Search Results (157)

Signal detection and classification tasks, especially in the realm of audio, suffer from difficulties in capturing long short-term dependencies and effectively utilizing samples. Firstly, audio signal detection and classification need to classify audio signals and detect their onset and offset times; therefore, obtaining long short-term dependencies is necessary. The methods based on RNNs have high time complexity and dilated convolution-based methods suffer from the “gridding issue” challenge; thus, the HDC-Inception module is proposed to efficiently extract long short-term dependencies. Combining the advantages of the Inception module and a hybrid dilated convolution (HDC) framework, the HDC-Inception module can both alleviate the “gridding issue” and obtain long short-term dependencies. Secondly, datasets have large numbers of silent segments and too many samples for some signal types, which are redundant and less difficult to detect, and, therefore, should not be overly prioritized. Thus, selecting effective samples and guiding the training based on them is of great importance. Inspired by support vector machine (SVM), combining soft margin SVM and cross-entropy loss (CE loss), the soft margin CE loss is proposed. Soft margin CE loss can adaptively select support vectors (effective samples) in datasets and guide training based on the selected samples. To utilize datasets more sufficiently, a hybrid CE loss is proposed. Using the benefits of soft margin CE loss and CE loss, hybrid CE loss guides the training with all samples and gives weight to support vectors. Soft margin CE loss and hybrid CE loss can be extended to most classification tasks and offer a wide range of applications and great potential. Full article

The monolithic integration of gallium phosphide (GaP), with its green band gap, high refractive index, large optical non-linearity, and broad transmission range on silicon (Si) substrates, is crucial for Si-based optoelectronics and integrated photonics. However, material mismatches, including thermal expansion mismatch and polar/non-polar interfaces, cause defects such as stacking faults, microtwins, and anti-phase domains in GaP, adversely affecting its electronic properties. Our paper presents a structural and defect analysis using scanning transmission electron microscopy, high-resolution transmission electron microscopy, and scanning nanobeam electron diffraction of epitaxial GaP islands grown on Si nanotips embedded in SiO₂. The Si nanotips were fabricated on 200 mm n-type Si (001) wafers using a CMOS-compatible pilot line, and GaP islands were grown selectively on the tips via gas-source molecular-beam epitaxy. Two sets of samples were investigated: GaP islands nucleated on open Si nanotips and islands nucleated within self-organized nanocavities on top of the nanotips. Our results reveal that in both cases, the GaP islands align with the Si lattice without dislocations due to lattice mismatch. Defects in GaP islands are limited to microtwins and stacking faults. When GaP nucleates in the nanocavities, most defects are trapped, resulting in defect-free GaP islands. Our findings demonstrate an effective approach to mitigate defects in epitaxial GaP on Si nanotip wafers fabricated by CMOS-compatible processes. Full article

This paper presents a polarizing beam splitter (PBS) based on a hexagonal lattice silver-filled photonic crystal fiber (PCF) with two silver wires, which possesses advantages such as a short splitting length, high extinction ratio (ER), and an ultra-wide bandwidth in commonly used communication bands. Utilizing the full-vector finite element method (FV-FEM), thorough investigations were conducted on lasers within the wavelength range of 1.1 to 1.9 μm. The PBS demonstrates a working bandwidth of 725 nm (1.14 to 1.865 μm) under an ultra-short splitting length of 55.3 μm, with an ER exceeding 20 dB, covering all bands of O + E + S + C + L + U optical communication, and achieving a maximum ER of 74.65 dB, where the surface plasmon resonance (SPR) effect of silver metal plays a significant role. It not only features an ultra-short splitting length and an ultra-wide splitting bandwidth but also exhibits excellent manufacturing tolerances and anti-interference capabilities. This polarizing beam splitter represents a promising candidate in communication and may find various applications in optical communication. Full article

This paper addresses the design of a CMOS modulator to control two quantum bits. The proposed architecture offers several advantages that are addressed and discussed in this paper. The proposed architecture is investigated through both mathematical modeling and Verilog simulations. Moreover, the circuit was designed using the cryogenic Design Kit of the 130 nm SiGe BiCMOS technology of the IHP foundry. The observed agreement between the modeling, Verilog, and transistor-level simulations proves the physical feasibility of the proposed architecture. Full article

