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电气英文翻译2011-02-06三绕组变压器:three-columntransformerThrClnTrans双绕组变压器:double-columntransformerDblClmnTrans电容器:Capacitor并联电容器:shuntcapacitor电抗器:Reactor母线:Busbar输电线:TransmissionLine发电厂:powerplant断路器:Breaker刀闸(隔脱离关):Isolator分接头:tap电动机:motor有功:activepower无功:reactivepower电流:current容量:capacity 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反电势历史上的今天:电气专业英语一览英文全称缩写中文【A-G】2011-02-06。
3206IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 58, NO. 11, NOVEMBER 2010Photonic RF Phase Shifter Based on a Vector-Sum Technique Using Stimulated Brillouin Scattering in Dispersion Shifted FiberXiaoqiang Sun, Student Member, IEEE, Songnian Fu, Kun Xu, Junqiang Zhou, Perry Shum, Senior Member, IEEE, Jie Yin, Xiaobin Hong, Jian Wu, and Jintong LinAbstract—A photonic RF phase shifter is proposed and demonstrated based on a vector-sum technique using stimulated Brillouin scattering (SBS) in dispersion shifted fiber (DSF). Two optical sidebands are generated and introduced to the Brillouin processing module when an RF signal is modulated on a continuous-wave carrier by an electrooptic phase modulator. SBS amplification/depletion, as well as nonlinear SBS phase, is induced to the selective optical sideband due to the interaction between the optical sidebands and the pump wave in the DSF, thus resulting in the phase-to-intensity modulation conversion. The Brillouin erbium-doped fiber laser is implemented to generate the pump wave to fix the frequency difference between pump wave and optical sideband, which can make the phase shifter broadband. By a vector-sum technique, the phase-shifted RF signal is obtained after heterodyne mixing at the photodetector and the magnitude of the phase shift is determined by the amplitude ratio and nonlinear phase from SBS. Index Terms—Dispersion shifted fiber (DSF), microwave photonics, stimulated Brillouin scattering (SBS).I. INTRODUCTION ROADBAND RF phase shifters have played an important role in phased-array beamforming, smart antennas, and signal processing for electronic warfare applications [1], as well as other millimeter-wave signal processing and measurement systems. Most conventional active RF phase shifters are based on purely electrical devices, which face the limitations of instantaneous bandwidth and phase-shift range [2], while photonic techniques can provide the advantages such as immunity to electromagnetic interference (EMI), high bandwidth, low loss, compact size, and light weight. This has prompted the development of photonic techniques for broadband RF phase shifters.Manuscript received January 06, 2010; revised July 29, 2010; accepted July 30, 2010. Date of publication October 11, 2010; date of current version November 12, 2010. This work was supported in part by the National Natural Science Foundation of China under Grant 60702006, Grant 60736002, Grant 60837004, Grant 60736036, and Grant 60932004, the Program for New Century Excellent Talents under Grant 06-0093, the Program for Changjiang Scholars and Innovative Research Team under Grant IRT0609, the Program for Ministry of Science and Technology International Cooperation under Grant 2008DFA11670, the 111 Project under Grant B07005, and the project funded by the State Key Lab of Advanced Optical Communication Systems and Networks. X. Sun, K. Xu, J. Yin, X. Hong, J. Wu, and J. T. Lin are with the Key Laboratory of Information Photonics and Optical Communications, Ministry of Education in China, Beijing University of Posts and Telecommunications, Beijing 100876, China (e-mail: sunxq36@). S. Fu, J. Zhou, and P. Shum are with the Network Technology Research Centre, Nanyang Technological University, Singapore 637553. Color versions of one or more of the figures in this paper are available online at . Digital Object Identifier 10.1109/TMTT.2010.2074811BRecently, various approaches have been proposed to implement photonic-assisted RF phase shifters [2]–[11], and most of the techniques can be classified into two major kinds: heterodyne mixing [2]–[8] and vector-sum technique [9]–[12]. For instance, in the heterodyne mixing technique, fiber nonlinear effects such as stimulated Brillouin scattering (SBS) and cross-phase modulation (XPM) have been used to induce nonlinear phase shift into one of the two optical sidebands, which were generated by single sideband (SSB) modulation or optical carrier suppressed (OCS) modulation, thus an RF phase-shifted signal can be obtained by heterodyne mixing