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Abstract The programmable photonic integrated mesh is arising as a powerful tool to deal with crosstalk in the multimode optical communication link.

Abstract Photonic integrated circuits have been extensively explored for optical processing with the aim of breaking the speed and energy efficiency bottlenecks of digital electronics. However, the input/output (IO) bottleneck remains one of the key barriers. Here we report a photonic iterative processor (PIP) for matrix-inversion-intensive applications. The direct reuse of inputted data in the optical domain unlocks the potential to break the IO bottleneck. We demonstrate notable IO advantages with a lossless PIP for real-valued matrix inversion and integral-differential equation solving, as well as a coherent PIP with optical loops integrated on-chip, enabling complex-valued computation and a net inversion time of 1.2 ns. Furthermore, we estimate at least an order of magnitude enhancement in IO efficiency of a PIP over photonic single-pass processors and the state-of-the-art electronic processors for reservoir training tasks and multiple-input and multiple-output (MIMO) precoding tasks, indicating the huge potential of PIP technology in practical applications.

Abstract Optical spectroscopic sensors are a powerful tool to reveal light-matter interactions in many fields. Miniaturizing the currently bulky spectrometers has become imperative for the wide range of applications that demand in situ or even in vitro characterization systems, a field that is growing rapidly. In this paper, we propose a novel integrated reconstructive spectrometer with programmable photonic circuits by simply using a few engineered MZI elements. This design effectively creates an exponentially scalable number of uncorrelated sampling channels over an ultra-broad bandwidth without incurring additional hardware costs, enabling ultra-high resolution down to single-digit picometers. Experimentally, we implement an on-chip spectrometer with a 6-stage cascaded MZI structure and demonstrate 200 nm bandwidth using only 729 sampling channels. This achieves a bandwidth-to-resolution ratio of over 20,000, which is, to our best knowledge, about one order of magnitude greater than any reported miniaturized spectrometers to date.

When a ship sails in shallow water, it will show different hydrodynamic performance from that in deep water due to the limitations of water depth. The shallow water effect may lead to hull sinkage and trim, increasing the risk of bottoming or collision. In this study, a new design scheme of a shallow-water seismic survey vessel is proposed to solve the problems of traditional seismic survey vessels in shallow-water marine resources exploration and safety. The RANS (the Reynolds-Averaged Navier–Stokes) method combined with the Overset Mesh and DFBI (Dynamic Fluid Body Interaction) method is used for numerical simulation to analyze the influence of ship type, water depth, and speed on ship sinkage and trim, as well as the influence of the shallow-water ship’s attitude on resistance. The results show that with the decrease in water depth and the increase in speed, the pressure distribution around the hull becomes uneven, which leads to the aggravation of the sinkage and trim of the hull. In response to this problem, the shallow-water seismic survey vessel significantly improved the sinkage and trim of the hull in shallow water to ensure its safe navigation. The research also shows that navigation resistance can be effectively reduced by appropriately adjusting the ship’s attitude. Therefore, this study provides a reference for the development of shallow-water ships in the future.

Abstract Miniaturization of optical spectrometers is important to enable spectroscopic analysis to play a role in in situ, or even in vitro and in vivo characterization systems. However, scaled-down spectrometers generally exhibit a strong trade-off between spectral resolution and operating bandwidth, and are often engineered to identify signature spectral peaks only for specific applications. In this paper, we propose and demonstrate a novel global sampling strategy with distributed filters for generating ultra-broadband pseudo-random spectral responses. The geometry of all-pass ring filters is tailored to ensure small self- and cross-correlation for effective information acquisition across the whole spectrum, which dramatically reduces the requirement on sampling channels. We employ the power of reconfigurable photonics in spectrum shaping by embedding the engineered distributed filters. Using a moderate mesh of MZIs, we create 256 diverse spectral responses on a single chip and demonstrate a resolution of 20 pm for single spectral lines and 30 pm for dual spectral lines over a broad bandwidth of 115 nm, to the best of our knowledge achieving a new record of bandwidth-to-resolution ratio. Rigorous simulations reveal that this design will readily be able to achieve single-picometer-scale resolution. We further show that the reconfigurable photonics provides an extra degree of programmability, enabling user-defined features on resolution, computation complexity, and relative error. The use of SiN integration platform enables the spectrometer to exhibit excellent thermal stability of ±2.0 °C, effectively tackling the challenge of temperature variations at picometer-scale resolutions.

