Miniature pop-up fiber grating crack meter

The utility model provides a miniaturized pop-up fiber grating crack meter. The crack meter comprises a shell, a transmission rod, a sensor sensitive structure, a transmission rod gland, a bottom cover, an external terminal and a spring, the sensor sensitive structure comprises a strain optical fiber, an equal-strength beam, a first optical fiber clamp, a second optical fiber clamp and a tail cable. The strain optical fiber is fixed on the constant-strength beam through the first optical fiber clamp and the second optical fiber clamp, the first optical fiber clamp is contacted with the tail part of the transmission rod, and the second optical fiber clamp is fixedly connected with the bottom cover; and two tail cables connected with the two ends of the strain optical fiber penetrate out ofthe bottom cover and then are respectively connected with the two external terminals. The transmission rod is simple in structure, small in size and high in precision, the transmission rod is activelyejected out through the s