2. Operating Principle
The configuration of the proposed demultiplexing approach for subcarrier multiplexed RoF system
employing multiple-optical-source-based microwave photonic filter is shown in Fig. 1. In the CS, a
multiwavelength laser or laser diode array is used as the optical source. Different formats of the
data streams are mixed with the RF subcarrier of different frequencies, i.e., f1; f2; . . . ; fx , and are
then modulating the optical source by an external modulator. The modulated optical signal is
transmitted via the fiber link to the RAUs. In each RAU, different data with different subcarrier
frequencies need to be demultiplexed for particular customers, and a dispersive medium with
tailored delay characteristics is allocated before the modulated optical signal is recovered by the
photo-detector (PD) and then radiated by the following antenna. The frequency of the subcarrier
used and the time delay value of the dispersive medium in each RAU should be carefully designed
to make the desirable frequency located at the peak and the undesired one at the valley of the
transfer response. The architecture of the microwave photonic filter based on multiple optical
sources is shown in the dashed block of Fig. 1. The lightwave from a multiwavelength source is
modulated by microwave signal from Port 1 of the network analyzer (NA) and then sent to a
Fig. 1. Proposed system configuration subcarrier multiplexed RoF system with a multiple-opticalsource-
based microwave photonic filter.
IEEE Photonics Journal Microwave Photonic Filter as a Subcarrier Demultiplexer
Vol. 3,
2. Operating PrincipleThe configuration of the proposed demultiplexing approach for subcarrier multiplexed RoF systememploying multiple-optical-source-based microwave photonic filter is shown in Fig. 1. In the CS, amultiwavelength laser or laser diode array is used as the optical source. Different formats of thedata streams are mixed with the RF subcarrier of different frequencies, i.e., f1; f2; . . . ; fx , and arethen modulating the optical source by an external modulator. The modulated optical signal istransmitted via the fiber link to the RAUs. In each RAU, different data with different subcarrierfrequencies need to be demultiplexed for particular customers, and a dispersive medium withtailored delay characteristics is allocated before the modulated optical signal is recovered by thephoto-detector (PD) and then radiated by the following antenna. The frequency of the subcarrierused and the time delay value of the dispersive medium in each RAU should be carefully designedto make the desirable frequency located at the peak and the undesired one at the valley of thetransfer response. The architecture of the microwave photonic filter based on multiple opticalsources is shown in the dashed block of Fig. 1. The lightwave from a multiwavelength source ismodulated by microwave signal from Port 1 of the network analyzer (NA) and then sent to aFig. 1. Proposed system configuration subcarrier multiplexed RoF system with a multiple-opticalsource-based microwave photonic filter.IEEE Photonics Journal Microwave Photonic Filter as a Subcarrier DemultiplexerVol. 3,
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