Two-Particle Parasitic Effects in Rare-Earth Doped Waveguides

This paper discusses Er-doped optical waveguides implemented in glass materials. The emphasis is put on physical limitations posed by concentration dependent nonlinear effects and on methods for their characterization. Examples of recently demonstrated, best performance integrated active devices are also given

Alternating cascade of spectrally different erbium-doped fiber amplifiers for link-loss-insensitive long-haul WDM transmission

This paper numerically investigates a cascade of erbium-doped fiber amplifiers (EDFA's) with different spectral characteristics in an alternating scheme. Thereby, in a transmission band with appropriate spectral properties (1544-1550 nm), the sensitivity of optically amplified long-haul WDM transmission links on the span loss between amplifiers can be reduced to that of single-channel systems. This may be as much as an order of magnitude better than in a traditional, nonalternating, WDM cascade. While passive bandpass filters are necessary to control the wavelength range, there is no need for any active gain equalization or feed-back control. The gain in the cascade can also to some extent automatically adjust to compensate for a spectral tilt of the loss, We show that the range of this automatic loss tilt compensation can be increased, up to three times its original value, by enhancing the difference of the net gain that signals at different wavelengths experience in EDFA's of different types

Steady-State and Switch-Off Behavior of Upconversion in Er-Doped Fibers

By measuring the metastable and the upconverted fluorescence in Er-doped fibers we determine rate of homogeneous upconversion as a function of the population inversion. The results confirm the prediction of our statistical model that at the same population inversion the upconversion rates under the steady-state and the switch-off conditions are different. The larger rate of the steady state upconversion is attributed to the pump enhanced redistribution of the excitation energy

Analysis of gain improvements through a pump reflector in Er³⁺-doped optical amplifiers in the presence of concentration quenching

We numerically examine the small-signal gain improvements possible when the pump light is reflected in erbium-doped amplifiers suffering from concentration quenching caused by homogeneous and inhomogeneous energy-transfer upconversion. For an unquenched amplifier, the improvement is larger for a pump power of 20 mW than it is at 100 mW. On the other hand, at a pump power of 100 mW, the reflector is found to be efficient for a quenched amplifier, with a maximum improvement of 6.5 dB. We also find that the reflector is more efficient at 1.535 μm than it Is at 1.550 μm, under all examined operating conditions

Nondestructive method for measuring the degree of cluster-induced quenching in Er3+-doped waveguides and fibers

Ion clustering is one of the major dissipative processes in the operation of Er3+-doped planar waveguide amplifiers and heavily doped fiber amplifiers. We propose and demonstrate a nondestructive method for measuring the fraction of erbium ions in doped planar waveguides and fibers that are quenched by ultrafast parasitic energy transfer in ion pairs or clusters. The method is based on unsaturable absorption measurements in the 980-nm absorption band. By combining transmission data at resonance with the corresponding data for radiation outside the absorption band, the influence of background and coupling losses can be eliminated. (C) 1998 Optical Society of America

Optical study and structure modelling of PPI liquid crystalline dendrimer derivatives

Optical study of two families of poly(propylene imine) (PPI) dendrimers (G = 1–5) are reported. The enlarging of the chain number (generations) of the PPI dendrimer leads to the spectra shift to IR region in solvent until 8 and 19 nm for both families, respectively. The theoretical modelling of the dendrimer structure was performed. The geometric characterization of dendrimer structure demonstrates that the preferable free space for encapsulation is periphery of the PPI dendrimerVilniaus pedagoginis universitetasVytauto Didžiojo universitetasŠvietimo akademij