In coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, the high peak-average-power ratio (PAPR) is the major disadvantage that impacts the system performance, which is manifested in limiting the maximum power of lasers and exacerbating the fiber nonlinear effects. Therefore, a novel PAPR reduction scheme using improved selective mapping (ISLM) cascading neural network (NN)-based companding algorithm is proposed. Compared with the original OFDM and the single traditional scheme, the proposed scheme shows better PAPR reduction effect and bit error rate (BER) performance. Compared with the cascaded scheme, the proposed scheme has the similar effect but lower complexity.
The recently presented coherent point-to-multipoint transceivers (P2MP-TRXs), which are enabled by digital subcarrier modulation, have been viewed as a promising substitute for the point-to-point transceivers, especially for the network segments with hub-and-spoke traffic patterns. This paper studies the network planning of wavelength-switched optical networks with P2MP-TRXs, which includes correlated routing and spectrum assignment, placement of P2MP-TRXs in groups and corresponding subcarrier assignments. We design an efficient heuristic to find near-optimal solutions in polynomial time.
An all-optical plasmonic modulator working at visible wavelengths based on graphene/black phosphorus heterostructure is proposed. This modulator is capable of operating from $400 \mathrm{~nm}$ to $800 \mathrm{~nm}$ with large extinction ratio up to $55 \mathrm{~dB}$.
A bandwidth and wavelength tunable filter and its application in fiber lasers are demonstrated. The continuous wavelength-tunable and the start-up and extinction dynamics of pulse in the Mamyshev oscillator have been studied with the filter.
In this paper, we propose and experimentally demonstrate a refractive index (RI) sensing system using an extrinsic Fabry-Perot interferometer (EFPI) structure based microwave photonic filter (MPF). Two EFPI sensors with cavity lengths of $500 \mu \mathrm{m}$ and $960 \mu \mathrm{m}$ have been fabricated, and the sensitivities of 627.953 MHz/RIU and 1201.653 MHz/RIU have been achieved, respectively. The proposed sensing system has the advantages such as high sensitivity, good linearity, and enlarged measurement range.
A novel superimposed fiber grating sensor for bending and temperature measurement has been proposed. The sensor exhibited high bending and temperature sensitivities of $17.096 \mathrm{~nm} / \mathrm{m}^{-1}$ and $-0.238 \mathrm{~nm} /^{\circ} \mathrm{C}$, respectively.
A short carbon nanotubes (CNTs) nano-film based polymer/SiO2 hybrid waveguide on-chip micro-ring filter is presented. The film can effectively improve the coherent depth and quality factor of the on-chip filter. The filter shows good all-optical controllable performance due to the excellent thermo-optic effect of the CNTs nano-film. Since the chip shows the advantages of small size, compact structure, and all-optical control, and it is expected to have practical applications in optical filters, optical sensors, spectral analysis, and so on.
In this study, a U-shaped few-mode fiber (FMF) sensor for blood glucose brix measurement is proposed, which is temperature-insensitive. These sensors with smaller bending diameters can be obtained by bending single-mode fiber (SMF)-FMF-SMF. The light leaks from fiber core to fiber cladding because the bending, which results in the occurrence of modal interference. The experiments show that the maximum blood glucose brix sensitivity is up to $1.081 \text{nm} / \%$ in the blood glucose brix range of 0%-18%, when the bending diameter is $\sim 1 \text{mm}$. And the sensors are temperature-insensitive in the temperature range of $10^{\circ} \text{C}-40^{\circ} \text{C}$. The sensor has advantages of compact structure and high sensitivity. Therefore, the sensor is suitable for applications in fields such as biomedicine.
In this paper, we report an all-fiber 4-mode fiber multiplexer and its measurement, which uses a fused tapering method to fabricate different mode-selective coupler. The insertion loss of a single mode-selective is less than 0.7dB, the insertion loss of LP 01 , LP 11 , LP 21 and LP 02 is less than 3 dB after cascading, while the modal crosstalk is lower than −15dB. This device can be applied in mode-division multiplexing transmission systems.
Algorithm using wavelet packet decomposition and 1D convolutional neural network is proposed to improve recognition accuracy of distributed fiber optic vibration sensor for natural gas pipeline monitoring, achieving average recognition accuracy of >98%.
FOCS current signals are measured by LIA when sensing coils under low frequency vibrations $(\mathbf{1 0} \sim \mathbf{2 0 H z})$. After FFT, it was found that the vibration frequency under $17 \mathrm{~Hz}$ has the greatest influence on the output results.
In this paper we proposed a photodetector using GaN/InGaN-based multi-quantum well micro-LED fabricated on Si-substrate. It yields 12.14 Gb/s data rate in our experiment, which is the highest record for GaN-based micro-PD.
In this work, a hollow-core negative curvature fiber filled with the ethanol and gold wires is proposed for the temperature sensing. It is demonstrated that the average sensitivity of 3 nm/°C can be achieved in the temperature range of −40 ~ 60°C.
We report the design of two polarization-insensitive $1 \times 2$ power dividers on SOI with 220nm top silicon. The multimode interference coupler is within 4 $\mu \mathrm{m} \times 140 \mu \mathrm{m}$. For the type I device, the excess losses for both the TE and TM modes at 1550 nm are $\lt 0.1$ dB. For the type II device, the excess losses for the TE and TM modes are $\lt 0.55$ dB over the C band. We also analyze their performance deteriorations due to ±20 nm fabrication errors in width.
A compact four-mode Si-SiN interlayer coupler with dual polarizations is proposed. The coupler has a low transmission loss of 0.05-0.73 dB and exhibits high fabrication tolerance from 1450 nm to 1650 nm.
A secure OFDM data communication scheme is proposed for wireless or optical networks, where a 200Kbps data transmission integrated with 50Kbps physical-layer key distribution is demonstrated using non-orthogonal multiple access (NOMA).
In nonlinear frequency division multiplexing (NFDM) transmission system with discrete spectrum (DS) modulation, there are two methods to improve the data transmission rate, including the increase of the baud rate, and the number of multiplexed eigenvalues. Although some studies have been made on the DS-NFDM, the characteristic of these two manners have not been analyzed yet. Here, we give some analysis on the DS-NFDM system to improve the performances, including the spectral efficiency, noise robustness and bit-error-rate (BER) under the same data transmission rate. The simulation results show that the single-eigenvalue high baud rate scheme has advantages in spectral efficiency, but it is inferior to the multi-eigenvalue low baud rate one in terms of noise robustness and BER performance.
A micro extrinsic Fabry-Perot air cavity is constructed on the fiber end using two-photon polymerization 3D printer. Experimental measurements show that the temperature sensitivity reaches 0.24 nm/°C in the temperature range of 20°C-60°C.
