Photocount statistics of amplitude-modulated radiation transmitted by a multimode fiber waveguide

The distribution of the probability of photocounts was determined for amplitude-modulated radiation transmitted by a multimode fiber waveguide. A dependence of the variance of the number of photocounts on the average power of the radiation coupled into the fiber waveguide was observed. This effect was attributed to the generation of sound at the frequency of modulation of the optical radiation due to electrostriction and thermal mechanisms. A formula describing the dependence of the variance of the number of photocounts on the average power was derived. A study was also made of the dependences of this characteristic on the frequency and depth of modulation of the radiation.