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An optical wireless communication technology subset includes visible light communication (VLC) that enhances resource usage by enabling high-speed data transmission with visible light while illuminating. Cooperative communication uses the system's users as relay stations to enhance the lower energy usage, transmission quality and boost network performance. In this paper, the decode-and-forward relaying technique for L pulse position modulated (L-PPM) modulated cooperative VLC (C-VLC) systems is presented. The signals received from cooperative broadcasts are combined at the receiving node using the maximum ratio combining (MRC) technique. The suggested system is thoroughly studied for a multi-user scenario, followed by scenarios with two and three users. In this paper, the bit error probability (BEP) of L-PPM modulated C-VLC system is calculated for both perfect and imperfect channel state information (CSI). To validate the generated analytical BEP results, simulation results are shown and contrasted with direct transmission and on–off keying (OOK) modulated C-VLC systems. [ABSTRACT FROM AUTHOR]

This paper presents a high-speed V-band on-off keying (OOK) modulator in 65 nm CMOS based on distributed transmission lines architecture. The high-speed operation of the proposed OOK modulator is attained by distributing a single large switching transistor into smaller units. The effects of parasitic capacitances of each small switch are mitigated by series inductors, forming an artificial transmission line. The switch size and the number of stages are optimized for a reasonable balance between insertion loss and isolation. Small signal measurement of the OOK modulator reveals 3.8 dB insertion loss and 20.5 dB isolation at 60 GHz, with <5 dB insertion loss and >16 dB on-off ratio from 50 GHz to 70 GHz. Testing with a modulation setup shows the modulator is fully functional up to 5 Gbps at a 60 GHz carrier. Limitations of the test setup prevent modulation testing at >5 Gbps. The fabricated modulator does not consume any DC power and has an active footprint of 0.025 mm2. [ABSTRACT FROM AUTHOR]

Visible Light Communication (VLC) is one of the emerging technologies of Optical Wireless Communications (OWCs) in finding sustainable solutions for the spectrum crunch of beyond 5G access technologies. This research work introduces the NeoCommLight system, a healthcare communication architecture for Neonatal Intensive Care Units (NICU) based on visible light communication, which offers a promising solution for RF-restricted areas and addresses the challenges posed by spectrum crunch and health concerns associated with traditional radio communication technologies. To demonstrate the feasibility and practicality of the proposed system, a prototype design is presented, accompanied by implementation details. Furthermore, the performance analysis of the NeoCommLight system is conducted, shedding light on crucial aspects such as communication delay, transmitter-to-receiver distance, variations in transmitter angle concerning the Line of Sight (LoS) axis, and the impact of diffraction caused by a knife edge obstacle placed between the transmitter and receiver. The performance analysis of the system showed that it could transmit data at a maximum data rate of 3 Mbps at a distance of 5 cm. The system could transmit data at a data rate 800 Kbps to a maximum distance of 2 meters.

Free space optics is a light-wave communication technology that operates in the near-infrared region of the electromagnetic spectrum (about 700–1675 nm) and uses atmospheric channel as the transmission medium for both inter-satellite and terrestrial networks. However, the operational proficiency of free space optical communication system is highly affected by channel dynamics which cause signal attenuation that results in short link range. To master these shortcomings different methods have been suggested in the literature, from transceiver design and diverse channel models to adaptive algorithms. In this manuscript, the design and performance investigation of free space optical system has been carried out for three optical transmission windows; 850, 1310 and 1550 nm by means of on-off keying digital modulation technique. The system analysis has been done taking bit error rate, quality factor and received optical power as the performance metrics. Their variation pattern with respect to varying link parameters such as range, transmitted optical power and beam divergence has been investigated. In addition, the observations made are well validated with thorough mathematical justification. [ABSTRACT FROM AUTHOR]

Free-space optical (FSO) communication system provides several advantages over radio frequency (RF) system offering high bandwidth, low cost, small space requirements and more secure transmission which is free from Electromagnetic Interference (EMI). However, when the transmitted light signal passes through the atmosphere it experiences attenuation and fluctuations due to atmospheric turbulence. This paper analyzes the bit error rate (BER) performance of FSO communication systems under strong atmospheric turbulence for on-off keying (OOK), binary phase-shift keying (BPSK), differential phase shift keying (DPSK), quadrature phase shift keying (QPSK) and 8-phase shift keying (8-PSK) for link distances of 500, 1,000, 1,500 and 2,000 m. The probability density function (pdf) of the received irradiance is modelled using the gamma-gamma distribution model. It is found that the system exhibits the best BER performance and compensates the lowest power penalty at BER of 10 - 9 for BPSK modulation compared with other modulation techniques which makes BPSK more appropriate to be used with FSO turbulent system. [ABSTRACT FROM AUTHOR]

