IEC 61280-2-8:2003 specifies two main methods for the determination of low BER values by making accelerated measurements. These include the variable decision threshold method (Clause 4) and the variable optical threshold method (Clause 5). In addition, a third method, the sinusoidal interference method, is described in Annex B. Key Words: BER values, variable decision threshold method, variable optical threshold method, sinusoidal interference method