Abstract—Four-wave mixing (FWM) impairments become severe increasingly, since optical amplifiers are required increasingly for long-transmission distance in wavelength- division multiplexing (WDM) transmission systems. With backward propagation method, the FWM impairments can be completely compensated theoretically using detectors whose number is the same as the number of new frequencies that new generated FWMs locate on. However, we consider the compensation possibility by detecting only signal channels in this paper. Our compensation possibilities for non-degenerate case of FWM of differential phase-shift keying (DPSK) transmission have been experimentally demonstrated in a three-channel WDM system through off-line digital signal processing by coherent detection. For FWM compensation, fixed phase relationship among local oscillators (LO) after coherent detection is realized by modulating a LO light using a phase modulator. The eye penalty with P0=8dBm is improved by 3.6dB, 4.9dB, 3.2dB, respectively, for individual signal. The compensation results indicate that the input optical power tolerance is improved by more than 4dB. And the FWM degradation compensation is also considered by reducing numbers of the detectors.
Index Terms—Backward Propagation, Coherent Detection, Four Wave Mixing (FWM), Wavelength- Division Multiplexing (WDM).
J. Liang and K. Iwashita are with the Department of Electronic and Photonic Systems Engineering, Kochi University of Technology (KUT), 185, Miyanokuchi, Tosayamada-cho, Kami-shi, Kochi 782-8502, Japan (e-mail:firstname.lastname@example.org).
Cite: Jing Liang and Katsushi Iwashita, "FWM Compensation in DPSK Transmission by Reducing Detectors with Digital Coherent Detection Using Backward Propagation," International Journal of Information and Electronics Engineering vol. 1, no. 1, pp. 99-104, 2011.