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Most of Optical Camera Communication (OCC) systems benefit from the rolling shutter mechanism of Complementary Metal-Oxide Semiconductor (CMOS) cameras to record the brightness evolution of the Light-Emitting Diode (LED) through dark and bright strips within images. While this technique enhances the maximum achievable data rate, the main difficulty lies in the demodulation of the signal extracted from images, subject to blooming effect. Thus, two main approaches were proposed to deal with this issue, using adaptive thresholds whose value evolves according to amplitude changes or detecting signal variations with the first-order derivative. As the second method is more robust, a new demodulation method based on the detection of the zeros of the first-order derivative of the extracted signal was proposed in this paper. Obtained results clearly show an improvement in the extracted signal demodulation compared to other methods, achieving a raw Bit Error Rate (BER) of 10−3 around 50 cm in a Line-Of-Sight scenario, and increasing the maximum communication distance by 43.5%, reaching 330 cm in the case of a Non-Line-Of-Sight transmission. [ABSTRACT FROM AUTHOR]

The deep integration of communication and sensing technology in fiber-optic systems has been highly sought after in recent years, with the aim of rapid and cost-effective large-scale upgrading of existing communication cables in order to monitor ocean activities. As a proof-of-concept demonstration, a high-degree of compatibility was shown between forward-transmission distributed fiber-optic vibration sensing and an on–off keying (OOK)-based communication system. This type of deep integration allows distributed sensing to utilize the optical fiber communication cable, wavelength channel, optical signal and demodulation receiver. The addition of distributed sensing functionality does not have an impact on the communication performance, as sensing involves no hardware changes and does not occupy any bandwidth; instead, it non-intrusively analyzes inherent vibration-induced noise in the data transmitted. Likewise, the transmission of communication data does not affect the sensing performance. For data transmission, 150 Mb/s was demonstrated with a BER of 2.8 × 10−7 and a QdB of 14.1. For vibration sensing, the forward-transmission method offers distance, time, frequency, intensity and phase-resolved monitoring. The limit of detection (LoD) is 8.3 pε/Hz1/2 at 1 kHz. The single-span sensing distance is 101.3 km (no optical amplification), with a spatial resolution of 0.08 m, and positioning accuracy can be as low as 10.1 m. No data averaging was performed during signal processing. The vibration frequency range tested is 10–1000 Hz. [ABSTRACT FROM AUTHOR]

We explore the use of smartphones to decode data transmitted from LEDs to smartphone cameras in visible light communication (VLC) applied to indoor positioning applications. The LEDs—modified to enable rapid on-off keying—transmit identification codes or optically encoded location data imperceptible to human perception. Equipped with a camera, the smartphone employs a single framed image to detect the presence of the luminaires in the image, decode their transmitted identifiers or locations, and determine the smartphone's position and orientation relative to the luminaires. The camera captures and processes images continuously. The following fundamental issues are addressed in this research: (i) analyzing the camera parameters on smartphones that affect data decoding results; (ii) exploiting the rolling shutter effect of the CMOS image sensor to receive multiple bits of data encoded in the optical communication line with a single frame shot; (iii) advancing research in developing algorithms to process data from multiple LEDs simultaneously. We conduct experiments to evaluate and analyze feasibility, as well as the challenges of the design, through scenarios varying in distance, transmission frequency, and data length. [ABSTRACT FROM AUTHOR]

Most of Optical Camera Communication (OCC) systems benefit from the rolling shutter mechanism of Complementary Metal-Oxide Semiconductor (CMOS) cameras to record the brightness evolution of the Light-Emitting Diode (LED) through dark and bright strips within images. While this technique enhances the maximum achievable data rate, the main difficulty lies in the demodulation of the signal extracted from images, subject to blooming effect. Thus, two main approaches were proposed to deal with this issue, using adaptive thresholds whose value evolves according to amplitude changes or detecting signal variations with the first-order derivative. As the second method is more robust, a new demodulation method based on the detection of the zeros of the first-order derivative of the extracted signal was proposed in this paper. Obtained results clearly show an improvement in the extracted signal demodulation compared to other methods, achieving a raw Bit Error Rate (BER) of 10−3 around 50 cm in a Line-Of-Sight scenario, and increasing the maximum communication distance by 43.5%, reaching 330 cm in the case of a Non-Line-Of-Sight transmission.

