You could try a fibre inspection scope. They are sold by a number of suppliers and are less expensive than setting up a microscope. I use a handheld fibre inspection scope to check the end of the fibre after hand polishing. If you need to take a picture then perhaps a small digital USB microscope such as those commonly used in schools might help.

Dear Xinyang,

in our laboratory we use low coherence interferometers to characterize the fiber end faces with a direct roughness evaluation.

This is certainly a very good solution to characterize your process.

Best regards,

Guilherme

Hello,

you may use interference contrast microscopy, e.g. TIC as described in the attachment. 

Matthias Vaupel

Hi;

I am not very familiar with fiber topic, but I am working on roughness as well. We excessively use AFM for roughness measurements in nm. I would recommend you use the AFM as well. Is there any problem with using AFM for fiber roughness measurements?

The answer here is that we could measure this depending on the diameter of the fiber.  Keeping in mind that we have 0.9um XY resolution, I would think somewhere around 50um diameter would be the smallest we could accurately measure. If the fibers are smaller, then the best option would probably be an AFM.

There is a publication on researchgate, at the following link, that includes a some nice pictures (in figure 1) of what an optical fiber looks like for various stages of polishing. The paper also describes how the images of the fiber were taken. If you can view the end of your fiber in detail you can compare the observed roughness with a "scratch and dig" reference target and make a visual estimate of the roughness. If you need a quantitative measurement of roughness then you may need to use one of the techniques described in the other answers to this question, such as an interferometer or surface profiler.

https://www.researchgate.net/publication/230609171_Impact_of_surface-polish_on_the_angular_and_wavelength_dependence_offiber_focal_ratio_degradation

Article Impact of surface-polish on the angular and wavelength depen...

Roughness of fiber end may be detected by measuring the scattering of light at the output end.