Crosstalk Characteristics Research Articles

Optical router based on a phase-coding multiplexed collinear holographic storage system

This paper analyzes the distribution characteristics of crosstalk in a phase-coded multiplexed collinear holographic storage system and realizes an optical router by this characteristic. The system employs collinear holographic storage technology to cache the signals of the optical router in the holographic storage material. Different routing addresses are represented by the phase code. The system reads the signals in the holographic storage material and accomplishes the routing function. The benefit of this approach is that it minimizes the loss of optical signal and possesses robust anti-interference capability, offering an efficient solution in the development of optical routing.

Mid-infrared seven-core chalcogenide fiber with ultra-large mode field area and high beam quality

A seven-core chalcogenide fiber with an ultra-large mode field for mid-infrared range of 2.5–11 μm is designed and fabricated. Through manipulation of the core radius and pitch in the seven-core configuration, we are engaged in a comprehensive exploration of crosstalk characteristics and the mode field area (MFA). In addition, the relationship between the parameters of seven-core fiber for infrared and the beam quality of the output laser is analyzed for the first time. A theoretical MFA of 8914 μm2 can be calculated with a core radius of 24 μm and the pitch of 50 μm. This impressive MFA is realized through the deployment of an improved drilling technique in the fabrication of a Ge–As–Se seven-core fiber. The fiber has a relatively low loss at the wavelength range of 2.5–11 μm, and the minimum loss is 1.4 dB m−1 at 8.5 μm. The measured MFA of the fiber at 10.6 μm is 7364 μm2, which is 6.2 times higher than that of traditional stepped single-core fiber, but slightly lower than the theoretical value. The power delivery capability of the fiber has been significantly improved about two times compared with that of single-core fiber. The output beam quality factor M 2 is calculated as 1.13. In all, the seven-core fiber exhibits substantial potential for high-power laser propagation with high quality and flexibility.

Research on transmission and crosstalk characteristics of a new type of through silicon via and multilayer through silicon via

In this work, a new type of bar-coaxial ring TSV (B-coaxial ring TSV) structure was proposed. This study used three-dimensional electromagnetic simulation software for analysis. Firstly, the conventional Bar-TSV (B-TSV) structure and the B-coaxial ring TSV structure were modeled, and their S-parameter results were compared. Our results indicated that the B-coaxial ring TSV structure had better transmission characteristics and crosstalk resistance. Secondly, by simulating of the B-coaxial ring TSV structure and the coaxial ring-tapered TSV structure, we proposed how to choose different structures for different application scenarios. Thirdly, the influence of some structural parameters of the B-coaxial ring TSV structure on the transmission performance was studied. Finally, the multilayer TSV structures of conventional B-TSV, B-coaxial ring TSV and coaxial ring-tapered TSV were studied respectively, and their performance was compared and analyzed.

Ultra-Bend-Resistant 4-Core Simplex Cable Used for Short-Reach Dense Spatial Division Multiplexing Optical Transmission.

We optimized and fabricated an ultra-bend-resistant 4-core simplex cable (SXC) employing 4-core multicore fiber (MCF) suitable for short-reach dense spatial division multiplexing (DSDM) optical transmission in the O-band. The characteristics of transmission loss, macro-bending and cross-talk (XT) between adjacent cores after cabling were firstly clarified. By introducing the trapezoid index and optimizing the cabling process, the maximum values of added XT of 1.17 dB/km due to 10 loops with a bending radius of 6 mm imposed over the 4-core SXC and a macro-bending loss of 0.37 dB/10 turns were, respectively, achieved.P Then, the optical transmission with low bit error rate (BER) was presented using a 100GBASE-LR4 transceiver over the 1.2 km long 4-core SXC. The excellent bending resistance of the 4-core SXC may pave the way for a reduction in space pressure and increase in access density on short-reach optical interconnect (OI) based on DSDM.

High dynamic range 3D shape measurement based on crosstalk characteristics of a color camera.

