Optical Communication Technology Research Articles

Broadband Port-Selective Silicon Beam Scanning Device for Free-Space Optical Communication

Indoor free space optical (FSO) communication technology that provides high-speed connectivity to edge users is expected to be introduced in the near future mobile communication system, where the silicon photonics solid-state beam scanning device is a promising tool because of its low cost, long-term reliability, and other beneficial properties. However, the current two-dimensional beam scanning devices using grating coupler arrays have difficulty in increasing the transmission capacity because of bandwidth regulation. To solve the problem, we have introduced a broadband surface optical coupler, “elephant coupler,” which has great potential for combining wavelength and spatial division multiplexing technologies into the beam scanning device, as an alternative to grating couplers. The prototype port-selective silicon beam scanning device fabricated using a 300 mm CMOS pilot line achieved broadband optical beam emission with a 1 dB-loss bandwidth of 40 nm and demonstrated beam scanning using an imaging lens. The device has also exhibited free-space signal transmission of non-return-to-zero on-off-keying signals at 10 Gbps over a wide wavelength range of 60 nm. In this paper, we present an overview of the developed beam scanning device. Furthermore, the theoretical design guidelines for indoor mobile FSO communication are discussed.

Optimization Method for Center Frequency Accuracy of High-Channel-Count Arrayed Waveguide Grating in Dense Wavelength Division Multiplexing Systems

The arrayed waveguide grating (AWG) is an essential component in dense wavelength division multiplexing (DWDM) systems. With advancements in optical communication technology, the number of AWG output channels has rapidly increased. However, achieving high center frequency accuracy (CFA) for these channels has become a significant challenge. This paper presents a design and optimization approach for a high-channel-count AWG based on the silica platform and the finite difference beam propagation method (FD-BPM). The causes of center frequency deviation are analyzed, and an optimization method is proposed to adjust the constraint relationship and geometric position of the output waveguides in order to improve CFA. Simulation results demonstrate the excellent optical performance of the designed AWG, achieving a CFA of up to 0.04 times the output channel frequency spacing. The insertion loss, insertion loss uniformity, and adjacent output channel crosstalk are simulated as 1.51 dB, 0.38 dB, and 23.81 dB, respectively. The optimized CFA could compensate for center frequency deviations caused by manufacturing errors and temperature fluctuations. The findings of this research hold potential for extending the optimization to other material platforms and contributing to the development of DWDM systems in the field of optical communication.

Controlled Cavity Length and Wide-Spectrum Lasing in FAMACsPb(BrI)3 Ternary Perovskite Vertical-Cavity Surface-Emitting Lasers with an All-Dielectric Dielectric Bragg Reflector

In this study, we utilized a dielectric Bragg reflector (DBR) as a mirror and positioned a wide-spectrum FAMACsPb(BrI)3 halide perovskite film between two DBRs to construct a vertical-cavity surface-emitting laser (VCSEL) structure. The top and bottom DBRs were connected using optical adhesive, allowing us to control the cavity length by applying external force. Through this approach, we achieved operation at the desired wavelength. Due to the exceptional optical gain provided by FAMACsPb(BrI)3, we successfully observed multimode and lasing phenomena at room temperature under continuous-wave (CW) laser excitation. The outcomes of this study provide valuable insights for the application of novel VCSEL structures and highlight the potential of using FAMACsPb(BrI)3 halide perovskites in optical gain. This work holds significant implications for the fields of optical communication and laser technology.

Research on Adaptive Reverse Design Method of Integrated Optical Fiber Communication System

The vigorous development of network technology promotes the progress of communication transmission technology, and the progress of communication transmission technology also drives the development of network technology. Optical fiber communication technology is widely used in communication industry because of its strong anti-interference ability, fast transmission speed and large amount of information. With the explosive growth of network data traffic in recent years, the transmission capacity of optical fiber communication has been continuously improved, coherent optical communication technology has developed rapidly, the trend of intelligence, grouping and broadband has become more and more obvious, and new photoelectric devices have been continuously developed and used. Optical fiber communication technology is undergoing tremendous changes and will become more important. In this paper, the application of optical fiber communication transmission technology is discussed in detail, and an adaptive reverse design method of integrated optical fiber communication system is proposed in order to promote the rapid development of optical fiber communication transmission technology.

