Delay Modulation Research Articles

The autonomous error suppression method based on phase delay modulation for the SINS

The autonomous error suppression method based on phase delay modulation for the SINS

Anti-machine-learning-attack strong PUF design based on multi-path delay selection strategy

Physical unclonable functions (PUF) have significant potential for application in information security. However, strong PUFs are vulnerable to machine learning (ML) modeling attacks, which severely limit their application in device authentication. Despite a variety of resistance techniques, strong PUFs suffer from hardware cost and stability deficiencies. This study proposes an anti-machine-learning-attack strong PUF based on a multi-path delay selection strategy through research on the entropy source of a strong PUF and the delay signal selection mechanism. First, we constructed a deviation source circuit based on multiplexers to increase the diversity of the delay signal transmission paths. Second, we constructed a delay selection circuit based on the logic gates. This circuit dynamically selects the delay signals with the same transmission path in the deviation source using AND and OR gates. Subsequently, the deviation source and delay selection circuits were utilized to construct the delay module, and the interconnection module was inserted between the delay modules to achieve alternating appearances of different types of logic gates along the delay path. Finally, RS flip-flops were employed to make decisions on the bias signals with the same delay path, and the final response was output through an XOR operation. The proposed PUF was implemented on a Xilinx Artix-7 FPGA, and the prediction accuracy of the four typical ML models was below 59 % (with 500,000 challenge-response pairs as the training set). Moreover, the proposed PUF structure is scalable and exhibits better performance in terms of hardware cost and stability than existing classic structures.

Ways to Organize and Identify Steganographic Channels in IP Networks

The article is devoted to an overview of network steganography methods that can be used to build hidden message transmission channels in IP networks, as well as methods aimed at identifying such hidden channels. The article gives the concept of a stegocontainer, and provides classification of network steganography methods. The article discusses the following methods of organizing hidden channels: the method of changing the contents of network packet headers, the Transcoding Steganography (TranSteg) method, the delay modulation method, the Lost Audio Packet Steganography (LACK) method, the Retransmission Steganography (RSTEG) method. In the review of the method of changing the contents of network packet headers, the principle of implementing changes in values in some service fields of IP (Internet Protocol) and TCP (Transmission Control Protocol) packet headers, which do not lead to data transmission failure, are considered. In the overview of the TranSteg method, the principle of transcoding the contents of network packets delivering real-time traffic is considered in order to free up space in the packet, which will be used to transmit hidden information. In the review of the delay modulation method, the principles of hidden message encoding are considered, which is carried out by changing the delay value of sending packets in the network. In the review of the LACK method, the mechanism of deliberate retention of RTP packets with an embedded steganographic message is considered. In the review of the RSTEG method, the principle of TCP segment exchange is considered, which provides the possibility of transmitting a steganogram. A number of parameters are given by which it is possible to conclude that there is a hidden channel in the network. The applicability of statistical methods and the methods with a classifier for detecting hidden channels in IP networks is considered. The expediency of implementing statistical methods and methods with a classifier in integration with systems for capturing and analyzing network traffic is indicated.

Engineering Modular DNA Reaction Networks for Signal Processing.

Diversified molecular information-processing methods have significant implications for nanoscale manipulation and control, monitoring and disease diagnosis of organisms, and direct intervention in biological activities. However, as an effective approach for implementing multifunctional molecular information processing, DNA reaction networks (DRNs) with numerous functionally specialized molecular structures have challenged them on scale design, leading to increased network complexity, further causing problems such as signal leakage, attenuation, and cross-talk in network reactions. Our study developed a strategy for performing various signal-processing tasks through engineering modular DRNs. This strategy is based on a universal core unit with signal selection capability, and a time-adjustable signal self-resetting module is achieved by combing the core unit and self-resetting unit, which improves the time controllability of modular DRNs. In addition, multi-input and -output signal cross-catalytic and continuously adjustable signal delay modules were realized by combining core and threshold units, providing a flexible, precise method for modular DRNs to process the signal. The strategy simplifies the design of DRNs, helps generate design ideas for large-scale integrated DRNs with multiple functions, and provides prospects in biocomputing, gene regulation, and biosensing.

