Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-09-22
2001-05-29
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C370S351000
Reexamination Certificate
active
06239887
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method to determine a predefined switching moment of a switch as and a line terminator, a control network unit and a network unit realizing such a method and a tree-like optical network including such a line terminator, such a control means or such a network unit.
Such a line terminator, a control network unit and such a network unit are already known in the art, e.g. from “the published European patent application, published at 26.03.1997, with the title “Arrangement for amplifying and combining optical signals, and method for upstream transmission realized therewith”, with publication number EP 0 765 045 A1”. Therein, an optical amplifier combiner arrangement is described in a tree-like optical network. The tree-like optical network consists of the cascade connection of dedicated branches, the combiner arrangement and a common branch. The arrangement is coupled between a plurality of optical network units and an optical line terminator via one of the dedicated branches and the common branch respectively. The tree-like optical network enables upstream transmission of information signals from the optical network units to the optical line terminator. The optical amplifier combiner arrangement includes for each branch of the dedicated branches
an optical amplifier to amplify an upstream information signal with a gain value and to thereby generate an amplified information signal with a predetermined power level;
an optical switch on/off coupled between the optical amplifier and an optical combiner to pass the amplified information signal when the information signal is present and to interrupt the branch when the information signal is not present.
The optical combiner is included in the arrangement to combine all amplified information signals according to a multiple access technique for application to the optical line terminator.
In order to explain the object of the invention a possible way of determining the switching moment of each switch is explained in this further paragraph. The above mentioned document describes in column 2 from line 11 to line 25 a network which uses for the upstream transmission a time division multiple access technique. This technique makes use of special grant information in order to indicate to a network unit the application of an upstream timeslot. When a network unit receives from the line terminator a grant, it will wait for a certain delay before transmitting an upstream information signal. These delays are determined during a so called ranging procedure whereby an identical virtual distance is introduced for each network unit. This ranging procedure assures that when looking to the multiple access principle, each information signal transmitted by the different network units, arrives at the optical combiner in order to use the common branch, the one after the other following its dedicated timeslot. When each network unit introduces a correct delay there will be no collision at the optical combiner between the upstream information signals.
Just before being combined, each information signal has passed the switch of its dedicated branch. The switch passed the information signal when it was present and interrupted the branch afterwards when the information signal was not present anymore.
The control of the switches is realized by
a) capturing downstream grant information by a control network unit which is coupled between the line terminator and the switch; and
b) determining the approximated switching moment by the control network unit based upon the downstream grant information.
With this special grant information the moment of transmitting upstream information for each network unit of each branch is determined and, associated therewith, also the moment of switching on and off for each switch of each dedicated branch in order to pass the transmitted upstream information.
However, due to the difference in distance of the control network terminator to the combiner and the different switches to the combiner, an uncertainty on the switching moment remains. Indeed, the control optical network terminator is enabled by capturing the special grant information to determine the moment when the information signal arrives at the combiner but the moment when the information signal arrives at the switch i.e. the switching moment of the switch is with this method only approximated due to this difference in optical delay and electrical delay.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method to determine a switching moment of a switch such as the above known method but which has not the above drawback, i.e. a method which determines a switching moment with a better accuracy.
According to the invention, this object is achieved by means of the method to determine a switching moment as described in claim
1
, and by means of the line terminator, the control network unit and the network unit which are realizing this method as described in claim
4
, claim
6
and claim
8
, respectively and the tree-like optical network including such a line terminator, such a control means and such a network unit as described in claim
10
.
Indeed, the present invention addresses this problem by:
c) upstream transmitting by one of the plurality of network units coupled to the dedicated branch a predefined bit pattern similar to the information signal, and when the predefined bit pattern is passing through the switch, thereby truncating the predefined bit pattern and providing a truncated bit pattern related to the approximated switching moment; and
d) detecting by the line terminator reception of the truncated bit pattern; and
e) determining by the line terminator upon reception of the truncated bit pattern a measure of how much the predefined bit pattern is truncated and providing thereby a truncation measure; and
f) calculating in function of the truncation measure a calibration value for the approximated switching moment; and
g) providing the calibration value to the control network unit in order to determine the switching moment in function of the calibration value and the approximated switching moment.
It has to be remarked that the transmission of a predefined bit pattern can be executed at predefined regular moments which are known by the different network units and by the line terminator. However, another way of initiating the step of upstream transmitting of a predefined bit pattern by a network unit is upon receiving from the line terminator a calibration control signal e.g. a specific grant downstream transmitted in order to give a particular network unit the permission to use an upstream timeslot for the transmission of the predefined bit pattern. This is described in the method of claim
2
, the line terminator of claim
5
and the network unit of claim
9
.
A possible way to determine by the line terminator a measure of how much the predefined bit pattern is truncated is e.g. determining the length of the truncated bit pattern and comparing this length with a predefined length of the predefined bit pattern. However another implementation of the present invention is described in claim
3
. Indeed, by:
determining by the line terminator upon detection of the truncated bit pattern a receiving time of the truncated bit pattern; and
defining a receiving time reference by determining the receiving time of the truncated bit pattern at the line terminator in the event when the switch is continuously open whereby the truncated bit pattern substantially equals to the predefined bit pattern; and that the calibration value is calculated in function of the receiving time and the receiving time reference.
A further possible implementation is described in claim
7
. Indeed, a possible way to realize the control network unit is according to a distributed way. This means that each switch has its own control network unit which must be able to perform the requested functions e.g. capturing grant information and determining the switching moment of its associated switch according to the received c
Martin Claire
Slabbinck Hans
Van de Voorde Ingrid Zulma Benoit
Vetter Peter Johannes
Alcatel
Lieu Vu
Pascal Leslie
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Method to determine a switching moment and a line... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method to determine a switching moment and a line..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method to determine a switching moment and a line... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484915