V. T. Potapov

Statistics of intensity of backscattered semiconductor laser radiation in single-mode optic fiber

We have studied the statistics of the intensity of backscattered radiation of a semiconductor laser in single-mode optic fiber as a function of the probing laser pulse duration and coherence time. It is shown that, at a given radiation source coherence time, the intensity distribution function varies, depending on the pulse duration, from nearly exponential to nearly Gaussian. The exponential statistics provides a better sensitivity for a coherent reflectometer with direct detection. Using the calculated distribution function, it is possible to qualitatively determine the degree of deterioration of the reflectometer sensitivity with respect to external factors during increasing probing pulse duration or decreasing laser coherence time. These data provide criteria for the optimum choice of a radiation source for the coherent fiber-optic reflectometer.

Optical fiber vibration measuring transducers based on irregular multimode fibers

Single-mode/multi-mode/single-mode (SMS) optical fiber structures with irregular multi-mode fiber (MMF) segments have been studied in the regime of photoinduced resonance oscillations. It is shown that these SMS structures can be used to create multiparametric optical fiber vibration measuring transducers.

Coherent fiber-optic reflectometer with 810-nm semiconductor laser

Coherent fiber-optic reflectometer with a single-mode (λ = 810 nm) semiconductor laser as a radiation source has been experimentally studied. It is demonstrated that distributed fiber-optic sensors for detecting and locating dynamic impacts can be created based on the proposed reflectometer with a fiber circuit length of up to 3 km.

Passive synchronization of fiber laser modes by a microcavity reflector

The dynamics of generation of an erbium-doped fiber laser with an external microcavity reflector has been studied under conditions where the frequency of photoinduced elastic oscillations of the micro-structure is close to the intermode interval of the laser cavity. The possibility of passive synchronization of the laser modes is demonstrated and the dependence of the laser pulse frequency on the system parameters is determined.

Self-modulation of the radiation from fiber lasers with microcavity mirrors

The domain of excitation of self-oscillations is experimentally studied in a system consisting of an erbium fiber laser and a microcavity. The dependences of the self-oscillation frequency on the parameters of the system are found. The features of the self-oscillations are analyzed for the case where the laser radiation simultaneously interacts with several microcavities.

A fiber-optic unit for measuring absolute distances and displacements with a nanometer resolution

A fiber-optic unit for measuring small absolute distances, namely, the base of the Fabry-Perot interferometer, formed by the fiber end and the reflecting surface from 30 to 250 μm with a resolution of no worse than 50 nm is described. The foundation for operation of the unit is the spectral method of the fiberoptic low-coherence interferometry.

Parametric oscillations in optical micro- and nanofibers

The static and dynamic instability of the rectilinear shape of optical micro- and nanofibers, which is caused by the propagating light, has been studied. Light power thresholds that correspond to the onset of instability are estimated and the possible fields of application of the related phenomena are outlined.

Fiber laser with passive Q-switching based on photoinduced fiber resonance oscillations

Automodulation oscillations in the intensity of a fiber laser in the regime of passive Q-switching based on resonance bending oscillations of a fiber segment representing an element of the laser cavity have been studied. It is shown that the proposed scheme can be used for the creation of fiber-optic transducers.

A fiber optic phase modulator with an optical frequency shift of up to 20 GHz

A fiber optic phase modulator is described in which the phase of a light wave traveling in an optical fiber is modulated by a composite electromechanical resonator with Q≌1000. The instantaneous frequency of the wave at the modulator output varies according to a harmonic law. The interval of tuning of the instantaneous light wave frequency achieved in the experiment is 20 GHz, which corresponds to a modulation index of ≌106. It is demonstrated that a maximum value of the frequency tuning range is determined by the elastic limit of the resonator material.

Self-excited oscillations in a fiber-optic laser-collimator-microresonator system

This paper proposes and studies experimentally a design for a fiber-optic self-excited oscillator, characterized by high stability of the operating point. The design appears promising for developing fiber-optic transducers of physical quantities with a frequency output.