We explore the use of smartphones to decode data transmitted from LEDs to smartphone cameras in visible light communication (VLC) applied to indoor positioning applications. The LEDs—modified to enable rapid on-off keying—transmit identification codes or optically encoded location data imperceptible to human perception. Equipped with a camera, the smartphone employs a single framed image to detect the presence of the luminaires in the image, decode their transmitted identifiers or locations, and determine the smartphone’s position and orientation relative to the luminaires. The camera captures and processes images continuously. The following fundamental issues are addressed in this research: (i) analyzing the camera parameters on smartphones that affect data decoding results; (ii) exploiting the rolling shutter effect of the CMOS image sensor to receive multiple bits of data encoded in the optical communication line with a single frame shot; (iii) advancing research in developing algorithms to process data from multiple LEDs simultaneously. We conduct experiments to evaluate and analyze feasibility, as well as the challenges of the design, through scenarios varying in distance, transmission frequency, and data length.

This paper reports the designing and numerical analysis of dense wavelength-division multiplexed (DWDM) transmission in an integrated passive optical network (PON)-free-space optics (FSO) system employing modified on–off keying (OOK)/digital-pulse position modulation schemes. The transmission performance has been analyzed under inter-channel crosstalk, noise errors, and weak and strong atmospheric turbulence effects for both modulation schemes. The DWDM system uses eight channels with a wavelength spacing of 0.8 nm, and each channel transmits a data rate of 2.5 Gbps for both the considered modulation formats. The results demonstrate that the DWDM channels are degraded due to inter-channel crosstalk, whereas the FSO transmission is limited as a result of atmospheric turbulence loss. The numerical results show that the proposed modulation scheme better than OOK modulation and exhibits 0.2–3 dB lower power penalty than OOK transmission. [ABSTRACT FROM AUTHOR]

Currently, wireless communication systems that use radio frequency are commonly deployed, for example, mobile communication systems, satellite systems, and the Internet of Things (IoT) systems. Based on their easy installation, wireless communication systems have benefits over other wired communication systems. However, using high frequencies to transfer data via wireless communication can hold significant risks for human health. Several researchers have studied this topic using visible light instead of Radio Frequency (RF) waveforms in communication systems. Many potential approaches are relevant in this regard, i.e., visible light communication, light fidelity, free-space optical, and optical camera communication. Artificial intelligence is also influencing the future of industry and people and is used to solve complex problems, create intelligent solutions, and replace human intelligence as the driving force behind emerging technologies such as big data, smart factories, and the IoT. In this paper, we proposed the architecture of the MIMO C-OOK (Multiple-Input Multiple-Output Camera On–Off Keying) scheme, which uses a convolutional neural network for light-emitting diode detection and a deep learning neural network for threshold predictions considering long-distance communication and mobility support. Our suggested method aimed to improve the performance of the traditional camera on–off keying scheme by increasing data rate, communication distance, and low bit error rate. Our suggested technique may achieve a communication distance of up to 22 m with a low error rate when considering the mobility impact (2 m/s, i.e., walking velocity) by controlling the exposure time, focal length, and employing Forward Error Correction code. [ABSTRACT FROM AUTHOR]

This paper presents a wireless kitchen fire prevention system that can detect and notify the fire risk caused by gas stoves. The proposed system consists of two modules. The sensor module detects the concentration of carbon dioxide (CO 2 ) near the gas stove and transmits the monitoring results wirelessly. The alarm module, which is placed in other places, receives the data and reminds the user of the stove status. The sensor module uses a cost-efficient electrochemical CO 2 sensor and embeds an in situ algorithm that determines the status of the gas stove based on the measured CO 2 concentration. For the wireless communication between the modules, on-off keying (OOK) is employed, thereby achieving a longer battery lifetime of the alarm module, low cost, and simple implementation. To increase the lifetime further, a wake-up function based on passive infrared (PIR) sensing is employed in the alarm module. Our system can successfully detect the on state of the stove within 40 s and the off state within 200 s. Thanks to the low-power implementation, in situ algorithm, and wake-up function, the alarm module's expected battery lifetime is extended to about two months. [ABSTRACT FROM AUTHOR]

This work experimentally demonstrates for the first time the practical feasibility of a freeform multipath lens (MPL) for optical wireless communications (OWC). The MPL is able to increase the eye safety laser power limit. Our transmitter is laser class 1M and features 190 mW optical output. We transmit 1.289 Gbit/s on-off keying (OOK) data and achieve a bit error ratio (BER) of 10−10 for an optical receiver power of −31.2 dBm. The link range is more than 5 m, depending on the targeted BER. We discuss the pros and cons of MPLs and compare them with diffusers. [ABSTRACT FROM AUTHOR]

