Abstract: A bottom cylinder for a high-temperature and high-pressure environment simulator of a high-fidelity corer is provided. The bottom cylinder includes a cylinder barrel. The bottom of the cylinder barrel is provided with a cylinder base. The piston is provided inside the cylinder barrel and divides an inner cavity of the cylinder barrel into a rodless cavity and a rod cavity. The piston is provided with a piston rod. The outer wall of the cylinder barrel is provided with an oil inlet hole communicated with the rodless cavity, an oil outlet hole communicated with the rod cavity, and a reserved hole. The lower end surface of the piston is provided with a first buffer ring, and the upper surface of the cylinder base is provided with a second buffer ring mated with the first buffer ring. The bottom cylinder is applied to the simulator for oil and gas resource exploitation.

Abstract: A small core-diameter graded-index optical fiber include a core layer and a cladding having an inner cladding layer, a depressed cladding layer, and an outer cladding layer from inside to outside thereof. The core layer has a parabolic refractive index profile with a distribution index in a range of 1.9-2.1, a radius in a range of 10-21 ?m, and a ?1 max in a range of 0.7-1.7% at a core layer center, and is a silica glass layer co-doped with germanium, phosphorus, and fluoride. The inner cladding layer is a pure silica layer or an F-doped silica glass layer, and has a unilateral width in a range of 0.5-5 ?m and a ?2 in a range of ?0.4-0%. The depressed cladding layer has a unilateral width in a range of 2-10 ?m and a ?3 in a range from ?0.8% to ?0.2%. The outer cladding layer is a pure silica glass layer.

Abstract: A small core-diameter graded-index optical fiber include a core layer and a cladding having an inner cladding layer, a depressed cladding layer, and an outer cladding layer from inside to outside thereof. The core layer has a parabolic refractive index profile with a distribution index in a range of 1.9-2.1, a radius in a range of 10-21 ?m, and a ?1 max in a range of 0.7-1.7% at a core layer center, and is a silica glass layer co-doped with germanium, phosphorus, and fluoride. The inner cladding layer is a pure silica layer or an F-doped silica glass layer, and has a unilateral width in a range of 0.5-5 ?m and a ?2 in a range of ?0.4-0%. The depressed cladding layer has a unilateral width in a range of 2-10 ?m and a ?3 in a range from ?0.8% to ?0.2%. The outer cladding layer is a pure silica glass layer.