Search

With phase-sensitive optical time-domain reflectometry (Φ-OTDR), an optic fiber can be used as a distributed vibration sensor to perceive the external disturbance along the fiber through the phase variation of the Rayleigh backscatter light. However, due to the inevitable interference fading phenomenon, the signal-to-noise ratio (SNR) of Rayleigh backscatter light at certain points is insufficient, thus affecting the fidelity of vibration sensing. In this paper, we propose the spectrum extraction and the rotated-vector-sum (SERVS) method to suppress the interference fading in the pulse-intensity-coding Φ-OTDR, which applies Golay complementary sequence through acousto-optic modulator (AOM). Benefited from the easier implementation, the experimental results demonstrate that the percentage of fading points can be reduced from 2.98% to 0.33% significantly and the standard deviation of differential phase is also decreased from 0.6556 rad to 0.2901 rad. Also the minimum level of averaged power spectral density (PSD) of the differential phase at whole locations along the fiber is reduced about 6 dB/Hz effectively. For the demodulated disturbance signal, no influence on the SNR is observed thus it maintains a SNR improvement of 8.6 dB compared to the traditional single pulse Φ-OTDR system, achieving a noise floor of 2.38 pϵ/√Hz.

A new U-shape panda polarization-maintaining fiber (PPMF) based microfiber interferometer coated with graphene oxide (GO) film was proposed and experimentally demonstrated for relative humidity (RH) sensing. Experimental results show that the U-shape sensor has refractive index (RI) sensitivity of 1692.5 nm/RIU in the RI range of 1.33 when the diameter of the taper waist is 10.08 μm. The surface of the U-shape sensor was then modified chemically and coated with a thin layer of GO film (59.64 nm) for RH detection and the sensitivity is proportional to RH: as RH increases from 30% to 98%, the sensitivity increases from 0.111 to 0.361 nm/%RH and the response time is 0.28 s. In addition, the cross sensitivity to temperature, stability, reproducibility, and response/recovery time of the RH sensor were studied in detail. The proposed U-shape fiber RH sensor has advantage of high sensitivity, good reproducibility and fast response (0.28 s), which has potential application in areas requiring dynamic measurement of RH variations such as industrial product fabrication process control and breath state monitoring.

In this paper, we report the existence of Eckhaus instability in laser cavities with harmonically swept filters, of which Fourier Domain Mode Locked (FDML) laser is an important example. We show that such laser cavities can be modeled by a real Ginzburg Landau equation with a frequency shifting term arisen from the cavity dispersion. We analytically derived a solution of the governing equation and analyzed its stability. We found that the cavity dispersion introduces a continuous frequency shift to the laser signal such that it will be eventually pushed outside the stable region and trigger the Eckhaus instability. We show that the repeated triggering of the Eckhaus instability in the laser cavities is the dominant effect that leads to the high frequency fluctuations in FDML laser output, which is the unique feature of such laser cavities and intrinsically limits the signal quality of the FDML lasers with nonzero cavity dispersion.

Single dissipative Kerr soliton (DKS) formed in microresonator shows few-cycle femtosecond pulses along with smooth and phase-coherent comb spectra that easily reaching an octave spanning. Such unique characteristics lead to revolutionary breakthrough in advanced communications, spectroscopy, metrology, etc. However, as hidden deepest inside the multistable states of driven-damped microresonator, the single DKS state remains challenging to generate deterministically and straightforwardly. Here, we theoretically show that a train of energetic pulse trigger imposed on an external continuous-wave driving pump can quickly kick start the cavity to deterministically evolve into a single DKS state. Neither the pump frequency nor the cavity resonance frequency requires to be scanned, thus possessing the potential for turnkey soliton microcombs generation. The additional degrees of freedom given by the combined pump enables the manipulation of multi-DKS and even perfect soliton crystals generation in the same microresonator. The proposed pulse train triggering method can also be harnessed for ultrahigh speed all-optical clock recovery with a potential rate up to terahertz. Our results open up a new path for manipulating single and multi-DKS in microesonators and a robust optical clock recovery module simultaneously possessing ultrahigh speed, on-chip integration, and cost-efficiency.

In this paper, a polarization beam splitter (PBS) based on the gold wire-filled dual-core photonic crystal fiber is proposed. The full-vector finite element method is used to investigate the influe...

