Yoshihiro Yasumura

Optical and millimeter-wave radio seamless MIMO transmission based on a radio over fiber technology

Multi-input multi-output (MIMO) transmission of two millimeter-wave radio signals seamlessly converted from polarization-division-multiplexed quadrature-phase-shift-keying optical signals is successfully demonstrated, where a radio access unit basically consisting of only optical-to-electrical converters and a radio receiver performs total signal equalization of both the optical and the radio paths and demodulation with digital signal processing (DSP). Orthogonally polarized optical components that are directly converted to two-channel radio components can be demultiplexed and demodulated with high-speed DSP as in optical digital coherent detection. 20-Gbaud optical and radio seamless MIMO transmission provides a total capacity of 74.4 Gb/s with a forward error correction overhead of 7%.

Coherent Radio-Over-Fiber and Millimeter-Wave Radio Seamless Transmission System for Resilient Access Networks

We propose a millimeter-wave (MMW) coherent radio-over-fiber (RoF) transmission system for application to an access network with a direct broadband last-mile wireless connection to an optical fiber network. The coherent RoF system comprises an optical two-tone RoF signal generator with an advanced modulation format for high-throughput transmission and employs a digital-signal-processing-aided coherent detection technique for MMW radio, which is a technique similar to that of optical digital coherent detection. As proof of concept, a 20-GBd quadrature phase-shift keying RoF transmission over 20 km of optical fiber before a radio transmission over 20 m of air is demonstrated. The results of the radio transmissions using Cassegrain-type antenna pairs with a gain of 50 dBi are consistent with theoretical estimations; this suggests the possibility of developing a midrange transmission system using a high-power MMW amplifier.

16-Gbaud QPSK radio transmission using optical frequency comb with recirculating frequency shifter for 300-GHz RoF signal

We demonstrate 300-GHz-band radio transmission with a digital coherent detection technique. Quadrature-phaseshift-keying modulation can provide a data rate of 29.9 Gb/s, with 7% forward error correction overhead. A frequency-locked optical frequency comb for a 300-GHz radio-over-fiber signal can be generated by a recirculating frequency shifter with a single sideband suppressed-carrier modulator in an amplified optical fiber loop.

100-GHz and 300-GHz coherent radio-over-fiber transmission using optical frequency comb source

Millimeter-wave and sub-millimeter-wave radio-over-fiber (RoF) technology with digital-signal-processing aided coherent detection can be a promising candidate for high-speed radio transmission links with a capacity of greater than 10 Gb/s if the energy consumption does not increase drastically. We demonstrate 100-GHz and 300-GHz-band simultaneous RoF signal generation using an optical frequency comb source comprising an optical frequency shifter in an amplified optical fiber loop, and its radio transmission over the air. 10-Gbaud quadrature-phase-shift-keying provides a capacity of 18.6 Gb /s with a 7% forward error correction overhead in single carrier signal transmission as well as in multi-carrier transmission.

20-Gbaud QPSK optical and radio transmission using high-gain antennas for resilient access networks

20-Gbaud QPSK transmission over 20-km SMF for optical and 7.5-m free space for 90-GHz radio is successfully demonstrated with 50-dBi Cassegrain antennas. This configuration will be feasible for kilometer-order distance transmission.

20-Gbaud QPSK RoF and millimeter-wave radio transmission

We successfully demonstrate 20-Gbaud (37.38 Gb/s) QPSK RoF and 100-GHz radio transmission over 20-km SMF and 0.3-m air. ADC with a bandwidth of 30 GHz can demodulate 40-GHz-bandwidth signal using digital coherent detection technique.

Fractionally-spaced frequency domain equalization for optical coherent receivers with interleaved samplers

We propose a fractionally-spaced frequency domain equalization technique for optical coherent receivers with interleaved samplers and experimentally demonstrate its robustness against the sampling timing mismatch and the IQ channel skew in 20Gbps coherent QPSK transmissions.

Digital-signal-processing-aided ultra-high-speed radio-over-fiber technology for highly resilient mobile backhaul

This paper describes a scenario of highly resilient mobile backhaul using the radio-over-fiber (RoF) technology. RoF-based millimeter-wave high-speed transmission is useful for quick recovery from severe physical damage of the network infrastructure. As a possible approach, we demonstrated polarization division multiplexing optical and 2×2 multi-input multi-output radio seamless hybrid downlink transmission over 20-km-long standard single mode fiber and 0.9-m free space with a digital signal processing technique for the 10-Gbaud QPSK format.