Single-mode Input Research Articles

Effectiveness Analysis of Entrepreneurial Legal Risk Prevention Based on Multi-Modal Deep Learning Model

With the emergence of the upsurge of entrepreneurship, entrepreneurs are increasingly concerned about legal risks. In the process of entrepreneurship, legal risk is the biggest hidden danger of entrepreneurial enterprises. The prevention and avoidance of legal risks is a long and arduous process, and not all risks can be identified and avoided in time. The deep learning method has brought great changes to the fields of speech recognition, image recognition and natural language processing. The tasks in these fields only involve single-mode input, but more recent applications need to involve multi-mode intelligence. Multimodal deep learning mainly includes three aspects: multimodal learning representation, multimodal signal fusion and multimodal application. Through the research on the legal risks in recent years, this paper believed that there are many legal problems in the development of entrepreneurial enterprises, including contract disputes, trade secret disputes, trademark infringement disputes, copyright infringement disputes, and so on. This paper aimed to study the problem of Legal Risks of Entrepreneurship (LRE) that entrepreneurs are concerned about, and proposed a new solution from the perspective of image recognition technology. 486 entrepreneurs were investigated by questionnaire. In the process of entrepreneurship, 87.04% of entrepreneurs encountered legal risks, and they would turn to lawyers for help, which is a better way. However, in most cases, entrepreneurs are exposed to LRE because of their insufficient understanding of economic law, so they solve it through lawyers. However, if a lawyer is hired, the cost would be very high, which would bring great economic pressure to the enterprise. Only 17.90% of entrepreneurs would safeguard their legitimate rights and interests through their own knowledge and legal weapons without resorting to lawyers. It can be seen that entrepreneurs have relatively low practical ability in the use of LRE, and their legal practical ability is obviously insufficient.

Free-standing microscale photonic lantern spatial mode (De-)multiplexer fabricated using 3D nanoprinting

Photonic lantern (PL) spatial multiplexers show great promise for a range of applications, such as future high-capacity mode division multiplexing (MDM) optical communication networks and free-space optical communication. They enable efficient conversion between multiple single-mode (SM) sources and a multimode (MM) waveguide of the same dimension. PL multiplexers operate by facilitating adiabatic transitions between the SM arrayed space and the single MM space. However, current fabrication methods are forcing the size of these devices to multi-millimeters, making integration with micro-scale photonic systems quite challenging. The advent of 3D micro and nano printing techniques enables the fabrication of freestanding photonic structures with a high refractive index contrast (photopolymer-air). In this work we present the design, fabrication, and characterization of a 6-mode mixing, 375 µm long PL that enables the conversion between six single-mode inputs and a single six-mode waveguide. The PL was designed using a genetic algorithm based inverse design approach and fabricated directly on a 7-core fiber using a commercial two-photon polymerization-based 3D printer and a photopolymer. Although the waveguides exhibit high index contrast, low insertion loss (−2.6 dB), polarization dependent (−0.2 dB) and mode dependent loss (−4.4 dB) were measured.

Vibration-based prediction of residual fatigue life for composite laminates through frequency measurements

Fiber reinforced polymer (FRP) structures may experience cumulative fatigue damage during their service life which can lead to structural failure. This paper focuses on predicting the residual fatigue life of FRP structures using vibration parameters. The relationship between residual fatigue life and natural frequencies is examined through modal testing and fatigue measurements on FRP beam specimens. Two prediction methods; semi-empirical models and machine learning (ML) algorithms, are utilized. The semi-empirical models are derived from existing “residual stiffness” models based on the relationship between bending stiffness and flexural frequencies. ML algorithms Support Vector Machine (SVM) and Artificial Neural Network (ANN), are developed for fatigue life prediction. Experimental validation is performed using measured frequencies during fatigue testing of FRP beams. The ML algorithms can use multimode frequencies unlike single mode of semi-empirical models. The verification results show that the ML algorithms can be used to predict the residual fatigue life with the selection of the appropriate mode of frequency. The results show that ML algorithms outperform single-mode frequency inputs, and the use of higher modes of measured frequencies improves the precision of fatigue life prediction. An inverse algorithm based on SVM exhibits higher prediction accuracy and stability, even with limited training samples.

