Comparison of optical processing techniques for optical microwave signal generation

Abstract

Recently, there have been several proposals on using the higher RF harmonics of detected pulses from mode-locked semiconductor lasers as a source of microwave and millimeter waves. This paper compares the performance of three optical techniques of signal processing that have been proposed to select a higher harmonic of a mode-locked laser, by using extensive numerical simulations. We show that techniques using delays and splitters are insensitive to the coherence properties of the source, but can introduce amplitude patterning if pulses overlap when recombined. We see that techniques relying on optical filtering to select optical modes require extremely high-Q filters and, thus, are extremely sensitive to tuning. A Fabry-Perot interferometer (FPI) is the optimum filter method in terms of power efficiency for low harmonics, but using two separate bandpass filters can give comparable efficiency when selecting higher harmonics. We also show that gain-switched lasers are unsuitable as sources when used with narrow-band optical filtering techniques because of their low pulse-to-pulse optical coherence.

<title>Simulation of laser sources for millimeter-wave signal generation</title>

“…The advantage of mode-locking is a lower timing jitter, as the pulse is seeded by the previous pulse returning from the optical cavity. Thus, mode-locked pulses are coherent, which is essential for some optical processing techniques which may be employed to modify the optical spectrum 15 Amode-locking technique is modelled in Section 4.3.…”

Photonic generation of microwave signals using dual-wavelength single-longitudinal-mode fiber lasers

“…The transmission of microwave signals over optical fiber is of great interest because optical fiber holds several advantages, such as wide bandwidth, low loss, and immunity to electromagnetic interference [1][2][3][4]. High-frequency microwave signal is expected to increase the capacity of the communication systems.…”

Tunable Photonic Microwave Generation Based on a Novel Dual-Polarization Fiber Laser Cavity

“…P HOTONIC generation of microwave signals has been the focus of much research for the past decades [1]- [5]. A straightforward technique to achieve this is to beat two laser beams from different laser sources whose frequencies differ by the required microwave frequency [6], [7].…”