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VCSEL-based differential modulation technique for high-speed gigabit passive optical networks
摘要： With the convergence towards 5G, optical networks need to be upgraded to support the emerging data tsunami. This work experimentally demonstrates the first real-time transmission of 20 Gbps over a class 10G 1550 nm vertical cavity surface emitting laser (VCSEL) in the context of on-off-keying (OOK) modulation format, by employing VCSEL differential drive mode technique, for adoption in high-speed gigabit passive optical networks (GPONs). Two OOK data streams each with 10 Gbps are differentially modulated onto a single VCSEL, therefore generating an aggregated data rate of 20 Gbps OOK signal. A receiver sensitivity of -13.36 dBm is experimentally achieved. Through extinction ratio optimization, an error free transmission over 24.7 km single mode fibre is attained, with a transmission penalty of 1.91 dB. Our proposed technique alleviates band-limitation of the VCSEL carrier, and doubles the channel data rate without replacing the transmitter optics.
关键词： optical fibre,on–off-keying,passive optical network,Vertical cavity surface emitting laser
更新于2025-09-10 09:29:36
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Ultrasonic detection of high-intensity focused ultrasound field using quadrature point phase step in a fibre optic interferometric sensor
摘要： A compact low-temperature cross-talk all-fibre ultrasonic sensor based on quadrature point phase step is proposed and experimentally demonstrated for the detection of high-intensity focused ultrasound (HIFU). The end facet of the graded index fibre was microfabricated with a 3π/2 phase step, which forms an ultra-compact two-wave interferometer. The ultrasonic wave front can be simply detected with phase-front modulation. The all-fibre configuration allows the sensor to detect the HIFU field at a high intensity level. More importantly, the proposed sensor is virtually temperature-independent due to the ultra-thin phase step. The experimental results show that the ultrasonic sensor has a sensitivity of 324mV/MPa, and the standard variation of the temperature cross-sensitivity is only 1.7%. The proposed fibre sensor is expected to have potential applications in HIFU detection due to its tolerance at high intensity levels and low-temperature cross-sensitivity.
关键词： phase-front modulation,HIFU field,phase step,optical fibre ultrasound sensor
更新于2025-09-10 09:29:36
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Machine learning analysis of extreme events in optical fibre modulation instability
摘要： A central research area in nonlinear science is the study of instabilities that drive extreme events. Unfortunately, techniques for measuring such phenomena often provide only partial characterisation. For example, real-time studies of instabilities in nonlinear optics frequently use only spectral data, limiting knowledge of associated temporal properties. Here, we show how machine learning can overcome this restriction to study time-domain properties of optical fibre modulation instability based only on spectral intensity measurements. Specifically, a supervised neural network is trained to correlate the spectral and temporal properties of modulation instability using simulations, and then applied to analyse high dynamic range experimental spectra to yield the probability distribution for the highest temporal peaks in the instability field. We also use unsupervised learning to classify noisy modulation instability spectra into subsets associated with distinct temporal dynamic structures. These results open novel perspectives in all systems exhibiting instability where direct time-domain observations are difficult.
关键词： machine learning,extreme events,optical fibre modulation instability,unsupervised learning,supervised neural network
更新于2025-09-10 09:29:36
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[Institution of Engineering and Technology 2nd IET International Conference on Biomedical Image and Signal Processing (ICBISP 2017) - Wuhan, China (13-14 May 2017)] 2nd IET International Conference on Biomedical Image and Signal Processing (ICBISP 2017) - An optical fibre based ex-vivo device for detection of cytokines
摘要： Cytokine detection is an essential topic for biomedical research. Herein we demonstrated an ex-vivo device based on a silica optical fibre for monitoring of locally variable cytokine IL-6 concentrations using a sandwich immunoassay scheme. The fibre was designed to be introduced into the perforated catheter with micrometre size holes drilled along its length to enable fluid exchange between the outside and inside of the catheter. An exposed optical fibre (diameter 125 μm) modified with a layer of gold nanoparticles was functionalized with the IL-6 capture antibody to form the sensing interface. The IL-6 detection antibody which was loaded on the fluorescently labelled magnetic nanoparticles, was used for reporting the analyte signal. This device was successfully applied to detect cytokine IL-6 with the detection limit of 1 pg mL-1 in the sample volume of 1 μL. It has the linear detection range of 1-400 pg mL-1 and is capable of detecting localised IL-6 secreted by BV2 cells following their liposaccharide stimulation. This universal biological detection system is suitable as a platform for the in-vivo devices able to monitor multiple health conditions.