The capacity of passive optical networks (PONs) is continuously increasing, and it has been standardized up to 50 Gbit/s. The two main standardization organizations, IEEE and ITU-T, are actively working on the next-generation PON, which appears to be a 100G-PON still based on intensity modulation. Even though direct detection would be preferred for its cost and simplicity, the choice of coherent detection seems inevitable when the bit rate reaches 200–400 Gbit/s, specifically to guarantee the optical power budget requirement of an access network. The introduction of coherent systems in the PON scenario, allowing high-power-budget performances, should encouragetelecom operators to merge the metro and access networks into a single domain. This paper analyzes the mentioned metro + PON convergence scenario with experimental results focusing on a 400 Gbit/s fully coherent transmission (50 GBaud PM-16QAM). We characterize three different transceivers, two of which are pre-commercials. We perform experimental demonstrations, with real urban fiber and laboratory set ups, of the metro–access convergence network in terms of the minimum OSNR value of the metro path, producing an acceptable optical power budget within the access network. Our work demonstrates feasibility of merging the metro–access network by using currently coherent optical transceivers for PON applications. Full article

In the literature, three-stage switching networks have been considered for nodes in elastic optical networks, where switches with spectrum conversion capability are placed in the first and third stages (wavelength–space–wavelength—WSW) or only in the second stage (space–wavelength–space—SWS). This paper proposes three-stage switching networks where the switches with spectrum conversion functions are located only in the first stage (wavelength–space–space—WSS) or only in the third stage (space–space–wavelength—SSW). For these networks, the strict-sense non-blocking conditions are derived and proved, and the number of elements required for their construction is assessed. It turns out that the proposed networks can be constructed with 50% fewer tunable spectrum converters than in the WSW networks, and this reduction is even greater in the case of the SWS networks. Full article

Since the advent of GPT, large language models (LLMs) have brought about revolutionary advancements in all walks of life. As a superior natural language processing (NLP) technology, LLMs have consistently achieved state-of-the-art performance in numerous areas. However, LLMs are considered to be general-purpose models for NLP tasks, which may encounter challenges when applied to complex tasks in specialized fields such as optical networks. In this study, we propose a framework of LLM-empowered optical networks, facilitating intelligent control of the physical layer and efficient interaction with the application layer through an LLM-driven agent (AI-Agent) deployed in the control layer. The AI-Agent can leverage external tools and extract domain knowledge from a comprehensive resource library specifically established for optical networks. This is achieved through user input and well-crafted prompts, enabling the generation of control instructions and result representations for autonomous operation and maintenance in optical networks. To improve LLM’s capability in professional fields and stimulate its potential on complex tasks, the details of performing prompt engineering, establishing domain knowledge library, and implementing complex tasks are illustrated in this study. Moreover, the proposed framework is verified on two typical tasks: network alarm analysis and network performance optimization. The good response accuracies and semantic similarities of 2400 test situations exhibit the great potential of LLM in optical networks. Full article

Due to its complex spatial distribution, the higher-order Hermite–Gaussian mode possesses significant application in fields such as precision measurement and optical communication. The spatial light modulator, with its capability to modulate the complex amplitude distribution of the incident light field, finds extensive applications in optical information processing and adaptive optics, thus making it an indispensable tool in these fields. Using cascaded spatial light modulators can efficiently and superbly generate a higher-order Hermite–Gaussian mode; however, the experimental system is challenging, and there are many influencing factors, such as the misalignment between the optical field on the plane of the second spatial light modulator and the hologram loaded onto it, as well as the spot size of the optical field on the plane of the second spatial light modulator. In this paper, we analyzed the influence of the above factors on the quality of generating a higher-order Hermite–Gaussian mode, providing a reference for the efficient and high-quality generation of the higher-order Hermite–Gaussian mode. Full article

