Propagation of signal and noise in concatenated erbium-doped fiberoptical amplifiers

Signal propagation and noise accumulation in lightwave systems using saturated optical amplifiers as repeaters are analyzed. Numerical simulations of amplified spontaneous emission in concatenated erbium-doped fiber amplifiers indicate that a reach beyond 10000 km is possible with a 1.55-μm system in the absence of fiber nonlinearities. Distributed optical amplifiers are shown to have low noise, but require higher pump power than lumped amplifiers. Three operating modes of an amplifier lightwave system are identified and their relative signal power efficiency and noise performance are described     

Use of LD-pumped erbium-doped fiber preamplifiers with optimalnoise filtering in a FDMA-FSK 1 Gb/s star network

An erbium-doped fiber amplifier was implemented in a closely spaced FDMA-FSK (frequency-division-multiple-access-frequency-shift-keyed) optical star network with a signaling rate of 1 Gb/s per channel. The fiber preamplifier, which is laser-diode pumped, increases the sensitivity of the direct-detection avalanche photodiode (APD) receiver by 14 dB, allowing for an increased number of network users. This enhanced sensitivity nearly corresponds to all of the available gain of the amplifier. Furthermore, the amplifier noise is optimally filtered by means of a wide band interference filter cascaded with a narrow band fiber Fabry-Perot filter     

Fundamental limits of all-optical NRZ-to-soliton conversion bynonlinear optical loop mirrors

All-optical NRZ-to-RZ conversion through nonlinear optical loop mirrors (NOLM) is analysed. By computing the time-bandwidth output characteristics, we investigate the dependence of the NOLM switching power and control envelope on the chirp of the switched RZ pulses. The effect of this chirp on further propagation in the soliton regime and related continuum generation is then analysed by an inverse-scattering transform     

Amplification of spontaneous emission in erbium-doped single-modefibers

Amplification of spontaneous emission (ASE) in erbium-doped single-mode fiber amplifiers operating at λ=1.53 μm is studied theoretically and experimentally. The ASE noise spectra obtained from the theory are found to be in excellent quantitative agreement with the experimental data. The observed changes in ASE spectral shapes under different population inversion conditions are also explained. The model may be used to evaluate the performance of erbium-doped fiber lasers as well as to assess the noise characteristics of erbium-doped fiber amplifiers as applied to wavelength-division multiplexing optical communications