Single-photon avalanche diodes (SPADs) capable of single photon detection are promising optical sensors for use as receivers in optical wireless communication (OWC) systems. In SPAD-based receivers, the intersymbol interference (ISI) effect caused by dead time is an important drawback that limits performance. In this paper, we propose two novel SPAD operation modes to reduce the ISI effect in SPAD-based OWC. To validate the feasibility of these two modes, we designed a free-running SPAD front-end circuit with post-layout transient simulation results and some measurements to show its function and performance. This SPAD circuit is improved by a novel mixed passive-active quench and reset front-end circuit that achieves a very short dead time. Based on the traditional free-running mode, we design the clock-driven mode and time-gated mode to reduce the ISI effect through time-controlled operating signals. To accurately evaluate these three modes, we develop a new simulation system to assess the ISI effect in On-Off Keying (OOK) modulated communication. The simulation results demonstrate that the clock-driven mode and time-gated mode receivers can improve the bit error rate (BER) performance in low data rate communication and high data rate high optical power communication, respectively. Moreover, compared to the free-running mode, the two proposed time-controlled modes achieve higher data rate communication and better noise tolerance ability in SPAD-based OWC.

Inthe work, we study and express a new wavelength-division-multiplexing passive optical network (WDM-PON) architecture with fiber fault protection. The designed optical network unit (ONU) module and periodic spectrum of 2 × N array waveguide grating (AWG) are applied to produce the self-protected mechanism. Here, we employ the free space optical communication (FSO)- and fiber-based connection between two adjacent ONUs to achieve signal relink. Moreover, the corresponding signal performances of downstream and upstream are also analyzed and discussed.

Due to the exponential growth of mobile devices and wireless services, a huge demand for radio frequency has increased. The presence of several frequencies causes interference between cells, which must be minimized to get the lower bit error rate (BER). For this reason, it is of great interest to use visible light communication (VLC). This paper suggests a VLC system that decreases the BER with applying a new LED distribution with a hexagonal shape using different techniques: on–off keying (OOK), quadrature amplitude modulation, and frequency reuse concept to mitigate the interference between the reused frequencies inside the hexagonal shape. The BER is measured in two scenarios line of sight (LoS) and non-line of sight for each technique that we used. The recommended values of BER in the proposed model for soft frequency reuse in case of LoS at 4, 8, and 10 dB signal to noise ratio, are 3.6 × 10–6, 6.03 × 10–13, and 2.66 × 10–18, respectively. [ABSTRACT FROM AUTHOR]

We consider a free-space optical (FSO) communication link for packet-based transmissions over a turbulence fading channel. The modulation format is on-off keying (OOK) and a unique-word (UW) composed by a known synch pattern is periodically inserted in the data stream to identify the start of frame. Since an avalanche photo-diode (APD) is used for direct detection of the OOK symbols, the photocurrent signal provided by the APD is plagued by a mixture of thermal and shot noise with signal-dependent power. Our goal is the detection of the UW position in the received stream, along with the estimation of the unknown channel attenuation and noise variances. The aforementioned problem has recently been studied by ignoring any information conveyed by data symbols surrounding the UW. In this work, further investigation is conducted in order to determine the maximum likelihood (ML) solution that, in addition to the UW, exploits all the information-bearing symbols belonging to the observation window. The relevant Cramér-Rao bound (CRB) is also evaluated to establish the ultimate accuracy achievable in the estimation process. Since the true ML estimator leads to a computationally intractable multi-dimensional optimization problem, we develop suitable approximations that enable accurate frame synchronization with affordable complexity. We also present an iterative solution to refine the channel and noise power estimates provided by the UW detection procedure. Numerical simulations demonstrate the superiority of the proposed synchronization and estimation schemes with respect to existing alternatives. [ABSTRACT FROM AUTHOR]