Fringe projection profilometry (FPP) has been widely used in many fields due to its fast speed, high accuracy and full-field characteristics. However, it is still a challenging problem to deal with high dynamic range (HDR) objects for traditional FPP, which utilizes a single exposure time or a single projection intensity. Overexposure will occur in areas with large reflectivity, which exceeds the maximum capturing capacity of camera sensors, resulting in the failure to obtain the accurate intensity, absolute phase and three-dimensional (3D) data. In this paper, a uniform blue image is projected to divide object surface into three areas with different reflectivity by using different intensity responses of RGB channels of color images. Crosstalk coefficient function is applied to obtain intensity of overexposed areas, and then the optimal exposure time of areas is calculated by the linear photometric response of the camera. Finally, three sets of blue fringe patterns with optimal exposure time are synthesized into the fused HDR images to calculate the absolute phase. Experimental results confirm that the proposed method can accurately measure HDR objects with large variation range of reflectivity.

Crosstalk characteristics of orbital angular momentum of focused perfect vortex beam in atmospheric turbulence

The perfect optical vortex beam (POV) is a special kind of vortex beam, whose radius is independent of its orbital angular momentum (OAM) mode, but the atmospheric turbulence (AT) causes crosstalk between different topological charges, which is a serious challenge in OAM-based communication system. We establish a theoretical model with a turbulence suppression effect for deriving the spiral spectrum of a focused perfect optical vortex beam (FPOV) after propagation through anisotropic AT. Through numerical analysis, we simulate the behavior of FPOV under different turbulence and beam parameters to better understand the effect of the received probability and its corresponding modal crosstalk under various conditions. In addition, the simulation of AT uses the multi-phase screen method to verify the theoretical results. The results show that the changes in topological charge, wavelength, receiving aperture, beam waist, and hollow radius all have an influence on the received probability. Also, some strategies for selecting turbulence parameters to reduce modal crosstalk in anisotropic AT are also discussed. The focus would reduce the effect of turbulent aberrations on the signal OAM mode received probability, and the FPOV provided better performance than the POV, which may be useful in OAM-based free space optical communication.

Natural products targeting signaling pathways associated with regulated cell death in gastric cancer: Recent advances and perspectives.

Gastric cancer (GC) is one of the most serious gastrointestinal malignancies with high morbidity and mortality. The complexity of GC process lies in the multi-phenotypic linkage regulation, in which regulatory cell death (RCD) is the core link, which largely dominates the fate of GC cells and becomes a key determinant of GC development and prognosis. In recent years, increasing evidence has been reported that natural products can prevent and inhibit the development of GC by regulating RCDs, showing great therapeutic potential. In order to further clarify its key regulatory characteristics, this review focused on specific expressions of RCDs, combined with a variety of signaling pathways and their crosstalk characteristics, sorted out the key targets and action rules of natural products targeting RCD. It is highlighted that a variety of core biological pathways and core targets are involved in the decision of GC cell fate, including the PI3K/Akt signaling pathway, MAPK-related signaling pathways, p53 signaling pathway, ER stress, Caspase-8, gasdermin D (GSDMD), and so on. Moreover, natural products target the crosstalk of different RCDs by modulating above signaling pathways. Taken together, these findings suggest that targeting various RCDs in GC with natural products is a promising strategy, providing a reference for further clarifying the molecular mechanism of natural products treating GC, which warrants further investigations in this area.

Experimental research of 13-core 5-LP mode fiber with high doped graded-index core and stairway-index trench.

A graded-index 13-core 5-LP mode fiber with high doped core and stairway-index trench structure have been successfully prepared by Hole-drilling method and Plasma vapor deposition. This fiber has 104 spatial channels, realizing large capacity information transmission. By building an experimental platform, the 13-core 5-LP mode fiber have been tested and characterized. The core can stably transmit 5 LP modes. The transmission loss is lower than 0.5 dB/km. Inter-core crosstalk (ICXT) of each layer of core is analyzed in detail. The ICXT can be less than -30 dB/100 km. The test results show that this fiber can stably transmit 5 LP modes, and has the characteristics of low loss and low crosstalk, realizing large capacity transmission. This fiber provides a solution to the issue of limited fiber capacity.

