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Frequency stabilization of a semiconductor laser under direct FSK modulation: The modulation method and evaluation of stability
Author(s) -
Watanabe Hiromichi,
Azuma Hideki,
Nakano Hiroyuki,
Sato Takashi,
Ohkawa Masashi,
Maruyama Takeo,
Shimba Minoru
Publication year - 1998
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/(sici)1520-6416(19981115)125:2<44::aid-eej6>3.0.co;2-o
Subject(s) - frequency shift keying , beat (acoustics) , laser , frequency modulation , modulation (music) , semiconductor laser theory , frequency deviation , stability (learning theory) , optical communication , materials science , acoustics , radio frequency , optics , physics , telecommunications , computer science , automatic frequency control , channel (broadcasting) , machine learning , demodulation
The frequency stability of a semiconductor laser deteriorated under direct frequency shift keying (FSK) when stabilization depended entirely upon an external frequency reference. Therefore, the PEAK method was devised for the purpose of improving frequency stability. This method requires two distinct frequency components and, therefore, will not work effectively in a communications system that produces a succession of identical frequencies, as does the FSK method on occasion. This paper, then, explains the results of our comparative analysis of the two modulation methods. The evaluation of frequency stability requires us to use a beat note between two stabilized laser beams, referred to here, as “signal” and “reference,” lasers. The reference laser is stabilized by a method that takes advantage of the magneto‐optical effect. This laser restrains the tendency of the beat note frequency to broaden in other stabilization methods, and even makes it possible to predetermine the beat frequency to be employed. The improvement in frequency stability obtained is about one order of magnitude. © 1998 Scripta Technica, Electr Eng Jpn, 125(2): 44–51, 1998