Although Successive Interference Cancellation (SIC) decoding is widely adopted in Nonorthogonal Multiple Access (NOMA) schemes for the recovery of user data at acceptable complexity, the imperfect SIC would cause Error Propagation (EP), which can severely degrade system performance. In this work, we propose an SIC-free NOMA scheme in pulse modulation based Visible Light Communication (VLC) downlinks, including two types of users with different data rate requirements. Low bit-rate users adopt on-off keying, whereas high bit-rate ones use Multiple Pulse Position Modulation (MPPM). The soft decision decoding scheme is exploited by high bit-rate users to decode MPPM signals, which could fundamentally eliminate the detrimental effect of EP; the scheme is also easier and faster to execute compared with the conventional SIC decoding scheme. Expressions of the symbol error rate and achievable data rate for two types of users are derived. Results of the Monte Carlo simulation are provided to confirm the correctness of theoretical results.

The existing radar-communication coexistence (RCC) waveform design based on chirp signal causes the increase of the complexity in the communication receiver, and multi-dimensional reuse also introduces more interference, leading to the deterioration of dual function performance. In this paper, a frequency division RCC system with on-off keying (OOK) based on frequency modulated continuous wave is designed for near sensors wake-up or low rate broadcast. The RCC signal has the fixed whole band and the variable sub-bands for radar signal and communication signal. We propose a two-stage envelope detection (TSED) scheme by extracting data from the frequency difference component of the two signals at the receiver without generating local radio frequency signal or using a mixer. By flexibly regulating the frequency band of two signals, the anti-interference ability of TSED can be further improved. In radar system, we perform small frequency hopping (FH) on radar signal to realize the full use of the whole band, and propose a scheme of abnormal peak detection and elimination (APDE) to eliminate the chirp interference. The simulation results show that the signal-to-interference ratio of TSED scheme for the RCC waveform can be respectively enhanced by 6 dB and 2 dB if compared with that of conventional envelope detection and coherent demodulation with a bit error rate of 10−5. Besides, The APDE scheme based on small FH reduces the range sidelobe by 20 dB and completely eliminates the added in-band interference. [ABSTRACT FROM AUTHOR]

Direct-detection on-off keying (DD-OOK) weakly-coupled multicore fiber (WC-MCF) systems impaired by intercore crosstalk (ICXT) and laser phase noise are investigated numerically and experimentally. This is performed for systems with a product between the bit rate and the absolute value of the skew between cores much larger than one. It is shown that the phase noise increases the instantaneous ICXT power fluctuations. The standard deviation of the short-term average ICXT (STAXT) power induced by the phase noise depends on the product between the laser linewidth and the absolute value of the skew between cores (linewidth × $|$ skew $|$). When linewidth × $|$ skew $|$ $\gg$ 1, typical of distributed feedback (DFB) lasers (linewidth in the few MHz range) and MCFs with skew in the $\mu$ s range, the decrease of the standard deviation of the STAXT power induced by the phase noise is 5 dB per decade of linewidth × $|$ skew $|$ increase. For linewidth × $|$ skew $|$ $\ll$ 1, typical of external cavity lasers (ECLs) and DFB lasers, and MCFs with skew of a few ns, the standard deviation of the STAXT power remains almost unaffected by the phase noise. Experimental results show that, compared with low linewidth ECLs, 10 Gb/s DD-OOK WC-MCF systems using DFB lasers as optical sources in the interfering cores and skew in the range between 2.4 ns and 5.4 ns, may require an additional ICXT margin up to 8 dB for a given outage probability. The additional ICXT margin and the lower amplitude of the STAXT power fluctuations observed experimentally for DFB lasers suggest that the level of the fluctuations of the STAXT power may be an inadequate system performance indicator. The dependence of the outage probability on the interfering core count is also investigated experimentally. It is shown that, for systems with bit rate × $|$ skew $|$ $\gg$ 1, the outage probability only depends on the total ICXT power and not on the interfering core count. [ABSTRACT FROM AUTHOR]

