Toshiaki Kuri

Fiber-optic millimeter-wave downlink system using 60 GHz-band external modulation

In this paper, a fiber-optic millimeter-wave (mm-wave) downlink system using 60 GHz-band external modulation is investigated. We prepare the fiber-optic 60 GHz-band mm-wave downlink testbed. It consists of an optical modulation section with a mm-wave signal generator, an optical single sideband (SSB) filter, a standard single-mode fiber (SMF), an optical detection section with a 60 GHz-band radio transmitter and a 60 GHz-band radio receiver. To modulate the laser output with 60 GHz-band mm-wave signals directly, a specially designed electro-absorption modulator with high-efficiency at around 60 GHz is used. The use of this modulator makes the simpler system configuration possible. Using the downlink testbed, the 5 m-long free-space propagation of subcarrier multiplexed 156 Mb/s-DPSK 60 GHz-band mm-wave signals recovered by optical direct detection is successfully demonstrated. The transmission of the mm-wave signals over 85 km-long standard SMF is also successfully demonstrated, using an optical SSB filtering technique to overcome the fiber dispersion. The BER of 10/sup -9/ is achievable at the optical received power of -7.0 dBm.

Simultaneous three-band modulation and fiber-optic transmission of 2.5-Gb/s baseband, microwave-, and 60-GHz-band signals on a single wavelength

Simultaneous modulation of 2.5-Gb/s baseband, microwave-band, and 59.6-GHz 155.52-Mb/s differential phase-shift keying signals on a single wavelength, using a single 60-GHz-band electroabsorption modulator (EAM), and fiber-optic transmission over a 40-km-long dispersion-shifted fiber (DSF) was experimentally demonstrated. The optimum operating conditions for three-band modulation and transmission were theoretically investigated. Degradation due to the nonlinearity of the EAM for the millimeter-wave signal is discussed theoretically. The fading problem due to the fiber dispersion of the standard single-mode fiber and the DSF was also investigated.

Wavelength-division-multiplexed Millimeter-waveband radio-on-fiber system using a supercontinuum light source

We propose to use a supercontinuum (SC) for a low-phase-noise multiwavelength light source in wavelength-division-multiplexing (WDM) millimeter-waveband (mm-waveband) radio-on-fiber (RoF) systems. We demonstrate the generation of low-phase-noise 60-GHz-band RoF signal. We also demonstrate the generation of two-channel WDM 60-GHz-band RoF signals and the transmission of the signals over a 25-km standard single-mode fiber (SMF) using photonic upconversion. The single multiwavelength light source can be shared with a number of users and simplifies the system configuration, which would allow the realization of high-reliability as well as low-cost RoF systems. Finally, the RoF network capacity with a single SC light source is estimated to be over 10 000 channels when the spectrum of the SC light source is fully utilized.

Dynamic Reconfigurable WDM 60-GHz Millimeter-Waveband Radio-Over-Fiber Access Network: Architectural Considerations and Experiment

We will propose a dynamic reconfigurable wavelength-division-multiplexed (WDM) millimeter-waveband (mm-waveband) radio-over-fiber (RoF) access network and demonstrate, for the first time, a dynamic-channel-allocation capability of millimeter-waveband optical RoF signals in WDM access network using a supercontinuum light source, arrayed-waveguide gratings, and a reconfigurable optical-crossconnect switch. The dynamic reconfigurable RoF network architecture is presented, and its features are described. Then, four 155-Mb/s RoF channels are effectively generated, transmitted through 25 km of fiber, switched, transmitted again through 2 km of fiber, and detected with an error-free operation (bit error rate < 10-10). The proposed RoF architecture is highly scalable, both in terms of channel and access-point counts.

Demultiplexing using an arrayed-waveguide grating for frequency-interleaved DWDM millimeter-wave radio-on-fiber systems

The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme.

An approach to single optical component antenna base stations for broad-band millimeter-wave fiber-radio access systems

To realize a cost-effective and practical antenna base station (BS) for 60-GHz-band millimeter-wave fiber-radio access systems, an approach to a single optical component BS is presented in this paper. The external modulation technique will allow to replace the pair of a photodetector (PD) and a laser diode with an external modulator at the BS by an optical transceiver. Two system architectures using different types of optical transceivers are studied in detail: one employs an electroabsorption transceiver (EAT), and the other employs an electroabsorption transceiver/mixer (EATX). The EAT serves simultaneously as a PD and an external light modulator in 60-GHz-band millimeter-wave region. The EATX furthermore acts as an IF-to-RF upconverter and an RF-to-IF downconverter. It is shown that both system architectures have good prospects to realize cost-effective fiber-radio access systems.

Optical Transmitter and Receiver of 24-GHz Ultra-Wideband Signal by Direct Photonic Conversion Techniques

To overcome the scarcity of available radio frequency (RF) resource, ultra-wideband (UWB) attracts its attention as one of next generation high-speed radio communication technologies because UWB systems can share the RF band with existing conventional narrowband radio systems. If such UWB signal can be delivered through optical networks without distance limitation, various standalone UWB applications can be networked widely and become available anywhere on demand. In this paper, novel optical transmitter and receiver of millimeter-wave UWB signal are proposed with direct photonic conversion techniques. We experimentally demonstrate the optical detection and regeneration, after 3-m-long transmitted in the air, of the optically generated 24 GHz UWB with the bandwidth of 46 Hz at the data rate of 250 Mb/s

Characterizations of supercontinuum light source for WDM millimeter-wave-band radio-on-fiber systems

We qualitatively evaluate for the first time phase-noise characteristics of radio-frequency carriers of a supercontinuum generator and prove to be promising as the multiwavelength light source for wavelength-division-multiplexed millimeter-wave-band radio-on-fiber systems.

Optical heterodyne detection technique for densely multiplexed millimeter-wave-band radio-on-fiber systems

Even in millimeter-wave-band (mm-wave-band) radio-on-fiber (ROF) systems, wavelength-division multiplexing (WDM) combined with subcarrier multiplexing (SCM) is a practical and attractive way to increase the channel capacity in existing optical-frequency-interleaved fibers. In this paper, we propose a channel selection scheme for interleaved dense WDM/SCM mm-wave-band ROF signals that use optical heterodyne detection with dual-mode local light. The principle underlying this scheme is explained theoretically, and channel selection of the DWDM/SCM ROF signal after transmission over a 25-km-long standard single-mode optical fiber has been experimentally demonstrated.

60-GHz-band full-duplex radio-on-fiber system using two-RF-port electroabsorption transceiver

A full-duplex radio-on-fiber system using a newly developed 60-GHz-band optical transceiver is investigated. We fabricated a 60-GHz-band two-radio-frequency (RF)-port electroabsorption transceiver (EAT) module, which is the first developed 60-GHz-band optical transceiver in the world. The EAT module has individual RF input and output ports, each with impedance-matching circuits that enhance modulation and detection efficiencies near 60 GHz. A radio-on-fiber testbed adopting the EAT has an advantage that a base station becomes the simplest configuration, which basically consists of only the 60-GHz-band EAT. Using the radio-on-fiber testbed, the simultaneous transmission of 59.6-GHz (downlink) and 60.0-GHz (uplink) signals with data of 156 Mb/s is experimentally demonstrated.