| Cover | Aug. 16, 2021 |
| Cover [Abstract] | |
| Document Type | S-3 |
| Entity Registrant Name | NeoPhotonics Corp |
| Entity Address, Address Line One | 3081 Zanker Road |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 94-3253730 |
| Entity Address, State or Province | CA |
| Entity Address, City or Town | San Jose |
| Entity Address, Postal Zip Code | 95134 |
| City Area Code | 408 |
| Local Phone Number | 232-9200 |
| Entity Central Index Key | 0001227025 |
| Amendment Flag | false |
| Entity Filer Category | Accelerated Filer |
| Entity Small Business | false |
| Entity Emerging Growth Company | false |