In this paper, we propose a photonic crystal fiber (PCF) refractive index (RI) sensor based on the surface plasmon resonance (SPR) effect. The coupling and sensing characteristics of the proposed P...

In this paper, a polarization-insensitive reverse-ridge AlGaAs waveguide is designed for the supercontinuum generation. In the considered wavelength range from 3.4 to 8 μ m, the dispersion profiles, nonlinear coefficients, and effective mode field areas for the quasi-TE and quasi-TM modes coincide well. The simulation results show that when pump pulse with wavelength of 4.2 μ m, peak power of 4.8 kW, and width of 90 fs is launched into the anomalous dispersion region of the quasi-TE and quasi-TM modes of the 3.4-mm-long waveguide, the two generated SCs overlap well. For the quasi-TE and quasi-TM modes, the SCs generated extend from 2.17 to 8.53 μ m and 2.23 to 8.61 μ m, respectively, spanning more than 1.95 octaves. The proposed reverse-ridge AlGaAs waveguide structure is expected to provide a possible solution for alleviating the undesired polarization effect related to the nonlinear dynamics.

A graphene-coated two-layer dielectric loaded surface plasmon polariton (GTDLSPP) rib waveguide is designed. The mode characteristics and electro-optic (EO) modulation performances of the four hybrid plasmonic modes (HPMs) in the designed waveguide are simulated by using the finite element method. The simulation results show that a 103 mm-scale propagation length and an effective mode field area of ~λ2/1333 are obtained by adjusting the bias voltage. The EO wavelength tunings are -68.6, -42.0, -49.7, and -11.1 nm/V for the HPM 1, HPM 2, HPM 3, and the peak 2 of HPM 4, which are two orders of magnitude larger than those of other EO modulation structures. For the peak 1 of the HPM 4, the EO wavelength tuning is the piecewise linear. For a 150-μm long waveguide, the modulation depths of ~98.7, ~87.9, and 99.5%, and FWHMs of ~450, ~100, and ~42 nm can be achieved for the HPM 1, HPM 2, and HPM 3. For the HPM 4, there are two peaks in the transmission spectrum. The modulation depths are ~97.3 and 75.2%, and FWHMs are ~92 and ~34 nm for the peaks 1 and 2. There is a tradeoff between the modulation depth and FWHM for different waveguide lengths. The GTDLSPP rib waveguide designed has small size, high modulation depth, broad bandwidth, and compatibility with the CMOS technology, soit has potential applications in the EO tunable devices, optical interconnects, and optical switches.

In this paper, passive generation of the multi-wavelength parabolic pulses (PPs) in tapered silicon nanowires (TSNs) is numerically investigated. The coupled inhomogeneous nonlinear Schrödinger equation (INLSE) is derived in the context of TSN to model the multi-wavelength PP generation. The TSN is designed based on the well-known self-similar theory that the group-velocity dispersion is decreased while the nonlinear coefficient is unchanged along the propagative direction. While the pump wavelengths for three input pulses are specially set with equal intervals of 18, 12, and 6 nm, the time-domain profiles are aligned at the same position. Simulation results show that except for wavelength interval, the waveguide length is also a critical factor that influences the quality of generated PP. Both of them reshape the pulse profile by the means of walk-off effect which depends on the cross-phase modulation between multiple pulses. By properly optimizing the input parameters of Gaussian pulses as well as the center wavelength interval and TSN length, we prove that the generation of two- even three-wavelength PPs with high-quality is feasible.

A simple optic-fiber Fabry-Perot (FP) sensing technique was proposed and experimentally investigated by using polymer material to connect the ends of two singlemode fibers. Four different polymer materials (benzocyclobutene (BCB), UV88 (Relentless, China), Loctite3525 (HenKel, Germany), and NOA68 (Norland, USA)) filling the FP cavity were used to comparatively study the sensing performance of temperature, strain and refractive index. The result shows that the FP sensor with BCB has excellent repeatability with good linear response to temperature in a wide range from room temperature to 250 °C, which is much larger than that of other three materials (2)) and the best repeatability among the four polymer materials.

In this paper, a V-shape photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR) effect is proposed. With the full vector finite element method, the V-shape photonic crystal fiber polarization filter is designed, and the coupling characteristics between the core mode and surface plasmon polariton mode are analyzed. The simulation results show that the fiber parameters have significant effects on the shift and strength of the SPR wavelength. Moreover, the losses of the core modes along the Y and X polarization directions are 68904 dB/m and 858 dB/m at the SPR wavelength of 1550 nm, respectively. Finally, the extinction ratio and error-tolerant rate of extinction ratio are also analyzed. The proposed V-shape PCF polarization filter can achieve good filtering effect in the communication band and is easy to integrate with existing optical fiber communication and sensing systems.

