Low Crosstalk Research Articles

Ultra-sensitive pressure sensor with low-temperature crosstalk based on the Vernier effect and helical structure

What we believe to be a novel high-sensitivity fiber-optic pressure sensor based on the vernier effect and helical structure is proposed and experimentally verified. The sensor utilizes the superposition of higher-order mode Mach-Zehnder interference and Sagnac fundamental mode polarization interference in a single fiber ring to achieve the vernier effect. In addition, a non-invasive encapsulation structure was fabricated to convert the rise and fall of the pressure value into the change in the twist angle of the optical fiber. This approach reduces the interference of the detecting medium on the sensor signal while simultaneously increasing the sensitivity of the pressure sensor. According to experimental data, the detection sensitivity of the sensor can reach −67277 nm/MPa, which is 65 times higher than the sensitivity of the conventional vernier effect pressure sensor. It also solves the issue of temperature interference with the Vernier-effect structured fiber optic sensor. The sensor has a measured temperature cross-sensitivity of 0.000065 kPa/°C, which is significantly lower than that of comparable sensors. This makes the sensor highly sensitive and ideal for low crosstalk pressure measurement.

A low crosstalk seven-core five-mode fiber for high density transmission and large capacity communication

We propose a seven-core five-mode fiber with air hole-assisted and high refractive index ring structure, and it can be fabricated by the stack-and-draw technique. The air hole auxiliary structure can significantly restrain the energy coupling between cores, and the high refractive index ring structure can meet the requirements of low intra-core crosstalk (XT) by improving the effective refractive index difference (Δn eff ) between adjacent modes. Through analyzing the influence of the number and arrangement of air holes on inter-core XT and effective mode field area (A eff ), it can be achieved the results that the inter-core XT is less than −44 dB/100 km and all the A eff values of LP modes are greater than 100 μm2 in the seven-core five-mode fiber when the wavelength is 1550 nm and the bending radius (R) is 80 mm. At the same time, the Δn eff between LP21 and LP02 mode can be controlled to 1.3 × 10−3 by adjusting the parameters of the high refractive index ring. In addition, the relative core multiplexing factor (RCMF) of the seven-core five-mode fiber is as high as 88.34. The simulation results show that the seven-core five-mode fiber has high spatial density and is suitable for the communication system with multi-channel and long-distance transmission.

Compact and broadband silicon polarization splitter-rotator using adiabaticity engineering.

We propose and demonstrate a short and broadband silicon mode-conversion polarization splitter-rotator (PSR) consisting of a mode-conversion taper and an adiabatic coupler-based mode sorter both optimized by adiabaticity engineering (AE). AE is used to optimize the distribution of adiabaticity parameter over the length of the PSR, providing shortcut to adiabaticity at a shorter device length. The total length of the PSR is 85 µm. The design is compatible with standard silicon photonics platforms and requires only one patterning step. Fabricated PSR has a polarization cross talk of less than -20 dB over the entire O-band for the TE polarization and a polarization cross talk of less than -15 dB from 1267 to 1348 nm for the TM polarization. Overall, the PSR shows low polarization cross talk (-15 dB) over a bandwidth of 81 nm in the O-band. Cross-wafer measurements show that the PSR has good fabrication tolerance.

36‐5: Research on The Structure of Low Color Crosstalk Grillless Optical Cavity Based on Partition Toning Technique

36‐5: Research on The Structure of Low Color Crosstalk Grillless Optical Cavity Based on Partition Toning Technique

Wavelength-polarization-multiplexed multichannel perfect vortex array generator based on dielectric metasurface

The multi-channel perfect vortex (PV) array based on metasurface has important applications in optical communication, particle manipulation, quantum optics, and other fields due to its ultra-thin structure and excellent wavefront control ability. However, it is very challenging to utilize a single metasurface to simultaneously achieve independent channel PV arrays at different wavelengths with low crosstalk and low structural complexity. Here, we propose and design a single rectangular structured metasurface based on TiO2, achieving a multi-channel PV beam array with dual-wavelength and dual-polarization multiplexing. Simulation and experimental results show that when two orthogonal linearly polarized beams with wavelengths of 532 nm and 633 nm are incident on the metasurface, clear PV arrays with corresponding topological charge arrangements can be obtained in different diffraction regions of the same observation plane. The metasurface proposed in this article can enhance the channel capacity of a PV beam array through wavelength-polarization-multiplexing, thus having important application potential in spatial information transmission, high-dimensional information storage, and secure information encryption.

