Abstract
An heterodyne interferoaeter is constructed with a sodulated laser diode (LD) in a Michelson interferoaeter. Phase drift of beat frequency with teiperature and its affection aechanis is discussed and a method elisinating the affection aentioned above is proposed. 1 . OPTICAL HETERODYNE INTERFEROMETER Optical frequency of laser diode can be linearly aodulated by an injection current. An optical heterodyne interferoseter is constructed with a modulated laser diode in a Michelson interferoseter. If a difference exists between two arms in the interferometer a optical beat frequency phenoaenon will be forRed. The beatfrequency signal can be detected with a photoelectric device. The output signal can be described by the following equation: 1g10[1+cos(2xfbt+t)J (1) and fb is given by fb 6f''8Lf. I C (2) Where f is the aaxiRua optical frequency variation value of wxiulated laser fb the beat frequency value fa the odulated signal frequency L the optical path difference between two aras in the interferoaeter C optical wave speed. 2. VARIATION OF BEAT FREQUENCY PHASE WITh TEMPERATURE It is well known that the optical frequency of a laser diode is affected by the tesperature (in the equation (1)) ay be changed with the variation of central wavelength of . odulated optical frequency. t aay be expressed in the for. : Li A242Ai t 2ir( ) (3) AiA2 The plus and ainus . arks in the equation above are corresponding to the upward
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