New linearization technique for analog fiber-optic links

Photonic Applications has developed a novel linearization technique for analog fiber-optic links, which is based on the feedforward approach and uses a single optical source. In this approach, the feedforward correction is accomplished using a portion of the laser light coupled into the feedforward modulator to which the error signal is applied. The modulated optical signal from the feedforward modulator is then combined with the output signal from the primary modulator with an optical coupler. The elimination of coherent effects at the output coupler, including phase noise of the optical source, is accomplished by impressing the proper phase modulation signal to one of the optical paths. This is not a simple phase compensation servo system. This approach has been demonstrated in the laboratory for both CATV and typical RF applications.