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In this paper a review on different signal generation techniques for Radio over Fiber systems is presented. Radio over fiber has become a conspicuous contender in upcoming high data rate demands from household and enterprises users. Radio signals or waves can be generated back from optical signals at RAU (radio access unit) so that they may be transmitted to mobile stations. This generation is first assembled into different categories on the basis of some similar parameters, various aspects of each category are given and then a comparison between different aspect of each technique is summarized in table. Analysis of these techniques on the basis of ranges of radio frequencies that can be generated is also proposed in this paper. [ABSTRACT FROM AUTHOR]

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]

We demonstrate real-time broadband multi-Gb/s electrical RF synthesizer-free millimeter-wave (MMW) signals generation and wireless transmission at the 5G new radio (NR) frequency band of 47 GHz based on analog radio-over-fiber (A-RoF) fronthaul. This is enabled by a low noise, highly correlated, monolithic C-band semiconductor InAs/InP quantum-dash (QDash) dual-wavelength distributed feedback (DW-DFB) laser. One laser mode is encoded using 4-/6-GBaud multilevel quadrature amplitude modulation (M-QAM) (16-/32-/64-QAM) baseband data signals, the other lasing mode is used as an optical local oscillator for optical-heterodyne remote up-conversion to a MMW carrier of 47.27 GHz. Consequently, optical baseband modulated data signals with data capacity up to 36 Gb/s (6-GBaud × 64-QAM) are transmitted through back-to-back (BtB) and 25-/50-km of standard single mode fiber (SSMF) before the MMW carrier is optically synthesized remotely for free space wireless data transmission and detection over up to 9-m. The end-to-end MMW-over-fiber (MMWoF) wireless link is thoroughly characterized exhibiting promising error-vector-magnitude (EVM) and bit-error-rate (BER) values. The 4-/6-GBaud 16-QAM MMWoF wireless links achieve EVMs down to 6.32%/7.33%, 6.71%/7.78%, and 7.35%/8.91% through BtB, 25-km, and 50-km SSMF, respectively. Similarly, the EVM for 32-QAM and 64-QAM links is observed to be 5.56%/6.56% and 6.05%/6.62%, respectively. Moreover, in each case, the calculated BER is below the forward error correction (FEC) limit of 3.8 × 10−3. The results corroborate the potential and viability of the QDash DW-DFB laser as a simple, efficient and cost-effective alternative to individual laser sources for deployment in broadband photonic MMWoF fronthaul systems of 5G wireless networks. [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 provide an efficient solution for future millimeter wave (mm-wave) wireless systems. The phase noise of the photo-generated mm-wave carrier limits the performance of such links, especially, for the transmission of low subcarrier baud rate multi-carrier signals. In this work, we present three different techniques for the compensation of the laser frequency offset (FO) and phase noise (PN) in an optical heterodyne A-RoF system. The first approach advocates the use of an analog mm-wave receiver; the second approach uses standard digital signal processing (DSP) algorithms, while in the third approach, the use of a photonic integrated mode locked laser (MLL) with reduced DSP is advocated. The compensation of the FO and PN with these three approaches is demonstrated by successfully transmitting a 1.95 MHz subcarrier spaced orthogonal frequency division multiplexing (OFDM) signal over a 25 km 61 GHz mm-wave optical heterodyne A-RoF link. The advantages and limitations of these approaches are discussed in detail and with regard to recent 5G recommendations, highlighting their potential for deployment in next generation wireless systems. [ABSTRACT FROM AUTHOR]

