Fiber optic reflector is a compact device that reflects a special wavelength while passing through all other wavelengths. It is used to detect any link problem in the PON system. Usually, the special wavelength is a test wavelength, which is not in the range of the working wavelength. It makes the test to find the problem will not affect the normal links.

According to the working mechanism, there are two types:

1. FBG(Fiber Bragg Grating) fiber optic reflector

The fiber material is photosensitive, the incident light coherent field pattern can be written into the core of the fiber through exposure to ultraviolet light, it makes the refractive index of the core axis change periodically, then form a spatial phase grating. It functions as a narrow band filter in the core. When a beam of broad-spectrum light passes through the fiber grating, the wavelength which meets the Bragg condition of the fiber grating will reflect, and the rest of the wavelengths will pass through the fiber grating.

2. Dielectric film reflector

The dielectric film reflector can be pre-installed in the connector or adapter. It will change the physical structure of the connector/adapter. When the reflect bandwidth is wide(bigger than 20nm), this type is a good solution.