Cover Page - USD ($) $ in Billions	12 Months Ended
	Oct. 31, 2020	Dec. 11, 2020	May 01, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Oct. 31, 2020
Current Fiscal Year End Date	--10-31
Document Transition Report	false
Entity File Number	001-36250
Entity Registrant Name	Ciena Corp
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	23-2725311
Entity Address, Address Line One	7035 Ridge Road
Entity Address, City or Town	Hanover
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21076
City Area Code	410
Local Phone Number	694-5700
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	CIEN
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 7.1
Entity Common Stock, Shares Outstanding		154,564,349
Documents Incorporated by Reference	Part III of the Form 10-K incorporates by reference certain portions of the registrant’s definitive proxy statement for its 2021 Annual Meeting of Stockholders to be filed with the Commission not later than 120 days after the end of the fiscal year covered by this report.
Entity Central Index Key	0000936395
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false