Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.

/pdf/terabit-free-space-data-transmission-employing-orbital-47zsgn5cdx.pdf

Terabit free-space data transmission employing orbital angular momentum multiplexing

This Review summarizes the simultaneous transmission of several independent spatial channels of light along optical fibres to expand the data-carrying capacity of optical communications. Recent results achieved in both multicore and multimode optical fibres are documented.

/pdf/space-division-multiplexing-in-optical-fibres-9acl86j916.pdf

Space-division multiplexing in optical fibres

Nonlinear photonic chips can generate and process signals all-optically with far superior performance to that possible electronically — particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics, its high two-photon absorption at telecommunication wavelengths poses a fundamental limitation. We review recent progress in non-silicon CMOS-compatible platforms for nonlinear optics, with a focus on Si3N4 and Hydex®. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We highlight their potential future impact as well as the challenges to achieving practical solutions for many key applications. This article reviews recent progress in the use of silicon nitride and Hydex as non-silicon-based CMOS-compatible platforms for nonlinear optics. New capabilities such as on-chip optical frequency comb generation, ultrafast optical pulse generation and measurement using these materials, and their potential future impact and challenges are covered.

New CMOS-compatible platforms based on silicon nitride and hydex for nonlinear optics

Today cross-cutting approaches, where molecular engineering and clever processing are synergistically coupled, allow the chemist to tailor complex hybrid systems of various shapes with perfect mastery at different size scales, composition, functionality, and morphology. Hybrid materials with organic–inorganic or bio–inorganic character represent not only a new field of basic research but also, via their remarkable new properties and multifunctional nature, hybrids offer prospects for many new applications in extremely diverse fields. The description and discussion of the major applications of hybrid inorganic–organic (or biologic) materials are the major topic of this critical review. Indeed, today the very large set of accessible hybrid materials span a wide spectrum of properties which yield the emergence of innovative industrial applications in various domains such as optics, micro-electronics, transportation, health, energy, housing, and the environment among others (526 references).

Applications of advanced hybrid organic–inorganic nanomaterials: from laboratory to market

The nonlinearities in silicon are diverse. This Review covers the wealth of nonlinear effects in silicon and highlights the important applications and technological solutions in nonlinear silicon photonics. The increasing capability for manufacturing a wide variety of optoelectronic devices from polymer and polymer–silicon hybrids, including transmission fibre, modulators, detectors and light sources, suggests that organic photonics has a promising future in communications and other applications.

Nonlinear silicon photonics

We experimentally investigate the simultaneous all-optical signal processing of two 40-Gb/s wavelength-division-multiplexing optical streams spaced by 5 nm using self-phase modulation and offset filtering in a single highly nonlinear fiber to achieve a 2R optical regeneration. Using a bidirectional configuration, we demonstrate efficient mitigation of the interchannel crosstalk. We experimentally observe no degradation of the regenerator performance arising from the presence of the second channel as compared to the single-channel case.

Investigation of Simultaneous 2R Regeneration of Two 40-Gb/s Channels in a Single Optical Fiber

This paper introduces a spectral slicing technique that extends the useful spectral range of frequency combs generated through self-phase modulation (SPM) of mode-locked laser pulses. When generating frequency combs by SPM, the spectral range with high-quality carriers is usually limited due to spectral minima carrying too little power. To overcome these limitations, we combine suitable slices of broadened and nonbroadened spectra. The concept was experimentally verified: A total number of 325 consecutive equidistant subcarriers span a bandwidth of 4 THz. All subcarriers have an optical carrier-power-to-noise-power-density ratio (OCNR) larger than 25.8 dB (0.1 nm) and were derived from one mode-locked laser with a mode linewidth of approximately 1 kHz. The signal quality of the comb and in particular of each subcarrier was ultimately tested in a terabit-per-second communication experiment. The comb quality allowed us to transmit 32.5 Tb/s over 225 km with 100 Gb/s dual polarization 16-ary quadrature amplitude modulation (16QAM) signals on each of the subcarriers.

High-Quality Optical Frequency Comb by Spectral Slicing of Spectra Broadened by SPM

We demonstrate a four-channel extension to the Mamyshev regenerator and investigate its potential for the simultaneous processing of 4 times 10 Gb/s return-to-zero wavelength division-multiplexed channels. Mitigation of the interchannel nonlinearities is achieved through the rapid walkoff induced by both the large differential group delay of a specially developed polarization maintaining highly nonlinear fiber and a bidirectional architecture. Numerical and experimental results demonstrate the reduction of interchannel crosstalk as well as the potential of the scheme for 2R regeneration.

/pdf/investigation-of-four-wavelength-regenerator-using-rn85htr23z.pdf

Investigation of Four-Wavelength Regenerator Using Polarization- and Direction-Multiplexing

A stable optical beat-signal with frequency >; 160 GHz is produced by injection-locking two narrow-linewidth semiconductor lasers emitting at frequencies spaced by the beat-frequency to a low-jitter 10-GHz optical comb. The generated beat-signal with broadband noise suppression of >; 75 dB is temporally compressed by factors of up to four in a high stimulated Brillouin scattering threshold aluminosilicate highly nonlinear fiber. The generated subpicosecond pulses have a root mean square (rms) timing jitter below 150 fs measured over 1 s.

Stable and Efficient Generation of High Repetition Rate ( $>$ 160 GHz) Subpicosecond Optical Pulses

A distributed acoustic sensor (DAS) based on two-mode fiber is demonstrated By using φ-OTDR, the backscattered light from higher order mode can be used to quantify vibrations By combining the result obtained from different mode, 252dB improvement in noise floor is achieved The results confirm that few-mode fiber can be used for DAS applications

Francesca Parmigiani

Papers

Investigation of Simultaneous 2R Regeneration of Two 40-Gb/s Channels in a Single Optical Fiber

High-Quality Optical Frequency Comb by Spectral Slicing of Spectra Broadened by SPM

Investigation of Four-Wavelength Regenerator Using Polarization- and Direction-Multiplexing

Stable and Efficient Generation of High Repetition Rate ( $>$ 160 GHz) Subpicosecond Optical Pulses

Distributed Acoustic Sensor Based on a Two-Mode Fiber