Design and Performance of 1×8 Core Selective Switch Supporting 15 Cores Per Port Using Bundle of Three 5-Core Fibers

A core-selective switch (CSS) is a key building block for a port modular spatial cross-connect where an optical signal launched into any core in the input multi-core fiber (MCF) can be switched to a core that has the same core identifier of any output MCF. One way to increase the core count in a CSS is to use several MCFs as a bundle and collimate/demultiplex beams emitted from it all at once using a single microlens. In this paper, we report a 1×8 CSS prototype based on a bundle of three 5-core fibers (5-CFs), which supports 15 cores per port, demonstrating the feasibility of a high core count CSS through MCF bundling. The CSS prototype exhibits insertion loss of less than 4.8 dB, and polarization dependent loss of less than 0.5 dB over an ultrawide wavelength range of 1480 nm to 1630 nm. The inter-core crosstalk (XT) characteristics as a function of the wavelength are thoroughly investigated. We show that the intra 5-CF XT imparted to the center core from the other four outer cores in the same 5-CF is less than −52 dB and the inter 5-CF XT from cores in the other 5-CFs in the same bundle is less than -64 dB, which are sufficiently low values for practical networks. No OSNR penalty in the 100-Gb/s spatial channel was observed when ten 100-Gb/s DP-QPSK WDM signals in the C-band were simultaneously routed by the bundled 5-CF 1×8 CSS prototype.

Low crosstalk and large effective mode field area heterogeneous 13-core 6-mode fiber with double high refractive index rings

We propose a heterogeneous thirteen-core few-mode fiber, which has the excellent characteristics of low crosstalk (XT), large effective mode field area (Aeff) and low dispersion slope (Dslope). The double high refractive index ring can precisely control the effective refractive index difference between the LP mode in the core and reduce intra-core XT. The relative spatial efficiency (RSE) of the 13-core 6-mode fiber reaches 33.84, and the number of spatial channels is as high as 130. The inter-core crosstalk is less than −60 dB/km at 1550 nm. The results show that the proposed fiber with low crosstalk and large Aeff is sufficient to satisfy the requirements of long-distance transmission in the future.

A novel mode-division (de)multiplexer with degenerate modes output for MIMO-FREE applications

In this study, we propose a novel three-dimensional architecture mode (de)multiplexer with degenerate modes output using a pure silica FMF ring core transmission channel, which solves the problem caused by random mode rotation and can be used in multiple-input multiple-output free (MIMO-FREE) applications such as data center application in the future. By using the pure silica FMF ring core transmission channel and larger effective refractive index difference, the performance with low loss, high extinction ratio (ER) and low crosstalk is achieved. The main channel with a few-mode fiber (FMF) ring-core structure supports the modes LP01, LP11, and LP21, and the large effective refractive index difference between each mode in the core ensures low crosstalk characteristics between the modes. Using the pure silica core channel can effectively reduce propagation attenuation and fusion loss. Our proposed MUX/DEMUX with degenerate modes output is achieved when the degenerate modes LP11a/LP11b and LP21a/LP21b are transmitted as two independent mode signals, which can be used in MIMO-FREE applications. The extinction ratios (ERs) of the degenerate modes LP11 and LP21 are kept above 31.66 dB and 24.43 dB, respectively, and the ER of mode LP01 is kept above 38.72 dB in the C band. The coupling efficiency of mode LP01 is approximately 0 dB, which is almost unchanged with the increase of the wavelength. The coupling efficiency of LP11 is higher than −3.49 dB and that of LP21 is higher than −7.24 dB in the whole C-band. At 1550 nm, the coupling efficiencies of modes LP01, LP11, and LP21 are −0.002 dB, −0.052 dB, and −0.178 dB, respectively. The coupling efficiency and ER of LP01 mode are the best, and those of the degenerate mode LP11 are always better than those of mode LP21. Our proposed MUX/DEMUX achieves low crosstalk and high ER performance and solves the problem caused by the degenerate modes rotations during transmission.

Multi-channel parallel ultrasound detection based on a photothermal tunable fiber optic sensor array.

