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2                                                 Transport aspects



























                           Figure 9-23 – Measured EVM as a function of optical path loss to evaluate
                                       the available dynamic range of optical path loss


            Figure 9-24 shows the measured EVM as a function of input RF power to evaluate the minimum input RF
            power. In the cases of E-BTB and E-BTB with LNA, in which the LNA inside the RoF transmitter was directly
            connected to the LTE VSA, it is estimated that the EVM thresholds of 8 and 12.5% were obtained when the
            input RF powers were about −76 and −82 dBm, respectively. Also in the case of optical BTB, in which the
            RoF  transmitter  was  directly  connected  to  the  RoF  receiver  without  any  optical  amplifier  (the  received
            optical power was fixed at −10 dBm for the RoF receiver), similar results were observed. As increasing the
            input RF power level from −62 to −57 dBm, a slight EVM degradation caused by LD clipping was observed.
            Thus, no significant degradation of the signal quality due to the introduction of the RoF transmitter and
            receiver was observed in the input RF power range from −85 to −62 dBm. In the case of 36 dB optical path
            loss, it is estimated that the EVMs of less than 8% for 20 MHz-bandwidth 64-QAM mapped signals were
            obtained at the input RF powers of more than −67 dBm. Similarly, it is also estimated that the EVMs of less
            than 12.5% for 20 MHz-bandwidth 16-QAM mapped signals were obtained at the input RF powers of more
            than −72 dBm. From these results, it is necessary to manage the input RF power level in order to achieve
            sufficient uplink transmission performance and to reduce overall system degradations.




























                           Figure 9-24 – Measured EVM as a function of input RF power to evaluate
                                               the minimum input RF power




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