Thin Glass Substrates with Through-Glass Vias

Glass substrates with fine-pitch through-glass via (TGV) technology gives an attractive approach to wafer level packaging and systems integration. Glass can be made in very thin sheets (<100 um thick) which aids in integration and eliminates the need for back-grinding operations. Electrical and physical properties of glass have many attractive attributes such as low RF loss, the ability to adjust thermal expansion properties, and low roughness with excellent flatness to achieve fine L/S. Furthermore, glass can be fabricated in panel format to reduce manufacturing costs. The biggest challenge to adopting glass as a packaging substrate has been the existence of gaps in the supply chain, caused primarily by the difficulty in handling large, thin glass substrates using standard automation and processing equipment. This paper presents a temporary bonding technology that allows the thin glass substrates to be processed in a semiconductor fab environment without the need to modify existing equipment. There have been a number of research articles published over the past several years showing the advantages that glass based solutions can bring to packaging and systems integration including RF front ends, interposers, MEMs devices, and integrated photonics. [1-10]. RF applications of glass in particular are gaining interest for use as a substrate for filters, switches, true time delay modules, and millimeter antenna arrays. The advantages include low insertion loss as the frequency increases above a few GHz relative to Si-based solutions and higher integration density compared to laminates and ceramics. Furthermore, numerous articles have shown the ability of glass to pass typical reliability testing including thermal shock and drop tests [e.g. 5, 8]. The challenge has been addressing how to make the transition from small scale demonstration to providing solutions that can transition into high volume manufacture environment. The overview of an approach for a new thin glass handling strategy has been reported previously. [12,13] The approach utilizes a thin inorganic adhesion layer to temporarily bond a thin glass wafer to a silicon or glass handle wafer (Si handle wafer is the primary approach). The thin glass substrate, which may contain through-glass vias (TGVs), is then processed through downstream steps such as via fill, CMP, RDL/passive deposition, lithography and bumping. The bond is stable (remains temporary and without outgassing) to over 400 °C. Utilizing a Si handle wafer allows the thin glass to be processed leveraging existing equipment and process flows, with only a mechanical de-bond to yield finished substrates. A key aspect of this handling solution, is that it addresses the gaps in the supply chain that have adversely affected the adoption of glass-based solutions. It is important that this solution integrate seamlessly into typical back-end processes, which includes via fill, CMP, RDL, de-bond and dicing/singulation without significant changes or upgrades required of existing process equipment. In this paper, we will describe the advances made to show the application of this temporary bond approach to leverage existing capabilities of standard processing equipment. In particular, we will show the ability to provide void free via fill using standard wafer-based approaches, such as blind via technology and ability to apply existing chemo-mechanical polishing (CMP) processes for Cu overburden removal and CMP. We will demonstrate the ability to provide top and bottom surface metallization/RDL using standard de-bond approaches as well as application of industry standard tools for dicing/singulation.

Viaffirm TM Thin Glass Handling Technology

Thin glass provides attractive solutions for emerging high frequency applications and particularly those related to the rollout of 5G. The electrical and physical properties of glass enable low RF loss, the ability to adjust thermal expansion properties, and low roughness with excellent flatness to achieve fine L/S and smaller form factors. The scalability of glass also provides opportunities to establish cost-effective solutions. There have been a number of research articles published over the past several years showing the advantages that glass based solutions can bring to packaging and systems integration including RF front ends, interposers, MEMs devices, and integrated photonics. [1-10]. RF applications of glass in particular are gaining interest for use as a substrate for filters, switches, true time delay modules, and millimeter antenna arrays. The advantages include low insertion loss relative to Si-based solutions and higher integration density compared with laminates and ceramics. Furthermore, numerous articles have shown the ability of glass to provide reliable solutions. These tests have included, HAST, thermal shock and drop tests [e.g. 5, 8]. The biggest challenge to adopting glass-based solutions has been the existence of gaps in the supply chain, caused primarily by the difficulty in handling large, thin glass substrates using standard automation and processing equipment. A new thin glass handling approach, Viaffirm TM, has been recently developed. [12,13] The approach utilizes a thin inorganic adhesion layer to temporarily bond a thin glass wafer to a silicon or glass handle wafer (Si handle wafer is the primary approach). The thin glass substrate, which may contain through-glass vias (TGVs), is then processed through downstream steps such as via fill, CMP, RDL/passive deposition, lithography and bumping. The bond is stable (remains temporary and without outgassing) to over 400 °C. Utilizing a Si handle wafer allows the thin glass to be processed leveraging existing equipment and process flows, with only a mechanical de-bond to yield finished substrates. In previous publications, the basic process has been described. Here, we will show advancements and application of this technology, with and without TGV, to seamlessly interface with the supply chain to fabricate next generation thin glass solutions for applications including photonic substrates, RF filters and antennas. The process is available for multiple glass types including alumino-borosilicate glasses with coefficient of thermal expansion that matches silicon, as well as ultra-low loss materials like fused silica (FS). Leveraging the precision bond Viaffirm allows you to fabricate FS wafers down to 100 um thick. The approach is enabling low loss solutions in electronically steerable antenna (ESA), radar arrays, MEMS, sensors and packaging substrates. A particularly attractive use for glass is in 5G applications due to its material properties, especially at high frequencies including mm-Wave applications. First, it is stable with respect to environmental changes (e.g. temperature and humidity). Also, glass is an isotropic material by nature, which means its properties are stable in all 3 axes. This can be very important in applications such as phased array antennas where you might have an 8x8 array of patch antennas, and require them all to perform predictably and with minimal variation to achieve desired results, such as in beam steering. Recent work was done to fabricate a multi-layer glass based Electronically Steerable Array (ESA) antenna with a design transmit signal of approximately 29.5 GHz. Additional architectural enhancements in this novel approach enable a dramatic reduction in the number of controllable elements in the array and therefore reduce the number of MMICs needed for antenna steering, resulting in a design with reduced size, weight, power and cost relative to more conventional approaches. [14] The approach utilized a multi-layer glass-based feed network to control 8x8 patch arrays. Analysis shows that by utilizing glass instead of PCB solutions, dramatic reduction in electrical loss are realized. By leveraging Viaffirm technology, thin glass solutions are available to address these and other mmWave applications important in 5G and beyond.

