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1.
Opt Express ; 32(9): 15166-15176, 2024 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-38859175

RESUMO

The refractive index (RI) measurment of the liquid often changes with the sensor's temperature. Accurate RI measurements require simultaneous measurements of the liquid temperature to calibrate the RI measurement. This study proposed what we believe to be a novel dual D-shaped plastic optical fiber sensor capable of simultaneously measuring both RI and temperature. A fluorescent material made of rhodamine B (RhB) is embedded in one of the D-shaped structures of the dual D-shaped fiber, which can be excited by a green laser to produce orange fluorescence. The fluorescence and the input laser of the fiber are superimposed at the output end of the fiber to form a specklegram containing information of two wavelengths. It was found through experiments that the effects of temperature and RI change on the red and green channels of the specklegrams are different, and the neural network can learn this feature to complete the measurement of both RI and temperature parameters. For RI sensing, the maximum error between the average predicted value and the true value of the test set is 0.0005. For temperature sensing, the maximum error between the average predicted value and the true value of the test set is 0.26°C. In addition, because the intensity change of the fluorescence varies linearly with RI and temperature, the sensor also has good stability.

2.
Opt Express ; 32(11): 18550-18561, 2024 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-38859008

RESUMO

As a stochastic perturbation, the inter-core crosstalk (IC-XT) severely distorts the signal in multi-core fibers (MCF), especially for long-haul transmission. How to quickly measure and monitor the IC-XT online for an MCF-based space division multiplexing (SDM) system is of special importance. In this paper, we introduce the technology of auxiliary management and control channel (AMCC) to online monitor the IC-XT of MCF, in which the unique advantage of low-frequency auxiliary management and control signal is fully utilized with the limited influence on high-speed data transmission. Specifically, two orthogonal sequences are chosen as monitoring signals for the signal-channel core and the crosstalk-channel core, respectively, followed by digital signal processing (DSP) for the received signal to evaluate the real-time crosstalk accurately. The experimental verifications of XT online monitoring confirm the effectiveness of our proposed method with very small monitoring error (mostly < 0.5 dB) for both heterodyne XT and homodyne XT in the C and L bands, showing its great potential for future SDM systems.

3.
Opt Express ; 31(12): 19065-19075, 2023 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-37381331

RESUMO

The inter-core crosstalk (IC-XT) of multi-core fiber (MCF) limits the capacity of space division multiplexing system (SDM) fundamentally. We develop a closed-form expression of the magnitude of IC-XT for various types of signals, which can well explain the mechanism of different fluctuation behaviors of the real-time short-term average crosstalk (STAXT) and bit error ratio (BER) for the optical signals with and without strong optical carrier. The experimental verifications with the real-time measurement of the BER and outage probability in a 7 × 10-Gb/s SDM system agree well with the proposed theory and confirm that the unmodulated optical carrier plays a substantial role in fluctuation of BER. The range of fluctuation can be reduced by 3 orders of magnitude for the optical signal without optical carrier. We also investigate the effect of IC-XT in a long-haul transmission system based on a recirculating 7-core fiber loop and develop a frequency-domain IC-XT measurement technique. Longer transmission distance is shown to have a narrower BER fluctuation range, since IC-XT is no longer the only dominant factor on transmission performance.

4.
Opt Express ; 31(13): 20919-20929, 2023 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-37381204

RESUMO

Multi-core fiber based on space division multiplexing technology provides a practical solution to achieve multi-channel and high-capacity signal transmission. However, long-distance and error-free transmission remains challenging due to the presence of inter-core crosstalk within the multi-core fiber. Here, we propose and prepare a novel trapezoid-index thirteen-core single-mode fiber to solve the problems that MCF has large inter-core crosstalk and the transmission capacity of single-mode fiber approaches the upper limit. The optical properties of thirteen-core single-mode fiber are measured and characterized by experimental setups. The inter-core crosstalk of the thirteen-core single-mode fiber is less than -62.50 dB/km at 1550 nm. At the same time, each core can transmit signals at a data rate of 10 Gb/s and achieve error-free signal transmission. The prepared optical fiber with a trapezoid-index core provides a new and feasible solution for reducing inter-core crosstalk, which can be loaded into current communication systems and applied in large data centers.

