Charles Middleton

Linear phase-and-frequency-modulated photonic links using optical discriminators.

We report our experimental results for linear analog optical links that use phase or frequency modulation and optical discrimination. The discriminators are based on two architectures: a cascaded MZI FIR lattice filter and a ring assisted MZI (RAMZI) IIR filter. For both types of discriminators, we demonstrate > 6 dB improvement in the links third-order output intercept point (OIP3) over a MZM link. We show that the links have low second-order distortion when using balanced detection. Using high optical power, we demonstrate an OIP3 of 39.2 dBm. We also demonstrate 4.3dB improvement in signal compression.

Reconfigurable Linear Optical FM Discriminator

We present a reconfigurable optical discriminator filter for frequency modulated microwave-photonics link applications. The filter is based on a simplified ring-assisted Mach-Zehnder interferometer configuration. It enables conversion of a highly linear frequency to amplitude modulation. Operations in a fixed bandwidth (BW) of 30 GHz and a tunable bandwidth from 10 to 30 GHz are achieved using third- and fifth-order filters. A balanced frequency discrimination architecture with electronically reconfigurable transfer characteristics is demonstrated. We measured a output-third order intercept point (OIP3) linearity improvement over that of a dual-output Mach-Zehnder.

Extending frequency and bandwidth through the use of agile, high dynamic range photonic converters

RF photonic techniques can be used to extend operating frequencies and bandwidth of mission communications and sensing systems. Photonic links inherently cover wide frequency bandwidths and optical modulators and detectors have been demonstrated that operate up to 100 GHz. This paper presents a photonic method for tunable high frequency carrier generation and wideband tunable RF frequency conversion. Photonic down-conversion measurements are presented with +24 dBm OIP3 and positive gain across RF input signals from 5 to 20 GHz. Additionally, measurements of undesired higher order mixing spurious products were more than 30 dB lower than those of typical RF mixers. Coupling wide-band optical components with a reconfigurable RF payload provides unprecedented agility and multi-mission utility for remote sensing, communications and SAR radar missions.

Improved microwave photonic link performance through optical carrier suppression and balanced coherent heterodyne detection

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.

High performance microwave photonic links using double sideband suppressed carrier modulation and balanced coherent heterodyne detection

Optical transmission of microwave signals offers many advantages such as increased bandwidth; immunity to electromagnetic interference; reduction of size, weight and power consumption; and low, frequency-independent loss over long distances. But microwave photonic links often lack the performance required to replace traditional microwave links. 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 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, and low link noise. The resulting link places this microwave photonic approach in the same performance realm as state-of-the-art microwave links.

Scalable Photonic-Assisted Wideband Frequency Converter

We present a photonic-assisted wideband tunable RF frequency converter with low phase noise to provide RF to IF frequency translation, and demonstrate 121 dB*Hz^2/3 spur-free dynamic range at 20 GHz RF and 2 GHz IF.

Photonic-based low phase noise frequency synthesis for RF-to-millimeter wave carriers and wideband RF-to-IF down-conversion

We present a photonic method for tunable high frequency carrier generation and wideband tunable RF frequency down-conversion with low phase noise. The phase noise of the photonic generated RF/IF signal is limited by the RF signal generator used to synthesize the optical local oscillators. We show phase noise measurements of photonic frequency synthesized carriers at 24 GHz and down-conversion measurements with +24 dBm OIP3 and positive gain from 5 – 20 GHz RF and 100 MHz IF, with ADC-limited digitization.

Eliminating co-location radio interference with photonic-enhanced spectrum management in cognitive radio networks

Co-location of RF emitters (communications plus jammer) is a problem in tactical operations where the goal within a tactical platform is to maintain blue force communications and deny (jam) red force communications or, indeed, any red force use of spectrum. Dynamic Spectrum Access (DSA) on the DARPA neXt generation (xG) communications program [1] has a goal to sense and share spectrum for more efficient use. A port and test of this DSA capability from a commercial radio to a tactical radio showed significant improvement in tactical communications in a jamming environment.

Balanced coherent heterodyne detection with double sideband suppressed carrier modulation for high performance microwave photonic links

Optical transmission of microwave signals offers many advantages such as increased bandwidth; immunity to electromagnetic interference; reduction of size, weight and power consumption; and low, frequency independent loss over long distances. But microwave photonic links often lack the performance required to replace traditional microwave links. 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 (DSB-SC) modulation together with a balanced coherent heterodyne detection scheme. The modulation method increases link linearity by producing 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 performance microwave photonic links.

Dynamic linearity improvement of phase and frequency modulated microwave photonic links using optical lattice filter discriminators

A phase modulated (PM) microwave photonic link (MPL) with linearity improvement is presented. The link demodulates the PM using a phase discriminator based on a dynamically tunable, integrated, sixth-order optical lattice filter in planar lightwave circuit (PLC) technology. The linearity of the demodulation process is optimized by using electrical spectrum monitoring and a feedback algorithm to automatically choose the filter coefficients. For a 2 GHz modulation frequency, the link achieves a 6.7 dB improvement in the third-order output intercept point (OIP3) for intermodulation distortion (IMD) over a Mach-Zehnder interferometer (MZI).