US 11,811,459 B1
In-service characterization of nonlinear interference on a per-span basis
Yinqing Pei, Kanata (CA); Andrew D. Shiner, Ottawa (CA); Alex W. MacKay, Ottawa (CA); David W. Boertjes, Nepean (CA); and Fangyuan Zhang, Kanata (CA)
Assigned to Ciena Corporation, Hanover, MD (US)
Filed by Ciena Corporation, Hanover, MD (US)
Filed on Jul. 19, 2022, as Appl. No. 17/868,170.
Int. Cl. H04B 10/58 (2013.01); H04B 10/67 (2013.01); H04B 10/073 (2013.01)
CPC H04B 10/58 (2013.01) [H04B 10/0731 (2013.01); H04B 10/674 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method of measuring nonlinear interference (NLI) on a per-span basis in an optical system with a plurality of spans, the method comprising steps of:
varying power on a span under test of the plurality of spans based on one or more of
(a) a first and a second variable optical attenuator (VOA) with the first VOA located before and the second VOA located after a line fiber associated with the span under test, where the VOA is used for varying power and the second VOA is used for compensation of the varying power,
(b) a single VOA located before the line fiber, where the single VOA is used for the varying power, and
(c) modifying settings associated with any of a launch power and amplifier gain;
observing total noise, at an optical receiver, from all of the plurality of spans; and
isolating noise for the span under test from the total noise based on a plurality of oscillations of the varying power and the associated observing thereof.