5.
Opt Express ; 31(9): 15214-15226, 2023 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-37157368

RESUMO

A graded-index 13-core 5-LP mode fiber with high doped core and stairway-index trench structure have been successfully prepared by Hole-drilling method and Plasma vapor deposition. This fiber has 104 spatial channels, realizing large capacity information transmission. By building an experimental platform, the 13-core 5-LP mode fiber have been tested and characterized. The core can stably transmit 5 LP modes. The transmission loss is lower than 0.5 dB/km. Inter-core crosstalk (ICXT) of each layer of core is analyzed in detail. The ICXT can be less than -30 dB/100 km. The test results show that this fiber can stably transmit 5 LP modes, and has the characteristics of low loss and low crosstalk, realizing large capacity transmission. This fiber provides a solution to the issue of limited fiber capacity.

6.
Appl Opt ; 62(34): 8978-8986, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-38108732

RESUMO

Multiple-input multiple-output (MIMO) detectors have been a key technology in communication systems. In this paper, a new MIMO detector is designed by combining the adaptive learning rate (ALR) with the convolutional neural network (CNN) and successfully implementing it in a mode division multiplexing (MDM) optical transmission system. The results show that the training and test accuracy of the signal in the system we proposed reaches 100%. What is more, we used the ALR-CNN to compare the performance with conventional detection algorithms. The results confirm that our DLNN exceeds the conventional MIMO detectors in performance and is able to achieve the ideal QPSK BER level. The minimum difference in the SNR is about 9.5 dB at a BER of the 10-3 order.

7.
Skin Res Technol ; 29(4): e13308, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37113098

RESUMO

BACKGROUND: Post-occlusive reactive hyperemia (PORH) test with signal spectral analysis coupled provides potential indicators for the assessment of microvascular functions. OBJECTIVE: The objective of this study is to investigate the variations of skin blood flow and temperature spectra in the PORH test. Furthermore, to quantify the oscillation amplitude response to occlusion within different frequency ranges. MATERIALS AND METHODS: Ten healthy volunteers participated in the PORH test and their hand skin temperature and blood flow images were captured by infrared thermography (IRT) and laser speckle contrast imaging (LSCI) system, respectively. Extracted signals from selected areas were then transformed into the time-frequency space by continuous wavelet transform for cross-correlation analysis and oscillation amplitude response comparisons. RESULTS: The LSCI and IRT signals extracted from fingertips showed stronger hyperemia response and larger oscillation amplitude compared with other areas, and their spectral cross-correlations decreased with frequency. According to statistical analysis, their oscillation amplitudes in the PORH stage were obviously larger than the baseline stage within endothelial, neurogenic, and myogenic frequency ranges (p < 0.05), and their quantitative indicators of oscillation amplitude response had high linear correlations within endothelial and neurogenic frequency ranges. CONCLUSION: Comparisons of IRT and LSCI techniques in recording the reaction to the PORH test were made in both temporal and spectral domains. The larger oscillation amplitudes suggested enhanced endothelial, neurogenic, and myogenic activities in the PORH test. We hope this study is also significant for investigations of response to the PORH test by other non-invasive techniques.


Assuntos
Hiperemia , Humanos , Hiperemia/diagnóstico por imagem , Termografia , Imagem de Contraste de Manchas a Laser , Fluxometria por Laser-Doppler/métodos , Microcirculação , Pele/irrigação sanguínea , Fluxo Sanguíneo Regional
8.
Opt Express ; 29(19): 30473-30482, 2021 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-34614770

RESUMO

We propose and experimentally demonstrate symmetrical (homo-modal) and asymmetrical (hetero-modal) full-duplex bi-directional architectures based on dual-vector eigenmodes multiplexing over a 3 km few mode fiber (FMF). Firstly, 4 vector modes (VMs) of 2 mode groups (MGs), l = 0 (HE11o and HE11e modes) and l = +2 (EH11o and EH11e modes), each carrying a 14 GBaud quadrature phase-shift keying (QPSK) signal, are utilized in the up and down links and a 224 Gb/s same-mode bi-directional transmission is successfully realized. The crosstalk between the VMs in l = 0 and l = +2 of this full-duplex system is less than -13.8 dB. To strengthen the immunity to performance degradation induced by connector reflection and back scattering, we propose an effective approach to mitigate impairments by using hetero-modes on two terminals of the bi-directional system. Then, 2 VMs of l = 0 and 2 VMs of l = +2 are respectively employed in the up and down streams. The channel isolation between the VMs in l = 0 and l = +2 of such full-duplex link is larger than 19 dB, which supports a 448 Gb/s bi-directional transmission with 28 GBaud 16-ary quadrature amplitude modulation (QAM) modulation over a 3 km FMF by using 2 × 2 MIMO. Moreover, mode-wavelength division multiplexing including 2 modes and 4 wavelengths in both up and down streams is implemented in the transmission system. A total capacity of the 1.792 Tb/s link with 28 GBaud 16-QAM signal over each channel is successfully realized over the 3 km FMF. The measured bit-error-ratios (BERs) of all channels are below the 7% hard decision forward error correction (FEC) threshold at 3.8 × 10-3. The experimental results adequately indicate that such a scheme has a great potential in high-speed bi-directional point-to-point (P2P) optical interconnects.

