Year: 2008
Miroslav Karásek, DrSc.
We designed a novel type of an optical source for distributed broad-band amplification of multiple signals based on stimulated Raman scattering in communication fibres. In difference to current commercially available Raman fibre amplifiers used in optical communication systems which apply continuous pump waves at different wavelength and powers, our approach is based on pulse time-division multiplexed pumping scheme. Disadvantage of continuously pumped Raman amplifiers is that even if the pump wavelengths and powers are optimized for flat gain spectrum, the optical signal-to-noise ratio can not be flattened due to pump-to-pump Raman amplification. This drawback can be removed by the new pumping scheme because at a given spot of the communication fibre only one pump wave is present at any time so that pump-to pump interactions are avoided. Block diagram of the new pumping source is shown in Fig. 1. Microprocessor controlled pulse generator produces four trains of high current non-overlapping pulse trains that drive 4 pairs of high-power laser diodes. The light of each pair is depolarized in polarization beam combiners (PBC) and launched into the transmission fibre via wavelength-division-multiplexed (WDM) coupler. Within the framework of a common project with CESNET, a.l.e. we manufactured two prototypes of pulse pumping sources. These prototypes are covered by the Czech Patent and Trademark Office [8, 9)]. At the same time we submitted a patent pending [10]. The performance of both prototypes was verified by transmitting 10 signals with 10 Gbit/s modulation speed over 383 km of optical fibre. Experimental and theoretical results are summarized in paper [11].
IPE carries out fundamental and applied research in the scientific fields of photonics, optoelectronics and electronics. In these fields, IPE generates new knowledge and develops new technologies.
