Erbium-Doped Fiber Amplifier for Video Distribution Networks

Possibility of an application of Er-doped fiber amplifiers to AM-FDM or FM-FDM video distribution networks is discussed in this paper. The measured noise and modulation distortion properties of Er-doped fiber amplifiers are good enough to meet even the severe quality standards set for trunk lines. A carrier-to-noise ratio (CNR) of 57 dB for an AM-FDM transmission was measured. A second-order harmonic distortion (HD2) of less than −56 dB was measured by the monotone method (modulation depth m = 50%) and a cross modulation distortion (XM) of less than −63 dB was measured by the two-tone method (m = 25%/channel). On the basis of these values, composite second-order distortion (CSO) and XM in a 40-channel transmission were estimated as less than −57 dB and −73 dB, respectively. Significant reduction of noise and modulation distortion is made possible by optimizing the length of Er-doped fiber amplifiers and using input- and output-port isolators. The attainable distribution number can be increased remarkably by using the Er-doped fiber amplifier as a post- and/or in-line amplifier. A 16-subscriber distribution for AM-FDM and 1000 for FM-FDM are possible.