The sale of Nortel's last substantial operating asset, bar the carrier voice unit which is set to go to Genband later this year, means the firm now has no need of a restructuring head.
He will be replaced as Nortel CFO by corporate group head John Doolittle, but given the nature of the light work - mostly concerning Nortel's intellectual property and transitional maintenance services - that remains to be done, he will not be filling the CRO role.
Binning said it was "an appropriate point" to step down from the top job, which he took last summer after Mike Zafirovski was shown the door.
A career finance man, Binning joined the firm in 2007 from UK-based heavy building materials supplier Hanson, and previously held senior positions at Marconi, as well as Johnnie Walker and Smirnoff owner Diageo.
Ciena elected, as permitted by the terms of the sale agreement, to swap the $239m principal amount of convertible notes with cash consideration of $244m, and therefore has paid an all-cash purchase price of $774m.
The unit's new owners have committed to retain approximately 2,000 Nortel staff.
In a departing statement Binning hailed the "significant progress on Nortel's plan to preserve both our technology and rich base of skilled employees."
"The sale of our optical and carrier Ethernet businesses to Ciena enables customers to continue to benefit from Nortel's heritage," he added.