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Terahertz-wave signal transmission is demonstrated using quadrature amplitude modulation (QAM) by photonics. Small frequency fluctuations using a frequency-locked optical frequency comb are capable of generating a 80-MHz-bandwidth 16-ary-QAM signal with a data rate of 195 Mb/s.
Wavelength characteristics of the extinction ratio of optical Mach-Zehnder modulator using an active Y-branch is evaluated over C-band wavelengths. The observed extinction ratios are achieved greater than 60 dB at all of the wavelengths by optimization of applying voltage to the Y-branch by each wavelength.
A new millimeter-wave (MMW) signal generation device using a rectangular waveguide and second order nonlinear optical effect is proposed. Using a T-shaped rectangular waveguide with a suspended LiTaO3 crystal, adiabatic MMW signal injection into the waveguide is obtainable through optical difference frequency generation in the crystal. This device is easy for coupling to standard rectangular waveguide...
A wavelength-division-multiplexed (WDM) radio-over-fiber (RoF) de-multiplexer, which is specially designed for frequency-modulated continuous-wave (FM-CW) signal delivery systems, is newly developed. The characteristics of the developed de-multiplexer are described and then the de-multiplexing performances of 4-channel WDM 32-GHz-band and 8-channel WDM 48-GHz-band FM-CW RoF signals are evaluated with...
An optical frequency comb source provides a terahertz-frequency-capable optical two-tone signal with an enhancement of the optical signal-to-noise ratio using an injection-locking technique. No phase-noise degradation between the signal with and without injection locking has been observed.
We demonstrated frequency-quadruple optical two-tone signal generation using integrated modulator driven by one-port RF signal input without optical filters. As a result, we generated the two-tone signal and the spurious suppression ratio was 27 dB.
We propose a frequency-octupling technique for millimeter-wave and terahertz signal generation using cascaded optical frequency multipliers based on optical modulation. A millimeter-wave-capable optical frequency doubler connected to an optical frequency quadrupler provides a 100–200-GHz signal whose number of multiplications is eight. The observed phase-noise degradation is followed by theoretically...
We propose and experimentally investigate a high-speed burst-mode LTE-A signal transmission on a seamlessly converged RoF and millimeter-wave system at 90 GHz. Satisfactory transmission performance over the converged RoF and a 1.2-m 90-GHz wireless link is achieved. The obtained results confirm the potential to use the system in future high-speed mobile and broadband access networks.
We report high-gain optical-to-electrical and electrical-to-optical converters for application to an analog radio-over-fiber link for an uplink signal transport on a mobile fronthaul. A 50-dB gain link with a relatively low noise figure provides an RF sensitivity of less than −90 dBm.
3.0-Gb/s signal transmission over a fiber-wireless hybrid link at the 22.5-GHz-band is demonstrated. A frequency-stabilized radio-over-fiber signal is generated using an optical phase-locked-loop driven by a synthesizer using a direct photonic up-conversion technique.
In this study, a high-capacity and low-latency fiber-wireless signal transport technology in the terahertz band is discussed. An advanced optical fiber communication technology is easily adopted for high-capacity terahertz signal transmission, as well as for encapsulation of existing radio services into the terahertz carrier.
We proposed a seamless fiber-millimeter-wave converged system suitable to provide a high-speed and low-latency transmission for heterogeneous wireless signals. Satisfactory performance is experimentally confirmed for simultaneous transmission of high-speed LTE-A and very-high-throughput WLAN IEEE 802.11ac signals over the proposed system.
Autoimmune pancreatitis (AIP) must be differentiated from pancreatic carcinoma, and immunoglobulin (Ig)G4‐related sclerosing cholangitis (SC) from cholangiocarcinoma and primary sclerosing cholangitis (PSC). Pancreatographic findings such as a long narrowing of the main pancreatic duct, lack of upstream dilatation, skipped narrowed lesions, and side branches arising from the narrowed portion suggest...
The two-mode lasing is obtained at the telecom-band using an InAs quantum dot gain chip. The wavelengths of the two modes were 1539.73 and 1540.44 nm corresponded to the frequency separation of 89.8 GHz which generated millimeter wave signal.
We propose and experimentally demonstrate optical data exchange scheme between 16QAM and QPSK with narrow spacing of 50GHz. The use of coherent pump makes it free of phase noise from pumps, and enables the use of low-cost DFB as pump source.
We demonstrate 12-Gbaud QPSK signal transmission in a fiber-wireless link and compare a modulator-based optical two-tone generator and an optical heterodyning with free-running lasers. The obtained frequency fluctuation of the two-tone system meets the requirements of the radio regulations.
We propose an extinction-ratio and chirp tunable modulator in single-drive operation. Using the modulator, we demonstrated precise amplitude modulation without parasitic phase modulation. Extinction-ratio was larger than 52.2 dB, with low chirp (<|0.007|) operation.
We propose a novel method to measure chirp of an electro-absorption modulator at any frequency using optical homodyne quadrature demodulation technique. Chirp parameters are directly obtained in the small-signal vector space, enabling practical chirp assessment for advanced modulation optical transmission.
High-speed coherent transmission at 325 GHz is successfully demonstrated with a 20-Gbaud QPSK signal. A frequency-locked terahertz signal can be provided by an optical-modulation-based optical frequency comb signal. A high-gain antenna with a gain of 46 dBi is suitable to extend the transmission distance up to 15 m without requiring a terahertz amplifier.
The Radio over Fiber (RoF) technologies are unique transmission means of radio analog signals through optical fiber cables for radiocommunicatoion services. These technologies are currently discussed at international standard organizations such as ITU-T, IEC APT and IEEE802. This invited paper summarizes recent standardization activities on RoF technologies at those standard organizations.
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