Our purpose is to make 1 mm spot size of quartz tungsten halogen light with 100 mm working distance for spectral imaging of wavelengths of 350-2000 nm.
With some QTH light source and adapter on the market, I can focus 250W QTH light to 800 um diameter beam for a SMA connector of fiber cable. But as a novice for fiber optics, I need to ask following questions to achieve the goal above.
What range of core size of fiber optic cable is required for my setup above? A sales representative recommended core size of 200 um. But I need to understand reason (formula) behind of the selection. Do we have to buy a singlemode or multimode cable and why? Are there any other conditions other than core size and NA to select a fiber cable?
According to some basics on optics, I need to first collimate light from fiber cable before focusing it. In order to select right collimator, should NA of fiber cable match NA of collimator? Although I think it does not make a good sense to me, one of my colleagues brought up this question.
I found there is virtually no collimator or focuser package for the wavelength range above. So I am afraid that we need to assemble our own collimator/focuser with some combination of optics. For example, for collimating light from fiber source (S), 15 mm FL reversed plano-convex lens (L1) can be used and for focusing, 100 mm FL plano-convex lens (L2) can be used. According to optics basics, distance (D1) between S and L1 should be 15 mm, distance (D2) between L1 and L2 can be 1 mm. Is this setup would work for us? Is there any other consideration I am missing?