In this paper, a joint baud-rate and modulation format identification (BR-MFI) is proposed based on asynchronous delay tap picture (ADTP) analyzer by using convolutional neural network (CNN). Considering 8 types of signals under different channel conditions of OSNR, CD and DGD, the proposed BR-MFI can achieve 100% accuracy after 6 training epochs, and just 2 epochs for MFI. Here, two test number of samples are about 15% of total samples. This paper also investigates the influence of CNN structure on the identification accuracy. The results show that CNN has better performance for image processing than back-propagation Artificial Neural Network (BP-ANN).

In this paper, we numerically investigate the generation of parabolic pulse (PP) in a silicon waveguide taper with simultaneous variations of the group-velocity dispersion and nonlinearity along the propagation direction. The design of such a waveguide taper is based on the condition of self-similar propagation of the PP. When Gaussian, hyperbolic secant, and super-Gaussian pulses are propagated inside the waveguide taper designed, the evolution processes under the ideal condition are analyzed. Then the PP generation from Gaussian input is shown when higher-order dispersion, higher-order nonlinearity, linear loss, two-photon absorption, free-carrier absorption, and free-carrier dispersion are taken into account. Moreover, the influences of the initial chirp, pulse width, peak power, and waveguide length on the PP generation are further discussed. It is demonstrated that high-quality PP can be obtained with a mismatch parameter as low as 1 . 3 × 1 0 − 3 , in the designed silicon waveguide taper.

We propose the two-stage cascaded-tapered silica photonic crystal fiber (PCF) for the supercontinuum (SC) generation. The cascaded-tapered silica PCF is designed to have a spatial periodic structure. The physical scenarios of the spectral broadening due to the interaction between the structure-induced periodic dispersion and Kerr nonlinearity under different pulse widths and peak powers are investigated. It is found that when the pump pulses with width of

In this paper, a reverse-strip AlGaAs waveguide with three zero-dispersion wavelengths (ZDWs) is designed. The corresponding three ZDWs are located at 3.74, 6.56, and 8.89 µm. The nonlinearity coefficient of the proposed reverse-strip AlGaAs waveguide is calculated as 2.09 W − 1 m − 1 at wavelength 4.9 µm. The effects of pump pulse parameters, waveguide length, and noise coefficient on the nonlinear dynamics of supercontinuum (SC) generation are investigated. When the hyperbolic secant pump pulse with a wavelength of 4.9 µm, peak power of 900 W, and duration of 100 fs is launched into the proposed waveguide and propagated after a 3 mm length, highly coherent and multi-octave mid-infrared (MIR) SC spanning from 2.2 to 14.5 µm (more than 2.7 octaves, at − 40 d B level) is generated. Finally, a possible fabrication process of the reverse-strip AlGaAs waveguide is introduced. Our research results have important applications in MIR photonics, MIR spectroscopy, optical precision measurement, and more.

This paper proposes a novel liquid crystal-filled, dual core photonic crystal fiber polarization beam splitter (LC-DC-PCF PBS) based on the coupled mode theory of DC-PCF. The mode birefringence of odd and even modes, coupling lengths (CLs) of the X-polarization (X-pol) and Y-polarization (Y-pol), and the corresponding coupling length ratio (CLR) of the proposed LC-DC-PCF PBS filled without LC E7 and with LC E7 are compared. The change rules of the CLs of the X-pol and Y-pol and CLR of the proposed LC-DC-PCF with wavelengths for different cladding microstructure parameters were investigated. The relationships between the X-pol and Y-pol normalized output powers in core A of the proposed LC-DC-PCF PBS and the propagation length at the wavelength of 1.604 μm are discussed. Finally, by studying the change of extinction ratio (ER) with wavelength, the LC-DC-PCF PBS ER of 60.3 and 72.2 dB at wavelengths 1.386 and 1.619 μm are achieved, respectively. The final splitting length (LS) is 94 μm, and the splitting bandwidth is 349 nm (1.352~1.701 μm), covering the whole of the E + S + C + L + U communication bands. The proposed LC-DC-PCF PBS has good beam-splitting performance, such as ultra-short LS and ultra-wide splitting bandwidth, with potential applications in laser, sensing, and communication systems.

