Frequently Asked Questions

A phase-shifted FBG has a deliberate phase defect at its center, splitting it into two grating sections. This creates a very narrow transmission (or reflection notch) peak within the grating's broader spectrum — much narrower than the grating's overall bandwidth would otherwise allow.

Typical FWHM of the central peak ranges from 0.1 nm down to as narrow as 0.005 nm, depending on the strength of the two grating sections either side of the phase defect.

Phase-shifted FBGs are used in single-frequency and DFB-type fiber lasers, high-resolution sensing, and any application needing a filter narrower than a standard FBG can provide.