With the continuous development of laser communication technology, UAV-based laser communication ATP system is gradually developing towards lightweight and miniaturization. This paper presents a multiplex system based on fourquadrant detector, which integrates tracking and communication. By using a four quadrant detector, the precision tracking detector and communication detector in conventional laser communication systems are combined into one. This can reduce the weight, size and power consumption of the fiber optic terminal. The receiving unit uses the diversity receiving and merging function of the four quadrant detector to improve the signal-to-noise ratio and improve the communication performance.
KEYWORDS: Microwave photonics, Signal attenuation, Image processing, Scattering, Signal processing, Optical modulators, Optical amplifiers, Electrooptic modulators, Signal generators, Signal detection
The electrical mixer is limited by operation bandwidth and parallel processing capacity, and is suffering from increasingly serious electro-magnetic interference. By introducing photonic properties, microwave photonic technology has many advantages compared to the traditional microwave technology, such as low loss, large bandwidth, high parallel processing capacity, anti-electromagnetic interference and so on. In this work, a Stimulated Brillouin Scattering (SBS) based microwave photonic mixer with high image rejection capacity is proposed. Due to the high wavelength-selectivity and wideband tenability of the SBS process, the image rejection ratio of the mixer exceeds 40dB over the IF range of 80 MHz to 2 GHz and the RF range of 2 to 40 GHz.
Distributed optical fiber sensors have the advantages of corrosion resistance, anti-electromagnetic interference and adaptability to extreme environments. They can be used in perimeter security, pipeline monitoring, seismic detection and other fields. A novel optical fiber sensor called microwave frequency fiber interferometer has been proposed for low frequency sensing applications such as submarine seismic monitoring. However, the MFFI can only achieve integrated sensing and cannot achieve distributed localization of disturbances. In order to solve the problem that MFFI cannot achieve distributed localization and make it more suitable for long distance sensing applications, we propose a dual wavelength MFFI system based on wavelength division multiplexing to achieve distributed localization through time delay estimation algorithm. Our proposed system and algorithm make up for the inability of MFFI to achieve distributed localization and can be used in more sensing applications.
The contradiction between the limited bandwidth of optical communication and the escalating demand for faster communication speed poses an urgent problem that needs to be addressed. To enhance the transmission bandwidth of optical communication systems and reduce transmission losses, this paper proposes a vertically structured thin film lithium niobate modulator with T-electrodes. Through simulations, the electrode's structural parameters are optimized to minimize microwave losses and increase transmission bandwidth. The results demonstrate that compared to traditional T-electrode modulators, the vertical T-electrode modulator with optimized structure parameters (t=5μm, r=45μm, s=2μm, c=5μm, h=4μm) exhibits an increased modulation bandwidth from 80GHz to 100GHz while reducing microwave loss from 0.554dB/cm/Hz1/2 to 0.399dB/cm/Hz1/2. This optimization approach enables broader bandwidths and lower microwave losses in electrodes and presents a novel idea for electrode optimization in modulators.
KEYWORDS: Microwave photonics, Electromagnetism, Telecommunications, Signal generators, Signal processing, Frequency combs, Modulation frequency, Channel projecting optics, Signal detection, Sensing systems
As the electromagnetic environment becomes more and more complex and strong electromagnetic interference becomes normal, in order to improve the ability of ultra-wideband(UWB) communication under strong resistance and complex electromagnetic environment, the wideband communication anti-interference technology has been applied more and more widely in electronic information systems. Based on the advantages of microwave photonic technology such as ultra-wideband and anti-interference, this paper constructed an ultra-wideband adaptive anti-interference communication system by combining microwave photonic spectrum sensing and high-speed frequency hopping signal generation. In the ultra-wideband adaptive anti-jamming communication system, the spectrum sensing module carries out high-speed real-time sensing of electromagnetic environment, the intelligent processor decides the safe spectrum information according to the spectrum sensing information, and the frequency-hopping signal generation module generates high-speed frequency-hopping signals according to the decision information, which can realize the adaptive anti-jamming of ultra-wideband communication. In the simulation, the 2~18GHz frequency spectrum is perceived at a high speed by using a coherent optical comb, and a frequency hopping pattern is determined according to the perceived information. The frequency hopping signal generation module generates a frequency hopping signal of 20000 hops /s according to the frequency hopping pattern, which improves the adaptive recognition ability of the communication system in the UWB range.