9.
BMC Med Inform Decis Mak ; 21(Suppl 2): 99, 2021 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-34330266

RESUMO

BACKGROUND: As proven to reflect the work state of heart and physiological situation objectively, electrocardiogram (ECG) is widely used in the assessment of human health, especially the diagnosis of heart disease. The accuracy and reliability of abnormal ECG (AECG) decision depend to a large extent on the feature extraction. However, it is often uneasy or even impossible to obtain accurate features, as the detection process of ECG is easily disturbed by the external environment. And AECG got many species and great variation. What's more, the ECG result obtained after a long time past, which can not reach the purpose of early warning or real-time disease diagnosis. Therefore, developing an intelligent classification model with an accurate feature extraction method to identify AECG is of quite significance. This study aimed to explore an accurate feature extraction method of ECG and establish a suitable model for identifying AECG and the diagnosis of heart disease. METHODS: In this research, the wavelet combined with four operations and adaptive threshold methods were applied to filter the ECG and extract its feature waves first. Then, a BP neural network (BPNN) intelligent model and a particle swarm optimization (PSO) improved BPNN (PSO-BPNN) intelligent model based on MIT-BIH open database was established to identify ECG. To reduce the complexity of the model, the principal component analysis (PCA) was used to minimize the feature dimension. RESULTS: Wavelet transforms combined four operations and adaptive threshold methods were capable of ECG filtering and feature extraction. PCA can significantly deduce the modeling feature dimension to minimize the complexity and save classification time. The PSO-BPNN intelligent model was suitable for identifying five types of ECG and showed better effects while comparing it with the BPNN model. CONCLUSION: In summary, it was further concluded that the PSO-BPNN intelligent model would be a suitable way to identify AECG and provide a tool for the diagnosis of heart disease.


Assuntos
Algoritmos , Eletrocardiografia , Humanos , Redes Neurais de Computação , Reprodutibilidade dos Testes , Análise de Ondaletas
10.
Opt Express ; 27(5): 7072-7086, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30876279

RESUMO

For hitless flexible coherent transceivers based next-generation agile optical network, efficient modulation format identification (MFI) is an essential element in digital signal processing (DSP) flow at the receiver-side (Rx). In this paper, we propose a blind and fast MFI scheme with high identification accuracy at low optical signal-to-noise ratio (OSNR) regime. This is achieved by first raising the signal to the 4th power and calculate the peak-to-average power ratio (PAPR) of the corresponding spectra to distinguish 32 quadrature amplitude modulation (QAM) from quadrature phase shift keying (QPSK), 16 and 64QAM signals. Then, followed by iterative partition schemes to remove signals with phase ±π4,±3π4 (or QPSK-like phases) based on the signal amplitudes, the PAPR of the remaining signals is calculated to distinguish the other three formats. Additionally, by frequency offset (FO) pre-compensation, the spectrum can be obtained using sparse-fast-Fourier-transform (S-FFT), which greatly reduces the total complexity. The MFI performance is numerically and experimentally investigated by 28 Gbaud dual-polarization (DP) coherent optical back-to-back (B2B) and up to 1500 km standard single mode fiber (SSMF) transmission system using QPSK, 16QAM, 32QAM, and 64QAM. Results show that high identification accuracy can be achieved, even when OSNR is lower than that required for the 20% forward error correction (FEC) threshold of BER=2×10-2 for each format. Furthermore, fast format switching between 64QAM-32QAM and 32QAM-16QAM are demonstrated experimentally for B2B scenario and 900 km SSMF with the proposed MFI technique, respectively.

11.
Appl Opt ; 57(29): 8594, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30461931

RESUMO

The correction to the funding in Appl. Opt.56, 6504 (2017)APOPAI0003-693510.1364/AO.56.006504 is presented in this erratum.

