Time Division Multiplexing Technique Research Articles

Two-Component Gas Sensor of Time-Division Multiplexing Technique Based on QEPAS and LITES

Two-Component Gas Sensor of Time-Division Multiplexing Technique Based on QEPAS and LITES

Simultaneous atmospheric CH4, CO2 and O2 detection using fiber-optic switch (FOS)-based time-division multiplexed NIR laser long optical path absorption spectroscopy

A near-infrared (NIR) distributed feedback (DFB) laser sensor based on long optical path absorption spectroscopy technique was developed for simultaneous measurement of atmospheric methane (CH4), carbon dioxide (CO2) and oxygen (O2). A fiber-optic switch (FOS) in conjunction with the time-division multiplexing (TDM) technique was adopted to enable different lasers scan over the target gas absorption lines in turn. The long optical path wavelength modulation spectroscopy (WMS) technique with second harmonic detection as well as a laser power fluctuation correction method was used to improve the sensor’s precision and accuracy. For the selected gas absorption lines, located at 6046.945 cm-1, 6361.245 cm-1 and 7877.647 cm-1, the detection limit (1σ) of 0.034 parts per million (ppm) for CH4, 11.921 ppm for CO2 and 0.14% for O2 was achieved according to the concentration and noise level. Allan deviation analysis indicates that the 1-s measurement precision was 0.030 ppm for CH4, 11.518 ppm for CO2 and 0.14% for O2, which could be improved to 6.5E-4 ppm, 0.255 ppm and 0.005% at an optimal average time of 800 s. A two-day continuous measurement of the CH4, CO2, and O2 concentration from ambient air was carried out, which verifies the stability and robustness of the developed multi-gas sensor.

Optimization of the Decision Criterion for Increasing the Bandwidth Utilization by Means of the Novel Effective DBA Algorithm in NG-PON2 Networks

In this paper, the reasons for the bandwidth and wavelength utilization in future next-generation passive optical networks are presented, and the possibilities for realization and utilization of extended dynamic wavelength and bandwidth algorithms for the second next-generation passive optical networks (NG-PON2) are analyzed. Next, principles of the effective dynamic bandwidth allocation are introduced in detail, focused on the importance of the decision criterion optimization. To achieve a better bandwidth utilization of dedicated wavelengths in NG-PON2 networks, this paper is focused on the novel effective dynamic bandwidth allocation algorithm with adaptive allocation of wavelengths to optical network units as well as the optimization of the decision criterion. The algorithm and the proposed method are tested and evaluated through simulation with actual traffic data. For analyzing novel extended dynamic wavelength and bandwidth algorithms used for various cases of wavelength allocation in NG-PON2 networks, the effective dynamic bandwidth allocation algorithm analysis is realized in the enhancement of simulation program. Finally, an optimization of the decision criterion defining a minimum bandwidth utilization of the actual wavelength is executed for NG-PON2 networks based on the hybrid time and wavelength division multiplexing technique.

Photoacoustic dual-gas sensor for simultaneous detection of hydrogen and water vapor

Hydrogen (H2) is an important energy carrier, however, it can be hazardous owing to the risks involved with boring and explosion with colorless flames. By detecting the concentrations of H2 and vapor water (H2O) in real time, such risks can be prevented in advanced. In this study, a sensor system is developed based on photoacoustic spectroscopy using an H-type photoacoustic cell (PAC). Further, the time division multiplexing technique is used in a specific scanning period to realize dual-gas simultaneous detection. The dimensions of the PAC are optimized (inner volume: 1.8 cm3) and N-th characteristic frequencies are simulated through multiphysics simulation in COMSOL software. The optimized PAC is applied in the system and experiments of simultaneous dual gases detection are performed. The detection results show that the sensor's response time is 0.51 s and the recovery time is 0.38 s, and the minimal detection limit of H2 is 138.69 ppm and H2O can reach 3.70 ppm.

