This PDF file contains the front matter associated with SPIE Proceedings Volume 11713, including the Title Page, Copyright Information, and Table of Contents.

While network traffic keeps increasing at exponential rates, fiber-optic communication systems are rapidly approaching fundamental as well as practical limits in capacity and power consumption. This reality holds true from sophisticated digital coherent trans-oceanic transmission systems all the way to highly integrated co-packaged optics for short-reach intra-datacenter links. We will explore scalability limitations across fiber-optic communication applications and show how massive spatial parallelism is the only way to scale communication system capacities while providing the necessary energy and cost reductions to keep the Internet scale in a viable manner.

Introduction to SPIE Photonics West OPTO conference 11713: Next-Generation Optical Communication: Components, Sub-Systems, and Systems X.

We numerically show the applicability of standard 125 μm-cladding multi-core fiber (MCF) to long-haul and wide-band transmission in the S+C+L band. Although expanding the single-mode bandwidth is an effective way to increase the transmission capacity, the shortened cut-off wavelength degrades the XT and the A_eff. We numerically determine the optimum design of a four-core fiber with W-shape index profile considering the tradeoff relationship among the cut-off wavelength, A_eff, and XT. We show the design and applicability of a standard 125 μm-cladding MCF for S+C+L band transmission over long-haul distance of 1000 km and above with larger A_eff is possible from conventional single-mode fiber.

Multi-core fibers, few-mode fibers and their hybrid combination, few-mode-multi-core fibers are promising transmission media for future high-capacity, space-division multiplexed optical fiber transmission systems. In this paper, we report on our latest short and long-haul transmission demonstrations, including record breaking 10.66 Pb/s transmission in a 38-core, three-mode fiber as well as 172 Tb/s over more than 2000 km coupled-core three core fiber, using more than 75 nm bandwidth in C- and L-bands. We further discuss key transmission channel parameters, such as the impulse response time spread and mode-dependent loss and their consequences on the transmission performance.

We present recent progress on fabrication of heat induced long period gratings (LPGs) in few mode fibers for stable mode conversion between the fundamental mode LP₀₁ to asymmetric and symmetric modes, such as LP₁₁ and LP₀₂. A simple, effective, and low-cost method is demonstrated for fabricating heat induced LPGs, as an alternative method compared to more complicated approaches that require UV lasers and hydrogen loading or CO₂ lasers. The LPGs are written point-by-point by periodically translating and heating the fiber. The heating filament is realized by conducting electrical current through an omega shaped 0.25 mm electrical platinum wire that enclose the fiber. We expect that the physical mechanisms for the refractive index change are caused by a combination of residual stress relaxation and tapering of the fiber. A grating period down to 622 μm for coupling between the LP₀₁ and LP₀₂ is demonstrated, however, we believe grating periods of a few hundreds of microns are feasible.

Silica glass optical fibers have revolutionized data transmission, sensing and laser development over the past 50 years, however, dielectric waveguides with a hollow core offer exciting development possibilities beyond traditional technology. Hollow Core Optical Fibers (HCFs) have been fabricated over the past 20 years with various geometries and refinements reported over this time. Despite numerous design developments and predictions from theoretical studies, one of the key performance indicators of optical fibers – attenuation - has remained significantly higher than can be routinely achieved in standard silica single mode fibers. Here we present recent developments in Nested Anti-resonant Nodeless Fiber (NANF) design over the last few years and show how this rapidly developing technology has been refined to produce state of the art HCFs with attenuation = 0.28 dB/km at 1550 nm.

In this talk, we review advanced modulation and direct detection techniques for short-reach (~ 100 km) applications. The advanced formats and their associated receiver techniques can compensate/mitigate signal distortions from fiber dispersion, therefore improve transmission distance and per wavelength interface rate. The concepts that will be discussed include a wide range of self-coherent systems including single-side band modulation and Kramers-Kronig receivers, double side band modulation and Stokes receivers, signal-carrier-interleaved modulation.

