Two main causes of optical fiber loss

The following are the two major causes of fiber loss:

1 Optical fiber intrinsic loss

The intrinsic loss of optical fiber is the inherent loss of optical fiber, mainly due to the defects of the optical fiber machine matrix material quartz glass and the metal transition impurities and oh-, so that the light in the transmission process to generate scattering, absorption and dispersion, generally can be divided into scattering loss, absorption loss and dispersion loss. The scattering loss is caused by the fluctuation of the atomic density in the material, the uneven density in the condensation process and the uneven concentration caused by the density fluctuation. The absorption loss is due to the fiber core containing metal transition impurities and oh-absorption light, especially in the infrared and ultraviolet spectral area of the glass exists inherent absorption. The optical fiber dispersion can be divided into three types according to the causes, namely material dispersion, waveguide dispersion and mode colors scatter. One of the Single-mode fiber is based on the transmission, so there is no mold colors scattered. In the eigen factor of single-mode fiber, the maximum of the connection loss is the Mode field diameter. The connection loss caused by the intrinsic factor of single-mode fiber is about 0.014dB, and 0.2dB connection loss will be produced when the Mode field diameter mismatch 20%. The normalized frequency of multimode fiber is v>2.404, there are multiple waveguide mode transmission, the V value is larger, the mode is more, besides the material dispersion and waveguide dispersion, there is also the mode colors scatter, general mode colors disperses occupies the main position. The so-called mode colors scatter, is refers to the different modes of the optical fiber at the same frequency phase constant β different, so the group velocity caused by different dispersion.

In addition, optical fiber geometry parameters such as fiber core diameter, cladding diameter, core/cladding concentricity, roundness, optical parameters such as relative refractive index, maximum theoretical numerical aperture, and so on, as long as one or more mismatch, will have different degrees of intrinsic loss.

2 Optical fiber Additional loss

The additional loss of optical fiber is generally composed of radiation loss and application loss. The radiation loss is due to the optical fiber drawing process, the fiber diameter, the fluctuation of the ellipse degree, the expansion shrinkage of the plastic layer temperature and the low temperature shrinkage of the coating caused by the fiber micro-bending; The application loss is due to the loss caused by the tension, bending and extrusion of the optical fiber.