In the application domain of large-scale high-precision measurement systems, accurately calibrating the precision of point position measurements is a pivotal issue. Traditional calibration methods rely on laser interferometers and high-precision displacement stages, which are not only costly but also challenging to implement in fixed measurement systems. Addressing this challenge, this study introduces an evaluation method for the spatial point measurement accuracy in large-scale fixed high-precision measurement systems. The models for the relationship between the limit deviation and the maximum deviation of finite measurements were established, as well as the limit deviation and point position measurement accuracy. The spatial point position accuracy of the measurement field was calculated by the measurement errors of a calibration rod. The algorithm was validated using a large-scale measurement platform based on photogrammetric technology. Experimental results demonstrate that the method achieved a point position measurement accuracy calibration better than 0.1 mm within a 20 m measurement range, effectively enhancing the measurement data’s accuracy and reliability. This research optimizes the calibration process for large-scale fixed measurement systems, improves calibration efficiency, and obviates the need for complex equipment to complete the calibration process, which is of considerable importance to the development of high-precision spatial point position measurement technology. Full article

This paper presents a novel pentagonal structure dual-core photonic crystal fiber polarizing beam splitter (PS-DC-PCF PBS) filled with a nematic liquid crystal (NLC) in the central hole. Unlike previous designs with symmetric arrangements, the upper and lower halves of the structure have different air hole arrangements. The upper half consists of air holes arranged in a regular quadrilateral pattern, while the lower half features a regular hexagonal arrangement of air holes. By filling the central hole with birefringent liquid crystal, the birefringence of the structure is enhanced, reducing the coupling lengths along the x polarization and y polarization directions. The polarization properties, coupling characteristics, and the influence of different structural parameters on the extinction ratio of the polarizing beam splitter are analyzed using the full-vector finite element method. Simulation results demonstrate that the designed PS-DC-PCF PBS achieves a maximum extinction ratio (ER) of 72.94 dB with a splitting length of only 61.9 μm and a wide operating bandwidth of 423 nm (1.324–1.747 μm), covering most of the O, E, S, C, L, and U communication bands. It exhibits not only ultra-short splitting lengths and ultra-wide splitting bandwidth but also good manufacturing tolerances and anti-interference capabilities. The designed PS-DC-PCF PBS could provide crucial device support for future all-optical communication systems and has potential applications in fiber optic communication or fiber laser systems. Full article

The pulse-coupled neural network (PCNN), due to its effectiveness in simulating the mammalian visual system to perceive and understand visual information, has been widely applied in the fields of image segmentation and image fusion. To address the issues of low contrast and the loss of detail information in infrared and visible light image fusion, this paper proposes a novel image fusion method based on an improved adaptive dual-channel PCNN model in the non-subsampled shearlet transform (NSST) domain. Firstly, NSST is used to decompose the infrared and visible light images into a series of high-pass sub-bands and a low-pass sub-band, respectively. Next, the PCNN models are stimulated using the weighted sum of the eight-neighborhood Laplacian of the high-pass sub-bands and the energy activity of the low-pass sub-band. The high-pass sub-bands are fused using local structural information as the basis for the linking strength for the PCNN, while the low-pass sub-band is fused using a linking strength based on multiscale morphological gradients. Finally, the fused high-pass and low-pass sub-bands are reconstructed to obtain the fused image. Comparative experiments demonstrate that, subjectively, this method effectively enhances the contrast of scenes and targets while preserving the detail information of the source images. Compared to the best mean values of the objective evaluation metrics of the compared methods, the proposed method shows improvements of 2.35%, 3.49%, and 11.60% in information entropy, mutual information, and standard deviation, respectively. Full article

Optical fibres are gaining popularity for relative dosimetry in proton therapy due to their spatial resolution and ability for near real-time acquisition. For FLASH proton therapy, these fibres need to handle higher dose rates and larger doses than for conventional proton dose rates. We developed a multi-point fibre sensor embedded in a 3D-printed phantom which can measure the profile of a FLASH proton beam. Seven PMMA fibres of 1 mm diameter were embedded in a custom 3D-printed plastic phantom of the same density as the fibres. The phantom was placed in a proton beam with FLASH dose rates at the TRIUMF Proton Therapy Research Centre (PTRC). The sensor was exposed to different proton energies, 13.5 MeV, 19 MeV and 40.4 MeV, achieved by adding PMMA bolus in front of the phantom and three different beam currents, varying the dose rates from 7.5 to 101 Gy/s. The array was able to record beam profiles in both transverse and axial directions in relative agreement with measurements from EBT-XD radiochromic films (transverse) and Monte Carlo simulations (axial). A decrease in light output over time was observed, which might be caused by radiation damage in the matrix of the fibre and characterised by an exponential decay function. Full article