Gain Maximization of BDFA between the Wavelength of 1700nm to 1800nm

Fiber optic communication technology is becoming increasingly important in various fields, and high-speed, large-capacity fiber optic transmission systems are urgently needed. The design of fiber amplifiers is influenced by both fiber length and doping concentration. Although the Erbium-doped fiber amplifier (EDFA) is one of the most widely used components in fiber optic communication systems, its working area cannot meet the growing demand for network traffic.This paper presents a new fiber amplifier operating in the spectral region of 1700-1800 nm, pumped by commercially available laser diodes, highlighting the potential benefits of developing optical amplifiers for new spectral regions.This paper constructs a model to optimize gain at the central wavelength by finding relevant parameters, fitting a binary function of gain as a function of doping concentration and fiber length using Matlab, and optimizing the maximum gain using a simulated annealing algorithm. The proposed fiber amplifier has potential applications in telecommunications, sensing, and spectroscopy. The design of the amplifier has been optimized to achieve high gain and low noise figures, which are crucial for practical applications. Furthermore, the amplifier can be easily integrated into existing fiber optic networks, making it a promising candidate for future optical communication systems.

The hybrid pulse amplitude width modulation scheme: high efficiency technique for dimmable VLC systems

Abstract Visible-light communications (VLC) is an environmentally friendly optical wireless communication (OWC) technology that operates in the 400–800 THz frequency band. It is currently a critical technology for 5G and 6G wireless indoor applications due to its high data rates, low latency, and superior reliability. Intensity modulated direct detection (IM/DD) is widely used in VLC systems. A channel modulation scheme is designed using L-level pulse modulation techniques such as on–off keying (OOK), amplitude modulation (PAM), position modulation (PPM), and the width modulation (PWM). We introduce a novel hybrid modulation scheme n-M-PAWM based on both PAM and PWM schemes to improve throughput and significantly increase power and spectrum efficiency in VLC communication systems. The performance of our proposed hybrid n-M-PAWM scheme is studied in several aspects, including the number of transmitted bits per symbol, average BER, information rate ratio (IRR), PAPR, bandwidth, and power requirement. In an extremely noisy VLC system, the proposed 2-M-PAWM modulation outperforms both PPWM and PAPM modulation schemes due to its better BER performances. Additionally, we examine the performance of the VLC system in terms of spectral efficiency (SE) using our proposed PAWM-based dimming control system by varying the number of pulses transmitted during one symbol period. We demonstrate through simulation results that our PAWM-based dimming control system performs significantly better compared to the other pulse modulation schemes. All results of this research show that our proposed hybrid PAWM modulation scheme has high potential for VLC technology in indoor and noisy environments.

A 50 Gb/s PAM-4 EAM driver in 28-nm CMOS technology

With the rapid development of Ethernet, the research of new high-speed optical communication technology is getting more and more attention. The external modulation technique is unaffected by frequency chirp makes the fiber optic system more stable. Meanwhile, the small driving voltage and efficient area of the electro-absorption optical modulator make the electro-absorption modulator(EAM) driver more widely used. The signal emission by the optical module is critically dependent on the performance of the EAM driver. This article presents a 50 Gb/s four pulse amplitude modulation(PAM-4) EAM driver in 28-nm CMOS. The proposed EAM driver consists of a continuous-time linear equalizer (CTLE), a variable gain amplifier (VGA), a preamp, and an output stage circuit. Linearity is enhanced by using inverter-based structures in the proposed CTLE, VGA, and preamp. The source-degenerated resistors are adopted by CTLE and VGA to provide equalization and improve linearity. Additionally, shunt peaking inductors are used to extend the bandwidth. To provide a large output swing, the output stage adopts the cascode structure. Measured results demonstrate that: the EAM driver has 23.12 GHz bandwidth and 2.14 V output voltage swing at 50-Gb/s. The EAM driver consumes 226 mW power while having an active area of 0.26 mm2.