The glycosylation levels of proteins in cancer cells are closely related to cancer invasion and migration. CD44 is a transmembrane glycoprotein that is significantly overexpressed in a variety of tumor cells and has been proven to promote the migration and motility of cancer cells, but the effect of its N-glycosylation modification on CD44 protein function in tumors is less studied. Here, we investigated the effect of six N-glycan chains (N25/57/100/110/120/255) on CD44s localization, function and stability in hepatocarcinoma cells. When the six sites were mutated, we found that CD44s lost its membrane localization in Huh7 and MHCC-97H cells. On this basis, we identified three glycosylation sites on CD44s (N57, N100 and N110) that played key roles in intracellular localization. When N57, N100 and N110 were mutated together, CD44 localized to the cytoplasm, while another three-site mutant (N25/N120/N255) was still anchored to the membrane. In addition, the ability of CD44-N57Q/N100Q/N110Q to promote the metastasis and invasion of Huh7 and 97H cells was weakened compared with that of CD44-N25Q/N120Q/N255Q. Furthermore, CD44-N57Q/N100Q/N110Q accumulated abnormally in the ER, and a high level of the ER stress (ERS) marker BiP was detected at the same time compared with wild-type CD44. When the lysosome inhibitor CQ was added, the content of mutant protein that triggered ERS significantly increased, which indicated that the degradation mode of CD44-N57Q/N100Q/N110Q after ERS was mainly through the lysosomal pathway (ERLAD). The results revealed that the N-glycosylation sites N57, N100 and N110 mutated on CD44s affected its function and degraded it by lysosomes after triggering ERS. These findings provide data for new studies on ER-related degradation, further promote the study of the glycan chain function of CD44 and furnish new ideas for the treatment of liver cancer metastasis.

Abstract The proliferation of Internet-of-Things has promoted a wide variety of emerging applications that require compact, lightweight, and low-cost optical spectrometers. While substantial progresses have been made in the miniaturization of spectrometers, most of them are with a major focus on the technical side but tend to feature a lower technology readiness level for manufacturability. More importantly, in spite of the advancement in miniaturized spectrometers, their performance and the metrics of real-life applications have seldomly been connected but are highly important. This review paper shows the market trend for chip-scale spectrometers and analyzes the key metrics that are required to adopt miniaturized spectrometers in real-life applications. Recent progress addressing the challenges of miniaturization of spectrometers is summarized, paying a special attention to the CMOS-compatible fabrication platform that shows a clear pathway to massive production. Insights for ways forward are also presented.

In this paper, we propose a faster-than-Nyquist non-orthogonal frequency-division multiplexing (NOFDM) scheme for visible light communications (VLCs) where the multiplexing/demultiplexing employs the inverse fractional cosine transform (IFrCT)/FrCT. Different to the common fractional Fourier transform-based NOFDM (FrFT-NOFDM) signal, FrCT-based NOFDM (FrCT-NOFDM) signal is real-valued, which can be directly applied to the VLC systems without the expensive up-conversion and thus it is more suitable for the cost-sensitive VLC systems. Under the same transmission rate, FrCT-NOFDM signal occupies smaller bandwidth compared to OFDM signal. When the bandwidth compression factor α is set to 0.8, 20% bandwidth saving can be obtained. Therefore, FrCT-NOFDM has higher spectral efficiency and suffers less high-frequency distortion compared to OFDM, which benefits the bandwidth-limited VLC systems. As the simulation results show, bit error rate performance of FrCT-NOFDM with α of 0.9 or 0.8 is better than that of OFDM. Meanwhile, FrCT-NOFDM has a superior security performance. In conclusion, FrCT-NOFDM shows the potential for application in the future VLC systems.

