US 7,542,678 B2
Method and apparatus for a supervisory channel in a WDM fiber-optic communication system
Lutz Raddatz, Nürnberg (Germany)
Assigned to Alcatel-Lucent USA Inc., Murray Hill, N.J. (US)
Filed on Dec. 30, 2004, as Appl. No. 11/27,847.
Prior Publication US 2006/0147205 A1, Jul. 06, 2006
Int. Cl. H04J 12/02 (2006.01); H04B 10/08 (2006.01)
U.S. Cl. 398—83  [398/30; 398/31; 398/32; 398/82; 398/186; 398/187; 398/188] 21 Claims
OG exemplary drawing
 
10. An Optical Add-Drop Multiplexer (OADM) of a multi-node wavelength division multiplexing (WDM) fiber-optic communication system, comprising:
a controller including a modulator and a demodulator of a supervisory channel;
a demultiplexer (DMUX) and a multiplexer (MUX) of transmitted WDM channels where at least one of the demultiplexed WDM channels comprises a variable optical attenuator wherein attenuation is controlled by said modulator in a manner facilitating equalization of an optical power between demultiplexed WDM channels;
an input optical coupler having a tap coupled to said demodulator; and
an output optical amplifier coupled to an output of the MUX;
wherein the modulator modulates said variable optical attenuator with a sum of a modulating signal of the supervisory channel and a setting for a power equalizing attenuation of an optical power between the demultiplexed WDM channels.