Spectral properties and theoretical analysis of Dy3+:KGd(WO4)2 crystals in the visible wavelength band

Yellow laser has been widely applied in various fields such as biomedicine, optical communication technology and chip processing. This study focuses on the preparation and characterization of a 3 at.% Dy3+:KGd(WO4)2 crystal. The crystal was grown by the top-seeded solution growth method. The absorption spectrum, excitation spectrum, emission spectrum, and fluorescence decay curve were measured at room temperature, and the fluorescence properties of the crystal in the yellow region were explored. Analysis of the absorption spectrum revealed an absorption cross-section σabs of 4.81 × 10−21 cm2 at 453 nm (E//Y), corresponding to the 6H15/2 → 4I15/2 transition. Utilizing the Judd-Ofelt theory, the J-O intensity parameters Ωt, radiative transition probability, fluorescence branching ratio, and radiative lifetime were calculated. The F-L theory was used to calculate the emission cross-section σem at 575 nm (E//Y), which was found to be 2.43 × 10−20 cm2, along with a fluorescence lifetime τf of 148.5 μs and a fluorescence quantum efficiency of 80.35% for 4F9/2. These findings suggest that Dy3+:KGd(WO4)2 crystal shows significant promise as a yellow laser material, with the potential to contribute to both commercial and scientific fields.

Experimental Studies and Analysis of 1550 nm Laser as Optical Wireless Communication Link in Simulated Rainy, Foggy, and Heating Conditions According to Indian Atmosphere

Interests are vastly growing on optical wireless communication (OWC) technology in recent times. This technology is mostly used where fibber-optic or wired communication technology cannot be used. However, the main constraints of this OWC technology are the attenuation of the laser power due to different atmospheric effects. This paper investigates the effects on the 1550 nm laser link in the various simulated atmospheric conditions, such as rain, fog, and heat in terms of signal to noise ratio (SNR), bit error rate (BER), optical power attenuation with the help of some pre-established models etc. For analysing the previously mentioned parameters in different simulated atmospheric conditions, a 10 MHz, NRZ-OOK, OWC communication channel has been established using fibber coupled acousto-optic modulator (FCAOM), and all the parameters are measured for 18 m link range. The peculiarity of this article is that the calculations and results have been made with keeping in mind the Indian atmospheric conditions. Indian weather report data has been used to do so.

Probing Optical Multi-Level Memory Effects in Single Core-Shell Quantum Dots and Application Through 2D-0D Hybrid Inverters.

Challenges in the development of a multi-level memory (MM)device for multinary arithmetic computers have posed an obstacle to low-power, ultra-high-speed operation. For the effective transfer of a huge amount of data between arithmetic and storage devices, optical communication technology represents a compelling solution. Here, by replicating a floating gate architecture with CdSe/ZnS type-I core/shell quantum dots (QDs), a 2D-0D hybrid optical multi-level memory (OMM) device operated is demonstrated by laser pulses. In the device, laser pulses create linear optically trapped currents with MM characteristics, while conversely, voltage pulses reset all the trapped currents at once. Assuming electron transfer via the energy band alignment between MoS2 and CdSe, the study also establishes the mechanism of the OMM effect. Analysis of the designed device led to a new hypothesis that charge transfer is difficult for laterally adjacent QDs facing a double ZnS shell, which is tested by separately stimulating different positions on the 2D-0D hybrid structure with finely focused laser pulses. Results indicate that each laser pulse induced independent MM characteristics in the 2D-0D hybrid architecture. Based on this phenomenon,wepropose a MM inverter to produce MM effects, such as programming and erasing, solely through the use of laser pulses. Finally, the feasibility of a fully optically-controlled intelligent system based on the proposed OMM inverters is evaluated through a CIFAR-10 pattern recognition task using a convolutional neural network.

Analyzing the physical behavior of optical fiber pulses using solitary wave solutions of the perturbed Chen–Lee–Liu equation

This research paper investigates the behavior of optical fiber pulses by studying the solitary wave solutions of the perturbed Chen–Lee–Liu (CLL) equation. The perturbed CLL equation is derived from the perturbed Schrödinger equation. Two analytical approaches for obtaining the innovative soliton-wave solutions are presented in this paper, and their reliability is examined by using a well-established numerical method. The accuracy of pulse wave analysis in an optical cable is demonstrated through a series of graphical representations. Our study introduces scientific novelty, as evidenced by the comparative analysis of our data with those of previous research papers. This research contributes to enhancing the understanding of the kinetics and physical behavior of pulses in optical fibers, which holds implications for the advancement of optical communication technologies.