Conditional-not Displacement: Fast Multioscillator Control with a Single Qubit

Bosonic encoding is an approach for quantum information processing, promising lower hardware overhead by encoding in the many levels of a harmonic-oscillator mode. Scaling to multiple modes requires weak interaction for independent control, yet strong interaction for fast control. Applying fast and efficient universal control on multiple modes remains an open problem. Surprisingly, we find that displacements conditioned on the state of a single-qubit ancilla coupled to multiple harmonic oscillators are sufficient for universal control. We present the conditional- operation concept, which can be used to reduce the duration of entangling gates. Within this guiding concept, we develop the conditional- displacement control method which enables fast generation and control of bosonic states in multimode systems weakly coupled to a single-ancilla qubit. Our method is fast despite the weak ancilla coupling. The weak coupling in turn allows for excellent separability and thus independent control. We demonstrate our control on a superconducting transmon qubit weakly coupled to a multimode superconducting cavity. We create both entangled and separable cat states in different modes of the multimode cavity, showing entangling operations at low crosstalk while maintaining independent control of the different modes. We show that the operation time is not limited by the inverse of the coupling rate, which is the typical timescale, and we exceed it by almost 2 orders of magnitude. We verify our results with an efficient method for measurement of the multimode characteristic function which employs our conditional- displacement. Our results inspire a new approach toward general entangling operations and allow for fast and efficient multimode bosonic encoding and measurement. Published by the American Physical Society 2024

Combined frequency domain near-infrared spectroscopy and diffuse correlation spectroscopy system for comprehensive metabolic monitoring of inspiratory muscles during loading.

Mechanical ventilation (MV) is a cornerstone technology in the intensive care unit as it assists with the delivery of oxygen in critically ill patients. The process of weaning patients from MV can be long and arduous and can lead to serious complications for many patients. Despite the known importance of inspiratory muscle function in the success of weaning, current clinical standards do not include direct monitoring of these muscles. The goal of this project was to develop and validate a combined frequency domain near-infrared spectroscopy (FD-NIRS) and diffuse correlation spectroscopy (DCS) system for the noninvasive characterization of inspiratory muscle response to a load. The system was fabricated by combining a custom digital FD-NIRS and DCS system. It was validated via liquid phantom titrations and a healthy volunteer study. The sternocleidomastoid (SCM), an accessory muscle of inspiration, was monitored during a short loading period in fourteen young, healthy volunteers. Volunteers performed two different respiratory exercises, a moderate load and a high load, which consisted of a one-minute baseline, a one-minute load, and a six-minute recovery period. The system has low crosstalk between absorption, reduced scattering, and flow when tested in a set of liquid titrations. Faster dynamics were observed for changes in blood flow index (), and metabolic rate of oxygen () compared with hemoglobin + myoglobin (Hb+Mb) based parameters after the onset of loads in males. Additionally, larger percent changes in , and were observed compared with Hb+Mb parameters in both males and females. There were also sex differences in baseline values of oxygenated Hb+Mb, total Hb+Mb, and tissue saturation. The dynamic characteristics of Hb+Mb concentration and blood flow were distinct during loading of the SCM, suggesting that the combination of FD-NIRS and DCS may provide a more complete picture of inspiratory muscle dynamics.