The high-frequency and tunable microwave signals are highly desirable in the files of military and civilian. The microwave photonic technology is an important solution to generate high-frequency and tunable microwave signals. Among them, the integrated microwave photonic solutions have a broader application prospect due to its small size, large bandwidth, and low power consumption, etc. We demonstrate a design of the monolithic integrated coupled DFB lasers (IC-DFB) to generate tunable microwave signal. A semiconductor optical amplifier (SOA) is integrated between DFB lasers to adjust the coupling strength. By tuning the injection current of the SOA section, microwave signals with a tuning range from 31 GHz to 35 GHz is achieve.
The increasing demands for enhance information security in the national defense and military applications such as satellite communication and integrated RF front end, have led to a critical requirement for high-speed frequency-hopping systems. However, the traditional frequency-hopping systems which is based on electrical domain is limited by its own electronic bottleneck. For example, the bandwidth is generally limited to several GHz, and the speed is generally limited to ms. Therefore, this paper innovatively propose a frequency-hopping system which has wide hopping-frequency bandwidth and frequency-hopping speed by using microwave photonics. The system has a frequency hopping bandwidth of more than 70GHz, a hopping speed of up to ns, and a maximum support of 35 frequency points, which can greatly expand the application prospect of secure communication.
The trend of modern radar signals towards multi format, multi frequency band, and large bandwidth has posed greater challenges to radar signal detection in electronic warfare, requiring receivers to have large instantaneous bandwidth, wide spectral coverage and high-frequency spectral resolution capabilities. Microwave photon technology, due to its advantages of low loss, large bandwidth, resistance to electromagnetic interference, and simple equipment structure, is matched with the demand for ultra wideband channelized reception. This article designs a parallel reconfigurable channelized reception scheme for high-frequency and broadband signals and conducts simulation verification. A coherent dual optical comb with 30 comb teeth is generated based on a cascaded electro-optic modulator, and a dual parallel Mach-Zehnder modulator is used to broadcast the broadband signals and frequency shifting of optical combs to achieve channel division of 17 channels. Finally, a filter was used to filter out the signal from a single free spectral region of the optical comb for down conversion, achieving information extraction of high-frequency broadband signals with a bandwidth smaller than the free spectral range of the optical frequency comb using a small free spectral region optical frequency comb.
We proposed an ultra-wide-band microwave photonics flexible frequency conversion scheme for integrated electronic systems, meeting the requirements of frequency conversion for multifunctional signal without crosstalk. The reconfigurable microwave photonics filter is exploited to achieve the flexible segmentation of optical broadband microwave signal with different center frequency and elastic bandwidth. The LO optical signal adapted to the signal frequency and target IF frequency is provided by the signal optical carrier, and the carrier-suppression single sideband mode of DPMZM ensures the flexible frequency conversion function. The numerical simulation of the proposed scheme is introduced to verify the feasibility and effectiveness, and three analog wideband signals are flexibly and efficiently converted to the target frequency with almost no crosstalk interference.
The precision of frequency signal is constantly improving, and the application of high-precision frequency signals requires an equally high-precision transmission method. So in this paper, we demonstrate an optical carrier radiofrequency phase stabilization transfer system based on a phase lock loop (PLL), applied to a 20 km spooled fiber link. The phase noise induced by optical fiber is suppressed by the PLL, and the transfer stability improved from 7.2×10-13@1 s to 8.9×10-15@1 s. In addition, the phase difference of peak-to-peak with compensation is less than 10 ps in a measurement of about 1 day. The phase study in antenna is with the compensation mode, so this work will lay the foundation for the phase synchronization of distributed coherent antenna system.
