| 摘要 |
<p>FIBER OPTIC FREQUENCY SHIFTER This invention relates to fiber optic frequency shifters for producing optical signals of a desired frequency range for input to a device such as an optical rotation sensing system. The rotating birefringence is created in a length of fiber optic material, which has the effect of a rotating half-wave plate upon an input optical signal. The length of fiber optic material may have a jacket of either an electrostrictive or a magnetostrictive material formed thereon such that application of an appropriate field to the jacket compresses the enclosed fiber to induce birefringence therein by means of the photoelastic effect. A half-coupler having a block of electro-optically active birefringent material adjacent the interaction region combined with an electrode configuration and circuitry for producing a rotating electric field in the block also produces a rotating half-wave plate frequency shifter. The evanescent field of light propagating in the optical fiber interacts with the rotating birefringence and experiences a frequency shift. The invention also includes feedback circuitry for processing the optical output of fiber optic rotating half-wave plates to maintain the intensity of components in the output signal having the carrier frequency below a threshold value.</p> |
