Patent Number: 7,711,268

Title: Passive optical network system and ranging system thereof

Abstract: A station-side communication device connected to subscriber-side communication devices via an optical combining device; sending, to the subscriber-side communication devices, a distance measurement request signal; computing transmission delay times of optical signals from the individual subscriber-side communication devices by receiving distance measurement signals, and including: a threshold control part identifying the level of distance measurement signals; a signal detection part detecting breaks in the distance measurement signals from the threshold control part; a transmission granting part determining the timing at which transmission of optical signals is granted, and a reset timing generation part that, there is notification of detection of a break in the distance measurement signal from the signal detection part while it is being notified that distance measurement is carried out to and from the subscriber-side communication devices from the transmission granting part, sends a reset signal indicating that the voltage level is reset to the threshold control part.

Inventors: Kazawa; Tohru (Kokubunji, JP), Ohira; Masaki (Yokohama, JP), Yajima; Yusuke (Fujisawa, JP), Sakamoto; Norihiro (Yokohama, JP)

Assignee: Hitachi, Ltd.

International Classification: H04J 14/00 (20060101)

Expiration Date: 5/04/12018