An Agent-Based Model to Reproduce the Boolean Logic Behaviour of Neuronal Self-Organised Communities through Pulse Delay Modulation and Generation of Logic Gates.

The human brain is arguably the most complex "machine" to ever exist. Its detailed functioning is yet to be fully understood, let alone modelled. Neurological processes have logical signal-processing and biophysical aspects, and both affect the brain's structure, functioning and adaptation. Mathematical approaches based on both information and graph theory have been extensively used in an attempt to approximate its biological functioning, along with Artificial Intelligence frameworks inspired by its logical functioning. In this article, an approach to model some aspects of the brain learning and signal processing is presented, mimicking the metastability and backpropagation found in the real brain while also accounting for neuroplasticity. Several simulations are carried out with this model to demonstrate how dynamic neuroplasticity, neural inhibition and neuron migration can reshape the brain's logical connectivity to synchronise signal processing and obtain certain target latencies. This work showcases the importance of dynamic logical and biophysical remodelling in brain plasticity. Combining mathematical (agents, graph theory, topology and backpropagation) and biomedical ingredients (metastability, neuroplasticity and migration), these preliminary results prove complex brain phenomena can be reproduced-under pertinent simplifications-via affordable computations, which can be construed as a starting point for more ambitiously accurate simulations.

High‐Sensitive and Background‐Free Coherent Anti‐Stokes Raman Scattering Microscopy Using Delay Modulation

AbstractCoherent anti‐Stokes Raman scattering (CARS) microscopy has demonstrated a powerful platform for label‐free, non‐invasive, and chemically specific imaging of biological samples. However, the non‐resonant background limits its ability to detect weak Raman signals. Here, an approach to eliminate the non‐resonant background in CARS using delay modulation (DM) is presented, which is enabled by an acousto‐optic modulator and spectral focusing. The results demonstrate that DM‐CARS reduces the non‐resonant background by 10 times and improves detection sensitivity by 100‐fold over normal CARS. It also shows that DM‐CARS has potential applications in tracking heavy water metabolism in bacteria for antimicrobial susceptibility testing and imaging liver tumor tissues. Furthermore, a handheld DM‐CARS device has also demonstrated for in vivo imaging, which can be beneficial in various applications.

Study on the influence of mechanism dispersion on transient recovery voltage distribution of modular DC vacuum circuit breakers

