Abstract: Each of a series of optical amplifiers is arranged such that, in response to detecting particular stimuli occurring at an input or receipt of an adjustment start message from an upstream amplifier, adjusts certain amplifier parameters using small steps and completes the adjustment using large steps if it does not receive the adjustment start message within a predetermined period of time of starting the adjustment in response to detecting the stimuli. If the optical amplifier receives the adjustment start message, then it continues to perform the adjustment and completes the adjustment using large steps when it receives an adjustment done message from the upstream optical amplifier. At that point, the optical amplifier sends an adjustment done message to the next downstream amplifier if it is not the tail-end amplifier.

Abstract: The present invention relates generally to the field of optical transmission and particularly to a method and a system for controlling optical amplification in wavelength division multiplex optical transmission. WDM systems currently under development will have eighty or more channels, i.e., modulated optical signals with different wavelengths (known as Dense Wavelength Division Multiplexing, DWDM). These DWDM systems are demanding optical amplifiers which, especially considering the cascadation of a plurality of optical amplifiers along the transmission path of the DWDM system, have only very limited tolerances in certain parameters. Among these parameters gain flatness and gain tilt are of special importance. The present invention discloses a method and a system which make use of auxiliary optical signals having a given power level which is equal for all auxiliary signals.

Abstract: An optical amplifier is adapted to cancel the Raman gain of an optical transmission path that degrades those optical signals occupying the low end of the bandwidth such that the power is transferred from the latter signals to the optical signals occupying the high end of the bandwidth. More specifically, the optical amplifier adjusts the gain that it applies to the optical signals so that it favors the signal components at the low end of the bandwidth.

Abstract: A process for the preparation of hydrocarbons by reaction of carbon monoxide with hydrogen over a supported cobalt catalyst in a fixed bed reactor downflow operation with recycle of a heavy hydrocarbon liquid over the catalyst.