| 主权项 |
1. A transducer for converting an acoustic signal into an electric signal, comprising:
a) a Fabry-Perot (FP) interferometer illuminated by a laser radiation with wavelength λ from a laser, a FP transmittance function being: T=1/(1+F sin2(2π·d·n/λ)), where F is a coefficient of finesse, d is a distance between two mirrors, and n is a refractive index of a medium in a space between the mirrors, wherein the medium is a gas or a liquid, wherein:
i. the distance d is constant and is off a resonance distance for a wavelength λ0; the mirrors themselves and the distance between the mirrors being non-movable and non-deformable;ii. the distance d corresponds to an operation point of the transducer, the operation point being achieved where a derivative of T is at a maximum or at a minimum value and a second derivative of T is equal to zero; andiii. the space receives an acoustic signal, changing the refractive index n of the medium in the space and thus influencing the laser radiation propagation; and b) a first laser radiation detector detecting an intensity of an outputted laser radiation influenced by the acoustic signal and generating an electric signal, wherein:
i. the electric signal is split into an AC (alternating current) and a DC (direct current) components by a separator; ii. the AC component of the electric signal is outputted, and the acoustic signal is recovered;
iii. the DC component enters a feedback loop connected to the laser; and iv. the DC component controls a drive current of the laser to irradiate wavelength λ being different from wavelength λ0, wherein λ corresponds to the operation point of the transducer where the second derivative of T is equal to zero. |
