On-line optical fiber grating preparing system

[0020] Embodiments of the present invention are further described below with reference to the accompanying drawings.

[0021] It consists of a drawing tower and a writing grating device, including a drawing furnace 2 and a preform clamping and feeding device 1 installed above the drawing furnace. A bare fiber caliper 3 is installed below the outlet of the drawing furnace. A writing grating device 5 is installed below the bare optical fiber 4, and a first-level coater 6 and a first-level ultraviolet curing furnace 7, a second-level coating device 8 and a second-level ultraviolet curing furnace are sequentially arranged below the writing grating device along the vertical downward direction of the bare fiber 4. Curing furnace 9, a fiber optic caliper 10 is installed under the secondary ultraviolet curing furnace to detect the outer diameter of the coated optical fiber 11, and the coated optical fiber is then transferred to the spinning wheel 13 through the tension measuring instrument 12, and passes through the grating position marking device 14. The matching device 15 and the wire drawing and take-up speed are retracted to the take-up reel 16 . The drawing speed of the drawing wheel is 2~30m/min. The grating writing device includes a phase mask 17 and a 193 nm excimer laser 21 . The phase mask is arranged close to the center of the bare fiber, and the distance between the phase mask and the center of the bare fiber is 0.3 mm. A diaphragm 19 and a lens 18 are installed at the output end of the 193nm excimer laser. The 193nm excimer laser outputs a single-pulse laser beam, which is shaped by the diaphragm, and then focused by the lens, and irradiated to the phase mask. The excimer laser light path (beam) 20 Keep straight transmission and perpendicular to the bare fiber 4. The pulse width of the single-pulse laser beam output by the 193 nm excimer laser is less than or equal to 4 ns. The 193nm excimer laser is connected with the computer 22, and the grating writing process is controlled by the computer.

[0022] The method for preparing the optical fiber grating of the present invention is as follows: the quartz glass matrix optical fiber preform is clamped on the optical fiber drawing tower to be melted and drawn, and the melted bare fiber is continuously extended downward, firstly, the grating is inscribed, and then the outer layer is coated with the outer layer. and drying, and finally received in the take-up reel, the grating writing adopts a phase mask method to configure a 193 nm excimer laser to perform single-pulse exposure on the bare fiber to write the grating. Exposure and coating take-up are performed in-line continuously. The excimer laser light path (beam) 20 keeps transmitting in a straight line and is perpendicular to the bare fiber 4, and the pulse width of the 193 nm excimer laser is less than or equal to 4 ns.

[0023] The optical fiber preform is placed in the drawing furnace 2, and its lower end is melted and then taped to form a wire. The diameter of the bare optical fiber is monitored by the bare optical fiber caliper 3 and the speed of the preform feeding device 1 and the bare optical fiber 4 is feedback-controlled in real time to realize the diameter of the bare optical fiber. stability control. The wire drawing speed is 15m/min. A grating writing device consisting of a phase mask and a 193 nm laser 5 writes gratings on the bare fiber moving downward, one light pulse writes a grating, and the bare fiber with the gratings written then enters the first coating 6 and the first coating. One cure 7, followed by a second coat 8 and a second cure 9. After coating, the diameter of the coated fiber 11 is monitored by the coated fiber caliper 10 to control the thickness of the coating layer. The tension measuring instrument 12 monitors the tension of the optical fiber, and at the same time co-positions the optical fiber with the preform feeding device 1 to keep the optical fiber in a vertical state. The drawing wheel 13 controls the drawing speed. The coated optical fiber 11 is marked by the grating position marking device 14 under the action of the take-up wheel 13 , and then collected on the take-up reel 16 by the drawing and take-up speed matching device 15 .

[0024] The invention adopts a 193nm laser combined with a phase mask method, in the process of low-loss optical fiber drawing, single-pulse exposure of bare optical fiber to prepare low-reflection grating, continuous exposure, and online preparation of one to one hundred thousand high-quality low-reflection gratings on the drawing tower rate fiber gratings and form arrays. During the wire drawing process, online real-time monitoring of equipment and states such as feeding device, wire drawing furnace, coater, UV curing furnace, gas flow and pressure, optical fiber tension, and wire drawing speed is carried out. Afterwards, the diameter of the optical fiber is measured to realize the adjustment and control of the entire system and ensure the stable operation of the entire system. In addition, the grating is written online under controlled temperature and humidity conditions, so that the fiber background temperature at the grating writing point has better consistency. By controlling the moving speed of the bare fiber and other measures above, the diameter of the bare fiber and the tension of the fiber are stably controlled to ensure the stability of the internal stress of the fiber, thereby ensuring the consistency of the grating written online. The process of writing gratings is controlled by the computer 22, and the spacing between the gratings and the intensity of the laser beam can be set as required.