Author
H. Takahashi
Bio: H. Takahashi is an academic researcher from Nippon Telegraph and Telephone. The author has contributed to research in topics: Optical switch & Waveguide (optics). The author has an hindex of 25, co-authored 98 publications receiving 1889 citations.
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors investigated the maximum output power of these devices and compared the phase noise of MMW signals generated by high-speed uni-traveling carrier photodiodes (UTC-PD) and InP high-electron mobility transistor (HEMT) millimeter-wave (MMW) monolithic integrated circuits (MMICs).
Abstract: Our progress in 120-GHz-band wireless link technologies enables us to transmit 10-Gbit/s data transmission over a distance of more than 1 km The 120-GHz-band wireless link uses high-speed uni-traveling carrier photodiodes (UTC-PD) and InP high-electron mobility transistor (HEMT) millimeter-wave (MMW) monolithic integrated circuits (MMICs) for the generation of MMW signals We investigate the maximum output power of these devices and compare the phase noise of MMW signals generated by UTC-PDs and InP HEMT MMICs We describe the antennas we used and their operation technologies Finally, we investigate the dependence of transmission distance on availability using the statistical rain attenuation data The calculation results show that the 120-GHz-band wireless link can transmit 10-Gbit/s data over a distance of 1 km with availability of 99999%
136 citations
TL;DR: In this article, a 120-GHz-band mm-wave monolithic integrated circuits (MMICs) were fabricated using 0.1-mum-gate InP-HEMTs and coplanar waveguides.
Abstract: We have developed a 120-GHz-band wireless link whose maximum transmission data rate is 11.1 Gbit/s. The wireless link uses millimeter-wave monolithic integrated circuits (MMICs) for the generation of a 120-GHz-band millimeter-wave wireless signal. The MMICs were fabricated using 0.1-mum-gate InP-HEMTs and coplanar waveguides. The wireless link can handle four kinds of data rate for OC-192 and 10-Gbit Ethernet standards with and without forward error correction (FEC). We succeeded in the error-free transmission of a 10-Gbit/s signal over a distance of 800 m. The introduction of FEC into the 120-GHz-band wireless link decreased the minimum received power for error-free transmission, and improved the reliability of the link.
129 citations
TL;DR: The wavefront matching (WFM) method is expanded to create optimum waveguide shapes with low-loss and low-wavelength dependence in waveguide lenses, Y-branches, and waveguide crossings.
Abstract: We have studied the wavefront matching (WFM) method, which synthesizes optimum waveguide patterns from the desired characteristics, and demonstrated its feasibility. In this paper, we expand this method to create optimum waveguide shapes with low-loss and low-wavelength dependence in waveguide lenses, Y-branches, and waveguide crossings. We describe the design procedures for each waveguide element and report the experimental results as proof of concept. The measured results agree well with our design requirements, and the waveguide patterns designed by the WFM method exhibit better characteristics than the reference patterns.
90 citations
21 Feb 1999
TL;DR: In this article, a low loss groove design for athermal silica-based arrayed-waveguide grating multiplexers was proposed and the insertion loss was 3 dB and the cross talk was -35 dB.
Abstract: We propose a new low loss groove design for athermal silica-based arrayed-waveguide grating multiplexers. The insertion loss was 3 dB and the cross talk was -35 dB. The temperature dependence of the channel wavelength change was suppressed to below 0.4 nm in the 0-85/spl deg/C temperature range.
88 citations
TL;DR: In this paper, the transmission characteristics of a 120 GHz-band millimeter-wave wireless link are described and the effects of transmitting 120GHz-band optical subcarrier signals through single-mode fibers were theoretically and experimentally investigated.
Abstract: The transmission characteristics of a 120-GHz-band millimeter-wave wireless link are described. The wireless link uses photonic technologies for generation, modulation, and transmission of millimeter-wave signals. This configuration enables set up of the photonic millimeter-wave generator and transmitter core separately; therefore, the wireless link can be used as a kind of radio-over-fiber system. The effects of transmitting 120-GHz-band optical subcarrier signals through single-mode fibers were theoretically and experimentally investigated. It was confirmed that the time shift of the code edges, because of chromatic dispersion, limits the transmission distance. A data stream at 10-Gbit/s was successfully transmitted over the 120-GHz-band millimeter-wave wireless link, with a bit error rate (BER) below 10-12 over a distance of 250 m. The results also demonstrated the stability of the wireless link, which satisfied the 10-Gb Ethernet standard under clear weather conditions.
87 citations
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TL;DR: Fiber Bragg grating (FBG) technology has been extensively studied in the literature as mentioned in this paper, where the basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described.
Abstract: The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described.
2,905 citations
TL;DR: In this paper, the state-of-the-art technologies on photonics-based terahertz communications are compared with competing technologies based on electronics and free-space optical communications.
Abstract: 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.
1,238 citations
TL;DR: The current progress of terahertz-wave technologies related to communications applications are examined and some issues that need to be considered for the future of THz communications are discussed.
Abstract: Recent changes in how people consume multimedia services are causing an explosive increase in mobile traffic. With more and more people using wireless networks, the demand for the ultra-fast wireless communications systems is increasing. To date, this demand has been accommodated with advanced modulation schemes and signal-processing technologies at microwave frequencies. However, without increasing the carrier frequencies for more spectral resources, it may be quite difficult to keep up with the needs of users. Although there are several alternative bands, recent advances in terahertz-wave (THz-wave) technologies have attracted attention due to the huge bandwidth of THz waves and its potential for use in wireless communications. The frequency band of 275 ~ 3000 GHz , which has not been allocated for specific uses yet, is especially of interest for future wireless systems with data rates of 10 Gb/s or higher. Although THz communications is still in a very early stage of development, there have been lots of reports that show its potential. In this review, we will examine the current progress of THz-wave technologies related to communications applications and discuss some issues that need to be considered for the future of THz communications.
1,072 citations
TL;DR: A wireless sub-THz communication system near 237.5 GHz with one to three carriers and up to 100 Gbit/s with state-of-the-art active I/Q-MMIC at the Rx is demonstrated.
Abstract: 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.
1,037 citations
TL;DR: The goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications and report on the reported advantages and challenges of using sub-terahertz andTHz waves as a means to transmit data wirelessly.
Abstract: According to Edholm’s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years It can be predicted that data rates of around 5–10 Gb/s will be required in ten years In order to achieve 10 Gb/s data rates, the carrier frequencies need to be increased beyond 100 GHz Over the past ten years, several groups have considered the prospects of using sub-terahertz (THz) and THz waves (100–2000 GHz) as a means to transmit data wirelessly Some of the reported advantages of THz communications links are inherently higher bandwidth compared to millimeter wave links, less susceptibility to scintillation effects than infrared wireless links, and the ability to use THz links for secure communications Our goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications
991 citations