The invention discloses a composite hollow-
core optical fiber and application thereof in detection of
hydrocarbon gas, and belongs to the technical field of optical fibers. The composite hollow-
core optical fiber sequentially comprises an outer cladding layer, an inner cladding layer and a
fiber core from outside to inside. The inner cladding is an anti-
resonance area and comprises four anti-
resonance units which are uniformly distributed in the circumferential direction, and each anti-
resonance unit comprises three
layers of circular
micro capillary tubes which are coaxially nested in sequence from inside to outside; the outer cladding is a photonic
band gap region, comprises a plurality of air holes which are tangent to one another, and is of a hexagonal structure as a whole; the
fiber core is filled with air and is formed by encircling a plurality of anti-resonance units in the inner cladding. The composite hollow-
core optical fiber has the characteristics of a hollow-core photonic
band gap optical fiber and a hollow-core anti-resonance
optical fiber, a three-layer circular
micro capillary structure is adopted, light can be effectively limited in a
fiber core, and
transmission loss is reduced; and the composite hollow-core
optical fiber can work under the ultra-wide
wavelength condition of 5.5-9.5 [mu] m, so that the requirement for detecting toxic
hydrocarbon gas is met.