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]

Optical heterodyne analog radio-over-fiber (A-RoF) links can provide a cost-effective and spectrally efficient solution for the generation and distribution of millimeter-wave/Terahertz (mm-wave/THz) carriers for the next-generation wireless systems. The use of an optical frequency comb (OFC) source in such a system can facilitate carrier generation free from frequency fluctuation. However, decorrelation between tones, due to path length difference, can lead to phase noise on the generated mm-wave carrier — limiting the performance of low subcarrier spacing multi-carrier signals specified in the 5G standard. In this work, we analyze the effect of comb tones decorrelation due to path length difference on the performance of 5G compatible 244 kHz subcarrier spacing 59 GHz OFDM signal over an optical heterodyne A-RoF link using a gain switched laser (GSL) OFC source. Furthermore, we demonstrate the ability of the OFC-based A-RoF optical/mm-wave system to support flexible and interoperable mm-wave functionality through signal generation at 27 GHz, 43 GHz and 59 GHz using different pairs of GSL OFC tones for remote heterodyning. The capability of multi-frequency 5G NR compatible mm-wave signal generation and potential for photonic integration make the demonstrated GSL OFC based optical heterodyne A-RoF system a suitable candidate for deployment in the next generation wireless systems. • Successful generation of multi-frequency 5G NR subcarrier spacing compatible mm-wave signals at 27, 43 and 59 GHz frequencies using the same gain-switched laser optical frequency comb source device over an optical heterodyne analog radio-over-fiber link is demonstrated. • A detailed phase noise analysis of the generated mm-wave carriers is provided highlighting the importance of coherence in such systems. • The capability of multi-frequency 5G compatible mm-wave signals generation and potential for photonic integration make the demonstrated system a suitable candidate for deployment in the next generation wireless systems. [ABSTRACT FROM AUTHOR]

A novel model for pipeline optical sensor and monitoring unit is been proposed through this paper, which consist of fiber Bragg grating array functioning as sensor unit and base station consist of monitoring and transmission unit. Monitoring unit smartly converts optical signal to electrical signal through optical heterodyning and detects the variation of reflected central frequency of each FBG through data processing. Frequency spacing between reflected optical signals are elegantly adjusted so that number of peaks in electrical domain spectrum are equal to number of FBGs. This architecture is verified theoretically, successfully simulated and analyzed. [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]

This article presents the investigation of frequency and temporal coherence properties of distributed Bragg reflector laser. In this scheme, a square-waveform voltage is applied to the phase section of the laser to tune optical wavelength, and delayed optical heterodyne technique is used for the analysis of spectral characteristics. Experiments show that lightwaves emitted from the same active region asynchronously are partially frequency and temporal coherent. When the two wavelengths are closer, the two waves are strongly coherent, and the coherence properties get weak as the delay time increases. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:822–825, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25031 [ABSTRACT FROM AUTHOR]

An all-optical premodulation-free microwave frequency up/down-conversion method is presented based on stimulated Brillouin scattering in optical fibers for bidirection radio-over-fiber systems. Through optical heterodyning between the modulated optical carrier and the Stokes light, the microwave signal of 1.5 GHz is up-converted to 9 and 12 GHz, and the microwave signal of 9 GHz is down-converted to 1.5 GHz. The unexpected microwaves are more than 7 dB suppressed by loading the signal to convert with the optical-carrier-suppressed modulation. [ABSTRACT FROM AUTHOR]

A simple photonic scheme is presented to generate microwave/mm-wave sources by utilizing the optical heterodyne technique between an optical carrier and its Stokes light coming from stimulated Brillouin scattering (SBS) in optical fibers. Stable microwave sources with the frequencies of about 10.56 and 21.71 GHz are experimentally realized using the first- and second-order SBS frequency shifts based on standard single-mode fibers. This scheme is laser cavity or modulation free and of frequency-multiplied capacity to achieve higher microwave and millimeter-wave sources. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1203–1206, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24285 [ABSTRACT FROM AUTHOR]

This paper describes a novel system for measuring the frequency response of electrooptic intensity modulators at millimeter-wave frequencies. The system measures ∣S21∣ in decibels electrical. In it, the electrical input signal to the modulator is generated by heterodyning two tunable lasers. The output of the modulator is then down-converted to a microwave frequency at which the output is easily measured. Measurements have been made up to 78 GHz using a 55-GHz photodiode as the mixer for the two lasers. In addition, our system tracks any frequency variations in the out- puts of the lasers. Our system can also measure the linear response of the modulator if it is operated in nonlinear regions since it can reject higher order harmonics, due to nonlinearities, generated in the modulator. [ABSTRACT FROM AUTHOR]

