382 research outputs found
Integrated microwave acousto-optic frequency shifter on thin-film lithium niobate
Electrically driven acousto-optic devices that provide beam deflection and
optical frequency shifting have broad applications from pulse synthesis to
heterodyne detection. Commercially available acousto-optic modulators are based
on bulk materials and consume Watts of radio frequency power. Here, we
demonstrate an integrated 3-GHz acousto-optic frequency shifter on thin-film
lithium niobate, featuring a carrier suppression over 30 dB. Further, we
demonstrate a gigahertz-spaced optical frequency comb featuring more than 200
lines over a 0.6-THz optical bandwidth by recirculating the light in an active
frequency shifting loop. Our integrated acousto-optic platform leads to the
development of on-chip optical routing, isolation, and microwave signal
processing
Characterization of Power-to-Phase Conversion in High-Speed P-I-N Photodiodes
Fluctuations of the optical power incident on a photodiode can be converted
into phase fluctuations of the resulting electronic signal due to nonlinear
saturation in the semiconductor. This impacts overall timing stability (phase
noise) of microwave signals generated from a photodetected optical pulse train.
In this paper, we describe and utilize techniques to characterize this
conversion of amplitude noise to phase noise for several high-speed (>10 GHz)
InGaAs P-I-N photodiodes operated at 900 nm. We focus on the impact of this
effect on the photonic generation of low phase noise 10 GHz microwave signals
and show that a combination of low laser amplitude noise, appropriate
photodiode design, and optimum average photocurrent is required to achieve
phase noise at or below -100 dBc/Hz at 1 Hz offset a 10 GHz carrier. In some
photodiodes we find specific photocurrents where the power-to-phase conversion
factor is observed to go to zero
A new frequency distribution architecture for wavelength division systems
Includes bibliographical references (p. 10-16)."Presented at Octima '91, Rome, Italy, January 1991."--Cover. Cover title.Research supported by DARPA. F19628-90-C-0002 Research supported by Bellcore, Nynex and NEC.Pierre A. Humblet, Peter C. Li
Optical Frequency Tuning for Coherent THz Wireless Signals
OAPACRWN THz wireless signals have become of interest for future broadband wireless communication. In a scenario where the wireless signals are distributed to many small remote antenna units (RAUs), this will require systems which allow flexible frequency tuning of the generated THz carrier. In this paper, we demonstrate experimentally the implementation of two tuning methods using an optical frequency comb generator (OFCG) for coherent optical frequency tuning in THz wireless-over-fiber systems. The first method is based on using a photonic integrated circuit optical phase lock loop (OPLL) sub-system implemented as a high quality optical filter for single comb line selection and optical amplification. The OPLL generates an optical carrier which is frequency and phase stabilized in reference to one of the optical comb lines with a frequency offset precisely selectable between 4 GHz and 12 GHz. The second method is based on optical single sideband suppressed carrier (SSB-SC) modulation from the filtered comb line using an optical IQ modulator. With this technique, it is possible to suppress the other unwanted optical tones by more than 40 dB. This generated optical carrier is then heterodyned with another filtered optical comb line to generate a tuneable and stable THz carrier. The full system implementations for both methods are demonstrated by transmitting THz wireless signal over fiber with 20 Gbps data in QPSK modulation. The system performance and the quality of the generated THz carrier are evaluated for both methods at different tuned THz carrier frequencies. The methods demonstrated confirm that a high quality tuneable THz carrier can easily be implemented in systems where dynamic frequency allocation is required
Integrated microwave acousto-optic frequency shifter on thin-film lithium niobate
Electrically driven acousto-optic devices that provide beam deflection and optical frequency shifting have broad applications from pulse synthesis to heterodyne detection. Commercially available acousto-optic modulators are based on bulk materials and consume Watts of radio frequency power. Here, we demonstrate an integrated 3-GHz acousto-optic frequency shifter on thin-film lithium niobate, featuring a carrier suppression over 30 dB. Further, we demonstrate a gigahertz-spaced optical frequency comb featuring more than 200 lines over a 0.6-THz optical bandwidth by recirculating the light in an active frequency shifting loop. Our integrated acousto-optic platform leads to the development of on-chip optical routing, isolation, and microwave signal processing
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