The embodiments of the present invention provides an optical demodulator, which includes a first reflective mirror, a second reflective mirror, a third reflective mirror, and an optical splitter. The optical splitter is configured to: split input light for the first time; split for the second time a first path of light reflected back by the first reflective mirror, where two paths of light obtained by splitting the first path of light are emitted to the first reflective mirror and the third reflective mirror respectively, split for the second time a second path of light reflected back by the second reflective mirror, where two paths of light obtained by splitting the second path of light are emitted to the first reflective mirror and the third reflective mirror respectively.