Showing papers by "Alwyn J. Seeds published in 1997"
TL;DR: In this paper, the first experimental results for optoelectronic mixing using a two-terminal edge-coupled InP/InGaAs heterojunction phototransistor (HPT) were reported.
Abstract: We report the first experimental results for optoelectronic mixing using a two-terminal edge-coupled InP/InGaAs heterojunction phototransistor (HPT). The HPT optoelectronic mixer (OEM) exhibits a maximum of 7-dB conversion gain relative to a 100% quantum efficient photodetector operated at the optical modulation frequency. We give a qualitative explanation for the observed conversion gain variation with the HPT bias voltage.
42 citations
TL;DR: In this article, the first theoretical analysis and experimental realization of an optical frequency modulation coherent detection (FMCD) link working at microwave frequencies is reported, and a detailed theoretical analysis of the SNR of FMCD links is carried out and compared to that for IMDD links.
Abstract: In this paper, the first theoretical analysis and experimental realization of an optical frequency modulation coherent detection (FMCD) link working at microwave frequencies is reported. Advantages over conventional optical intensity modulation direct detection (IMDD) links in terms of reduced effects of fiber nonlinearity, facilitation of multichannel operation, and bandwidth/signal-to-noise ratio (SNR) tradeoffs are identified. A detailed theoretical analysis of the SNR of FMCD links is carried out and compared to that for IMDD links. In the experimental FMCD link, a novel source laser tuning technique, based on the quantum confined Stark effect, is used. The experimental results are presented and compared with the predictions of the theoretical analysis.
31 citations
03 Sep 1997
TL;DR: In this paper, the first experimental results for an heterodyne optical injection phase-lock loop are reported, with phase error variance as low as 0.003 rad/sup 2/ in a bandwidth of 100 MHz, single-sideband (SSB) noise density of -94 dBc/Hz at 10-kHz offset and mean time to cycle slip of 3/spl times/10/sup 10/ s have been achieved using DFB lasers of 36-MHz summed linewidth, a loop propagation delay of 20 ns and an injection ratio of -30 dB.
Abstract: The requirements for narrow linewidth lasers or short-loop propagation delay limit optical phase-lock loop realizability with semiconductor lasers. Although optical injection locking can provide low-phase-error variance, its locking range is limited by stability considerations. The first experimental results for an heterodyne optical injection phase-lock loop are reported. Phase-error variance as low as 0.003 rad/sup 2/ in a bandwidth of 100 MHz, single-sideband (SSB) noise density of -94 dBc/Hz at 10-kHz offset and mean time to cycle slip of 3/spl times/10/sup 10/ s have been achieved using DFB lasers of 36-MHz summed linewidth, a loop propagation delay of 20 ns and an injection ratio of -30 dB.
22 citations
08 Jun 1997
TL;DR: In this article, a review of technologies for providing broadband wireless access using millimetre-wave over fiber-optic systems is presented. But the authors focus on the use of optical phase lock loop techniques and signal detection using optically controlled heterojunction phototransistors.
Abstract: The paper reviews technologies for providing broadband wireless access using millimetre-wave over fibre systems. Recent advances in modulated signal generation using optical phase lock loop techniques and in signal detection using optically controlled heterojunction phototransistors are also described.
22 citations
03 Sep 1997
13 citations
TL;DR: In this article, a multiple quantum well ridge guide laser tuned by the quantum confined Stark effect has been reported, and the frequency modulation response of the laser is highly uniform (± 0.7 dB) over the frequency range from 10 kHz to 100 MHz, with the upper frequency parasitic capacitance limited.
Abstract: We report a multiple quantum well ridge guide laser tuned by the quantum confined Stark effect. In contrast to carrier-induced effect tuned lasers, the frequency modulation response of our laser is highly uniform (±0.7 dB) over the frequency range from 10 kHz to 100 MHz, and within ±2.5 dB from 5 kHz to 500 MHz, with the upper frequency parasitic capacitance limited. We predict that the response could be extended to over 20 GHz by using a low parasitic contacting structure.
