Keizo Inagaki

60 GHz millimeter-wave source using two-mode injection-locking of a Fabry-Perot slave laser

We demonstrate 60 GHz carrier generation and transmission using a two-mode injection-locked Fabry-Perot (F-P) slave laser. The relationship between the power of the generated carriers and the frequency of the reference signal for the injection-locking is also investigated. The RF power-penalty caused by fiber dispersion was within 2.0 dB when the locked modes were transmitted at a distance of 0.5-48 km. Accordingly, the two-mode locked F-P laser can be used in fiber-based millimeter-wave systems.

Multiplexing of millimeter-wave signals for fiber-radio links by direct modulation of a two-mode locked Fabry-Pe/spl acute/rot laser

In this paper, we introduce generation of multiplexed signals on the millimeter-wave bands for fiber-radio systems where an optical millimeter-wave generator is based on a two-mode locked Fabry-Pe/spl acute/rot (FP) slave laser, whose injection current is directly modulated by a signal source. We qualitatively consider the distortion of the millimeter-wave signals from the FP slave laser. The distortion components on the millimeter-wave bands are induced from the simultaneous modulation of the locked modes and the nonlinear modulation response of the FP laser. Two-tone modulation of the locked FP laser is examined to evaluate the dynamic range of the millimeter-wave signals against the second- and third-order distortion components. We also perform fiber transmission of three 156-Mb/s-BPSK signals on the 60-GHz band to demonstrate fiber-radio down-link systems. The total capacity of the down-link system is discussed. In addition, two methods for multicarrier generation on the millimeter-wave bands are proposed. Multicarrier generators supported by these methods can be used as local signals for up-link millimeter-wave signals. The first method is based on multitone modulation of the FP slave laser. We attempt the down-conversion of a 52-Mb/s ASK signal on the 60-GHz band by using the millimeter-wave local signals. The second method depends on the distorted modulation of the FP slave laser by using a single continuous wave signal where the DC-bias level of the FP lasers injection current is partly under the threshold value. We confirm that five carriers on the 60-GHz band are effectively generated by using the second method. Furthermore, the influences of the chromatic dispersion effects on the millimeter-wave local signals are investigated for both methods.

Carrier generation and data transmission on millimeter-wave bands using two-mode locked Fabry-Perot slave lasers

This paper concerns an optical millimeter-wave signal generator for fiber-based millimeter-wave systems. The millimeter-wave signal generator is based on two-mode injection locking of a Fabry-Perot (F-P) laser. The millimeter-wave signal can be induced by self-heterodyne detection of the locked two modes in a high-speed photodetector (PD). The locking characteristics of the F-P slave laser and the tunability for the millimeter-wave carrier frequency are demonstrated. When the F-P laser is directly modulated by data signals, the locked two modes are modulated simultaneously. The data signals can then be up-converted to the millimeter-wave band at the PD output. By this direct modulation method, the effect of fiber chromatic dispersion on the millimeter-wave signal components at the PD output can be moderate according to mixing of amplitude and phase modulation on the locked two modes. In virtue of the wide response of the F-P laser, relatively high-speed data (2.5 Gbit/s nonreturn to zero (NRZ)-ASK or 622 Mbit/s NRZ-BPSK) on the millimeter-wave band (52 or 60 GHz) can be transmitted on a 32-km single-mode fiber without bit error. A wide tunable range (56-63 GHz) for the central frequency of the millimeter-wave signals and a wide optical bandwidth (1530-60 nm) of the F-P slave laser are also confirmed by the bit-error measurements of the transmitted data signals.

Two-dimensional optical signal-processing beamformer using multilayer polymeric optical waveguide arrays

Optically controlled beamforming techniques are very effective for phased-array antenna control. We have developed a two-dimensional (2-D) Fourier transform optical signal-processing (OSP) beamformer. In the OSP beamformer, we use multilayer polymeric optical waveguide arrays to generate and control a 2-D specific phase-front and sample 2-D distributed light beams. These multilayer optical waveguide arrays consist of three layers and 13 waveguides; each layer has four, five, and four waveguides, respectively. We experimentally demonstrate 2-D beam steering in the X-band, and show the feasibility of the 2-D OSP beamformer.

Birefringent photonic integrated circuit for beam forming network of independently steerable multibeam antenna

We report on the development of a beam forming network (BFN) for three independently steerable beams by a five-element array antenna integrated on a birefringent photonic integrated circuit (PIC) chip and measured phase shift characteristics of the BFN by optical wavelength tuning. In a coherent optical signal processing system transmitting an RF signal as the frequency difference of two lightwaves, the phase of the regenerated RF signal from the lightwaves is controlled by changing the relative phase difference between the two lightwaves, which requires only a small optical path control on the order of micrometers. The operating principle of the BFN is based on the combination of an optical Rotman lens technique for multibeam formation and an optical wavelength scanning technique to steer each beam independently.

Beam steering array antenna controlled by optical wavelength

We developed a beam forming network (BFN) for an array antenna with 5 elements radiating 3 independently steerable beams, and measured the phase shift characteristics. The main part of the BFN is integrated as a single photonic integrated circuit (PIC) chip using birefringent Lithium Niobate (LN) waveguide. The phase distribution among the 5 element antennas is controlled by the wavelength tuning of an optical RF source. Highly linear phase shift characteristics with the sensitivity of 8.24°/nm are achieved. By using 3 tunable optical RF sources allocated to different wavelength range, the PIC chip can generate feeding signals for 3 independently steerable beams.

A GaAs monolithic anti-series varactor pair for voltage-controlled capacitance with reduced RF nonlinearity

This paper presents a trial fabricated GaAs monolithic anti-series varactor pair. Its second-order and third-order harmonic distortions, which are generated from the nonlinearity of capacitance-voltage characteristics, are investigated experimentally and numerically. Compared to the case of a single varactor, the distortions of measurement and simulation are suppressed by about 25 dB and 45 dB for the second-order harmonic, and 3 dB and 10 dB for the third-order harmonic, respectively.