Yoshihiko Mizuguchi

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.

Spatial optical beam-forming network for receiving-mode multibeam array antenna - proposal and experiment

This paper proposes an array antenna for multibeam reception with a beam-forming network (BFN) that uses spatial optical signal processing and also presents experimental results. In this antenna, signals received at individual antenna elements are converted to optical signals, and are optically divided from the directions of signal arrival by means of optical spatial Fourier transformation, and then the optical signals are reconverted into microwave signals at the BFN. In this BFN, to maintain optical path-length conditions, an optical integrated circuit is employed. We have experimentally investigated the optical signal processing performances of the BFN for multibeam reception. The experimental results show that optical beam direction is changed according to the signal arrival direction of an array antenna. Two multiple RF signals with different phase distributions are separated. The sidelobe level of the optical signal is reduced when amplitude distributions of optical signals are Chebyshev distributions. We also present the signal transmission behavior of this BFN. The measured carrier-to-noise-ratio degradation of this BFN is 2 dB at BER=10/sup -6/ when 118.125-Mb/s QPSK modulated signal is input into the BFN.

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.

IF signal transmission at 60 GHz-band using direct modulation of a two-mode locked Fabry-Perot slave laser

We demonstrate the fiber transmission of an IF signal at 60 GHz-band using a two-mode injection-locked Fabry-Perot slave laser for fiber radio systems. The IF signal can be generated by the CW modulation of the slave laser without using an optical intensity-modulator. We confirm the fast response of the modulated slave laser and a 77 dB dynamic range for signal modulation against third-order distortion. The IF signals power deviation caused by fiber dispersion is also investigated.

Development of an adaptive array based on subband signal processing

Adaptive arrays are recognized as a solution to multipath fading environments that can be a serious problem in high-speed mobile communication systems. However, huge computational loads are required due to its spatio-temporal signal processing. Subband signal processing has been known as a parallel signal processing scheme on the frequency domain. It allows us to allocate heavy computational loads to several processors when it is implemented in digital signal processors (DSPs) or field programmable gate arrays (FPGAs) and so on. Basically, the performance of adaptive arrays based on subband signal processing is identical to that based on time domain signal processing. However, several types of configurations are possible. As a result, there is a configuration that is very advantageous in terms of the computational reduction even though its performance is slightly degraded compared to one configured in the time domain. In this paper, an adaptive array based on subband signal processing that can intensively reduce computational loads is implemented by using DSPs and its performance is verified through experiments in an anechoic chamber. Finally, the computational loads of adaptive arrays are examined and the implemented adaptive array is shown to realize very efficient signal processing.

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.