Single-mode fiber - Characteristics

1 attenuation coefficient a: the physical meaning of its provisions with the same multi-mode fiber.

(2) dispersion coefficient D (λ): the fiber dispersion can be divided into three parts, mode dispersion, material dispersion and waveguide dispersion. For single-mode fiber, since the implementation of the single-mode transmission so there is no mode dispersion problems, so the dispersion mainly as material dispersion and waveguide dispersion (collectively referred to within the dispersion model). Considering the single-mode fiber dispersion and waveguide dispersion of the material, referred to the dispersion coefficient. Dispersion coefficient can be understood: as units per kilometer of fiber-optic spectral width of the pulse broadening caused by the value. Thus, L km of optical fiber dispersion caused by the pulse broadening values​​: σ = δλ · D (λ) · L (2.17) of which: δλ as the light source spectral width σ is the root mean square value of the dispersion coefficient of broadening the smaller the better. The fiber dispersion coefficient, the greater the coefficient means that the bandwidth the greater transmission capacity.

3 mode field diameter d: characterization of single-mode fiber mode field diameter of concentrated light energy level. Since only the fundamental mode in single-mode fiber during the transmission, so roughly speaking, is the mode field diameter single-mode fiber receiver in the fundamental mode spot diameter of the surface (in fact there is no apparent fundamental mode spot boundary), mode field diameter d and similar to single-mode fiber core diameter.

4 cut-off wavelength λc: When the fiber normalized frequency V is less than the normalized cutoff frequency Vc, the single-mode transmission can be achieved, that is only in the fundamental mode in fiber transmission, all the rest of the high-order mode cut-off. In addition to fiber parameters such as core radius, numerical aperture must meet certain conditions, to achieve single-mode light-wave transmission must also grew up in a value, that is, λ ≥ λc, this value is called the single-mode optical fiber cut-off wavelength. Therefore, the cutoff wavelength λc is the meaning, can achieve single-mode optical fiber transmission minimum operating wavelength. In other words, even though other conditions are met, but if you grow up in single-mode fiber optical wave cut-off wavelength, still can not be achieved single-mode transmission.

5 Return Loss --- ReturnLoss: reflection loss, also known as return loss, it is pointed out that the light side, after the reflected light relative to the input ratio in decibels of light, the greater the return loss as possible to reduce the reflected light of the light source and the impact of the system