An optical true-time delay generation scheme based on WSS for adaptive null steering is proposed. The system is based on optically-switched fiber TTD technology. Take the advantages of the LCoS-based programmable WSS, arbitrary multiple true-time delays to generate multiple nulls can simultaneously be synthesized by control the routing of the optical radio frequency signal between the wavelength selective switches. We simulate the scheme with Optisystem and Matlab, the results confirm the scheme is able to achieve null depth over 50dB.
For the urgent demand of the broadband, high efficient, parallel processing and high speed frequency hopping capability in the field of ultra-wideband measurement control and communication, this paper puts forward a kind of channelized receive technology based on microwave photonic technology. The coherent optical comb generation module generates the signal optical comb and the local oscillator optical comb, and coherent optical comb with high repetition frequency is obtained by using cascade modulator and nonlinear technique. In order to satisfy the 10 comb teeth designed for the system, the FSR of coherent optical frequency comb is greater than 100GHz and 99.4GHz respectively, and the channel bandwidth is 600MHz. The channel division module receives the frequency hopping signal from the RF front-end and modulates it to the optical frequency comb. By DPMZM single sideband modulation, 10 optical combs can be used to shift the frequency of the oscillator frequency comb. At the same time, according to the position of the frequency hopping signal, the frequency comb is carefully controlled. After the WDM multiplexing device, it is selected by the high-speed optical switch controlled by the control unit. And photoelectric detection and mirror frequency suppression are realized by coherent demodulation, which consists of an optical mixer, a balance detector and a bridge. Which realizes channelized reception and cross-frequency conversion of any 6GHz wideband signal from the DC to 40 GHz band. Achieve 3dB channel consistency and mirror frequency suppression above 30dB. The results are verified by simulation and experiment. This method can be used to receive ultra-wideband ultra-high speed frequency hopping signals.
Concerning future ultra wideband (UWB) real-time measurement of electromagnetic spectrum demand in electromagnetic battlefield, this paper proposes a frequency-time mapping measurement method based on microwave photonics. Frequency-time mapping, or real-time Fourier transform, maps the input ultra-wideband electromagnetic spectrum information to the output time-domain waveform. The electromagnetic spectrum signal is modulated to light by CS-SSB modulation, and frequency-time mapping is formed by using electrically modulated micro-ring. Through simulation verification, the method can achieve frequency measurement of panoramic bandwidth signal from100MHz to 30GHz.The frequency resolution can reach 80 MHZ, whose scanning time is less than 20us. The method can achieve ultra-high speed, high-precision, broadband measurement of wideband complex electromagnetic spectrum situation, providing technical support for future electromagnetic spectrum operations.
KEYWORDS: Channel projecting optics, Frequency combs, Modulators, Signal detection, Mirrors, Control systems, Single mode fibers, Oscillators, Microwave photonics, Modulation
For the urgent demand of the broadband, high efficient, parallel processing and anti-jamming capability in the field of ultra-wideband measurement control and communication. This paper puts forward a kind of channelized receive technology based on microwave photonic technology. The coherent optical comb generation module generates the signal optical comb and the local oscillator optical comb. The coherent optical comb with high repetition frequency is obtained by using cascade modulator and nonlinear technique. In order to satisfy the 10 comb tooth designed for the system, the FSR of coherent optical frequency comb is greater than 100GHz and 99.4GHz respectively, and the channel bandwidth is 600MHz. The channel division module receives the broadband RF signal from the RF front-end and modulates it to the optical frequency comb. By DPMZM single sideband modulation, 10 optical combs can be used to shift the frequency of the oscillator frequency comb. At the same time, according to the position of the 6GHz signal, the frequency comb is accurate controlled. After the WDM multiplexing device, it is selected by the high-speed optical switch controlled by the control unit. The photoelectric detection and mirror frequency suppression are realized by coherent demodulation, which consists of an optical mixer, a balance detector and a bridge. Which realizes channelized reception and cross-frequency conversion of any 6GHz wideband signal from the DC to 40 GHz band. Achieve 3dB channel consistency and mirror frequency suppression above 30dB. The results are verified by simulation and experiment. This method can also be extended to receive ultra-high speed frequency hopping signals. Which can provides technical support for ultra-wideband measurement control and communication, integrated RF front-end and electromagnetic space integration system.