between the two sidebands at the photodetector (PD) [2], [3]. However, most heterodyne mixing techniques have the disadvantage of inevitable phase noise caused by separation and combination of the two optical sidebands. In the vector-sum technique, two sinusoidal signals, with the same frequency, but different amplitudes, are summed and generate an RF phase-shifted signal. The phase of the resultant signal can be shifted by changing the amplitudes of the two signals, and the amplitude ratio of the two signals can be controlled by employing some important components such as an integrated Mach–Zehnder modulator, a polarization maintain fiber, and a semiconductor optical amplifier (SOA) [9]–[12]. The theory of this vector-sum technique is very simple, but it suffers power variation, which is quite difficult to be avoided in practical applications. SBS in optical fibers has been widely applied in the area of microwave photonics such as processing of microwave signals in optical domain and improvement of transmission quality in high-speed analog-optic fiber links, due to its narrow-linewidth spectra and low threshold [13], [14]. More recently, we have characterized the SBS gain and loss spectra, and introduced it to the implementation of RF phase shifter [15], [16]. In this paper, we demonstrate a compact and stable RF phase shifter using electrooptic phase modulation (PM) and SBS in dispersion shifted fiber (DSF). Based on our previous work [16], we have extended the theoretical model, simulation, and experiment to make the implementation more reliable in practical applications. We induce the SBS amplification/depletion, as well as nonlinear phase shift to the selective optical sideband, thus resulting in the PM to intensity modulation conversion in DSF. At the PD, two sinusoidal signals are generated by beating between the two sidebands and optical carrier. The phase and amplitude of the two signals can be controlled by the power of the pump wave, resulting in a broadband RF phase shifter. In this scheme, the optical sidebands co-propagate in a single fiber resulting in a low phase noise, compact, and stable implementation.0018-9480/$26.00 © 2010 IEEESUN et al.: PHOTONIC RF PHASE SHIFTER BASED ON VECTOR-SUM TECHNIQUE USING SBS IN DSF3207is the Bessel funcwhere is the modulation index, and tion of the first kind of order . The modulation index is re, where lated to the input signal amplitude by is the half-wave voltage of the phase modulator. Under small-signal conditions, only the first-order sidebands need to be considered and (4) can be further simplified asFig. 1. Schematic diagram of the photonic RF phase shifter.This paper is organized as follows. Section II illustrates the principle of operation where the vector-sum technique and Brillouin processing of the selective optical sidebands are discussed in detail. Pump wave generation from a Brillouin fiber laser and the overall implementation for the photonic RF phase shifter is presented in Section III. The experimental demonstration of the approach is given in Section IV and the main conclusions are summarized in Section V. II. PRINCIPLE OF OPERATION In the vector-sum technique [10], two sinusoidal signals with , but different amplitudes ( and same angular frequency ) and phase difference are summed into one sinusoidal signal, which is given by (1) where (2) (3) The phase of the summed signal can be controlled by adjusting and the original phase difference the amplitude ratio . In our scheme, PM is employed to generate two sinusoidal signals, while the Brillouin processing module is used to change the amplitude ratio and original phase difference. As shown in is modulated onto Fig. 1, an input RF signal the optical carrier by an electrooptic phase modulator (EOPM). After the Brillouin processing, the first-order upper and lower sideband experiences depletion and amplification, respectively, and PM to intensity modulation conversion is realized at the optical-to-electronic (O/E) conversion module. Due to the intrinsic modulation nonlinearity in the EOPM, higher order harmonics would be genwith angular frequencies erated even in the case of small-signal modulation [17]. The complex amplitude of the phase-modulated optical signal after the EOPM can be written as [17](5) where is the angular frequency of the optical carrier and is the complex amplitude of the original input optical carrier. Based on the property of Bessel functions, we have when is odd. From (5), we