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Proceedings Paper

Oscillation frequency stabilization of a semiconductor laser under direct FSK by using the PEAK method
Author(s): Hiroki Nakamura; Kazuto Tamura; Kuniyuki Hosoya; Hiroyuki Nakano; Takashi Sato; Masashi Ohkawa; Takeo Maruyama; Minoru Shimba
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Paper Abstract

The oscillation frequency of a semiconductor laser must be stabilized in coherent optical communications systems that use such devices, because the frequency fluctuates according to variations in either temperature or injection current. Therefore, we set about the task of stabilizing it, using the Rb-D2 absorption line as an external frequency reference and negative feedback control. This method of stabilization requires the application of small sine wave modulation to obtain error signal by synchronous detection method. While the highly sensitive control ensures improved signal stability, frequency stability is deteriorated under direct FSK (Frequency Shift Keying), because the oscillation spectrum of a semiconductor laser is broadened. We, therefore, devised the `PEAK method', which improves frequency stability under direct FSK. The accurate measurement of frequency stability requires that the beat note between two stabilized laser frequencies, the signal and reference lasers, be measured. But beat note was sometimes outside the limits of our measuring equipment. The reference laser frequency was therefore adjusted by using the magneto-optical effect to control the beat note frequency within measurable limits of this work. We calculated the square root of the Allan variance to estimate the frequency stability, thereby confirming the effectiveness of PEAK method.

Paper Details

Date Published: 8 October 1998
PDF: 10 pages
Proc. SPIE 3415, Laser Diodes and Applications III, (8 October 1998); doi: 10.1117/12.326633
Show Author Affiliations
Hiroki Nakamura, Niigata Univ. (Japan)
Kazuto Tamura, Niigata Univ. (Japan)
Kuniyuki Hosoya, Niigata Univ. (Japan)
Hiroyuki Nakano, Niigata Univ. (Japan)
Takashi Sato, Niigata Univ. (Japan)
Masashi Ohkawa, Niigata Univ. (Japan)
Takeo Maruyama, Niigata Univ. (Japan)
Minoru Shimba, Tokyo Denki Univ. (Japan)

Published in SPIE Proceedings Vol. 3415:
Laser Diodes and Applications III
Pierre Galarneau, Editor(s)

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