Medical applications have driven many areas of engineering to optimize diagnostic capabilities and convenience. In the near future, wireless body area networks (WBANs) are expected to have widespread impact in medicine. To achieve this impact, however, significant advances in research are needed to cope with the changes of the human body’s state, which make coherent communications difficult or even impossible. In this paper, we consider a realistic noncoherent WBAN system model where transmissions and receptions are conducted without any channel state information due to the fast-varying channels of the human body. Using distributed reception, we propose several symbol detection approaches where on-off keying (OOK) modulation is exploited, among which a supervised-learning-based approach is developed to overcome the noncoherent system issue. Through simulation results, we compare and verify the performance of the proposed techniques for noncoherent WBANs with OOK transmissions. We show that the well-defined detection techniques with a supervised-learning-based approach enable robust communications for noncoherent WBAN systems. [ABSTRACT FROM AUTHOR]

The atmospheric scintillation effect on free space optics (FSO) communication link is very detrimental and the bit error rate (BER) reliability of the FSO link has suffered for it. However, by applying the aperture averaging scheme, the detrimental effect of the scintillation is reduced and the performance of BER is improved significantly. In this letter, a higher order multiple input multiple output (MIMO)-based mid-wave infrared (MWIR) (4000 nm) and short-wave infrared (SWIR) (1550 nm) FSO communication wavelengths, the link distance is 5 km and modulation technique, on-off keying (OOK), have been considered. For applying the aperture averaging technique, different diameter aperture size has been considered like 10 cm., 15 cm., and 20 cm. As the aperture size is increased, as a result, the system performance in terms of BER is improved irrespective of different diversity MIMO scheme. In the very clear visibility, clear visibility, and haze weather conditions, the MWIR FSO link shows the better BER performance, whereas, in case of foggy weather condition, the MWIR link works properly but SWIR wavelength link fails in the same visibility condition, same link distance, signal-tonoise ratio (SNR), aperture diameters and MIMO diversity schemes. [ABSTRACT FROM AUTHOR]

In this work, we present a wireless energy-efficient fully integrated amplitude shift keying (ASK) transmitter (TX) array at 220 GHz. Each TX cell consists of an oscillator, a modulation switch, an on-chip antenna, and baseband amplifiers. The oscillator uses a harmonic generation technique that is optimized for maximum output power and efficiency. The ASK scheme is used for data modulation and is implemented with a fast switch that does not consume any dc power. Three of these TX cells are coherently coupled together to increase the signal-to-noise ratio (SNR) and, hence, the data rate. This also enables the possibility of having a four-level spatial ASK modulation. Fabricated in a 55-nm SiGe bipolar complementary metal oxide semiconductor (BiCMOS) process, the array dissipates 165.2 mW of dc power and generates 4.2-dBm effective isotropic radiated power (EIRP). The chip demonstrates a 20-Gb/s data transmission rate with on-off keying (OOK) modulation at a 28-cm distance using low-cost Teflon lenses. The measured energy efficiency of the array is 8.26 pJ/bit. To the best of our knowledge, this work demonstrates the best energy efficiency among TX arrays at this frequency range. [ABSTRACT FROM AUTHOR]

Fast and reliable synchronization in free-space optical (FSO) communications is a crucial task that has received little attention so far. Since in these applications the data rate is much higher than in traditional radio-frequency (RF) systems, novel technological constraints may arise in the design of the synchronization algorithms, as for example the need to operate at symbol rate instead with an oversampled data stream. In this work, we consider an FSO link and investigate the problem of channel estimation, symbol timing recovery and frame detection using a known synch pattern. The modulation format is on-off keying (OOK) and the received signal is plagued by a mixture of thermal and shot noise. By applying the least-squares criterion, we derive a novel synchronization scheme that can jointly retrieve all the unknown parameters using symbol-spaced samples. Although designed without taking the noise statistics into account, the estimator performance is assessed in a realistic scenario where shot noise is present. Comparisons are made with the relevant Cramér-Rao bound for the joint estimation of the synchronization parameters and signal-dependent noise variances. Numerical simulations and complexity analysis indicate that the resulting scheme performs satisfactorily with an affordable processing load. Hence, it represents a promising solution for fast synchronization in high-speed FSO communications. [ABSTRACT FROM AUTHOR]

