Long Period Fiber Grating

Long Period Fiber Grating (LPFG) is formed by the periodic refractive index modulation in the fiber axis, and its period is generally larger than 100µm. Its coupling mechanism is: the fundamental mode of the fiber core transmitted forward is coupled into the cladding mode of the forward transmission of several specific wavelengths, and the cladding mode is quickly lost, so the LPFG basically has no retroreflection, and in its transmission there are several absorption peaks at specific wavelengths in the spectrum.