V. Polo

Optically beamformed beam-switched adaptive antennas for fixed and mobile broad-band wireless access networks

In this paper, a 3-bit optical beamforming architecture based in 2/spl times/2 optical switches and dispersive media is proposed and demonstrated. The performance of this photonic beamformer is experimentally demonstrated at 42.7 GHz in both transmission and reception modes. The progress achieved for realizing these architectures with integrated optics is also reported. Due to its advanced features (i.e., potential fast-switching, huge bandwidth, and immunity to electromagnetic interference), the architecture is a very promising alternative to traditional beamforming technologies for implementing beamformed base-station antennas in fixed and mobile broad-band wireless access networks operating in the millimeter-wave band. The study presented here has been carried out in the frame of the IST 2000-25390 OBANET project.

Novel tunable photonic microwave filter based on laser arrays and N/spl times/N AWG-based delay lines

In this letter, a novel tunable and flexible photonic microwave filter architecture based on the use of laser arrays and the periodicity of N/spl times/N arrayed-waveguide-gratings optical response is proposed. Filter coarse and fine-tuning capabilities are experimentally demonstrated showing an excellent agreement with theory.

On the use of fiber-induced self-phase modulation to reduce chromatic dispersion effects in microwave/millimeter-wave optical systems

In this letter, a novel approach to compensate for the dispersion-induced power penalty in externally modulated 1550-nm analog fiber-optic systems is presented. The principle is based on the use of fiber-induced self-phase modulation to generate a chirp distortion effect opposite to that induced by the chromatic dispersion. A significant reduction of chromatic dispersion effects is achieved, which results in augmenting the frequency-length product of the fiber-optic link. It is theoretically and experimentally shown how this dispersion compensation may be controlled by means of the optical power injected to the optical fiber.

Generalized study of dispersion-induced power penalty mitigation techniques in millimeter-wave fiber-optic links

The authors present a comprehensive analysis of the chromatic dispersion effects in harmonic upconverted millimeter-wave (mm-wave) fiber-optic links. The optical upconversion is performed through a photonic mixer based on a Mach-Zehnder electrooptical modulator. It is shown that by biasing the electrooptical modulator either at the maximum or at the minimum transmission bias points, the dispersion-induced power penalty effect on the upconverted signal may be sharply mitigated, which results in increasing the frequency-length product of the fiber-optic link. Experimental results are provided for the three different types of bias.

Compensation of chromatic dispersion effects in microwave/millimeter-wave optical systems using four-wave-mixing induced in dispersion-shifted fibers

The authors report theoretical and experimental results on the compensation of chromatic dispersion effects in microwave/millimeter-wave optical systems employing four-wave mixing (FWM) induced in dispersion shifted fiber (DSF). The technique is based on generating a phase-conjugated wave by means of FWM in a 12.7-km-long DSF placed at the midspan of the fiber-optic link. The experimental results show that by using FWM a complete compensation of the electrical carrier suppression effect in a 50-km standard single-mode-fiber optic link is achieved.

Harmonic suppressed photonic microwave filter

This paper proposes a photonic microwave filter based on wavelength-division multiplexing (WDM) of multiple optical carriers and dispersive media. Harmonic suppression is obtained using nonuniform tap spacing to extend the filter free spectral range by a Vernier effect. The experimental results presented are in excellent agreement with theory.

Efficient architecture for WDM photonic microwave filters

A novel technique to reduce the number of components in photonic microwave filters implemented using multiple optical carriers (wavelength-division multiplexing) and dispersive media is presented and experimentally demonstrated. This technique is based on using jointly dispersive and nondispersive media to reuse the optical carriers and, therefore, to reduce the number of filter components. The technique allows the implementation of filters showing N/spl times/M taps using N+M components instead of N/spl times/M components, as required in previous proposals.

Ten gigabits per second 16-level quadrature amplitude modulated millimeter-wave carrier generation using dual-drive Mach–Zehnder modulators incorporated photonic-vector modulator

A novel photonic-vector modulator architecture for the generation of 16 quadrature amplitude modulation (16 QAM) millimeter-wave carriers using dual-drive Mach-Zehnder modulators is proposed. Experimental generation of 5 Gbits/s 4 amplitude shift-keying (4 ASK) and 10 Gbits/s 16 QAM modulated 42 GHz carriers is reported. The multilevel modulated millimeter-wave signals are demodulated using an electrical receiver and its error-vector magnitude (EVM) estimated from the measurements, obtaining EVMs of -21.04 and -18.33 dB for 4 ASK and 16 QAM modulation formats, respectively.

Direct photonic generation of electrical vector modulations at microwave/millimeter-wave frequencies

In this letter, a novel quadrature photonic vector modulator architecture is proposed. An electrical quadrature-modulated signal at microwave/millimeter-wave frequencies is generated from its corresponding base-band in-phase (I) and quadrature (Q) components. In the proposed scheme, no electrical devices apart from the electrical tone oscillator are needed in the generation process and, therefore, high data rates at high electrical frequencies can be obtained. In addition, the hardware requirements are reduced when compared to previously proposed architectures so a highly compact low-cost architecture can be implemented. Experimental results demonstrate the feasibility of the architecture.

Experimental demonstration of dispersion-tolerant 155-Mb/s BPSK data transmission at 40 GHz using an optical coherent harmonic generation technique

The transmission of 155-Mb/s binary phase-shift keying data at 40 GHz through a 2.2-km standard single-mode fiber link is experimentally demonstrated by using a flexible technique for dispersion-tolerant optical coherent harmonic generation of modulated microwave/millimeter-wave signals which also allows simultaneous local-oscillator remoting. The proposed technique employs a single laser and a single dual-drive Mach-Zehnder modulator. Experimental results show bit-error-rate <10/sup -9/ operation at millimeter-wave frequencies which makes the proposed technique suitable for next-generation broad-band wireless access networks.