Abstract Background Carrier generation based on optical heterodyning techniques where a beat signal is generated from the mixing of two light sources can be interesting solution due to ease on tunability. The free running heterodyning scheme benefits with a very wide tuning capability and the generated carrier can be freely adjusted. However, the drawbacks come in the form of frequency stability. Heterodyning of two optical frequencies coming from a single laser cavity has shown its potential on improvement of frequency stability. Methods The impact of the laser parameters (i.e., optical power and linewidth) on the quality of the generated carrier (i.e., phase/frequency stability and carrier-to-noise ratio) is analyzed for a 25×64 elements PAA system. An optically generated carrier signal using a dual-frequency distributed feedback waveguide laser in ytterbium doped aluminum oxide (Al2O3:Yb3+) is analyzed and experimentally demonstrated in this paper. The carrier signal is used for downconversion of the signal received from a phased array antenna (PAA) of a DVB-S (Digital Video Broadcasting-Satellite) system. Results An optical frequency locked loop (OFLL) to stabilize the generated carrier is implemented which results in a microwave frequency at ∼14 GHz with a phase noise of -75 dBc/Hz at 1 MHz offset from the center frequency and gives a loop settling time of 12 μs. By using the proposed OFLL, the long term and the short term frequency stability of the generated carrier has an Allan deviation of more than 1×10−10 for an averaging time of 1000 s and a standard deviation of 39.4 kHz, respectively. The lasers linewidth should be in the order of tens of Hz, with a maximum relative intensity noise (RIN) of -107 dB/Hz and a minimum optical power of 0.94 mW. Conclusions The optical carrier generation by OFLL using a DFL to comply with the requirements of the standard carrier used in commercial LNBs has been investigated. The detailed analysis of the OFLL scheme is presented. Specifications requirement on carrier power, linewidth and relative intensity noise of the optically generated carrier have been addressed. The optical carrier generation is experimentally demonstrated and the requirements on CNR have been determined by measuring the noise floor and the optical carrier power. The measured values are compared with the calculated values and found to be very close.

We experimentally demonstrate a real-time optical heterodyning and envelope detection-enabled orthogonal frequency-division-multiplexing-based Q-band radio-over-fiber (OFDM-RoF) system. Envelope-detector-based down-conversion is applied to the mobile terminal (MT), which makes MT insensitive to the phase noise of the beating millimeter wave signal and enables the generation of RoF signals using two free-running non-narrow line-width distributed feedback lasers in the central office. The error-free transmission real-time Reed-Solomon- coded 16-quadrature-amplitude modulation(16-QAM)-OFDM-RoF signals with a net bit rate of 1.2 Gb/s at 35/40 GHz over 4.5-km single-mode fiber (SMF) and 0.8-m wireless distance is reported in this paper. Additionally, the transmission performance of the signals at 35 GHz with the net bit rate from 1.5 to 5.9 Gb/s is also investigated by offline digital signal processing approaches. It indicates that the BER of the signal with the net rate up to 4.4 Gb/s after the SMF and wireless link transmission is below a 7% hard-decision forward error correction (FEC) threshold of 3.8 × 10-3.

THz wireless signals have become of interest for future broadband wireless communication. In a scenario where the wireless signals are distributed to many small remote antenna units, this will require systems which allow flexible frequency tuning of the generated THz carrier. In this paper, we demonstrate experimentally the implementation of two tuning methods using an optical frequency comb generator for coherent optical frequency tuning in THz wireless-over-fiber systems. The first method is based on using a photonic integrated circuit optical phase lock loop (OPLL) subsystem implemented as a high quality optical filter for single comb line selection and optical amplification. The OPLL generates an optical carrier, which is frequency and phase stabilized in reference to one of the optical comb lines with a frequency offset precisely selectable between 4 and 12 GHz. The second method is based on optical single sideband suppressed carrier (SSB-SC) modulation from the filtered comb line using an optical IQ modulator. With this technique, it is possible to suppress the other unwanted optical tones by more than 40 dB. This generated optical carrier is then heterodyned with another filtered optical comb line to generate a tuneable and stable THz carrier. The full system implementations for both methods are demonstrated by transmitting THz wireless signal over fiber with 20 Gb/s data in QPSK modulation. The system performance and the quality of the generated THz carrier are evaluated for both methods at different tuned THz carrier frequencies. The demonstrated methods confirm that a high quality tuneable THz carrier can easily be implemented in systems where dynamic frequency allocation is required. [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]

We experimentally demonstrate a real-time optical heterodyning and envelope detection-enabled orthogonal frequency-division-multiplexing-based Q-band radio-over-fiber (OFDM-RoF) system. Envelope-detector-based down-conversion is applied to the mobile terminal (MT), which makes MT insensitive to the phase noise of the beating millimeter wave signal and enables the generation of RoF signals using two free-running non-narrow line-width distributed feedback lasers in the central office. The error-free transmission real-time Reed–Solomon- coded 16-quadrature-amplitude modulation(16-QAM)-OFDM-RoF signals with a net bit rate of 1.2 Gb/s at 35/40 GHz over 4.5-km single-mode fiber (SMF) and 0.8-m wireless distance is reported in this paper. Additionally, the transmission performance of the signals at 35 GHz with the net bit rate from 1.5 to 5.9 Gb/s is also investigated by offline digital signal processing approaches. It indicates that the BER of the signal with the net rate up to 4.4 Gb/s after the SMF and wireless link transmission is below a 7% hard-decision forward error correction (FEC) threshold of 3.8 × 10−3. [ABSTRACT FROM PUBLISHER]

