On Multicast Routing With Network Coding: A Multiobjective Artificial Bee Colony Algorithm

This paper is concerned with two important issues in multicast routing problem with network coding for the first time, namely the load balancing and the transmission delay. A bi-objective optimization problem is formulated, where the average bandwidth utilization ratio and the average transmission delay are both to be minimized. To address the problem, we propose a novel multiobjective artificial bee colony algorithm, with two performance enhancing schemes integrated. The first scheme is an elitism-based food source generation scheme for scout bees, where for each scout bee, a new food source is generated by either recombining two elite solutions randomly selected from an archive or sampling the probabilistic distribution model built from all elite solutions in this archive. This scheme provides scouts with high-quality and diversified food sources and thus helps to strengthen the global exploration. The second one is a Pareto local search operator with the concept of path relinking integrated. This scheme is incorporated into the onlooker bee phase for exploring neighboring areas of promising food sources and hence enhances the local exploitation. Experimental results show that the proposed algorithm performs better than a number of state-of-the-art multiobjective evolutionary algorithms in terms of the approximated Pareto-optimal front.

A 32-channel 100 GHz wavelength division multiplexer by interleaving two silicon arrayed waveguide gratings

A 32-channel wavelength division multiplexer with 100 GHz spacing is designed and fabricated by interleaving two silicon arrayed waveguide gratings(AWGs).It has a parallel structure consisting of two silicon 16-channel AWGs with200 GHz spacing and a Mach-Zehnder interferometer(MZI)with 200 GHz free spectral range.The 16 channels of one silicon AWG are interleaved with those of the other AWG in spectrum,but with an identical spacing of 200 GHz.For the composed wavelength division multiplexer,the experiment results reveal 32 wavelength channels in C-band,a wavelength spacing of 100 GHz,and a channel crosstalk lower than-15 dB.

Joint modulation format identification and OSNR monitoring based on Stokes vector distribution features for digital coherent optical receivers

For joint modulation format identification(MFI)and optical signal-to-noise ratio(OSNR)monitoring,a simple and intelligent optical communication performance monitoring method is proposed,and the feasibility is demonstrated by digital coherent optical communication experiments.The experiment results show that for all modulation formats,including 28 GBaud polarization division multiplexing(PDM)QPSK/8-QAM/16-QAM/64-QAM,100%MFI accuracies are achieved even at OSNR values lower than the corresponding theoretical 20%forward error correction limit,as well as the high accuracies for OSNR monitoring.Furthermore,the proposed scheme has a reasonable monitoring level when chromatic dispersion and fiber nonlinear effects are varied.

Optical multipath self-interference cancellation for a wideband in-band full-duplex system using a silicon photonic modulator chip

We propose and experimentally demonstrate a photonic method for wideband multipath self-interference cancellation using a silicon photonic modulator chip.The chip generates phase-inverted reference signals by leveraging the opposite phase between optical sidebands.Effectively managing amplitude and phase imbalances between self-interference and reference signals,the approach rectifies discrepancies through consistent chip manufacturing and packaging processes.Employing photonic multi-dimensional multiplexing,including wavelength and polarization,enables the acquisition of multiple reference signals.Experimental results show multipath cancellation depths of 25.53 dB and 23.81 dB for bandwidths of 500 MHz and 1 GHz,achieved by superimposing 2-path reference signals.

0.75 Gbit/s high-speed classical key distribution with mode-shift keying chaos synchronization of Fabry–Perot lasers

High-speed physical key distribution is diligently pursued for secure communication.In this paper,we propose and experimentally demonstrate a scheme of high-speed key distribution using mode-shift keying chaos synchronization between two multi-longitudinal-mode Fabry–Perot lasers commonly driven by a super-luminescent diode.Legitimate users dynamically select one of the longitudinal modes according to private control codes to achieve mode-shift keying chaos synchronization.The two remote chaotic light waveforms are quantized to generate two raw random bit streams,and then those bits corresponding to chaos synchronization are sifted as shared keys by comparing the control codes.In this method,the transition time,i.e.,the chaos synchronization recovery time is determined by the rising time of the control codes rather than the laser transition response time,so the key distribution rate is improved greatly.Our experiment achieved a 0.75-Gbit/s key distribution rate with a bit error rate of 3.8×10^(−3)over 160-km fiber transmission with dispersion compensation.The entropy rate of the laser chaos is evaluated as 16 Gbit/s,which determines the ultimate final key rate together with the key generation ratio.It is therefore believed that the method pays a way for Gbit/s physical key distribution.

