The new microwave photonic receiver system employs spatial light processing to enable multi-beam imaging within its field of view. This system uses fiber optic links for transmission, where the optical phase is sensitive to environmental disturbances, potentially affecting imaging quality. This paper aims to design and implement an efficient phase consistency control system for multi-channel optical fiber links. The system ensures the coherence of optical signals during transmission by precisely locking the phase in each channel's fiber optic link. Additionally, a serial digital-to-analog conversion scheme is proposed to address the pin count limitations of FPGA. Precise optical phase consistency control was achieved in single-channel experiments, and the serial digital-to-analog conversion scheme was validated on a 24- channel microwave photonic receiver, where stable image points were observed on the camera.
Phased array radar has important applications in military and civil fields. In order to improve the performance of radar systems, there is a growing demand for increased the signal bandwidth. However, with the larger bandwidth, the traditional phased array system based on microwave phase shifter will have obvious beam squint phenomenon when realizing beam pointing adjustment. Hence, the microwave photonic broadband phased array with the core of light-controlled microwave technology has become a much-appreciated realization of broadband phased array. For the beam squint phenomenon caused by broadband signals, this paper proposes a scheme of using the true time delay introduced by a continuously tunable Mach-Zehnder interferometer for compensation in optical domain. Four different bandwidth with different center frequencies were designed and validated to achieve a squint free beamforming within the scanning angles of ±30°.
Talbot self-imaging has been utilized for arbitrary repetition-rate control of optical pulse trains and frequency combs, which are important for many applications. The fundamental theory of generalized Talbot self-imaging has been presented for the design of temporal and spectral phase operations, while the effects of potential phase modulation distortions and residual dispersions on repetition-rate control in experiments remain to be investigated. In this paper, numerical studies are conducted for evaluating the feasibility of yielding arbitrary repetition-rate control of optical pulse trains and frequency combs, and it provides additional insights into the optimal design conditions for practical implementation of the scheme.
In this paper, we propose and demonstrate a novel Tilted Fiber Bragg grating (TFBG) sensing demodulation scheme based on microwave photonic technique. In the proposed approach, the optical power spectrum from BBS (Broadband source) is shaped by a TFBG and then sent to a dispersive element to perform the linear wavelength-to-time mapping. A nonuniform microwave photonic filter with the center frequency depending on the shaped optical spectrum is obtained at the output of a high-speed photodetector. The central frequency and the envelope of the generated microwave photonic filter will shift according to the change of environment. Theory and a proof-of-principle experiment are implemented to verify the proposed approach.
A photonic RF self-interference cancellation (SIC) scheme for full-duplex communication is proposed and demonstrated experimentally. It is based on phase modulation to convert the RF signal into optical domain. The interference cancellation performance of the photonic RF SIC system under different delay deviation (Δτ) and amplitude deviation (Δα) is analyzed. The cancellation depth of 34.5 dB is measured for 10 GHz signal with bandwidth of 50MHz. According to experimental results, the interference cancellation performance affected by the time delay deviation, the amplitude deviation and the phase response is investigated. The results give a direction for the improvement of system performance.
In this paper, we present a tilted fiber Bragg gratings (TFBG) based surface Plasmon resonance (SPR) label-free sensors with boronic acid derivative (ABA-PBA) as receptor molecule to detect glycoprotein with high sensitivity and selectivity. Tilted fiber Bragg gratings (TFBG) as a near infrared wavelengths detecting element can be able to excite a number of cladding modes whose properties can be detected accurately by measuring the variation of transmitted spectra. A 10° TFBG coated by 50nm gold film was manufactured to stimulate surface plasmon resonance on the surface of the sensor. The sensor was loaded with boronic acid derivative as the recognition molecule which has been widely used in various areas for the recognition matrix of diol-containing biomolecules. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with the protein concentration sensitivity up to 2.867dB/ (mg/ml) and the limit of detection was 2*10-5g/ml.
