D4 is a 2mm ferrule fiber connector used primarily in Japan for single mode telecom applications. The threaded coupling and smaller ferrule than SC provide a compact yet secure connection for telecom equipment.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | Fiber Core | Single mode optical signal | BUS |
| 2 | Threaded Body | 2mm threaded coupling | I/O |