An active probe and microstimulator SoC for interfacing with peripheral nerves is presented. It performs 64-channel artifact-tolerant neural recording, cuff imbalance compensation by impedance sensing, and neurostimulation for the closed-loop operation. Each recording channel is a second-order opamp-less $\Delta \Sigma $ ADC that consumes 140 nW and occupies 0.01 mm2 area in 130 nm CMOS. The single-loop $\Delta \Sigma $ architecture achieves second-order noise shaping with two passive integrators. To the best of our knowledge, this yields the lowest power and area of any second-order $\Delta \Sigma $ ADC and the lowest FOM (fJ/conv. step) of any passive second-order $\Delta \Sigma $ ADC (27 fJ/conv. step). The SoC uniquely performs multi-modal input signal recording: voltage (for neural recording) and current (for impedance sensing) are measured concurrently using frequency multiplexing. The SoC also features a 60 MHz energy-efficient inductive powering link and a 600 MHz RF data communication link. The prototype is validated in vivo in the rat sciatic nerve for electroneurogram (ENG) sensing and the correction of impedance-imbalance in cuff electrodes. [ABSTRACT FROM AUTHOR]

In this paper, we propose and experimentally demonstrate a receiver-side electronic dispersion compensation (EDC) algorithm for direct-detection 56 Gbit/s on-off keying signal in C-band over 20 km dispersion-uncompensated standard single-mode fiber transmission. The proposed receiver-side EDC algorithm includes the feed-forward equalizer, post noise-whitening filter and modified iterative detection algorithm, which is originally used in spectrally efficient frequency division multiplexing systems for inter-carrier interference cancellation. Only with the aid of the proposed EDC algorithm for the compensation of power fading effect caused by bandwidth limit and chromatic dispersion, bit-error ratio below the 7% hard-decision forward error correction limit is achieved. This scheme can keep the system cost-effective and flexible, showing potentials for optical interconnects.

In order to provide a novel analytically traceable free space optics (FSO) channel model for describing turbulence based irradiance fluctuations, following basic scintillation theory principles, we have derived closed-form expression for probability density function (PDF) of a new statistical Gamma--Chi-square model. Further, capitalizing on provided model, error performances of FSO system over on--off keying (OOK) transmission scheme both in the presence of atmospheric turbulence and misalignment fading (pointing error) is investigated. For both cases, the average bit error rate (ABER) at the receiving side of the system is determined in an analytically closed form. The results are graphically presented in order to analyze the impact of different levels of turbulence, as well as other relevant parameters, on the quality of the received signal in the OOK modulated FSO system. [ABSTRACT FROM AUTHOR]

A low-power-consumption single-arm-driven silicon (Si) Mach-Zehnder modulator (MZM) operated at C-band (λ =1550 nm) for non-return-to-zero on-off-keying (NRZ-OOK) transmission beyond 50 Gbit/s over 10-km single-mode fiber (SMF) and dispersion-shift fiber (DSF) is demonstrated to guarantee the IEEE 802.3bs standardized 400GBASE-FR8/LR8 operation. The Si MZM exhibits asymmetric waveguide arms and 2-mm-contact-length phase shifter under carrier depletion operation in its p-n junction, which is DC biased as low as 2 V to provide a low Vπ L product of 0.909 V⋅cm. For the error-free transmission of the NRZ-OOK data-stream, the single-arm-driven Si MZM supports the highest data rates of 53, 53 and 50 Gbit/s over optical back-to-back, 2-km SMF and 10-km DSF transmissions, respectively. The 50-Gbit/s receiving power penalties are respectively 0.2 and 0.25 dB after 2-km SMF and 10-km DSF propagation. [ABSTRACT FROM AUTHOR]

Free space optical (FSO) communication links offers an emerging alternative to RF communication links because of high speed, secure and cost-effective options to provide the last mile connectivity to end-users. They may be deployed for quick network access temporarily during link failure and natural disaster. This paper focusses on the performance of FSO communication link impaired with strong turbulence and atmospheric attenuation added through varying climatic conditions. A closed-form expression for outage probability is derived to evaluate the performance under different levels of atmospheric attenuation and turbulence strengths. The mathematical analysis clearly shows inimical effects added by atmospheric attenuation over the performance of the communication link. The impact of wavelength diversity on the outage probability of such a link is analyzed with three carrier wavelengths 1550 nm, 1310 nm and 850 nm. The simulation results with wavelength diversity for different atmospheric attenuation levels and turbulence are plotted and analyzed. [ABSTRACT FROM AUTHOR]

