trend of "Moore’s law" in photonic integration and optical fiber transmission. In this tutorial, we provide a review of MDM works and cutting-edge progresses from photonic integration to optical fiber transmission, including our recent works of MDM low-noise amplification, FMF fiber design, MDM Si photonic devices, and so on. Research and application challenges of MDM for optical communications regarding long-haul transmission and short reach interconnection are discussed as well. The content is expected to be of important value for both academic researchers and industrial engineers during the development of next-generation optical communication systems,from photonic chips to fiber links.
基金supported by National Major Research and Devel-opment Program(2021YFB2801703)National Natural Science Foundation of China(62135011&62105286)+1 种基金“Pioneer”and“Leading Goose”R&D Program of Zhejiang(2022C01103)the Fundamental Research Funds for the Central Universities.
文摘Published online:14 August 2023 A matrix-vector multiplication(MVM)optical signal processor based on mode division multiplexing(MDM)was proposed and demon-strated in the current work,which is composed of a mode multiplexer,a multimode beam splitter,a mode demultiplexer,a modulator ar-ray and combiners.In addition,the characteristics of MDM obviate the need for multiple wavelengths and therefore multiple laser light sources are unneeded,which greatly reduces the complexity and cost.A 4×4 MDM-MVM was realized on a standard silicon-on-insulator(SOI)platform.Combined with the off-chip light source and photode-tectors(PDs),4-level modulation has been demonstrated,and each level of the output signal could represent 2 bits of information.
基金supported by the National Key R&D Program of China(No.2018YFB1800905)the National Natural Science Foundation of China(Nos.61935005,61720106015,61835002,and 62127802)。
文摘We experimentally transmit eight wavelength-division-multiplexing(WDM)channels,16 quadratic-amplitude-modulation(QAM)signals at 32-GBaud,over 1000 km few mode fiber(FMF).In this experiment,we use WDM,mode division multiplexing,and polarization multiplexing for signal transmission.Through the multiple-input-multiple-output(MIMO)equalization algorithms,we achieve the total line transmission rate of 4.096 Tbit/s.The results prove that the bit error rates(BERs)for the16QAM signals after 1000 km FMF transmission are below the soft-decision forward-error-correction(SD-FEC)threshold of2.4×10^(-2),and the net rate reaches 3.413 Tbit/s.Our proposed system provides a reference for the future development of high-capacity communication.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.62305391)Hunan Innovative Province Construction Project(No.2019RS3017)Scientifc Fund of National University of Defense Technology(No.22-061).
文摘This study presents a high-accuracy,all-fber mode division multiplexing(MDM)reconstructive spectrometer(RS).The MDM was achieved by utilizing a custom-designed 3×1 mode-selective photonics lantern to launch distinct spatial modes into the multimode fber(MMF).This facilitated the information transmission by increasing light scattering processes,thereby encoding the optical spectra more comprehensively into speckle patterns.Spectral resolution of 2 pm and the recovery of 2000 spectral channels were accomplished.Compared to methods employing single-mode excitation and two-mode excitation,the three-mode excitation method reduced the recovered error by 88%and 50%respectively.A resolution enhancement approach based on alternating mode modulation was proposed,reaching the MMF limit for the 3 dB bandwidth of the spectral correlation function.The proof-of-concept study can be further extended to encompass diverse programmable mode excitations.It is not only succinct and highly efcient but also well-suited for a variety of high-accuracy,high-resolution spectral measurement scenarios.
基金supported by the National Key R&D Program of China(Nos.2017YFA0303700 and 2016YFA0202103)the National Natural Science Foundation of China(Nos.11674167 and 11621091)the support of PAPD from Jiangsu Province and the Dengfeng Project B of Nanjing University
文摘We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by the scattering of guided waves to free space with respect to different modes. According to different mode numbers, these guided modes have different responses to the multiplexed hologram, and then give rise to different holographic images in reconstructions. In experiments, we show two kinds of MDMHs based on TM0∕TE0 and TE0∕TE1 modes as examples. Our approach could enrich the holography method that favors on-chip integration.