We report world record high data transmission over standard optical fiber from a single optical source. We achieve a line rate of 44.2 Terabits per second (Tb/s) employing only the C-band at 1550nm, resulting in a spectral efficiency of 10.4 bits/s/Hz. We use a new and powerful class of micro-comb called soliton crystals that exhibit robust operation and stable generation as well as a high intrinsic efficiency that, together with an extremely low spacing of 48.9 GHz enables a very high coherent data modulation format of 64 QAM. We achieve error free transmission across 75 km of standard optical fiber in the lab and over a field trial with a metropolitan optical fiber network. This work demonstrates the ability of optical micro-combs to exceed other approaches in performance for the most demanding practical optical communications applications.

With an ever increasing amount of end user devices connected to the internet, the global data traffic, especially within data centers, increases significantly. In order to keep pace, the current 100 Gbps standard (4 lines x 25 Gbps) needs to be upgraded. There are several possibilities to increase the data rate per line. The easiest way is to use multilevel modulation formats such as PAM4 with 2 bit per symbol or PAM8 or 16. Furthermore, optical multiplexing should be taken into account to maximize the bandwidth usage. Especially, optical signal processing with Nyquist pulses shows no inter-symbol interference, exhibit a rectangular spectrum and enables transmission at the maximum possible symbol rate for a given bandwidth. Here we present a simplified concept for ideal Nyquist pulse generation and simultaneous data modulation using just a single modulator per channel. Thereby, a laser source is split into three branches and the data signal is mixed electrically with a sine wave and then transferred into the optical domain, leading to a modulated Nyquist pulse train. The time delay between each Nyquist Pulse sequence for multiplexing is realized by a simple phase shift of the sinusoidal signal. With 3 time-domain channels, the proposed method achieved an aggregate baud rate, which corresponds to the full optical bandwidth of the modulators. On the contrary, the electronics require only 1/3 of the bandwidth. Due to the simple setup, integration on a silicon photonics platform might be straight forward. Preliminary simulation results show data transmission with PAM4 modulation at low bit error rates.

Future cellular mobile networks will rely on hybrid 4G/LTE-5G technologies to provide wireless coverage and capacity that operators need for consistent service across their geographic footprint. However, this technology trend is creating many challenges in the mobile front-haul (MFH) networks to support the co-existence of Common Public Radio Interfaces (CPRI) and Evolved Common Public Radio Interfaces (eCPRI) traffic with diverse connectivity requirements in terms of capacity and reach. To address this problem, this paper presents a Discrete Multi-Tone modulation (DMT) ASIC fabricated in 16 nm CMOS process which supports flexible data rates in hybrid 4G/LTE-5G MFH networks, including CPRI-10, 25 GbE, 50 GbE, 75 GbE and 100 GbE (eCPRI rates). In addition, this ASIC performs stably over the full industrial temperature range (-40°C to +85°C), making it fully qualified for outdoor MFH applications. Using this DMT ASIC, we demonstrate 400 Gb/s real-time transmission over 40 km of standard single mode fiber (SSMF) in C-band without optical dispersion compensation.

The attenuation of GPS signals inside buildings has recently boosted research in the field of indoors navigation systems. Different solutions can be used to manage positioning and navigation services inside the buildings, that make use of different technologies. In this paper we propose an indoor navigation system based on Visible Light Communication (VLC). In this system navigation through a building is enabled by using the location information supplied by the lighting infrastructure. The application presented in this paper relates the use of robotics solutions within warehousing, a field where automation is directly related to reduce labor costs, minimize human error and create the potential to better use building space. In this paper we propose VLC based bi-directional communication among the infrastructure and guided vehicles to support navigation inside the indoors space of the warehouse and transmission of dedicated messages related to the operations managed by the vehicles. The communication network is supported by VLC emitters using tri-chromatic white LEDs and dedicated receivers based on a-SiC:H/a-Si:H photodiodes with selective spectral sensitivity. The downlink channel establishes the infrastructure to vehicle (I2V) link and transmits information through the modulation of the red and blue emitters of the RGB LEDs. Position information is provided by each LED lamp to the vehicle by suitable modulation of the RGB emitters. The decoding strategy is based on accurate calibration of the output signal. The uplink channel is used for the communication from the vehicle to the infrastructure (V2I). This link is established using a single optical signal. In this paper we present basic system requirements, give details on the network topology and discuss the methodology used to decode the multiplexed signal transmitted by simultaneous emitters.

