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8 October 1998 Oscillation frequency stabilization of a semiconductor laser under direct FSK by using the PEAK method
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Proceedings Volume 3415, Laser Diodes and Applications III; (1998) https://doi.org/10.1117/12.326633
Event: Lasers and Materials in Industry and Opto-Contact Workshop, 1998, Quebec, Canada
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.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hiroki Nakamura, Kazuto Tamura, Kuniyuki Hosoya, Hiroyuki Nakano, Takashi Sato, Masashi Ohkawa, Takeo Maruyama, and Minoru Shimba "Oscillation frequency stabilization of a semiconductor laser under direct FSK by using the PEAK method", Proc. SPIE 3415, Laser Diodes and Applications III, (8 October 1998); https://doi.org/10.1117/12.326633
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