Confirmation of Dissipative Sensing Enhancement in a Microresonator Using Multimode Input

Optical microresonators have proven to be especially useful for sensing applications. In most cases, the sensing mechanism is dispersive, where the resonance frequency of a mode shifts in response to a change in the ambient index of refraction. It is also possible to conduct dissipative sensing, in which absorption by an analyte causes measurable changes in the mode linewidth and in the throughput dip depth. If the mode is overcoupled, the dip depth response can be more sensitive than the linewidth response, but overcoupling is not always easy to achieve. We have recently shown theoretically that using multimode input to the microresonator can enhance the dip-depth sensitivity by a factor of several thousand relative to that of single-mode input and by a factor of nearly 100 compared to the linewidth sensitivity. Here, we experimentally confirm these enhancements using an absorbing dye dissolved in methanol inside a hollow bottle resonator. We review the theory, describe the setup and procedure, detail the fabrication and characterization of an asymmetrically tapered fiber to produce multimode input, and present sensing enhancement results that agree with all the predictions of the theory.

Silicon-based compact eight-channel wavelength and mode division (de)multiplexer for on-chip optical interconnects.

A compact wavelength and mode division (de)multiplexer is proposed for multiplexing a total of eight guided TE modes of a 220nm thick silicon-on-insulator waveguide with input channels at two wavelengths of 1.55 and 2µm for wavelength division multiplexing. The (de)multiplexer is composed of four sequentially arranged sections with bus waveguides of increasing widths. The first section uses an asymmetric directional coupler to couple one TE mode at 1.55µm, while each of the next three sections consists of two collocated directional couplers to simultaneously couple two TE modes of the bus waveguide, one at each wavelength of 1.55 and 2µm. Three linear adiabatic tapers are designed to connect the consecutive bus waveguides. The fundamental TE mode of the bus waveguide at 1.55 or 2µm is coupled by using another adiabatic taper from a single-mode input waveguide. The simulation results show that over a broad bandwidth of >100n m the insertion loss and crosstalk for both wavelength bands is <1.15d B and <-27d B, respectively. In addition, a compact device footprint with a total coupling length of ∼61µm is achieved due to the use of collocated directional couplers in three sections.

Sub-shot-noise-limited phase estimation via single-mode inputs.

In 1981, Caves pointed out that the phase sensitivity of a Mach-Zehnder interferometer with single-mode inputs is bounded by the shot-noise limit. The quantum Fisher information analysis shows that this statement holds true for the scenario where two antisymmetric phase shifts occur in two arms, but it is invalid for the scenario where an unknown phase is embedded in one of two arms. In this paper, we focus on the phase sensitivity directed against the latter scenario. The optimal single-mode input is discussed by analyzing common states, including displaced squeezed states, displaced number states, squeezed number states, Schrödinger cat states and completely mixed states. We find that the best choice is a squeezed vacuum state and show the specific measurement scheme which is capable of saturating the corresponding phase sensitivity limit. In addition, we study the effects of several realistic factors-anti-squeezing noise, photon loss and dark counts-on the phase sensitivity. Our results suggest that sub-shot-noise-limited phase sensitivity is attainable with low noise or loss, which paves the way for practical metrology.

Modeling of the thermal-lens induced mode coupling in fiber amplifiers

In this paper, a novel model for describing the thermal-lens induced mode coupling (TLMC) effect in the high power fiber amplifier is proposed firstly, to the best of our knowledge. Based on the rate equation and couple-mode equation, the model is built with both consideration of the thermal-lens induced mode field variation and the gain effect. With this model, the mode coupling behaviors with various pump schemes are numerically investigated and the impact of the TLMC is quantitatively discussed in a finite-length single-frequency fiber amplifier for paradigm. It is found that the higher-order mode (HOM) can be induced by the TLMC even with pure single-mode input signal and this effect is most severe with the co-pumped scheme while weakest with the counter-pumped scheme. It is also revealed that the TLMC will enhance the average HOM content and will keep predominant until the incident HOM is larger than a certain content. Such an enhancement of HOM content can play an important role as the seed triggering the transverse mode instability (TMI) and the pertinent study is helpful on investigating the relationship between the thermal-lens effect and the TMI.

Photonic Lanterns, 3-D Waveguides, Multiplane Light Conversion, and Other Components That Enable Space-Division Multiplexing

Four-mode multiplexing and manipulation technologies are reviewed in the context of space-division multiplexing (SDM) optical communication systems. These are multiplane light conversion (MPLC), fused fiber devices, such as photonic lanterns and tapered fiber bundles, 3-D waveguides fabricated using ultrafast laser inscription, and free-space imaging systems. Each device has its unique strengths and use cases. MPLC can create very complex transformations between two arbitrary sets of spatial modes and leverages mature gray-scale lithographic techniques. Photonic lanterns and tapered fiber bundles are all-fiber devices that can convert beams on single-mode fiber inputs into spatial modes. The all-fiber construction leads to very low losses and high-power handling. 3-D waveguides are inscribed into a glass block using ultrashort lasers and can arbitrarily route light in 3-D. Finally, free-space systems using lenses can also relay many multicore and multimode beams through a single free-space device, such as a thin film filter or an optical isolator. These four technologies have enabled hero transmission experiments in the multimode, multicore, and multimode fiber.

