William D. Jemison

A mode-locked microchip laser optical transmitter for fiber radio

This paper is concerned with the optical domain generation of high-quality millimeter-wave signals for fiber-radio and other applications. The mode-locked millimeter-wave optical transmitter described is based on simple electrooptic microchip laser technology. The transmitter can be designed to operate from a few gigahertz to 100 GHz and beyond. The residual phase noise of the laser is below -100 dBc/Hz at 1-kHz offset, which makes it well suited for optically fed millimeter-wave wireless applications. A key feature of the transmitter is its simplicity, the very small number of elements it employs and the high level of integration of the millimeter-wave and photonic components that results in a small, rugged, and reliable package. The paper describes the design, fabrication, and experimental evaluation of the transmitter.

Hybrid fiberoptic-millimeter-wave links

Combining fiberoptics for point-to-point communication and millimeter waves for short-range wireless communication simultaneously provides fast data rates, high security levels, and mobility. The article describes the system architecture, including some of the key design tradeoffs that have been and are currently being considered, and the demonstration/validation (DEMVAL) results. Highlights of the progress include the transmission of data, digital video, and voice from a fixed computer terminal to a portable/wearable computer over the hybrid fiberoptic/millimeter-wave link. These results demonstrate system architecture proof-of-concept as well as significant risk reduction in critical subsystems.

Analysis of the AO-FDPC optical heterodyne technique for microwave time delay and phased array beamsteering applications

This paper presents a theoretical analysis of the application of the acousto-optic frequency-dependent phase compensated (AO-FDPC) optical heterodyne technique for microwave time delay applications and phased array beamsteering. A primary goal of the paper is to resolve open questions that have been associated with this interesting and highly referenced technique. The work presented here quantifies, for the first time, the fundamental time delay performance bounds of this technique in terms of the parameters associated with the AO-FDPC acousto-optic (AO) cell and the signal bandwidth. The theory presented in this paper is used to interpret previously reported experimental results that have been subject to debate. Much of the theoretical approach is general and may, therefore, be modified to address the design of new FDPC approaches. Finally, the wide-band beamsteering performance that can be achieved with this technique is quantified in terms of the AO cell parameters and phased array specifications.

Fiber radio: from links to networks

Various fiber radio link architectures have been developed to transmit modulated microwave or MM-wave signals over fiber. However, the issue of how to integrate these links into a network topology remains an open issue. This paper addresses one method that can be used to develop a transparent fiber radio network.

A coherent fiber-optic link with optical-domain down-conversion and digital demodulation

Frequency down-conversion is an essential element of radar signal processing. Classical electronic down-conversion using heterodyne mixing, however, introduces unavoidable non-linearities resulting in inter-modulation distortion and conversion loss. In this paper we describe a hybrid optical/digital downconversion technique that is free of distortion and conversion loss. Experimental results are presented showing proof-of-concept operation limited to the dynamic range of the A/Ds that were available for the experiment. The ultimate goal is to attain an SFDR of 150 dB-Hz2/3 or higher across an instantaneous bandwidth of 1 GHz for a microwave carrier up to 100 GHz.

Coupled Optoelectronic Oscillation via Fundamental Mode-Locking in a Composite-Cavity Electro-Optic Microchip Laser

Composite-cavity electro-optic microchip lasers have been proposed as a source for high-speed, low-noise microwave and optical signals. Such signals can be produced from a single short-cavity laser using the coupled optoelectronic oscillation architecture, but strict control of the cavity longitudinal modes must be maintained to achieve fundamental mode-locking. The mechanism for this control is studied analytically and it is determined that the Lorentzian gain approximation does not predict nonadjacent modal effects in short-cavity lasers. A modification is presented which can explain these effects. Experimentally, the modal structure of an adjustable short-cavity laser is investigated and the results are consistent with the revised model. Finally, the results of the theory are used to design an optimized cavity geometry that is used to successfully demonstrate FM mode-locking and coupled optoelectronic oscillation at 20 GHz using a Nd:YVO4/MgO:LiNbO3 prototype.

A Novel Class E Analog Fiber Optic Link with RF Power Gain and High DC-RF Conversion Efficiency

A novel analog fiber optic link is described that incorporates class E switching amplifier techniques in the link architecture to provide RF power gain with high post-detector dc-RF conversion efficiency. The proof-of-concept link was designed to operate at a nominal design frequency of 70 MHz and has an RF gain of 30 dB and a maximum post-detector power amplifier dc-RF conversion efficiency of 78%

Performance limits of a hybrid fiber/millimeter-wave wireless system

This paper reports a physical layer performance analysis for a hybrid fiber/wireless millimeter-wave communications system. The impact of the fiber link is carefully considered together with the microwave link budget. Vector modulation measurements are used to assess the quality of the fiber link.

An automatic gain control circuit with TiO 2 memristor variable gain amplifier

An automatic gain control (AGC) topology with a variable gain amplifier (VGA) utilizing a titanium dioxide (TiO 2 ) memristor is described. A system analysis technique is developed based on recently published physical memristor models and unique properties of the passive device. A linearized feedback loop amplitude model is used to design the AGC and the performance is verified with SPICE simulation including a TiO 2 memristor SPICE model.

A new optoelectronic oscillator topology based on a class E analog fiber optic link

A new optoelectronic oscillator (OEO) topology based on a class E analog fiber optic link is presented. This topology provides a high level of inherent opto-electronic conversion gain in the analog fiber optic link portion of the OEO thus eliminating the need for dedicated post-detector gain. The class E operation also allows for dual loop operation using a single optical detector and can provide good dc-RF efficiency. A proof-of-concept dual loop OEO was designed at 77 MHz and experimental results are reported that validate the proposed topology.