Enhanced optoelectronic reservoir computation using semiconductor laser with double delay feedbacks.

We numerically explored the enhanced performance and physical mechanism of semiconductor laser (SL) based reservoir computation (RC) with double optoelectronic feedback (DOEF). One-step and multistep Santa Fe time series predictions were used as standard test benchmarks in this work. We found that in the optimized parameter region the normalized mean square error (NMSE) of an SL-based RC under DOEF is smaller than an SL-based RC with single optoelectronic feedback (SOEF). In addition, the performance improvement is more obvious for multistep prediction, which is particularly suitable for more complex tasks that requires a higher memory capability (MC). The enriched node states (optical intensity of the virtual nodes for each sample) and the enhanced MC of the proposed DOEF were verified by a comparison to SOEF under the optimized feedback strength. The influence of the feedback strength and the delay difference on the NMSE and the MC was also investigated. Our study should be helpful in the design of a high-performance optoelectronic RC based on an SL.

Towards fast sensing along ultralong BOTDA: flatness enhancement by utilizing injection-locked dual-bandwidth probe wave.

Brillouin optical time-domain analysis (BOTDA) using distributed Brillouin amplification (DBA) only requires a milliwatt-level pump to achieve a sensing range beyond 100 km, which provides a powerful tool for temperature/strain sensing. However, similar to the majority of other long-range BOTDAs, the state-of-the-art reports require > 1000 times average, severely restricting the sensing speed. The blind area over tens of kilometers caused by the nonuniform Brillouin response and parasitic amplitude modulation (AM) are crucial factors affecting the signal-to-noise ratio (SNR). Here, a comprehensive performance optimization and substantial enhancement for BOTDA sensors was presented by the direct demodulation of an injection-locked dual-bandwidth probe wave. Injection locking (IL) can completely eliminate the impact of AM noise; dual-bandwidth probe enables self-adaptive pulse loss compensation, thereby intensifying the SNR flatness along the ultralong fiber, and direct probe demodulation can overcome nonlocal effects and allows ∼19.7 dB enhancement of probe input power. Therefore, using only 100 times average, ∼148.3 km sensing, and ∼5 m spatial resolution were achieved with < ∼0.8 MHz standard deviation of Brillouin frequency shift (BFS) over a broad range (∼131.7 km). The reduction in averages was more than 10 times that of the reported majority of long-range BOTDAs. Such performances were achieved without using time-consuming or post-processing techniques, such as optical pulse coding and image denoising. Because this approach is compatible with optical chirp chain technique without frequency sweeping, fast acquisition (0.3 s) was also realized, which has the potential for fast sensing at 3.3 Hz along a ∼150 km fiber.

Clinical Study of the Treatment of Klebsiella pneumoniae with Comprehensive Nursing Intervention Combined with New Nano Silver.

To investigate the inhibitory effect of new nano silver (nAg-NPs) on Klebsiella pneumoniae producing extended spectrum ß-lactamases (EBLs). Clinical interventions are mainly directed to inpatients, or patients with obvious discomfort, symptoms, and signs needing outpatient examination, referral, and clear diagnosis. We randomly selected 88 patients from the rehabilitation department of our hospital from November 2017 to June 2019, and divided them into observation and control groups by drawing lots. Taking ESBL K. pneumoniae as the research object, the bactericidal effect of nAg-NPs was determined using the coating method; the minimal inhibitory concentration (MIC) was measured using the broth microdilution method, and the mechanism of action of nAg-NPs on ESBL K. pneumoniae was evaluated by electron microscopy. After the implementation of different nursing management modes, the incidence of risk events in the observation group was significantly lower than that in the control group, and nursing satisfaction was significantly higher than that in the control group. nAg-NPs (≥0.5 g/mL) had 100% bactericidal effect on ESBL K. pneumoniae, 0.05 g/mL nAg-NPs had obvious bactericidal effect on ESBL K. pneumoniae, 5 g/mL nAg-NPs had obvious bactericidal effect on ESBL K. pneumoniae for 5, 15, 30 and 60 min. Additionally, nAg-NPs showed 3.12 g/mL of MIC. Furthermore, nAg-NPs had a significant effect on the morphology of K. pneumoniae. nAg-NPs shows obvious inhibitory effect on ESBL K. pneumoniae. These results will provide an experimental basis for the further study and clinical application of nAg-NPs with the help of clinical nurses.

