Ciena has slumped to a GAAP net loss of $109.9m (£71m) or $1.18 per share after booking $17m of acquisition and integration-related costs associated with the integration of Nortel's Metro Ethernet Networks (MEN) business.
The third quarter of Ciena's fiscal 2009, which closed on 31 July, was the first quarter to include full numbers from the MEN unit, which contributed $221.8m to a sales pot that totalled $389.7m.
Ciena added that two customers between them accounted for 34% of total aggregate revenue during the quarter.
In spite of the alarming slide in its numbers, Ciena said in a statement that "increasing levels of customer activity and continued strength in teh fundamental demand drivers of our business" were standing the vendor in good stead for the coming quarter.
CEO Gary Smith said: "We're pleased with our progress and believe our financial performance this quarter is evidence of both the strategic value and market acceptance of the combined company."