In two-arms interferometers, spurious beams are often cause of instabilities. Resulting multiple-beam interference limit the probe sensitivity. Optical components are usually added to spatially shift or to suppress these `spurious beams' returning inside the interferometer. Experimentally, we have shown that the so-called `spurious beams' returning towards the laser can be successfully used to obtain stable interference. So, we have developed new structures of interferometers based on the reflection of a returning beam on the high-quality front mirror of He-Ne laser. The new structures present several advantages compared with classical interferometers (Michelson or Mach-Zehnder, e.g.). They are more simple and, at least, the same sensitivity has been measured. Alignment is simplified and power balancing is very easy.