Item 1. (a) Ciena Corp (b) 7035 Ridge Road Hanover, Maryland 21076 United States Item 2. (a) Platinum Investment Management Limited (b) Level 8, 7 Macquarie Place Sydney NSW 2000 Australia (c) Australia (d) Common Stock (e) 171779309 Item 3. (e) An IA in accordance with Section 240.13d-1(b)(1)(ii)(e) Item 4. (a) 6,563,925 (b) 6.1% (c) (i) 5,710,236 (ii) 0 (iii) 6,563,925 (iv) 0 Item 5 No Item 6 The clients of Platinum Investment Management Ltd including pooled investment vehicles and other managed accounts have the right to receive or power to direct the receipt of dividends from, and the proceeds from the sale of, Ciena Corp. Item 7 N/A Item 8 N/A Item 9 N/A Item 10 (a) By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. (b) N/A After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.