Tetsuya Kawanishi

High-speed control of lightwave using electrooptic (EO) effect is investigated in this paper. Agile optical frequency shift can be achieved by optical single-sideband (SSB) and frequency-shift-keying (FSK) modulators, where high-speed optical phase-shift-keying (PSK) signals can also be generated by using FSK/SSB modulators. We also describe ultrahigh extinction ratio optical intensity modulation (IM) technique for two-tone lightwave signals with high spurious suppression, which is useful for ph

Terahertz (THz) wave can offer over 100-Gb/s wireless transmission by the use of wide spectrum. Due to features of high-frequency waves such as lightwaves, THz can have high directivity. To mitigate congestion of radio spectrum, advanced modulation formats will play significant roles in THz bands as well as in conventional millimeter-wave or microwave bands. This paper will provide overviews on spectral efficiency and transmission capacity of THz wave systems. Power consumption of radio links wo

This paper describes optical frequency comb generation using optical single-sideband modulation technique. We can obtain optical frequency shift using the singnal-sideband modulator consisting of four optical phase modulators, where the frequency shift is precisely equal to that of an rf-signal fed to the modulator. A series of optical spectral components can be generated by using an optical fiber loop having an optical single-sideband modulator.

We described a novel optical label swapping (OLS) technique for optical packet systems using frequency-shift-keying (FSK) optical labeling. High-speed optical FSK signal can be generated by using an external FSK modulator consisting of four optical phase modulators. The FSK modulator was based on optical single-sideband (SSB) modulation technique, and comprised of traveling-wave electrodes for high-speed frequency switching. We demonstrate 10 Gbps FSK transmission, and simultaneous modulation by

A technique for suppressing of undesired optical harmonics in wavelength conversion using an optical single-sideband modulator is proposed. The third-order optical harmonic due to nonlinearity of the modulator, which determines the conventional theoretical limit of the signal-to-noise ratio, can be diminished through simultaneous feeding of the fundamental and the third-order harmonic radio-frequency signals.

We investigated an integrated optical modulator consisting of two Mach-Zehnder interferometers. The modulator can generate optical signals in various types of modulation formats, which have advantages for long-haul transmission, optical labeling, etc. By using a fabricated versatile optical modulator having traveling-wave electrodes designed for high-speed signals, we demonstrated generation of optical 40Gb/s frequency-shift-keying signals, which can be demodulated by an optical filter. 80Gb/s o

As fifth-generation (5G) technology is expected to offer super-broadband mobile services with new features such as low latency for critical applications and low-power operation for Internet of Things (IoT) applications, it will use wireless interfaces for small or spot cells with a new RF resource, the high band (frequencies above 6 GHz), in addition to the low band (below 6 GHz) on macro and small cells coexisting with conventional mobile technologies [1]-[4]. Another feature of 5G wireless int

A novel free-space coupling system combined with a multi-core fiber enables up-scaling to a record space-division-multiplexed (SDM) channel number of 19. We achieve 305-Tb/s transmission over 10.1 km using 19-SDM, 100-WDM PDM-QPSK signals.

An optical frequency-shift-keying (FSK) modulator with a pair of Mach-Zehnder structures that can switch optical frequency is developed. The operation is demonstrated at a 10 Gbit/s FSK transmission conducted on a standard singlemode fibre of 60 km, where the FSK signal is demodulated by a fibre Bragg grating.