Single-Mode Input Fiber Combined with Multimode Sensing Fiber Used in Brillouin Optical Time-Domain Reflectometry

Conventional single-mode fiber (SMF) Brillouin optical time-domain reflectometry (BOTDR) suffers from a low signal-to-noise ratio (SNR) and severe sensing reliability due to the influence of the stimulated Brillouin scattering threshold and bend loss. In this study, a simple and low-cost distributed sensing structure, with a single-mode input fiber alignment fusion and a 50 μm diameter graded index multimode sensing fiber, is designed, and the SNR characteristic is investigated. Through theoretical derivation and experimental verification, a higher SNR and excellent bending resistance are realized in BOTDR. The experimentally measured improvements in the SNR of the proposed sensing structure over the SMF at the beginning and end of a 5 km fiber are 2.5 dB and 1.3 dB, respectively. The minimum bending radius of the sensing structure is 2.25 mm, which is much better than that of the SMFs. The bidirectional optical losses between the SMF and the 50 μm graded index multimode fiber are measured by a simple experiment system and are 0.106 dB and 1.35 dB, respectively. The temperature-sensing characteristics of the sensing structure are measured by the self-built frequency-shift local heterodyne BOTDR sensor, and the measured temperature sensitivity and accuracy are 0.946 MHz/℃ and 1 ℃, respectively. The design provides a reference for BOTDR with a high SNR and has great potential for structural safety and health monitoring of infrastructures.

Adjoint-optimized metasurfaces for compact mode-division multiplexing.

Optical fiber communications rely on multiplexing techniques that encode information onto various degrees of freedom of light to increase the transmission capacity of a fiber. However, the rising demand for larger data capacity is driving the need for a multiplexer for the spatial dimension of light. We introduce a mode-division multiplexer and demultiplexer design based on a metasurface cavity. This device performs, on a single surface, mode conversion and coupling to fibers without any additional optics. Converted modes have high fidelity due to the repeated interaction of light with the metasurface’s phase profile that was optimized using an inverse design technique known as adjoint analysis. We experimentally demonstrate a compact and highly integrated metasurface-based mode multiplexer that takes three single-mode fiber inputs and converts them into the first three linearly polarized spatial modes of a few-mode fiber with fidelities of up to 72% in the C-band (1530–1565 nm).

A bend-tolerant BOTDR distributed fiber sensor

A standard single mode input fiber combined with a graded index multimode sensing fiber (GI-MMF) with large numerical aperture is used as a distributed sensing fiber to realize bend-tolerant and low-cost structural safety and health monitoring of large infrastructures. In the designed distributed sensing fiber, the single mode fiber at the near end of the GI-MMF is used to excite the fundamental mode as much as possible in the GI-MMF to achieve good bending resistance, and filter out the high-order modes in the backscattering signal that may degrade the bending resistance and deteriorate the sensing performance, so as to realize the bend-tolerant distributed sensing. The principle of bend loss is analyzed, and the bending resistance of different sensing structures are discussed on the basis of theoretical and experimental comparisons. By measuring the Brillouin frequency shift and scattering spectrum width of the sensors, a stable and reliable optical coupling method is determined for the single mode fiber and GI-MMF combination, and a frequency-shifted local heterodyne Brillouin optical time domain reflectometry system is constructed for temperature measurements to evaluate the bending resistance of the sensors. The experimental results show that the sensor with the single mode fiber alignment fusion to a 5 km long and 62.5 μm diameter GI-MMF has the best bending resistance, and the achieved minimum bend radius, temperature coefficient and measurement accuracy are 1.75 mm, 0.933 MHz/°C and 1.4 °C, respectively, which indicates that the proposed sensing structure is capable of realizing bend-tolerant sensing and has huge potential in the field of high-accuracy structural safety and health monitoring of large infrastructures.