A broadband polarization beam splitter (PBS) based on compressed hexagonal structure and liquid crystal-filled dual-core photonic crystal fiber is proposed. The bandwidth of the proposed PBS is 280 nm, covering the S, C, L, and U communication bands. Besides, it has a short length of 109.5 µm and an extinction ratio of 63 dB at the communication wavelength of 1.55 µm.

A novel photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) effect for a wider range of refractive index (RI) detection is proposed. The sensitivity of the proposed sensor could reach −4851 nm/RI unit (RIU) in the dynamic RI range from 1.25 to 1.49 for the y-pol mode as well as −4523 nm/RIU in the dynamic RI range from 1.25 to 1.45 for the x-pol mode, which makes it has potential application prospects in the chemistry, biology, and environment monitoring.

An ultra-short polarization beam splitter (PBS) based on a dual-core photonic crystal fiber (PCF) with the surface plasmon resonance effect is proposed. The finite-element method is used to investigate the coupling characteristics between the core mode and surface plasmon polariton mode. The influences of the PCF structure parameters on the coupling length and coupling length ratio are also investigated. The normalized output powers of the x-polarization and y-polarization are calculated, and the optimized PBS achieves an ultra-short length of 62.5 μm. The splitting bandwidth of 110 nm (1.51 to 1.61 μm) is achieved when the extinction ratio (ER) is less than −20 dB. The minimum ER reaches −71 dB at the wavelength of 1.55 μm. The proposed PBS has an important application in high-speed optical communication systems.

In this paper, we numerically demonstrate efficient spectral compression (SPC) of wavelength-shifting soliton in a chalcogenide strip waveguide. It is found that the profiles of group-velocity dispersion (GVD) and Kerr nonlinearity play key roles in determining SPC. After calculating the dispersion of Kerr nonlinearity and Raman spectrum for three kinds of chalcogenide materials, Ge11.5As24Se64.5 is chosen as the material for designing the chalcogenide strip waveguide (CSW). The geometric parameters of CSW are optimized to obtain the desired GVD and Kerr nonlinearity. Simulation results show that in the designed CSW, an input spectrum width of 52.04 nm can be compressed to 7.23 nm along with wavelength shift of 17 nm when the input peak power is 25 W. With the input peak power increasing to 75 W, the SPC is slightly weakened, but wavelength shift can be up to 190 nm. The proposed CSW is applied to integrated all-optical quantization and an effective quantization number of 3.66-bit is achieved. It is expected that our research results can find important applications in on-chip integrated spectroscopy, all-optical signal processing, etc.

In this paper, a chalcogenide-based ridge waveguide with a suspended structure on the substrate of Si 3 N 4 , is designed, which is demonstrated to have low and flat dispersion profiles. Simulation results show that when the higher-order nonlinear effects and linear loss are considered, a broadband supercontinuum with high coherence ranging from 1.0 to 5. 6 μ m is obtained after a 3.1-mm long propagation when pumping wavelength 2. 65 μ m and peak power 450 W. Our proposed scheme provides a promising solution to realize broadband and highly coherent SC in mid-infrared region for nonlinear photonics and spectroscopy.

Single channel 100 Gbit/s PAM4 transmission at O band is experimentally studied based on low cost intensity modulation and direct detection (IM-DD). By the use of advanced digital signal processing algorithms, we successfully achieve a receiver sensitivity of −17.3 dBm at 7% HD-FEC threshold of 3.8E-3 over 40 km un-amplified SSMF transmission with 17 GHz (3 dB bandwidth) commercial electric absorption modulated laser (EML) and avalanche photodiode (APD). To the best of author’s knowledge, we hereby report the best receiver sensitivity for 100 Gbit/s/λ IM-DD system. Due to the low cost and high sensitivity merits, the proposed scheme will be a promising way for high speed short-haul optical transmissions in the future.

