We present a microwave photonic link architecture that enables high gain and dynamic range, low noise figure, and
multi-octave bandwidth operation. Our method uses double sideband suppressed carrier modulation together with a
balanced coherent heterodyne detection scheme. The modulation method increases link linearity by producing carriersuppressed
amplitude modulation based on the optical field rather than intensity. The combination of carrier suppression,
optical amplification, phase-locked local oscillator insertion, and balanced detection provide high signal-efficient gain,
reduced intermodulation distortion, wide-band operation, frequency agile spectrum access, and low link noise.
Optical transmission of microwave signals offers many advantages such as increased bandwidth, immunity to electromagnetic interference, reduction of size and weight, and minimal loss over long distances. But microwave photonic links often lack the sufficiently high dynamic range and large instantaneous bandwidth required in many applications. Optical carrier suppression has been used to increase link dynamic range, but second harmonic distortion terms limit the operational bandwidth to sub-octave applications.
We present a method to apply carrier suppression to microwave photonic links while maintaining multi-octave operation. Our technique uses double sideband suppressed carrier modulation together with coherent heterodyne balanced detection to increase dynamic range, eliminate bandwidth-limiting second-order distortion terms, and reduce link noise figure. This approach provides efficient amplification of the modulated signal while limiting the effect of shot noise from the source laser and reducing common-mode noise terms such as source laser RIN and amplifier-related beat noise.
Optical implementation of RF filtering provides processing and switching advantages for analog optical links, bringing
additional versatility to the field of RF photonics. Many RF photonic notch filter designs have demonstrated this
increased link functionality, but most techniques are sensitive to polarization and phase noise, and are tunable over
limited ranges, set by the tunability limits of conventional link components such as DFB lasers. We demonstrate an RF
photonic notch filter with extremely wide tunability, high extinction ratio, and large range of useable bandwidths as part
of a high dynamic range RF photonic link. We discuss methods for improved filter operation, present experimental
results for X-band operation of the filter, and describe its use in applications such as co-site interference mitigation.
KEYWORDS: Optical amplifiers, Signal to noise ratio, Sensors, Interference (communication), Modulators, Signal detection, RF photonics, Analog electronics, Receivers, Photodiodes
Optical down-conversion techniques have become an increasingly popular architecture to realize Multi-band Enterprise
Terminals (MET), Synthetic Aperture Radar (SAR), Optical Arbitrary Waveform Generation (OAWG), RF Channelizers
and other technologies that need rapid frequency agile tunability in the microwave and millimeter RF bands. We describe
recent SFDR, NF, Gain, and Noise modeling and measurements of Erbium-doped-fiber amplified analog RF optical
links implementing all-optical down-conversion and balanced photodiode receivers. We describe measurements made on
our newly designed extensive test-bed utilizing a wide array of high powered single and balanced photodiodes,
polarization preserving output LN modulators, EAMs, LIMs, tunable lasers, EDFAs, RF Amplifiers, and other
components to fully characterize direct and coherent detection techniques. Additionally, we compare these experimental
results to our comprehensive MATLAB system modeling and optimization software tools.
We present the first mm-wave characterization of Semimetal Semiconductor Schottky (S3) diodes for direct detector applications from 94 GHz to 30 THz. The S3 devices use molecular-beam epitaxy growth of binary compounds that are closely lattice-matched and crystallographically perfect across the heterointerface to reduce 1/f and burst noise while maintaining ultra-high-frequency performance. The S3 diodes are fabricated from an InAlGaAs/InP based material system with both the Schottky layer and contact layer having n and n+ doping levels. The semimetal Schottky contact is ErAs which is grown in-situ during the MBE growth. By varying the InAlAs percentage content in the epitaxial layer structure, the diode dc I-V characteristics and its zero bias responsivity are optimized. Diode s-parameter data from dc-100 GHz is used to determine the diode responsivity as a function of frequency and diode capacitance and resistance. These measurements then allow the device intrinsic and extrinsic equivalent-circuit elements to be optimized for direct detection from 94 GHz to ~30 THz.
An antenna-coupled metal-oxide-metal (MOM) diode for dual-band Infrared (IR)-millimeter wave (MMW) detection is presented. Electron-beam lithography and conventional sputtering techniques were used to fabricate a Ni-NiO-Ni diode coupled to an Infrared slot antenna at 28 THz and a coplanar waveguide (CPW)-fed MMW twin slot antenna at 94 GHz; simultaneous dual-band detection was tested and verified.
We built and tested a low-cost 8-by-8 millimeter-wave focal plane array using antenna-coupled micro-bolometers. The array consists of slot antennas coupled to nickel bolometers and was fabricated using optical lithography on high-resistivity silicon wafers. The measured noise equivalent temperature difference (NETD) of an individual element was 450 K. Simulation results corresponded with observed device performance. An improved design was then implemented using a square spiral antenna. We discuss the fabrication of this type of array element, include some modeling results, and present the methods and results of our measurements.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.