Multimodal Learning for Temporally Coherent Talking Face Generation With Articulator Synergy

Talking face generation is a demanding task to synthesize a high quality video with accurate lip synchronization and rhythmic head motion. Any subtle artifacts could be sensitively captured by humans and lead to poor visual quality. Existing methods tend to employ a conditional generation solution, which introduces facial landmarks to bridge the input information and output videos. However, these methods always suffer from unrealistic facial animations, because 1) they only take single-mode input, but ignore the complementarity of multimodal inputs for lip-sync improvement; 2) they only explore lip movements, but ignore the articulator synergy between lips and jaw; 3) they generate each video frame in a temporal-independent way, but ignore the temporal continuity among the entire video. To address these limitations, in this paper, we present a novel method to generate realistic and temporally coherent talking heads by considering multimodal inputs, articulator synergy, inter-frame consistency and intra-frame consistency. Firstly, for landmark prediction, a novel Multiple Synergy Network (MSN) is proposed to improve the accuracy of landmark prediction by incorporating multimodal inputs (i.e., audio and text inputs). Besides, instead of merely considering lip landmarks, we also explore the jaw movements to ensure articulator synergy among lips and jaw. Secondly, for realistic video generation, a Video Consistency Network (VCN) is proposed conditioned on the predicted landmarks. In VCN, the optical flow is adopted to model the temporal continuity between frames to ensure inter-frame consistency. Meanwhile, a mouth generation branch is proposed to enhance mouth texture and the corresponding mouth mask is employed to ensure intra-frame consistency between the mouth area and the others. Extensive experiments demonstrate that our approach exhibits excellent superiority on lip-sync and can generate photo-realistic facial animations. Project is available at http://imcc.ustc.edu.cn/project/tfgen/.

High fringe visibility fiber sensor based on MMF-FCF-MMF structure for dual-parameter detection

In this paper, a novel optical fiber sensor based on multimode fiber (MMF) - four-core fiber (FCF)-MMF structure is proposed and experimentally demonstrated. The device consists of a segment of FCF sandwiched between two MMFs. The MMFs are used to improve the light coupling efficiency between the input single mode fiber (SMF) and the FCF, and the FCF is used as sensing arm. Due to the multipath interference configuration embedded in one fiber, higher phase sensitivity can be obtained in our scheme. The maximum fringe visibility of the interference resonance dips exceeds 26.3 dB. The interference fringe of the sensor would shift with the variation of liquid level and temperature. So it is possible to measure dual-parameter simultaneously by simply monitoring the different wavelength shift. For 10 pm wavelength resolution, the resolution of the sensor is 0.14 cm and 2.08 °C in liquid level and temperature, respectively. Moreover, the proposed sensor has the advantages of simple fabrication process, good stability, repeatability and high fringe visibility, which mean it has a broad application prospect in liquid level measurement.

A Long Period Grating Sensor Based on Helical Capillary Optical Fiber

We proposed a high sensitivity long-period fiber grating strain and temperature sensor. The sensor is composed of input single mode fiber (SMF), helical capillary optical fiber (HCOF), and output SMF in cascade. By using a fusion junction structure between SMF and HCOF, almost all the light from input SMF can be coupled to the silica cladding of HCOF, and then modulated by HCOF. Because the light propagates in the same channel as the silica cladding of HCOF, the sensor is insensitive to refractive index (RI) change but has a high sensitivity to stress and temperature. The experiment results show that the strain sensitivity can reach -9.29 pm/μ ε when the hollow air capillary diameter and twisting pitch of HCOF are 10 μm and 1.2 mm, respectively. And the temperature sensitivity can reach 17.14 pm/°C in this condition. The sensing characteristics of the sensor are related to the diameter of the hollow air capillary and the twisting pitch of HCOF. Benefiting from eliminating the cross-influence of strain and temperature, the sensor may have the potential to realize stress detection in a harsh environment.

Quantum memories and the double-slit experiment: implications for astronomical interferometry

Thomas Young’s slit experiment lies at the heart of classical interference and quantum mechanics. Over the last 50 years, it has been shown that particles (e.g., photons, electrons, large molecules), even individual particles, generate an interference pattern at a distant screen after passage through a double slit, thereby demonstrating wave-particle duality. We revisit this famous experiment by replacing both slits with single-mode fiber inputs to two independent quantum memories that are capable of storing the incident electromagnetic field’s amplitude and phase as a function of time. At a later time, the action is reversed: the quantum memories are read out in synchrony, and the single-mode fiber outputs are allowed to interact, consistent with the original observation. In contrast to any classical memory device, the write and read processes of a quantum memory are non-destructive and hence preserve the photonic quantum states. In principle, with sufficiently long storage times and sufficiently high photonic storage capacity, quantum memories operating at widely separated telescopes can be brought together to achieve optical interferometry over arbitrarily long baselines.

