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Accounts Receivable
 12 Months Ended
Oct. 31, 2019
Receivables [Abstract]  
ACCOUNTS RECEIVABLE ACCOUNTS RECEIVABLE

As of October 31, 2019, one customer accounted for 12.0% of net accounts receivable. As of October 31, 2018, one customer accounted for 10.0% of net accounts receivable. Ciena has not historically experienced a significant amount of bad debt expense. During fiscal 2017, Ciena’s allowance for doubtful accounts includes a provision for a significant asset impairment of $13.7 million for a trade receivable related to a single customer in the APAC region. The following table summarizes the activity in Ciena’s allowance for doubtful accounts for the fiscal years indicated (in thousands):
Year ended
 
Beginning
 
 
 
Net
 
Ending
October 31,
 
Balance
 
Provisions
 
Deductions
 
Balance
2017
 
$
3,963

 
$
18,221

 
$
4,604

 
$
17,580

2018
 
$
17,580

 
$
2,700

 
$
2,902

 
$
17,378

2019
 
$
17,378

 
$
6,740

 
$
4,017

 
$
20,101