This paper presents new solutions for laser vibrometry, which are based on fibre vibrometry in the third telecommunication window. The scattered laser beam from a vibrating object is guided by a fibre collimator and coherently detected through heterodyning it with an acousto-optical frequency-shifted reference beam. The concept of measuring vibration parameters from many points of the vibrating object has been inspired by wavelength division multiplexing (WDM) in fibre telecommunications. The N-independent WDM separated 15XX nm fibre-coupled laser diodes (used for optical fibre telecommunications) form a system of sources for multipoint vibration measurement according to the rule ‘one wavelength–one point’.
We report the design and characteristics of a simple and compact mode-locked Er-doped fiber laser and its application to broadband cavity-enhanced spectroscopy. The graphene mode-locked polarization maintaining oscillator consumes less than 5 W of power. It is thermally stabilized, enclosed in a 3D printed box, and equipped with three actuators that control the repetition rate: fast and slow fiber stretchers, and metal-coated fiber section. This allows wide tuning of the repetition rate and its stabilization to an external reference source. The applicability of the laser to molecular spectroscopy is demonstrated by detecting CO 2 in air using continuous-filtering Vernier spectroscopy with absorption sensitivity of 5.5 × 10 −8 cm −1 in 50 ms.
In this paper we present an effective method of pulse distortion pre-compensation in saturated high-power fiber amplifiers by arbitrarily shaping the input pulse. We derive a simple expression which allows us to generate userdefined pulse shapes at the output of the amplifier chain consisting of more than one stage. The numerical results were verified experimentally using a diode-seeded all-fiber two-stage master oscillator-power amplifier (MOPA) source based on Er 3+ /Yb 3+ -doped double-clad fiber. Several examples of obtained output shapes are presented, including high-energy 100-ns-long rectangular pulses.
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