High sensitivity I-beam shaped polarization related vector curvature sensor with optical intensity modulation

This paper presents an innovative I-beam optical sensor combining Panda-type polarization-maintaining fiber (PMF) and thin-width polarization-maintaining photonic crystal fiber (PM-PCF), crafted using precision machining techniques like tapering and axially offset splicing. The study explores the impact of structural parameters on the device's optical performance using polarization mode coupling theory and assesses its effectiveness in vector curvature sensing, focusing on intensity sensitivity. A novel dual-parameter differential demodulation technique is proposed, achieving accurate bending angle measurements (error < 2°) through wavelength and intensity-curvature sensitivities. The experimental results highlight the device's impressive maximum intensity-curvature response of 9.36 dB/m−1. With notable responsiveness, low cross-talk, and robust polarization stability, this device holds substantial promise in the realms of fiber lasers and optical communications, serving as an ideal polarization-based, mechanically tunable optical device. Furthermore, it introduces innovative concepts and offers technological support for precision instrument measurements and related fields.

Low thermal crosstalk silicon MZI optical switch with high speed and low power consumption

Abstract We developed a compact thermo-optic Mach–Zehnder interferometer switch with a direct heating heater using multimode interference and achieved a sufficiently low thermal crosstalk performance. Large-scale switch systems, such as optical neural networks, require thermo-optical switches with low power consumption, fast switching speed, compact size, and low thermal crosstalk. This switch is equipped with a heater that directly heats the Si core waveguide, which is a structure that connects non-doped Si wires between phase shifters and a heatsink. As a result, a significant miniaturization with a phase shifter length of approximately 7 μm, low π-phase shift power consumption of less than 20 mW, and fast switching in sub-microseconds were achieved. The improved phase shifter showed a very small figure of merit of 8.89 mW∙μs. Simultaneously, transmission spectrum measurements of nearby ring resonators show that the thermal crosstalk is significantly reduced even at a distance of only 30 μm. This device can contribute to the overall circuit performance and footprint reduction in large-scale optical integrated circuits and optical neural network configurations.

Cellulose/Single‐Walled Carbon Nanotube‐Based Pressure‐Sensing Thin Film Transistor with Channel Conductivity Modulation

Field‐effect transistor (FET)‐type pressure sensor offers excellent amplification and signal conversion functionality as a switching device, and it has the capability to integrate tactile sensors by constructing active‐matrix arrays with low crosstalk. However, conventional FET‐type pressure sensors either have a complex device layout with additional components, such as pressure‐sensitive elastomer, attached to the source/drain electrodes, or the method of modulating the gate dielectric can lead to dielectric breakdown and device failure. Additionally, the deformation of the elastomer limits response speed and causes differences in early and late response characteristics. In this article, a facile structure pressure‐sensing thin film transistor (TFT) that modulates the channel conductivity by cellulose/single‐wall carbon nanotube (SWCNT) composite is reported, ensuring a simple layout without damaging the device. The fabricated cellulose/SWCNT‐based pressure‐sensing TFT exhibits a change in the on/off current ratio from 2.75 × 103 to 2.0 × 104 in response to pressure with high linearity (R2 = 0.9935) and maintains durable performance over 2000 loading‐unloading cycles. Additionally, the sensor shows a fast response time of less than 8 ms. A practical concept of sensing circuits is demonstrated based on pressure‐sensing TFTs for integration into display driving circuits, enabling accurate pressure sensing using only the signal to drive the display.

Chromatic correction for super multi-view 3D display based on diffraction theory.

The traditional analysis method for super multi-view 3D display based on geometric optics, which approximates the lenticular lenses as a series of pinhole structures, ignored the chromatic aberration. In this paper, the optimization method based on diffraction theory is proposed for super multi-view 3D display, where the wavefronts are evaluated accurately by the forward propagation method, and the chromatic aberration of the synthetic viewpoint image is reduced dramatically by the backward reconstruction optimization method (BROM). The optical experiment is performed to verify the feasibility of the method, which is consistent with numerical simulation results. It is proved that the proposed method simulates the physical propagation process of super multi-view 3D display and improves the reconstructed image quality. In the future, it can be used to achieve the super multi-view 3D light field technology with low crosstalk.