This paper uses the concept of request/response for the management of a trajectory in a two-way-two-way traffic lights controlled crossroad, using Visible Light Communication (VLC). The connected vehicles receive information from the network (I2V), interact with each other (V2V) and with the infrastructure (V2I), using a request distance and pose estimation concept. In parallel, an intersection manager (IM) coordinates the crossroad and interacts with the vehicles (I2V) using the response distance and the pose estimation concepts. The communication is performed through VLC using the street lamps and the traffic signaling to broadcast the information. Data is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. As receivers and decoders, SiC Wavelength Division Multiplexer (WDM) devices, with light filtering properties, are used. A simulated Vehicle-to-Everything (V2X) traffic scenario is presented and a generic model of cooperative transmission established. The primary objective is to control the arrival of vehicles to the intersection and schedule them to cross at times that minimize delays. Bidirectional communication between the vehicles and the infrastructure is tested, using the VLC request/response distance and pose estimation concepts. A phasing traffic flow is developed as a proof of concept. The simulated/experimental results confirm the cooperative VLC architecture. Results show that the communication between connected cars is optimized using a request/response concept and that pose analysis is an important issue to control driver’s behavior in a crossroad. The block diagram conveys that the vehicle’s behavior (successive poses) is influenced by the manoeuvre permission, by the I2V messages and also by the intersection redesigned layout and presence of other vehicles. An increase in the traffic throughput with least dependency on infrastructure is achieved.

Silicon photonics (SiPh) are promising technologies for digital coherent optical communications because they can monolithically integrate all optical functions except for a laser, namely, modulators, mixers, photodiodes, a polarization beam splitter/combiner, and rotator, onto a single chip. We developed SiPh-based coherent optical subassemblies (COSAs) for various bit-rate systems. We review recent advances in SiPh technologies and discuss our experimental demonstration resulting in from 32-Gbaud to 96-Gbaud optical signal generation and detection for 100-Gbps to beyond 400-Gbps systems with our COSAs.

Integrated Kerr micro-combs are a powerful source of multiple wavelength channels for photonic radio frequency (RF) and microwave signal processing, particularly for transversal filter systems. They offer significant advantages featuring a compact device footprint, high versatility, large numbers of wavelengths, and wide Nyquist bands. We review progress photonic RF and microwave high bandwidth temporal signal processing based on Kerr micro-combs with comb spacings from 49GHz to 200GHz. We focus on integral and fractional Hilbert transforms, differentiators as well as integrators. The future potential of optical micro-combs for RF photonic applications in terms of functionality and ability to realize integrated solutions is also discussed.

A computationally efficient deep learning based digital backpropagation (DL-DBP) algorithm providing a 1.9 dB SNR over a conventional linear compensation (chromatic dispersion compensation algorithm) and a 1 dB gain over a conventional back-propagation algorithm of the same complexity is presented. The algorithm has been tested in a 1200km transmission experiment. Also, if the algorithm is tested against a conventional digital backpropagation algorithm with the gain, then the new algorithm requires a factor 6 lower complexity. We discuss its training procedure and its principle. We discuss its training procedure and its principle.

Artificial intelligence (AI) has shown significant performance in optical network control and management. However, the reliability, complexity and deployment procedure of these AI-based applications need further investigation. To efficiently speed up the network automation and function extension, a digital-twin-based network control framework is proposed, which can intelligently synchronize with the practical system to support the upper-layer applications. To build a digital twin, high efficiency modeling, monitoring and self-learning mechanisms are the key building blocks. In this paper, we discuss our recent works on modeling, monitoring and self-learning methods for building a digital-twin for optical networks.

