Fiber grating and method and apparatus for fabricating the same

Abstract

A core is co-doped with Ge in a general concentration equivalent to that in a core of an optical fiber to be connected as well as Sn and Al in predetermined concentrations. A glass part F including the core and a cladding is coated with a primary coat layer of a UV transmitting resin which transmits UV of 240 nm through 270 nm but cures by absorbing UV of a shorter wavelength band than 240 nm or a longer wavelength band than 270 nm. A grating is written in the core by irradiating the core with UV through the primary coat layer. The primary coat layer is covered with a secondary coat layer of a resin having a negative coefficient of linear expansion so as to cancel and suppress expansion/shrinkage of the glass part in accordance with temperature change derived from the positive coefficient of linear expansion. Thus, the invention provides a fiber grating and a method of fabricating a fiber grating, in which a grating can be easily written without causing degradation of the transmitting characteristic, the transmitting characteristic and the mechanical strength characteristic can be consistent with each other without spoiling improvement of productivity, and the temperature characteristic can be stabilized for attaining high reliability.