V. Karalekas

Impact of nonlinear spectral broadening in ultra-long Raman fibre lasers

We present an experimental study of the impact of FWM-induced nonlinear spectral broadening on the effective reflectivity of ultra-long Raman fiber laser cavities of diverse lengths and fiber bases. We observe an exponential decay of the effective reflectivity with growing power. In standard single-mode fiber, effective reflectivity drops of up to 50% for shorter cavity lengths are observed, while the longest cavity length of 82.4km displays power leakage amounting to an effective reduction of reflectivity of approximately 30%. Using different types of fiber we examine the effect of chromatic dispersion on the Stokes wave broadening.

High efficiency supercontinuum generation using ultra-long Raman fiber cavities

Supercontinuum generation in a multi-fibre ultra-long Raman fibre laser cavity is investigated experimentally. By using this cavity configuration we demonstrate improved spectral flatness and supercontinuum generation efficiency.

Experimental demonstration of mode structure in ultralong Raman fiber lasers

We present the first experimental demonstration of a resolvable mode structure with spacing c/2nL in the RF spectra of ultralong Raman fiber lasers. The longest ever demonstrated laser cavity (L=84 km), RF peaks of ~100 Hz width and spacing ~1 kHz have been observed at low intracavity powers. The width of the peaks increases linearly with growing intracavity power and is almost independent of fiber length.

Long-distance soliton transmission through ultralong fiber lasers

We present the first experimental demonstration (to our knowledge) of long-distance unperturbed fundamental optical soliton transmission in conventional single-mode optical fiber. The virtual transparency in the fiber required for soliton transmission, over 15 complete periods, was achieved by using an ultralong Raman fiber laser amplification scheme. Optical soliton pulse duration, pulse bandwidth, and peak intensity are shown to remain constant along the transmission length. Frequency-resolved optical gating spectrograms and numerical simulations confirm the observed optical soliton dynamics.

165 km ultra-long raman fibre laser in the C-band

We present the first experimental demonstration of a Raman fibre laser operation with a resolvable ~0.6 kHz mode spacing operating at 1551 nm. Our laser has a record cavity length of 165 km.

High efficiency supercontinuum generation using ultra-long Raman fibre cavities

Supercontinuum generation in a multi-fibre ultra-long Raman fibre laser cavity is investigated experimentally. By using this cavity configuration we demonstrate improved spectral flatness and supercontinuum generation efficiency.

Signal Power Excursion and Pump Efficiency in Quasi-Lossless Ultra-Long Raman Laser Links

Performance optimisation of ultra-long Raman laser links is studied theoretically and experimentally. We observe that it is possible to reduce signal power excursion by adjusting FBG reflectivity without compromising pump efficiency.

CW lasing in a telecom fibre due to the random distributed feedback via Rayleigh scattering

We demonstrate a fibre laser with a mirrorless cavity that operates via Rayleigh scattering amplified through the Raman effect. The properties of such random distributed feedback laser appear different from those of both traditional random lasers and conventional fibre lasers.

True soliton transmission through ultra-long laser links

We present the first experimental demonstration of true (not loss managed) soliton pulse transmission in conventional optical fibre. Experimental FROG spectrograms and numerical simulations confirm the soliton pulse evolution dynamics.

Turbulent Spectral Broadening in Ultra-Long Raman Fibre Lasers

The turbulent nature of the generation of multiple cavity modes in ultra-long Raman fiber lasers is demonstrated in this study. Observations show turbulence-induced broadening of the intra-cavity spectrum and formation of clearly pronounced exponential tails at the power level as small as ~0.1 W. This broadening is likely to occur due to nonlinear four-wave mixing.