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Proceedings Paper

Microwave signal generation using an erbium-doped external cavity laser
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Paper Abstract

The increasing demand for broadband mobile communications has generated interest in exploring new frequency bands and modifying network structures. In such systems, photonic technologies can bring both cost reduction as well as an increase in performance, mainly due to the low-loss properties of optical fibers. An optical source capable of producing tunable, high-quality microwave/mm-wave signals would be of great interest not only in such communications systems, but in fiber sensors and numerous other applications as well. One potentially cost-effective method to fabricate such a system is via optical heterodyning. In this approach, the difficulties in generating a high-quality signal are two-fold. The first issue is in maintaining a specific frequency difference (i.e. microwave signal) between the lasers for an extended period of time. The second is in narrowing the inherent linewidth of the laser from the MHz values typically produced by conventional semiconductor lasers, down to values practical for a communications system. Both of the above requirements are facilitated by the newly developed doped-fiber, external cavity laser (DFECL), which offers relatively stable single-longitudinal-mode operation in addition to narrow linewidth operation. This paper will demonstrate frequency locking of a DFECL using a delay-line discriminator. The RF linewidth, initially 10-15MHz, is reduced to levels conducive to optical PLL locking. Optical power levels are approximately -3 dBm and unamplified microwave power output levels are typically -35 dBm, depending on photodetector responsivity. Carrier-to-noise ratios are generally 40-45 dB. The physical mechanisms underlying the observed laser dynamics are discussed, including laser-to-fiber alignment and thermal fluctuations.

Paper Details

Date Published: 11 August 2008
PDF: 7 pages
Proc. SPIE 7099, Photonics North 2008, 70990O (11 August 2008); doi: 10.1117/12.805321
Show Author Affiliations
Howard Rideout, Communications Research Ctr. (Canada)
Runnan Liu, École Polytechnique de Montréal (Canada)
Joe Seregelyi, Communications Research Ctr. (Canada)
Stéphane Paquet, Communications Research Ctr. (Canada)
Raman Kashyap, École Polytechnique de Montréal (Canada)

Published in SPIE Proceedings Vol. 7099:
Photonics North 2008
Réal Vallée; Michel Piché; Peter Mascher; Pavel Cheben; Daniel Côté; Sophie LaRochelle; Henry P. Schriemer; Jacques Albert; Tsuneyuki Ozaki, Editor(s)

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