关键词： spatial detection,IL-6,medical device,cytokines,Optical fibre
更新于2025-09-10 09:29:36
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[ASME 2018 12th International Pipeline Conference - Calgary, Alberta, Canada (Monday 24 September 2018)] Volume 3: Operations, Monitoring, and Maintenance; Materials and Joining - Real-Time Continuous Pipeline Integrity Monitoring Utilising Telecommunications Optical Fibre Cables
摘要： A recent trend in the field of pipeline monitoring has been the utilisation of an optical fibre based distributed acoustic sensing (DAS) technology, for the purpose of security monitoring of buried pipelines [1-3]. The technology comprises an interrogator, connected to an optical fibre cable, which is interrogated to acquire coherent Rayleigh backscatter. Localised environmental vibrations may result in a proportional strain of the fibre. This strain results in a localised optical path length variation, resulting in a phase distortion in the measured signals. Application of signal processing techniques infer the characteristic of the originating stimulus, and thus identify and locate the source activity of interest. Activity may arise as a result of ground excavation, vehicular movement, or similar in the vicinity of the pipeline. Researchers are now studying the possibility of utilisng this technology for the purpose of pipeline leak detection monitoring [4]. This paper provides a review of one such programme of work. Results are presented for a permanent installation, where signatures relating to leaks were identified, and located in the resulting DAS data. Results are provided relating to liquid leaks, where product was emitted at a flow rate of 20.0l/minute and operational pressure 20.0bar.
关键词： Distributed Acoustic Sensing,Leak Detection,Optical Fibre sensing
更新于2025-09-09 09:28:46
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A novel use of etched multi-mode fibre as magnetic field sensor
摘要： In this study, an optical fibre magnetic field sensor is experimentally demonstrated using chemical etched multimode fibre sandwiched between two single mode fibres. The obtained result of the magnetic field and refractive index response shows that the decreasing fibre diameter in the sensing region plays an important role to enhance the sensitivity of the device. The magnetic field sensing is based on a tunable refractive index (RI) property of magnetic fluid infiltrated into the capillary tube. The sensing system is verified by testing RI of different concentrations of sodium chloride (NaCl) solution before sealing in capillary tube. Experimental results show that the sensor with taper fibre diameter of 45?μm has relatively high magnetic field sensitivity of ～ 0.993?dB/mT ranging from 0 to 6?mT. The proposed devices find potential applications in magnetic field sensing.
关键词： optical fibre magnetic field sensor,sensitivity,chemical etched multimode fibre,refractive index,magnetic fluid
更新于2025-09-04 15:30:14
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Numerical simulation of light propagation in metal-coated SNOM tips
摘要： Presented are the results of numerical simulations accomplished to investigate the propagation of electromagnetic excitations in certain types of metal-coated tapered tips terminating SiO2 multimode optical fibres with a subwavelength output aperture. The numerical simulations were initiated in order to enable better interpretation of previously reported experimental results concerning some features of the mesoscopic effect of spectral modulation observed for a broadband light transmitted by such tips. This effect occurs due to the interference between a small number of waveguide modes exiting a metal-coated tip, and the experimental results indicate a possible mode-selective photon-plasmon coupling in the studied tips. To match the experimental conditions, the tips were modelled for the light wavelength of 800 nm as three-layer systems (with the intermediate adhesion Cr layer and the outer layer of Al or Au). However, due to computational restrictions the end of a tip, only 18 μm long (most significant), was modelled. Numerical simulations yielded the dependences of propagation and attenuation constants on the fibre core radius for the most intensive (both photonic and plasmonic) output modes. The pairs of modes most probably contributing to the observed spectral modulation were identified. Although the simulations did not reveal any explicit mode coupling, the imperfections of real tips can cause mode transformations implying possible involvement of more than two modes. The thin (20 nm) Cr layer plays the main role for plasmonic modes generated on its SiO2 interface, which explains the small outer metal layer influence on the observed modal dispersion.
关键词： numerical simulation,multimode optical fibre,optics,spectral modulation,SNOM tip,plasmonics,photonics
更新于2025-09-04 15:30:14
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Optimal tone detection for optical fibre vector hydrophone
摘要： An optimal tone detector based on the Neyman–Pearson criterion is proposed for the optical fibre vector hydrophone (OFVH). The detector takes account of the difference between noise levels on the acoustic pressure channel and the three particle acceleration channels of an OFVH. Explicit expressions for the impulse responses of pre-filters that are central to the proposed detector are given. Analyses show that the proposed detector is equivalent to the minimum variance distortionless response beamformer for the OFVH. In the case of identical noise on all particle acceleration channels, the signal-to-noise ratio (SNR) gain of the detector is 10lg(1 + μ) dB (μ is the noise power ratio of OFVH channels at the tone frequency), whereas the SNR gain also depends on target direction and is bounded by 10lg(1 + μmin) and 10lg(1 + μmax) dB when noise on all particle acceleration channels are different. Results from both simulations and lake experiment data show that the proposed detector outperforms tone detectors that use (i) the acoustic pressure signal, (ii) the particle acceleration signals and (iii) equally the combination of acoustic pressure signal and particle acceleration signals.
关键词： signal-to-noise ratio gain,Neyman–Pearson criterion,optimal tone detector,optical fibre vector hydrophone
更新于2025-09-04 15:30:14