Jose A. Altabas

1Gbps full-duplex links for ultra-dense-WDM 6.25GHz frequency slots in optical metro-access networks

1 Gbps full-duplex optical links for 6.25 GHz ultra dense WDM frequency slots are demonstrated and optimized for cost-effective metro-access networks. The OLT-ONU downlinks are based on 1 Gbps Nyquist-DPSK using MZM and single-detector heterodyne reception obtaining a sensitivity of -52 dBm. The ONU-OLT uplinks are based on 1 Gbps NRZ-DPSK by directly phase modulated DFB and also single-detector heterodyne reception obtaining same sensitivity of -52 dBm. The power budget of full-duplex link is 43 dB. These proposed links can provide service to 16 (32) users at each 100 (200) GHz WDM channel.

Cost-Effective Transceiver Based on an RSOA and a VCSEL for Flexible uDWDM Networks

A cost-effective transceiver for a 1-Gb/s full-duplex ultra-dense wavelength division multiplexing optical link is proposed for flexible metro-access and 5G networks. The transceiver is based on a vertical cavity surface emitting laser, which is used as the local oscillator for a heterodyne receiver and also feeds a phase-modulated reflective semiconductor optical amplifier (RSOA) transmitter. The modulation format used in the RSOA is a nonreturn-to-zero differential binary phase shift keying (DPSK) for the uplink, while the downlink is based on a Nyquist DPSK format. The central frequencies of the links are 2 GHz separated, and both links can be placed inside a 6.25-GHz frequency slot. The sensitivity of this transceiver is -43.5 dBm over a 50-km fiber.

Flexible PON Key technologies: Digital advanced modulation formats and devices

Flexible PON are future paradigm in parallel with flexible and elastic optical networks are under research for core networks. In the same way as those backbone optical networks can be significantly improved by following software-defined network (SDN) techniques, it is described how SDN PONs can be implemented by highly spectral efficient digital modulation formats. A main challenge is the implementation by cost effective devices. We will show the progress in alternatives implementations and adequacy of diverse modulation formats to cost effective bandwidth limited optical sources and receivers.

SDN-enabled flexible optical node designs and transceivers for sustainable metro-access networks convergence

The Internet data traffic constant growth caused by the popularization of cloud services, mobile and social networks, is being stressed by the advent of 5G technologies. Hence, architectural changes are required at the underlying networks to support the expected traffic volume growth, whereas providing a highly dynamic connectivity. Cost-effective and energy efficient solutions for flexible network subsystems are required in order to provide future sustainable networks. In this paper, we present flexible optical node designs (ROADM and OXC) and transceivers, remotely managed by a Software Defined Networking (SDN) controller, able to satisfy the requirements of future metro-access networks in support of 5G services. In particular, the overall architecture including both the novel data plane devices and the SDN control plane is discussed.

Survey of Faster-Than-Nyquist for Flexible Passive Optical Networks

The constant growing in traffic demands has driven to look for new methods with which to reduce the occupied bandwidth and efficient use of the optical spectrum. Despite non-orthogonal signalling lead to intersymbolic interference introduction, it can be considered as a promising solution if interference is introduced in a controlled manner. In this paper the modulation scheme called Faster-Than-Nyquist (FTN) is presented for Flexible Passive Optical Networks application. Different ratios of bandwidth reduction vs. power penalty are presented and compared to the Nyquist modulation.

Chirp-based direct phase modulation of VCSELs for cost-effective transceivers

A 2.5  Gb/s differential binary phase-shift keying (DPSK) transmitter based on direct phase modulation of a vertical cavity surface emitting lasers (VCSEL) using its own chirp is proposed. The VCSEL, which has a wavelength of 1539.84 nm, has been characterized both statically and dynamically. The sensitivity of a single photodiode heterodyne receiver using the proposed 2.5  Gb/s VCSEL transmitter is -39.5  dBm. Thus, this transmitter is an extremely cost-effective solution for future access networks.

Graphene Silicon ring resonators for wavelength routers in Photonic Network-on-Chip

We propose graphene integrated Silicon waveguides in ring-resonator structures for broad spectrum, compact, high speed Silicon wavelength routers and filters for future Photonic Network-on-Chip. Analytical model shows > 2 THz FSR adequate for > 10 WDM channels at 200 GHz with passing-(drop-)losses in the range of 0.2 to 0.8 dB (6 to 3 dB), respectively.

Transparent service delivery in elastic metro/access networks with cost-effective programmable transceivers

In this paper, we present and experimentally validate a transparent signal delivery scheme using programmable sliceable bandwidth/bit rate variable transceivers (S-BVTs), for converged optical access/metro networks. A programmable transceiver based on discrete multitone (DMT) directly modulated vertical cavity surface-emitting laser (VCSEL) and direct detection (DD) is proposed to efficiently increase the cost-effectiveness and scalability of the network. Variable data rates are enabled for a maximum optical spectrum occupancy of 9 GHz, while coping with a minimum power budget of 20 dB in the access segment. This allows to fully exploit system flexibility while enabling photonic integration.

MultiCAP modulation for high spectral efficiency transmission over SI-POF

Plastic optical fiber (POF) has been considered as a low-cost alternative to traditional copper cabling for indoor and industrial networks. Large core step index plastic optical fibers (SI-POFs) are lightweight and robust with a safe and an easy installation. These advantages are coupled with high attenuation and dispersion that have so far limited its use to short reach and low bit rate applications. Nowadays, new multimedia services require higher data rates and longer distances, and complex modulation techniques, such as pulse amplitude modulation (PAM) or carrierless amplitude phase (CAP) modulation, have been proposed to reach these new requirements [1]. However, both modulations are very sensitive to non-flat spectral links, such as the POF one, and require very complex equalizers. To solve this important issue, we propose a multiband approach to CAP signalling (MultiCAP), where the CAP signal is divided into smaller bands [2]. MultiCAP have the same advantages of CAP such as lower peak-to-average power ratio (PAPR) and high spectral efficiency, and, additionally, the CAP filters become easier to realize, since the frequency bands covered by each pair of filters are narrowed down. Another advantage of MultiCAP is the possibility to use different modulation orders in each band to accommodate different bitrate or to compensate the dispersion or losses in the link.

Nonorthogonal multiple access and carrierless amplitude phase modulation for flexible multiuser provisioning in 5G mobile networks

In this paper, a combined nonorthogonal multiple access (NOMA) and multiband carrierless amplitude phase modulation (multiCAP) scheme is proposed for capacity enhancement of and flexible resource provisioning in 5G mobile networks. The proposed scheme is experimentally evaluated over a W-band millimeter wave radio-over fiber system. The evaluated NOMA-CAP system consists of six 1.25-GHz multiCAP bands and two NOMA levels with quadrature phase-shift keying and can provide an aggregated transmission rate of 30 Gbit/s. The proposed system can dynamically adapt to different user densities and data rate requirements. Bit error rate performance is evaluated in two scenarios: a low user density scenario where the system capacity is evenly split between two users and a high user density scenario where NOMA and multiCAP are combined to serve up to 12 users with an assigned data rate of 2.5 Gbit/s each. The proposed system demonstrates how NOMA-CAP allows flexible resource provisioning and can adapt data rates depending on user density and requirements.