Search

We have demonstrated spectrum sharing and coexistence between a 5G network and a radio telescope without causing interference to the radio astronomer. This was realized by using optical heterodyning between two distributed feedback (DFB) semiconductor lasers as a flex-spectrum photonic RF transmitter. The 5G network was designed to identify and avoid any radio frequency interference (RFI). The generated 5G RF carrier signal is used as the primary RF data carrier for the 5G network. A second RF signal, acting as noise signal, is introduced to the 5G network using an electrical mixer. When the frequencies at the mixer ports are the same, an error signal is generated which triggers the control circuit of the 5G network to correct for the RFI by shifting the primary RF data carrier of the 5G network to a new RF carrier frequency. An impressive RFI correction time of about 3 milliseconds was recorded. [ABSTRACT FROM AUTHOR]

Radiation from a Terahertz Photomixing Antenna (PMA) involves multi-physical phenomena. We introduce a simple analytical model that combines the multi-physical phenomena in the PMA using a conventional 2-ray model. We observe reasonably close agreement between the antenna output obtained from the proposed model and the available measured results. We extend our analytical framework to incorporate the presence of an additional signal source on one of the laser beams, intended towards producing modulation in the PMA output signal. We analytically investigate the active region current density and radiated fields of the PMA. We also present a brief discussion on the efficiency of the PMA and the different factors that impact the efficiency. The output power depends on some key parameters which can be utilized to make PMAs suitable for sensing as well as wireless communication applications. [ABSTRACT FROM AUTHOR]

Vertical cavity surface-emitting lasers (VCSELs) are power-efficient optical sources for application in passive optical networks. Despite these sources having the potential of generating coherent high-frequency radio frequency signal, their application for high-order amplitude modulation formats is yet to be demonstrated experimentally. In this work, for the first time, we experimentally demonstrate a four-level pulse amplitude modulation (4-PAM) format on a photonically generated RF carrier signal using optical heterodyning of two independent VCSELs. Two low-power VCSELs were combined at an optical coupler and allowed to beat a PIN photodiode to generate a 10-GHz RF carrier. In the first demonstration, an 8.5 Gbps data signal was modulated on the photonically generated 10 GHz RF carrier. In the second demonstration, a 17-Gbps PAM-4 data signal was externally modulated onto the same VCSEL carrier, ultimately doubling the network bit rate. A simple digital signal processing (DSP) receiver was used as an alternative to costly receiver hardware to decode the transmitted PAM-4 data signal. A 24-km fiber transmission penalty of 7-dB was recorded when PAM-4 signal was photonically generated and transmitted. The penalty introduced by moving from binary transmission to PM-4 transmission was recorded to be 3-dB. [ABSTRACT FROM AUTHOR]

In this paper, the simulation of 60 GHz millimeter-wave radio over fiber link with 4-QAM OFDM modulation format at 40 Gb/s over 150 km SMF is proposed. The 60 GHz millimeter-wave signal is generated by the optical heterodyne method. Coherent detection has been used at the receiver to down-convert millimeter-wave signal to IF band. Introduction of the OFDM modulation in RoF-based system realizes the benefits of higher order modulations (such as 4-QAM, 16-QAM, etc.) to ensure the good spectral efficiency and multi-gigabit access. The performance of the system is analyzed by Q-factor and BER by which it can be shown that the best results are obtained at the input power of 10 dBm. The simulation results clearly demonstrate the feasibility of this 4-QAM OFDM RoF system over 150 km fiber link. [ABSTRACT FROM PUBLISHER]