In this paper, a compact and fully passive bit encoding circuit, capable of operating as a chipless radio frequency identification (RFID) tag is presented. The structure consists of novel concentric trefoil-shaped slot resonators realized using Rogers RT/duroid® 5880 laminate, occupying a physical footprint of 13.55 $\times $ 13.55 mm2. Each resonating element is associated with a particular data bit, having a 1:1 resonator-to-bit correspondence. Bit sequences are configured through introducing modifications in the geometric structure either by addition or exclusion of each nested slot resonator. Such changes manifest directly in the electromagnetic signature of the tag as presence or absence of corresponding resonant peaks. The proposed 10-bit tag offers minimized inter-resonator mutual coupling and insensitivity to changes in polarization and incident angles thereby demonstrating orientation independent functionality. Moreover, error-free encoding is achieved through stabilizing the shift in resonant frequencies for a variety of different geometric configurations and orientation of the structure. The tag operates within the license-free ultra-wideband ranging from 5.4 to 10.4 GHz, providing spectral bit capacity and bit density of 2 bits/GHz and 5.44 bits/cm2 respectively.

In this investigation, we propose and demonstrate an integrated vertical-cavity surface-emitting laser (VCSEL) and blue light emitting diode (LED) based visible light communication (VLC) system by using the decode-and-forward (DF) relay scheme indoors. The 682 nm visible VCSEL can reach 3 Gbit/s on-off keying (OOK) modulation rate for 4 m free space transmission by applying 1.25 GHz bandwidth PIN photodiode (PD). Then, the VLCVCSEL signal connects to multiple blue LEDs for broadcasting VLCLED traffic in parallel. Therefore, the maximum VLCLED rates of 775, 700, and 600 Mbit/s are obtained at the free space transmission lengths of 2, 3, and 4 m, respectively within the forward error correction (FEC) target under 4 m VLC transmission at the low detected power of 15 μW. In addition, the number of LEDs used in the DF relay VLC system depends on the practical requirement of VLCLED rate and traffic length indoors. [ABSTRACT FROM AUTHOR]

In this paper, we propose and experimentally demonstrate a receiver-side electronic dispersion compensation (EDC) algorithm for direct-detection 56 Gbit/s on-off keying signal in C-band over 20 km dispersion-uncompensated standard single-mode fiber transmission. The proposed receiver-side EDC algorithm includes the feed-forward equalizer, post noise-whitening filter and modified iterative detection algorithm, which is originally used in spectrally efficient frequency division multiplexing systems for inter-carrier interference cancellation. Only with the aid of the proposed EDC algorithm for the compensation of power fading effect caused by bandwidth limit and chromatic dispersion, bit-error ratio below the 7% hard-decision forward error correction limit is achieved. This scheme can keep the system cost-effective and flexible, showing potentials for optical interconnects. [ABSTRACT FROM AUTHOR]

This article presents a high data rate, high-efficiency 60-GHz on–off keying (OOK) CMOS transmitter and receiver. The transmitter consists of a voltage-controlled oscillator (VCO) and a modulator. The receiver consists of a low-noise amplifier, detector, and limiting amplifier (LA) and has a compact design. An analysis of the on–off isolation of the modulator and bandwidth of the LA reveals that the proposed transformer (TF) between the modulator and the VCO can improve the on–off isolation, and the feedforward capacitor can enhance the bandwidth. Implemented in the 65-nm CMOS technology, the transmitter and the receiver consume dc powers of 12.1 and 21 mW, respectively, at 12.5 Gb/s. Moreover, they occupy core chip areas of 0.09 and 0.06 mm2, respectively. The transceiver system is constructed with on-board Yagi–Uda antennas, and it achieves 12.5 Gb/s wireless OOK data transmission for a pseudorandom binary sequence of length 27 −1 with a bit error rate of less than 10−12. The proposed transceiver system achieves an energy efficiency of 2.65 pJ/bit. [ABSTRACT FROM AUTHOR]

