Abstract: An electromagnetic interference (EMI) prevention structure for a signal cable, which has at least one signal wire, a plurality of shielding wires, an intermediate layer located between the signal wire and the shielding wires, and an outer layer covering the shielding wires, includes a plurality of grounding areas formed on the outer layer of the signal cable by re-distributing or removing some parts of the structural mass of the outer layer at predetermined intervals or at predetermined positions. Whereby any noise voltage produced on the signal cable across any section thereof is effectively removed via one of the grounding areas that is closest to the section at where the noise voltage is produced.

Abstract: The present invention discloses a novel apparatus and method for stabilizing the frequency of a laser. To avoid the effect that a single-frequency absorption spectrum is easy to be affected by variations of laser power and the complexity to modulate a laser frequency, the present invention adopts at least two laser beams at different frequencies and obtains an error signal that is a difference in absorption spectrums of the laser beams. Since the error signal is a difference between two laser beams coming from an identical laser source, the variation of laser power could be eliminated. Furthermore, since the absorption spectrum is usually above hundreds of (MHz), the range of locked frequency of the present invention is large, and the laser frequency is not easily unlocked due to outside disturbance.