12.
Appl Opt ; 56(23): 6504-6510, 2017 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-29047940

RESUMO

This paper demonstrates the principles of static and dynamic north-finding methods by measuring the projection of the Earth's rotation rate with a fiber optic gyroscope. For a comprehensive comparison of the two methods, the influence of a closed-loop feedback mechanism of a servo motor in a turntable is taken into consideration. Thus, we proposed the static and dynamic north-finding experimental implementations according to the different impact of the motor jitters and the different seeking times. Experimental results show that the dynamic method can reduce the north-finding bias error and instability by 60.1% and 54.6%, respectively, in the seeking time of 360 s, while the reduced proportions are 81.3% and 82.5%, respectively, in the seeking time of 120 s, compared with the static method under the jittering effect of the turntable. Therefore, it can be concluded that the dynamic method is more accurate and robust to the jittering effect.

13.
Opt Express ; 22(5): 5037-42, 2014 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-24663842

RESUMO

This paper firstly demonstrated the refractive index (RI) characteristics of a singlemode-claddingless-singlemode fiber structure filter based fiber ring cavity laser sensing system. The experiment shows that the lasing wavelength shifts to red side with the ambient RI increase. Linear and parabolic fitting are both done to the measurements. The linear fitting result shows a good linearity for applications in some areas with the determination coefficient of 0.993. And a sensitivity of ~131.64nm/RIU is experimentally achieved with the aqueous solution RI ranging from 1.333 to 1.3707, which is competitively compared to other existing fiber-optic sensors. While the 2 order polynomial fitting function, which determination relationship is higher than 0.999, can be used to some more rigorous monitoring. The proposed fiber laser has a SNR of ~50dB, and 3dB bandwidth ~0.03nm.

14.
Appl Opt ; 53(23): 5259-63, 2014 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-25320937

RESUMO

We propose and demonstrate a fiber Bragg grating sensor interrogator based on a 2D imaging system using a virtually imaged phased array (VIPA) and infrared camera. There are no moving parts, and the interrogator has good stability and reliability. The absolute wavelength accuracy of the interrogator is better than that of traditional diffraction grating and a 1D-imaging-system-based method, thanks to the VIPA's high spectral resolution and large angular dispersion. The wavelength resolution of the interrogator is about 7 pm, and the spectral range of this interrogator is more than 30 nm. The optimum setup for the best wavelength resolution is analyzed.

15.
Appl Opt ; 52(25): 6359-63, 2013 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-24085098

RESUMO

An interferometric fiber-optic vibration sensing system using the phase-generated carrier (PGC) method is proposed and experimentally demonstrated. The sensing section consists of a Sagnac interferometer combined with a Mach-Zehnder interferometer, a length of sensing fiber is shared between the two interferometers. The PGC demodulation scheme is used to demodulate the time-varying phase shifts induced by vibrations. Spatial information can be extracted from the demodulated results. A prototype sensing system with a 628 m long sensing fiber has been tested and a spatial resolution better than 12 m is successfully achieved.

16.
Opt Express ; 20(13): 14109-16, 2012 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-22714475

RESUMO

High-throughput real-time optical integrators are of great importance for applications that require ultrafast optical information processing, such as real-time phase reconstruction of ultrashort optical pulses. In many of these applications, integration of wide optical bandwidth signals is required. Unfortunately, conventional all-optical integrators based on passive devices are usually sensitive to the wavelength and bandwidth of the optical carrier. Here, we propose and demonstrate a passive all-optical intensity integrator whose operation is independent of the optical signal wavelength and bandwidth. The integrator is implemented based on modal dispersion in a multimode waveguide. By controlling the launch conditions of the input beam, the device produces a rectangular temporal impulse response. Consequently, a temporal intensity integration of an arbitrary optical waveform input is performed within the rectangular time window. The key advantage of this device is that the integration operation can be performed independent of the input signal wavelength and optical carrier bandwidth. This is preferred in many applications where optical signals of different wavelengths are involved. Moreover, thanks to the use of a relatively short length of multimode waveguide, lower system latency is achieved compared to the systems using long dispersive fibers. To illustrate the versatility of the optical integrator, we demonstrate temporal intensity integration of optical waveforms with different wavelengths and optical carrier bandwidths. Finally, we use this device to perform high-throughput, single-shot, real-time optical phase reconstruction of phase-modulated signals at telecommunications bit rates.