A multi-channel parallel ultrasound detection system based on a photothermal tunable fiber optic sensor array is proposed. The resonant wavelength of the ultrasound sensor has a quadratic relationship with the power of a 980-nm heating laser. The maximum tuning range is larger than 15 nm. Through photothermal tuning, the inconsistent operating wavelengths of the Fabry-Perot (FP) sensor array can be solved, and then a multiplexing capacity of up to 53 can be theoretically realized, which could greatly reduce the time required for data acquisition. Then, a fixed wavelength laser with ultra-narrow linewidth is used to interrogate the sensor array. The interrogation system demonstrates a noise equivalent pressure (NEP) as low as 0.12 kPa, which is 5.5-times lower than the commercial hydrophone. Furthermore, a prototype of a four-channel ultrasound detection system is built to demonstrate the parallel detection capability. Compared with the independent detection, the SNR of parallel detection does not deteriorate, proving that the parallel detection system and the sensor array own very low cross talk characteristics. The parallel detection technique paves a way for real-time photoacoustic/ultrasound imaging.

Dual-channel metasurfaces for independent and simultaneous display in near-field and far-field.

The operation of near-field and far-field can be employed to display holographic and nanoprinting images, which significantly improves the information density. Previous studies have proposed some approaches to display the images independently or simultaneously, but cannot satisfy these two characteristics in a single structure under the same incident light. Here, a single layer multifunctional metasurface is proposed to display a nanoprinting image and a holographic image independently and simultaneously. By tailoring the dimensions of each nanobricks and adopting different orientation angle, the amplitude and phase can be artificially designed. Moreover, enabled by the simulated annealing algorithm, we take the impact of both amplitude and phase of each nanobrick into consideration, which eliminates the unnecessary influence of amplitude on holographic image. Compared with previous work, our metasurfaces markedly improve the quality of holographic image with simple structures while not affecting the nanoprinting image. To be exact, it breaks the coupling between the near-field and far-field, achieving independent and simultaneous control of both fields. Our proposed metasurfaces carry characteristics of simple manufacture, little crosstalk, and great compactness, which provides novel applications for image displays, optical storage and information technology.

Analysis and Calculation of Crosstalk for Twisted Communication Cables in Umbilical Cable

An umbilical cable is a compactly integrated cable consisting of electrical power cables, communication (electric signal) cables, and chemical transposition tubes. An umbilical cable is widely used in developing oil and gas resources of deep and ultra-deep water. With the increment of the length and the functional integration of umbilical cables, the crosstalk becomes a crucial issue in the cable design, and needs to be evaluated carefully before the fabrication and installation. Moreover, the twisted structure of communication cable cores has incurred extra difficulties to the crosstalk calculation. Nevertheless, it is not an easy task to model the complex twisted structure in existing models and methods of the crosstalk computation. In this regard, this paper proposes a numerical methodology for the crosstalk calculation considering the multi-conductor twisted structure of the cable cores. In the methodology, the four-wire twisted structure is modelled as a cascade of uniform multiconductor transmission line (MTL) sections, each wire section covering a length of 1/4 pitch, with abrupt interchanges of wire positions at the ends. The chain-parameter equation is introduced to describe the voltage and current transfer relationship in each MTL section. To obtain the numerical solutions of the twisted cable system, the port constraint equations and the permutation matrices are also required and developed. The per-unit-length parameters of the umbilical cable system are computed by numerical methods. The feasibility to engineering applications and accuracy of the proposed methodology is validated by experimental results, and the crosstalk characteristics of communication cables in a typical umbilical cable under different operating conditions are investigated.

Core Selective Switch With Low Insertion Loss Over Ultra-Wide Wavelength Range for Spatial Channel Networks

The core selective switch (CSS) is an optical spatial switch that has been recently proposed as a key building block to achieve a scalable and low-insertion-loss spatial cross-connects for use in future spatial channel networks. In this paper, we report on a novel CSS design employing a two dimensionally arranged microlens-based multicore fiber (MCF) collimator array and a micro-electromechanical systems (MEMS) mirror array. The former enables precise alignment between MCFs and collimator lenses, and the latter yields polarization-independent high reflection over a wide wavelength range and a large tilt angle. Based on the design, a compact (∼50 mm) five-core <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1 \times 8$</tex-math></inline-formula> CSS prototype is fabricated. We experimentally show that the CSS prototype exhibits low insertion loss (1.2∼2.7 dB), low polarization dependent loss (< 0.25 dB), and low crosstalk (< <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ - 30$</tex-math></inline-formula> dB) characteristics over an ultra-wide wavelength range from 1500 nm to 1630 nm. Bit-error-rate measurements using optical signals in the C-band, S-band, and L-band show that the CSS prototype incurs no optical signal-to-noise ratio penalty in spatial channel routing over an ultra-wide wavelength band.

