There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Jasmonates: biosynthesis, perception, signal transduction and action in plant stress response, growth and development. An update to the 2007 review in Annals of Botany

This Review covers the state-of-the-art technologies on photonics-based terahertz communications, which are compared with competing technologies based on electronics and free-space optical communications. Future prospects and challenges are also discussed. Almost 15 years have passed since the initial demonstrations of terahertz (THz) wireless communications were made using both pulsed and continuous waves. THz technologies are attracting great interest and are expected to meet the ever-increasing demand for high-capacity wireless communications. Here, we review the latest trends in THz communications research, focusing on how photonics technologies have played a key role in the development of first-age THz communication systems. We also provide a comparison with other competitive technologies, such as THz transceivers enabled by electronic devices as well as free-space lightwave communications.

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Advances in terahertz communications accelerated by photonics

Wave propagation and group velocity

A wireless communication system with a maximum data rate of 100 Gbit s−1 over 20 m is demonstrated using a carrier frequency of 237.5 GHz. The photonic schemes used to generate the signal carrier and local oscillator are described, as is the fast photodetector used as a mixer for data extraction.

Wireless sub-THz communication system with high data rate

This paper proposes a novel bandwidth-elastic and energy-efficient passive optical network (PON) based on the coherent interleaved frequency division multiple access (IFDMA) scheme. We experimentally demonstrate the coherent IFDMA-PON uplink transmission up-to 30 Gbps over a 30 km standard single-mode fiber with 2 × optical network units (ONUs). A low-complexity digital carrier synchronization technique enables multiple access of the ONUs on the basis of 78.1 MHz narrow band orthogonal subcarriers without any guard-bands.

An energy-efficient and elastic optical multiple access system based on coherent interleaved frequency division multiple access.

Spatial multiplexing gain degradation due to millimeter-order antenna misalignments in W-band MIMO-RoF systems is investigated in 40-Gbps-class 2 × 2 MIMO-OFDM RoF transmissions. The advantage of space-time block coding there is also demonstrated.

On the MIMO channel rank deficiency in W-band MIMO RoF transmissions

A novel fixed-length elastic-capacity optical OFDM payload packet which can significantly ease the buffer scheduling is proposed. 1 × 2 switching and fiber delay line buffering of 19-30Gbps coherent OFDM payload packets is experimentally demonstrated.

Fixed-length elastic-capacity OFDM payload packet: Concept and demonstration

A simple and spatially-flexible coherent receiver without local lights, optical hybrids, or spatial de-multiplexers is experimentally demonstrated; 2×10-Gbaud SDM QPSK signals were detected only by 2-D arrayed photodetectors based on a novel phase-retrieving technique.

Coherent Detection Only by 2-D Photodetector Array: A Discreteness-Aware Phase Retrieval Approach

A low-complexity frequency-dependent IQ imbalance monitoring technique for a dual-polarization (DP) IQ modulator by using a single photodetector is proposed based on phase retrieval and demonstrated experimentally with a 63.25-Gbaud DP-16QAM signal.

Simultaneous Monitoring of Frequency-dependent IQ Imbalances in a Dual-polarization IQ Modulator by using a Single Photodetector: A Phase Retrieval Approach

Yuki Yoshida

Papers

An energy-efficient and elastic optical multiple access system based on coherent interleaved frequency division multiple access.

On the MIMO channel rank deficiency in W-band MIMO RoF transmissions

Fixed-length elastic-capacity OFDM payload packet: Concept and demonstration

Coherent Detection Only by 2-D Photodetector Array: A Discreteness-Aware Phase Retrieval Approach

Simultaneous Monitoring of Frequency-dependent IQ Imbalances in a Dual-polarization IQ Modulator by using a Single Photodetector: A Phase Retrieval Approach