RESTRUCTURING COSTS (Details) $ in Thousands		3 Months Ended			6 Months Ended
		Apr. 30, 2017 USD ($)	Jan. 31, 2017 USD ($) employee	Apr. 30, 2016 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2016 USD ($)
Activity and balance of the restructuring liability accounts
Balance at beginning of period			$ 2,838		$ 2,838	$ 1,279
Additional liability recorded		$ 4,276		$ 535	6,671	919
Additional liability recorded						929
Adjustment to previous estimates						(10)
Cash payments					(4,217)	(1,026)
Balance at end of period		5,292		1,172	5,292	1,172
Current restructuring liabilities		5,081		1,006	5,081	1,006
Non-current restructuring liabilities		211		166	211	166
Workforce reduction
Restructuring Cost and Reserve [Line Items]
Number of employee reduction | employee	[1]		50
Activity and balance of the restructuring liability accounts
Balance at beginning of period			$ 868		868	591
Additional liability recorded	[1]				2,369
Additional liability recorded						929
Adjustment to previous estimates						0
Cash payments					(3,084)	(823)
Balance at end of period		153		697	153	697
Current restructuring liabilities		153		697	153	697
Non-current restructuring liabilities		0		0	0	0
Consolidation of excess facilities
Activity and balance of the restructuring liability accounts
Balance at beginning of period			$ 1,970		1,970	688
Additional liability recorded	[2]				4,302
Additional liability recorded						0
Adjustment to previous estimates						(10)
Cash payments					(1,133)	(203)
Balance at end of period		5,139		475	5,139	475
Current restructuring liabilities		4,928		309	4,928	309
Non-current restructuring liabilities		$ 211		$ 166	$ 211	$ 166

[1] Reflects a global workforce reduction of approximately 50 employees during the first quarter of fiscal 2017 as part of a business optimization strategy to improve gross margin, constrain operating expense and redesign certain business processes and systems.

[2] Reflects unfavorable lease commitments and relocation costs incurred during the second quarter of fiscal 2017 in connection with the facility transition from Ciena's existing research and development center located at Lab 10 on the former Nortel Carling Campus to a new campus facility in Ottawa, Canada.