BlackRock (NYSE: CIEN) reports 11.27M shares, 8.0% stake

Rhea-AI Filing Summary

BlackRock, Inc. files an amended Schedule 13G/A reporting ownership of 11,274,540 shares of CIENA CORPORATION common stock, representing 8.0% of the class as of 03/31/2026. The amendment notes these holdings reflect securities held by certain Reporting Business Units of BlackRock, Inc.

Insights

Institutional Ownership Analyst

BlackRock reports an 8.0% stake in CIENA via consolidated reporting units.

BlackRock's amendment discloses 11,274,540 shares beneficially owned with 10,538,703 shares carrying sole voting power as of 03/31/2026. The filing attributes holdings to specific Reporting Business Units rather than all BlackRock business units.

Implications depend on each unit's trading discretion; subsequent filings could clarify which subsidiaries hold or trade these shares.

Key Figures

Beneficially owned: 11,274,540 shares Percent of class: 8.0% Sole voting power: 10,538,703 shares +3 more

6 metrics

Beneficially owned 11,274,540 shares Amount beneficially owned as of 03/31/2026

Percent of class 8.0% Percent of CIENA common stock as of 03/31/2026

Sole voting power 10,538,703 shares Shares with sole power to vote reported on Schedule 13G/A

Sole dispositive power 11,274,540 shares Shares with sole power to dispose reported on Schedule 13G/A

CUSIP 171779309 CIENA CORPORATION Common Stock CUSIP

Filing signature date 04/24/2026 Date signature certifying amendment

Key Terms

Schedule 13G/A, Beneficially owned, Sole Dispositive Power, Reporting Business Units

4 terms

Schedule 13G/A regulatory

"Amendment No. 5 ) CIENA CORPORATION Common Stock"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficially owned regulatory

"Item 4. | Ownership (a) | Amount beneficially owned: 11274540"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole Dispositive Power regulatory

"7 | Sole Dispositive Power 11,274,540.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Reporting Business Units regulatory

"reflects the securities beneficially owned ... by certain Reporting Business Units"

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 5)

CIENA CORPORATION

(Name of Issuer)

Common Stock

(Title of Class of Securities)

171779309

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 171779309

1

Names of Reporting Persons

BlackRock, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 10,538,703.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 11,274,540.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

11,274,540.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.0 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: CIENA CORPORATION
(b)	Address of issuer's principal executive offices: 7035 RIDGE ROAD HANOVER MD 21076
Item 2.
(a)	Name of person filing: BlackRock, Inc. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units (collectively, the "Reporting Business Units") of BlackRock, Inc. and its subsidiaries and affiliates. It does not include securities, if any, beneficially owned by other business units whose beneficial ownership of securities are disaggregated from that of the Reporting Business Units in accordance with such release.
(b)	Address or principal business office or, if none, residence: BlackRock, Inc., 50 Hudson Yards New York, NY 10001
(c)	Citizenship: See Item 4 of Cover Page
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 171779309
Item 4.	Ownership
(a)	Amount beneficially owned: 11274540
(b)	Percent of class: 8.0 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 10538703
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 11274540
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of CIENA CORPORATION. No one person's interest in the common stock of CIENA CORPORATION is more than five percent of the total outstanding common shares.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See Exhibit 99
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

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, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

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.

BlackRock, Inc.

Signature:	Spencer Fleming
Name/Title:	Managing Director
Date:	04/24/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7

FAQ

What stake does BlackRock hold in CIEN according to this Schedule 13G/A?

BlackRock reports beneficial ownership of 11,274,540 shares, equal to 8.0% of CIENA's common stock as of 03/31/2026. The filing shows 10,538,703 shares with sole voting power for BlackRock's reporting units.

Does this amendment indicate who within BlackRock controls the CIEN shares?

The amendment states the holdings reflect certain Reporting Business Units of BlackRock, Inc.; it does not list individual funds. It clarifies that other BlackRock business units may hold separate holdings disaggregated under SEC guidance.

What voting and dispositive powers does BlackRock report for these CIEN shares?

BlackRock reports 10,538,703 shares as sole power to vote and 11,274,540 shares as sole power to dispose of. Shared voting and dispositive powers are reported as 0 in the amendment.

When was the Schedule 13G/A signed and what is the relevant ownership date?

The cover records the ownership as of 03/31/2026. The amendment was signed by Spencer Fleming, Managing Director, on 04/24/2026, certifying the information in the filing.