US 12,224,889 B2
Adaptive equalization filter and method for updating filter coefficients
Etsushi Yamazaki, Musashino (JP); Seiji Okamoto, Musashino (JP); Masanori Nakamura, Musashino (JP); Kengo Horikoshi, Musashino (JP); Takeo Sasai, Musashino (JP); and Yoshiaki Kisaka, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 18/038,194
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Nov. 25, 2020, PCT No. PCT/JP2020/043817
§ 371(c)(1), (2) Date May 22, 2023,
PCT Pub. No. WO2022/113204, PCT Pub. Date Jun. 2, 2022.
Prior Publication US 2023/0421420 A1, Dec. 28, 2023
Int. Cl. H04L 25/03 (2006.01); H04L 27/01 (2006.01)
CPC H04L 27/01 (2013.01) [H04L 25/03057 (2013.01)] 8 Claims
OG exemplary drawing
 
1. An adaptive equalization filter for an optical transmission system, the adaptive equalization filter comprising:
a main signal filter; and
a coefficient computator that updates a filter coefficient of the main signal filter,
wherein the coefficient computator includes:
a pre-stage filter and a post-stage filter that are connected in cascade, each having a sample of a main signal as an input;
a pre-stage coefficient computator that obtains a filter coefficient of the pre-stage filter by feedback control using a gradient method;
a post-stage coefficient computator that obtains a filter coefficient of the post-stage filter by feedforward control; and
a convolution computator that obtains the filter coefficient of the main signal filter by convolution computation of the filter coefficient of the pre-stage filter obtained by the pre-stage coefficient computator and the filter coefficient of the post-stage filter obtained by the post-stage coefficient computator.