A compact dual-loop optoelectronic oscillator (OEO) employing a dual-output Mach–Zehnder intensity modulator (DOMZM) and a balanced photodetector (BPD) is theoretically analyzed and experimentally demonstrated. The fundamental idea of the scheme is based on double loops formed by two complementary output ports of DOMZM and two input ports of BPD, which could be naturally combined without any additional optical coupler or polarization beam splitter devices. This simple structure makes it possible to enhance side-mode suppression ratio (SMSR) and reduce phase noise of the OEO. Compared with the traditional dual-loop OEO (SO-OEO) based on single-output Mach–Zehnder modulator (MZM), optical coupler, and BPD, the advantages of our proposed dual-loop OEO (DO-OEO) with DOMZM and BPD are presented. Experimental results show that a 16-GHz single-mode OEO is obtained with measured SMSR of 72 dB and phase noise of −133.2 dBc/Hz at 10-kHz frequency offset.
A polymer-based multimode interference optical splitter chip has been designed and fabricated. Fiber-waveguide coupling loss as well as the structure of the multimode waveguide are optimized in the design to achieve higher performance. A simple UV-based soft nanoimprint lithography (Soft UV-NIL) technique is adopted in the fabrication. Fluorinated acrylate resins, LFR, with different refractive indices are used in this work. Both the residual layer and waveguide deformation are improved by controlling the fabrication processes. An average of 12.98 dB insertion loss is obtained from 1×4 splitters with 1.08 dB uniformity and 0.05 dB polarization-dependent loss. The validity of the polymer optical splitters fabricated through Soft UV-NIL technique is demonstrated by software simulation as well as experimental works.
A polymer-based multimode interference (MMI) optical splitter chip has been fabricated through UV-based soft imprint lithography (Soft UV-NIL) technique. Propagation loss and bending loss are considered during the chip design in order to decrease the insertion loss. UV curable fluorinated acrylate resin is used due to its low material absorbing loss. 1×4 cascaded MMI splitter is fabricated and measured at 1550 nm optical wavelength and an average 12.38 dB insertion loss is obtained together with an 1.23 dB uniformity.
A novel optical single-sideband (OSSB) signal generation with simultaneous IF signal up conversion technique is proposed to overcome the fiber dispersion problem. With this up-conversion technique, a high frequency OSSB signal is generated by using two low bandwidth intensity modulators in combination with fiber gratings. The low frequency local oscillator (LO) signal is modulated by employing frequency doubling technique or frequency quadrupling technique respectively. The OSSB radio frequency (RF) signal generated by mixing the intermediate frequency (IF) signal and low frequency local oscillator (LO) signal, is transmitted over standard single-mode fiber successfully. The received signal error vector magnitude (EVM) is 5.8% rms and 13% rms.
The filtering properties of a continuously tunable single-passband microwave photonic filter based on stimulated Brillouin scattering (SBS) are investigated. The filter utilizes the advantage of combining phase-modulated RF signal and dual-sideband suppressed-carrier pump signal to achieve the SBS-based tunable narrowband filtering. The effects of pump power on the out-of-band rejection (OBR) and 3-dB bandwidth, the optical fiber structure on the resonant sideband, and input RF signal power on the OBR and 3-dB bandwidth are analyzed theoretically and experimentally. The results show that the pump power has the potential of increasing the OBR and tuning 3-dB bandwidth, whereas the RF signal power has nearly no influence on the two parameters.
KEYWORDS: Signal generators, Singular optics, Modulators, Modulation, Radio optics, Single mode fibers, Microwave radiation, Eye, Signal detection, Optical amplifiers
A novel method is proposed for optical up-converted single-sideband (OSSB) signal generation in radio over fiber links, which can realize optical carrier reuse synchronously. The OSSB signal is generated in order to overcome the fiber dispersion problem by using two intensity modulators in combination with fiber gratings. With this up-conversion technique, a 25 GHz OSSB radio frequency signal is generated by mixing an intermediate frequency signal (5 GHz) and low frequency local oscillator signal (10 GHz). The signal is transmitted over 25 km standard single-mode fiber successfully. And the received signal error vector magnitude is 5.8% root mean square, with eye diagram widely open.
KEYWORDS: Microwave radiation, Single mode fibers, Time division multiplexing, Optical amplifiers, Optical switching, Dispersion, Switches, Modulators, Signal detection, Signal attenuation
We propose a novel photonic technique for unknown microwave frequency measurement by employing an optical group delay line. The 7-bit optical delay line composed of several magneto-optical switches and 1.6 km single-mode fiber is designed as a tunable dispersive medium in the measurement system. In our scheme, the measurable frequency range of 1 to 20 GHz with a measurement error less than ±40 MHz was demonstrated experimentally. Also, we studied the sensitivity of the whole measurement system, and the minimum detectable power reached −50 dBm .
