Multitap microwave photonic filters with programmable phase response via optical frequency comb shaping

Abstract

We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration.

Comb-Based RF Photonic Filters Based on Interferometric Configuration and Balanced Detection

“…Among these sources, the EO-generated combs are very attractive for RF photonic filtering and other RF photonic signal processing due to their spectral flatness, high coherence, tunable repetition rate, and good stability [21], [22]. Our group has previously demonstrated reconfigurable RF photonic filters using an EO-generated comb and pulse shaper in an interferometric configuration [12]- [16]. Gaussian bandpass filters with fast (ß40 ns) tunability of the passband center frequency, high sidelobe suppression radio (>60 dB), and high stopband attenuation (>70 dB) were demonstrated in [15].…”

“…Reconfigurable flat-topped filters were reported in [14]. In [16] and [18], reconfigurable phase filters were implemented and applied for compression of wideband RF chirp signals. Using a similar comb-based RF filter configuration but without the interferometer, rapid (ß20 ns) bandwidth reconfiguration was demonstrated in [19], and simultaneous tunable bandpass filtering and downconversion was reported in [20].…”

Simultaneous broadband microwave downconversion and programmable complex filtering by optical frequency comb shaping

“…The need to introduce spectral quadratic phase (i.e., dispersion) to shift the resonance bandpass is due to the phase difference operation implicit in the tap coefficients. This is in contrast to the tuning mechanisms in other comb-based configuration that do not perform downconversion sampling [4][5][6], where tuning may be achieved in an interferometric configuration.…”

“…Thanks to these characteristics, MWP filters with high side-lobe suppression or submicrosecond tuning speeds have been reported [5]. When combined with line-by-line pulse shaping, reconfigurable filtering and programmable phase control is also possible [6]. These features are beyond the state of the art in electronics and illustrate very well the potential of MWPs.…”

Noise Comparison of RF Photonic Filters Based on Coherent and Incoherent Multiwavelength Sources

“…This approach is also easy to scale to a high number of taps while providing optical frequency stability, flexibility in tuning, and a coherence level not attainable from incoherent sources or typical harmonically mode-locked laser sources. When combined with optical line-by-line pulse shaping, this approach enables reconfigurable complex filtering [12], [13]. In direct-detection microwave links, OFCs also provide higher dynamic range than what can be achieved with a single laser, since they can overcome the power limitations due to Brillouin scattering [14].…”