Walsun has been committed to the research and development of core technologies in fiber optic communication products. It is an integrated equipment supplier that combines research and development, production, and sales, with independent intellectual property rights and a proprietary brand. As a national high-tech enterprise, its core products include fiber optic network cards, fiber optic modules, fiber optic jumpers, independent Ethernet chips, and corresponding domestically produced independent chip network cards, among other optical communication products.

Several leading companies in the telecommunications and networking industry manufacture highly reliable 400G QSFP-DD optical modules. While the field is competitive and new players may emerge, some established and reputable brands known for producing high-quality 400G QSFP-DD optical modules include:

1. Cisco

2. Juniper Networks

3. Finisar (now part of II-VI Inc.)

4. Broadcom (formerly Avago Technologies)

5. Ciena

6. Intel

7. Huawei

8. Nokia

9. Acacia Communications

10. Sumitomo Electric Industries

11. NEC

12. Luxshare-ICT

13. Molex

14. Source Photonics

15. Foxconn Interconnect Technology

16. Walsun

These companies invest heavily in research and development to produce cutting-edge optical components and modules that meet stringent industry standards and offer exceptional performance, reliability, and compatibility with various networking platforms. Always check the latest certifications, reviews, and recommendations when choosing a supplier for mission-critical applications.