Over the last few years, free space optical communication (FSO) has emerged as a viable alternative to radio frequency communication. It provides a promising high-speed pointto-point communication solution. However, atmospheric absorption, scattering and turbulence degrade wireless optical communication significantly, lowering device efficiency. The attenuation of signals due to the above atmospheric reasons is another major factor that affects device efficiency. The atmospheric turbulence conditions are observed implemented into different models of FSO systems, such as Single Input Single Output (SISO), Multiple Input Multiple Output (MIMO), Wavelength Division Multiplexing MIMO (WDM-MIMO) and proposed model Double Multiple Input Multiple Output (DMIMO) using the Gamma-Gamma model for a variety of reasons. The OptiSystem 7.0 software was used to run simulations to study how various weather conditions (clear, haze and fog) affected the performance of the channel. Simulation results show that implementing Double Multiple Input Multiple Output (DMIMO) techniques for FSO systems provides high quality factor for various ranges while still achieving accurate transmitted data at the receiver side. In the presence of atmospheric turbulence conditions such as clear air, haze and fog, performance improvements signal power levels, quality factor and link distance range have been demonstrated. [ABSTRACT FROM AUTHOR]

In this study, we built a single photon avalanche diode (SPAD) receiver based underwater wireless optical communication (UWOC) system. The bit error rate (BER) and signal-to-noise ratio (SNR) performance of UWOC with different distances and data transmission rates were obtained. Based on the water attenuation coefficient of 0.12 m-1, a series of neutral density (ND) filters were exploited to attenuate the light output power from the blue laser diode (LD) to simulate the long distance UWOC. The maximum estimated distances of 144 m and 117 m with corresponding BERs of 1.89 × 10-3 and 5.31 × 10-4 at data transmission rates of 500 bps and 2 Mbps were acquired in UWOC system using on-off keying (OOK) modulation scheme, respectively. Furthermore, we compared the differences between free-space and underwater channels, and a divergence angle of ~1.02 mrad was measured experimentally at a distance of 50 m in the free space. The long UWOC distances obtained in this study partly benefit from high sensitivity SPAD, the small laser divergence angle and low light attenuation. This study provides an approach to achieve long distance UWOC using SPAD.

In the paper, we present and investigate an integrated wavelength-division-multiplexing (WDM) free space optical (FSO) fiber access network for 51 km long-reach connection. Here, the proposed network architecture also can mitigate Rayleigh backscattering (RB) interferometric beat noise. We employ symmetric 4 × 10 Gbit/s on-off keying (OOK) WDM-FSO downstream and upstream wavelengths for demonstration. According to the simulated and experimental results, the free space transmission length of 400 to 940 m can be achieved based on various WDM-FSO downstream signals and their corresponding power budget, when the wavelengths are without optical amplification.

Recent years have witnessed the conceptualization and development of light-to-camera communication (LCC). Various innovative modulation schemes are designed for throughput improvement. Nevertheless, the fundamental limits of LCC itself are still unknown from a theoretical perspective. In this paper, we present the LCC channel model to shed light on a question: how to improve the system performance under identical conditions of transmitting/receiving device and modulation scheme. We reveal the channel parameters of LCC that affect the formation of the signal layer and provide a design guideline for increasing the symbol rate. Moreover, we improve the demodulation performance by sampling judging points from the separated signal layer instead of detecting the widths of bands in capture images. To enhance the signal-to-noise ratio, we propose a short-time linear regression algorithm to filter out the noise from the signal layer. We build a hardware prototype with the simple ON-OFF keying to demonstrate the proposed channel model under various experiment settings. The results show that the system throughput reaches 8.2 kbps with a symbol rate of 25 kBd. We believe our techniques for symbol rate increasing and demodulation improvement can help other LCC systems improve their performance.

This paper evaluates the practically achievable best error performance obtained from a dimmable visible light communication (VLC) system that conveys information using binary modulations, such as on-off keying (OOK). As compared to previous studies that address the ideal performance of dimmable VLC systems only over reliable channels with arbitrarily small error probability, this paper presents the best achievable error probability of various configurations with the dimming targets, signal quality, and data rate. The numerical results establish the ultimate decoding error performance targeted for dimmable VLC systems and are expected to provide a practical guideline for the enhanced VLC system design. [ABSTRACT FROM AUTHOR]

Terahertz (THz) communication is a promising technique for chip-to-chip communication and wireless personal area networks. In this paper, we present an experimental study and design to realize such THz communication systems. We develop two different chip sets for on-off-keying (OOK) modulation based THz transceivers which include carrier generators, modulators, THz amplifiers, and baseband amplifiers. Specifically, the first chip set integrates the circuit blocks for the OOK modulation without the THz amplifier for short-range communication. In addition, the second chip set design includes the THz amplifier modules to extend the coverage of transmission. For these two chip sets, we experimentally demonstrate the feasibility of the wireless communication at THz frequency bands and assess performance using the bit error rate (BER) analysis. We estimate the BER by calculating the signal-to-noise ratio (SNR) based on the eye diagram and compare with actual BER measurements and Monte Carlo simulations. We also address the impact of the distance, the transmit power, and the data rate for the proposed THz transceivers based on the link budget analysis, and confirm the accuracy of the derived BER expression. [ABSTRACT FROM AUTHOR]

