Showing papers by "Kun Xu published in 2014"
TL;DR: Some of the notable challenges in MWP are identified and the recent work is reviewed and applications and future direction of research are also discussed.
Abstract: Microwave photonics (MWPs) uses the strength of photonic techniques to generate, process, control, and distribute microwave signals, combining the advantages of microwaves and photonics. As one of the main topics of MWP, radio-over-fiber (RoF) links can provide features that are very difficult or even impossible to achieve with traditional technologies. Meanwhile, a considerable number of signal-processing subsystems have been carried out in the field of MWP as they are instrumental for the implementation of many functionalities. However, there are still several challenges in strengthening the performance of the technology to support systems and applications with more complex structures, multiple functionality, larger bandwidth, and larger processing capability. In this paper, we identify some of the notable challenges in MWP and review our recent work. Applications and future direction of research are also discussed.
103 citations
TL;DR: Based on optical frequency combs (OFC), this work proposes an efficient and flexible multi-band frequency conversion scheme for satellite repeater applications that realizes simultaneous inter- and intra- band frequency conversion just in a single structure and needs only three frequency-fixed microwave sources.
Abstract: Based on optical frequency combs (OFC), we propose an efficient and flexible multi-band frequency conversion scheme for satellite repeater applications. The underlying principle is to mix dual coherent OFCs with one of which carrying the input signal. By optically channelizing the mixed OFCs, the converted signal in different bands can be obtained in different channels. Alternatively, the scheme can be configured to generate multi-band local oscillators (LO) for widely distribution. Moreover, the scheme realizes simultaneous inter- and intra-band frequency conversion just in a single structure and needs only three frequency-fixed microwave sources. We carry out a proof of concept experiment in which multiple LOs with 2 GHz, 10 GHz, 18 GHz, and 26 GHz are generated. A C-band signal of 6.1 GHz input to the proposed scheme is successfully converted to 4.1 GHz (C band), 3.9 GHz (C band) and 11.9 GHz (X band), etc. Compared with the back-to-back (B2B) case measured at 0 dBm input power, the proposed scheme shows a 9.3% error vector magnitude (EVM) degradation at each output channel. Furthermore, all channels satisfy the EVM limit in a very wide input power range.
63 citations
05 Dec 2014
TL;DR: Zhang et al. as discussed by the authors propose a pipeline framework to model a user's query intention as a phrase level dependency DAG which is then instantiated regarding a specific KB to construct the final structured query.
Abstract: Understanding natural language questions and converting them into structured queries have been considered as a crucial way to help users access large scale structured knowledge bases. However, the task usually involves two main challenges: recognizing users’ query intention and mapping the involved semantic items against a given knowledge base (KB). In this paper, we propose an efficient pipeline framework to model a user’s query intention as a phrase level dependency DAG which is then instantiated regarding a specific KB to construct the final structured query. Our model benefits from the efficiency of linear structured prediction models and the separation of KB-independent and KB-related modelings. We evaluate our model on two datasets, and the experimental results showed that our method outperforms the state-of-the-art methods on the Free917 dataset, and, with limited training data from Free917, our model can smoothly adapt to new challenging dataset, WebQuestion, without extra training efforts while maintaining promising performances.
62 citations
TL;DR: In this paper, the wavelength of the optical carrier is adjusted according to the phase variation of the reference LO, to stabilize the delay of the fiber link, and the phases of other LO signals that transferred through the same fiber link will all be stabilized.
Abstract: In this paper, we propose and demonstrate a multiple local oscillator (LO) signal phase stabilization technique for long-distance fiber delivery. One of the LO signals, which acts as a reference single, is round-trip transferred between the central station and the remote end, carrying the phase variation arises from perturbations of the fiber link. The wavelength of the optical carrier is adjusted according to the phase variation of the reference LO, to stabilize the delay of the fiber link. Once the delay of the link is stabilized, the phases of other LO signals that transferred through the same fiber link will all be stabilized. Meanwhile, the delay tunable range is in proportion to the fiber length, which means a very long delivery distance can be expected. Experimentally, LOs at frequencies of 2.46 GHz and 8 GHz are transferred through a 30-km fiber link, and significant phase drift compression is observed at both frequencies.
57 citations
TL;DR: A phase-conjugation-based fast radio frequency (RF) phase auto stabilization technique for long-distance fiber delivery, which avoids the use of any tunable parts and dynamic phase tracking, enabling a fast phase stabilization at the remote site.
