Optical generation of microwave signals is gaining relevance in recent times due to its low complexity, cost, and ability to distribute to longer distances when compared to electronic methods, especially for radio distribution systems such as next-generation phased array radars, 5G and beyond. The traditional cellular Radio Access Network (RAN), which uses digitized radio over fiber (DRoF) to transport data from base band units (BBUs) to the remote radio heads (RRHs). The DRoF systems requires complex circuitry at the RRH, including ADCs, DACs, high frequency upconverters, RF sources with good phase noise, and synchronization systems. This becomes inefficient with the introduction of mmWaves where large number of cell sites (RRHs) are required with high data rates in demand. Analog radio over fiber (ARoF) systems provide promising solution to this issue as it moves all complex processing to a the centralized BBU and low cost RRHs over long distances. This work presents optical upconversion schemes based on external modulators for generation and transport of downlink mmWave 5G NR signals in the n258 band. Although EVM performance of the optical doubler is observed to be better than that of the quadrupler system, both still falls within the limits specified standards. Optical doubling and quadrupling schemes are demonstrated with performance optimizations to match the EVM requirements specified in 3GPP standards. The scheme is extended to a multichannel downlink system, where four channels of independent data channels are upconverted simultaneously and transported to the RRH.