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Nonlinear data distortion effect caused by nonlinear transfer function of communication component devices is one critical limitation factor of using high order modulation formats in short-reach optical fiber communications. In order to mitigate the nonlinear distortion effect with memory, indirect learning architecture based digital pre-distorter (ILA-DPD) algorithm has been widely applied for computing a Volterra filter based DPD (Volterra-DPD), which is used as a pre-inverse of nonlinear distortion effect. Given the potential prospect of self-homodyne detection (SHD) for shorter reach optical communications, in this paper, we study the effectiveness of ILA-DPD for a SHD system based on high order quadrature amplitude modulation (QAM) format with different input signal powers of modulator by varying output voltage amplitudes of arbitrary waveform generator (AWG). The principle of ILA-DPD algorithm is shown from Volterra series theory. In our work, an arcsin function based DPD (arcsin-DPD) which is proposed for addressing nonlinear transfer function of Mach-Zehnder modulator is considered in ILA-DPD algorithm and performed together with computed Volterra-DPD. The performance of considered DPD scheme is evaluated in a proof-of-concept 25 Gbaud dual polarization 64QAM SHD system with back-to-back (BtB) and 10 km transmissions. Experiment results show that the considered DPD scheme could significantly improve the transmission performance compared with using arcsin-DPD and achieve a better performance than by using a Volterra-DPD alone for relatively higher output voltage amplitude of AWG.

Amphiphilic nanosheets have gained great attraction in diverse applications owing to their unprecedented performance. In this paper, amphiphilic molybdenum disulfide (CTAB–MoS2) nanosheets were prepared through a one-step simple hydrothermal method, and the physicochemical properties were systematically investigated. The results showed that the CTAB–MoS2nanosheets displayed a distinct ultrathin flakelike structure and a lateral size in the range of 95 nm. More specifically, the presence of defect sites over the surfaces of MoS2nanosheets facilitated linkage with CTAB molecules, which made MoS2amphiphilic. Because of the amphiphilic nature, the CTAB–MoS2nanosheets could be steadily dispersed in water phase, reduce the oil–water interfacial tension, alter wettability of the solid surface, and stabilize emulsions at ultralow concentrations (50 mg/L). By observing and analyzing the interfacial behavior of CTAB–MoS2nanosheets in a simulated oil/brine system, it was found that CTAB–MoS2nanosheets could be adsorbed at the oil–water interface in the form of multilayer adsorption, and the adsorption layer (oil–water interfacial film) exhibited higher strength elasticity. This work provides a scalable method for preparing amphiphilic nanosheets and reveals the physicochemical properties of CTAB–MoS2amphiphilic nanosheets.

To analyze the cost-effectiveness of prostate cancer screening among Chinese men.

Low-power radio frequency (RF) signal detection is highly desirable for many applications, ranging from wireless communication to radar systems. A tunable optoelectronic oscillator (OEO) based on a phase-shifted fiber Bragg grating for detecting low-power RF signals is proposed and experimentally demonstrated. When the frequency of the input RF signal is matched with the potential oscillation mode of the OEO, it is detected and amplified. The frequency of the RF signal under detection can be estimated simultaneously by scanning the wavelength of the laser source. The RF signals from 1.5 to 5 GHz as low as −91  dBm are detected with a gain of about 10 dB, and the frequency is estimated with an error of ±100  MHz. The performance of the OEO system for detecting an RF signal with different modulation rates is also investigated.

The polymer waveguide optical biosensor based on the Mach-Zehnder interferometer (MZI) by using spectral splitting effect is investigated. The MZI based biosensor has two unequal width sensing arms. With the different mode dispersion responses of the two-arm waveguides to the cladding refractive index change, the spectral splitting effect of the output interference spectrum is obtained, inducing a very high sensitivity. The influence of the different mode dispersions between the two-arm waveguides on the spectral splitting characteristic is analyzed. By choosing different lengths of the two unequal width sensing arms, the initial dip wavelength of the interference spectrum and the spectral splitting range can be controlled flexibly. The polymer waveguide optical biosensor is designed, and its sensing property is analyzed. The results show that the sensitivity of the polymer waveguide optical biosensor by using spectral splitting effect is as high as 104nm/RIU, with an improvement of 2–3 orders of magnitude compared with the slot waveguide based microring biosensor.

A 2×2 optical waveguide coupler at 850 nm based on the multimode interference (MMI) structure with the polysilsesquioxanes liquid series (PSQ-Ls) polymer material and the imprint technique is presented. The influence of the structural parameters, such as the single mode condition, the waveguide spacing of input/output ports, and the width and length of the multimode waveguide, on the optical splitting performance including the excess loss and the uniformity is simulated by the beam propagation method. By inserting a taper section of isosceles trapezoid between the single mode and multimode waveguides, the optimized structural parameters for low excess loss and high uniformity are obtained with the excess loss of‒0.040 dB and the uniformity of‒0.007 dB. The effect of the structure deviations induced during the imprint process on the optical splitting performance at different residual layer thicknesses is also investigated. The analysis results provide useful instructions for the waveguide device fabrication.