High sensitivity and low temperature cross-talk magnetic field sensor with ferrofluid-filled in-fiber Mach-Zehnder interferometer

A ferrofluid-filled in-fiber Mach-Zehnder interferometer (MZI) is presented and validated for magnetic field sensing. It is constructed by embedding a short capillary tube filled with ferrofluid which is sandwiched between two SMFs through a short MMF at its both ends, and the device is experimentally proved having extreme high refractive index (RI) sensitivity. When the sensor is placed in an external magnetic field, the RI of the ferrofluid changes, causing a shift in the transmission spectrum of the interferometer. Experimental results show that the proposed sensor exhibits a high sensitivity of 8.9657 nm/mT and 4.2642 nm/mT for longitudinal and vertical magnetic field within the range of 0–1.5 mT and 0.8–2.2 mT, respectively. Furthermore, the sensor exhibits excellent low temperature cross-talk in longitudinal and transverse magnetic fields as low as 0.014 mT/°C and 0.030 mT/°C, respectively. The sensor offers advantages such as stable operation, compact size, and robust mechanical structure.

Design of low crosstalk homogeneous multicore few mode fiber for future high-capacity optical transmission

Many researches are diligently striving to develop a multi-core optical fiber with minimal signal distortion and reduced issues. The current study proposed few designs for homogeneous multicore few mode fiber which is characterized by the combination of high index ring and trench. This study also added four air holes surrounding each core. We considered pure silica for both the outer clad and the inner clad of the fiber. To calculate the crosstalk, a two-core model was used and the mode coupling coefficient was determined using coupled-mode and couple-power theory. For the current work we considered only the fundamental mode (LP01) to compute the crosstalk between neighboring cores. The proposed structure was simulated using the wave optics module of COMSOL Multiphysics (Version 6.1), a well-known commercial software tool based on finite element method (FEM). MATLAB (Version R2018a) was used to calculate the mode coupling coefficient and crosstalk after extracting the mode field data from COMSOL. Obtained results revealed that the proposed structure can offer lower crosstalk which was attractive for future high-capacity fiber optic communication using multicore fiber technology.

Inverse design of a silicon-based ultra-compact four-channel mode splitter with dual polarizations

We adopt the inverse-designed method and demonstrate an ultra-compact four-channel mode splitter with dual polarizations, which enables mode division multiplexing and polarization division multiplexing simultaneously without changing the mode orders and suitable for fabrication and integration based on silicon-on-insulator platform. The four TE0, TM0, TE1 and TM1 modes at the central wavelength of 1550 nm can be efficiently split with low insertion loss (<1.9 dB), low channel crosstalk (<−17 dB), low reflection loss (<−18 dB). Moreover, the proposed mode splitter has the potential of incorporating the wavelength division multiplexing for mass data transmission and high computing parallelism.

Crosstalk reduction for Arrayed waveguide gratings on Silicon-on-Insulator platform

Ultracompact silicon-based arrayed waveguide gratings (AWGs) with low loss and low crosstalk are essential for on-chip optical interconnect and miniaturized spectroscopic analysis systems. In our previous research, we demonstrated the crosstalk reduction by utilizing constant projection period for phased array waveguide on the tangent line to the grating pole to reduce the imaging error induced by phased array waveguide end point positions [1] and using deep etching waveguides at the interface of free propagation region to further decrease the footprint of phase region of an AWG to reduce fabrication imperfections induced phase error [2]. Here we first study the effect of curved waveguides in the phased array of 16 × 400 GHz AWGs on the adjacent crosstalk of output channels. According to the AWGs made in our fabrication platform and the testing results of five dies from one wafer at different locations, the AWGs with equal length of single-mode curved waveguides have an average adjacent crosstalk level of ∼ 4 dB smaller than those with equal length of narrow single-mode waveguides composed of straight and curved waveguides in their phased array. Based on the design of equal curved waveguide length in phased array, in combination with our reported approaches on crosstalk reduction, 16 × 200 GHz, 8 × 800 GHz and 8 × 1250 GHz AWGs are fabricated. For characterization, five dies including all designs from different locations of the fabricated wafer are tested. Experimental results show that among these five dies, the best adjacent crosstalk levels are less than − 21.97 dB, −25.72 dB, −24.83 dB and the worst adjacent crosstalk levels are less than − 20.51 dB, −25.03 dB, −24.34 dB for 16 × 200 GHz, 8 × 800 GHz and 8 × 1250 GHz AWGs with FPR angle of 120°, respectively, within the passband width of 25 % channel spacing. The on-chip insertion losses for all output channels of these fabricated AWGs are less than 3 dB.