基金supported by the National Key R&D Program of China(No.2023YFB2905502)the National Natural Science Foundation of China(Nos.62122047 and 61935011).
文摘In this study,we proposed and experimentally demonstrated an electro-optic modulator with a small footprint and high modulation efficiency,achieved through the utilization of a mode-folded phase shifter with lumped electrodes.The threemode phase shifter recycles the light three times with different waveguide modes while leading to a pronounced tightening of the optical field confinement.We experimentally obtained a 3.7-times improvement in the modulation efficiency.A low V_(π)L for thin-film lithium niobate(TFLN)Mach-Zehnder modulators of 1 V·cm is realized with a device footprint of 2.7 mm×0.6 mm(0.5 mm for the phase shifter).Even greater improvements in modulation efficiency can be expected through the incorporation of additional modes.
基金Project supported by the National Basic Research Program of China(No.2014CB340102)the National Natural Science Foundation of China(Nos.61274045,61335009)
文摘The design, fabrication and characterization of a fundamental/first-order mode converter based on mul- timode interference coupler on InP substrate were reported. Detailed optimization of the device parameters were investigated using 3D beam propagation method. In the experiments, the fabricated mode converter realized mode conversion from the fundamental mode to the first-order mode in the wavelength range of 1530-1565 nm with ex- cess loss less than 3 dB. Moreover, LPol and LP11 fiber modes were successfully excited from a few-mode fiber by using the device. This InP-based mode converter can be a possible candidate for integrated transceivers for future mode-division multiplexing system.
基金We thank Prof. Richard Soref, Prof. Xiaoqing Jiang, Prof. Jianyi Yang, and Prof. Christine Tremblay et al. for their helpful discussion and contributions. This work was supported in part by the National Natural Science Foundation of China （NSFC） （Grant Nos. 61605112, 61235007, 61505104）, in part by the 863 High-Tech Program （No. 2015AA017001）, and in part by the Science and Technology Commission of Shanghai Municipality （Nos. 15ZR1422800, 16XD1401400）. We thank the Center for Advanced Electronic Materials and Devices （AEMD） of Shanghai Jiao Tong University for the support in device fabrications.
文摘Mode-and polarization-division multiplexing are new promising options to increase the transmission capacity of optical communications.On-chip silicon polarization and mode handling devices are key components in integrated mode-and polarization-division multi-plexed photonic circuits.In this paper,we review our recent progresses on silicon-based polarization beam splitters,polarization splitters and rotators,mode（de）multiplexers,and mode and polarization selective switches.Silicon polarization beam splitters and rotators are demonstrated with high extinction ratio,compact footprint and high fabrication tolerance.For on-chip mode multiplexing,we introduce a low loss and fabrication tolerant three-mode（de）multiplexer employing sub-wavelength grating structure.In analogy to a conventional wavelength selective switch in wavelength-division multi-plexing,we demonstrate a selective switch that can route mode-and polarization-multiplexed signals.
文摘We propose an alternative approach to compensation of intermodal interactions in few-mode optical fibers by means of digital backpropagation.Instead of solving the inverse generalized multimode nonlinear Schr?dinger equation,we accomplish backpropagation of the multimode signals with help of their near-field intensity distributions captured by a camera.We demonstrate that this task can successfully be handled by a deep neural network and provide a proof of concept by training an autoencoder for backpropagation of six linearly polarized[LP]modes of a step-index fiber.
基金supported by the National Key R&D Program of China(No.2018YFB1801001)the Royal Society International Exchange Grant(No.IEC\NSFC\211244).
文摘We propose a transfer-learning multi-input multi-output(TL-MIMO)scheme to significantly reduce the required training complexity for converging the equalizers in mode-division multiplexing(MDM)systems.Based on a built three-mode(LP01,LP11a,and LP11b)multiplexed experimental system,we thoughtfully investigate the TL-MIMO performances on the three-typed data,collecting from different sampling times,launching optical powers,and inputting optical signal-to-noise ratios(OSNRs).A dramatic reduction of approximately 40%–83.33%in the required training complexity is achieved in all three scenarios.Furthermore,the good stability of TL-MIMO in both the launched powers and OSNR test bands has also been proved.
