A novel approach of true-time delay (TTD) optical feeder for phased-array antennas is proposed and demonstrated. A compact size continuously variable TTD is achieved by employing tunable lasers and one wide bandwidth chirped-fiber grating as dispersive element. A high-resolution performance (5.3 ps) is obtained for a 26-GHz phased-array antenna employing narrow tuning bandwidth lasers with a wavelength stability of 0.005 nm and a 4 nm bandwidth chirped grating.

It is demonstrated experimentally that the dramatic microwave-power degradation that appears in conventional 1550 nm lightwave amplitude modulated systems, due to chromatic dispersion, may be overcome by using tapered linearly chirped fibre gratings. An extension of the frequency-length product of fibre links in optical microwave/millimetre-wave systems can be achieved using chirped fibre gratings.

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.

The bandwidth limitation of a high-frequency analogue-to-digital (A/D) conversion technique based on photonic time-stretch is investigated. Single-sideband modulation of the electrical input signal is proposed to avoid this limitation. This technique is promising for A/D conversion of ultrafast signals (> 100 Gflops).

The electrical bandwidth limitation of continuous variable time delay units based on chirped fibre gratings is studied. The radiofrequency response of a linearly chirped fibre grating with an optical bandwidth of 4 nm and a dispersion of nearly 850 ps/nm has shown a –3 dB bandwidth of 6.4 GHz. To overcome this limitation, the use of a single-sideband plus carrier generator employing a dual-drive electro-optical modulator is experimentally demonstrated.

Chromatic dispersion effects in upconverted millimetre-wave fibre optic links employing electro-optical modulators are investigated. It is shown that by biasing the electro-optical modulator at the the minimum transmission point, instead of biasing at the quadrature point, the dispersion-induced carrier suppression effect on the upconverted signal may be sharply mitigated, which results in an increased frequency-length product in millimetre-wave optical systems.