Currently, wireless communication systems that use radio frequency are commonly deployed, for example, mobile communication systems, satellite systems, and the Internet of Things (IoT) systems. Based on their easy installation, wireless communication systems have benefits over other wired communication systems. However, using high frequencies to transfer data via wireless communication can hold significant risks for human health. Several researchers have studied this topic using visible light instead of Radio Frequency (RF) waveforms in communication systems. Many potential approaches are relevant in this regard, i.e., visible light communication, light fidelity, free-space optical, and optical camera communication. Artificial intelligence is also influencing the future of industry and people and is used to solve complex problems, create intelligent solutions, and replace human intelligence as the driving force behind emerging technologies such as big data, smart factories, and the IoT. In this paper, we proposed the architecture of the MIMO C-OOK (Multiple-Input Multiple-Output Camera On–Off Keying) scheme, which uses a convolutional neural network for light-emitting diode detection and a deep learning neural network for threshold predictions considering long-distance communication and mobility support. Our suggested method aimed to improve the performance of the traditional camera on–off keying scheme by increasing data rate, communication distance, and low bit error rate. Our suggested technique may achieve a communication distance of up to 22 m with a low error rate when considering the mobility impact (2 m/s, i.e., walking velocity) by controlling the exposure time, focal length, and employing Forward Error Correction code.

We experimentally evaluate the high-speed on–off keying (OOK) and four-level pulse amplitude modulation (PAM4) transmitter's performance in C-band for short-reach optical interconnects. We demonstrate up to 100 Gbaud OOK and PAM4 transmission over a 400 m standard single-mode fiber with a monolithically integrated externally modulated laser (EML) having 100 GHz 3 dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable 800 GbE client-side links based on eight, and even four, optical lanes for optical interconnect applications. We study the equalizer's complexity when increasing the baud rate of PAM4 signals. Furthermore, we extend our work with numerical simulations showing the required received optical power (ROP) for a certain bit error rate (BER) for the different combinations of the effective number of bits (ENOB) and extinction ratio (ER) at the transmitter. We also show a possibility to achieve around 1 km dispersion uncompensated transmission with a simple decision feedback equalizer (DFE) for a 100 Gbaud OOK, PAM4, and eight-level PAM (PAM8) link having the received power penalty of around 1 dB. [ABSTRACT FROM AUTHOR]

This paper presents a wireless kitchen fire prevention system that can detect and notify the fire risk caused by gas stoves. The proposed system consists of two modules. The sensor module detects the concentration of carbon dioxide (CO2) near the gas stove and transmits the monitoring results wirelessly. The alarm module, which is placed in other places, receives the data and reminds the user of the stove status. The sensor module uses a cost-efficient electrochemical CO2 sensor and embeds an in situ algorithm that determines the status of the gas stove based on the measured CO2 concentration. For the wireless communication between the modules, on-off keying (OOK) is employed, thereby achieving a longer battery lifetime of the alarm module, low cost, and simple implementation. To increase the lifetime further, a wake-up function based on passive infrared (PIR) sensing is employed in the alarm module. Our system can successfully detect the on state of the stove within 40 s and the off state within 200 s. Thanks to the low-power implementation, in situ algorithm, and wake-up function, the alarm module’s expected battery lifetime is extended to about two months.

Abstract The successful treatment of hearing loss depends on the individual practitioner’s experience and skill. So far, there is no standard available to evaluate the practitioner’s testing skills. To assess every practitioner equally, the paper proposes a first machine, dubbed artificial patient (AP), mimicking a real patient with hearing impairment operating in real time and real environment. Following this approach, we develop a multiple-input multiple-output auditory model that synthesizes various types of hearing loss as well as elements from psychoacoustics such as false response and reaction time. The model is then used to realize a hardware implementation, comprising acoustic and vibration sensors, sound cards, and a fanless personal computer. The AP returns a feedback signal to the practitioner upon perceiving a valid test tone at the hearing threshold analogous to a real patient. The AP is derived within a theoretical framework in contrast to many other solutions. The AP handles masked air-conduction and bone-conduction hearing levels in the range from 5 to 80 dB and from – 20 to 70 dB, respectively, both at 1 kHz. The frequency range is confined within 250 and 8000 Hz. The proposed approach sets a new quality standard for evaluating practitioners.