Abstract Faster-than-Nyquist (FTN) signal achieves higher spectral efficiency and capacity compared to Nyquist signal due to its smaller pulse interval or narrower subcarrier spacing. Shannon limit typically defines the upper-limit capacity of Nyquist signal. To the best of our knowledge, the mathematical expression for the capacity limit of FTN non-orthogonal frequency-division multiplexing (NOFDM) signal is first demonstrated in this paper. The mathematical expression shows that FTN NOFDM signal has the potential to achieve a higher capacity limit compared to Nyquist signal. In this paper, we demonstrate the principle of FTN NOFDM by taking fractional cosine transform-based NOFDM (FrCT-NOFDM) for instance. FrCT-NOFDM is first proposed and implemented by both simulation and experiment. When the bandwidth compression factor α is set to 0.8 in FrCT-NOFDM, the subcarrier spacing is equal to 40% of the symbol rate per subcarrier, thus the transmission rate is about 25% faster than Nyquist rate. FTN NOFDM with higher capacity would be promising in the future communication systems, especially in the bandwidth-limited applications.

A novel low-cost and energy-efficient approach for reaching 40 Gb/s signals is proposed for cost-sensitive optical access networks. Our proposed design is constituted of an innovative low-complex high-performance digital signal processing (DSP) architecture for pulse amplitude modulation (PAM-4), reuses existing commercial cost-effective 10-G components and eliminates the need of a power-hungry radio frequency (RF) component in the transmitter. Using a multi-functional 17-tap reconfigurable adaptive Volterra-based nonlinear equalizer with noise suppression, significant improvement in receiver optical power sensitivity is achieved. Results show that over 30 km of single-mode fiber (SMF) a link power budget of 33 dB is feasible at a bit-error-rate (BER) threshold of 10−3.

Heating elements are used to tune the optical properties of silicon photonic devices, to stabilize operating temperatures, and to compensate for fabrication variations. In this paper, we characterize the transient thermal response and develop models for silicon photonic devices equipped with such heating mechanisms. To demonstrate the usefulness and practicality of the proposedmodels, we investigate pulse widthmodulation (PWM) drive scheme for microheaters and experimentally demonstrate its use in stabilizing microring resonators by digital driving signals (twolevel voltage). Requirements on the drive frequency and duty cycle of the PWM signal to minimize optical power penalties owing to the undesired thermal ripples are discussed based on the accurately modeled thermal frequency response of the heater-ring system. It is shown that smaller duty cycles require higher drive frequencies and the maximum optical ripple for a microring resonator occurs at 65% duty cycle. [ABSTRACT FROM AUTHOR]

Hybrid multiband (HMB) CAP/QAM transmitter/receiver systems are proposed for the first time. Simulation results are provided to show the feasibility of 100 Gb Ethernet links employing a single-laser source transmitting HMB CAP-16/QAM-16, CAP-32/QAM-32, and CAP-64/QAM-64 signals. The proposed hybrid scheme has low sensitivity to directly modulated laser nonlinearities. We found that QAM receivers bring about identical jitter tolerance to ideally phase compensated CAP receivers, and QAM receivers are more practical since no phase tracking and compensation are required. Compared with the case of using a standard non phase compensated CAP receiver, the use of the modified QAM-16/32/64 receiver significantly lowers system timing jitter sensitivity in the multiband, as well as single-band case. Results also showthat the use of increasing number of bands causes increased system power margin. For practical jitter conditions of ±6 ps, three HMB CAP/QAM systems with optimum band counts are identified to be capable of supporting single-laser 100 Gb/s transmission over 15-km SMF. [ABSTRACT FROM AUTHOR]