High-Speed Underwater Optical Wireless Communication with Advanced Signal Processing Methods Survey

Underwater wireless communication (UWC) technology has attracted widespread attention in the past few years. Compared with conventional acoustic underwater wireless communication technology, underwater optical wireless communication (UOWC) technology has promising potential to provide high data rate wireless connections due to the large license-free bandwidth. Building a high-performance and reliable UOWC system has become the target of researchers and various advanced and innovative technologies have been proposed and investigated. Among them, better hardware such as transmitters and receivers, as well as more advanced modulation and signal processing techniques, are key factors in improving UOWC system performance. In this paper, we review the recent development in UOWC systems. In particular, we provide a brief introduction to different types of UOWC systems based on channel configuration, and we focus on various recent studies on advanced signal processing methods in UOWC systems, including both traditional non-machine learning (NML) equalizers and machine learning (ML) schemes based on neural networks. In addition, we also discuss the key challenges in UOWC systems for future applications.

Weathers effect on the free space optics communication system

Unlicensed spectrum is used in free space optics (FSO) communication, significantly increasing available bandwidth. Regardless of the weather, the most immediate concern is the link's performance and availability. Changes in the weather might impact the reliability of the link substantially. As a result, iterative optimization is being used to reduce the impact of weather and geography on FSO communication. In addition to enhancing visibility, this enhancement also reduces the bit error rate (BER). The system's wireless optical communication technology supports a data rate of up to 10 Gbps. The proposed wireless optical communication performance is compared to existing technologies regarding the visible distance, quality factor, BER, and eye diagram in various meteorological circumstances. Simulations show that the proposed work is more efficient.

All-Optical Signal Processing in Ultrafast Optical Communication

Optical communication technology plays a crucial role in today's information age, as a result of the continuous advancement of social informatization. An array of nascent technologies, encompassing edge computing, the Internet of Things, big data, and artificial intelligence, have grown rapidly, leading to an increased demand for information transmission, which in turn has resulted in higher requirements for the development of optical communication technology. The emergence of ultrafast optical communication, which uses all-optical signal processing technology, has made data transmission faster and more reliable. This article introduces three basic methods for implementing all-optical signal processing (optical modulation, regeneration, and interconnection) based on all-optical and electronic signal processing. It examines the issues and difficulties that arise within particular application contexts and explores the progression of several correlated technologies in the times ahead. The field of all-optical signal processing is experiencing rapid growth and has the potential to bring revolutionary changes to various industries. Anticipated outcomes entail the attainment of ultra-long distance and ultra-high-capacity transmission, as facilitated by the ongoing advancements in hardware and all-optical signal processing technology. Meanwhile, the relentless pursuit of high-performance goals drives the continuous progress of ultrafast optical communication.

Performance investigation of multi-aperture digital combining algorithm for satellite-to-ground coherent optical communication

An important component of the future communication network will include satellite-to-ground communication technology. In the meantime, the community of communication network also has a huge capacity as one of its purposes. In this situation, the free-space optical (FSO) communication technology is a potential option for satellite-to-ground communications. A major drawback of FSO communication systems, nevertheless, is atmospheric turbulence. Multi-aperture receiver with digital combining architecture is an effective approach to overcoming the effect of atmospheric turbulence on the performance of free-space optical (FSO) communication. In this paper, a blind digital combining algorithm for coherent FSO communication is proposed. To verify the effectiveness of the proposed combining algorithm, a 10-Gbps data rate single polarization 16-ary quadrature amplitude modulation (SP-16QAM) offline four-aperture simulated turbulence experiment is performed, and the performance of multi-aperture spatial diversity and signal processing is emulated through the experimental data. The results confirm that the proposed blind digital combining algorithm has an excellent performance in average bit error rate (BER). Compared with the single-aperture system, the receiver sensitivity of the four-aperture is increased by 1.2, 4.6, and 6.8 dB for the cases of weak, moderate, and strong turbulence at the SD-FEC threshold, respectively.

