Mode-field diameter of single-mode fiber by knife-edge scanning in the far field

Knife-edge scanning has been applied to the far-field patterns of both matched-clad and depressed-clad single-mode fiber at 1300 nm. The method offers several advantages as compared with other techniques. The mode-field diameter (MFD) has been derived according to a Gaussian fitting procedure, and values agree closely with those obtained with the other standardized procedures.