Intermediate amplifier for a Soliton transmission system with sliding frequency filters

摘要

A sliding-frequency guiding filter for use in the repeater of a soliton transmission system is disclosed. The filter is joined to the output of a soliton amplifier by a fusion splice and consists of a single mode fiber pigtail joined by a fusion splice to each end of an elliptical core fiber having a length L, defined by the following equation: LFSR= (1/ DELTA n) [( lambda 2/FSR)- lambda ] where FSR is the free spectral range of the filter, lambda is the wavelength of the fundamental mode in the system, and DELTA n is the difference between the index of refraction for the fundamental mode and the index of refraction for a higher order mode in the fiber of length L. Since the length, L, is difficult to obtain at the level of precision required, the filters are first measured in order to determine the frequencies of their attenuation peaks and then placed into bins in accordance with the measured wavelength of the attenuation peak. The filters are then selected for placement in a repeater in accordance with the position of the repeater in the system. IMAGE