The utility model relates to the field of
optical fiber interference sensors, and discloses an M-Z interference sensor of a seven-
core optical fiber cascaded graded-index multimode
optical fiber, which comprises a light injection single-mode
optical fiber, a step multimode optical
fiber, a seven-
core optical fiber, a graded-index multimode optical
fiber and a light receiving single-mode optical
fiber which are connected in sequence, the axis of the joint of the seven-
core optical fiber and the gradient
refractive index multimode optical fiber deviates by a preset offset; the outer side of a fiber core of the seven-core optical fiber is coated with a stress layer, and the
radius of the fiber core of the step multimode optical fiber is larger than the
radius of the stress layer of a central fiber core of the seven-core optical fiber and smaller than the
minimum distance from the central fiber core of the seven-core optical fiber to the stress layer of the fiber core on the outer side of the seven-core optical fiber. The length of the seven-core optical fiber is far smaller than that of the gradient multimode optical fiber; and the
refractive index of the stress layer material outside the fiber core of the seven-core optical fiber is smaller than that of the cladding material of the seven-core optical fiber. According to the scheme, the problems that the interference valley is too wide and the
extinction ratio is too low in a gradient
refractive index multimode optical fiber interference sensor can be solved while the high-sensitivity sensing characteristic is maintained.