Detecting collisions on multipoint shared optical media
View Patent ↗A system, and methods for detecting collisions on multipoint shared optical media, comprising an optical receiver, clock phase detector, clock recovery circuit, and a Passive Optical Network (PON) that transmits optical signals wherein the PON, the clock recovery circuit, and the clock phase detector are communicably coupled to the optical receiver, detecting of the collision is determined by a distortion of transition times of the optical signals at the optical receiver.
1. A system for detecting a collision on multipoint shared optical media, comprising:
an optical receiver;
a clock phase detector;
a clock recovery circuit; and
a Passive Optical Network (PON) that transmits optical signals;
wherein the PON, the clock recovery circuit and the clock phase detector are communicably coupled to the optical receiver;
wherein the detection of the collision is determined by a distortion of transition times of the optical signals at the optical receiver;
wherein the clock phase detector detects edge transitions of the optical signals and expects the edge transitions to conform to a nominal data period;
wherein if the edge transitions are not at the nominal data period, the clock phase detector filters the edge transitions; and
wherein the clock phase detector stores the filtered edge transitions.
2. The system of claim 1 , wherein the PON comprises a plurality of Optical Network Terminal (ONT) unit.
3. The system of claim 2 , wherein the ONT units transmit the optical signals.
4. The system of claim 3 , wherein a timing variability between the ONT units occurs due to their differing locations on the PON.
5. The system of claim 4 , wherein the variability will result in the distortion of transition times of the optical signals at the optical receiver if the ONT units are transmitting the optical signals simultaneously.
6. The system of claim 1 , wherein an output of the optical receiver reveals edge transitions that do not conform to the nominal data period expected when only one ONT unit is transmitting.
7. The system of claim 6 , wherein the nominal data period is around 800 ps.
8. The system of claim 6 , wherein the edge transitions are monitored and compared to an expected transition interval.
9. The system of claim 8 , wherein the edge transitions occurring outside of the expected transition interval indicate a presence of another transmitting ONT unit.
10. The system of claim 9 , wherein the presence of another transmitting ONT unit reveals a presence of an insubordinate ONT unit.
11. The system of claim 1 , wherein the clock recovery circuit utilizing clock phase alignment techniques detects distortion of transition times of the optical signals.
12. The system of claim 1 , wherein the clock phase detector triggers an alarm.
13. A method for detecting a collision on multipoint shared optical media, comprising:
transmitting, by a plurality of Optical Network Terminal (ONT) units at different locations, optical signals;
determining a timing variability between the ONT units due to the different locations;
wherein the variability will result in a distortion of transition times of the optical signals at an optical receiver if the ONT units are transmitting the optical signals simultaneously; detecting the collision by determining the distortion of the transmission times;
detecting, by a clock phase detector, edge transitions of the optical signals and expecting the edge transitions to conform to a nominal data period;
if the edge transitions are not at the nominal data period, filtering, by the clock phase detector, the edge transitions; and
storing, by the clock phase detector, the filtered edge transitions.
14. The method of claim 13 , wherein an output of the optical receiver reveals edge transitions that do not conform to a nominal 800 ps data period expected when only one ONT unit is transmitting.
15. The method of claim 14 , wherein the edge transitions:
are monitored and compared to an expected transition interval;
occurring outside of the expected transition interval indicate a presence of another transmitting ONT unit; and
wherein the presence of another transmitting ONT unit reveals a presence of an insubordinate ONT unit.
16. A method for detecting a collision on multipoint shared optical media, comprising:
detecting the collision when a clock recovery circuit detects distortion of transition times of optical signals;
detecting, by a clock phase detector, edge transitions of the optical signals and expecting the edge transitions to conform to a nominal data period;
if the edge transitions are not at the nominal data period, filtering, by the clock phase detector, the edge transitions; and
storing, by the clock phase detector, the filtered edge transitions;
if the edge transitions are not at the nominal data period, triggering an alarm by the clock phase detector.