V.L. da Silva

Inhomogeneously broadened fiber-amplifier cascade for wavelength-multiplexed systems

The authors observe little or no accumulation of optical-power variations among wavelength-multiplexed signals as they traverse successive stages of a cooled, inhomogeneously broadened, erbium-doped fiber-amplifier cascade. The cascade instead exhibits separate automatic power regulation of each channel, decoupled from other channels, without the use of servo loops.<<ETX>>

Comparison of four-wave mixing and cross phase modulation penalties in dense WDM systems

The relative impact of four-wave mixing (FWM) and cross phase modulation (XPM) is investigated by treating them as noiselike impairments. We show that XPM affects wavelength-division multiplexing (WDM) transmission more strongly than FWM for the range of fiber parameters investigated.

Inhomogeneously broadened fiber-amplifier cascades for transparent multiwavelength lightwave networks

The emergence of practical fiber-amplifier chains has swiftly raised the prospect of transparent lightwave networks, in which signals travel from source to destination through a sequence of intermediate nodes without optoelectronic conversion. When such networks employ multiple wavelengths, however, some of the most substantial new research challenges are those posed by the amplifier chains themselves. Such networks suffer from accumulating interchannel power spread, from sensitivity to interamplifier loss variations, and from transient cross saturation, as the network undergoes reconfiguration. All of these difficulties effectively vanish in a chain of saturated lightwave amplifiers whose per-channel gains are decoupled by, e.g., inhomogeneous broadening. Unlike conventional, homogeneously broadened systems, saturated fiber-amplifier chains with decoupled gain dynamics provide automatic channel-by-channel power regulation, tolerance to interamplifier loss variations, and immunity to transient cross saturation. Thus, if amplifiers with such decoupled gain dynamics can be implemented in a practical way, they promise to solve-in a single stroke-several of the most substantial technological challenges facing transparent multiwavelength lightwave networks. >

Remotely pumped erbium-doped fiber amplifiers for repeaterless submarine systems

A remotely pumped erbium-doped fiber amplifier system is described that provides a record budget improvement over a non-remotely pumped system of 11 dB for 145 mW of pump power. The improvement over previously reported experiments is a result of increased pump power as well as careful optimization of the fibers utilized.<<ETX>>

Optical power equalization for multiwavelength fiber-amplifier cascades using periodic inhomogeneous broadening

Inhomogeneously broadened fiber amplifiers inserted periodically in an amplifier cascade are shown to provide significant interchannel power equalization in wavelength-multiplexed systems. Interchannel power variations in a six-amplifier cascade are reduced from 16 dB in a conventional system to about 5 dB when power equalizers are inserted.<<ETX>>

FWM penalty reduction in dense WDM systems through channel detuning

The impact of four wave mixing (FWM) as a function of the channel alignment is studied. A channel plan is proposed which minimizes FWM penalties while still agreeing with the ITU grid. We have shown that in order to demonstrate system performance under the effect of FWM it is necessary to control the alignment of the WDM channels with an accuracy significantly better than the bandwidth of the RX.

374-km transmission in a 2.5-Gb/s repeaterless system employing a remotely pumped erbium-doped fiber amplifier

A transmission distance of 374 km corresponding to a fiber loss of 73.6 dB is demonstrated in a 2.488 Gb/s repeaterless system experiment. An improvement in the power budget of 11.0 dB is obtained from a remotely pumped erbium doped fiber amplifier located 66 km from the receiver. The remote EDFA provides 15.4 dB of gain with a noise figure of 5.6 dB. Furthermore, the 145-mW of pump power, which is launched into the fiber span at the receiver, gives rise to 5.3 dB of Raman gain.<<ETX>>

Automatic gain flattening in optical fiber amplifiers via clamping of inhomogeneous gain

An Er-doped fiber amplifier with a flattened gain spectrum is obtained by incorporating the amplifier into a ring laser and making use of inhomogeneous broadening at 77 K. The results indicate several potential benefits for doped-fiber material systems that are inhomogeneously broadened at room temperature.<<ETX>>

Experimental comparison of the effect of discrete and distributed path inband crosstalk on system performance: application to predicting system performance penalties

The system performance degradations of inband crosstalk produced by distributed Rayleigh scattering and a single discrete time delayed path have been measured in the same system. Rayleigh scatter crosstalk degrades performance more than equal amounts of discrete crosstalk. By parameterizing the system bit error rate (BER) and received power, we have separated the optical and electrical noise contributions to the BER based on their intensity and crosstalk scaling. We observed behavior consistent with earlier models, but found an unexpected increase in the total optical noise. This excess noise had a very regular linear scaling with crosstalk power. Because of its well defined crosstalk and intensity scaling, this easily measured noise term can be used as a correction to established models to more accurately estimate system performance at high optical powers and low crosstalk levels.

Suppression of Dynamic Cross-saturation in Multiwavelength Lightwave Networks with Inhomogeneously Broadened Fiber Amplifiers

With the current surge of interest in multiwavelength lightwave networks [1,2], much attention has focused on the fiber-amplifier cascades they will require. Two serious performance issues have surfaced. First, due to the amplifiers’ non-flat gain spectra, less-favored wavelengths will tend to exponentially decay along the cascade, dropping eventually to undetectable levels. Second, because the amplifiers saturate on a total power basis, adding or rerouting channels in a multi-access network will tend to perturb other signal wavelengths sharing all or part of the route. Although this perturbation will generally be small in a single amplifier, it will grow rapidly along a cascade. Network reconfigurations directly involving a few wavelengths will thus generate both steady-state and dynamic power excursions for all wavelengths.