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Proceedings Paper

Reduction of harmonic distortion in injection-locked semiconductor lasers
Author(s): Sheng Kwang Hwang; Jia Ming Liu; J. Kenton White
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Paper Abstract

Subcarrier multiplexed fiber-optic systems using direct modulation of semiconductor lasers have attracted much attention for analog and digital broadband services. Since analog modulation is adopted, the system performance can be degraded seriously due to inherent nonlinearities of semiconductor lasers. In this study, the injection-locking technique is applied to reduce the nonlinearities in directly modulated semiconductor lasers. In particular, the characteristics of the second harmonic distortion (SHD) and the third harmonic distortion (THD) are experimentally investigated. First of all, at a modulation frequency of 5 GHz, both SHD and THD in the injection-locked semiconductor laser are observed to reduce significantly and equally for a large range of modulation power, which are 15dB- and 23 dB-decreased, respectively. Second, at a fixed modulation power of 6 dBm, the reduction of SHD and THD is, however, found to vary with modulation frequency. The reduction of SHD is more substantial at around one-half of the relaxation resonance frequency of the free-running laser. The decrease in THD is more significant at around one-half and one-third of the relaxation resonance frequency of the free-running laser. Finally, how the reduction of harmonic distortions varies with the operational parameters of the laser system is also investigated. The results demonstrate the feasibility of the injection-locking method in reducing harmonic distortions for high-speed and high-power analog modulation applications.

Paper Details

Date Published: 20 December 2004
PDF: 10 pages
Proc. SPIE 5577, Photonics North 2004: Optical Components and Devices, (20 December 2004); doi: 10.1117/12.567459
Show Author Affiliations
Sheng Kwang Hwang, National Chung Cheng Univ. (Taiwan)
Jia Ming Liu, Univ. of California/Los Angeles (United States)
J. Kenton White, Bookham Technology (Canada)

Published in SPIE Proceedings Vol. 5577:
Photonics North 2004: Optical Components and Devices
John C. Armitage; Simon Fafard; Roger A. Lessard; George A. Lampropoulos, Editor(s)

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