Document and Entity Information - shares	9 Months Ended
	Jul. 31, 2017	Sep. 01, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	CIENA CORP
Entity Central Index Key	0000936395
Current Fiscal Year End Date	--10-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jul. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		142,688,322