Robert Pous

Bio: Robert Pous is an academic researcher from Ericsson. The author has contributed to research in topics: Passive optical network & Fiber optic splitter. The author has an hindex of 4, co-authored 6 publications receiving 135 citations.

Towards ultra-dense wavelength-to-the-user: The approach of the COCONUT project

Abstract: This paper presents the high-level COCONUT architecture of an optical access network based on coherent technology, supporting ultra-dense Wavelength Division Multiplexing (WDM). The COCONUT network should allow for seamless evolution from present PON architectures, but also support new emerging applications such as mobile back-haul and front-haul. Coherent techniques will hence allow serving a higher number of users, thanks to ultra-dense WDM, and reaching higher power budget, thanks to higher sensitivity. These features should allow for economy of scale and network consolidation. Although coherent solutions are well-developed for core networks, the prohibitive cost of their optical and electronic parts makes them unsuitable for the massive deployment of access networks. To this aim, COCONUT will address realization of coherent transmitter/receivers exploiting low-cost components and simple electronics, so that the cost of typical line terminals would be affordable to the end-users. The paper presents an overview of the target results and key issues that are addressed by the COCONUT partners.

Technologies for Cost-Effective udWDM-PONs

Abstract: New technologies for ultradense WDM-PON (udWDM-PON), enabled by coherent techniques and low-cost devices, are developed for an efficient utilization of the optical spectrum, revealing that the “Wavelength-to-the-User” concept can be feasible. In this paper, an udWDM-PON with only 6.25-GHz channel spacing is implemented with conventional DFB lasers, for a splitter-based PON infrastructure with 256 ONUs. The results of the analysis of udWDM access network architecture with respect to their associated complexity, cost, and migration scenarios, exhibit the potential for higher aggregate throughput, higher split ratios, and node consolidation, when compared to competing technologies.

Field-Trial of a High-Budget, Filterless, $\lambda$ -to-the-User, UDWDM-PON Enabled by an Innovative Class of Low-Cost Coherent Transceivers

Abstract: We experimentally demonstrate an innovative ultradense wavelength division multiplexing (UDWDM) passive optical networks (PON) that implements the full $\lambda \text {-to-the-user}$ concept in a filterless distribution network. Key element of the proposed system is a novel class of coherent transceivers, purposely developed with a nonconventional technical approach. Indeed, they are designed and realized to avoid D/A–A/D converter stages and digital signal processing in favor of simple analog processing so that they match system, cost, and power consumption requirements of the access networks without sacrificing the overall performance. These coherent transceivers target different use case scenarios (residential, business, fixed, wireless) still keeping perfect compatibility and co-existence with legacy infrastructures installed to support gray, time division multiplexed PON systems. Moreover, the availability of coherent transceivers of different cost/performance ratios allows for deployments of different quality service grades. In this paper, we report the successful field trial of the proposed systems in a testbed where 14 UDWDM channels (and one legacy E-PON system) are transmitted simultaneously in a dark-fiber network deployed in the city of Pisa (Italy), delivering real-time and/or test traffic. The trial demonstrated filterless operations (each remote node selects individually its own UDWDM channel on a fine $\text{6.25}\text{-}\text {GHz}$ grid), real-time GbE transmissions (by using either fully analog or light digital signal processing), multirate transmission ( $\text{1.25}\; \text{and}\; \text{10}\,\text {Gb/s}$ ), high optical distribution network loss (18–40 dB) as well as a bidirectional channel monitoring system.

Ultra-dense WDM access network field trial

Abstract: An UDWDM-PON with simple real-time ASK and DPSK transceivers at 6.25 GHZ channel spacing is validated in a field-trial with deployed fiber with power budget above 40 dB. This work presents final results of the Coconut European Project.

Field-trial of a λ-to-the-user high-budget PON using a novel class of low-cost coherent transceivers and compatible with EPON system operation

Abstract: COCONUT project demonstrated an innovative DWDM Passive Optical Network implementing the full λ-to-the-user concept in a filterless distribution fiber network. We make use of an innovative class of coherent transceivers that exploit the advantages of coherent detection in terms of sensitivity and channel selectivity in a cost efficient manner. The different transceivers developed target different use case scenarios, showing perfect compatibility with legacy infrastructures installed. In this paper, we report the successful trial of the proposed system in a testbed where 4 different coherent transceivers (plus one legacy E-PON system) ran simultaneously, operating over 14 DWDM channels, in a dark-fiber network in the city of Pisa, delivering real-time and/or test traffic. The testbed demonstrated filterless operations, multi-rate transmission (from 1.25 to 10 Gb/s/λ), high ODN loss (18 – 40 dB) as well as a bi-directional channel monitoring system.