Abstract: In this paper, we propose a phase-conjugation-based fast radio frequency (RF) phase auto stabilization technique for long-distance fiber delivery. By phase conjugation at the center site, the proposed scheme pre-phase-promotes the RF signal with the shift which is acquired by round-trip transferring another RF whose frequency is half of the one to be sent. Such phase pre-promotion is then used to counteract exactly the following retard induced by one-way delivery. Different from the previous phase-locking-loop-based schemes, the proposed open-loop design avoids the use of any tunable parts and dynamic phase tracking, enabling a fast phase stabilization at the remote site. An end-less compensation capacity can also be achieved. Our design is analyzed by theory. Experimentally, the new scheme is verified by transferring a frequency of 2.42 GHz through a 30-km optical fiber link. Significant phase drift compression is observed. The rapid phase stabilization is verified by introducing sudden time delay change into the link. The recovery time equals to the round-trip time of the link plus the transitional duration of the delay change, which is much shorter than the traditional trial-and-error phase locking loop. Important issues of the system design are discussed.
48 citations
TL;DR: In this paper, a post digital linearization technique is proposed and demonstrated for a conventional intensity-modulation direct-detection analog photonic link, where the key distortion information is directly acquired from hardware.
Abstract: In this paper, a post digital linearization technique is proposed and demonstrated for a conventional intensity-modulation direct-detection analog photonic link. Instead of precisely emulating the transfer function of the whole nonlinear system in the digital domain, the key distortion information is directly acquired from hardware. By low biasing the Mach-Zehnder modulator, linearization can be achieved through simply multiplying the distorted signal by the coreceived low-pass band. Theory analysis shows that only the bias angle should be known by the algorithm, whereas the simulation shows adequate tolerance. The low bias angle also results in an improved link gain. The experiment shows a well-suppressed third-order intermodulation distortion (IMD3). With the optical down conversion, we demonstrate a spurious-free dynamic range increasing from 103.2 to 123.3 dB in a 1-Hz bandwidth.
42 citations
TL;DR: A phase stabilized wideband downlink transmission scheme, which directly transmits the received radio frequency signals from remote antennas to central station, and a tunable optical delay line is realized to cancel the delay variation of the fiber link.
Abstract: In this paper, we propose and demonstrate a phase stabilized wideband downlink transmission scheme, which directly transmits the received radio frequency (RF) signals from remote antennas to central station. A reference RF tone is round-trip transferred between the central station and remote end to obtain the delay variation caused by the fiber link. The delay variation is then used to alter a tunable laser. Since optical carriers with different wavelengths propagate at different velocities in fiber, a tunable optical delay line is realized to cancel the delay variation of the fiber link. The tunable delay range is in proportion to the length of the fiber link, which means a very long delivery distance can be expected. Experimentally, a RF signal at frequency of 2.50 GHz has been downlink transferred through a 45 km fiber link, with stability of 3.3 x 10⁻¹³ at 1 s and 7.5 x 10⁻¹⁷ at 10⁴s.
36 citations
TL;DR: This paper proposes the path-label transitive closure method to answer LCR queries in large graphs, and proves that finding the optimal graph partition to minimize query processing cost is a NP-hard problem.
32 citations
TL;DR: A novel scheme to effectively suppress the cross modulation distortion (XMD) and the third-order inter-modulation distortion (IMD3) which exist in wide-band, multi-carrier analog photonic link (APL) system is proposed and demonstrated.
Abstract: We propose and demonstrate a novel scheme to effectively suppress the cross modulation distortion (XMD) and the third-order inter-modulation distortion (IMD3) which exist in wide-band, multi-carrier analog photonic link (APL) system. Such nonlinearities, which are caused by the out-of-band and in-band signals, respectively, constrain the link’s performance severely. Instead of building an extra nonlinear path in hardware, the XMD and IMD3 compensation information is extracted from the received distorted signal, and both distortions are then suppressed by digitally multiplying the distorted signal with the compensation information. After compensation in the digital domain, the down-converted XMD and IMD3 distortions are experimentally suppressed with 33 dB and 25 dB, respectively, resulting in an improved upper limit for the SFDR.
22 citations
TL;DR: A fiber link capable of stable time signal transfer utilizing the authors' active long-distance radio frequency (RF) stabilization technology, which compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference.
