Journal of Lightwave Technology

The recently developed digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as M-ary phase-shift keying and quadrature-amplitude modulation. Moreover, in the digital domain, we can equalize all linear transmission impairments such as group-velocity dispersion and polarization-mode dispersion of transmission fibers, because coherent detection pres... View full abstract»

This paper attempts to clarify the difference between visible light communication (VLC) and light-fidelity (LiFi). In particular, it will show how LiFi takes VLC further by using light emitting diodes (LEDs) to realise fully networked wireless systems. Synergies are harnessed as luminaries become LiFi attocells resulting in enhanced wireless capacity providing the necessary connectivity to realise... View full abstract»

This paper aims to address the perception that visible light communication (VLC) systems cannot work under the presence of sunlight. A complete framework is presented to evaluate the performance of VLC systems in the presence of solar irradiance at any given location and time. The effect of solar irradiance is investigated in terms of degradations in signal to noise ratio, data rate, and bit error... View full abstract»

Orthogonal frequency division multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems because it is an effective solution to intersymbol interference caused by a dispersive channel. Very recently a number of researchers have shown that OFDM is also a promising technology for optical communications. This paper gives... View full abstract»

Internet of Things (IoT) requires cloud infrastructures for data analysis (e.g., temperature monitoring, energy consumption measurement, etc.). Traditionally, cloud services have been implemented in large datacenters in the core network. Core cloud offers high-computational capacity with moderate response time, meeting the requirements of centralized services with low-delay demands. However, colle... View full abstract»

Microwave measurement refers to the acquisition of parameters of a microwave signal or the identification of properties of an object via microwave-based approaches. Thanks to the broad bandwidth and high speed provided by modern photonics, microwave measurement in the optical domain can provide better performance in terms of bandwidth and speed which may not be achievable using traditional, even s... View full abstract»

Modulation nonlinearity can severely distort multilevel modulation, and signal processing to mitigate the distortion is highly desirable. In this paper, we demonstrated a machine learning method for adaptive detection of 4-level pulse amplitude modulation (PAM-4) signals modulated by silicon micro-ring modulator (Si-MRM). The very limited linear modulation range of Si-MRM leads to serious modulati... View full abstract»

We describe a method to estimate the capacity limit of fiber-optic communication systems (or ¿fiber channels¿) based on information theory. This paper is divided into two parts. Part 1 reviews fundamental concepts of digital communications and information theory. We treat digitization and modulation followed by information theory for channels both without and with memory. We provide explicit relat... View full abstract»

In this paper, three forms of orthogonal frequency division multiplexing (OFDM) designed for intensity modulated/direct detection (IM/DD) optical systems are compared. These are asymmetrically clipped optical OFDM (ACO-OFDM), DC biased optical OFDM (DCO-OFDM) and asymmetrically clipped DC biased optical OFDM (ADO-OFDM). ADO-OFDM is a new technique that combines aspects of ACO-OFDM and DCO-OFDM by ... View full abstract»

Surface plasmon resonance (SPR) optical fiber sensors can be used as a cost-effective and relatively simple-to-implement alternative to well established bulky prism configurations for in situ high sensitivity biochemical and electrochemical measurements. The miniaturized size and remote operation ability offer them a multitude of opportunities for single-point sensing in hard-to-reach spaces, even... View full abstract»

We investigate phase-modulated analog photonic link performance using interferometric detection with a Mach- Zehnder interferometer (MZI) under different bias conditions and a high-power high-linearity modified unitraveling carrier (MUTC) photodiode (PD). Expressions for radio frequency (RF) small signal gain and the optimal MZI bias point for RF gain are derived, and noise figure (NF) and third-o... View full abstract»

We present the demonstration of an integrated frequency modulated continuous wave LiDAR on a silicon platform. The waveform calibration, the scanning system, and the balanced detectors are implemented on a chip. Detection and ranging of a moving hard target at upto 60 m with less than 5 mW of output power is demonstrated in this paper. View full abstract»

In this paper, a simple scheme for linear frequency-modulated (LFM) waveform generation based on a frequency-sweeping optoelectronic oscillator is proposed and demonstrated. The OEO is built up with an optically injected semiconductor laser and the oscillation frequency can be tuned by adjusting the optical injection strength. By applying an injection strength controller in the OEO for rapid frequ... View full abstract»