Asymmetric dual-core liquid crystal channel-based tunable mode converter

In this work, a higher order-to-fundamental mode converter is reported and analyzed based on an asymmetric dual channel waveguide (ADC-WG) on silicon. In the reported structure, one of the two waveguides is infiltrated with nematic liquid crystal (NLC) material to add temperature tunability while the other one is a solid BK7 waveguide. The modal characteristics are obtained using the full vectorial finite difference method (FVFDM). In addition, the structural parameters and optical characteristics of the employed materials are investigated to achieve good wavelength selectivity with a short device length (LD). Thus, a compact mode converter that can work at different wavelengths including the telecommunication wavelength i.e., 1.55 μm with LD ~ 482.31 μm and a low crosstalk of − 19.86 dB is presented. To prove the thermal tunability of the suggested mode converter, its operation is tested through a temperature range between 20 and 35 °C and the results show that the mode conversion process is achieved at each temperature with different phase matching wavelengths (λPMW) but with quite similar coupling length (LC). The proposed device can therefore be effectively utilized in integrated photonic circuits.

Multiplicative-noise-multiplexing holography with ultrahigh capacity and low cross talk.

Optical multiplexing technologies, by utilizing various dimensions of light, can effectively expand the information capacity and density for holography but may also lead to multiplexing cross talk. Here, we propose and demonstrate a novel, to our knowledge, multiplicative-noise-multiplexing holography by utilizing the orthogonality between multiplicative noises as a multiplexing dimension. The results prove that this holography can provide a new multiplexing dimension, significantly enhancing information capacity and effectively lowering cross talk. This promising scheme for ultrahigh-capacity holography has the potential to address the limitations of traditional holographic multiplexing technologies.

Test Method of Splice Points for Constructing Uncoupled Multi-Core Fiber Transmission Line With Low Inter-Core Crosstalk

Test Method of Splice Points for Constructing Uncoupled Multi-Core Fiber Transmission Line With Low Inter-Core Crosstalk

Low crosstalk six-core five-mode fiber with high refractive index rings and air trench

A novel six-core five-mode fiber composed of an air trench and high refractive index ring is proposed in this paper. Numerical analysis shows that the fiber can stably transmit five LP modes in the C + L band. The effective refractive index difference of the five LP modes at 1.55 μm is more significant than 1.4 × 10-3, which is conducive to the independent transmission of the modes. The inter-core crosstalk of the fiber is less than -95 (dB / 100km). Therefore, the fiber can be well used to build a large-capacity optical fiber transmission system.

Ultra-compact and high-performance four-channel coarse wavelength-division (de)multiplexing filters based on cascaded Mach-Zehnder interferometers with Bezier-shape directional couplers

Using cascaded Mach-Zehnder interferometers (CMZIs) provides an attractive option for realizing coarse wavelength-division (de)multiplexing (CWDM) filters with low losses, low crosstalk, flat tops, and high scalability. However, they usually have large footprints and insufficient fabrication tolerances, due to the inferior performance of conventional directional couplers (DCs) used for MZIs. Here, a four-channel CMZI wavelength-division (de)multiplexer based on novel Bezier-shape DCs with compact footprints, broad bandwidths and decent fabrication tolerances. For the fabricated (de)multiplexer with 20-nm channel spacing, the excess loss is less than 0.5 dB and the crosstalk is lower than −19.5 dB in the 1-dB bandwidth of 12.8 nm. For the case with a core-width deviation of ±20 nm, the device still performs very well with low losses and low crosstalk. Compared to the state-of-the-art MZI-based CWDM filters, the present device has slightly high performances and a footprint of 0.012 mm2 shrunk greatly by ∼3-folds. This work can be extended for more channels and other material platforms.