Abstract: In this Letter we demonstrate a fiber link capable of stable time signal transfer utilizing our active long-distance radio frequency (RF) stabilization technology. Taking advantage of the chromatic dispersion in optical fiber, our scheme compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference. Since the time signal and the RF reference are carried by the same optical carrier, a highly stable time transfer is achieved at the same time. Experimentally, we demonstrate a stability of the time signal transfer over 50-km fiber with a time deviation of 40 ps at 1-s average and 2.3 ps at 1000-s average. The performance of the RF reference delivery is also tested, with an Allan deviation of 2×10−15 at 1000-s average. According to our proposal, a simultaneous stable time and frequency transfer is expected.
19 citations
TL;DR: Using the suggested parameters, the multi-dimensional DPD is able to improve the RF input power tolerance by greater than 3dB for each band in a two-band RoF system, indicating an enhancement of RF power transmitting efficiency.
Abstract: The recently-proposed multi-dimensional digital predistortion (DPD) technique is experimentally investigated in terms of nonlinearity order, memory length, oversampling rate, digital-to-analog conversion resolution, carrier frequency dependence and RF input power tolerance, in both directly-modulated and externally-modulated multi-band radio-over-fiber (RoF) systems. Similar characteristics of the multi-dimensional digital predistorter are identified in directly-modulated and externally-modulated RoF systems. The experimental results suggest implementing a memory-free multi-dimensional digital predistorter involving nonlinearity orders up to 5 at 2 × oversampling rate for practical multi-band RoF systems. Using the suggested parameters, the multi-dimensional DPD is able to improve the RF input power tolerance by greater than 3dB for each band in a two-band RoF system, indicating an enhancement of RF power transmitting efficiency.
TL;DR: Through using a high-performance pre- and post-amplifier, improved link noise figure and gain are obtained while the nonlinearity of the electrical amplifiers can be also compensated by the proposed algorithm.
Abstract: In this paper, we investigate the performance improvement in analog photonics link incorporating digital signal processing technique and low-noise electrical amplifiers. The proposed linearization does not require to know the precise transfer function of the whole nonlinear system, which is achieved by directly acquiring the output third-order intercept point from the system hardware. Through using a high-performance pre- and post-amplifier, improved link noise figure and gain are obtained while the nonlinearity of the electrical amplifiers can be also compensated by the proposed algorithm. Experimentally, spurious-free dynamic range of 128.3 dB in 1-Hz bandwidth is achieved for a digitizer noise limited analog photonics link. The measured noise figure and gain of the photonics link are 8.9 and 27.5 dB, respectively.
TL;DR: A multi-dimensional crest factor reduction (MD-CFR) technique is proposed to improve the performance and efficiency of multi-band radio-over-fiber (RoF) links, in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR).
Abstract: A multi-dimensional crest factor reduction (MD-CFR) technique is proposed to improve the performance and efficiency of multi-band radio-over-fiber (RoF) links. Cooperating with multi-dimensional digital predistortion (MD-DPD), MD-CFR increases the performance of both directly-modulated and externally-modulated RoF links, in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR). For directly-modulated RoF link, more than 5 dB output ACPR reduction is obtained, output EVMs are reduced from 11.83% and 12.47% to 7.51% and 7.26% for two bands respectively, while only a slight improvement to 11.58% and 10.78% is obtained solely using MD-DPD. Similar results are achieved in externally-modulated RoF link. Given a threshold in EVM or ACPR, the RF power transmit efficiency is also further enhanced.
Patent•
27 Aug 2014
TL;DR: In this paper, a self-interference canceling circuit comprising a detection module, an adjustment module, a feedback module and a combiner is proposed to solve the selfinterference problem in a passive RFID system.
Abstract: The invention relates to a self-interference canceling circuit comprising a detection module, an adjustment module, a feedback module and a combiner. By the adoption of the structure, the read-write capacity of electronic tags is enhanced, the number of identified tags is increased, the receiving flexibility of the system is improved, the amplitude of reflected signals of the tags is increased, and therefore a series of disadvantages caused by the self-interference problem in a passive RFID system are solved. The self-interference canceling circuit can be applied to various fields such as warehouse management in logistic storage, identity recognition, traffic and transportation, food, medical treatment, animal management, entrance guard burglary prevention and military industry.
