Solution paths to limit interferometric noise induced performance degradation in ASK/direct detection lightwave networks

Interferometric noise, arising on the optical interference of the desired information signal and parasitic crosstalk waveforms at the photodetector, afflicts practically all lightwave communication networks, inducing unacceptable power penalties and bit error rate floors. In this paper, the induced performance degradation is quantified, both experimentally and analytically, and solution paths are identified. It is concluded that the total crosstalk level of noise generating parasitics in a generalized optical network must be held below -25 dB for a penalty of less than 1 dB-a further 2 to 4 dB may lead to network failure; otherwise, means of suppressing the noise by RF rejection at the receiver must be invoked. A number of approaches to achieving a reduction in the level of interferometric noise are presented and contrasted.