Visible light communication (VLC) is a secure, low-cost, and high-rate communication method. On-off keying (OOK) is one of the modulation schemes of VLC, turning each light either on or off to generate binary signals. Recently, deep learning (DL) technologies have made a series of breakthroughs for dimming in VLC system. This task is actually quite challenging for DL, since the VLC system needs to be able to support various dimming targets on account of the different preferences from users in practical applications, resulting in an optimization problem with multiple constraints. This article presents a DL framework for the dimming-aware binary VLC system, which can meet arbitrary dimming requirements by a universal neural network, named universal auto-encoder (UAE). The proposed UAE creatively utilizes a multi-branch architecture with several carefully designed concatenated patches, and a novel multi-stage training strategy for the optimization problem with multiple dimming constraints. The experiments indicate that the proposed DL approach outperforms existing techniques in terms of the average bit error rate, the satisfaction of the dimming constraints, and the robustness for imperfect optical channels. [ABSTRACT FROM AUTHOR]

In this paper, we propose adaptive channel-matched detection (ACMD) to effectively compensate channel distortions for C-band 64-Gbit/s intensity-modulation and direct-detection (IM/DD) optical on-off keying (OOK) system over a 100-km dispersion-uncompensated link. The proposed ACMD can adaptively compensate most of the link distortions based on channel and noise characteristics, which includes a polynomial nonlinear equalizer (PNLE), a decision feedback equalizer (DFE) and maximum likelihood sequence estimation (MLSE). Based on the channel characteristics, PNLE eliminates the linear and nonlinear distortions, while the followed DFE compensates the spectral nulls caused by chromatic dispersion. Finally, based on the noise characteristics, a post filter can whiten the noise for implementing optimal signal detection using MLSE. To the best of our knowledge, we present a record C-band 64-Gbit/s IM/DD optical OOK system over a 100 km dispersion-uncompensated link achieving 7% hard-decision forward error correction limit using only the proposed ACMD at the receiver side. [ABSTRACT FROM AUTHOR]

This paper presents a new on–off keying modulation circuit for a Class-E power transmitter used in high-data-rate wireless links used for powering medical implants. A circuit technique is proposed to keep the current of the RF choke of the power transmitter constant, while the transmitter turns on and off. This allows the transmitter to quickly turn on and off. To prove the feasibility of the proposed circuit, a wireless power and data transfer link based on the proposed circuit was designed and implemented. At a carrier frequency of 2.5 MHz, the measured data rate was 625 kbps, which means that a data-rate-to-carrier-frequency ratio of 25% has been achieved. The power transfer efficiency and the power delivered to the load, with a 2.37-μH transmitter coil and a 1.4-μH receiver coil separated by a 1.0-cm air gap, were measured to be 21% and 80 mW, respectively. The measured bit error rate of the link was less than 10−5. [ABSTRACT FROM AUTHOR]

Intercore crosstalk (ICXT) impaired weakly-coupled multicore fiber (MCF) systems using on-off keying (OOK) and direct-detection (DD) are experimentally assessed. The stochastic properties of the received bit amplitudes that depend on the relative propagation delay (skew) between two cores of the MCF and on the OOK bit-rate are discussed. For low skew×bit-rate ($< < $ 1): (i) the received amplitude of bits 0 or 1 of the interfered core are mainly characterized by two possible levels; (ii) when the short-term average crosstalk (STAXT) power increases (decreases), the fluctuations of the received amplitudes of bits 1 and 0 become larger (lower). For high skew×bit-rate ($>>$ 1): (i) the received amplitudes of bits 0 and 1 present a noise-like behaviour; (ii) larger fluctuations of the received amplitudes of the OOK signal may not occur only for high STAXT powers. For both low and high skew×bit-rate, it is shown that the histogram of the received amplitudes of bits 1 or 0, and the histogram of the mean and variance of these amplitudes are reasonably well characterized by Gaussian distributions. Experimental results suggest that the rule of thumb to design emerging MCF applications with higher ICXT tolerance is to use cores with skew much longer than the symbol period. [ABSTRACT FROM AUTHOR]

