On September 3, China’s Ministry of Commerce (MOFCOM) ruled that Corning and other U.S. fiber optic makers had been trying to get around existing anti-dumping duties by tweaking their trade patterns and shipping a slightly different product to China — a type of cutoff wavelength shifted single-mode fiber known as G.654.C. MOFCOM said this move didn’t have solid business logic, weakened the impact of the original duties, and therefore counted as duty evasion. Based on that, the ministry announced a 37.9% anti-dumping tariff on U.S.-made single-mode fiber, including Corning’s products, starting September 4. Corning and Ciena shares initially dipped but quickly bounced back, ending the day up 0.7% and 0.8% respectively.
Although China and the U.S. are in a temporary truce at the moment, small skirmishes continue. Today, the U.S. Treasury sanctioned a Guangzhou-based Chinese company and two individuals over fentanyl. On August 27, the U.S. Department of Commerce issued a preliminary anti-dumping ruling on corrugated polypropylene boxes imported from China, imposing a uniform high tariff of 83.64%. A final decision, combining the anti-dumping and countervailing duty rulings, is expected on November 12.
Back on 4 March, MOFCOM launched an anti-circumvention investigation into U.S.-origin cut-off wavelength shifted single-mode optical fibre imports.
Notably, this is China’s first-ever anti-circumvention investigation as a trade remedy measure. Cut-off wavelength shifted single-mode optical fiber is a type of fiber that, through structural parameter adjustments (such as refractive index distribution, core, and cladding dimensions), shifts its original cut-off wavelength. By modifying these structural parameters, the fiber's transmission and application characteristics can be altered compared to its originally designed cut-off wavelength.
Since 2010, China has conducted anti-dumping investigations on imported non-dispersion shifted single-mode optical fiber of U.S. and EU origin, and has been imposing anti-dumping duties on such imports from the U.S. and EU since 2017. According to MOFCOM’s announcement, a leading Chinese cable company accused U.S. optical fiber manufacturers Corning Incorporated, OFS Fitel, and their exporters of circumventing the anti-dumping duties by changing the product name and tariff classification. Consequently, MOFCOM has initiated this anti-circumvention investigation. It is evident that the impact of this investigation is limited to a very small number of companies and a narrow industry segment.
Corning’s troubles with Chinese trade regulators go way back. More than a decade ago, in 2011, Chinese fiber companies complained that U.S. giants like Corning were undercutting them by dumping fiber into the Chinese market at unfairly low prices. After an investigation, MOFCOM agreed and slapped anti-dumping duties on imports of U.S.-made non-dispersion shifted single-mode fiber starting that April.
For Corning, that meant its products suddenly got hit with an extra cost in China, wiping out much of its price advantage. Normally these duties run for five years, but when they were set to expire in 2017, MOFCOM reviewed the case and decided to keep them in place for another five years. In 2018, the ministry even adjusted the rates — Corning’s was in the 30% range, while some other U.S. companies faced tariffs of more than 70%.
Things didn’t ease up in the following years. In 2023, when the duties were due to expire again, China extended them through 2028. That basically left Corning with no real relief in the Chinese market.
Fast forward to 2025: Chinese regulators noticed U.S. exporters had started shipping a “new” type of fiber — the G.654.C model. Technically, it wasn’t listed in the original tariff scope, but in practice, its uses and market impact were almost identical to the older non-dispersion shifted fiber. Chinese rivals like YOFC (Yangtze Optical Fibre and Cable) filed complaints, prompting MOFCOM to launch an anti-circumvention probe. The ministry concluded this new product line was essentially a workaround to dodge tariffs, not a legitimate business shift. The result: these newer fibers are now also covered by the anti-dumping duties, meaning Corning and other U.S. firms must pay up.
All of this has left Corning at a serious disadvantage in one of the world’s biggest fiber markets. China’s policies have tilted the playing field toward domestic players, while Corning either has to swallow steep tariffs or look for workarounds — like joint ventures or setting up local production — just to keep a foothold.
The MOFCOM Ruling is available:
MOFCOM Announcement No. 48 of 2025
Ruling on the Anti-Circumvention Investigation into Certain Cut-off Shifted Single-Mode Optical Fiber Originating in the United States[Issuing Authority] Trade Remedy and Investigation Bureau
[Document Number] MOFCOM Announcement No. 48 of 2025
[Date of Issuance] September 3, 2025On March 4, 2025, at the request of Yangtze Optical Fibre and Cable Joint Stock Limited Company, the Ministry of Commerce (MOFCOM) issued Announcement No. 14 of 2025, deciding to initiate an investigation into whether imports of certain cut-off shifted single-mode optical fiber originating in the United States were circumventing the anti-dumping measures imposed on imports of dispersion unshifted single-mode optical fiber from the United States.
