Showing papers by "Alwyn J. Seeds published in 2009"

Homodyne coherent receiver with phase locking to orthogonal-polarisation pilot carrier by optical injection phase lock loop

Abstract: Phase locking to an orthogonal-polarisation pilot by an optical injection phase lock loop is demonstrated for the first time, enabling homodyne demodulation of 10Gb/s BPSK with performance close to the LO-ASE limit (OSNR=6dB/0.1nm; BER=10−3).

New applications for microwave photonics

Abstract: A photonic technique for generating high-purity millimetre-wave or terahertz signals based on heterodyne of two phase-locked optical sources is described. Technology requirements and potential applications are discussed.

Photonic-enabled microwave and terahertz communication systems

Abstract: An optical heterodyne technique for generating millimetre-wave and THz carriers with high spectral purity and low phase noise is described, for application to Gb/s wireless communications systems. Progress on key integrated optical components is reported.

Demonstration of an indoor real-time location system with optical fibre backbone

Abstract: We report the first demontration of an indoor realtime location system, based on an optical fibre backbone, using an active RFID tag emitting 83.5 MHz wide linear FM chirp in the 2.4 GHz ISM band.

Technologies for radio over fibre systems

Abstract: In this paper we present some of the latest technologies for radio over fibre systems developed in the authors' own laboratory and by other international groups.

Phase-locked Optical Signal Recovery

Abstract: : Phase-locked receivers have long been used for the recovery of signals in low signal to noise ratio (SNR) environments, such as space applications. A loop for use with semiconductor laser generated signals would require a bandwidth of >500 MHz for low phase error variance (<0.01 rad2) tracking, constraining the propagation delay to <0.3 ns. Since this requires an equivalent path length of <100 mm, conventional realizations in optical fiber technology are not possible, requiring special micro-optical solutions. An alternative technique is to use optical injection locking. This avoids loop propagation limitations, but stable locking ranges are typically <1 GHz, requiring precision (<10 mK) control of the receiver laser and continuous adjustment to track drift in the incoming signal. At University College London (UCL), we have developed a technique that overcomes the limitations described above-the Optical Injection Phase Lock Loop (OIPLL) in which a narrow bandwidth optical phase lock loop (OPLL) is used to control the free-running frequency of an optically injection locked laser to compensate for thermal drift, drift in the incoming signal and low-frequency noise. If successful this would enable low SNR optical signals to be recovered without the need for constant skilled adjustment of the receiver system. For the feasibility study we propose to investigate two possible detection schemes. The first is an homodyne OIPLL. Although this appears simple in principle there are significant challenges in implementation. The second scheme is based on heterodyne detection, with the heterodyne frequency chosen to be remote from data modulation interference. In this approach, the incoming signal passes through a modulator, where it is sinusoidally intensity modulated at microwave frequency by the offset source. The slave laser is injection locked to one of these side frequencies through an optical circulator.