Methods and systems using one or more distributed feedback (DFB) lasers for capturing changes in the lasing environment are disclosed. Specifically, a sensor for measuring a measurand, such as pressure or temperature, or changes in a measurand, includes a fiber with at least one core, at least one fiber laser cavity formed by a single fiber grating in the core, wherein the laser operates on at least two modes along at least part of its length. The DFB laser includes a section that is bent into a non-linear shape and at least one pump laser connected to the fiber laser cavity. When the DFB laser experiences a perturbation or measurand change that changes the spacing of the modes, a change in an RF beat note is generated. This beat note can then be measured and related to the measurand change.

A displacement sensor including an optical whispering gallery mode (WGM) microresonator and a package encasing at least a portion of the WGM microresonator, the package comprising polydimethylsiloxane (PDMS). The WGM microresonator can be configured as a sensor and used in a displacement detection system that can detect displacement with high quality. Artificial intelligence can be implemented in the displacement detection system for improved sensing of different variables and/or pinpointing the location of perturbations.

A method for measuring position of a translational movable element of a nuclear reactor, includes emitting kN optical signals, k and N being natural numbers greater than or equal to 1, by kN so-called emitter optical fibres included in N probes resistant to a primary medium; receiving the kN optical signals by N tracks resistant to a primary medium, each track receiving k optical signals, the tracks having reflecting surfaces and diffusing surfaces; receiving, by mN so-called receiver optical fibres, m being a natural number greater than or equal to k, included in the N probes, the kN optical signals reflected or diffused by the N tracks; converting the kN optical signals received by the mN receiver optical fibres into binary code.