Method and apparatus for providing dispersion in dispersioncompensation modules

摘要

The invention relates to the field of chromatic-dispersion compensation. A circulator (30) is connected in-line with an optical fibre transmission line (50) to permit a double passage through a length of dispersion-compensation fibre (40). Light propagating in the transmission line (50) enters the circulator at a first port (10), is coupled to the dispersion-compensation fibre (40) at a second port, propagates along dispersion-compensation fibre (40) to a reflector (60), is reflected back along dispersion-compensation fibre (40) to the second port and is coupled back into the transmission line (50) at a third port (20). The compensation provided is thus double that of a single-pass arrangement. Furthermore the dispersion-compensation fibre (40) is optically pumped by Raman pumping thereby providing Raman amplification of the light. In one arrangement the reflector (40) is substantially transmissive at the pump wavelength and pumping means (e.g.a laser) optically pumps the fibre (40) through the reflector.