Systems and methods for clip prevention in a CATV network

Patent metadata

Field	Value
Publication number	US-9531474-B2
Application number	US-201514625601-A
Country	US
Kind code	B2
Filing date	Feb 18, 2015
Priority date	Apr 21, 2014
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

Systems and methods for preventing laser clipping in a CATV network.

First claim

The invention claimed is:

1. A device for relaying content between a head end and a plurality of subscribers remote from the head end, the device comprising:
(a) at least one input capable of detecting an upstream signal;
(b) an optical transmitter that outputs an optical signal using said upstream signal as an input to produce a driving signal for driving said optical transmitter, where said optical transmitter operates in burst mode;
(c) a controller capable of monitoring power levels of one or more upstream signals over a time interval to determine whether clipping occurs and, responsive to a threshold number of clipping events occurring within said time interval reduce clipping of said transmitter, the controller operable to reduce the clipping by at least one of (i) determining based on the power levels monitored over the time interval an amount to attenuate the driving signal and attenuating the driving signal of said transmitter by the amount determined or (ii) varying a bias of said transmitter to cause a slower a rise time of the transmitter,
wherein the reduction in clipping enables the burst mode to inhibit interference with an upstream spectrum to be transmitted.

2. The device of claim 1 located in an ONU.

3. The device of claim 1 located in an active splitter.

4. The device of claim 1 where said controller monitors said transmitter to detect clipping and selectively reduces said clipping when detected clipping exceeds a threshold.

5. The device of claim 1 including an amplifier between the at least one input and the optical transmitter, where the controller modulates the gain of the amplifier based on the modulation of the bias of the transmitter.

6. The device of claim 5 where the controller delays the signal from the amplifier relative to a turn-on time of the transmitter.

7. The device of claim 6 where the controller applies a faster rise time to the signal from the amplifier relative to the rise time of the transmitter.

8. The device of claim 7 where the rise time of the amplifier is the fastest rise time achievable by said amplifier.

9. The device of claim 1 where the controller delays the signal to the transmitter relative to a turn-on time of the transmitter.

10. A method for relaying content between a head end and a plurality of subscribers remote from the head end, the method comprising:
(a) detecting a radio frequency (RF) signal;
(b) transmitting an optical signal using said RF signal as an input for driving a laser;
(c) monitoring power levels of one or more upstream signals over a time interval to determine whether clipping occurs; and
(d) responsive to a threshold number of clipping events occurring within said time interval, reducing clipping of said laser by at least one of (i) modulating said RF signal to said laser by attenuating the RF signal input or (ii) modulating a bias of said laser to cause a slower rise time of the laser.

11. The method of claim 10 including the step of reducing said clipping when detected clipping exceeds a threshold.

12. The method of claim 10 where the RF signal input to the laser is delayed relative to a turn-on time of the laser.

Assignees

• Arris Entpr Inc

Inventors

• Schemmann Marcel F
• Mutalik Venkatesh G

Classifications

• H04J14/0232

  for downstream transmission · CPC title

• H04B10/075

  using an in-service signal (H04B10/071 takes precedence) · CPC title

• H04N7/22

  Adaptations for optical transmission · CPC title

• H04B10/2575

  Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier · CPC title

• H04B10/50

  Transmitters · CPC title