Canobeam DT-100 Series Allowable Rainfall Rainfall is the most common weather phenomenon that affects outdoor wireless optical systems like the Canobeam. The attenuation due to rainfall can be estimated by the formulas below for the rainfall R and attenuation x. x = 4.9R0.63 (dB/km)(1) R : Rainfall per 10 minutes (mm) The criteria for rain strength are shown in Table 1 below. Table 1 Instantaneous Rain Strength (Units: mm) Instantaneous rain strength Rainfall per minute Ground conditions and other factors Particularly weak rain 0.02 or less The ground is hardly wet. Weak rain 0.02 to 0.05 The ground is wet, but no puddles are formed. Normal rain 0.05 to 0.25 Water puddles form on the ground, and the sound of rain can be heard. Strong rain 0.25 to 1.0 Puddles are formed all over the ground, and the sound of rain is loud. Particularly strong rain 1.0 or more Downpour with flooding of drainage systems and sewers. Figs. 1 and 2 show the allowable limits of rainfall when the signed error rate calculated from the formula (1) above is less than 1x10-9 or 1x10-6.   Fig.1 Allowable Rainfall for Signed Error Rate of 1x10-6   Fig.2 Allowable Rainfall for Signed Error Rate of 1x10-9