Instantaneous frequency measurement (IFM) of input unknown microwave signals is critical importance for modern radar warning receivers in the field of electronic warfare. The photonic techniques have attracted more and more attentions for IFM due to the advantages of wide bandwidth, low loss, light weight, and immunity to electromagnetic interference. In this paper, a photonic approach to IFM with extended range based on phase modulation is presented. In the proposed measurement system, two optical wavelengths and two segment dispersion fibers are used to construct the frequency-dependent amplitude comparison functions (ACFs). Several ACFs can be jointly utilized to determine the microwave frequency without ambiguities beyond a monotonic region of the conventional one ACF. Then the measurable range of microwave frequency can be extended and the accuracy can be improved by selection of ACF with large slope. The operation principle of the photonic approach is illustrated and the experiment results show that the errors are limited within ±0.15 GHz from 8 to 20GHz frequency measurement range.
A novel technique for instantaneous frequency measurement of unknown microwave signal based on both phase
modulation and intensity modulation is theoretically and experimentally demonstrated. Based on the output microwave
power through dispersive fiber links, three amplitude comparison functions (ACFs) are established, which are combined
to measure the frequency of input microwave signal with improved measurable range and accuracy. In the frequency
estimation process, the measured calibration ACFs are utilized as the look-up table. The experiment results show that
measurement error smaller than 200 MHz can be obtained for the frequency from 0.5 GHz to 20 GHz.
Optical waveguide biosensors are attracting more and more attentions and presenting great potential applications.
Polymer-based optical biosensors are promising for the their unique advantages: low cost, easy fabrication,
possibility of functionalization with chemicals for the detection of biological molecules, and flexible operating
wavelength in both the infrared communication wavelength band (1310-1550nm) and the visible wavelength region
(500-800nm). Operating in the visible wavelength, the optical biosensing can avoid the high optical absorption loss
of water solution, which can hardly be done for Si-based optical sensors. In this paper, an optical biosensor utilizing
polymer-based athermal optical waveguide microring resonator is presented. The athermal design of the microring
resonator can make the resonant wavelength drift with temperature be greatly reduced, and an optical biosensing
platform with high thermal stability can be achieved. The simulation results show that the maximal resonant
wavelength drift is -0.0085nm when the temperature varies from 20°C to 65°C and the maximal wavelength drift
slope is -0.0009nm/K. With the microring resonators fabricated by using a simple UV based soft imprint technique
with self-developed UV-curable polymer PSQ-L materials, experimental investigations on the specific surface
detection of target molecules have been preliminarily performed. The results shows that the optical biosensors
based on the polymer optical microring resonators would have potential applications for label-free surface sensing.
A novel photonic approach for measuring microwave frequency over a wide bandwidth, based on intensity-modulated link with output microwave interference detection, is proposed. In this simple measurement system, a tunable laser and a fixed-wavelength laser are used with a single-mode fiber as the dispersive medium. By scanning the wavelength of a tunable laser, the frequency of the modulated microwave signal can be obtained directly through analyzing the interference intensity of the microwave signal at the output of the photodetector. The proposed approach is demonstrated experimentally by obtaining the unknown microwave frequency in the range of 1 to 20 GHz with a measurement accuracy of several tens of MHz.
Integrated waveguide microwave photonic filters (MPFs) have the potential to bring down volume, weight, and power consumption of signal processing equipment besides the common advantages of discrete-component-based MPFs. A polysiloxane-liquid polymer-based optical wave-guide microring resonator was designed and fabricated by a simple ultraviolet-based soft-imprint technology, with which the quasi-single-sideband filtering for the 10 to 22 GHz microwave signal was realized and 20 Mbps quadrature phase shift keying signal carried by 14.35 GHz microwave transmission over a 25 km single mode fiber was demonstrated.
Phase noise characteristics of the carrier transmitted by the double-sideband-carrier-suppressed (DSB-CS) modulation system are investigated. On the basis of the established DSB-CS modulation system, the phase noise of the input carrier and the output doubled frequency carrier is measured. The influencing factors on the far-from-carrier phase noise are discussed in detail. The noise current mean-square value of the signal-spontaneous beat noise is first derived in the case that there are two first-order optical sidebands generated by DSB-CS modulation. It is shown that the far-from-carrier phase noise is degraded primarily due to the signal-spontaneous beat noise and the relative-intensity noise.
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