In this paper, a novel gold film-coated V-shape dual-core photonic crystal fiber (V-DC-PCF) polarization beam splitter (PBS) based on surface plasmon resonance effect is proposed. The coupling lengths of the X-polarization (X-pol) and Y-polarization (Y-pol) and the corresponding coupling length ratio of the proposed V-DC-PCF PBS without gold film and with gold film are compared. The fiber structure parameters and thickness of the gold film are optimized through investigating their effects on the coupling lengths and coupling length ratio. As the propagation length increases, the normalized output powers of the X-pol and Y-pol of the proposed V-DC-PCF PBS at the three wavelengths 1.610, 1.631, and 1.650 &mu, m are demonstrated. The relationships between the extinction ratio (ER), insertion loss (IL) and wavelength for the three splitting lengths (SLs) 188, 185, and 182 &mu, m are investigated. Finally, it is demonstrated that for the proposed V-DC-PCF PBS, the optimal SL is 188 &mu, m, the ILs of the X-pol and Y-pol are less than 0.22 dB, and the splitting bandwidth (SB) can cover the E + S + C + L + U band. The proposed V-DC-PCF PBS has the ultra-short SL, ultra-wide SB, and ultra-low IL, so it is expected to have important applications in the laser, sensing, and dense wavelength division multiplexing systems.

A polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) with three layers of elliptical air holes is proposed. The full-vector finite element method is used to investigate the coupling and propagation characteristics of the PBS, and the three-dimensional beam propagation method is used to demonstrate the evolutions of the x-pol and y-pol light fields in cores A and B of the DC-PCF. In this design, the elliptical air holes are introduced to enhance the birefringence of the DC-PCF. The simulation results show that, with the proposed PBS, the complete beam splitting can be achieved at wavelength 1.55 μm when the fiber length is 254 μm. Moreover, when the extinction ratio is less than −20 dB, the bandwidth of the PBS can be up to 48 nm, covering the whole C-band. It is believed that the proposed PBS will be a promising candidate in laser and sensor systems.

An ethanol and gold wires-filled single-polarization hollow-core negative curvature fiber is proposed for temperature sensing. The average sensitivity and R2 can reach 3.03 nm/ and 0.999 in the temperature range of 20 to 70, respectively.

Based on three typical features, i.e. energy entropy, histogram distribution percentage and zero-crossing rate, we compared the classification accuracy of microseismic events between fiber-optic and electronic monitoring system using support vector machine.

Based on the delayed self-heterodyne scheme, the linewidths of DFB and ECL are measured and analyzed by PSD of optical field, variance of phase difference and FM-noise PSD spectrum. The latter can measure the linewidth produced by white FM-noise. The impact of white noise and flick noise of laser on BER and mismatch length is researched.

An ultra-short and broadband dual-core photonic crystal fiber polarization beam splitter with a gold film based on surface plasmon resonance effect is proposed. The splitter length and bandwidth are 194 μm and 243 nm, respectively.

With hollow-core negative curvature fiber, a refractive index (RI) sensor based on surface plasmon resonance effect is proposed. The average sensitivity can be up to -7024 nm/RIU in the RI range from 1.29 to 1.39.

We demonstrate the high sensitivity fiber index sensors by tapering the four core fibers to produce supermode interference with the best extinction ratio of up to 15 dB and the index sensitivity of 2,884 nm/RIU.

In this paper, a hollow-core negative curvature fiber (HC-NCF) with high birefringence is proposed for low refractive index (RI) sensing based on surface plasmon resonance effect. In the design, the cladding region of the HC-NCF is composed of only one ring of eight silica tubes, and two of them are selectively filled with the gold wires. The influences of the gold wires-filled HC-NCF structure parameters on the propagation characteristic are investigated by the finite element method. Moreover, the sensing performances in the low RI range of 1.20&ndash, 1.34 are evaluated by the traditional confinement loss method and novel birefringence analysis method, respectively. The simulation results show that for the confinement loss method, the obtained maximum sensitivity, resolution, and figure of merit of the gold wires-filled HC-NCF-based sensor are &minus, 5700 nm/RIU, 2.63 &times, 10&minus, 5 RIU, and 317 RIU&minus, 1, respectively. For the birefringence analysis method, the obtained maximum sensitivity, resolution, and birefringence of the gold wires-filled HC-NCF-based sensor are &minus, 6100 nm/RIU, 2.56 &times, 5 RIU, and 1.72 &times, 3, respectively. It is believed that the proposed gold wires-filled HC-NCF-based low RI sensor has important applications in the fields of biochemistry and medicine.