12 citations
23 Oct 1997
TL;DR: In this article, the authors describe the construction of a laser-diode OPLL subsystem for evaluation in a proof-of-concept beamforming system, which involves optimization of the loop design, development of single-frequency laser diodes with the correct linewidth, modulation and tuning characteristics and integration into a micro-optic assembly with custom wideband electronics.
Abstract: A coherent, optical heterodyne approach to signal generation and beamforming is particularly advantageous in multi-beam mobile phased arrays. Use of optical technology allows an optimum distribution of weight and power to be achieved between the antenna face and central electronics, together with an efficient implementation of the beamforming function and a modular design approach in which the basic building blocks are frequency-independent. Systems of this type employ a pair of optical carriers with a difference frequency equal to the required microwave signal. Phased- locking is necessary in order to achieve sufficiently low phase noise in the radio communication link. Optical phase locked loops (OPLLs) have been shown to be potential candidates for this application, yet work still needs to be done to bring them from the laboratory to field demonstrations. This paper describes the construction of a laser-diode OPLL subsystem for evaluation in a proof-of- concept beamforming system. This involves optimization of the loop design, development of single-frequency laser diodes with the correct linewidth, modulation and tuning characteristics and integration into a micro-optic assembly with custom wideband electronics.
7 citations
08 Jun 1997
TL;DR: In this article, a three-terminal InP/InGaAs heterojunction bipolar transistor (HBT) with optical access has been fabricated and used in an optoelectronic mixer (OEM) configuration.
Abstract: A three-terminal InP/InGaAs heterojunction bipolar transistor (HBT) with optical access has been fabricated and used in an optoelectronic mixer (OEM) configuration. Leakage of the photogenerated RF signal from the HBT base was identified as a cause of reduced mixed IF output power. By using a 3-stub tuner to present a high impedance to the base at signal frequency, over 5 dB improvement in the IF power was obtained resulting in a -4.7 dB system conversion gain. This result is the highest yet reported for a three-terminal HBT OEM and over 16 dB better than for a high quality photodiode/double-balanced mixer combination.
7 citations
11 May 1997
TL;DR: In this article, a 3-terminal photo transistor optoelectronic mixer was demonstrated with a high conversion gain and the maximum obtained internal mixing efficiency was 113 dB and the mixing performance was measured as a function of the DC bias of the device and local oscillator power level.
Abstract: A high conversion gain 3-terminal heterojunction photo transistor optoelectronic mixer was demonstrated The maximum obtained internal mixing efficiency was 113 dB The mixing performance was measured as a function of the DC bias of the device and local oscillator power level A SPICE based large signal model was employed to simulate the device The main non-linear effects which contribute to the mixing process were the bias dependence of the dynamic emitter resistance, and the transition from the active to the saturation mode
5 citations
08 Sep 1997
TL;DR: In this article, the loss and noise figure of optical links transmitting microwave signals is dealt with, and it is shown that the noise figure is not proportional to the loss, and theoretically it can be less than the loss.
Abstract: Loss and noise figure of optical links transmitting microwave signals - e.g. for remote antennas in wireless communications - is dealt with. Conditions are rather general, including arbitrary matching conditions, shot noise and laser relative intensity noise. It is shown, that - alike passive microwave systems - noise figure is not proportional to the loss and theoretically it can be less than the loss. Optical power should be as low as possible - this limit being mainly determined by the required dynamic range of the system.
3 citations
03 Sep 1997
01 Sep 1997
08 Sep 1997
TL;DR: In this article, the authors describe techniques for the optical synthesis of microwave signals, focusing on optical heterodyne generation techniques and including recent results for a high spectral purity optical injection phase lock loop.
Abstract: Microwave signals can be generated by the photo-detection of multiple optical signals. This approach has potential for the generation of signals having characteristics not readily obtainable by other means, such as fast tuning over multi-octave ranges, low dispersion and non-linearity penalties in millimetre-wave over fibre transmission and compact millimetre-wave local oscillator generation. Obtaining the spectral purity required for practical applications is however a significant challenge. This paper describes techniques for the optical synthesis of microwave signals, focusing on optical heterodyne generation techniques and including recent results for a high spectral purity optical injection phase lock loop.