SNR Enhancement of up to 9.5 Db Utilizing Four-Wave Mixing for Angle-Modulated Analog Optical Links

Angle modulation, such as phase and frequency modulation (FM/PM), has recently attracted attention for improving the fidelity of analog optical links. This is because angle can enhance signal-to-noise ratio (SNR) original message simply by increasing index or bandwidth. However, direct generation a broadband angle-modulated signal not necessarily easy. On other hand, there an indirect method, where narrowband first generated then converted to with help nonlinear devices. method often used in FM radio systems, but few reports are available on implementation this method. In paper, therefore, we propose using four-wave mixing (FWM) fiber. Since fiber naturally third-order nonlinearity (i.e., Kerr effect), it should be possible use increase bandwidth signal. We two types FWM-based methods. type, injected into dispersion-shifted (DSF) unmodulated pump wave. Consequently, one idlers via FWM double index, SNR enhanced 6 dB. second input becomes conjugate pair idler threefold type enhances 9.5 experimentally confirmed concept. The results showed that actually increased almost threefold, approximately 8.8