The average bit error rate (BER) and outage probability of circle polarization shift keying (CPOLSK) modulation in free-space optical (FSO) system operating under exponentiated Weibull (EW) distribution are studied. The closed expression of the average BER is derived by generalized Gauss–Laguerre polynomials. The analytical results show the relationship between the average BER and average signal to noise ratio (SNR) of CPOLSK modulation with the effect of aperture averaging under different turbulence strengths and it is compared with on–off keying (OOK) modulation. The relationship between the outage probability and normalized threshold SNR of CPOLSK modulation is studied as well. All the analytical results are verified by the Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

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The paper explorers Free Space Optical (FSO) communication with its flashes and corns. FSO technology is useful where the physical connection is impractical due to high cost or other considerations, and in most cases, optical data transmission is done via optical fibers, because it allows transmission over relatively large distances without alignment issues and relatively very less disturbing influences of atmosphere. But optical data transmission using fiber has also many limitations. Some limitations are removed by FSO technology, such as it provides high data rates, low power consumption, low installation cost and easily upgradable. FSO performance parameters, i.e., internal and external parameters, and some modulation techniques used in FSO technology are also discussed. [ABSTRACT FROM AUTHOR]

Abstract In this demonstration, we propose and investigate experimentally a bidirectional wavelength-division-multiplexed (WDM) free space optical communication (FSO) system integrated with fiber access network for wireless traffics. Here, there are four 10 Gbit/s on–off keying (OOK) WDM-FSO signals would propagate through a 25 km single-mode fiber (SMF) transmission and a 6 m free space transmission length for the bidirectional downstream and upstream FSO traffics. Moreover, an accurately simulation of detected powers of FSO wavelength under different free space transmission lengths can be estimated based on the proposed WDM-FSO system architecture. Therefore, according to the experimental and simulated results, the bidirectional WDM-FSO transmission can achieve 1000 m free space transmission length based on the obtained power sensitivity of each FSO signal. [ABSTRACT FROM AUTHOR]

In this paper, we numerically investigate the behavior of solitons in a Mach–Zehnder interferometer made of dual-core photonic crystal fibers. The goal was to obtain logic gates with modulated information in ON-OFF keying (OOK). We considered ultra-short solitonic pulses propagating throughout the system in two distinct regimes of pump power and obtained the OR and XOR gates with fundamental solitons. In addition, the A→B and A←B Boolean expressions were obtained with high peak power. As these logical expressions were obtained with the same length of the obtained logic gates, they are important and therefore can be used to save space in the design of complex circuits. [ABSTRACT FROM AUTHOR]

This paper presents a fully combined sensor-antenna transmitter system for sensing relative permittivity of material at microwave frequencies. The transmit (Tx) antenna senses the relative permittivity of specimen and loads the radio frequency (RF) oscillator which translates the relative permittivity to the operational frequency of the carrier signal. At the same time, independent data, which can be the Radio Frequency Identification (RFID) information, are ON–OFF keying modulated over the carrier. At the receiver, a demodulator system extracts the data stream as well as recovers the carrier frequency using a zero-crossing detector. Therefore, the relative permittivity of the sample can be obtained from the extracted frequency shift as a digital number. As all the sensing elements in the proposed structure are passive, the sensor does not increase the power consumption of the system. The sensor-transceiver capability at low powers makes it ideal for sensor nodes in the Internet of Things applications. Since the sensing and demodulation are implemented at the same time, the complexity for detection reduces significantly compared with traditional RF/microwave sensing techniques which need complicated frequency spectrum monitoring equipment. The output of the system is a digital number correlated to the dielectric constant of the specimen and the independent data stream for communication. The proposed sensor node is fabricated at the 2.45-GHz ISM band as an evaluation and the measurement results with some known samples are presented. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive analytical approach is presented for modeling the counting statistics of active quenching and passive quenching single-photon avalanche diode (SPAD) detectors. It is shown that, unlike ideal photon counting receiver for which the detection process is described by a Poisson arrival process, photon counts in practical SPAD receivers do not follow a Poisson distribution and are highly affected by the dead time caused by the quenching circuit. Using the concepts of renewal theory, the exact expressions for the probability distribution and moments (mean and variance) of photocounts in the presence of dead time are derived for both active quenching and passive quenching SPADs. The derived probability distributions are validated through Monte Carlo simulations and it is demonstrated that the moments match with the existing empirical models for the moments of SPAD photocounts. Furthermore, an optical communication system with on–off keying and binary pulse position modulation is considered and the bit error performance of the system for different dead time values and background count levels is evaluated. [ABSTRACT FROM AUTHOR]

