Method and apparatus for bit error rate analysis

[Subject] It is the method and equipment which determine a bit error rate. [Solution means] During the predetermined period, the method of the present invention acquires a data signal in the acquisition part of test apparatus, and consists of steps (310) which memorize a data signal in the memory of test apparatus. A clock signal is recovered from the memorized data signal (315), and the data signal memorized according to it is sliced by two or more data segments of predetermined length. Each of a data segment is synchronized by a frame or the predetermined pattern (335) (662), and determines the bit error rate (345).