Patent ID: 6239887
Filing Date: 2001-05-29
Classification: H04J,H04Q

Abstract:
A method to determine a switching moment (Ti) of a switch (SWi) which is coupled to an optical combiner (OC) of a tree-like optical network, said optical combiner (OC) being provided in order to enable multiple access of information signals (IN1, . . . , INi, . . . INn) being upstream transmitted from a plurality of network units (NU1, NU1', NU1"", . . . , NUi, . . . , NUn) to a line terminator (LT) via the cascade connection of dedicated branches (B1, . . . , Bi, . . . , Bn), said optical combiner (OC) and a common branch (BC), said switch (SWi) being provided to pass one of said information signals (INi) transmitted via one of said dedicated branches (Bi) at an approximated switching moment (APP-Ti) in the event when said information signal (INi) is present and to interrupt said branch (Bi) when said information signal (INi) is not present, said method includes the steps of:a) capturing downstream grant information by a control network unit (CTRL-NU) being coupled between said switch (SWi) and said line terminator (LT); andb) determining said approximated switching moment (APP-Ti) by said control network unit (CTRL-NU) based upon said downstream grant information, characterized in that said method further includes the steps of:c) upstream transmitting by one of said plurality of network units (NUi) coupled to said one dedicated branch (Bi) a predefined bit pattern (PAT) similar to said information signal (INi), and in the event when said predefined bit pattern (PAT) is passing through said switch (SWi), thereby truncating said predefined bit pattern (PAT) and providing a truncated bit pattern (PAT-TR) related to said approximated switching moment (APP-Ti); andd) detecting by said line terminator (LT) reception of said truncated bit pattern (PAT-TR); ande) determining by said line terminator (LT) upon reception of said truncated bit pattern (TR-PAT) a measure of how much said predefined bit pattern (PAT) is truncated and providing thereby a truncation measure (TR); andf) calculating in function of said truncation measure (TR) a calibration value (CAL-SWI) for said switching moment (APP-Ti);g) providing said calibration value (CAL-SWi) to said control network unit (CTRL-NU) in order to determine said switching moment (Ti) in function of said calibration value (CAL-SWi) and said approximated switching moment (APP-Ti).