MOFCOM investigated whether the imports of certain cut-off shifted single-mode optical fiber originating in the United States constituted an act of circumvention of trade remedy measures as provided under Article 36 of the Foreign Trade Law of the People’s Republic of China. Based on the investigation results, and in accordance with Article 37 of the Foreign Trade Law, the investigating authority rendered a ruling (see annex). The relevant matters are hereby announced as follows:
I. Ruling
MOFCOM rules that U.S. optical fiber producers and exporters, by altering trade patterns, exported certain cut-off shifted single-mode optical fiber (G.654.C optical fiber) to China without sufficient commercial justification, thereby undermining the effectiveness of the existing anti-dumping measures. This constitutes circumvention of the anti-dumping measures imposed on dispersion unshifted single-mode optical fiber originating in the United States.
II. Existing Anti-Dumping Measures
On April 21, 2011, MOFCOM issued Announcement No. 17 of 2011, deciding to impose anti-dumping duties on imports of dispersion unshifted single-mode optical fiber originating in the United States, with a five-year implementation period starting from April 22, 2011.
On April 21, 2017, MOFCOM issued Announcement No. 20 of 2017, deciding to continue imposing anti-dumping duties on the above product for another five years starting from April 22, 2017.
On July 10, 2018, MOFCOM issued Announcement No. 53 of 2018, adjusting the applicable anti-dumping duty rates on U.S. companies to a range of 33.3%–78.2%.
On April 21, 2023, MOFCOM issued Announcement No. 16 of 2023, deciding to continue imposing anti-dumping duties on dispersion unshifted single-mode optical fiber originating in the United States for another five years starting from April 22, 2023.
Product Description Subject to Existing Measures:
Chinese Name: 非色散位移单模光纤
English Name: Dispersion Unshifted Single-Mode Optical Fiber
Description: Commonly referred to as G.652 optical fiber or G.652 single-mode fiber. It has both the 1550nm and 1310nm windows. The zero-dispersion point is near 1310nm, with minimum attenuation at 1550nm but maximum dispersion.
Typical values: attenuation at 1310nm: 0.3–0.4 dB/km, dispersion coefficient: 0–3.5 ps/nm·km; attenuation at 1550nm: 0.19–0.25 dB/km, dispersion coefficient: 15–18 ps/nm·km.
Uses: Low internal loss, large bandwidth, cost efficiency, widely used for high-speed, long-distance transmission, including long-haul communications, trunk lines, cable TV, and feeder loops.
Tariff Code: 90011000 (excluding other optical fibers, fiber bundles, cables, and ITU-T G.657 A/B type fibers).
III. Anti-Circumvention Measures
Based on the investigation results, MOFCOM proposed to the Tariff Policy Commission of the State Council to adjust the scope of taxation. The Commission, acting on MOFCOM’s recommendation, decided—pursuant to Article 49 of the Foreign Trade Law, Article 54 of the Customs Law, and Article 55 of the Anti-Dumping Regulations—that starting from September 4, 2025, the existing anti-dumping duty rates on dispersion unshifted single-mode optical fiber from the United States shall also apply to imports of certain cut-off shifted single-mode optical fiber from the United States.
Product Description Subject to Anti-Circumvention Measures:
Name: Certain Cut-off Shifted Single-Mode Optical Fiber (G.654.C Optical Fiber)
Description: A sub-category of G.654 optical fiber. At the 1550nm window, typical values are attenuation of 0.14–0.20 dB/km and dispersion coefficient not exceeding 20 ps/(nm·km).
Tariff Code: 90011000 (other products under this heading are excluded).
Applicable Anti-Dumping Duty Rates:
Corning Incorporated – 37.9%
OFS Fitel, LLC – 33.3%
Draka Communications Americas, Inc. – 78.2%
All other U.S. companies – 78.2%
IV. Levying Method
Starting from September 4, 2025, importers of certain cut-off shifted single-mode optical fiber originating in the United States shall pay the corresponding anti-dumping duties to the General Administration of Customs of the People’s Republic of China.
Calculation formula:
Anti-dumping duty = Customs-assessed dutiable price × applicable anti-dumping duty rate.Import VAT shall be levied on the dutiable price plus customs duty and anti-dumping duty.
V. Duration of Measures
The anti-circumvention measures will be implemented from September 4, 2025, until April 21, 2028, the expiration date of the existing anti-dumping measures on dispersion unshifted single-mode optical fiber from the United States.
VI. Review
During the implementation period, interested parties may, after a reasonable period, apply in writing to the investigating authority for a review of the necessity to continue implementing the anti-circumvention measures in the form and level set out in this announcement.
VII. Administrative Reconsideration and Litigation
In accordance with Article 65 of the Foreign Trade Law, any party dissatisfied with this anti-circumvention decision may apply for administrative reconsideration according to law, or file an administrative lawsuit with a people’s court.
VIII. Effective Date
This Announcement shall take effect on September 4, 2025.
Annex: Ruling of the Ministry of Commerce of the People’s Republic of China on the Anti-Circumvention Investigation into Certain Cut-off Shifted Single-Mode Optical Fiber Originating in the United States (PDF)
Ministry of Commerce of the People’s Republic of China
September 3, 2025