In this study, we built a single photon avalanche diode (SPAD) receiver based underwater wireless optical communication (UWOC) system. The bit error rate (BER) and signal-to-noise ratio (SNR) performance of UWOC with different distances and data transmission rates were obtained. Based on the water attenuation coefficient of 0.12 m−1, a series of neutral density (ND) filters were exploited to attenuate the light output power from the blue laser diode (LD) to simulate the long distance UWOC. The maximum estimated distances of 144 m and 117 m with corresponding BERs of 1.89 × 10−3 and 5.31 × 10−4 at data transmission rates of 500 bps and 2 Mbps were acquired in UWOC system using on-off keying (OOK) modulation scheme, respectively. Furthermore, we compared the differences between free-space and underwater channels, and a divergence angle of ∼1.02 mrad was measured experimentally at a distance of 50 m in the free space. The long UWOC distances obtained in this study partly benefit from high sensitivity SPAD, the small laser divergence angle and low light attenuation. This study provides an approach to achieve long distance UWOC using SPAD. [ABSTRACT FROM AUTHOR]

In the cableless seafloor observation networks (SONs), the links among network nodes rely on underwater acoustic communication (UAC). Due to the energy constraint and the high-reliability requirement of the cableless SONs, the noncoherent UAC has been a preferred choice, even though a noncoherent UAC scheme generally suffers from low spectral efficiency. In this paper, we propose a high-spectral-efficiency noncoherent UAC transmission scheme which is implemented as an orthogonal frequency-division multiplexing (OFDM) system adopting the on-off keying (OOK) modulation. To simultaneously achieve high performance at a low energy consumption, an irregular recursive convolutional code (IrCC) is employed and an accumulator (ACC) is introduced to achieve a modulation with memory at the transmitter side. The ACC enables a turbo iteration between the soft demapper called the ACC-OOK demapper and the soft decoder on the receiver side, and also reduces the decoding error floor. To account for the unknown signal-to-noise ratio (SNR), an iterative threshold estimation (ITE) algorithm is proposed to determine a proper decision threshold for the ACC-OOK demapper. The IrCC is designed to match the extrinsic information transfer (EXIT) curve of the ACC-OOK demapper, lowering the SNR threshold of the aforementioned turbo iteration. Simulations and experimental results verify the superiority of the proposed noncoherent UAC scheme over conventional ones. [ABSTRACT FROM AUTHOR]

This article presents a high energy efficiency, high-integrated, and low-power on–off keying transceiver for a 2.4 GHz industrial scientific medical band. The proposed receiver includes an input matching network, a low-noise amplifier, a novel single-to-differential envelope detector, a level shifter, cascaded baseband amplifiers, and a hysteresis comparator. The proposed transmitter includes a bias-stimulating circuit, a current-reused self-mixing voltage controlled oscillator, and a quadruple-transconductance power amplifier. Numerous proposed techniques implemented in the mentioned circuits improve the energy per bit and power efficiency. Therefore, the proposed receiver for short-distanced propagation can achieve a sensitivity of −46 dBm with a carrier frequency of 2.45 GHz and a high data rate of 2 Mbps. The proposed transmitter achieves an output power of −17 dBm with a high data rate of 20 Mbps. This work is fabricated in a TSMC 0.18 μm CMOS process and consumes 160 μW and 0.6 mW in the receiver and transmitter, respectively, from a 1.2 V supply voltage. The energy per bit of 80 pJ/bit in the receiver part and the figure of merit of 9 in the transmitter part are better than those of existing state-of-the-art transceivers. [ABSTRACT FROM AUTHOR]

Wireless technologies that are based on radio frequencies are currently widely used, with numerous applications around the world. However, they pose some disadvantages to human health. High frequencies can have potentially harmful effects on children, hospital patients, and even healthy people if the signal power exceeds the permitted standard. Conversely, the use of visible light for data transmission is a trend that presents new options, including optical wireless communication, optical camera communication, and visible light communication. This paper proposes a modulation scheme based on on-off keying in the time domain, which is applied to a monitoring system using optical camera communication. This scheme has various compatible supports for the global-shutter camera and rolling-shutter camera, which are popular commercially available cameras. Furthermore, this scheme facilitates a low-cost monitoring system. By using small light-emitting diodes (LEDs) and controlling the exposure time in a single camera, the camera, as a receiver, can simultaneously detect signals from up to 10 sensor devices in different positions at a maximum distance of up to 50 m, with a low error rate. [ABSTRACT FROM AUTHOR]

We experimentally evaluate the high-speed on–off keying (OOK) and four-level pulse amplitude modulation (PAM4) transmitter’s performance in C-band for short-reach optical interconnects. We demonstrate up to 100 Gbaud OOK and PAM4 transmission over a 400 m standard single-mode fiber with a monolithically integrated externally modulated laser (EML) having 100 GHz 3 dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable 800 GbE client-side links based on eight, and even four, optical lanes for optical interconnect applications. We study the equalizer’s complexity when increasing the baud rate of PAM4 signals. Furthermore, we extend our work with numerical simulations showing the required received optical power (ROP) for a certain bit error rate (BER) for the different combinations of the effective number of bits (ENOB) and extinction ratio (ER) at the transmitter. We also show a possibility to achieve around 1 km dispersion uncompensated transmission with a simple decision feedback equalizer (DFE) for a 100 Gbaud OOK, PAM4, and eight-level PAM (PAM8) link having the received power penalty of around 1 dB.