Noise level estimation of BOTDA for optimal non-local means denoising.

Due to the similarity of Brillouin optical time domain analyzer (BOTDA) signals, image denoising could be utilized to remove the noise. However, the performance can be much degraded due to inaccurate noise level estimation. By numerical and experimental study, we compare the noise level estimation of three different methods for BOTDA: calculating the standard deviation (STD) of the measurements, a filter-based estimation algorithm, and a patch-based estimation algorithm proposed in this paper, which selects weak textured patches of BOTDA signal and then estimates noise level using principal component analysis (W-PCA). The results show that W-PCA and the mean of STD can accurately estimate the noise level, while the filter-based method overestimates the noise level. Nevertheless, for BOTDA with distributed amplification, the STD has huge fluctuation along the length, while the W-PCA is relatively robust for its global consideration. Experimental results of an ultra-long-distance BOTDA prove that the non-local means denoising processing based on W-PCA effectively removes the noise of a sensing system without signal distortion.

Frequency-comb-based BOTDA sensors for high-spatial-resolution/long-distance sensing.

Frequency-comb-based Brillouin optical time-domain analysis (BOTDA) sensors were developed to achieve acquisition-time reduction and high-spatial-resolution/long-distance sensing simultaneously. We found that, for the standard frequency-comb-based BOTDA, the use of a double-sideband (DSB) pulse generates a series of pulse pairs that simultaneously propagate along the sensing fiber, leading to a nonlinear interaction between the two sidebands of each frequency comb pulse, and a significant splitting of the Brillouin gain spectrum (BGS). This problem prevents its application in high-spatial-resolution sensing due to the higher pulse power requirement. Thus, one of the sidebands of DSB pulse was proposed for greatly suppressing the BGS distortion. In combination with the phonon pre-excitation technique based on phase-shifted pulse, a sensor with a spatial-resolution approximately 60 cm along a fiber approximately 592 m in length was demonstrated. Furthermore, we explored the detailed performance of long-distance sensing by frequency- comb-based BOTDA. The use of a frequency comb for the probe wave can suppress the pulse distortion and non-local effect, which is helpful for extending the sensing distance. A spatial resolution of approximately 6 m along a sensing fiber approximately 74.2 km in length was successfully demonstrated.

BOTDA sensors enhanced using high-efficiency second-order distributed Brillouin amplification.

A novel approach for long-distance sensing through Brillouin optical time-domain analysis (BOTDA) assisted by second-order distributed Brillouin amplification (DBA) was proposed and experimentally demonstrated. To the best of our knowledge, this is the first BOTDA study that used second-order DBA. Compared with BOTDA assisted by first-order DBA, the proposed approach enhanced the signal-to-noise ratio of the Brillouin trace by ~3 dB for a range featuring minimum sensing intensity. Long-distance sensing with ~5 m spatial resolution and ± 1.6°C measurement uncertainty over ~99 km fiber was successfully realized by employing high-efficiency pumping using ~6 dBm second-order and ~1.5 dBm first-order pumps.

Syndrome Differentiation Analysis on Mars500 Data of Traditional Chinese Medicine.

Mars500 study was a psychological and physiological isolation experiment conducted by Russia, the European Space Agency, and China, in preparation for an unspecified future manned spaceflight to the planet Mars. Its intention was to yield valuable psychological and medical data on the effects of the planned long-term deep space mission. In this paper, we present data mining methods to mine medical data collected from the crew consisting of six spaceman volunteers. The synthesis of the four diagnostic methods of TCM, inspection, listening, inquiry, and palpation, is used in our syndrome differentiation. We adopt statistics method to describe the syndrome factor regular pattern of spaceman volunteers. Hybrid optimization based multilabel (HOML) is used as feature selection method and multilabel k-nearest neighbors (ML-KNN) is applied. According to the syndrome factor statistical result, we find that qi deficiency is a base syndrome pattern throughout the entire experiment process and, at the same time, there are different associated syndromes such as liver depression, spleen deficiency, dampness stagnancy, and yin deficiency, due to differences of individual situation. With feature selection, we screen out ten key factors which are essential to syndrome differentiation in TCM. The average precision of multilabel classification model reaches 80%.