Roadmap of optical communications

Abstract: Lightwave communications is a necessity for the information age. Optical links provide enormous bandwidth, and the optical fiber is the only medium that can meet the modern society's needs for transporting massive amounts of data over long distances. Applications range from global high-capacity networks, which constitute the backbone of the internet, to the massively parallel interconnects that provide data connectivity inside datacenters and supercomputers. Optical communications is a diverse and rapidly changing field, where experts in photonics, communications, electronics, and signal processing work side by side to meet the ever-increasing demands for higher capacity, lower cost, and lower energy consumption, while adapting the system design to novel services and technologies. Due to the interdisciplinary nature of this rich research field, Journal of Optics has invited 16 researchers, each a world-leading expert in their respective subfields, to contribute a section to this invited review article, summarizing their views on state-of-the-art and future developments in optical communications.

Integrated Wireless Backhaul Over Optical Access Networks

Abstract: Recent technological advances and deployments are creating a new landscape in access networks, with an integration of wireless and fiber technologies a key supporting technology. In the past, a separation between those with fiber in the access networks and those with wireless networks, the relatively low data-rate requirements of backhaul and the relatively large cell sites, have all combined to keep fiber deployment low in wireless backhaul. As fiber has penetrated the access network and the latest wireless standards have demanded smaller, higher bandwidth cells, fiber connectivity has become key. Choices remain as to where the demarcation between key elements should be in the network and whether fiber should be used as just a high data-rate backhaul path or if a transition to radio-over-fiber techniques can afford benefits. This paper will explore the network options available in particular those demonstrated in recent European Union (EU) projects, how they can be integrated with existing access networks and how techniques such as radio-over-fiber can be deployed to offer increased functionality.

Coherent Access: A Review

Abstract: In this paper, we will address the benefits of the coherent detection in future optical access networks. The scarcity of the optical spectrum, the required flexibility, and constant evolution of requirements highlight the effectiveness of coherent techniques toward the future passive optical networks (PON). A set of architectures for coherent optical access networks will be presented and the key attributes of each scenario will be investigated. In addition, as a basis to decrease the cost of the local oscillator (LO) at customer side, we experimentally investigate the possibility of using a low-cost laser as LO with real-time detection of a Nyquist-shaped differential quadrature phase-shift keying (DQPSK) signal using simple 8-bit digital signal processing (DSP) on a field-programmable gate array. Moreover, we experimentally derive a set of optimized parameters and their impact on the network operation for coherent ultradense wavelength-division multiplexing (UDWDM) systems. The balance between the number of channels, power budget, and dynamic power range will be evaluated. Furthermore, we demonstrate a reconfigurable real-time receiver DSP for future flexible UDWDM-PON systems applying the DQPSK and D8PSK modulation formats. By reviewing some of the motivations for this technology, such as flexibility, spectral efficiency, as well as compatibility with software-defined networking, we show that this technology is approaching the required maturity.

Polarization-Independent Receivers for Low-Cost Coherent OOK Systems

Abstract: We demonstrate analytically a novel scheme to obtain polarization-independent operation in low-cost coherent OOK receivers, suitable for access networks. We move from a well-known phase-diversity receiver, exploiting a 3 × 3 coupler, three photodiodes, and basic analogue processing. If that receiver is modified to inject the local oscillator (or the signal) into two inputs with proper polarization states, we show, by both mathematical derivation and numerical simulations, that the resulting electrical signal can be polarization-independent; this is attained only if the frequency-detuning between the signal carrier and the local oscillator is high enough, so that intrinsic second order distortions can be spectrally isolated and suppressed by the low-pass filtering of the receiver.

Direct Phase Modulation DFBs for Cost-Effective ONU Transmitter in udWDM PONs

Abstract: A technique for direct phase modulating a low-cost distributed feedback laser is presented for user transmitter in ultra dense wavelength division multiplexing passive optical networks. It consists of a simple RC network, which equalizes the phase response. The method is tested with differential phase-shift keying modulation and heterodyne coherent detection at 1.25 and 2.5 Gb/s showing a penalty <;1 dB at BER = 10-3 compared with external phase modulation.