Time-Division Multiplexing Light Field Display with Learned Coded Aperture.

Conventional stereoscopic displays suffer from vergence-accommodation conflict and cause visual fatigue. Integral-imaging-based displays resolve the problem by directly projecting the sub-aperture views of a light field into the eyes using a microlens array or a similar structure. However, such displays have an inherent trade-off between angular and spatial resolutions. In this paper, we propose a novel coded time-division multiplexing technique that projects encoded sub-aperture views to the eyes of a viewer with correct cues for vergence-accommodation reflex. Given sparse light field sub-aperture views, our pipeline can provide a perception of high-resolution refocused images with minimal aliasing by jointly optimizing the sub-aperture views for display and the coded aperture pattern. This is achieved via deep learning in an end-to-end fashion by simulating light transport and image formation with Fourier optics. To our knowledge, this work is among the first that optimize the light field display pipeline with deep learning. We verify our idea with objective image quality metrics (PSNR, SSIM, and LPIPS) and perform an extensive study on various customizable design variables in our display pipeline. Experimental results show that light fields displayed using the proposed technique indeed have higher quality than that of baseline display designs.

Enhanced dispersion reduction using apodized uniform fiber Bragg grating for optical MTDM transmission systems

The aim of this work is to propose a model for enhancing chromatic dispersion compensation in standard single mode optical fibers (SSMFs). The proposed model consists of a single stage Apodized Uniform Fiber Bragg Gratings (AUFBG) in a post-compensation scheme. It is based on the Maximum Time Division Multiplexing (MTDM) technique. The performance of the proposed model is evaluated through the quality factor (Q-factor) and Bit Error Rate (BER) in four cases, in a comparative study. In case one, the system performance is evaluated without using UFBG. The other cases study the effect of the proposed model with using different connections schemes and the most common apodization functions. For simulation, the proposed model is connected in a 10 Gbps WDM 70 km link under ordinary operating parameters. The simulation and evaluation process is conducted by Optisystem 7.0. In the pre-compensation scheme, the best results are obtained as a maximum Q-factor of 9.2 and a minimum BER of 3.25 × 10–20, using a tanh apodization function. The proposed model realizes an improvement over the related work by at least ~ 68%.

A CMOS Microelectrode Array System With Reconfigurable Sub-Array Multiplexing Architecture Integrating 24,320 Electrodes and 380 Readout Channels.

This article presents a CMOS microelectrode array (MEA) system with a reconfigurable sub-array multiplexing architecture using the time-division multiplexing (TDM) technique. The system consists of 24,320 TiN electrodes with 17.7 μm-pitch pixels and 380 column-parallel readout channels including a low-noise amplifier, a programmable gain amplifier, and a 10-b successive approximation register analog to digital converter. Readout channels are placed outside the pixel for high spatial resolution, and a flexible structure to acquire neural signals from electrodes selected by configuring in-pixel memory is realized. In this structure, a single channel can handle 8 to 32 electrodes, guaranteeing a temporal resolution from 5 kS/s to 20 kS/s for each electrode. A 128 × 190 MEA system was fabricated in a 110-nm CMOS process, and each readout channel consumes 81 μW at 1.5-V supply voltage featuring input-referred noise of 1.48 μVrms without multiplexing and 5.4 μVrms with multiplexing at the action-potential band (300 Hz-10 kHz).

Dispersion compensation using cascaded apodized CFBGs under MTDM transmission technique: Enhanced system performance

