Abstract
We propose and experimentally demonstrate new architectures to realize multi-tap microwave photonic filters, based on the generation of a single or multiple dynamic Brillouin gratings in polarization maintaining fibers. The spectral range and selectivity of the proposed periodic filters is extensively tunable, simply by reconfiguring the positions and the number of dynamic gratings along the fiber respectively. In this paper, we present a complete analysis of three different configurations comprising a microwave photonic filter implementation: a simple notch-type Mach-Zehnder approach with a single movable dynamic grating, a multi-tap performance based on multiple dynamic gratings and finally a stationary grating configuration based on the phase modulation of two counter-propagating optical waves by a common pseudo-random bit sequence (PRBS).
Highlights
The interface between microwave engineering and optical signal processing is designated as Microwave Photonics (MWP) [1,2], an emergent area of research which enables the generation, transport and processing of radio frequency (RF), microwave and millimeter-wave signals directly in the optical domain [3,4]
One architecture for MWP filters that is prevalent in the literature relies on discrete-time processing [3,4,5]: delayed replicas of an optical wave, which is modulated by a microwave signal, are weighed and summed to obtain a desired finite impulse response
The pumps pulses were Gaussian shaped with a full width at half maximum (FWHM) of 400 ps, corresponding to a dynamic Brillouin grating (DBG) reflectivity bandwidth that is far broader than 1 GHz
Summary
The interface between microwave engineering and optical signal processing is designated as Microwave Photonics (MWP) [1,2], an emergent area of research which enables the generation, transport and processing of radio frequency (RF), microwave and millimeter-wave signals directly in the optical domain [3,4]. One architecture for MWP filters that is prevalent in the literature relies on discrete-time processing [3,4,5]: delayed replicas of an optical wave, which is modulated by a microwave signal, are weighed and summed to obtain a desired finite impulse response. Variable optical delay elements are key components in MWP filter implementations. Aiming at developing reliable MWP based filtering implementations, the efficient design of broadband and tunable delay lines is of key importance [5]. Among the wide diversity of optical delay line schemes that have been reported over the last decade [68], slow and fast light (SFL) has proved to be one potential approach to generate continuously tunable signal delays. The maximum achievable time delay in all SFL systems is essentially restricted by the delay-bandwidth product [9]
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