AbstractA simulation analysis and an experiment are carried out to investigate how the gap difference between the breaks of a direct current vacuum circuit breakers with multi‐breaks (MB‐DC VCB) caused by the mechanism dispersion of the breaker influences the distribution of TRV among the breaks. An interruption model of MB‐DC VCB, combining the continuous transition model, is established to analyse the rising rate of transient recovery voltage and the dielectric strength recovery speed of the breaks for MB‐DC VCB under different gap difference conditions. Based on the experimental platform of dual break DC vacuum circuit breaker breaking, the correctness of the simulation model is verified on a DC VCB with the double‐breaks interruption experimental platform. Moreover, a model is applied to the non‐synchronous interruption simulation of a DC VCB with three‐breaks. The relationship between the TRVs of the breaks under different gap difference conditions is analysed using the comparative analysis method, obtaining the maximum gap difference at the moment of breaking failure. The results of this study show that large‐gap breaks have a higher TRV than small‐gap breaks (the fracture of the action delay module), with double fractures reaching 1.4 times and triple fractures reaching a maximum of 1.52 times; the ability of small‐gap breaks to withstand TRV is weak, giving rise to re‐breakdown or even interruption failure; as the number of fractures increases, the maximum gap difference also increases. Improving the synchronous interruption ability of the MB‐DC VCB is conducive to improving the interruption performance and interruption success rate of this type of a circuit breaker.

A self-driven, microfluidic, integrated-circuit biosensing chip for detecting four cardiovascular disease biomarkers

Cardiovascular diseases (CVDs) claimed the lives of nearly 21 million people worldwide in 2021, accounting for 30% of global deaths. However, one in five CVD patients is unaware that they have the disease, emphasizing the need for accurate biomarker monitoring. Herein we developed an integrated microfluidic system (IMS) for rapid quantification of four CVD biomarkers, including N-terminal pro B-type natriuretic peptide (NT-proBNP), fibrinogen, cardiac troponin I (cTnI), and C-reactive protein (CRP)- via aptamer-coated interdigitated electrodes (IDE) with integrated circuits (IC) and a self-driven IMS for sample treatment. The device was composed of plasma filtration, metering, and fluidic delay modules, and the former could extract 45% of plasma from a 20-μL blood sample; the metering module could quantify 5 μL of plasma within 90 s. Subsequently, the plasma was transported to a detection chamber, where IC-based IDE sensors made measurements within 5 min. The entire 15-min process allowed us to evaluate biomarkers across a wide dynamic range: NT-proBNP (0.1–10,000 pg/mL), fibrinogen (50-1,000 mg/dL), cTnI (0.1–10,000 pg/mL), and CRP (0.5-9 mg/L). Given that spiked blood samples were measured with reasonable accuracy (>80%), the IMS could see utility in CVD risk assessment and personalized medicine.

Learnable axonal delay in spiking neural networks improves spoken word recognition.

Spiking neural networks (SNNs), which are composed of biologically plausible spiking neurons, and combined with bio-physically realistic auditory periphery models, offer a means to explore and understand human auditory processing-especially in tasks where precise timing is essential. However, because of the inherent temporal complexity in spike sequences, the performance of SNNs has remained less competitive compared to artificial neural networks (ANNs). To tackle this challenge, a fundamental research topic is the configuration of spike-timing and the exploration of more intricate architectures. In this work, we demonstrate a learnable axonal delay combined with local skip-connections yields state-of-the-art performance on challenging benchmarks for spoken word recognition. Additionally, we introduce an auxiliary loss term to further enhance accuracy and stability. Experiments on the neuromorphic speech benchmark datasets, NTIDIDIGITS and SHD, show improvements in performance when incorporating our delay module in comparison to vanilla feedforward SNNs. Specifically, with the integration of our delay module, the performance on NTIDIDIGITS and SHD improves by 14% and 18%, respectively. When paired with local skip-connections and the auxiliary loss, our approach surpasses both recurrent and convolutional neural networks, yet uses 10 × fewer parameters for NTIDIDIGITS and 7 × fewer for SHD.

Flexible all-optical terahertz switch based on electromagnetically induced transparent-like metamaterial

The electromagnetically induced transparent-like metamaterials have received much attention because of their excellent slow-light properties and strong nonlinear effects. They have many promising applications in novel terahertz functional devices, high-sensitivity sensors, and optical storages. In this paper, a flexible terahertz switching device based on the electromagnetically induced transparent-like effect was proposed. The device exhibited a significant slow light phenomenon without pumped laser. Meanwhile, it is demonstrated that the device has a large modulation depth and excellent tunable slow light performance with low-power pumped laser. Its amplitude modulation depth can reach 60.4% and the group delay modulation can reach 32.5 ps. And the minimum group velocity of the device in slow terahertz light can reach 0.69 × 105 m/s. Moreover, the flexible substrate of the proposed device is not easily damaged. It makes the device suited for more complex environments well. Therefore, the device will have great potential for future research on high-performance terahertz switching devices.