This study focuses on compensating chromatic dispersion affecting the propagated signal in a standard single mode optical fibers (SSMFs). We propose a model that consists of an identical four stages cascaded linear chirped apodized fiber Bragg gratings (CFBGs) in a post-compensation scheme under Maximum Time Division Multiplexing (MTDM) technique. MTDM is free of the limitations resulting from the fiber nonlinear effects. It, thus, effectively utilizes optical wavelength and operating in various network of different distances and capacities. Therefore, MTDM is designed to be used in the high-capacity and high-speed transmission systems. The evaluation of the proposed model performance is performed through a comparative study using different connections and the most common apodization functions. This comparative study includes three cases based on the used connection scheme. A 10 Gbps Wavelength Division Multiplexing (WDM) 70 km link is simulated under ordinary operating parameters. Optisystem 7.0 is used for the simulation and evaluation process, in terms of two metrics which are quality factor (Q-factor) and bit error rate (BER). In the pre-compensation scheme, the highest results are: Q-factor = 7.664 and BER = 8.99 × 10–15, using the raised cosine apodization function. Using the raised sine apodization in the post-compensation connection realizes the best performance: Q-factor = 8.58 and BER = 4.77 × 10–18. In the symmetrical-compensation scheme and using the raised sine apodization, the proposed model attains the highest Results: Q-factor = 7.49 and BER = 3.53 × 10–14. The proposed model achieves at least 92.6% improvement in BER and 3.75% in Q-factor over the related works. The study is a simulation work and is performed through Optisystem ver. 7.

High-speed wavelength interrogation system based on crossed HiBi-FLMs for array FBGs

A novel ultrafast wavelength interrogation system for array fiber Bragg gratings (FBGs) has been proposed and experimentally demonstrated, the operation principle is based on pulsed optical source (POS) combined with edge-filtering method and time-division multiplexing (TDM) technique. Thanks to the Gaussian-shape nature and numerous passband channels of the HiBi-FLM transmission, the simultaneous interrogation of array wavelength-division multiplexing (WDM) FBGs can be realized by employing crossed HiBi-FLMs scheme. The HiBi-FLM can provide an individual edge filter for each WDM-FBG and map the FBG reflection spectra into corresponding optical intensity, thus realizing the simultaneous interrogation of multiple WDM-FBGs. The interrogation speed of the proposed system is as high as 200 kHz, which can be further improved to hundreds of megahertz (MHz) by increasing the repetition rate of the POS, the response speed of the photodetector (PD), and the sampling rate of field programmable gate array (FPGA), as well as reducing the pulse width and the lengths of the delay lines. The proposed wavelength interrogation system features high speed, outstanding multiplexing capability, large dynamic range and simple configuration, thus providing a promising solution for various applications, such as quasi-distributed sensing, high-speed communication, medical treatment and the monitoring of ultrafast dynamic phenomena (e.g., molecular dynamics sensing and aircraft engine diagnostics).

Infrared dual-gas CH4/C2H2 sensor system based on dual-channel off-beam quartz-enhanced photoacoustic spectroscopy and time-division multiplexing technique

Highly sensitive and stable measurement of methane (CH4) and acetylene (C2H2) based on a novel dual-channel off-beam quartz-enhanced photoacoustic spectroscopy and time-division multiplexing technique was realized by a compact 3D-printed gas cell with a size of 3 × 2 × 1 cm3. Two near-infrared distributed feedback diode lasers were employed to target the CH4 absorption line at 6046.9 cm−1 and the C2H2 absorption line at 6521.2 cm−1, respectively. Second-harmonic wavelength modulation spectroscopy method was used for photoacoustic signal recovery. A minimum detection level of ∼ 7.63 parts-per-million in volume (ppmv) for CH4 and a level of ∼ 17.47 ppmv for C2H2 were achieved with a 1 s lock-in integration time, leading to a normalized noise equivalent absorption (NNEA) coefficient of 7.24 × 10-8 cm−1·W·Hz−1 and 3.73 × 10-8 cm−1·W·Hz−1 for CH4 and C2H2, respectively. Allan-Werle deviation analysis was employed to evaluate the stability and the minimum detection limit (MDL) of the developed photoacoustic CH4/C2H2 dual-gas photoacoustic sensor. Owing to the high stability of the developed sensor system, an MDL of ∼ 0.73 ppmv and an MDL of ∼ 1.60 ppmv with a 100 s averaging time were achieved for CH4 and C2H2, respectively.