This paper presents a new concept for the study of spatio-temporal generation regimes in which several time scales coexist in the radiation (one of which is related to the cavity round-trip time). The essence of the concept is that the time dependence of the intensity is investigated in two dimensions, one of which corresponds to the evolution over successive cavity round trips. It is shown that fiber lasers of various types, e.g., quasicontinuous lasers and passively and actively mode-locked pulsed lasers, have a variety of spatio-temporal generation regimes. The possibility of experimental detection of localized structures, including solitons, in fiber laser radiation is demonstrated. The prospects of the proposed approach are discussed. [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]

Higher capacity wireless access networks are required to serve the growing demands for mobile traffic and multimedia services. The use of sub-THz carrier frequencies is a potential solution for the increased data demands. This paper proposes and demonstrates experimentally the photonic generation of a multiband signal for sub-THz wireless-over-fiber transmission at up to 100 Gbit/s (20 Gbit/s in each band) using the full spectrum 220– 280 GHz for downlink wireless transmission and an uplink with 10 Gbit/s on-off keying. By using an optical frequency comb generator (OFCG), five optical tones spaced by 15 GHz are selected and split into odd and even optical subcarriers modulated separately using 10 Gbaud quadrature phase shift keying with Nyquist bandwidth achieved by using root raised cosine filtering with 0.01 roll off factor. These optical subcarriers are combined and transmitted over 10 km of fiber to the remote antenna unit (RAU). The optical bands are then filtered and transmitted separately at the RAU in a wireless channel. The received sub-THz band is down-converted to the intermediate frequency and digital signal processing (DSP) is employed at the receiver to measure the bit error ratio (BER). The performance is also evaluated to investigate the impact of the uplink on the downlink optical transmission. The receiver link budget and wireless distance for acceptable BER are also explored. The proposed system aims to distribute sub-band THz signals for short range indoor mobile units. The overall transmission capacity is increased by transmitting it as a multiband, which also reduces the bandwidth requirements on opto-electronic devices. [ABSTRACT FROM PUBLISHER]

Generation of microwave signals by optical heterodyning has been an active area of research in the field of Microwave Photonics. Though this approach offers great flexibility in choosing the microwave frequency, issues related to frequency stability and phase noise performance are inherent to it. The effect of laser phase noise on heterodyned output is mathematically analyzed, simulated and practically demonstrated. Design of hardware-efficient Optical Phase Locked Loop (OPLL) that overcomes the issues of phase noise and frequency instability is proposed. Frequency stability and phase noise tracking achieved by the proposed OPLL is demonstrated experimentally. Highly stable microwave signals, exhibiting phase noise as low as −105 dBc/Hz at 10 KHz offset (limited by the phase noise of the reference source used in the experiment), are successfully generated by the proposed approach. The generated microwave signals have been shown to be devoid of spurious components and harmonics. [ABSTRACT FROM AUTHOR]

A self-referenced frequency response measurement of high-speed photodetectors (PDs) is proposed and demonstrated based on optical frequency-detuned heterodyne method. Our method provides a narrow linewidth and wide-bandwidth optical stimulus consisting of acoustooptic frequency shifting and two-tone phase modulation in a Mach-Zehnder interferometer, and achieves the self-referenced frequency response measurement of high-speed PDs without the need for correcting the power variation of optical stimulus. Moreover, it allows multiplied measuring frequency range and avoids any bias drifting problem. Frequency responses are experimentally measured for a commercial PD, which agree well with the results obtained by the conventional methods. [ABSTRACT FROM PUBLISHER]

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]

