US 9,813,157 B2
Mitigation of multi-path interference from quasi-single-mode fiber using hybrid span configuration and digital signal processing
Shaoling Zhang, Princeton, NJ (US); Fatih Yaman, Monmouth Junction, NJ (US); Yue-Kai Huang, Princeton, NJ (US); Ezra Ip, Plainsboro, NJ (US); and Yoshihisa Inada, Tokyo (JP)
Assigned to NEC Corporation, Tokyo (JP)
Filed by NEC Laboratories America, Inc., Princeton, NJ (US)
Filed on Mar. 6, 2016, as Appl. No. 15/62,179.
Claims priority of provisional application 62/129,158, filed on Mar. 6, 2015.
Prior Publication US 2016/0261344 A1, Sep. 8, 2016
Int. Cl. H04B 10/00 (2013.01); H04B 10/2581 (2013.01); H04L 25/03 (2006.01); H04B 10/2543 (2013.01); H04B 10/69 (2013.01)
CPC H04B 10/2581 (2013.01) [H04B 10/2543 (2013.01); H04B 10/6971 (2013.01); H04L 25/03885 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A method for mitigating multi-path interference (MPI) in a long-haul optical communications system comprising the steps of:
configuring each fiber span of the system with a hybrid span of fiber, said hybrid span including a length of quasi-single-mode fiber (QSM) and a length of single-mode fiber (SMF) such that the overall fiber nonlinearity and MPI is reduced by at least half as compared to a link of QSM fiber over the same distance;
configuring the system to include an Asymmetric Least-Mean Square (ALMS) equalizer wherein the ALMS equalizer operates to shift its center tap towards the right if a higher mode transmits slower than a fundamental mode else the center tap is shifted to the left such that the number of equalizer taps employed is reduced by at least ⅓ as compared to a standard Decision-Directed Least-Mean Square (DD-LMS) equalizer; and
introducing a low-baudrate sub-banding signal into the system such that MPI is effectively compensated and a number of decision-directed least-mean square (DD-LMS) equalizer taps employed is reduced as compared with a high-baudrate signal.