Edward I. Ackerman

Bio: Edward I. Ackerman is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Noise figure & Signal. The author has an hindex of 26, co-authored 67 publications receiving 2323 citations. Previous affiliations of Edward I. Ackerman include Drexel University & Carlisle Companies.

Limits on the performance of RF-over-fiber links and their impact on device design

Abstract: This paper is divided into two major parts. Following a brief introduction that establishes some definitions and assumptions, Section II updates our earlier study on the limits of the RF performance of optical links. Section III reviews progress since our 1997 review paper in the development of devices enabling link performance closer to these limits, including (but not limited to): 1) cascade lasers that permit broad-band direct modulation links with gain >0 dB; 2) injection-locked edge- and surface-emitting lasers at 1300 and 1550 nm with modulation frequency responses as great as 40 GHz; 3) modulators with improved performance, especially electroabsorption modulators that now have switching voltages as low as 0.36 V, or handle optical powers as great as 60 mW, or have bandwidths as great as 50 GHz (but not all three of these in one device yet); and 4) high-speed photodetectors with high saturation currents, e.g., a 20-GHz device with a saturation current of 90 mA and a 55-GHz device with saturation at 50 mA. We conclude in Section IV by summarizing the component developments necessary for higher performance RF-over-fiber links, i.e.: 1) semiconductor lasers (for direct modulation) that have higher slope efficiency and bandwidth and lower relative intensity noise (RIN) at reasonable bias current levels; 2) continuous wave (CW) lasers (for external modulation) with higher fiber-coupled power and lower RIN; 3) higher frequency lower loss external modulators with more linear transfer functions and lower V/sub /spl pi// that can withstand larger CW optical powers; and 4) photodetectors with higher responsivity and bandwidth that respond linearly even when illuminated by greater average optical powers.

Corrections to "Limits on the Performance of RF-Over-Fiber Links and Their Impact on Device Design"

Abstract: The authors correct an error in their original article (see ibid., vol.54, no.2, p.906-20, Feb. 2006).

Direct-detection analog optical links

Abstract: We review state-of-the-art intensity-modulation direct-detection (IMDD) analog optical links, focusing on advances since 1990. We contrast direct and external modulation with respect to gain, noise figure, and dynamic-range performance.

Broad-band linearization of a Mach-Zehnder electrooptic modulator

Abstract: Analog optical-link dynamic range in excess of 75 dB in a 1-MHz band has been achieved using specially designed electrooptic modulators that minimize one or more orders of harmonic and intermodulation distortion. To date, however, such "linearized" modulators have only enabled improved link dynamic ranges at frequencies below 1 GHz. Additionally, linearization across more than an octave bandwidth has required precise balancing of the signal voltage levels on multiple electrodes in a custom modulator, which represents a significant implementation challenge. In this paper, a link linearization technique that uses a standard Mach-Zehnder lithium-niobate modulator with only one RF and one dc-bias electrode to achieve broad-band linearization is discussed, resulting in a dynamic range of 74 dB in 1 MHz across greater than an octave bandwidth (800-2500 MHz). Instead of balancing the voltages on two RF electrodes, the modulator in this new link architecture simultaneously modulates optical carriers at two wavelengths, and it is the ratio of these optical carrier powers that is adjusted for optimum distortion canceling. The paper concludes by describing a second analogous link architecture in which it is the ratio of optical power at two modulated polarizations that is adjusted in order to achieve broad-band linearization.

RF fiber-optic link performance

Abstract: Applications that involve point-to-point routing of analog signals have benefited from the excellent propagation characteristics of optical fiber. Fiber-optic links that remote RF signals to and from phased-array radar antennas must meet especially stringent performance requirements. The past decade has seen significant progress in the performance of the fiber-optic links that distribute RF signals in antenna-remoting applications, as well as in cellular communications and cable television signal distribution networks. This article reviews the present state of the art in RF fiber-optic links.

Microwave Photonics

Abstract: Broadband and low loss capability of photonics has led to an ever-increasing interest in its use for the generation, processing, control and distribution of microwave and millimeter-wave signals for applications such as broadband wireless access networks, sensor networks, radar, satellite communitarians, instrumentation and warfare systems. In this tutorial, techniques developed in the last few years in microwave photonics are reviewed with an emphasis on the systems architectures for photonic generation and processing of microwave signals, photonic true-time delay beamforming, radio-over-fiber systems, and photonic analog-to-digital conversion. Challenges in system implementation for practical applications and new areas of research in microwave photonics are also discussed.

A review of lithium niobate modulators for fiber-optic communications systems

Abstract: The current status of lithium-niobate external-modulator technology is reviewed with emphasis on design, fabrication, system requirements, performance, and reliability. The technology meets the performance and reliability requirements of current 2.5-, 10-, and 40-Gb/s digital communication systems, as well as CATV analog systems. The current trend in device topology is toward higher data rates and increased levels of integration. In particular, multiple high-speed modulation functions, such as 10-Gb/s return-to-zero pulse generation plus data modulation, have been achieved in a single device.

A tutorial on microwave photonic filters

Abstract: Microwave photonic filters are photonic subsystems designed with the aim of carrying equivalent tasks to those of an ordinary microwave filter within a radio frequency (RF) system or link, bringing supplementary advantages inherent to photonics such as low loss, high bandwidth, immunity to electromagnetic interference (EMI), tunability, and reconfigurability. There is an increasing interest in this subject since, on one hand, emerging broadband wireless access networks and standards spanning from universal mobile telecommunications system (UMTS) to fixed access picocellular networks and including wireless local area network (WLAN), World Interoperability for Microwave Access, Inc. (WIMAX), local multipoint distribution service (LMDS), etc., require an increase in capacity by reducing the coverage area. An enabling technology to obtain this objective is based on radio-over-fiber (RoF) systems where signal processing is carried at a central office to where signals are carried from inexpensive remote antenna units (RAUs). On the other hand, microwave photonic filters can find applications in specialized fields such as radar and photonic beamsteering of phased-arrayed antennas, where dynamical reconfiguration is an added value. This paper provides a tutorial introduction of this subject to the reader not working directly in the field but interested in getting an overall introduction of the subject and also to the researcher wishing to get a comprehensive background before working on the subject.

Photonic signal processing of microwave signals

Abstract: Photonic signal processing offers the prospect of realizing extremely high multigigahertz sampling frequencies, overcoming inherent electronic limitations. This stems from the intrinsic excellent delay properties of optical delay lines. These processors provide new capabilities for realizing high time-bandwidth operation and high-resolution performance. In-fiber signal processors are inherently compatible with fiber-optic microwave systems and can provide connectivity with built-in signal conditioning. Fundamental principles of photonic signal processing, including sampling, tuning, and noise, are discussed. Structures that can extend the performance of photonic signal processors are presented, including methods for improving the filter shape characteristics of interference mitigation filters, techniques to increase the stopband attenuation of bandpass filters, and methods to achieve large free spectral range. Several photonic signal processors, including high-resolution microwave filters, widely tunable filters, arbitrary waveform generators, and fast signal correlators, are discussed. Techniques to solve the fundamental noise problem in photonic signal processors are described, and coherence-free structures for few-tap notch filters are discussed. Finally, a new concept for realizing multiple-tap coherence-free processor filters, based on a new frequency-shifting technique, is presented. The structure not only eliminates the phase-induced intensity noise limitation, but can also generate a large number of taps to enable the achievement of processors with high performance and high resolution.