Optical attenuation from moving lenses settled between fiber-optic collimators

This paper proposes and theoretically shows how movable lenses inside an imaging system situated between two fiber-optic collimators alter the optical beam waist tremendously and thereby induce high optical attenuation. Under the condition that the maximum movement of the lens is comparable to the focal length of the lens, a higher maximum optical attenuation (e.g., >30 dB) can be accomplished under a shorter focal-length (e.g., <100 □m) lens. This result implies that a very-compact inline high-dynamic-range variable fiber-optic attenuator can be easily implemented.