After dominating the electronics industry for decades, silicon is on the verge of becoming the material of choice for the photonics industry: the traditional stronghold of III-V semiconductors. Stimulated by a series of recent breakthroughs and propelled by increasing investments by governments and the private sector, silicon photonics is now the most active discipline within the field of integrat... View full abstract»

In this paper, we implement an optical fiber communication system as an end-to-end deep neural network, including the complete chain of transmitter, channel model, and receiver. This approach enables the optimization of the transceiver in a single end-to-end process. We illustrate the benefits of this method by applying it to intensity modulation/direct detection (IM/DD) systems and show that we c... View full abstract»

We achieved the lowest-ever transmission losses of 0.1419 dB/km at 1560 nm wavelength and 0.1424 dB/km at 1550 nm in a Ge-free silica-core optical fiber. It was an improvement by 4 mdB/km from the previous record realized in 2015. The Ge-free silica core included fluorine co-doping, which helps to reduce disorder in the microscopic glass network structure that causes Rayleigh scattering loss witho... View full abstract»

The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described. View full abstract»

Broadband and low loss capability of photonics has led to an ever-increasing interest in its use for the generation, processing, control and distribution of microwave and millimeter-wave signals for applications such as broadband wireless access networks, sensor networks, radar, satellite communitarians, instrumentation and warfare systems. In this tutorial, techniques developed in the last few ye... View full abstract»

Next generation 5G mobile system will support the vision of connecting all devices that benefit from a connection, and support a wide range of services. Consequently, 5G transport networks need to provide the required capacity, latency, and flexibility in order to integrate the different technology domains of radio, transport, and cloud. This paper outlines the main challenges, which the 5G transp... View full abstract»

Multicore fibers (MCFs) are expected as a good candidate for overcoming the capacity limit of a current optical communication system. This paper describes the recent progress on the MCFs for space-division multiplexing to be utilized in future large capacity long-distance transmission systems. Tradeoff issue between low crosstalk and high core density in MCFs is presented and prospect of large-spa... View full abstract»

Machine learning techniques relevant for nonlinearity mitigation, carrier recovery, and nanoscale device characterization are reviewed and employed. Markov Chain Monte Carlo in combination with Bayesian filtering is employed within the nonlinear state-space framework and demonstrated for parameter estimation. It is shown that the time-varying effects of cross-phase modulation (XPM) induced polariz... View full abstract»

The next-generation passive optical network stage 2 (NG-PON2) effort was initiated by the full service access network (FSAN) in 2011 to investigate on upcoming technologies enabling a bandwidth increase beyond 10 Gb/s in the optical access network. The FSAN meeting in April 2012 selected the time- and wavelength-division multiplexed passive optical network (TWDM-PON) as a primary solution to NG-PO... View full abstract»

Optical signal processing brings together various fields of optics and signal processing - namely, nonlinear devices and processes, analog and digital signals, and advanced data modulation formats - to achieve high-speed signal processing functions that can potentially operate at the line rate of fiber optic communications. Information can be encoded in amplitude, phase, wavelength, polarization a... View full abstract»

We study the techno-economics of submarine systems constrained by a fixed electrical power supply. We show significant cost savings for high-capacity submarine systems using massive space-division multiplexing (SDM), even without assuming any savings from SDM-specific subsystem integration. Systems with about 100 parallel optical paths, e.g., ~50 fiber pairs are shown to provide minimum cost/bit, ... View full abstract»

In this paper, we describe the spectral characteristics that can be achieved in fiber reflection (Bragg) and transmission gratings. Both principles for understanding and tools for designing fiber gratings are emphasized. Examples are given to illustrate the wide variety of optical properties that are possible in fiber gratings. The types of gratings considered include uniform, apodized, chirped, d... View full abstract»

Visible light communications is an alternative method of indoor wireless communications that requires sensitive receivers. Ideally, single photon avalanche detectors (SPADs) could be used to create more sensitive receivers. However, the dead time, finite output pulse width, and photon detection efficiency of existing SPAD arrays limit their sensitivity and bandwidth. In this paper, an accurate equ... View full abstract»

