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International audience; A 100 Gbit/s/λ PAM-4 fiber link with an optical budget of 30 dB and 20 km fiber reach is achieved in real time experiments. This is compliant with class A (20 dB) point to point (PtP) applications as mobile fronthaul for example, and with class N1 (29 dB) point to multipoint (PtMP) for residential market. We used an integrated externally modulated laser, an analog pre-equalizer, an optical booster amplifier and/or non-filtered preamplifier and direct detection without any digital signal processing (whether real-time or offline).

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. We experimentally demonstrate an innovative ultradense wavelength division multiplexing (UDWDM) passive optical networks (PON) that implements the full ¿-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 6.25-GHz grid), real-time GbE transmissions (by using either fully analog or light digital signal processing), multirate transmission (1.25 and 10 Gb/s), high optical distribution network loss (18-40 dB) as well as a bidirectional channel monitoring system.

A monolithically integrated dual electroabsorption modulated laser (DEML), consisting of distributed feedback laser (DFB) and electroabsorption modulator (EAM) sections, is proposed as a transmitter in an optical network unit with phase-shift keying (PSK) modulation. The DFB is directly modulated in phase, and the EAM section is applied for mitigating the residual amplitude modulation. The DEML, as compared with external phase modulator, has advantages of low cost, simplified design, low footprint, and reasonable power consumption, thus making it attractive for an ultradense wavelength division multiplexing passive optical unit. The system is validated at 2.5 and 5 Gb/s with intradyne detection.

We present a coherent ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) with enhanced spectral efficiency. The benefit of using Gaussian or Nyquist pulse-shaping filters at the transmitter is evaluated through numerical simulations and experiments. The transmitters consist of directly phase modulated distributed feedback (DFB) lasers through beat signals whose duty-cycle and amplitude are digitally adjusted. The results show that transmitting a Nyquist-shaped signal achieves a 25% spectral saving allowing to place 2.5 Gb/s/user data in 6.25 GHz channels. Furthermore, the proposed transmitter tolerates differential link-losses of 15 dB at Rx sensitivity of ¿44 dBm at BER=10¿3 with intradyne detection.

We compare three clipping techniques for reducing the PAPR of an UFMC signal over an AWGN channel. First, the techniques are analyzed probabilistically showing that deep clipping reduces the most, but it also has the worst performance. Then, the percentile levels of deep factor and level clipping are optimized, achieving similar performance that common techniques.

Coherent ultra-dense wavelength division multiplexing (UDWDM) architecture constitutes an approach to serve hundreds of users in a passive optical network (PON) with high spectrum efficiency. We propose and experimentally test a directly phase modulated distributed feedback (DFB) laser with a Nyquist shaped beat signal. An Rx sensitivity of −44 dBm at BER=10e-3 is achieved for dedicated 2.5 Gb/s/user in only 6.25 GHz spaced. Even more, the proposed technique tolerates a differential link-loss of 15 dB.