Patent ID: 7035553

Claim:
An optical-signal autocorrelation-bit-error detection apparatus using an optical branch system, comprising: optical branch means for branching an optical signal to be measured modulated by a pulse signal and outputting branched optical signals as first and second optical pulse signals; first light-to-electricity conversion means for converting the first optical pulse signal supplied from said optical branch means into a first electrical signal and outputting the first electrical signal; second light-to-electricity conversion means for converting the second optical pulse signal supplied from said optical branch means into a second electrical signal and outputting the second electrical signal; first decision means for outputting a reference pulse signal in accordance with a comparison result between the voltage of the first electrical signal supplied from said first light-to-electricity conversion means and a reference-signal generation voltage set to an approximate median of the amplitude of said first electrical signal; second decision means for outputting a measuring pulse signal in accordance with a comparison result between the voltage of the second electrical signal supplied from said second light-to-electricity conversion means and a noise detection voltage set to an optional level slid from an approximate median of the amplitude of said second electrical signal to a mark side or space side; and bit error detection means for detecting an autocorrelation bit error of said optical signal to be measured in accordance with a comparison result between the reference pulse signal supplied from said first decision means and the measuring pulse signal supplied from said second decision means, wherein said optical branch means outputs said first and second optical pulse signals by setting magnitudes of the signals to m:n (m>n) where m corresponds to the magnitude of said second optical pulse signal and n corresponds to the magnitude of the first optical pulse signal so that the magnitude of the second optical pulse signal is greater than that of the first optical pulse signal when optically branching said optical signal to be measured into said first optical pulse signal at the reference side and into said second optical pulse signal at the noise detection side.