In this paper, we introduce an end-to-end and real-time seamless fiber-wireless (Fi-Wi) bridge system, for gigabit Ethernet standard data connectivity and 8K standard video streaming. The proposed end-to-end Fi-Wi bridge system consists of seamless integration of 2 × 20-km intermediate frequency-over-fiber (IFoF) and 96-GHz millimeter-wave (mmWave) wireless links. Using our system, zero packet los... View full abstract»

We report the first demonstration of gain-switched optical pulses generated by continuous-wave 1.3 μm InAs/GaAs quantum dot (QD) broad-area lasers directly grown on silicon. The shortest observed pulses have typical durations between 175 and 200 ps with peak output powers of up to 66 mW. By varying the drive current pulsewidth and amplitude systematically, we find that the peak optical power is ma... View full abstract»

In this paper, interference mitigation techniques based on angle diversity receivers (ADRs) are studied for optical attocell networks. Consisting of multiple photodiodes (PDs), an ADR requires appropriate signal combining schemes in order to mitigate intercell interference (ICI) in optical attocell networks. Four signal combining schemes, namely select best combining, equal gain combining, maximum... View full abstract»

A novel automatic bias control (ABC) method which could lock an optical IQ modulator at arbitrary bias points is proposed and experimentally demonstrated for the first time. In the proposed method, the sequences and parameters of the used dither signals and the switch of the applied bias voltages are specially designed to minimize the influence of the power coupling between three MZMs in optical I... View full abstract»

Keeping up with bandwidth requirements in next generation short- and long-reach optical communication systems will require migrating from simple modulation formats such as on-off keying to more advanced formats such as quaternary phase-shift keying (QPSK). In this paper, we report the first demonstration of QPSK signal generation in the O-band using a silicon dual-drive Mach-Zehnder modulator (DD-... View full abstract»

In general, visible light communication (VLC) systems, which utilise white light-emitting diodes (LEDs), only offer a bandwidth limited to the lower MHz region. Therefore, providing VLC-based high data rate communications systems using VLC becomes a challenging task. To address this challenge, we propose a solution based on multiplexing in both the frequency and space domains. We experimentally de... View full abstract»

We report simultaneous transmission of six spatial and polarization modes, each carrying 40 Gb/s quadrature-phase-shift-keyed channels over 96 km of a low-differential group delay few-mode fiber. The channels are successfully recovered by offline DSP based on coherent detection and multiple-input multiple-output processing. A penalty of <;1.2 dB is achieved by using 6 × 6 feed-forward equalizer... View full abstract»

A Gaussian noise (GN) model, precisely accounting for an arbitrary frequency dependent signal power profile along the link, is presented. This allows accurate evaluation of the impact of inter-channel stimulated Raman scattering (ISRS) on the optical Kerr nonlinearity. Additionally, the frequency dependent fiber attenuation can be taken into account and transmission systems that use hybrid amplifi... View full abstract»

The set-partitioning quadrature amplitude modulation (SP-QAM) formats are highly preferred for the next generation fiber optical transmission system, due to the Euclidean distance increment of constellation and its power efficiency. However, the existing carrier phase recovery (CPR) scheme of SP-QAM is independently implemented between two polarization signals, and the laser linewidth tolerance of... View full abstract»

In this paper, we present a miniature fiber-optic Fabry-Pérot interferometric pressure sensor based on an in situ printed fiber-top air cavity. With an in-house optical 3D μ-printing setup, a suspended SU-8 diaphragm with light scatter is directly printed on the end face of standard optical fiber to form a sealed Fabry-Pérot cavity. The fabricated Fabry-Pérot microinterferometer shows a linear res... View full abstract»

For a future 5G Ethernet-based fronthaul architecture, 100G trunk lines of a transmission distance up to 10 km over a standard single-mode fiber (SSMF) in combination with cheap gray optics to daisy chain cell site network interfaces are a promising cost- and power-efficient solution. For such a scenario, different intensity modulation and direct detect formats at a data rate of 112 Gb/s, namely N... View full abstract»