Integrated sensing and communication in an optical fibre

The integration of high-speed optical communication and distributed sensing could bring intelligent functionalities to ubiquitous optical fibre networks,such as urban structure imaging,ocean seismic detection,and safety monitoring of underground embedded pipelines.This work demonstrates a scheme of integrated sensing and communication in an optical fibre(ISAC-OF)using the same wavelength channel for simultaneous data transmission and distributed vibration sensing.The scheme not only extends the intelligent functionality for optical fibre communication system,but also improves its transmission performance.A periodic linear frequency modulation(LFM)light is generated to act as the optical carrier and sensing probe in PAM4 signal transmission and phase-sensitive optical time-domain reflectometry(Φ-OTDR),respectively.After a 24.5 km fibre transmission,the forward PAM4 signal and the carriercorrespondence Rayleigh backscattering signal are detected and demodulated.Experimental results show that the integrated solution achieves better transmission performance(~1.3 dB improvement)and a larger launching power(7 dB enhancement)at a 56 Gbit/s bit rate compared to a conventional PAM4 signal transmission.Meanwhile,a 4m spatial resolution,4.32-nε/√Hz strain resolution,and over 21 kHz frequency response for the vibration sensing are obtained.The proposed solution offers a new path to further explore the potential of existing or future fibre-optic networks by the convergence of data transmission and status sensing.In addition,such a scheme of using shared spectrum in communication and distributed optical fibre sensing may be used to measure non-linear parameters in coherent optical communications,offering possible benefits for data transmission.

Photonic generation of microwave signals with tunabilities

Microwave photonic signal generation schemes based on the frequency to time mapping and external modulation are reviewed.We concentrate on those configurations that can provide tunability of frequency,phase of signal,modulation formats(i.e.,2PSK,2FSK,etc.),as well as pulse shapes(i.e.,UWBs-,triangle-and arbitraryshaped,etc.).

Covert wireless communication using massive optical comb channels for deep denoising

Covert wireless communications are unprecedentedly vital for security and privacy of individuals,government,and military bodies.Besides encryption,hiding signal transmission deeply under noise background highly proliferates the covertness in the physical layer.A deep signal hiding leads to a low interception probability at the interceptor but a poor data recovery at the receiver.To ensure both high covertness and high-fidelity recovery,massive and dense optical comb channels are utilized for deep denoising through the analog spectrum convolution.Using an external modulation-based optical frequency comb(OFC)and a single detection branch,the available optical comb channels can sustainably scale up by breaking or greatly mitigating physical bottlenecks on immense hardware and spectrum requirements.Thus,a striking signal-to-noise ratio(SNR)rise can be achieved for deep denoising.Combination of 1024 comb channels(the first parallel comb channel number beyond 1000)and the analog spectrum convolution enable a record SNR enhancement of 29 dB for a microwave signal with a 10.24 GHz bandwidth and a 10 Mbit/s data rate,which is deeply hidden below the in-band noises by 18 dB or even 30 dB in both the frequency and time domains.This method opens a new avenue for covert communications.

Chaos synchronization of semiconductor lasers over 1040-km fiber relay transmission with hybrid amplification

Optical chaos communication and key distribution have been extensively demonstrated with high-speed advantage but only within the metropolitan-area network range of which the transmission distance is restricted to around 300 km.For secure-transmission requirement of the backbone fiber link,the critical threshold is to realize long-reach chaos synchronization.Here,we propose and demonstrate a scheme of long-reach chaos synchronization using fiber relay transmission with hybrid amplification of an erbium-doped fiber amplifier(EDFA)and a distributed fiber Raman amplifier(DFRA).Experiments and simulations show that the hybrid amplification extends the chaos-fidelity transmission distance thanks to that the low-noise DFRA suppresses the amplified spontaneous emission noise and self-phase modulation.Optimizations of the hybrid-relay conditions are studied,including launching power,gain ratio of DFRA to EDFA,single-span fiber length,and number of fiber span.A 1040-km chaos synchronization with a synchronization coefficient beyond 0.90 is experimentally achieved,which underlies the backbone network-oriented optical chaos communication and key distribution.

All-optical processing to optical and radio frequency(RF) signals

Signal processing is always the heart of the overall information technology and industry,providing enabling solutions for the processing,understanding,learning,retrieval,mining,and extraction of information from different signals.Regarding the all-optical signal processing,it dates back to the 1980s when the electronic bottleneck

Ultra-wideband Waveguide-coupled Photodiodes Heterogeneously Integrated on a Thin-film Lithium Niobate Platform

With the advantages of large electro-optical coefficient,wide transparency window,and strong optical confinement,thin-film lithium niobate(TFLN)technique has enabled the development of various high-performance optoelectronics devices,ranging from the ultra-wideband electro-optic modulators to the high-efficient quantum sources.However,the TFLN platform does not natively promise lasers and photodiodes.This study presents an InP/InGaAs modified uni-traveling carrier(MUTC)photodiodes heterogeneously integrated on the TFLN platform with a record-high 3-dB bandwidth of 110 GHz and a responsivity of 0.4 A/W at a 1,550-nm wavelength.It is implemented in a wafer-level TFLN-InP heterogeneous integration platform and is suitable for the large-scale,multi-function,and high-performance TFLN photonic integrated circuits.