Six‐Mode Orbital Angular Momentum Generator Enabled by Helicity‐Assisted Full‐Space Metasurface with Flexible Manipulation of Phase, Polarization, and Spatial Information

AbstractVortex beam carrying orbital angular momentum (OAM) has been experiencing a research upsurge attributed to its excellent communication capability, which also boosts the development of the OAM technology and promotes the application of the OAM generator. However, most of the existing designs of the OAM generators can only produce a small number of diverse OAM modes, and restrict the channel capacity of single OAM generator. Herein, an appealing strategy of six‐mode OAM generator based on helicity‐assisted full‐space metasurface is proposed to generate up to six diverse OAM modes by altering the polarization state, illumination region, and incidence direction of incident waves. Significantly, the designed OAM generator has high communication security because of its great information entropy, and the generated OAM modes possess the characteristics of high purity and low crosstalk which result from the orthogonal polarization states and unequal deflection angles of produced vortex beams. A proof‐of‐concept prototype is constructed to corroborate the validity of our methodology, and the results of simulations and experiments are in excellent agreement with theoretical predictions. This fire‐new OAM generator will possess a promising application prospect in communication systems, and may also provide an efficacious method to design multifunctional devices.

Analysis of time reversal cavity characteristics based on multipath channel model

The electromagnetic wave time reversal technology using time reversal cavity (TRC) has potential applications in many areas, such as pulse compression, power synthesis, perturbation detection, beamforming, etc. Microwave chaotic cavity with multi-path transmission characteristics is usually used in TRC. Based on diffraction theory, it can prove that this kind of cavity has spatiotemporal focusing characteristics and can be used for compressing pulses, but it cannot be used to analyze the reversal performance of the cavity. In order to obtain a suitable analysis method and guide the design of TRC, in this work, the scattering, diffusion and attenuation characteristics of electromagnetic wave propagation are analyzed and a multipath channel model of TRC is built by the channel theory. Moreover, the crosstalk characteristics between paths are studied, and the generation mechanism of time sidelobe, time sidelobe shift and interference are also investigated. In addition, under the assumption of random plane wave, the distribution characteristics of spatial focal spot are analyzed, which is consistent with the diffraction theory. Moreover, the actual focal spot size is not only limited by the diffraction limit, but also related to the initial focal spot size. The theoretical analysis results are basically consistent with the experimental and numerical simulation results.

Design of ring-core few-mode multi-core fiber with low crosstalk and low bending loss

Aiming at solving the problems of coupling between modes in a core and mode coupling between cores in few-mode multi-core fiber, a fiber with seven cores each with step index is proposed, and each core can support five modes. Each core has a central low refractive index region and a high refractive index ring to ensure that there is a large refractive index difference between modes in the core, so as to reduce the problem of mode coupling. The bending loss of central core and outer core, the crosstalk characteristics between modes and the influence of core parameters on crosstalk performance are simulated and analyzed by the finite element method. The simulation results show that at a wavelength of 1.55 μm and a bending radius of 50 mm, the bending loss of the proposed multi-core fiber is much lower than its attenuation loss, and the crosstalk between the adjacent cores of the five core modes are less than –20 dB/100 km. Therefore, this multi-core fiber can realize independent transmission of the core modes with long-distance under small bending radius.

Distribution Characteristics of Inter-Core Crosstalk in Weakly Coupled Multicore Fibers

Distribution Characteristics of Inter-Core Crosstalk in Weakly Coupled Multicore Fibers

Crosstalk prediction and statistical properties of transmission line

In this paper, for the crosstalk error problem of multi-core stranded wires caused by non-uniform pitch, the Monte Carlo method is used to establish the probability distribution model of non-uniform pitch of stranded wires. For stranded wire crosstalk prediction, a transmission line pa-rameter prediction model is constructed using the BSO-BP neural network algorithm, and the effec-tiveness of the algorithm in this paper is verified by simulation. The final calculation gives the statis-tical characteristics of crosstalk on multicore stranded wires.