Tbit/s line-rate satellite feeder links enabled by coherent modulation and full-adaptive optics

Free-space optical (FSO) communication technologies constitute a solution to cope with the bandwidth demand of future satellite-ground networks. They may overcome the RF bottleneck and attain data rates in the order of Tbit/s with only a handful of ground stations. Here, we demonstrate single-carrier Tbit/s line-rate transmission over a free-space channel of 53.42 km between the Jungfraujoch mountain top (3700 m) in the Swiss Alps and the Zimmerwald Observatory (895 m) near the city of Bern, achieving net-rates of up to 0.94 Tbit/s. With this scenario a satellite-ground feeder link is mimicked under turbulent conditions. Despite adverse conditions high throughput was achieved by employing a full adaptive optics system to correct the distorted wavefront of the channel and by using polarization-multiplexed high-order complex modulation formats. It was found that adaptive optics does not distort the reception of coherent modulation formats. Also, we introduce constellation modulation – a new four-dimensional BPSK (4D-BPSK) modulation format as a technique to transmit high data rates under lowest SNR. This way we show 53 km FSO transmission of 13.3 Gbit/s and 210 Gbit/s with as little as 4.3 and 7.8 photons per bit, respectively, at a bit-error ratio of 1 ∙ 10−3. The experiments show that advanced coherent modulation coding in combination with full adaptive optical filtering are proper means to make next-generation Tbit/s satellite communications practical.

Latest Developments in the Field of Optical Communications for Small Satellites and Beyond

In this paper, we introduce our vision for the future non-terrestrial networks beyond 5G and discuss the possible implementation scenarios for free-space optical communication technology in it, especially regarding the satellite communications segment. We show and discuss some of the latest system developments globally in the field of optical communications for small satellites. Together with the latest projects in the National Institute of Information and Communications Technology (NICT) of Japan for payloads for small moving platforms, a specific trend in the field is clearly defined. We further show our newly developed ground station for the experiments with our High-speed Communication with Advanced Laser Instrument (HICALI) payload and discuss the main challenges in a satellite to ground optical link and our specific solution providing preliminary test results of the performance.

(Invited) Brief analysis of the impact of Hasegawa-Nyu’s work “Eigenvalue communication” on modern optical communication technologies

Optical solitons are known to preserve the eigenvalues in the inverse scattering transform (IST) thus the eigenvalues can be used as robust information carriers. If several eigenvalues and their combinations are used in a soliton as information carrier, the transmission data rate can be increased drastically. Based on the concept, Hasegawa and Nyu proposed eigenvalue communication in 1993. In this paper, the impact of their pioneering work “Eigenvalue communication” on modern optical communication technologies are introduced and analyzed briefly.

The Road to High Data Rates in Space: Terahertz Versus Optical Wireless Communication

With the ultimate vision of ubiquitous egalitarian worldwide coverage, private companies are launching satellite constellations at unprecedented rates. The large projected traffic in orbital cross-link communication will demand more spectrum to suit more users and to satisfy higher data rates. In this paper, terahertz and optical wireless communication technologies are explored as the two projected high-data-rate cross-link communication technologies and are compared in terms of device technology capabilities and wireless propagation properties. A performance analysis including a link budget directly compares the two technologies for space communication in low Earth orbit constellations. More importantly, a roadmap is provided paving the way to push both ultra-broadband wireless technologies forward.

Comparison of the frontiers optical quantum communication technology with traditional classical communication technology

Due to the advancement of technology, laser communication, fiber optic communication and optical quantum communication have been developed, not only in the field of life, but also in the field of aviation, military and information security. This paper, mainly compares the difference between optical quantum communication and other communication technologies in terms of security and effectiveness, presenting the current state of technology and applications and providing an outlook on future directions. Through the comparison, this paper argues that the application of technology in optical quantum communication can promote the rapid development of quantum communication technology and thus enhance the comprehensive strength of global communication technology.