In this paper, we propose a novel type of hollow-core anti-resonance fiber (HC-ARF). The cladding region of this fiber is formed by a combination of nested tubes and U-shaped tubes, and the centrally symmetric arrangement significantly reduces sensitivity to polarization. The influence of parameters on the performance of the designed HC-ARF LMA is analyzed by a finite element algorithm. The simulation results demonstrate that the designed structure achieves a large mode area of 3180 µm², bending loss of 2 × 10⁻² dB/km, and confinement loss of 5 × 10⁻³ dB/km at a wavelength of 1064 nm. Similarly, at a wavelength of 1550 nm, the large mode area, bending loss, and confinement loss are 3180 µm², 1.4 × 10⁻² dB/km, and 4 × 10⁻² dB/km, respectively. These results indicate unprecedentedly large mode areas and ultra-low losses compared to previous studies. Within the bending radius under consideration, the bending loss remains below 1.35 × 10⁻² dB/km. Furthermore, by increasing the fiber radius, the large mode area can reach an extraordinary 6250 µm². The proposed device exhibits excellent mode area and outstanding polarization insensitivity, along with favorable bending performance. We believe that the designed fiber holds promising applications in high-power miniaturized fiber lasers, fiber amplifiers, and various high-power fiber communication systems, and it can be applied in sensors that require polarization insensitivity and better bending performance. Full article

With the development of the Internet and information technology, optical fiber communication systems need to meet people’s information demand for large capacity and high speed. High-order phase modulation and channel multiplexing can improve the capacity and data rate of optical fiber communication systems, but they also bring the problem of bit error. To improve the transmission quality and reliability of optical fiber communication systems, forward error correction (FEC) coding techniques are commonly used, which serve as the fundamental approach to enhance the quality and reliability of fiber optic communication systems, ensuring that the received data remain accurate and reliable. The FEC in optical fiber communication systems is divided into three generations. The first generation FEC is mainly hard decision codewords, represented as RS code. The second generation FEC is mainly cascaded code, which stands for interleaved cascaded code. The third generation of FEC mainly refers to soft decision codes, which are represented as low-density parity-check (LDPC) codes. As a kind of FEC, LDPC codes stand out as pivotal contributors in the field of optical communication and have gained remarkable attention due to exceptional error correction performance and low decoding complexity. Based on IEEE802.16e standard, LDPC code with specific code length and rate is compiled and simulated in MATLAB and VPItransmissionMaker 10.1 and successfully incorporated into polarization multiplexed differential quadrature phase shift keying (PM-DQPSK) coherent optical transmission system. The simulation results indicate that the bit error rate (BER) can be reduced to 10⁻³ when the optical signal-to-noise ratio (OSNR) reaches 14.2 dB, and the BER experiences a reduction by nearly three orders of magnitude when the OSNR is 17.2 dB. These findings underscore the efficacy of LDPC codes in significantly improving the performance of optical communication systems, particularly in scenarios demanding robust error correction capabilities. This study provides valuable, significant results regarding the potential of LDPC codes for enhancing the reliability of optical transmission in real-world applications. Full article

Advanced electronics technology is moving towards smaller footprints and higher computational power. In order to achieve this, advanced packaging techniques are currently being considered, including organic, glass, and semiconductor-based substrates that allow for 2.5D or 3D integration of chips and devices. Metal-core substrates are a new alternative with similar properties to those of semiconductor-based substrates but with the added benefits of higher flexibility and metal ductility. This work comprehensively compares the thermal properties of a novel metal-based substrate, molybdenum, and silicon and fused silica glass substrates in the context of system-on-foil (SoF) integration. A simple electronic technique is used to simulate the heat generated by a typical CPU and to measure the heat dissipation properties of the substrates. The results indicate that molybdenum and silicon are able to effectively dissipate a continuous power density of 2.3 W/mm² as the surface temperature only increases by ~15 °C. In contrast, the surface temperature of fused silica glass substrates increases by >140 °C for the same applied power. These simple techniques and measurements were validated with infrared camera measurements as well as through finite element analysis via COMSOL simulation. The results validate the use of molybdenum as an advanced packaging substrate and can be used to characterize new substrates and approaches for advanced packaging. Full article