Dear Mr. X, I am a postdoctoral fellow that works in Dr. Y’s group at the W institute located in Bologna. We own a Nikon Eclipse 2000-E laser scanning confocal microscope equipped with a scan head. Last week we noticed some strange artefacts in our confocal images. I am enclosing two confocal images of a rhodamine B film. The images were recorded using two different lasers (405 and 488 nm). Please notice that the illumination pattern is inhomogeneous and that there are bright lines across the image. These features cannot be attributed to the rhodamine B film itself. Previous images of this film have always shown a homogeneous illumination pattern. Furthermore, the bright lines across the image were absent in previous images of this film. We strongly believe that the problem is the optical fibre that goes from the three-laser unit to the scan head (referred to as the “optical-fibre cable for excitation light” in the microscope manual). I am also enclosing a photo of how the laser beam looks like when it comes out of the optical fibre. As you can see, the light does not exit the fibre as a single round spot, but rather as a round spot surrounded by somewhat distorted diffraction rings. This weird pattern is identical regardless of the laser source used, which suggests that the problem is not the alignment of the three-laser unit, but the optical fibre itself. Replacing the “optical-fibre cable for excitation light” does not seem trivial because of how this fibre is connected to the three-laser unit. What would you suggest us to do? Do you think that the problem is indeed the optical fibre? If you need more information, please let me know. Kind regards, XXXX.