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During multi-dimensional optical transmission, because of photodetector (PD) operation as a square law detector, signals get distorted when they are modulated on polarization and phase due to interdimensional interference (IDI) by intensity-modulated signals. We propose an IDI mitigation technique using recurrent neural network for multi-dimensional optical transmission. The signal transmission performance of the proposed equalization technique was experimentally analyzed. The performance of the proposed system was verified using the symbol error rate (SER).

A novel concept for single wavelength high spectral-efficient multi-dimensional optical transmission with geometric and probabilistic constellation shaping and bit mapping technique is presented in this study. We propose a simultaneous Hexagonal RF-Quadrature Amplitude Modulation – Differential Phase Shift Keying(HQAM-DPSK) optical modulation for spectral efficient optical transmission. In order to mitigate signal distortion by inter-dimensional interference between intensity and phase, constellation shaping technique is applied to multi-dimensional optical transmission scheme. The validity of the proposed scheme is demonstrated by optical fiber transmission simulation.

We report a multi–dimensional quadrature amplitude modulation with M-ary differential phase shift keying (QAM-MDPSK) modulation for optical access network transmission systems employing a Mach–Zehnder modulator (MZM) and a phase modulator (PM) in a direct detection system. Even though several problems that occur in a QAM-DPSK employing a single MZM were solved, inter-signal distortion between two modulations remains when the optical phase signal is converted into an optical intensity signal for detection. To maximize the transmission capacity of QAM-MDPSK, the effect of inter-signal distortion in QAM-MDPSK need to be analyzed for optimization. Mathematical analysis and simulations were performed to evaluate inter-signal distortion. Furthermore, experimental transmission on the proposed QAM-MDPSK modulation has been performed to verify the inter-signal distortion analysis.

In optical transmission technique using optical polarization, the change of state of polarization (SOP) and the rotation of SOP (RSOP) during optical transmission has a significant impact on the transmission performance. We propose polarized intensity rotational frequency shift keying (PIR-FSK) as a novel modulation technique in change of SOP and RSOP-tolerant optical transmissions. The proposed PIR-FSK signal does not affect the entire intensity of the optical carrier by modulating the sinusoidal signals on each X and Y-polarized optical carrier. Therefore, the proposed PIR-FSK modulation and optical carrier intensity modulation can operate at the same time. Moreover, since the proposed technique does not modulate the signal using the SOP unlike the PolSK, PIR-FSK is not affected by SOP changes that occur during transmission, and the signal does not be degraded even with RSOP. We demonstrated that the signals modulated using the proposed PIR-FSK modulation have higher signal capacity and efficiency compared to the signal modulated using PolSK modulation.

Real-time monitoring human motions normally demands connecting a large number of sensors in a complicated network. To make it simpler, Kim et al. decode the motion of fingers using a flexible sensor attached on wrist that measures skin deformation with the help of a deep-learning architecture.

In coherent orthogonal frequency division multiple accessing technique-based passive optical network (CO-OFDMA-PON) uplink transmission, two main multiple-access noises (MNs), which are multiple- state-of-polarization leakages (SOPLs) and phase noises (PNs) inevitably occur by various optical network units (ONUs) and interfere with the uplink signal in this system. These MNs are different by optical devices and paths of each ONU. In this regard, parallel MNs handling per ONU is necessary to provide uplink service. We propose digital phase conjugated pilot-tones (DPC-PTs) based MNs compensation technique. This can deal with MNs by using superposition of two adjacent pilot subcarriers. In the experiments conducted, we applied a pair of DPC-PTs per ONU to handle two MNs and performed parallel processing for each ONU. The transmission performance in terms of root-mean-square error, error-vector magnitude, bit-error-rate (BER), and the overhead of redundant PTs was improved by using the proposed technique in 20-km CO-OFDMA-PON uplink transmission. Both MNs were effectively compensated by comparing transmitted and received DPC-PTs. Minimum overhead of 0.39 % OFDMA symbol duration was verified to meet BER target in the given transmission condition. It guarantees more accurate tracking of SOPL than single-PT-based one due to the doubled number of estimator samples. Besides, more accurate tracking of PNs is demonstrated due to lower noise level between DPC-PTs. As a result, applicability to the phase and polarization diversities-based coherent multiple access is demonstrated through the proposed MNs tracking technique.

Abstract Evolution has decided to gift an articular structure to vertebrates, but not to invertebrates, owing to their distinct survival strategies. An articular structure permits kinematic motion in creatures. However, it is inappropriate for creatures whose survival strategy depends on the high deformability of their body. Accordingly, a material in which the presence of the articular structure can be altered, allowing the use of two contradictory strategies, will be advantageous in diverse dynamic applications. Herein, spatial micro‐water molecule manipulation, termed engineering on variable occupation of water (EVO), that is used to realize a material with dual mechanical modes that exhibit extreme differences in stiffness is introduced. A transparent and homogeneous soft material (110 kPa) reversibly converts to an opaque material embodying a mechanical gradient (ranging from 1 GPa to 1 MPa) by on‐demand switching. Intensive theoretical analysis of EVO yields the design of spatial transformation scheme. The EVO gel accomplishes kinematic motion planning and shows great promise for multimodal kinematics. This approach paves the way for the development and application of smart functional materials.

Touch technology holds potential for the development of smartphones and touchscreens, yet the conventional devices are usually built on separate pressure and location sensing units. Kim et al. show a flexible and transparent touch sensor capable of mapping the position and pressure at the same time.

A novel spectrally efficient optical transmission in a passive optical network (PON) with hexagonal quadrature amplitude modulation (QAM)-based adaptive modulated optical (AMO) orthogonal frequency division multiplexing (OFDM) is proposed and experimentally demonstrated. With the help of hexagonal QAM and 4-dimensional (4D) modulation, adaptive bit loading is effectively processed to enhance the total data rate. In this approach, some subcarriers are aggregated to transmit integer bits. To employ hexagonal QAM-based 4D AMO-OFDM, the signal to noise (SNR) ratio is calculated using the measured error vector magnitude of the training signal. In our experiment, hexagonal QAM-based 4D AMO-OFDM transmission with a total data rate of 21 Gbps is demonstrated over a 20 km standard single mode fiber for two optical network units (ONUs). The experimental results show that the total data rate obtained using the proposed method is increased by 14% compared to the conventional square QAM-based AMO-OFDM.

We propose a modulation-based adaptive power allocation (MBAPA) technique for nonlinear distortion mitigation in intermediate frequency over fiber (IFoF) systems. The technique allocates the spectral power of each IF band according to the required signal-to-noise power ratio (SNR) of the modulation format. To demonstrate the performance of the technique, transmission experiments were performed in 10 km and 20 km with 24-IF bands using OFDM signals. The feasibility of the proposed MBAPA technique was experimentally verified by reducing inter-modulation distortion (IMD) power and enhancing channel linearity.

The article presents a study which explores the digital selective transformation and patterning of highly conductive hydrogel bioelectronics by laser-induced phase separation. It mentions that study demonstrated stable neural signal recording and stimulation with hydrogel electrodes fabricated by laser.