TL;DR: In the scheme, the bandpass sampling technique is introduced in RoF systems to overcome the high sampling rate requirement and front-end hardware dependency of conventional digtal coherent receivers.
Abstract: A bandpass sampling based digital coherent receiver is presented for phase modulated radio-over-fiber links with coherent detection In the scheme, the bandpass sampling technique is introduced in RoF systems to overcome the high sampling rate requirement and front-end hardware dependency of conventional digtal coherent receivers In particular, the selection rule of bandpass sampling rate was defined by taking into account the frequency offset induced by free-running optical local oscillator Analytical assessment and simulations are used to determine the ultimate performance in terms of tolerances to ADC bit resolution and laser linewidth Thereafter, a 40Mbps QPSK modulated data signal at 24GHz RF carrier frequency is experimentally demonstrated over the proposed 506-km radio-over-fiber link employing bandpass sampling
Patent•
30 Jul 2014
TL;DR: The experimental results show that combining the two techniques further improves the performance as compared with the case solely using DPD in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR) for both directly modulated and externally modulated RoF links.
Abstract: In this letter, we investigate the combined use of crest factor reduction and digital predistortion (DPD) as an effective method for increasing the performance in radio-over-fiber (RoF)-based downlinks. The experimental results show that combining the two techniques further improves the performance as compared with the case solely using DPD in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR) for both directly modulated and externally modulated RoF links. Given a threshold in EVM or ACPR, the RF power transmit efficiency is also further enhanced.
Patent•
27 Aug 2014
TL;DR: In this article, the authors proposed a high-receiving-sensitivity passive RFID system with optical link connection, which has the advantages of being easily applied to wiring in different environments, being very low in optical link loss under a long-distance transmission circumstance, being suitable for transmission of large volumes of data and the like, and therefore the distribution range of an antenna is enlarged, the receiving sensitivity of the system is improved.
Abstract: The invention relates to a high-receiving-sensitivity passive RFID system with optical link connection. By the adoption of an optical link structure, the high-receiving-sensitivity passive RFID system has the advantages of being easily applied to wiring in different environments, being very low in optical link loss under a long-distance transmission circumstance, being suitable for transmission of large volumes of data and the like, and therefore the distribution range of an antenna is enlarged, the receiving sensitivity of the system is improved, and the system is suitable for application scenarios when a large number of electronic tags are identified. The problems that according to an existing passive RFID system, the range of tag identification is small, and identification accuracy is low are solved. The high-receiving-sensitivity passive RFID system can be widely applied to the fields of warehouse management in logistics storage, identity recognition, transportation, food, medical treatment, animal management, entrance guard against theft, industry, military and the like.
10 Jun 2014
TL;DR: Simulation results show that the improved PCF outperforms the distributed coordination function (DCF) in both the basic-access and request/clear-to-send modes in terms of the total throughput and the fairness among RAUs.
Abstract: In this paper, we present an improved IEEE 802.11 wireless local-area network (WLAN) medium access control (MAC) mechanism for simulcast radio-over-fiber-based distributed antenna systems where multiple remote antenna units (RAUs) are connected to one access point (AP). In the improved mechanism, the fiber delay between RAUs and central unit is taken into account in a modification to the conventional point coordination function (PCF) that achieves coordination by a centralized algorithm. Simulation results show that the improved PCF outperforms the distributed coordination function (DCF) in both the basic-access and request/clear-to-send modes in terms of the total throughput and the fairness among RAUs.
09 Mar 2014
TL;DR: In this article, a digital multi-channel post linearization technique is proposed for uplink of multi-band radio frequency (RoF) systems, with all linearization functions located in the central office, >12dB ACLR reduction is demonstrated in a two-band RoF system.
Abstract: A digital multi-channel post linearization technique is proposed for the uplink of multi-band RoF systems. With all linearization functions located in the central office, >12dB ACLR reduction is demonstrated in a two-band RoF system.
TL;DR: In this paper, the authors demonstrate the soliton generation from a mode-locked erbium-doped fiber laser using a novel saturable absorber (SA), which is realized by combining a dual-drive modulator and an intensity feed-forward path.