Large viewing angle, dense viewpoints, high-resolution 3D light field display technology can achieve large viewing angle, high resolution, and high dynamic reconstruction of the objective world scene light field, which is an important direction for the development of future display technology. The application of advanced 3D light field display technology is getting more and more attention. However, the current lack of efficient access to large viewing angles, dense viewpoints, and high-resolution 3D light field content limits its development and application. To this end, here proposes a dense viewpoints video generation, coding, transmission method, and build a super multi-view 3D light field video live broadcast system. The method and system are composed of 3D light field video generation, light field video coding, light field video transmission and a display part. It can provide viewers with a real-time, high-quality 3D visual experience.

An ultra-high sensitivity label-free optical fiber biosensor for inactivated Staphylococcus aureus (S. aureus) detection is proposed and investigated in this study, with additional advantages of robust and stability compared to traditional tapered fiber structure. The proposed fiber biosensor is based on a tapered singlemode- no core-singlemode fiber coupler (SNSFC) structure, where the no core fiber was tapered to small diameter (taper-waist diameter of about 10 μm) and functionalized with the pig immunoglobulin G (IgG) antibody for detection of S. aureus. The measured maximum wavelength shift of the sensor for an S. aureus concentration of 7 × 101 CFU/mL (colony forming unit per milliliter) is 2.04 nm, which is equivalent to a limit of detection (LOD) of 3.1 CFU/mL (a highest LOD reported so far for optical fiber biosensors), considering the maximum wavelength variation of the sensor in phosphate buffered saline (PBS) is ±0.03 nm over 40 min, where 3 times of maximum wavelength variation (3 × 0.03 = 0.09 nm) is defined as measurement limit. The response time of the developed fiber sensor is less than 30 min. The ultra-sensitive biosensor has potential to be widely applied to various areas such as disease, medical diagnostics and food safety inspection.

In this paper, a T-type germanium (Ge) waveguide with an all-normal dispersion profile is designed for mid-infrared (MIR) supercontinuum (SC) and frequency comb generations. The nonlinearity coefficient of the designed waveguide is calculated as 30.48 W-1·m-1 at the initial pump wavelength of 3.0 µm. Moreover, the group-velocity dispersion is kept low and flat in the considered wavelength range. Simulation results show that with the designed waveguide, the highly coherent and octave-spanning MIR SC can be generated in the wavelength range from 1.85 to 9.98 µm (more than 2.4 octaves) when the pump pulse with wavelength of 3.0 µm, peak power of 900 W, and duration of 120 fs is launched into the 5 mm long waveguide. When the pulse train including 50 pulses at a repetition rate of 100 MHz is used as the pump source, the SC-based frequency comb is obtained.

We report a simple refractive index (RI) sensor based on a twin-hole fiber (THF). The THF is fused with the single-mode fiber to realize sensing by the multimode interference. The mode transmission characteristics in the THF are numerically investigated. In the sensing experiment, when the surrounding RI changes, the wavelength shift of the transmission spectrum shows approximate linearity in the low RI region and nonlinearity in the high RI region. When a THF with the length of 10 mm is used, the highest sensitivity can be up to 1351 nm / RIU in the RI range from 1.430 to 1.445. Moreover, the effect of the temperature on the transmission spectrum relative to the RI is much smaller when the external temperature changes from 30°C to 80°C.

A novel microfiber sensor is proposed and demonstrated based on a singlemode-tapered hollow core-singlemode (STHS) fiber structure. Experimentally a STHS with taper waist diameter of $26.5~\mu \text{m}$ has been fabricated and RI sensitivity of 816, 1601.86, and 4775.5 nm/RIU has been achieved with RI ranges from 1.3335 to 1.3395, from 1.369 to 1.378, and from 1.409 to 1.4175 respectively, which agrees very well with simulated RI sensitivity of 885, 1517, and 4540 nm/RIU at RI ranges from 1.3335 to 1.337, from 1.37 to 1.374, and from 1.41 to 1.414. The taper waist diameter has impact on both temperature and strain sensitivity of the sensor structure: (1) the smaller the waist diameter, the higher the temperature sensitivity, and experimentally 26.82 pm/°C has been achieved with a taper waist diameter of $21.4~\mu \text{m}$ ; (2) as waist diameter decrease, strain sensitivity increase and 7.62 pm/ $\mu \varepsilon $ has been achieved with a taper waist diameter of $20.3~\mu \text{m}$ . The developed sensor was then functionalized for human chorionic gonadotropin (hCG) detection as an example for biosensing application. Experimentally for hCG concentration of 5 mIU/ml, the sensor has 0.5 nm wavelength shift, equivalent to limit of detection (LOD) of 0.6 mIU/ml by defining 3 times of the wavelength variation (0.06 nm) as measurement limit. The biosensor demonstrated relatively good reproducibility and specificity, which has potential for real medical diagnostics and other applications.

