All-fiber carbon isotope detection system and detection method

The all-fiber carbon isotope detection system comprises a detection light source, a time-delay optical fiber and an input optical fiber, an optical fiber annular channel comprises a hollow-core optical fiber air chamber, and the two opposite ends of the hollow-core optical fiber air chamber are connected with the time-delay optical fiber and the input optical fiber respectively; the probe light is propagated in the optical fiber annular channel and circularly passes through the hollow-core optical fiber air chamber; the hollow-core optical fiber gas chamber is filled with gas to be detected; the pump light source is connected with the optical fiber annular passage and is used for generating pump light and introducing the pump light into the hollow-core optical fiber gas chamber, the temperature and the refractive index of gas are changed under the action of the pump light, and the phase of probe light is changed after the probe light passes through the gas in the hollow-core optical fiber gas chamber; the pho