Towards High-Resolution Imaging With Photonics-Based Time Division Multiplexing MIMO Radar

A photonics-based time division multiplexing (TDM) multiple-input and multiple-output (MIMO) radar is proposed to realize high-resolution imaging. In this MIMO radar, multiple transmitters generate time-domain orthogonal linearly frequency modulated (LFM) signals based on microwave photonic frequency octupling and optical TDM technique, and multiple receivers implement dechirping of the multi-channel radar echoes based on microwave photonic frequency mixing. The microwave photonic techniques make the system capable to generate and process broadband radar signals, and the TDM yields a high spectral efficiency, which allows a large bandwidth in each transmitter and receiver. Meanwhile, the TDM-MIMO ensures complete orthogonality between different channels and enables good flexibility in arranging more transmit and receive channels. Therefore, the proposed photonics-based TDM-MIMO radar can achieve both high range resolution and high angular resolution. In the experiment, a photonics-based 4 × 8 TDM-MIMO radar is established which has an operation bandwidth of 8 GHz in each transmit channel. The range resolution and angular resolution are estimated to be 1.9 cm and 1.1°, respectively. A broadband back projection (BP) imaging algorithm with both frequency and time-delay dependent phase compensation is proposed, based on which high resolution imaging of single and complex targets is achieved.

Software-defined optical intra-data center network and access control Strategy

The continuously emerging cloud services provide an unprecedented traffic growth into the large-scale data centers (DCs) globally. In this paper, we introduce an optical DC network (DCN) architecture to organize the servers into computing clusters. Since a high percentage of the total DCΝ traffic is served within a cluster, we assume two distinct networks: the intra-cluster passive optical network that handles the traffic destined to any server of the same cluster and the inter-cluster one to route the traffic to any other cluster. The servers interconnection within the passive optical intra-cluster network causes low power consumption, while the Top-of-Cluster (ToC) switch requires less ports than a relative Top-of-Rack (ToR) one to interconnect the same number of servers within the intra network, reducing even more the total power consumption. In the data plane, the intra- and the inter-cluster networks use separate wavelengths. In the control plane, the software-defined networking (SDN) paradigm is followed. Especially, in each cluster we adopt a cluster controller to coordinate the medium access control (MAC) in both the intra and inter-cluster networks. Unlike other studies that assume electrical connectivity with the controller, we consider that it is performed in the optical domain to guarantee the effective synchronized operation of the control and data planes. In our work, we focus on the intra-cluster network. We propose a synchronous transmission software-defined bandwidth allocation (SD-BA) MAC protocol to fairly coordinate the collisions-free transmission of different quality of service traffic categories in the intra-cluster network, based on the wavelength and time division multiplexing (W&TDM) techniques. The proposed DCN architecture along with the SD-MAC protocol provides scalability and efficiency. Simulations results show that the proposed SD-BA MAC protocol achieves almost 100% bandwidth utilization, while it reaches at high loads 145% higher throughput, 573% lower delay and 233% less dropped packets as compared to the relative DMAC network architecture (Zheng and Sun, Apr. 2020) [24]. Also, the proposed intra-cluster DCN architecture is compared to some other currently leading relative ones in terms of throughput and power consumption and it is proven to be a performance and energy efficient DCN solution.

Accelerating joint relaxation-diffusion MRI by integrating time division multiplexing and simultaneous multi-slice (TDM-SMS) strategies.