High-Resolution and Wide-Swath SAR Imaging with Space–Time Coding Array

To achieve high-resolution and wide-swath (HRWS) synthetic aperture radar (SAR) images, this paper focuses on resolving the problem of separating range-ambiguous echoes with the space–time coding (STC) array. At the modeling stage, the transmit elements and pulses of the STC array are configured with time delay and phase coding modulation, which introduces extra degrees of freedom (DOFs) in the transmit domain. To separate the echoes corresponding to different range-ambiguity regions, the equivalent transmit beamforming is performed in the two-dimensional space–frequency domain. Moreover, in order to compensate for the loss of range resolution during the beamforming progress, the frequency splicing method is proposed. At the analysis stage, the distributed target simulation is provided to demonstrate the effectiveness of obtaining HRWS SAR images in the STC radar. Additionally, the performance of resolving range ambiguity is compared with the traditional radar in terms of the range-ambiguity-to-signal ratio (RASR).

Frozen mode regime in an optical waveguide with a distributed Bragg reflector

We introduce a glide symmetric optical waveguide exhibiting a stationary inflection point (SIP) in the Bloch wavenumber dispersion relation. An SIP is a third-order exceptional point of degeneracy (EPD) where three Bloch eigenmodes coalesce to form a so-called frozen mode with vanishing group velocity and diverging amplitude. We show that the incorporation of chirped distributed Bragg reflectors and distributed coupling between waveguides in the periodic structure facilitates the SIP formation and greatly enhances the characteristics of the frozen mode regime. We confirm the existence of an SIP in two ways: by observing the flatness of the dispersion diagram and also by using a coalescence parameter describing the separation of the three eigenvectors collapsing on each other. We find that, in the absence of losses, both the quality factor and the group delay at the SIP grow with the cubic power of the cavity length. The frozen mode regime can be very attractive for light amplification and lasing in optical delay lines, sensors, and modulators.

High-precision data acquisition for free-space continuous-variable quantum key distribution.

Data acquisition in a continuous-variable quantum key distribution (CV-QKD) system is a necessary step to obtain secure secret keys. And the known data acquisition methods are commonly based on the assumption that the channel transmittance is constant. However, the channel transmittance in free-space CV-QKD fluctuates during the transmission of quantum signals, and the original methods are not applicable in this scenario. In this paper, we propose a data acquisition scheme based on the dual analog-to-digital converter (ADC). In this scheme, two ADCs with the same sampling frequency as the pulse repetition rate of the system and a dynamic delay module (DDM), which are used to construct a high-precision data acquisition system, eliminate the effect of transmittance fluctuation by a simple division operation of the data from the two ADCs. Simulation and proof-of-principle experimental results show that the scheme is effective for free-space channels and can achieve high-precision data acquisition under the condition of fluctuation of channel transmittance and very low signal-to-noise ratio (SNR). Furthermore, we introduce the direct application scenarios of the proposed scheme for free-space CV-QKD system and verify their feasibilities. This method is of great significance to promote the experimental realization and practical application of free-space CV-QKD.

Laminar chaos in systems with quasiperiodic delay.

A type of chaos called laminar chaos was found in singularly perturbed dynamical systems with periodic time-varying delay [Phys. Rev. Lett. 120, 084102 (2018)]0031-900710.1103/PhysRevLett.120.084102. It is characterized by nearly constant laminar phases, which are periodically interrupted by irregular bursts, where the intensity levels of the laminar phases vary chaotically from phase to phase. In this paper, we demonstrate that laminar chaos can also be observed in systems with quasiperiodic delay, where we generalize the concept of conservative and dissipative delays to such systems. It turns out that the durations of the laminar phases vary quasiperiodically and follow the dynamics of a torus map in contrast to the periodic variation observed for periodic delay. Theoretical and numerical results indicate that introducing a quasiperiodic delay modulation into a time-delay system can lead to a giant reduction of the dimension of the chaotic attractors. By varying the mean delay and keeping other parameters fixed, we found that the Kaplan-Yorke dimension is modulated quasiperiodically over several orders of magnitudes, where the dynamics switches quasiperiodically between different types of high- and low-dimensional types of chaos.

Time delay interferometry with a transfer oscillator.