Assuntos
Dispositivos Ópticos , Processamento de Sinais Assistido por Computador/instrumentação , Telecomunicações/instrumentação , Sistemas Computacionais , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento
17.
ACS Omega ; 7(50): 46003-46011, 2022 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-36570205

RESUMO

Real-time polymerase chain reaction (PCR) technology is essential in nucleic acid detection and point-of-care testing (POCT). However, nowadays, the classical qPCR instrument has the deficiency of its bulky volume, high cost, and inconvenience to use; hence, a low-cost and easy-to-use PCR equipment was thus developed consisting of a hardware subsystem as well as a software subsystem based on an improved proportional-integral-derivative (PID) system. The proposed system not only could hold self-setting reaction cycles of temperature rising and falling automatically but also the temperature during the constant temperature stage was regulated steady based on improved temperature control algorithm, which proved its great effect compared with the reaction temperature derived from an infrared thermal imaging camera. The experimental results in gene detection research also could indicate its applicability and stability of our developed PCR system by using the amplification curve analysis, the melting curve analysis, and agarose gel electrophoresis analysis compared with the commercial PCR instrument, which illustrates the great potential application value of the proposed PCR system.

18.
Opt Express ; 19(24): 24563-8, 2011 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-22109484

RESUMO

We present an all-optical passive low-cost spectral filter that exhibits a high-resolution periodic sawtooth spectral pattern without the need for active optoelectronic components. The principle of the filter is the partial masking of a phased array of virtual light sources with multiply jammed diffraction orders. We utilize the filter's periodic linear map between frequency and intensity to demonstrate fast sensitive interrogation of fiber Bragg grating sensor arrays and ultrahigh-frequency electrical sawtooth waveform generation.


Assuntos
Filtração/instrumentação , Dispositivos Ópticos , Refratometria/instrumentação , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento
19.
Opt Express ; 19(24): 23809-17, 2011 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-22109406

RESUMO

The ability to control chromatic dispersion is paramount in applications where the optical pulsewidth is critical, such as chirped pulse amplification and fiber optic communications. Typically, devices used to generate large amounts (>100 ps/nm) of chromatic dispersion are based on diffraction gratings, chirped fiber Bragg gratings, or dispersion compensating fiber. Unfortunately, these dispersive elements suffer from one or more of the following restrictions: (i) limited operational bandwidth, (ii) limited total dispersion, (iii) low peak power handling, or (iv) large spatial footprint. Here, we introduce a new type of tunable dispersive device, which overcomes these limitations by leveraging the large modal dispersion of a multimode waveguide in combination with the angular dispersion of diffraction gratings to create chromatic dispersion. We characterize the device's dispersion, and demonstrate its ability to stretch a sub-picosecond optical pulse to nearly 2 nanoseconds in 20 meters of multimode optical fiber. Using this device, we also demonstrate single-shot, time-wavelength atomic absorption spectroscopy at a repetition rate of 90.8 MHz.


Assuntos
Tecnologia de Fibra Óptica/instrumentação , Refratometria/instrumentação , Ressonância de Plasmônio de Superfície/instrumentação , Cor , Desenho de Equipamento , Análise de Falha de Equipamento
20.
ACS Appl Mater Interfaces ; 13(12): 14718-14727, 2021 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-33728892

RESUMO

Metals were for decades perceived as devoid of interesting optical properties that could be harnessed for optical components and devices. However, with the development of accurate nanofabrication techniques and precise control over architectural parameters, metals can be structured and characterized on the nanoscale. Metallic plasmonic nanomaterials exhibit a number of unique structural and optical properties, which offer the potential for developing new types of plasmonic devices. Here, we demonstrate a low-loss broadband polarizer based on a hybrid plasmonic fiber structure using metals as polarization-selective absorption materials. The polarization mechanism, design, fabrication, and characteristics of the plasmonic polarizers are investigated theoretically, numerically, and experimentally. The theoretical analysis predicts that the polarization-selective absorption with insensitivity to wavelength enables hybrid plasmonic fibers to function as broadband polarizers. Numerical simulations give the comparison of the polarization-selective absorption of various metallic nanomaterials (Ag, Au, In, Al, Cr) and show that aluminum is regarded as the optimum absorption material for the plasmonic polarizer. Experimental results show that through precise control over geometrical parameters, this device is capable of offering a high polarization extinction ratio (PER) of over 40 dB and a low insertion loss (IL) of less than 1.3 dB in the wavelength region of 810.1-870.0 nm. Compared with commercial birefringent-crystal-fiber polarizers, the plasmonic fiber polarizer has a better PER and IL bandwidth. These merits, combined with a compact and robust configuration, enable the plasmonic polarizer to have great potential in a broad range of applications.

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