The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

Electronics based on two-dimensional materials

We review the current status of single-photon-source and single-photon-detector technologies operating at wavelengths from the ultraviolet to the infrared. We discuss applications of these technologies to quantum communication, a field currently driving much of the development of single-photon sources and detectors.

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Invited review article: Single-photon sources and detectors

The current status of lithium-niobate external-modulator technology is reviewed with emphasis on design, fabrication, system requirements, performance, and reliability. The technology meets the performance and reliability requirements of current 2.5-, 10-, and 40-Gb/s digital communication systems, as well as CATV analog systems. The current trend in device topology is toward higher data rates and increased levels of integration. In particular, multiple high-speed modulation functions, such as 10-Gb/s return-to-zero pulse generation plus data modulation, have been achieved in a single device.

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A review of lithium niobate modulators for fiber-optic communications systems

Digital filters underpin the performance of coherent optical receivers which exploit digital signal processing (DSP) to mitigate transmission impairments. We outline the principles of such receivers and review our experimental investigations into compensation of polarization mode dispersion. We then consider the details of the digital filtering employed and present an analytical solution to the design of a chromatic dispersion compensating filter. Using the analytical solution an upper bound on the number of taps required to compensate chromatic dispersion is obtained, with simulation revealing an improved bound of 2.2 taps per 1000ps/nm for 10.7GBaud data. Finally the principles of digital polarization tracking are outlined and through simulation, it is demonstrated that 100krad/s polarization rotations could be tracked using DSP with a clock frequency of less than 500MHz.

Digital filters for coherent optical receivers.

Optical fiber transmission is impacted by linear and nonlinear impairments. We study the use of digital backpropagation (BP) in conjunction with coherent detection to jointly mitigate dispersion and fiber nonlinearity. We propose a noniterative asymmetric split-step Fourier method (SSFM) for solving the inverse nonlinear Schrodinger equation (NLSE). Using simulation results for RZ-QPSK transmitted over terrestrial systems with inline amplification and dispersion compensation, we obtain heuristics for the step size and sampling rate requirements, as well as the optimal dispersion map.

Compensation of Dispersion and Nonlinear Impairments Using Digital Backpropagation

We propose a novel method of the supercontinuum (SC) generation, in which the extremely flat SC spectrum can be obtained by the Kerr nonlinearity in a distributed optical fiber amplifier. We successfully demonstrate the SC generation over 34 nm using a 1-km-long Erbium-doped fiber.

Novel method of extremely flat supercontinuum generation using distributed optical gain in long Erbium-doped fiber amplifier

Using a PLC-based 16-tap optical FIR filter, we demonstrate tunable optical equalization for 40-Gbps intensity-modulated signals. Such equalizer compensates for both intensity distortion due to tight filtering and phase distortion due to±100-ps/nm chromatic dispersion, giving significant receiver-sensitivity improvement.

Tunable optical equalizer for 40-Gbps intensity-modulated signal using PLC-based finite-impulse-response filter

We explore the ultimate potential offered by state-of-the-art Bismuth oxide-based optical fiber technology in a high-speed optical phase-locked loop-based clock recovery subsystem for an optical time-division multiplexed (OTDM) signal, in which the use of optical fiber-based devices has been considered to be inappropriate due to its tight requirement of short optical loop length. Here, we experimentally demonstrate the implementation of a compact all-fiber-based OTDM receiver incorporating both clock recovery and demultiplexing functions by use of short lengths of Bismuth oxide-based nonlinear fiber and erbium-doped Bismuth oxide fiber. Successful clock recovery and subsequent error-free demultiplexing are readily achieved at a data rate of 80 Gb/s. The clock recovery subsystem is also shown to be operable at 160 Gb/s.

Clock Recovery and Demultiplexing of High-Speed OTDM Signal Through Combined Use of Bismuth Oxide Nonlinear Fiber and Erbium-Doped

Coherent optical communications were studied extensively in the 1980s because of the high receiver sensitivity that could enhance the unrepeated transmission distance; however, since 1990, related R&D had been interrupted by the rapid advances in wavelength-division multiplexed (WDM) systems and erbium-doped fiber amplifiers (EDFAs).

Coherent optical communication technology

PROBLEM TO BE SOLVED: To solve such problem in the conventional case that an element with satisfactory compensation characteristic has not been obtained inexpensively in spite of the proposal of various methods and elements for compensating dispersion for eliminating difficulty in communications resulting from the occurrence of wavelength dispersion in a signal transmitted through an optical fiber in optical communications in which a communication bit rate is >=10 Gbps, especially >=40 Gbps. SOLUTION: When producing elements capable of performing dispersion compensation through the use of group velocity delay time-wavelength characteristic and connecting a plurality of the elements in series, the element for performing dispersion compensation and a collimetor part are mounted on separate holding members and both of the holding members are mounted to a case attachably and detachably and opposedly to each other, thereby the optical dispersion compensation element which is large in band width and large in the extreme value of the group velocity delay time is prepared at a low cost.

Kazuro Kikuchi

Papers

Novel method of extremely flat supercontinuum generation using distributed optical gain in long Erbium-doped fiber amplifier

Tunable optical equalizer for 40-Gbps intensity-modulated signal using PLC-based finite-impulse-response filter

Clock Recovery and Demultiplexing of High-Speed OTDM Signal Through Combined Use of Bismuth Oxide Nonlinear Fiber and Erbium-Doped

Coherent optical communication technology

Element and method for compensating dispersion of light