Abstract
This work presents an optical up-conversion system with frequency quadrupling for wavelength-division-multiplexing (WDM) communication systems using a dual-parallel Mach-Zehnder modulator without optical filtering. Four-channel 1.25-Gb/s wired fiber-to-the-x (FTTx) and wireless radio-over-fiber (RoF) signals are generated and transmitted simultaneously. Moreover, the decline in receiver sensitivities due to Mach-Zehnder modulator bias drifts is also investigated. Receiver power penalties of the 20-GHz up-converted WDM signals and baseband (BB) FTTx signals are less than 1 dB when bias deviation voltage is less the 20% of the half-wave voltage. After transmission over a 50-km SSMF, the receiver power penalties of both the BB and 20-GHz RF OOK signals are less than 1 dB. Notably, 60-GHz optical up-conversion can be achieved using 15-GHz radio frequency (RF) components and equipment.
Highlights
Optical millimeter-wave generation and up-conversion are essential to Radio-over-Fiber (RoF) communication systems [1,2,3,4,5,6,7]
Frequencies of millimeter-wave generation and up-conversion systems are still restricted by the frequency response of LiNbO3 modulators, which is typically less than 40 GHz
The Mach-Zehnder modulator (MZM) has been used for several decades, bias drift, which affects MZM performance, remains an important issue when the MZM is biased at the maximum or minimum transmission point
Summary
Optical millimeter-wave generation and up-conversion are essential to Radio-over-Fiber (RoF) communication systems [1,2,3,4,5,6,7]. Many schemes have recently been developed for optical millimeter wave generation with frequencies exceeding two times that of the RF driving signals [3, 6, 9, 10, 11, 13] Via these frequency tripling and quadrupling techniques, optical millimeter-wave signals can be generated using low-frequency RF components and equipment which markedly reduces the entire system costs. Some of these proposed systems require two cased external modulators, which increase system complexity and cost. Four-channel BB 1.25-Gbits/s WDM millimeter-wave signals are simultaneously up-converted with optical carrier suppression using only one external modulator without narrowband optical filtering. The impact of the MZM bias drift on the performance of BB and RF signals is investigated
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