Infinera has cut 53 jobs at a facility in Sunnyvale, California, as part of a corporate restructuring effort tied to its recent acquisition of rival Coriant.

The restructuring was announced in a U.S. Securities and Exchange Commission (SEC) filing on Dec. 10. It noted that the initial phase of the program would “optimize resources for future growth, improve efficiencies, and address redundancies following the Coriant acquisition.”

Infinera said the initial phase of the program would cost between $6 million and $8 million, with most of the activity completed by Dec. 29. The California job cuts were included in a recent State of California report.

Infinera has not yet responded to questions regarding the extent of the job cuts across the organization. It did note in the SEC filing that, “the company is continuing to review the potential impact of the restructuring initiative and is unable to estimate any additional significant costs or charges at this time, which are expected to include one-time retention costs and facilities-related and other costs.”

Infinera’s management did not mention the restructuring plans when it spoke with investors during its third-quarter earnings conference call in early November. Infinera CFO Brad Feller during that call did note that a combination of restructuring costs tied to severance, retention, and other one-time costs would be between $75 million and $80 million.

Infinera closed on its $430 million acquisition of Coriant on Oct. 1. The combined entity counted around 4,200 employees at closing. In a presentation tied to the deal, Infinera claimed it would result in $100 million in savings through operational integration. A vast majority of that savings was linked to operating expenses.

The Coriant deal was initially announced in July. It consolidated what were two similarly-sized second-tier vendors in the optical networking space into a more robust segment challenger.

A recent IHS Markit report on the optical networking space had the newly-bolstered Infinera as the world’s No. 5 player in the market. Segment leaders include Huawei, Ciena, ZTE, and Nokia. Other “challengers” in the space include Fujitsu, ECI, and ADVA.