Abstract: We demonstrate for the first time to our knowledge, the soliton generation from a mode-locked erbium-doped fiber laser using a novel saturable absorber (SA), which is realized by combining a dual-drive modulator and an intensity feed-forward path. The laser is fundamentally mode-locked under high-frequency RF signal modulation. Experimentally, the actively mode-locked laser produces a 16.7 MHz repetition rate pulse train with a 1.4 ps pulse width, and the spectrum bandwidth is 2.17 nm. The results demonstrate that the SA supports soliton pulse shaping in the cavity at the fundamental frequency.
22 Dec 2014
TL;DR: In this paper, a linearization approach for a novel type of intensity-modulated directly-detected (IM-DD) analog photonic link based on digital processing technique was proposed and experimentally demonstrated.
Abstract: We propose and experimentally demonstrate a linearization approach for a novel type of intensity-modulated directly-detected (IM-DD) analog photonic link based on digital processing technique. In our scheme, the analog signal is intensity and orthogonally modulated on a pair of co-propagated photonic links, i.e. one of the two intensity modulations has a bias angle which is 90 degree difference from the other. At the remote end, the analog signal can be linearly recovered by a digital signal processing based on the direct detections of the link pair. We experimentally demonstrate our concept through a piece of polarization maintained fiber (PMF), a polarization modulator (PolM), a polarizer, and the dual-channel wavelength division multiplexing (WDM) technology. The PMF, PolM, and the polarizer constitute an asymmetric mach-zehnder modulator (A-MZM), whose bias angle can be tuned easily by tuning the input optical carrier wavelength. Experiment results show 26.8 dB suppression of the third-order intermodulation distortion (IMD3) compared with the traditional quadrature-biased IM-DD link is achieved. Compared with the previously-reported linearized phase- or polarization-modulated, in-phase/quadrature demodulation (PM-IQD or PolM-IQD) analog photonic links, our scheme has the advantage that neither the highly-coherent optical local oscillation nor the precise polarization alignment is required in the remote end.
22 Dec 2014
TL;DR: In this article, a novel radio-over-fiber (RoF) based digital receiver architecture for coherent heterodyne detection is presented, which demonstrates the application of using bandpass sampling in a RoF communications system to overcome the high sampling rate requirement of conventional receivers and front end hardware dependency.
Abstract: We have experimentally presented a novel radio-over-fiber (RoF) based digital receiver architecture for coherent heterodyne detection. It demonstrates the application of using bandpass sampling in a RoF communications system to overcome the high sampling rate requirement of conventional receivers and front-end hardware dependency. In particular, we modified the uniform bandpass sampling theorem to cope with frequency offset produced by independent free running optical local oscillator. Thereafter, a 40Mbit/s QPSK modulated data signal at 2.4GHz RF carrier frequency is experimentally demonstrated by using phase modulated and digital signal processing aided RoF links.
01 Oct 2014
TL;DR: In this article, the compensation of XMD nonlinearity in wide-band, multiple-carrier analog photonic link (APL) systems was demonstrated by low biasing the MZM, where the fundamental sidebands to XMD sidebands ratio was improved by more than 19 dB.
Abstract: We experimentally demonstrate the compensation of cross modulation distortion (XMD) nonlinearity which exists in wide-band, multiple-carrier analog photonic link (APL) systems. Such nonlinearity is caused by out-of-band signals due to the inherent nonlinear transfer function of Mach-Zehnder modulator (MZM). Instead of precisely emulating the transfer function of the whole nonlinear system in the digital domain, we digitally multiply the distorted signals by a compensating signal which can be extracted through a digital low-pass filtering. As a result, the XMD will be well suppressed. Theory analysis shows that only the bias angle should be known by the algorithm. By low biasing the MZM, the experiment shows a well-suppressed XMD, where the fundamental sidebands to XMD sidebands ratio is improved by more than 19 dB.
TL;DR: Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes, especially when the inserted fiber length is short.
Abstract: The performance of three wireless local-area network (WLAN) media access control (MAC) protocols is investigated and compared in the context of simulcast radio-over-fiber-based distributed antenna systems (RoF-DASs) where multiple remote antenna units (RAUs) are connected to one access point (AP) with different-length fiber links The three WLAN MAC protocols under investigation are distributed coordination function (DCF) in basic access mode, DCF in request/clear to send (RTS/CTS) exchange mode, and point coordination function (PCF) In the analysis, the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into accountResults show that adaptive PCF mechanism has better throughput performances than the other two DCF modes, especially when the inserted fiber length is short
01 Oct 2014
TL;DR: In this article, a multi-dimensional crest factor reduction (MD-CFR) is proposed to improve the performance of multi-band radio-over-fiber (RoF) links.