This paper presents an ultra-low power super-regenerative receiver suitable for ON–OFF keying modulation and provides analytical insight into its design procedure. The receiver is fabricated in 40-nm CMOS technology and operates in the ISM band of 902–928 MHz. Binary search algorithm through successive approximation register architecture is being exploited to calibrate the internally generated quench signal and the working frequency of the receiver. Employing an on-chip inductor and a single ended to differential architecture for the input amplifier has made the receiver fully integrable, eliminating the need for external components. A power consumption of 320 $\mu \text{W}$ from a 0.65-V supply results in an excellent energy efficiency of 80 pJ/b at 4-Mb/s data rate (DR). The receiver also employs an analog to digital converter that enables soft-decisioning and a convenient sensitivity-DR tradeoff, achieving sensitivity of −86.5, and −101.5 dBm at 1000- and 31.25-kbps DR, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the performance of intensity-modulated with direct detection (IM/DD) free space optical (FSO) system using the on-off keying (OOK) and avalanche photodiode (APD) receiver is observed. The gamma-gamma model is used to describe the effect of atmospheric turbulence since it provides good agreement in the wide range of atmospheric conditions. In addition, the same FSO system with equal gain combining applied at the reception is analyzed. After theoretical derivation of the expression for the bit error rate (BER), the numerical integration with previously specified relative calculation error is performed. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of the FSO link and receiver parameters on the BER performance are discussed. The results illustrate that the optimal APD gain in the minimum BER sense depends considerably on the link distance, atmospheric turbulence strength and receiver temperature. In addition, the value of this optimal gain is slightly different in the case of spatial diversity application compared with single channel reception.

We investigate the error performance of an earth-to-satellite free space optical uplink using transmitter spatial diversity in presence of turbulence and weather conditions, using gamma-gamma distribution and Beer-Lambert law, respectively, for on-off keying (OOK), M-ary pulse position modulation (M-PPM) and M-ary differential PPM (M-DPPM) schemes. Weather conditions such as moderate, light and thin fog cause additional degradation, while dense or thick fog and clouds may lead to link failure. The bit error rate reduces with increase in the number of transmitters for all the schemes. However, beyond a certain number of transmitters, the reduction becomes marginal. Diversity gain remains almost constant for various weather conditions but increases with increase in ground-level turbulence or zenith angle. Further, the number of transmitters required to improve the performance to a desired level is less for M-PPM scheme than M-DPPM and OOK schemes. [ABSTRACT FROM AUTHOR]

Bit-error rate measurements for ON-OFF keying modulation at multigigabit per second rates over a V-band wireless link are presented. Serial data-rates from 2.5 to 20 Gb/s were studied for a 231 -1 bit random sequence. Error-free data transfer over a 0.3-m link was achieved at up to 10 Gb/s. Acceptable bit-error rates, -5 and 10-3, were measured at up to 1.5 m for 10- and 15-Gb/s data-rate, respectively. The performance was achieved using a transmitter that consists of an integrated wavelet generator, whereas the receiver was built from off-the-shelf waveguide components. The results demonstrate that very high data-rates may be achieved using binary modulation and short symbols generated in an efficient V-band transmitter. The system is benchmarked against state-of-the-art transceiver systems with multigigabit per second data-rates.