In this paper, a novel silicon photonic crystal fiber (Si-PCF) polarization filter based on surface plasmon resonance effect is proposed for the first time. With the full-vector finite-element method, the mode coupling characteristics of the Si-PCF with the gold-coated film between the core mode and surface plasmon polariton mode are investigated, and the confinement losses are analyzed. The confinement losses of the Y-polarized core mode at the three resonant wavelengths 2.84, 3.29, and 4. 53 μ m are 9235.9, 27097.5, and 97818.3 dB/m, respectively. The extinction ratio reaches -391 dB and the insertion loss is less than 1 dB when the Si-PCF length is 4 mm, along with the filter bandwidth of 2. 75 μ m . Moreover, by modifying the fiber structure parameters, the filter bandwidth of the proposed three kinds of Si-PCF polarization filters can cover 2.75 to 7. 80 μ m . It is believed that the proposed Si-PCF polarization filter has important applications in the mid-infrared laser and optical communication systems.

A method for adjusting the differential order of a silicon-based waveguide grating differentiator by inputting light, which is through two-photon absorption and free carrier absorption effects, is proposed. The simulation results are demonstrated.

We design a dual-core photonic crystal fiber (PCF) polarization beam splitter (PBS) based on surface plasmons resonance effect. The maximum extinction ratio of the PBS can be up to -160.56 dB at wavelength 1.55 μm.

We propose and demonstrate a directional bend sensing based on Mach-Zehnder interferometer in a high birefringence dual-core photonic crystal fiber. Its curvature sensitivity is up to 4.24 nm/m–1 within the curvature range of 2.19-3.99 m–1.

A pre-configured Kramers-Kronig (Pre-KK) scheme is proposed for single sideband (SSB) systems and demonstrated that a better performance can be achieved than traditional KK scheme because of reducing the requirement of DAC and ADC resolution.

A nematic liquid crystal-filled dual-core photonic crystal fiber single-polarization wavelength splitter is proposed. The length of the splitter is 2.38 mm, and the crosstalk between the wavelengths 1.31 and 1.55 μm can achieve -68.18 dB.

An ultra-broadband silicon dual-core photonic crystal fiber polarization beam splitter at mid-infrared spectral region based on surface plasmon resonance is proposed. The bandwidths of the cores A and B are 730 and 580 nm, respectively. © 2020 The Author(s).

We experimentally demonstrate coherent comb generation in a 5-mm long all-normaldispersion AlGaAs-on-sapphire waveguide with a 47% pump-to-comb conversion efficiency. We achieve a 20-dB bandwidth of 24.5 THz covering from the S- to U-band wavelength ranges.

The traditional control flow integrity usually takes dynamic control transfer as the measurement object. And it means that the attacker can subvert software by modifying the obvious victim. To overcome it, a novel concept, called as control flow invariant, is presented in this paper. Control structure invariant is a certain law followed by software run. Not limited to dynamic control transfer, control structure invariant have more forms, thus supporting more types of control flow integrity measure. In order to find more control structure invariant, we proposes to use hardware to capture the trace information of software running, and analyze it to mine the control structure invariant. We give a case study that a system on Intel PMC is introduced to show the reasonableness of our solution.

A critical barrier for the successful development of fiber sensors for bio-chemical processes is their limitedly improved sensitivity, restricted by the sensor structural design. To solve this, in this paper, a novel concept was proposed using functionalised modified magnetic microspheres (MMSs) to "amplify" the effect of target bio-chemical analytes to significantly improve the fiber sensor's sensitivity, which has been demonstrated using human chorionic gonadotropin (hCG) as an example. Two types of antibody hCG, (β and α, both can specifically bind with hCG), were adhered on the surface of fibre sensor and MMSs respectively. Both hCG and MMSs will be specifically captured by the fibre sensor, where MMSs act as an "amplifier" to improve the sensor sensitivity. Experimentally immunomagnetic detection limit of 0.0001 mIU/mL has been achieved, which is the highest reported so far. This newly developed methodology opens a new direction for sensitivity improvement and could be further explored to applications require ultrahigh sensitivity detections such as earlier medical diagnostics.