In this work, we experimentally perform time delay interferometry by using a transfer oscillator, which is capable of reducing the laser frequency noise and the clock noise simultaneously in the post processing. The iodine frequency reference is coherently downconverted to the microwave frequency using a laser frequency comb. The residual noise of the downconversion network is 5 × 10-6Hz/Hz1/2 at 0.7 mHz, and 4 × 10-6Hz/Hz1/2 at 0.1 Hz, indicating high homology between the optical frequency and the microwave frequency. We carry out time delay interferometry with the aid of the electrical delay module, which can introduce large time delays. The results show that the laser frequency noise and the clock noise can be reduced simultaneously by ten and three orders of magnitude, respectively, in the frequency band from 0.1 mHz to 0.1 Hz. The performance of the noise reduction can reach 6 × 10-8Hz/Hz1/2 at 0.1 mHz, and 7 × 10-7Hz/Hz1/2 at 1 mHz, meeting the requirements of the space-borne gravitational wave detection. Our work will be able to offer an alternative method for the frequency comb-based time delay interferometry in the future space-borne gravitational wave detectors.

2-D beamforming system based on photonic lantern and few-mode fiber Bragg grating

In this paper, a 2-D beamforming system based on the photonic lantern (PL) and few-mode fiber Bragg grating (FM-FBG) with a 3 × 3 antenna array is proposed. The FM-FBG is produced by the femtosecond laser point-by-point method, which is flexible and simple; moreover, the 2-D time delay regulation can be realized with different positions of FM-FBG by a single wavelength and single-stage optical true time delay (OTTD) modules to complete the 2-D beam scanning, which reduces the system cost, complexity and simplifies the system structure. The effects of different types of PLs on the system are investigated with the results that the channel amplitude dither of the 2-D beamforming system using non-mode-selective PLs is less than 1.5 dB, and the main lobe beamwidth and sidelobe level are smaller than those of the mode-selective PL system. In addition, the effect of the polarization state of optical on the gain of the system is studied, and the experiment results show that the overall gain of the system is improved by 2.27 dB when we adjust the optical polarization state to the optimum. Under this best-adjusted polarization state, we construct a 2-D beamforming system based on the non-mode-selective PL with time delay steps of (12 ps, 10 ps), and the elevation and azimuth angles are achieved by switching the operating state of the optical switch for the scan ranges of 0°–60° and 0°–35°, respectively.

Autoignition delay modulation by high-frequency thermoacoustic oscillations in reheat flames

This paper investigates the sensitivity of the autoignition delay in reheat flames to acoustic pulsations associated with high-frequency transverse thermoacoustic oscillations. A reduced order model for the response of purely autoignition-stabilised flames to acoustic disturbances is compared with experimental observations. The experiments identified periodic flame motion associated with high-amplitude transverse limit-cycle oscillations in an atmospheric pressure reheat combustor. This flame motion was assumed to be the result of a superposition of two flame-acoustic coupling mechanisms: autoignition delay modulation by the oscillating acoustic field and displacement and deformation of the flame by the acoustic velocity. The reduced order model coupled to reaction kinetics calculations reveals that a significant portion of the observed flame motion can be attributed to autoignition delay modulation. The ignition position responds instantaneously to the acoustic pressure at the time of ignition, as observed experimentally. The model also provides insight into the importance of the history of acoustic disturbances experienced by the fuel-air mixture prior to ignition. Due to the high-frequency nature of the instability, a fluid particle can experience multiple oscillation cycles before ignition. The ignition delay responds in-phase with the net-acoustic perturbation experienced by a fluid particle between injection and ignition. These findings shed light on the underlying mechanisms of the flame motion observed in experiments and provide useful insight into the importance of autoignition delay modulation as a driving mechanism of high-frequency thermoacoustic instabilities in reheat flames.

Research on the Performance of Multimode Optical Chaotic Secure Communication System With Multidimensional Keys and a Complex Entropy Source

In this paper, we design an optical chaotic secure communication system with multi-dimensional keys and a complex entropy source, which can allow secure communication working in different modes such as unicast, multicast, and broadcast. In the proposed scheme, amplified spontaneous emission (ASE) noise of the erbium-doped fiber amplifier (EDFA) with sufficient randomness is used as an entropy source to improve the security of the system. And by using the electro-optic delay feedback loops, the key spaces are introduced and the phase distortion is generated, then the data are masked in both phase and intensity fields. As a frequency-dependent group delay (FDGD) module, Gires-Tournois interferometer (G-T I) in the feedback loop can effectively hide the time delay signature (TDS) and achieve additional 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">36</sup> key spaces. The influence of different key mismatches on decryption function is numerically investigated, and the results indicate that the broadband nature of ASE noise makes the TDS a very sensitive encryption key, which increases the difficulty of illegal third parties stealing information. And with the help of the wavelength converter and wavelength division multiplexer, secure communication in various modes is successfully realized, which greatly improves the communication efficiency and is suitable for various security places.