Search

The nonlinear Fourier transform (NFT) is a potentially promising way to mitigate nonlinear signal distortions in fiber-optic communication systems [1–4]. Recently, the new approach named the b-modulation was introduced [1] that allows to control the temporal duration of NFT-generated signals. In the "traditional" NFT-based communication, the nonlinear spectrum, r (ξ) is used to modulate data. Then the signal duration depends on the signal energy and is not predetermined and controlled. The utilisation of the NFT scattering coefficient b (ξ) gives a possibility to control the pulse duration in time domain under condition that the Fourier spectrum of b (ξ) is localized. In particular, the OFDM format satisfies that condition. It was already shown that the properties of the effective noise in the NFT domain differ from a circular Gaussian noise. More specifically, such a noise is signal-dependent and non-circular [2, 3]. It was shown in [4] that the covariance B 1 and pseudo-covariance B 2 characteristics related to b-coefficient of NFT spectrum depend on the propagation distance. Here, we extend our previous work and examine noise characteristics for a novel b-modulation transmission introduced in [1]. We demonstrate that the variances behaviour is generic and do not depend on a specifics of NFT modulation. The presence of amplifier spontaneous emission in the optical link translates into the effective noise in the nonlinear spectral domain as an effective additive term N (ξ, b (ξ, 0)): $e^{-4 i \xi^{2L}b}(\xi, L) = b(\xi, 0) + N(\xi, b(\xi, 0), L)$ , where $\xi$ is the “nonlinear frequency” (NFT spectral parameter): $\langle N (\xi)N^*(\xi ')\rangle = 2DL\pi \delta (\xi -\xi')B_{1}(\xi, L), \langle N (\xi)N(\xi')\rangle = 2DL\pi \delta (\xi - \xi ')B_{2}(\xi, L) $

Silica-based luminescent materials have gained significant attention over the last several years primarily to be used under integrated photonics. In this context Ce-doped silica are particularly interesting due to their potential to be used as Si-based light emitting sources [1]. In this work we have prepared a Ce-doped silica fiber that is drawn from a preform which is prepared using standard MCVD technology. In this work we study the spontaneous lifetime and fluorescence parameters of a Ce-doped silica fiber when pumped with 405 nm continuous wave laser.

Nonlinear Fourier transform (NFT) has attracted in the past several years a renewed interest as a potential tool for mitigation of nonlinear signal distortions in optical communications [1]. The NFT exploits the integrability of the master equation for the signal evolution in the optical fibre — nonlinear Schroedinger equation (NLSE). The NFT maps the solution of the NLSE to the domain of the complex-valued spectral parameter ξ, the nonlinear analogue of frequency. The complete set of nonlinear spectral data contains continuous functions α(ξ), b (ξ), and discrete spectrum, consisting of two complex-valued parameters for each discrete degree of freedom: eigenvalue ξ eig , IM ξ eig > 0, and spectral amplitude C(ξ eig ) associated to a discrete soliton eigenvalue [1].

A novel non-invasive, wearable VCSEL-based system for multipoint in − vivo measurements of blood perfusion was introduced. The system operates on the basis of the laser Doppler flowmetry (LDF) method and allows for microcirculation studies. The sensors developed were used to analyse the skin blood flow synchronization in homologous regions of the contralateral limbs, both in the basal state and during various functional tests. A high synchronisation of blood flow rhythms in the contralateral limbs of healthy volunteers was shown in the studies presented.

A pure Ce-doped silica fiber is fabricated using modified chemical vapor deposition (MCVD) technique. Fluorescence characteristics of a Ce-doped silica fiber are experimentally investigated with continuous wave pumping from 440 nm to 405 nm. Best pump absorption and broad fluorescence spectrum is observed for ~ 405 nm laser. Next, the detailed analysis of spectral response as a function of pump power and fiber length is performed. It is observed that a -10dB spectral width of ~ 280 mn can be easily achieved with different combinations of the fiber length and pump power. Lastly, we present, for the first time to the best of our knowledge, a broadband fluorescence spectrum with -10dB spectral width of 301 nm, spanning from ~ 517.36 nm to ~ 818 nm, from such fibers with non-UV pump lasers.

We demonstrate a single wavelength operation from an InGaN/GaN distributed feedback (DFB) blue laser at 42X nm. The 39th order grating is etched in the sidewall to achieve single wavelength. The laser has a FWHM of ~ 25 pm at 500mA pulsed current with 15 mW output power.

We investigate the wavelength-tuning of cascade quantum-well GaSb-based diode lasers emitting at 3.2 µm. An external-cavity setup is used to demonstrate wavelength-tuning over a range of 250 nm with a maximum output power of 8.4 mW.