Cascaded Modulation Scheme and Its Application to Optical Multi-Channel Signal Transmission Systems

Koji KIKUSHIMA  Toshihito FUJIWARA  Satoshi IKEDA  

IEICE TRANSACTIONS on Communications   Vol.E90-B   No.2   pp.195-208
Publication Date: 2007/02/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.2.195
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fiber-Optic Transmission for Communications
optical transmission systems,  optical modulation scheme,  CATV,  

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This paper starts by describing the advantages of cascaded modulation, i.e., using multiple concatenated external modulators to modulate CW (Continuous Wave) light. Next, the paper examines computer simulations of the resulting modulated light waveform shapes and intermodulation distortion values to elucidate the basic modulation characteristics of a cascaded modulation scheme. Examples of applying cascaded modulation to a multi-channel optical signal transmission system are shown, and the characteristics are clarified by optical transmission experiments. For example, the dependency of the signal quality on the modulation depth values of each external modulator is clarified. Moreover, experiments show that cascaded modulation permits the remote insertion of local broadcast programs into wide area broadcast programs. Last, the paper shows that cascaded modulation offers better modulation properties than the conventional single modulation approach.