TUBE-ENCASED FIBER GRATING

摘要

A tube-encased fiber grating includes an optical fiber (10) having at leastone Bragg grating (12) impressed therein which is embeddedwithin a glass capillary tube (20). Light (14) is incident on the grating (12)and light (16) is reflected at a reflection wavelength .lambda.1. Theshape of the tube (20) may be other geometries (e.g., a "dogbone" shape)and/or more than one concentric tube may be used or more thanone grating or pair of gratings may be used. The fiber (10) may be doped atleast between a pair of gratings (150, 152), encased in thetube (20) to form a tube-encased compression-tuned fiber laser or the grating(12) or gratings (150, 152) may be constructed as a tunableDFB fiber laser encased in the tube (20). Also, the tube (20) may have aninner region (22) which is tapered away from the fiber (10)to provide strain relief for the fiber (10), or the tube (20) may have tapered(or fluted) sections (27) which have an outer geometry thatdecreases down to the fiber (10) and provides added fiber pull strength. Also,the tube encased grating (12) exhibits lower mode couplingfrom the fiber core to the cladding modes due to the increased diameter of thecladding where the tube (20) is fused to the fiber (10) wherethe grating is located (12).