| Subject | English | German |
| IT | graded-index optical fiber | Gradientenfaser |
| earth.sc., tech. | instrument with optical index | Lichtmarken-Instrument |
| earth.sc., tech. | instrument with optical index | Lichtmarken-Meßgerät |
| el., meas.inst. | instrument with optical index | Lichtmarkenmessgerät |
| obs., phys.sc., chem. | optical index | Brechungsexponent |
| obs., phys.sc., chem. | optical index | Brechungszahl |
| obs., phys.sc., chem. | optical index | Brechungskoeffizient |
| obs., phys.sc., chem. | optical index | Brechungsindex |
| gen. | optical index | Brechzahl |
| earth.sc. | optical polymer with a single index of refraction | optisches Polymer mit nur einem Brechungsindex |
| IT | step-index optical fiber | Stufenfaser |
