We used an excimer laser (193 nm), a femtosecond laser (775 nm) and a CO<sub>2</sub> laser (10.6 µm) to drill cylindrical holes in fused silica optical fibers and in glass micro-pipettes. CO<sub>2</sub> laser-drilling using tip processing results in tapered holes with larger diameters than the holes drilled with the excimer and the femtosecond laser. Although routing of holes of various shapes results in sharper edges and a higher aspect ratio when the femtosecond laser is used, the CO<sub>2</sub> laser could still be used to route rectangular holes in fused silica optical fibers. Albeit hole dimensions and details are smaller when micromachined with the excimer and the femtosecond lasers, the optical fibers are very brittle at the end of the process. CO<sub>2</sub> lasers offer the advantage of producing higher fused silica ablation rates with much better polished surfaces and a better mechanical integrity, which are usually more suitable in some applications.