Abstract: A multi-dimensional crest factor reduction (MD-CFR) is proposed to improve the performance of multi-band radio-over-fiber (RoF) links. Cooperating with multi-dimensional digital predistortion (MD-DPD), MD-CFR increases the performance significantly for directly-modulated RoF links, in terms of error vector magnitude (EVM) and adjacent channel power ratio (ACPR). By implementing MD-CFR in conjunction with MD-DPD, more than 5 dB ACPR reduction is obtained, output EVMs are reduced from 11.83% and 12.47% to 7.51% and 7.26% for two bands respectively, while only a slight improvement to 11.58% and 10.78% is obtained solely using MD-DPD. As compared with the case solely using MD-DPD, the allowable RF input power applied to RoF links increases by ~1dB given an EVM threshold of 5%, indicating an distinct enhancement of RF power transmit efficiency.
11 Nov 2014
TL;DR: In this article, a frequency-conversion system of changing the input RF frequency to four different ones by adjusting modulators' electrical parameters was proposed, which needs only one frequency-fixed microwave source and can be applied in satellite repeaters.
Abstract: We propose one novel frequency-conversion system of changing the input RF frequency to four different ones by adjusting modulators' electrical parameters, which needs only one frequency-fixed microwave source and can be applied in satellite repeaters.
01 Jun 2014
TL;DR: In this article, a multi-dimensional digital predistortion based on memory polynomial model is experimentally studied for multi-band externally-modulated radio-over-fiber (RoF) systems, in terms of nonlinearity order, memory length, maximum tolerable RF input power and distorted signal feedback approach for model coefficients adaptation.
Abstract: Multi-dimensional digital predistortion based on memory polynomial model is experimentally studied for multi-band externally-modulated radio-over-fiber (RoF) systems, in terms of nonlinearity order, memory length, maximum tolerable RF input power, and distorted signal feedback approach for model coefficients adaptation. The experimental results show that the external modulator instead of photodetector contributes to the most of nonlinear distortions among which the cross-band distortions is dominant with respect to the in-band distortions. Based on the investigations, it is feasible to employ an auxiliary photodetector at the transmitter side to feedback the distorted signal for adapting the model coefficients. Moreover, the results also suggest us to implement a memoryless multi-dimensional digital predistortor with involving nonlinearity orders up to 5 for a practical multi-band externally-modulated RoF system. With the suggested parameters, the proposed multi-dimensional DPD technique is able to improve the RF input power tolerance by greater than 3 dB for each band in a two-band case.
TL;DR: In this paper, a photonic system is proposed to calibrate the instantaneous frequency and glitches of a fast frequency sweeping oscillator using a pseudo random bit sequence (PRBS) frequency comb.
Abstract: A photonic system is proposed to calibrate the instantaneous frequency and glitches of a fast frequency sweeping oscillator using a pseudo random bit sequence (PRBS) frequency comb. Its performance is demonstrated by simulations and experiments. A vector signal generator (Agilent E8257D), whose frequency ranges from 0.5 to 2.5 GHz and from 2.5 to 5 GHz, respectively, is calibrated. The deviation from linearity of frequency sweeping is measured to be less than 0.02%. As an extension of the calibrating system, the characterized sweeping oscillator is applied to multi-tone radio frequency (RF) measurement with an accuracy of 5 kHz and a resolution of 1 MHz. This technique will find applications in the field of electronic warfare and communication systems.
01 Aug 2014
TL;DR: In this article, the authors proposed and demonstrated a RF-to-Digital photonic link for relaying microwave signals over an optical fiber and linear converting the microwave signal to digital domain.
Abstract: We proposed and demonstrated a RF-to-Digital photonic link for relaying microwave signals over an optical fiber and linear converting the microwave signal to digital domain. The system uses two cascaded polarization modulators to achieve microwave-optoeletronic mixer. Two parallel polarization controllers (PC) and polarization beam splitter (PBS) are connected to the output of receiver PolM in order to realize I/Q intensity demodulation. We further show that by simply merging the coherent demodulation with DSP, the dynamic range of the system is significantly improved to 112dB-Hz2/3 at 14 GHz. In this scheme, the fluctuation of optical phase noise has no impact on the stable performance of the system.