To accelerate the acquisition of relaxation-diffusion imaging by integrating time-division multiplexing (TDM) with simultaneous multi-slice (SMS) for EPI and evaluate imaging quality and diffusion measures. The time-division multiplexing (TDM) technique and SMS method were integrated to achieve a high slice-acceleration (e.g., 6×) factor for acquiring relaxation-diffusion MRI. Two variants of the sequence, referred to as TDM3e-SMS and TDM2s-SMS, were developed to simultaneously acquire slice groups with three distinct TEs and two slice groups with the same TE, respectively. Both sequences were evaluated on a 3T scanner with in vivo human brains and compared with standard single-band (SB) -EPI and SMS-EPI using diffusion measures and tractography results. Experimental results showed that the TDM3e-SMS sequence with total slice acceleration of 6 (multiplexing factor (MP) = 3 × multi-band factor (MB) = 2) provided similar image intensity and microstructure measures compared to standard SMS-EPI with MB = 2, and yielded less bias in intensity compared to standard SMS-EPI with MB = 4. The three sequences showed a similar positive correlation between TE and mean kurtosis (MK) and a negative correlation between TE and mean diffusivity (MD) in white matter. Multi-fiber tractography also shows consistency of results in TE-dependent measures between different sequences. The TDM2s-SMS sequence (MP = 2, MB = 2) also provided imaging measures similar to standard SMS-EPI sequences (MB = 2) for single-TE diffusion imaging. The TDM-SMS sequence can provide additional 2× to 3× acceleration to SMS without degrading imaging quality. With the significant reduction in scan time, TDM-SMS makes joint relaxation-diffusion MRI a feasible technique in neuroimaging research to investigate new markers of brain disorders.

Analytical modeling and impact analysis on multichannel symmetric optical and wireless NG-PON2 networks of CD, SPM, XPM and FWM impairments

A conceptual model for optical wireless (OW) interfacing with NG-PON2 access network is analyzed using N1-class backbone optical distribution and OW free-space optics (FSO) channels in the frontend to connect ONUs to symmetric 1.25/2.5/10 Gbps channels incorporating Time and Wavelength Division Multiplexing (TWDM) technique to deliver applications and services based on Fiber-to-the-X (FTTX), IoT and 5 G technologies. We successfully demonstrated the design and analysis of ODN channel attributes supporting coexistence approach in contiguous with fiber channel linear and nonlinear impairments (LNI), and atmospheric attenuations β due to haze, dry particles inside the premises for high-speed OW channel for indoor applications along with optimization of hybrid N1-power budget class distributing configuration propagating multi-channel (MC) OW-FSO TWDM NG-PON2 configurations supporting symmetric configuration. Multichannel input power is calculated to optimize up/down link spectrum ODN power to 4 and 3 dBm respectively at worst-case scenario accommodating eight symmetric channels. Simulation results achieved at 50.011 km in either direction are − 41.85/− 36.67/− 39.04/ dBm and − 33.63/− 42.78/− 37.92 dBm receiver sensitivities supporting 448 splitter configuration at 50.011 km, FWM efficiency is 1.65e-52 and FWM component power at as low as − 53 to − 54 dB in conjunction with CD, SPM, XPM, and FWM LNI for spectrum in either directions.

Multi-channel pseudo-random coding single-photon ranging and imaging

We demonstrate a multi-channel pseudo-random coding single-photon ranging system. A pseudo-random multiplexing technique is proposed, which realizes multi-channel pseudo-random ranging only by using one single-photon detector and processing circuit. Compared with the time division multiplexing technique, it will not reduce the maximum unambiguous range while increasing the number of the ranging channel. Eight-channel pseudo-random coding single-photon ranging was realized with the ranging accuracy better than 2 cm. Moreover, photon counting imaging was realized through scanning the laser beams of the eight-channel pseudo-random ranging system. There is no crosstalk between channels, which is suitable for multi-beam long-distance single-photon Lidar.