This paper describes selectivity and sensitivity performance evaluations and improvement methods for an on-off keying super-regenerative (SR) receiver. A slope-controlled quasi-exponential quench waveform, generated by a low-complexity PVT-tolerant quench generator circuit, is proposed to increase data rate and reduce the receiver 3-dB bandwidth, thereby preventing oscillation caused by out-of-band injected signals and improving the receiver selectivity. The SR receiver sensitivity is also enhanced by a noise-canceling front-end topology with single-ended to differential (S2D) signal converter. To exemplify these techniques, we designed an SR receiver with the proposed front-end and quench waveform generator in a 0.18-μm CMOS technology. Theoretical analyses and circuit simulations show 30% and 65% reduction in 3-dB bandwidth of the SR receiver at 25 Mbps data rate by employing the proposed quench signal compared with piecewise-linear and trapezoidal quench waveforms, respectively. Performance of the proposed front-end is evaluated by a fast bit-error-rate estimation procedure, based on circuit noise simulations and statistical analyses, without the need for time-consuming transient-noise simulations. Accuracy of the procedure has been verified by comparing its results with transient-noise simulations. According to the estimated bit-error-rate curves, the noise-canceling topology with S2D converter enhances the SR receiver sensitivity by 9 dB. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this letter, we experimentally analyze the filter narrowing effect for low bandwidth connections in the context of the flexi-grid paradigm for optical aggregation networks. First of all, we characterize the concatenation of up to 12 filters by means of a high resolution optical spectral analyzer. Then, we set up the programmable filters with the obtained characterization, in order to emulate the filter concatenation impairments. The studied filters have nominal bandwidths of 12.5 GHz, 25 GHz, and 50 GHz. The two potential candidates analyzed are intensity modulation/direct detection on-off keying and direct detection orthogonal frequency division multiplexing (OFDM) with uniform and bit loading. Results show a significant signal degradation for filter bandwidths of 12.5 GHz with respect to 25 GHz and 50 GHz, considering a net bit rate of 10 Gb/s. We also conclude that for future entire flexi-paradigm, OFDM is an appropriate candidate. [ABSTRACT FROM PUBLISHER]

This paper describes a frequency-domain on-off keying (F-OOK) modulation method which utilizes power detection of both a carrier and a sideband by modulating the carrier frequency with a pre-selected modulation template. Compared to on-off keying and binary frequency-shift keying modulations, more efficient bandwidth control is achieved for the same data rate with a symmetric FM template. Since the proposed modulation maintains the average center frequency of the carrier regardless of data pattern, the F-OOK signal can be generated by using only the high-pass modulation path of the conventional phase-locked loop-based two-point modulator, thus relaxing design complexity. A prototype transmitter implemented in 65-nm CMOS consumes 1.9 mW from a 0.8-V supply with a data rate of 750 kb/s, achieving an energy efficiency of 2.5 nJ/b. [ABSTRACT FROM AUTHOR]

In this paper, we present a numerical investigation of all-optical logic gates based on a Mach-Zehnder Interferometer (MZI) configuration of micro structured fibers, also known as photonic crystal fibers (PCF) under optical OOK (on-off keying). We determine several relevant quantities to characterize the system performance, such as transmission and extinction ratio as a function of the nonlinearity profile (β) added to one of the Mach-Zehnder Interferometer (MZI) arms. High-order effects such as third-order dispersion, intrapulse Raman scattering and self-steepening were included in the generalized nonlinear Schrödinger equation describing the pulse propagation. For this study, we used an optical pulse with a shape of hyperbolic secant of 100 fs (femtosecond). A pumped laser with three power values was simulated. With critical power Pc = 103.5 kW (P = Pc), below the critical power P = 90 kW (P < Pc) and above the critical power P = 110 kW (P > Pc). We added a nonlinearity profile in one of the Mach-Zehnder Interferometer (MZI) arms. Nonlinearity profiles were expressed in terms of the parameter β. We studied three different profiles: constant, increasing and decreasing. Our results show that the proposed device can be used to obtain all-optical OR and XOR logic gates as well as logic functions A and A . B ¯ . The OR logic gate was the one which achieved the greatest FOMELG ( Figure of Merit of Logic Gates ) when using increasing profile with critical power (P 0 = 103.5 kW) for β = 1.05 and FOMELG = 15.68 dB. The XOR logic gate presented the greatest FOMELG = 7.75 dB when using the decreasing profile with power below the critical (P 0 = 90 kW) for β = 1.44. These results provide support for applications in all-optical networks. [ABSTRACT FROM AUTHOR]

In this letter, we present a novel hybrid intensity modulation and direct detection communication system, which integrates asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and on–off keying (OOK) modulation schemes. First, the negative ACO-OFDM is proposed based on the conventional ACO-OFDM system to accommodate the on case with direct current in the OOK modulation, while the ACO-OFDM can match the off case in the OOK modulation. Therefore, the novel hybrid system combines the ACO-OFDM and OOK modulation schemes, while the signals can be recovered at the receiver to support the different qualities of service with high spectral efficiency and can be adapted to various receivers with different complexities. Simulation results are reported for the visible light channel and show that both the ACO-OFDM and OOK signals can be well recovered. [ABSTRACT FROM PUBLISHER]