Broadband gain flattened Raman Amplifier to extend operation in the third telecommunication window

摘要

Fibre Raman amplifiers can provide gain for the second and third telecommunication windows operating throughout the complete window of low loss of optical fibre to extend existing and future telecommunication systems. These broadband Raman amplifiers in excess of 100nm in bandwidth can be produced using pumping with multiple wavelengths [1, 2, 3]. Using 24 high power laser diodes with dense multiplexing, optimized wavelength channel spacing and power ratios, a gain of 6.5 dB with a gain fluctuation of +/- 0.5dB over a 100nm bandwidth was achieved [3]. The dense multiplexing of such a large number of diodes results in considerable losses and complications. An alternative way is to use fewer but higher power pumps. A 100nm Raman high gain amplifier was reported using triple wavelength pumping [2]. However, the gain variation was as high as +/- 2.5dB for the 26dB gain as a result of using large separation between pump wavelengths. The major gain ripple was on the scale of 20-30nm, and hence can be compensated for using similar techniques applied to Erbium amplifiers. The specific requirements for Raman gain equalizing filters are that they have to be low loss and suitable for broadband operation.