Analysis of all-optical temporal integrator employing phased-shifted DFB-SOA.

All-optical temporal integrator using phase-shifted distributed-feedback semiconductor optical amplifier (DFB-SOA) is investigated. The influences of system parameters on its energy transmittance and integration error are explored in detail. The numerical analysis shows that, enhanced energy transmittance and integration time window can be simultaneously achieved by increased injected current in the vicinity of lasing threshold. We find that the range of input pulse-width with lower integration error is highly sensitive to the injected optical power, due to gain saturation and induced detuning deviation mechanism. The initial frequency detuning should also be carefully chosen to suppress the integration deviation with ideal waveform output.

[94 km Brillouin distributed optical fiber sensors based on ultra-long fiber ring laser pumping].

A novel optical amplification configuration based on ultra-long fiber laser with a ring cavity was proposed and applied to Brillouin optical time-domain analysis (BOTDA) sensing system, in order to extend the measurement distance significantly. The parameters used in the experiment were optimized, considering the main limitations of the setup, such as depletion, self-phase modulation (SPM) and pump-signal relative intensity noise (RIN) transfer. Through analyzing Brillouin gain spectrum, we demonstrated distributed sensing over 94 km of standard single-mode fiber with 3 meter spatial resolution and strain/temperature accuracy of 28 /1. 4 degree C.

Ultra-long high-sensitivity Φ-OTDR for high spatial resolution intrusion detection of pipelines.

An ultra-long phase-sensitive optical time domain reflectometry (Φ-OTDR) that can achieve high-sensitivity intrusion detection over 131.5km fiber with high spatial resolution of 8m is presented, which is the longest Φ-OTDR reported to date, to the best of our knowledge. It is found that the combination of distributed Raman amplification with heterodyne detection can extend the sensing distance and enhances the sensitivity substantially, leading to the realization of ultra-long Φ-OTDR with high sensitivity and spatial resolution. Furthermore, the feasibility of applying such an ultra-long Φ-OTDR to pipeline security monitoring is demonstrated and the features of intrusion signal can be extracted with improved SNR by using the wavelet detrending/denoising method proposed.

Distributed Raman amplification using ultra-long fiber laser with a ring cavity: characteristics and sensing application.

Distributed Raman amplification (DRA) based on ultra-long fiber laser (UL-FL) pumping with a ring cavity is promising for repeaterless transmission and sensing. In this work, the characteristics (including gain, nonlinear impairment and noise figure) for forward and backward pumping of the ring-cavity based DRA scheme are fully investigated. Furthermore, as a typical application of the proposed configuration, ultra-long-distance distributed sensing with Brillouin optical time-domain analysis (BOTDA) over 142.2 km fiber with 5m spatial resolution and ± 1.5 °C temperature uncertainty is achieved, without any repeater. The key point for the significant performance improvement is the system could offer both of uniform gain distribution and considerably suppressed pump-probe relative intensity noise (RIN) transfer, by optimized design of system structure and parameters.

Third-order random lasing via Raman gain and Rayleigh feedback within a half-open cavity.

Third-order random lasing operating in 1670 nm spectral band is experimentally demonstrated for the first time to the best of our knowledge, with only 2.45 W pump threshold. The lasing cavity is formed by G.652 fiber and fiber loop mirrors (FLMs), while the former acts as the distributed reflector and the latter acts as the point reflector. The G.652 fiber and the FLMs are connected via a multi-band wavelength-division-multiplexer, which ensures each of the three Raman Stokes components generated in the long fiber is routed to one FLM and then reflected back with minimum loss. Unlike existing half-open random lasing cavities using fiber Bragg gratings, the reflection bandwidth of FLMs is wide enough to preserve the intrinsic spectral features of each lasing bands, providing a valuable platform to study the mechanism of high-order random lasing in fibers. Also, the reflection efficiency can be treated as an invariant as the pump power grows, significantly reducing the threshold of high-order random lasing. The stationary model is used to calculate the output power, and the results fit the experimental data well.

