US 7,511,883 B2
Optical amplifying method, optical amplifying apparatus, and optical amplified transmission system using the apparatus
Ryo Kawahara, Tokyo (Japan); Masaru Fukushima, Tokyo (Japan); Nobuyuki Kagi, Tokyo (Japan); and Kensaku Sekiya, Tokyo (Japan)
Assigned to The Furukawa Electric Co., Ltd., Tokyo (Japan)
Filed on Oct. 31, 2007, as Appl. No. 11/931,944.
Application 11/931944 is a division of application No. 10/775103, filed on Feb. 11, 2004, granted, now 7,333,262.
Claims priority of application No. 2003-034135 (JP), filed on Feb. 12, 2003; and application No. 2003-397952 (JP), filed on Nov. 27, 2003.
Prior Publication US 2008/0068700 A1, Mar. 20, 2008
Int. Cl. H04B 10/17 (2006.01)
U.S. Cl. 359—341.41 8 Claims
OG exemplary drawing
 
3. An optical amplifier connected to an optical transmission line, comprising;
means for detecting an optical input and output power of said optical amplifier;
means for applying a logarithmic transformation to the detected optical input and output power to obtain a logarithmic transformed optical input and output power;
means for obtaining a difference between a target gain and a measured gain of said optical amplifier obtained based on the logarithmic transformed optical input and output power to produce an error signal;
means for applying said error signal to each of a proportional calculation and an integral calculation to create respective proportional arid integral control signals;
means for adding the proportional and integral control signals to create a drive current of at least one pump laser diode provided in said optical amplifier;
means for controlling the gain of said optical amplifier with the drive current; and
means for adjusting a control parameter of the proportional calculator in response to the logarithmic transformed optical output power, said control parameter being a proportional constant by which said error signal is multiplied to form said proportional control signal, said proportional constant being represented by a function logarithmic transformed of the optical output power as a result of the adjusting the control parameter in response to the logarithmic transformed optical output power whereby said proportional constant is increased according to an increase of said logarithmic transformed optical output power.