Abstract: We present the study of collinear light scattering by relatively short acoustic pulses in birefringent crystals providing that both the acoustic attenuation and spreading the acoustic beam are allowed for. The exact and closed analytical model for the phenomenon described is developed. The peculiarities of collinear acousto-optical interaction in the cells made of lithium niobate single crystal are considered for the traveling-wave regime. The feasibility of applying such an effect to perform a coherent optical processing of ultra-high frequency (UHF) radio-wave electronic pulses is analyzed and the corresponding opto-electronic algorithm is elaborated. The results of preliminary experiments, exhibiting an opportunity for the data processing in anti-radar system, are presented. [Copyright &y& Elsevier]

The photonic technique is a feasible solution for generation of high-frequency RF carrier signals, attracting considerable attention in the past decades. In the laser gain-switching technique for photonic generation of high-frequency RF carrier signals, two optical lines, separated by the desired RF carrier frequency are filtered from the generated optical frequency comb. One of the filtered comb lines is externally modulated with an optical modulator, while the other acts as an optical local oscillator signal. In this paper, we report on the effects of optical local oscillator signal power on the RF carrier signal and the baseband signal of a fronthaul network using a sub-60 GHz RF carrier signal generated from a gain-switched, low-power, VCSEL-based optical frequency comb source. A 56-GHz RF carrier signal was generated by filtering out from the generated optical frequency comb, two optical lines with wavelength difference corresponding to the desired RF carrier frequency. The resultant RF carrier signal was photonically amplitude-modulated with 16-Gbps data before transmitted over 21-km of SSMF. In this study, we investigated the effects of attenuating the optical local oscillator signal power below the modulated optical carrier signal power. It was found that the RF carrier power is reduced when attenuating the optical local oscillator power below the power of the modulated optical carrier signal. However, the performance of the baseband signal is improved. It was found that by optimally establishing a power ratio between the two filtered optical signals, a power gain of up to 18-dB can be achieved to reach an error-free BER of 10−9 for the baseband signal. For the RF signal at the beating frequency, it was found that reducing the power of the modulated optical carrier signal below the power of the optical local oscillator signal could results in power improvements. [ABSTRACT FROM AUTHOR]

• The dynamic oscillatory radiation force optical heterodyning method is introduced • This method is based on the oscillatory behavior of the optical force induced by amplitude modulation • Exact mathematical series expansions for the dynamic force are derived and computed • Examples for dielectric cylinders in TM or TE polarized are considered • The results could pave the road for the development of optical oscillatory heterodyne tweezers In contrast with the optical radiation force induced by conventional lasers of continuous mono-frequency wave-fields, a dynamic or oscillatory mode arises when a beating effect caused by intensity changes over time (i.e., amplitude modulation) occurs. The purpose of this analysis is directed toward examining theoretically the dynamic (oscillatory) radiation force in optical heterodyning, caused by interfering/mixing two electromagnetic/optical plane waves driven at slightly different frequencies. The example of a dielectric cylinder material having a circular geometric cross-section is considered. Based on the integration of Maxwell's stress tensor over the surface of the object in the near-field, the modal expansion method in cylindrical coordinates is used in conjunction with the short-term time average to obtain mathematical series for the longitudinal dynamic optical radiation force per-length (i.e. acting along the direction of wave propagation). The cases of incident TM and TE polarized plane progressive waves are considered. Numerical illustrative results for the dimensionless dynamic radiation force function are performed with particular emphasis on changing the size parameter of the cylinder as well as the normalized difference-frequency and time parameters. The results show that the total force is not the mere sum of the components originated by the primary waves. There is an additional cross-term factor related to the dynamic component which cannot be neglected, suggesting that the radiation force phenomenon using beating optical waves is slowly time-varying (oscillatory). Moreover, a resonance splitting effect in the plots of the dynamic radiation force is observed and discussed. The present analysis has the potential to open a novel method in the development of dynamic/oscillatory optical heterodyne tweezers and tractor beams for particle manipulation and characterization. [ABSTRACT FROM AUTHOR]