<TABLE> <S> <C>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
BALANCE SHEET, STATEMENT OF OPERATION AND STATEMENT OF CASH FLOWS INCLUDED IN
CIENA'S FORM 10-Q FOR THE PERIOD ENDING JULY 31, 2000, AND IS QUALIFIED IN ITS
ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 9-MOS
<FISCAL-YEAR-END> OCT-31-2000
<PERIOD-START> NOV-01-1999
<PERIOD-END> JUL-31-2000
<CASH> 209,903
<SECURITIES> 34,159
<RECEIVABLES> 223,578
<ALLOWANCES> 10,491
<INVENTORY> 108,026
<CURRENT-ASSETS> 661,670
<PP&E> 297,490
<DEPRECIATION> 129,618
<TOTAL-ASSETS> 852,590
<CURRENT-LIABILITIES> 131,218
<BONDS> 0
0
0
<COMMON> 1,419
<OTHER-SE> 678,081
<TOTAL-LIABILITY-AND-EQUITY> 852,590
<SALES> 571,160
<TOTAL-REVENUES> 571,160
<CGS> 319,380
<TOTAL-COSTS> 178,618
<OTHER-EXPENSES> (9,503)
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 259
<INCOME-PRETAX> 82,406
<INCOME-TAX> 26,782
<INCOME-CONTINUING> 55,624
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> 55,624
<EPS-BASIC> .40
<EPS-DILUTED> .37
</TABLE>