Hybrid distributed Raman amplification combining random fiber laser based 2nd-order and low-noise LD based 1st-order pumping.

A configuration of hybrid distributed Raman amplification (H-DRA), that is formed by incorporating a random fiber laser (RFL) based 2nd-order pump and a low-noise laser-diode (LD) based 1st-order pump, is proposed in this paper. In comparison to conventional bi-directional 1st-order DRA, the effective noise figure (ENF) is found to be lower by amount of 0 to 4 dB due to the RFL-based 2nd-order pump, depending on the on-off gain, while the low-noise 1st-order Raman pump is used for compensating the worsened signal-to-noise ratio (SNR) in the vicinity towards the far end of the fiber and avoiding the potential nonlinear impact induced by excess injection of pump power and suppressing the pump-signal relative intensity noise (RIN) transfer. As a result, the gain distribution can be optimized along ultra-long fiber link, due to combination of the 2nd-order RFL and low-noise 1st-order pumping, making the transmission distance be extended significantly. We utilized such a configuration to achieve ultra-long-distance distributed sensing based on Brillouin optical time-domain analysis (BOTDA). A repeater-less sensing distance record of up to 154.4 km with 5 m spatial resolution and ~ ± 1.4 °C temperature uncertainty is successfully demonstrated.

Random-lasing-based distributed fiber-optic amplification.

The gain and noise characteristics of distributed Raman amplification (DRA) based on random fiber laser (RFL) (including forward and backward random laser pumping) have been experimentally investigated through comparison with conventional bi-directional 1st-order and 2nd-order pumping. The results show that, the forward random laser pumping exhibits larger averaged gain and gain fluctuation while the backward random laser pumping has lower averaged gain and nonlinear impairment under the same signal input power and on-off gain. The effective noise figure (ENF) of the forward random laser pumping is lower than that of the bi-directional 1st-order pumping by ~2.3 dB, and lower than that of bi-directional 2nd-order pumping by ~1.3 dB at transparency transmission, respectively. The results also show that the spectra and power of RFL are uniquely insensitive to environmental temperature variation, unlike all the other lasers. Therefore, random-lasing-based distributed fiber-optic amplification could offer low-noise and stable DRA for long-distance transmission.

Propagation of an Airy beam through the atmosphere.

In this paper, the effect of thermal blooming of an Airy beam propagating through the atmosphere is examined, and the effect of atmospheric turbulence is not considered. The changes of the intensity distribution, the centroid position and the mean-squared beam width of an Airy beam propagating through the atmosphere are studied by using the four-dimensional (4D) computer code of the time-dependent propagation of Airy beams through the atmosphere. It is shown that an Airy beam can't retain its shape and the structure when the Airy beam propagates through the atmosphere due to thermal blooming except for the short propagation distance, or the short time, or the low beam power. The thermal blooming results in a central dip of the center lobe, and causes the center lobe to spread and decrease. In contrast with the center lobe, the side lobes are less affected by thermal blooming, such that the intensity maximum of the side lobe may be larger than that of the center lobe. However, the cross wind can reduce the effect of thermal blooming. When there exists the cross wind velocity vx in x direction, the dependence of centroid position in x direction on vx is not monotonic, and there exists a minimum, but the centroid position in y direction is nearly independent of vx.

Analysis of bistable steady characteristics and dynamic stability of linearly tapered nonlinear Bragg gratings.

Based on the nonlinearly coupled mode equations (NLCME), the bistable steady characteristics and dynamic stability of linearly tapered nonlinear Bragg grating (LT-NLBG) have been investigated in detail. The results show that, when the device is tuned near an edge of "photonic band gap" (PBG), in contrast with the free-tapered grating, the negative-tapered grating enhances the switching-on threshold, but increases the on-off switching ratio, enlarges the stable regime, and strengthens the stability significantly. On the other hand, the positive-tapered grating decreases the switching-on threshold, but lower the on-off switching ratio, and worsen the stability remarkably.