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.