| 摘要 |
PCT No. PCT/GB94/00675 Sec. 371 Date Jan. 16, 1996 Sec. 102(e) Date Jan. 16, 1996 PCT Filed Mar. 30, 1994 PCT Pub. No. WO94/23507 PCT Pub. Date Oct. 13, 1994An optical beam having a high radio-frequency modulation is generated by generating a lower frequency modulation, using it to control the optical output of a laser and further modulating the optical output in an optical modulator by a control signal having another lower frequency modulation generated. Either or both of the lower frequency modulations also carries an information containing modulation. the effect of the optical modulator is to up-convert the modulation carried by the optical beam by the modulation frequency of the control signal. The optical modulator may be a Mach-Zehnder interferometer. The non-linearity of such a modulator with respect to its control input may be exploited by selecting the amplitude of the control signal such that the optical output is up-converted by an integer multiple of the initial modulation frequency. These methods avoid the need to apply the high frequency modulation to either the laser input or the control input directly. |
