Oriol Bertran-Pardo

Bio: Oriol Bertran-Pardo is an academic researcher from Bell Labs. The author has contributed to research in topics: Wavelength-division multiplexing & Phase-shift keying. The author has an hindex of 19, co-authored 52 publications receiving 830 citations.

72×100Gb/s transmission over transoceanic distance, using large effective area fiber, hybrid Raman-Erbium amplification and coherent detection

Abstract: 100Gb/s channels are transmitted over 7,040km. After propagation across eighty-eight 80km-long sections of large effective area fiber, separated by Raman-assisted erbium repeaters, demodulation of PDM-QPSK waveforms is performed with digital processing in a coherent receiver.

Flexible TDMA access optical networks enabled by burst-mode software defined coherent transponders

Abstract: We propose a concept of flexible PON and show with experiments and network dimensioning how burst-mode, software-defined coherent transponders can more than double the average capacity per user in TDMA access networks.

Comparison of set-partitioned two-polarization 16QAM formats with PDM-QPSK and PDM-8QAM for optical transmission systems with error-correction coding

Abstract: We compare set partitioned two-polarization 16QAM formats with conventional PDM-QPSK and PDM-8QAM formats by considering error correction coding. We particularly show that 128SP-16QAM appear as a competitive alternative to PDM-8QAM for spectrally efficient (>4 b/s/Hz) optical transmission systems using forward error-correction coding.

Spectrally efficient long-haul transmission of 22-Tb/s using 40-Gbaud PDM-16QAM with coherent detection

Abstract: We report on the transmission of 1-Tb/s clusters of channels, composed by four 50-GHz-spaced WDM channels modulated with 40-Gbaud PDM-16QAM. We transmit 22-Tb/s data over 2,400 km, with a spectral efficiency of 5 bit/s/Hz.

Experimental transmission of Nyquist pulse shaped 4-D coded modulation using dual polarization 16QAM set-partitioning schemes at 28 Gbaud

Abstract: We report the experimental transmission of 4-D coded modulation formats based on set-partitioning of two 16QAM 2-D constellations. Using Nyquist-pulse-shaping, 32SP-DP-16QAM and 128SP-DP-16QAM signals are transmitted over long-haul distance and compared with PDM-16QAM.

Digital Coherent Optical Receivers: Algorithms and Subsystems

Abstract: Digital coherent receivers have caused a revolution in the design of optical transmission systems, due to the subsystems and algorithms embedded within such a receiver. After giving a high-level overview of the subsystems, the optical front end, the analog-to-digital converter (ADC) and the digital signal processing (DSP) algorithms, which relax the tolerances on these subsystems are discussed. Attention is then turned to the compensation of transmission impairments, both static and dynamic. The discussion of dynamic-channel equalization, which forms a significant part of the paper, includes a theoretical analysis of the dual-polarization constant modulus algorithm, where the control surfaces several different equalizer algorithms are derived, including the constant modulus, decision-directed, trained, and the radially directed equalizer for both polarization division multiplexed quadriphase shift keyed (PDM-QPSK) and 16 level quadrature amplitude modulation (PDM-16-QAM). Synchronization algorithms employed to recover the timing and carrier phase information are then examined, after which the data may be recovered. The paper concludes with a discussion of the challenges for future coherent optical transmission systems.

Software Defined Optical Networks (SDONs): A Comprehensive Survey

Abstract: The emerging software defined networking (SDN) paradigm separates the data plane from the control plane and centralizes network control in an SDN controller. Applications interact with controllers to implement network services, such as network transport with quality of service. SDN facilitates the virtualization of network functions so that multiple virtual networks can operate over a given installed physical network infrastructure. Due to the specific characteristics of optical (photonic) communication components and the high optical transmission capacities, SDN-based optical networking poses particular challenges, but holds also great potential. In this article, we comprehensively survey studies that examine the SDN paradigm in optical networks; in brief, we survey the area of software defined optical networks (SDONs). We mainly organize the SDON studies into studies focused on the infrastructure layer, the control layer, and the application layer. Moreover, we cover SDON studies focused on network virtualization, as well as SDON studies focused on the orchestration of multilayer and multidomain networking. Based on the survey, we identify open challenges for SDONs and outline future directions.

Improved single channel backpropagation for intra-channel fiber nonlinearity compensation in long-haul optical communication systems

Abstract: Backpropagation has been shown to be the most effective method for compensating intra-channel fiber nonlinearity in long-haul optical communications systems. However, effective compensation is computationally expensive, as it requires numerous steps and possibly increased sampling rates compared with the baud rate. This makes backpropagation difficult to implement in real-time. We propose: (i) low-pass filtering the compensation signal (the intensity waveform used to calculate the nonlinearity compensation) in each backpropagation step and (ii) optimizing the position of the nonlinear section in each step. With numerical simulations, we show that these modifications to backpropagation improve system performance, reducing the number of backpropagation steps and reducing the oversampling for a given system performance. Using our ‘filtered backpropagation’, with four backpropagation steps operating at the same sampling rate as that required for linear equalizers, the Q at the optimal launch power was improved by 2 dB and 1.6 dB for single wavelength CO-OFDM and CO-QPSK systems, respectively, in a 3200 km (40 × 80km) single-mode fiber link, with no optical dispersion compensation. With previously proposed backpropagation methods, 40 steps were required to achieve an equivalent performance. A doubling in the sampling rate of the OFDM system was also required. We estimate this is a reduction in computational complexity by a factor of around ten.

Design of Low-Margin Optical Networks

Abstract: We review margins used in optical networks and review a formerly proposed margin taxonomy. For each category of margins, we review techniques that the network designer can use in order to increase the capacity of optical networks, extend their life, and decrease deployment cost (CAPEX) or total cost of ownership over their life duration. Green field (new network deployments) and brown field techniques (used after initial network deployment) are discussed. The technology needed to leverage the margins and achieve the aforementioned gains are also reviewed, along with the associated challenges.

Fiber Impairment Compensation Using Coherent Detection and Digital Signal Processing

Abstract: Next-generation optical fiber systems will employ coherent detection to improve power and spectral efficiency, and to facilitate flexible impairment compensation using digital signal processors (DSPs). In a fully digital coherent system, the electric fields at the input and the output of the channel are available to DSPs at the transmitter and the receiver, enabling the use of arbitrary impairment precompensation and postcompensation algorithms. Linear time-invariant (LTI) impairments such as chromatic dispersion and polarization-mode dispersion can be compensated by adaptive linear equalizers. Non-LTI impairments, such as laser phase noise and Kerr nonlinearity, can be compensated by channel inversion. All existing impairment compensation techniques ultimately approximate channel inversion for a subset of the channel effects. We provide a unified multiblock nonlinear model for the joint compensation of the impairments in fiber transmission. We show that commonly used techniques for overcoming different impairments, despite their different appearance, are often based on the same principles such as feedback and feedforward control, and time-versus-frequency-domain representations. We highlight equivalences between techniques, and show that the choice of algorithm depends on making tradeoffs.