## 7 Conclusions  
A novel inserting pilot scheme to generate a 16-tupling frequency MMW ROF system with data modulated only on the +8 th-order sideband is proposed. A \(\pm\)8 th-order sideband generator (SG) is constructed by connecting four MZMs in parallel. By adjusting the amplitude and initial phase of the RF drive signals of the MZMs, the output of the SG is \(\pm\)8 th-order sidebands. The data signal is first split into two beams: one first modulates the RF driving signal with the PM, another beam is gained by EG, and then the two beams are combined into one, which is used as the composite RF driving signal of the MZMs. By appropriately adjusting the P of the PM and the gain G of the EG, the data signal is modulated only to the +8 th-order sideband. We designed a conventional frequency 16-tupling MMW ROF system with the same structure and same parameters, except the part of the data that were modulated. For the transmission distance of 20 km with 2.5 Gpbs of data, under the condition that the Q factor is greater than 6, for our designed scheme, the power penalty of our designed scheme is 1.16 dB and the Q factor of the conventional ROF system is less than 6. This paper also analyses the effects on the BER and Q factor when the extinction ratio of the MZM, the P of the PM, and the G of the EG deviate from their theoretical values. For the case of 40 km transmission distance with a data rate of 2.5 Gpbs, the extinction ratio of the MZM is greater than 40 dB, the P varies in the range of 32.26\({}^{\circ}\)\(\sim\)36.38\({}^{\circ}\), the G varies in the range of 5.1 to 6.7, and the Q factor is greater than 6. The scheme designed in this paper can effectively solve the bit walk-off effect caused by fiber chromatic dispersion in the ROF system, greatly improve the fiber transmission distance, and has important application prospects in ROF. Conceptualization, X.C. ([PERSON]), X.C. ([PERSON]), S.D., B.L. and L.W. ; methodology, X.C. ([PERSON]) and S.D. ; software, X.C. ([PERSON]); validation, X.C. ([PERSON]) and B.L. ; formal analysis, X.C. ([PERSON]) and S.D. ; investigation, X.C. ([PERSON]); resources, X.C. ([PERSON]) and L.W. ; data curation, S.D. ; writing--original draft preparation, X.C. ([PERSON]); writing--review and editing, X.C. ([PERSON]); visualization, X.C. ([PERSON]); supervision, B.L. and L.W. ; project administration, L.W. ; funding acquisition, X.C. ([PERSON]). All authors have read and agreed to the published version of the manuscript. This research was funded by the National Key Research and Development Project (2018 YFB1404101). Not applicable. Not applicable. * (19) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Frequency-doubling photonic vector millimeter-wave signal generation from one DML. _IEEE Photon. J._**2015**, \(7\), 5501207. [CrossRef]
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