The spectra of capillary waves were studied for bidistilled water and a NADH aqueous solution, and their dynamics under electromagnetic irradiation in the millimeter range was determined at different space frequencies of the surface wave k. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate techniques for efficient RF carrier extraction and reuse in an orthogonal frequency-division multiplexing (OFDM) radio-over-fiber (RoF) system. In this system, an RF carrier is generated in the base station through optical heterodyning between two uncorrelated optical carriers delivered from the central office. The RF down conversion is accomplished by mixing the intermediate frequency signal with the extracted RF carrier. This not only relaxes the phase noise requirement on the RF carrier, but also minimizes signal-signal beat interference. We demonstrate an RoF network carrying 8.2 Gb/s QPSK data in OFDM modulation format for both downlink and uplink, which share the same RF carrier, which avoids the need of an additional RF oscillator in the customer unit. [ABSTRACT FROM PUBLISHER]

A tunable microwave generation is demonstrated by monolithically integrated photonic chip, which combines a mirror section and two distributed feedback (DFB) lasers. The focus ion beam technology was employed to achieve high-quality air/semiconductor slab for the mirror. Two DFB lasers (named slave and master lasers, respectively) can operate in a single fundamental mode when they are individually pumped. A microwave signal with the differential frequency between the two lasers can be obtained through optical heterodyning. A tunable microwave signal up to 25.5 GHz can be generated by adjusting the injected currents of the two DFB lasers. A four-wave mixing spectrum was measured and the linewidth of the generated radio frequency signal is 1.9 MHz. [ABSTRACT FROM PUBLISHER]

We demonstrate a bidirectional millimeter-wave (mmW) radio-over-fiber system based on the use of a p–i–n photodiode (PD) biased in the nonlinear regime. Since frequency down-conversion and photodetection are carried out by a single photodiode, the base station (BS) architecture is simplified. Down-link transmission employs an optical heterodyning technique for mmW generation and remote local oscillator (LO) delivery to BSs. The up-link scheme uses the electrical port of the PD as an input for optoelectronic mixing with the remotely delivered LO. Up-link and down-link have been successfully demonstrated for 397 Mbps and 794 Mbps binary phase-shift keying complying with the 60 GHz ECMA 387 standard. Error vector magnitude measurements and theoretical analysis are discussed as regards optimal PD bias conditions. It is shown that PD can be used in this bidirectional system without any switching of the PD bias. [ABSTRACT FROM PUBLISHER]

In this paper, theoretical model on phase noise in self-heterodyning optical system for mmW generation is proposed. Phase noise is impacted by optical path difference between both optical tones and laser source coherence time, but also by RF generators phase noise. Phase noise measurements of the mmW signal and RF sources have been realized to discuss the validity of the model. Based both on the theoretical approach and on the phase noise characterizations, an error vector magnitude (EVM) model is developed to quantify the impact of the optical self-heterodyning output phase noise on up-converted broadband digital signal (ECMA 387 standard). [ABSTRACT FROM PUBLISHER]

The performance of wireless signal generation and detection at millimeter-wave frequencies using baseband optical means is analyzed and experimentally demonstrated. Multigigabit wireless signal generation is achieved based on all-optical orthogonal frequency division multiplexing (OFDM) and photonic upconversion. The received wireless signal is optically modulated and detected using digital coherent detection. We present a theoretical model, ultimate performance limitations based on simulations as well as experimental validation of the proposed architecture. In order to demonstrate the RF scalability and bit-rate transparency of our proposed approach, we experimentally demonstrated generation and detection in the 60 GHz and 75-110 GHz band of an all-optical OFDM quadrature phase shift keying, with two and three subcarriers, for a total bit rate over 20 Gb/s. [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]

A novel technique to modulate one carrier in a dual-carrier millimeter-wave (mm-wave) photonic system is presented and experimentally evaluated. The technique utilizes the polarization dependence of an optical phase modulator and the properties of optical heterodyning and is demonstrated for both amplitude- and phase-modulated mm-wave signal outputs. Experimental verification of the technique is presented with transmission of up to 2.5-Gb/s nonreturn-to-zero data, multilevel quadratic-amplitude modulation, and IEEE 802.11a WLAN data signals on a 40-GHz carrier over optical fiber and wireless transmission. The tolerance for fiber dispersion is investigated, and penalty-free transmission over 44 km is verified. The linearity of the system is evaluated by measuring the spurious-free dynamic range. [All rights reserved Elsevier]. [ABSTRACT FROM PUBLISHER]

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]