A novel design of switched boost action based multiport converter using dsPIC controller for renewable energy applications

ABSTRACT Traditionally the grid supplies only a particular voltage to the load, but today we are using ‘n’ number of loads with different voltage rating and converters. So, the conversion of the generated AC voltage into several stages of DC voltage before reaching the load is required. In this paper, the Multi Port Converter (MPC) is proposed, which is capable of converting a single valued AC voltage into several stages of DC voltage. The feasibility of employing of converter level switch node, as an interface to numerous output stages is examined in this paper. The connecting of several outputs at the identical node is accomplished by the use of time-division multiplexing technique. In this study, the input power is multiplexed into separate ports via a phenomenon known as Switching Boost Action (SBA). The prototype was developed for converting the 240 V, 50 Hz, single phase AC supply into two outputs and the 12 V DC supply which can fed to the loads, that can be stored in batteries for future use. This paper has been proposed to design SBA based MPC using dsPIC controller for renewable energy applications.

Tunable diode laser-based two-line thermometry: a noncontact thermometer for active body temperature measurement.

A precise and fast optical thermometer based on a tunable diode laser absorption spectroscopy is developed for breath diagnostics with relevance to noncontact body temperature measurement. As water vapor (H2O) is the major component in human breath, two optimal absorption lines of H2O at 1392 nm and 1371 nm are selected for sensitive body temperature measurement by systematically investigating the near-infrared spectral database. The optical thermometer is developed using two distributed feedback diode lasers with the time-division multiplexing technique to achieve real-time measurement. The sensor performance such as accuracy, repeatability, and time response is tested in a custom-designed gas cell with its temperature controlled in the range of 20°C-50°C. By measuring the test air with different water concentrations, the sensor consistently shows a quadratic response to temperature with an R-squared value of 0.9998. Under the readout rate of 1 s, the sensor achieves a measurement precision of 0.16°C, suggesting its potential applications to fast, accurate, and noncontact body temperature measurements.

Recording Strategies for High Channel Count, Densely Spaced Microelectrode Arrays.

Neuroscience research into how complex brain functions are implemented at an extra-cellular level requires in vivo neural recording interfaces, including microelectrodes and read-out circuitry, with increased observability and spatial resolution. The trend in neural recording interfaces toward employing high-channel-count probes or 2D microelectrodes arrays with densely spaced recording sites for recording large neuronal populations makes it harder to save on resources. The low-noise, low-power requirement specifications of the analog front-end usually requires large silicon occupation, making the problem even more challenging. One common approach to alleviating this consumption area burden relies on time-division multiplexing techniques in which read-out electronics are shared, either partially or totally, between channels while preserving the spatial and temporal resolution of the recordings. In this approach, shared elements have to operate over a shorter time slot per channel and active area is thus traded off against larger operating frequencies and signal bandwidths. As a result, power consumption is only mildly affected, although other performance metrics such as in-band noise or crosstalk may be degraded, particularly if the whole read-out circuit is multiplexed at the analog front-end input. In this article, we review the different implementation alternatives reported for time-division multiplexing neural recording systems, analyze their advantages and drawbacks, and suggest strategies for improving performance.

Dispersion compensation analysis of optical fiber link using cascaded apodized FBGs hybrid with maximum time division multiplexing transmission technique

Dispersion compensation analysis of optical fiber link using cascaded apodized FBGs hybrid with maximum time division multiplexing transmission technique

Active Cylindrical Metasurface With Spatial Reconfigurability for Tunable Backward Scattering Reduction

This article presents an active cylindrical metasurface with spatial reconfigurability to achieve dynamic control of the radar cross section (RCS) reduction. The proposed metasurface is designed based on the combination of microwave transmission network and Mie scattering. In particular, by modulating the spatial coding sequence of p-i-n diodes in meta-atoms, the surface impedance of the metasurface can be dynamically changed, which enables an active metasurface to operate in an expanded frequency band via time-division multiplexing technique. Both simulated and measured results demonstrate that the proposed cylindrical metasurface with an ultrathin thickness of $0.018\lambda $ can be continuously tuned across a wide fractional bandwidth over 32% for reducing backward scattering by 10 dB. The proposed metasurface with ultrathin thickness, tunability, conformal profile, and high performance may be applied to wideband RCS reduction, as well as advanced noninvasive detection, communication, etc.