We investigate the performance and design of free-space optical (FSO) communication links over slow fading channels from an information theory perspective. A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence and pointing errors is derived. Unlike earlier work, our model considers the effect of beam width, detector size, an... View full abstract»

Microwave photonic filters are photonic subsystems designed with the aim of carrying equivalent tasks to those of an ordinary microwave filter within a radio frequency (RF) system or link, bringing supplementary advantages inherent to photonics such as low loss, high bandwidth, immunity to electromagnetic interference (EMI), tunability, and reconfigurability. There is an increasing interest in thi... View full abstract»

This paper presents an overview of integrated optics routing and coupling devices based on multimode interference. The underlying self-imaging principle in multimode waveguides is described using a guided mode propagation analysis. Special issues concerning the design and operation of multimode interference devices are discussed, followed by a survey of reported applications. It is shown that mult... View full abstract»

Driven primarily by cloud service and data-center applications, short-reach optical communication has become a key market segment and growing research area in recent years. Short-reach systems are characterized by direct detection-based receiver configurations and other low-cost and small form factor components that induce transmission impairments unforeseen in their coherent counterparts. Innovat... View full abstract»

Fiber-induced intra- and interchannel nonlinearities are experimentally tackled using blind nonlinear equalization (NLE) by unsupervised machine-learning-based clustering (MLC) in ~46-Gb/s single-channel and ~20-Gb/s (middle-channel) multichannel coherent multicarrier signals (orthogonal frequency-division multiplexing (OFDM) based). To that end, we introduce, for the first time, hierarchical and ... View full abstract»

In this paper, a pulse-overlapping super-Nyquist (Pol-SN) wavelength-division multiplexing (WDM) scheme is proposed to improve spectral efficiency of coherent optical transmission. In this scheme, two tributaries of polarization-division multiplexing quadrature phase-shift keying (PDM-QPSK) signals at the transmitter, carried by the same wavelength, are grouped together to allow for pulse overlapp... View full abstract»

Light-fidelity (LiFi) relies on visible light communication to provide multiuser access in a small cell. For higher throughput, this paper studies the resource allocation problem for an orthogonal frequency-division multiplexing access scheme for LiFi downlink transmissions and presents a joint design of the bias level, power and subcarrier allocation. Decomposing the original optimization into su... View full abstract»

Microring resonators side coupled to signal waveguides provide compact, narrow band, and large free spectral range optical channel dropping filters. Higher order filters with improved passband characteristics and larger out-of-band signal rejection are realized through the coupling of multiple rings. The analysis of these devices is approached by the novel method of coupling of modes in time. The ... View full abstract»

In future photonic-based THz backhaul links, integrating the optical local oscillator (LO) in a remote antenna unit can be beneficial in terms of optical bandwidth efficiency and higher compatibility with passive optical networks. In such a scenario, two approaches can be used to reduce the high phase noise associated with free-running lasers: 1) baseband (BB) signals & carrier recovery, and 2... View full abstract»

The high index contrast silicon-on-insulator platform is the dominant CMOS compatible platform for photonic integration. The successful use of silicon photonic chips in optical communication applications has now paved the way for new areas where photonic chips can be applied. It is already emerging as a competing technology for sensing and spectroscopic applications. This increasing range of appli... View full abstract»

We developed a distributed vibration sensor by using heterodyne detection and signal processing of moving averaging and moving differential for the phase optical time domain reflectometry system. The broadband acoustic frequency components generated by pencil-break vibration have been measured and identified in location by our distributed vibration sensor for the first time. Pencil break measureme... View full abstract»

This tutorial describes the transmission, group delay time and quadratic dispersion properties of the four basic building blocs of optical filters built using ring resonators. These building blocs are single-ring resonators in either two-port (all-pass) or four-port (add/drop filter) configuration. The effect of waveguide and coupler loss is included throughout. Explicit expressions to compute the... View full abstract»

This paper presents a linear current driver for simultaneous illuminations and high-speed visible light communications. Our proposed driver integrates a high-efficient converter, a preequalizer, and a high-bandwidth transconductor with an emitter equalizing stage together. In order to enhance the bandwidth and stability, we present an accurate model of our proposed driver to analyze the major impa... View full abstract»