Noise performance evaluation of distributed erbium-doped fiberamplifiers with bidirectional pumping at 1.48 μm

An accurate model for unsaturated fiber amplifiers with fiber background loss is used to determine optimal parameters for distributed amplification in erbium-doped fibers. Pump power at 1.48 μm and erbium-doping levels required for transparency are studied for both unidirectional and bidirectional pumping schemes. An optimal erbium absorption coefficient which minimizes the required pump power is found. However, this case corresponds to the highest amplifier noise figure. The authors conclude that, in practice, distributed erbium-doped fiber amplifiers are not significantly advantageous compared to 980-nm-pumped lumped amplifier schemes     

Noise performance of erbium-doped fiber amplifier pumped at 1.49μm, and application to signal preamplification at 1.8 Gbit/s

Direct measurements of the noise figure of an erbium-doped fiber amplifier are described. With an amplifier gain as high as 36 dB, a noise figure as low as 4.1 dB was measured. Noise figures remained below 6 dB for signal wavelengths within the high gain (G>20 dB) region of the amplifier. An optical receiver sensitivity of -43 dBm at 1.8 Gb/s, corresponding to 215 photons/b, was achieved using the fiber amplifier as an optical preamplifier for a direct detection receiver     

Demonstration of packet switching through an integrated-optic tree switch using photo-conductive logic gates

Optical routing control of 10 Gbit/s data through a tree-structured photonic switch is experimentally demonstrated. A binary route address within a header is optically processed to control the switch.<>     

Analysis of distributed erbium-doped fiber amplifiers with fiber background loss

An accurate model for erbium-doped fiber amplifiers with fiber background loss applicable to the unsaturated gain regime is presented. Exact analytical solutions are derived for the output pump power, gain, and amplified spontaneous noise as a function of input pump power in the cases of unidirectional or bidirectional pumping. An exact relation is also derived between the pump threshold and the pump required for fiber transparency. Such expressions are particularly useful to model distributed fiber amplifiers and to determine the optimal fiber parameters corresponding to a given pumping scheme. As an example, the analytical solutions are used to study the pump power requirement for distributed fiber amplifiers unidirectionally pumped at 1.48 mu m, and to determine an optimum Er/sup 3+/ absorption coefficient.<>     

Analysis of erbium-doped fiber amplifiers pumped in the4I15/2-4I13/2 band

A theoretical model for the amplifiers predicts gain coefficients of around 2 dB per milliwatt of launched pump power, in close agreement with previously reported measurements. The model is also used to determine the optimal pump wavelength λ_opt that maximizes the amplifier gain. It is shown that the latter is insensitive to pump detuning near λ_opt=1.48 μm, within a 20 nm range, which indicates that broadband, multimode laser diode pump sources and pumps with narrow linewidths should yield identical gain performance     

Optimal pump wavelength in the4I15/2-4I13/2 absorption band for efficient Er3+-doped fiberamplifiers

The authors report the measured gain of a highly efficient erbium-doped fiber amplifier pumped at wavelengths between 1.46 and 1.51 μm. The optimal pump wavelength, λ_opt, was determined to be 1.475 μm. At this wavelength, the maximum gain coefficients for signals at 1.531 and 1.544 μm were 2.3 and 2.6 dB/mW, respectively. At λ_opt, high gains ranging from 32 dB at pump power P_p=20 mW up to 40 dB at P _p=80 mW were obtained. These modest pump powers are within the capabilities of currently available 1.48-μm diode lasers. The width about λ_opt for 3-dB gain variation exceeded 27 nm for P_p=10 mW and 40 nm for P_p >20 mW. With this weak dependence on pump wavelength, single-longitudinal-mode lasers do not have a significant advantage over practical Fabry-Perot multimode pump lasers     

2-Gbit/s signal amplification at λ=1.53 μm in anerbium-doped single-mode fiber amplifier

The gain, saturation power, and noise of an erbium-doped single-mode traveling-wave fiber amplifier operating at a wavelength λ=1.53 μm are characterized. In continuous-wave (CW) measurements amplification at 2 Gbit/s was demonstrated with up to 17-dB gain for 1×10^-9 bit error rate at 1.531 μm and a 3-dB full bandwidth of 14 nm. From the determination of the fiber-amplifier's output signal-to-noise ratio versus input signal power during data transmission, it was concluded that, with signal levels used here, signal-spontaneous beat noise limited the receiver sensitivity improvement. With the fiber amplifier acting as an optical preamplifier of the receiver, the best sensitivity was -30 dBm, obtained after installing a polarizer at the fiber amplifier output to reject half of the applied spontaneous emission power. This sensitivity was 6 dB better than without the fiber amplifier, proving that the fiber amplifier can be used as a preamplifier     

Reentrant fiber Raman gyroscope

An experimental demonstration of an active reentrant fiber gyroscope is reported. Raman amplification is used to increase the number of signal recirculations in the rotation-sensing loop, which improves system sensitivity to rotation rate. A theoretical analysis of the wave mixing between counterpropagating pump and signal fields, interacting through Raman scattering in a polarization-preserving fiber, is presented     

How Close to Maximum Entropy Is Amplified Coherent Light?

We analyze the issue of entropy maximization for discrete communication channels under both mean and variance constraints. The probability-distribution solution, ξ(k), is substantially different from that of amplified coherent light, φ(k), while the corresponding entropies H(ξ) and H(φ) are found to be very nearly equal. At high signals, both H(ξ) and H(φ) converge to the continuous-channel entropy given by Gaussian statistics. Amplified coherent light can thus be considered to be very close to entropy maximum, regardless of the signal level.     

Experimental assessment of wavelength margin in 20 Gbit/s WDMsoliton system over 18 Mm distance

The authors show that the operating wavelength range of a 10 Gbit/s single-channel soliton system using sliding-frequency guiding filters over a 18 Mm distance reduces from 1.3 to 0.2 nm when the system is upgraded to 20 Gbit/s with a second wavelength channel. A record WDM propagation distance >19 Mm is obtained by tuning the channels in the centre of the operating wavelength range. This result is achieved without the use of dispersion management