M6 formalism – generalization of the laser beam quality factor M2 to the 3D domain

Abstract Here we define a theoretical basis for the generalization of the beam quality factor M2 to three-dimensional (3D) space, which we call M6 formalism. The formalism is established through the use of examples of multifocal and Axicon optical systems to illustrate discrete and continuous axial beam shaping, respectively. For the continuous case, we expand the definition of the Rayleigh range to incorporate a quality factor having both axial and transverse components M add 2 $M_{{\rm{add}}}^2$ and M2. Using geometrical ray tracing simulations, a proportion factor C is found to empirically describe the axial quality factor M z 2 $M_z^2$ of an optical setup including an Axicon and a paraxial focusing lens with a Gaussian single mode input beam. Using our M6 formalism depth of focus (DOF) ranges are calculated for higher M2 beams, and are shown to be in good agreement with the simulated DOF range, demonstrating the usefulness of the M6 formalism for the design of real optical systems.

Numerical analysis of planar multimode optical sensor with active nanolayer

In the paper, numerical studies of the model of an optical sensor, based on interference of modes in a planar one-dimensional step-index configuration, are presented. Calculations are performed using the method of mode field analysis. The structure consists of the single-mode input waveguide, the multimode waveguide that guides only a few modes and the single-mode output waveguide. The structure is covered by a nanometer active sensor layer of a high refractive index, which changes its optical properties in contact with the measured external surrounding. The refractive index variation of an active sensor layer affects the modal properties of the multimode waveguide and the output optical field distribution. By the proper selection of the active layer, the considered configuration can be used for gas detection.

Modeling multivariate dependencies for manufacturing single-mode I/O structures of integrated MMI-based splitters in glass sheets

For the realization of integrated optical interconnect systems, optical waveguide components are needed. A promising approach to manufacturing graded-index waveguide components is their embedding in thin glass sheets by ion-exchange processes. Conventionally, the modeling of integrated waveguide components manufactured by thermal diffusion processes involves the numerical solution of differential equations. In this work, a semi-analytical approach for the modeling of the concentration profile is extended by the Gauss–Newton optimization algorithm. This is done with the specific purpose of accurately modeling single-mode input and output waveguide structures of multimode-interference-based (MMI-based) optical splitters. The constraints imposed by the multivariate manufacturing process for the realization of these MMI-based components are elaborated. Corresponding correlations between these constraints and the according modeling of the devices are established.

Realization of linear-mapping between polarization Poincaré sphere and orbital Poincaré sphere based on stress birefringence in the few-mode fiber.

Based on the spatial profiles and polarization states evolution process of the first-order modes resulted from stress-induced birefringence in the few-mode fiber (FMF), we analyze the mapping relationship between the input polarization states represented on polarization PS and the output spatial profiles represented on the orbital PS of the FMF with respect to the magnitude and orientation of birefringence. When the input mode lobe orientation and the phase differences between the four eigenmodes of FMF induced by the stress birefringence satisfy a given condition, the mapping relationship between the input polarization PS and the output orbital PS is linear. Thus, the arbitrary points on the orbit PS can be generated at the output of stressed FMF by controlling the polarization state of the input modes. Then we experimentally verify that, an electrical single-mode polarization controller, a mode converter for converting fundamental mode to higher-order mode, a polarization controller mounting a coil of two-mode fiber and a polarizer can be employed to generate arbitrary first-order spatial modes on the orbital PS by controlling the input single-mode polarization states. The positions on the orbital PS of the generated first-order modes, which are obtained by calculating the three normalized Stokes parameters of output modes, agree well with the simulation ones. The correlation coefficients between the theoretical mode profiles and the experimental ones are higher than 80%. Since the spatial profile evolutions depend on the variations of the input polarization states, a potential advantage of this method is high-speed switching among desired first-order modes by using the commercial devices switching the state of polarization.

Cascaded FPI/LPFG interferometer for high-precision simultaneous measurement of strain and temperature

Abstract An all-fiber and low-cost strain and temperature sensor realized by the cascaded FPI/LPFG interferometer was developed. This device consists of an input single mode fiber (SMF), hollow core fibers (HCF), a long-period fiber grating (LPFG) inscribed by the CO2 laser pulses, and an output SMF. The Fabry-Perot interferometer (FPI) is insensitive to temperature and its reflective spectrum is utilized for strain measurement while the transmission spectrum of the LPFG is only utilized for temperature measurement. The actual measurement shows that the strain sensitivity of the proposed hybrid FPI/LPFG sensor can reach 4.16 pm/μe within the strain range of 0–1500 μe, meanwhile, the temperature sensitivity is 135.19 pm/°C when the temperature rises from room temperature to 82.11 °C. In addition, the proposed hybrid FPI/LPFG sensor has excellent linear response characteristics, and the R-Square values of the linear fitting curve of strain and temperature are 0.9995 and 0.9936, respectively. Therefore, the proposed hybrid FPI/LPFG sensor can simultaneously measure strain and temperature in the same location in the application field.