<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.

<MULTIPLIER> 1,000

                             
<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
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          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