Patent ID: 7725031

Claim:
An optical communication system comprising: a station-side communication device; a plurality of subscriber-side communication devices; and an optical combining device connecting the plurality of subscriber-side communication devices to the station-side communication device, wherein: the station-side communication device transmits to said plurality of subscriber-side devices a distance measurement request signal for measuring distances from said station-side communication device to respective said plural subscriber-side communication devices, receives distance measurement signals which are replies to said distance measurement request signal from said plurality of subscriber-side communication devices, and computes transmission delay times of optical signals from said individual subscriber-side communication devices, said station-side communication device comprising: a threshold control part identifying voltage levels of said distance measurement signals converted from optical signals into electrical signals; a signal detection part identifying breaks in said distance measurement signals from said threshold control part; a transmission granting part determining timing at which transmission of optical signals from said subscriber-side communication devices is granted; and a reset timing generation part sending said threshold control part a plurality of reset signals while having a notification from said transmission granting part that the distance measurements are carried out between said station-side communication device and said subscriber-side communication devices, in order to reset the voltage levels; and said subscriber-side communication devices return a plurality of said distance measurement signals to said station-side communication device, when receiving said distance measurement request signals from said station-side communication device.