| 摘要 |
<p>A method and apparatus for generating a plurality of electromagnetic signals, primarily optical signals, having linewidths centred on frequencies fixed relatively to a reference frequency. The apparatus comprises a reference frequency signal source such as a gas laser (1) which generates a reference signal having a frequency fP. This reference signal is fed to a leading one (3) of a plurality of optical fibre ring lasers (3, 11, 16) connected together in series by optical fibres (6, 12). The characteristics of the injected signal and the form of the waveguide ring (5) defined by the ring laser (3) is such that stimulated Brillouin scattering occurs in the waveguide ring to generate a scattered signal with a frequency fP-fA travelling in an opposite direction to the injected signal. This scattered signal is passed by the optical fibres (6) via an isolation device (7) to the next ring laser (11) in series. Directional couplers (2, 10, 15) are provided to guide the injected signals, including the reference signal to respective output ports (9, 14, 17). The stimulated Brillouin scattering effect causes each scattered wave to be offset from the corresponding injected wave by a fixed frequency (fA).</p> |