Wireless technologies that use radio frequency (RF) waveforms are common in wireless communication systems, such as the mobile communication, satellite system, and Internet of Things (IoT) systems. It is more advantageous than wired communication because of the ease of installation. However, it can negatively impact human health if high frequencies are used to transmit data. Therefore, researchers are exploring the potential of optical wireless communication as an alternative, which uses the visible light bandwidth instead of RF waveforms. Three possibilities are being investigated: visible light communication, light fidelity, and optical camera communication. In this paper, we propose a multiple-input multiple-output modulation scheme using a light-emitting diode (LED) array, which is applicable to the IoT system, based on on–off keying modulation in the time domain. This scheme is compatible with the two popular types of camera in the market, rolling shutter cameras and global shutter cameras, as well as the closed-circuit television camera, which is used in factories, buildings, etc. Despite the small size of the LED array, implementing this scheme with 10 links in different positions at a communication distance of 20 m is possible for efficient performance (low error rate) by controlling the exposure time, shutter speed, focal length, channel coding and applying the matched filter.

An overall bit rate of 625 Mb/s real-time multi-access VLC system is presented in this paper. In order to decrease the effect of ambient light and deal with the non-linearity of LED, we propose a new algorithm to get orthogonal codes which is suitable for OOK modulation. By employing a single white LED and three photo diodes, three users are provided access to the VLC system individually at the same time. A data frame and CRC32 are adopted to realize a reliable and continuous data interaction between Ethernet and VLC system. All the numerical calculations are implemented by FPGAs so as to provide a practical high-speed transmission. [ABSTRACT FROM AUTHOR]

The probabilistic shaping scheme by Honda and Yamamoto (2013) for polar codes is used to enable power-efficient signaling for on–off keying (OOK). As OOK has a non-symmetric optimal input distribution, shaping approaches that are based on the concatenation of a distribution matcher followed by systematic encoding do not result in optimal signaling. Instead, these approaches represent a time-sharing scheme, where only a fraction of the codeword symbols is shaped. The proposed scheme uses a polar code for joint distribution matching and forward error correction which enables asymptotically optimal signaling. Numerical simulations show a gain of 1.8 dB compared to uniform transmission at a spectral efficiency of 0.25 bits/channel use for a blocklength of 65 536 bits. [ABSTRACT FROM AUTHOR]

According to control performance requirement of Antenna Interface Standards Group(AISG) 2.0 protocol to Time Division Duplex-Tower Mounted Amplifier(TDD-TMA), a design scheme of TMA control unit was presented. An on-off keying(OOK) communication module employing logarithmic amplifier and RF switch were designed, and they effectively solve the problem of sending signal loop back to the receiver. One configurable current-alarm circuit based on current negative feedback was designed to provide exact control on alarm-current. AISG protocol stack design, TMA fault detection and processing module were also given respectively. The test results show that this design scheme matches the communication and control requirement of AISG protocol well, presents sophisticated state monitoring function, and also features its current-alarm function when AISG communication failure occurs. [ABSTRACT FROM AUTHOR]

Free-space optical communication links operating over lognormal turbulence channels using on-off keying (OOK) are studied in this paper. Such systems can suffer from irreducible error floors that result from the use of demodulation with fixed and unoptimized detection thresholds. The resulting error floors are analyzed for the general case of low- and high-state offsets (i.e., finite extinction ratios). An electrical signal-to-noise ratio (SNR) optimized detection system is applied. The system uses the electrical SNRs to implement adaptive detection thresholds and eliminate the error floors. The system can accommodate operation with finite extinction ratios, as it uses the method of moments and maximum likelihhod estimation techniques to estimate the low- and high-state offsets and electrical SNR. Numerical results show that the SNR gap between the electrical-SNR-optimized detection system and the adaptive detection system is 2.3 dB at a bit-error rate of 10-5 without a state offset. The SNR gap increases to 4.5 dB with a state offset of ξ=0.2 .