Cascaded Noise Penalty for Amplified Long-Haul Analog Fiber-Optic Links

The noise penalty (NP) metric is useful in long-haul analog link design, as it predicts degradation of the RF noise figure (NF), 1-dB compression dynamic range (CDR), and the spurious-free dynamic range (SFDR) for a single-amplifier link. We extend the NP theory to predict the cascaded NP of a multiamplifler fiberoptic link from the NP due to each of the individual amplifiers. A cascaded NP expression is derived and compared to experimental results from a 60-km link consisting of three amplifiers. The measured NP of 11.8 dB for the link matches well with our theoretical prediction. The link gain of -7 dB, RF NF of 31 dB, 1-dB CDR of 148 dB ldrHz, and of 108 dB ldrHz^2/3 are also measured and matched to predicted values for the measured NP.