Underwater wireless optical communication can realize short-distance, high-speed communication. It effectively supplements the vacancy of optical cable communication, radio communication and underwater acoustic communication in underwater networking. Using Orthogonal Frequency Division Multiplexing (OFDM) technology in underwater wireless optical communication can effectively reduce the influence of multipath effects in the channel and improve system communication performance. The error correction ability of Reed-solomon (RS) code under medium code length is close to the theoretical value. This letter analyzes the underwater optical channel model, simulates the underwater optical communication system based on RS coding and OFMD, and studies the influence of communication distance and signal-to-noise ratio (SNR) on bit error rate (BER), as well as the error code distribution in the presence of Doppler shift and the impact of interleaving on system performance. The simulation results show that the BER of received signal increases with the increase of communication distance and the decrease of SNR; When Doppler shift exists, error codes appear in concentrated positions. Deep interleaving can effectively utilize the error correction ability of RS coding, reduce the influence of Doppler shift, and improve the communication quality of the system.
Aiming to solve the problems of the atmospheric turbulence in free-space optical communications which cause the increase of the system bit error and influence the communication stability, an algorithm is proposed to suppress the influence of atmospheric turbulence. This algorithm combines traditional grouped matrix interleaver and random interleaver design methods to construct a new type of interleaving matrix to solve the turbulence effect under different atmospheric conditions. A field programmable gate array (FPGA) board with external DDR3 is used to implement the algorithm and optimize the delay. The results show that the algorithm is accurate and reliable in different turbulence models. At the same time, the impact of turbulence effects on link performance can be reduced to a certain extent.
Photonic generation and processing of high-frequency and large-bandwidth microwave arbitrary waveforms have become an increasingly important area that can find numerous applications, such as in ultrawide-band (UWB) communication systems, radar, and other warfare systems, and the quality directly decides the system performance. Based on the microwave photonic channelization, arbitrary waveforms were generated through dual optical frequency combs (OFCs) with different free spectrum ranges (FSR). Due to the multiple optical channels with tunable amplitude and phase, the fundamental and higher harmonics are generated simultaneously and used to synthesize into the required waveforms. Combining the advantages of low-loss broadband photonics and microwave with fine narrowband control, the proposed channelized synthesis arbitrary waveform overcomes the electronic bottleneck of ultra-wideband analog processing and opens up a whole new solution to microwave signal generation. The simulation experiment system based on Optisystem software is conducted, the results confirm that an arbitrary wave, such as triangular, square, and sawtooth will be generated by adjusting the channel parameters, and the accuracy of the generated waveforms can be improved by introducing the fifth Fourier component. Compared to the waveform synthesized by the third-order harmonic, the root mean square error (RMSE) of the fifth-order harmonic is increased by 17%-20%.
In response to the harsh environmental conditions and the strict requirements for payload mass of the airborne platform, a structural design method is proposed for a good performance stability, lightweight and miniaturized laser expander system. In order to realize the lightweight and miniaturization design of the laser expander system, a miniaturized coaxial catadioptric defocus optical system is designed consisting of mirrors and lens. To ensure the stability and lightweight of the structure, the flexure and the main support structure which combined the thin-wall cylinder and truss are designed for the mirrors and lens. Finally, the engineering analysis of the system is carried out. The results show that the relative decenter and spacing between primary mirror and secondary mirror are 2.28μm and 5.92μm under normal working condition, respectively. The maximum surface shape error of the mirrors is 5.42nm. The first-order natural frequency of the system is 349.6Hz, and the maximum value of the root-mean-square of acceleration response under random vibration excitation occurs on the primary mirror, and the amplification factor is 7.1. It meets the mechanical performance requirements of airborne platform.