A bandpass filter with a flat-top transmission is highly essential for various applications in optical communications. Previously, bandpass filters are designed by optimizing reflectivities of multistage Faby-Perot with equal length cavities. In these prior cases, at least the same number of equal length cavities are required as the filter’s designed order. Here, we present a novel digital synthesis technique to achieve a ripple-free passband transmission by optimizing the multistage etalons’ unequal cavity lengths. We find that the number of cavities is less than half of the designed filter order with our approach. As an example, we design a Chebyshev bandpass optical filter with ripples less than 0.0001 dB in the passband, stopband peak rejection of less than -50dB, and isolation among the neighboring channels greater than 60 dB. The desired filter is designed and estimated its transfer function in the z-domain. It is then refined by changing the denominator and numerator polynomials’ powers in a set pattern iteratively and compared the response with the desired one using predictive-error-method to get the transfer function of unequal cavity multistage Fabry-Perot with least mean-square-error. Using our proposed procedure, we realize the filter by determining the required number of cavities and their respective lengths by assuming fixed reflectivities of reflectors. This work is easily generalizable to ring resonators and Fiber-Bragg-grating based cavities.

In this work, 4×4 Multiple-Input Multiple-Output Visible Light Communication (MIMO-VLC) system architecture is proposed with the capability of serving up to six users. Each transmitter has four LEDs and each receiver has four photodetectors. Therefore, the link between the transmitter and any user has different sixteen routs. The proposed system used non-orthogonal multiple access (NOMA) to utilize the system bandwidth. Numerical simulation is applied to evaluate the system performance. The relation between normalized offset and sum rate is analyzed and discussed. The results show that the system sum rate has been improved at the system edge with increasing the number of users. On the other hand, adding extra users affects the average bit rate allowed for each user. Thus, the relation between the number of users and the normalized offset is provided. The benefits and drawbacks of adding extra users to the proposed system are also discussed through this work.

Overcoming bandwidth limitations is of immense interest in optical signal processing. We propose to use a Mach-Zehnder modulator inside an integrated ring, which multiplies the same signal multiple times with sampling pulses of different time shifts, leading to higher sampling rates. In proof-of-concept experiments with a fiber ring, we have realized the sampling of an optical periodic pulse train (signal) by a multiplication with sampling pulses with 2.7 times the bandwidth of the modulator driving signal. This was achieved by applying an electrical multitone signal to the modulator with a frequency spacing close to the fundamental resonance of the ring. The modulator converts the electrical multitone signal into optical sampling pulses and the consecutive multiplication of these pulses with the signal to sample at slightly shifted positions enables very short pulses. The frequency mismatch between the multitone signal and the ring resonance ensures that the frequency components of the sampling pulses are not distorted by the frequency selectivity of the ring. The setup operates like a row of cascaded modulators driven with time-shifted sampling pulses. The method might enable an accurate waveform characterization for high-bandwidth optical periodic pulse trains.

In order to cope with the fast increase in data traffic demand, optical networks are fast evolving towards the disaggregation and progressive implementation of the openness paradigm. Such an evolution is enabling the application of the software-defined networking below the IP layer, down to the optical transmission (SD-OTN). SD-OTN is enabled by the capability of the network controller to automatized management of photonic switching systems, and allowing their full virtualization and softwarisation. To this purpose, one of the major matter of contention is an efficient utilization of routing strategies, which can be seamlessly incorporated into the control plane. In this work, we rely on data-driven science (DDS) to develop the machine learning (ML) model which is able to predict the routing strategies of generic N x N photonic switching system without any knowledge required of the topology. The dataset used for training and testing the ML model is generated “synthetically”. In particular, the training and testing of the proposed ML module is done in a completely topological and technological agnostic way and is able to perform its application in real-time. Furthermore, the scalability and accuracy of the proposed approach is verified by considering two different switching topologies: the Honey-Comb Rearrangeable Optical Switch and the Beneš network. Promising results are achieved in terms of predicting the control signals matrix for both of the considered topologies.