Single-end hybrid Rayleigh Brillouin and Raman distributed fibre-optic sensing system

Backscattered lightwaves from an optical fibre are used to realise distributed fibre optic sensing(DFOS)systems for measuring various parameters.Rayleigh,Brillouin,and Raman backscattering provide different sensitivities to different measurands and have garnered the attention of researchers.A system combining the three principles above can effectively separate the measured strain and temperature completely as well as provide measurements of both dynamic and static parameters.However,the combined system is extremely complicated if the three systems are independent of each other.Hence,we propose a single-end hybrid DFOS system that uses two successive pulses to realise the Brillouin amplification of Rayleigh backscattering lightwaves for combining Rayleigh and Brillouin systems.A 3-bit pulse-coding method is employed to demodulate the Raman scattering of the two pulses to integrate Raman optical time-domain reflectometry into the hybrid system.Using this hybrid scheme,a simultaneous measurement of multiple parameters is realised,and a favourable measurement accuracy is achieved.

Transmission and demodulation of multi-polarization-multiplexed signals

We propose the configuration of signal multiplexing with four polarization states and investigate its transmission performance over single-mode fiber links.Using coherent detection and digital signal processing,a demodulation scheme for four-polarization-multiplexed(4PM)system is presented.We discuss the impact of crosstalk from polarization mode dispersion and polarization beam splitter misalignment on the proposed 4PM system.Furthermore,the transmission distance could be doubled to*50 km by employing feedback decision equalizers.

Photonic microwave filters with ultra-high noise rejection [Invited]

As a key figure-of-merit for high-performance microwave filters, the out-of-band noise rejection is of critical importance in a wide range of applications. This paper overviews the significant advances in photonic microwave filters(PMFs) having ultra-high rejection ratios for out-of-band noise suppression over the last ten years.Typically, two types of PMFs, the bandpass and bandstop ones, are introduced with fundamental principles,detailed approaches, and then cutting-edge results for noise rejection. Ultra-high noise rejection ratios of ～80 d B and >60 dB have been demonstrated for single-passband and single-stopband PMFs, respectively, which are comparable with the state-of-the-art electronic filters operating in stringent conditions. These PMFs are also characterized by wide frequency coverage, low frequency-dependent loss, and strong immunity to electromagnetic interference due to the intrinsic features from the advanced photonics technology.

Flexible polarization demultiplexing method based on an adaptive process noise covariance Kalman filter

A flexible polarization demultiplexing method based on an adaptive Kalman filter（AKF） is proposed in which the process noise covariance has been estimated adaptively. The proposed method may significantly improve the adaptive capability of an extended Kalman filter（EKF） by adaptively estimating the unknown process noise covariance. Compared to the conventional EKF, the proposed method can avoid the tedious and time consuming parameter-by-parameter tuning operations. The effectiveness of this method is confirmed experimentally in 128 Gb/s 16 QAM polarization-division-multiplexing（PDM） coherent optical transmission systems. The results illustrate that our proposed AKF has a better tracking accuracy and a faster convergence（about 4 times quicker）compared to a conventional algorithm with optimal process noise covariance.

Covert wireless communication using massive optical comb channels for deep denoising: erratum

The position of the parentheses in the original manuscript is incorrect.This is a clerical error,and all of the theories and conclusions are unchanged by this correction.

Misalignments among stacked layers of metamaterial terahertz absorbers

Misalignment among stacked layers of absor- bers is inevitable in practice. Adverse effects induced by this undesired factor was investigated and analyzed in this paper. The absorption responses of thin terahertz metama- terial （MM） absorber with different degree of misalign- ment were simulated by finite-difference time-domain （FDTD） method under both transverse magnetic （TM） and transverse electric （TE） polarization. Results show that slight misalignment deteriorates absorption response due to the decreased spatial resolution. The analyses are given in terms of the magnetic field distribution in the cross section. In addition, the depravation is changed with polarization, which depends on the direction of excursion.

Editorial Foreword-Light:Advanced Manufacturing

Light:Advanced Manufacturing(LAM),a journal affiliated to Light:Science&Applications(Light)Group,has finally come into realization after two years′endeavour.Advanced manufacturing is a comprehensive discipline which has its root in traditional manufacturing,but applies to industrial manufacturing and engineering all the latest advancements of other sciences and technologies(especially information,communication,computer,sensing,artificial intelligence and management science).Thirty years after its establishment,the discipline is focused on the direction of pushing manufacturing to be more precise,more network-based,more integrated,more intelligent,more flexible,more personalised,more energy-efficient and cleaner.In the 21st century,advanced manufacturing is even more integrated with the development and application of the Internet,big data,and artificial intelligence,and considered as a priority for development in many countries.