Launch optical system is used for analysis of optical diffusion of multimode optical fiber, plastic optical fiber, etc. under specially restricted launch condition. For this object, we supply two kind of launch optical system, Underfilled launch optical system / M-Scope type G, and Mode-selective launch optical system / M-Scope type ML. In this article, we explain the difference between underfilled launch method and mode-selective launch method.
（Fig.1）Underfilled launch
Underfilled launch optical system is the special launch optics that change the spot size and irradiation N.A. (Numerical Aperture) of launch light, and analyze the optical diffusion of multimode optical fiber, plastic optical fiber, etc.
Image of underfilled launch method is shown left as figure 1. In case of underfilled launch, sample fiber is launched by all the light flux as specified N.A. In this case, beam profile of launch light on sample fiber core has flat shape.
By Synos' Underfilled launch optical system / M-Scope type G,
（Fig.2）Mode-selective launch
In case of mode-selective launch, sample fiber is launched by the light flux of only the specified N.A. In other words, mode-selective launch optics generate the launch light that has the specified incident angle only.
Image of mode-selective launch method is shown left as figure 2. As shown in figure 2, launch light has only specified N.A. light flux (specified incident angle light flux), launch light has ring condition incident angle light flux.
By Synos' Mode-selective launch optical system / M-Scope type ML,
