Eduardo Temprana

Overcoming Kerr-induced capacity limit in optical fiber transmission

Getting around the capacity crunch The growing appetite for an ever-faster Internet and enhanced long-haul communication requires the pumping of more light down optic fibers. However, light-induced nonlinearities limit how much light can be pumped into the fiber without compromising the signal. This limitation has led to the prospect of a “capacity crunch.” Temprana et al. eliminated the effects of nonlinearity by using digital back-propagation methods with mutually coherent laser pulses from a single frequency comb. Science, this issue p. 1445 Digital back-propagation is used to mitigate light-induced nonlinear effects in optic fiber. Nonlinear optical response of silica imposes a fundamental limit on the information transfer capacity in optical fibers. Communication beyond this limit requires higher signal power and suppression of nonlinear distortions to prevent irreversible information loss. The nonlinear interaction in silica is a deterministic phenomenon that can, in principle, be completely reversed. However, attempts to remove the effects of nonlinear propagation have led to only modest improvements, and the precise physical mechanism preventing nonlinear cancellation remains unknown. We demonstrate that optical carrier stability plays a critical role in canceling Kerr-induced distortions and that nonlinear wave interaction in silica can be substantially reverted if optical carriers possess a sufficient degree of mutual coherence. These measurements indicate that fiber information capacity can be notably increased over previous estimates.

Wideband Parametric Frequency Comb as Coherent Optical Carrier

We report the first use of the CW-seeded parametric comb as a multiwavelength source for coherent channel transmitters. The new comb source relies on a multistage parametric mixer design seeded by a single kilohertz-linewidth master laser. The resultant frequency comb provides more than 120 tones in a 100-nm-wide continuous band, all possessing kilohertz-scale linewidth inherited from the master laser. The applicability of the new comb source as a coherent channel carrier was quantified by error-vector magnitude and bit-error rate metrics of individual spectral lines modulated by QPSK signaling. The performance of the new source exceeded that of the standard tunable coherent transmitter while providing a qualitatively lower frequency uncertainty and drift.

Nonlinearity Cancellation in Fiber Optic Links Based on Frequency Referenced Carriers

We study the limitations and their origins in the nonlinear effects mitigation in fiber-optic communication systems. The carrier frequencies uncertainty and their stochastic variations are identified as the major impeding factor for successful inter-channel nonlinear impairments management. Furthermore, the results clearly point out to the significant benefits of employing fully frequency referenced carriers in transmission, with frequency combs representing an immediately available solution. Finally, frequency referenced transmitters and/or receivers are shown as critical for availing longer reach at high spectral efficiencies in transmission.

Ultrahigh Count Coherent WDM Channels Transmission Using Optical Parametric Comb-Based Frequency Synthesizer

A novel optical frequency synthesizer capable of generating a multitude of narrow linewidth oscillations, fully compatible with high-speed fiber-optic transmission requirements, is presented. The new device is based on an ultra-dense and wideband parametric comb capable of generating more than 1800 spectral lines with 6.25 GHz spacing within 100 nm (C + L band) of optical bandwidth and 3 dB spectral flatness. The parametric comb generation relies on the highly efficient nonlinear interaction of the ultra-short and high peak power pulse train in the precisely controlled dispersive medium. The generated comb source is used for coherent transmission of 1520 Nyquist ultra-dense wavelength division multiplexed channels in a flex-grid compatible optical access network architecture, offering up to 30 Gb/s per user over a 50 km of standard single mode fiber with estimated aggregate capacity of 32 Tb/s. The line spacing tunablity and one-to-multiple coherent cloning capability make the proposed multicarrier generator a strong contender fully capable of replacing thousands of discrete lasers in optical data communication systems.

Two-fold transmission reach enhancement enabled by transmitter-side digital backpropagation and optical frequency comb-derived information carriers

We demonstrate a two-fold reach extension of 16 GBaud 16-Quadrature Amplitude Modulation (QAM) wavelength division multiplexed (WDM) system based on erbium doped fiber amplifier (EDFA)-only amplified standard and single mode fiber -based link. The result is enabled by transmitter-side digital backpropagation and frequency referenced carriers drawn from a parametric comb.

A fully frequency referenced parametric polychromatically sampled analog-to-digital conversion

We present a novel scalable photonically-sampled analog-to-digital-converter based on parametric multicasting, polychromatic sampling and frequency referenced lasers. A sampling rate of 30-GS/s is achieved with three subrate-channels with a 6.2-ENOB performance of a 19-GHz signal.

All optical wavelength multicaster and regenerator based on four-mode phase-sensitive parametric mixer

Four-mode phase-sensitive (4MPS) process has been employed in a parametric mixer based wavelength multicaster, enhancing the multicasting conversion efficiency and signal-to-noise ratio. In addition, the 4MPS parametric multicaster is an outstanding candidate for all-optical regeneration, owing to its inherent capabilities to clamp amplitude fluctuations by the saturated parametric effect and to squeeze phase distortions by the phase sensitive process. The investigation in this paper focuses on the 4MPS multicaster operated in the saturation gain regime, including theoretical simulations and experimental demonstrations on amplitude and phase noise regeneration over 20 multicasting signal copies.

Demonstration of local-oscillator phase-noise tolerant 40 GBaud/s coherent transmitter

A new transmitter architecture for local-oscillator phase-noise resilient coherent transmission is introduced. The technique is experimentally implemented and less than 0.5dB penalty in the detection of 40GBaud/s data with a 5 GHz-wide LO is demonstrated.

Transmitter-Side Digital Back Propagation With Optical Injection-Locked Frequency Referenced Carriers

A 100% reach extension is demonstrated in a coherent four-channel wavelength division multiplexed system by employing full-bandwidth frequency-referenced transmitter-side digital back propagation. Frequency referenced optical carriers are generated by injection locking distributed feedback lasers to a reference optical frequency comb and the performance of digital back propagation is evaluated with and without the frequency reference. In addition, we investigate the effect of an implementation with reduced computational complexity by limiting the number of steps-per-span used in the back propagation computation. Lastly, we measure the penalties generated by an inaccurate fiber dispersion parameter in the back propagation model.

Dynamic reconfiguration of parametric frequency comb for superchannel and flex-grid transmitters

We propose and demonstrate a parametric frequency comb architecture with dynamically reconfigurable carrier frequency grid for superchannel and flex-grid elastic transmitters. Performance of 16-QAM signal generation was characterized for 100 GHz, 25 GHz, 12.5 GHz and 6.25 GHz frequency spacing.