Due to the diversity of underwater environments, it is difficult to test the underwater optical communication systems in actual seawater. This letter uses the Monte Carlo model to study channel capacity of underwater optical communications. Matlab is used to analyze the transmission of laser of various wavelengths in different water and the influence of changes in water quality. Furthermore, the influences of seawater type, divergence Angle, transmission distance and beam type on the power received by the receiver are analyzed when blue-green laser is used as the light source. The experiment shows that in the same water quality, with the increase of divergence Angle and transmission distance, the light intensity received by the receiver becomes smaller and smaller and the photon distribution becomes more and more dispersed. Compared with the Gaussian beam, when the attenuation coefficient is small, the energy of the receiving end is more concentrated when flat-top beam is used as the light source.
In the fields of ultra-wideband satellite communication, integrated radio frequency, radar and other national defense and military at present, it is necessary to realize the interconversion between baseband signals and radio frequency signals in Ka or even U band and L band to meet the processing requirements of RF front-end. Traditional electronic technology usually uses multistage local vibration mixing to realize frequency conversion, which is complicated and accompanied by serious nonlinearity and noise accumulation. As a kind of multi-wavelength light source, optical frequency beam can provide stable multiple local oscillations in the optical domain, and move the baseband/RF signals to the optical domain to achieve flexible mixing processing. In this paper, an UWB microwave photonic mixing technology based on optical frequency comb is innovatively proposed. UWB octave-spanning up-conversion from 10MHz to 60.01 GHz and down-conversion can be achieved by using only 20 GHz microwave driver, which effectively improves the RF preprocessing capability of UWB transmitter in the field of national defense and military.
Vector beam lasers are highly desirable for wide applications ranging from manipulation to communications. In this paper, we report the first directly modulated vector beam laser with azimuthally polarized emission. It’s a microcylinder cavity added with proper second order grating on the top, which enables single-mode lasing and efficient surface emission. Through theoretically and numerically analysis, the lasers are designed in detail. With optimized top grating, the emission is azimuthally polarized vector beam.
Due to increasing demand for high-speed and large capacity of data transmission, seamless connection between space network and Internet becomes one of the current trends of space communication. Under this background, this paper proposes an IPv6 over AOS gateway system based on FPGA to integrate the Internet and the space network. The system achieves protocol conversion to transmit IPv6 packets through the packet service in the AOS spatial data link protocol, and also has the function of address resolution and label switching. The main contents of this paper are as follows: 1. The IPv6 protocol, NDP protocol, MPLS technology and the conversion mechanism of IP over AOS protocol are studied. 2. The system test environment was set up to simulate the datagram transmission of spatial link between different node, the system performance and link stability were carried out by using logic analyzer and network packet capture tools. 3. The results of the function verification and performance test were analyzed and summarized according to packet loss rate and bandwidth availability ratio. The system achieves a variety of data types and large capacity information data transmission, it can also reduce networking costs while improving the transmission efficiency.
Based on the classical theory of atmospheric turbulence, the time-frequency transfer model of laser in free space channel was established, and the variation rules of turbulence intensity, outer scale, wind speed and transmission distance on the stabiliThe random fluctuation of atmospheric refractive index seriously affects the accuracy and stability ty of frequency transfer were simulated and compared with common noise types. The results show that the stability of frequency transfer decreases linearly with the increase of turbulence intensity and transmission distance. The interference of medium intensity turbulence to frequency signal is greater than the inherent noise of the system. The frequency stability is negatively correlated with the wind speed. Increasing the integration time may reduce the wind speed disturbance. This paper can provide reference for the design and optimization of laser time-frequency transmission system.
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