Abstract: A method is presented for calculating the Rayleigh backscattered signal (RBS) for an inhomogeneous fiber span amplified by a counter-propagating pump source, the fiber span being a concatenation of sections of different types of fiber. The method may be used to determine the Raman gain coefficients of each fiber section within the inhomogeneous fiber span. In addition, when the Raman gain coefficients for the fiber types are known, the method may be used to determine the fiber type of a section, if unknown.

Abstract: An agile network is provided with a layered control system for maintaining a network-wide target performance parameter (e.g. power) along all end-to-end connections. A connection is controlled at the physical layer using optical control loops that have a concatenated response based on a set of loop time constants. The network is separated into gain based span loops and power based switch loops; each link has a gain profile, and requires a per-wavelength power target as the output power target for the switch loop at the start of the link. Use of achievable gain for the span loops allow to optimize the performance of the link. Use of individual achievable power targets allows each switch loop to autonomously ramp on and off channels without causing interference with existing and other ramping channels. A loop control uses a model-based rules block, to distribute control signals to an optical section encompassing a plurality of optical components.

Abstract: A Raman module comprises a detecting unit for measuring the output power of a WDM signal traveling along a fiber section, and a spectral gain estimating unit for determining an estimated vector gain Gainmeas based on the output power alone. The Raman pump signal is controlled with a gain GainRA evaluated based on the estimated gain Gainmeas so that all channels have a similar gain. The spectral gain estimating unit comprises a fiber gain model and an input signal adjust unit. The model receives the output power, assumes a predicted input power for each channel and provides a corresponding estimated output power for each channel. The input signal adjust unit adjusts the predicted input power based on an error signal provided by the model. The gain is then calculated from the predicted input powers and the estimated output powers. The detecting unit demultiplexes a fraction of the WDM signal into n sub-band and detects sub-band optical power PB1, . . . PBn.