can observe that the two first-order sidebands are out of phase at the output of the EOPM, which is different from the intensity modulation where the two sidebands are in phase. Therefore, the RF signal cannot be recovered because the beating between the carrier and upper sideband exactly cancels the beating between the carrier and lower sideband after direct detection at the PD. In our scheme, SBS is used to break the “ -out-of-phase” relation between the upper and lower sideband. After the Brillouin processing module, the complex amplitude of optical signals is given by(6) where , and are the amplitudes of the optical lower sideband, upper sideband, and carrier, respectively, while , are the nonlinear phase shift caused by SBS in the DSF. and In standard single-mode fiber (SMF), the intrinsic dispersion can also realize the PM to intensity modulation, and the transfer function of the dispersive fiber can be written as [17] (7) where is the second-order dispersion coefficient of the optical fiber, and is fiber length. It is noted that the transfer function fluctuates with frequency of the input RF signal, resulting in the power fading effect. Therefore, we employ 1 km of DSF in our implementation, and the dispersive affects on the power variation can be ignored. Here, the nonlinear SBS effect in DSF is analyzed, and detailed Brillouin processing on the two sidebands is presented. In (6), the amplitudes of the optical sidebands and carrier are given by (8) and the gain is written as (9)(4)3208IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 58, NO. 11, NOVEMBER 2010with , the pump wave power, , the effective fiber length, , the effective core area, , the fiber loss, and , the fiber can also represent loss caused length. It is noted that the gain by Brillouin depletion on the lower sideband by a negative gain coefficient. The SBS gain coefficient is given by [18]the lower sideband or upper sideband. When the Brillouin freof the pump wave is higher than the upper sidequency shift band, amplitude gain and nonlinear phase shift is introduced only to the upper sideband resulting in a simplified ac current (17)(10) where is the full wdith at half maximum (FWHM) Brillouin is the frequency detuning of the th-order linewidth and sideband. The peak Brillouin gain coefficient is [18]where(18) (19) For lower sideband amplification/depletion, the ac current is given by (20) where (21) (22)(11) and derived from the physical constants , the index of refraction, , the specific density, , the acoustic velocity, , the elasto-optic coefficient, , the pump wavelength, and , the light speed in vacuum. We can also obtain the nonlinear phase for the upper or lower sideband from [18] shift(12) represents the first-order upper and lower sidewhere band. Finally, according to the above derivation, the ac-electrical current of the RF signal after heterodyne mixing at the PD can be expressed by Here we see the induced phase shifts are related to both the nonlinear phase shift and SBS gain, and together, increase the overall tuning range of the RF phase shift. We can also observe that the RF amplitude varies with respect to the SBS gain and phase shift. This variation can be overcome by post-detection processing in the electrical domain after photodetection. In the traditional vector-sum technique, the phase shift would be expected to be tuned simply by changing the relative amplitude of two signals that have a given fixed phase shift (typically they are in quadrature). In our SBS-based scheme, both the SBS gain and inherent SBS nonlinear phase shift are induced to the optical sideband. After heterodyne mixing at the PD, two sinusoidal signals are generated by beating of the optical carrier and two sidebands, of which the phase shift is determined by the power of pump wave. By the vector-sum technique, a phase shifted RF signal is obtained and the phase shift is determined by the phase shift and amplitude ratio of the two signals. According to (16), the SBS nonlinear phase shift is beneficial to the increasing of the overall tuning range in this RF phase-shifter implementation. III. IMPLEMENTATION AND SIMULATION The proposed photonic RF phase shifter is theoretically presented in the above section, and we can find that the frequency higher than that of the upper or of the pump wave should be lower sideband. This makes it difficult to adjust the wavelength of the pump wave with respect to the input broadband RF signal. Here we implement the phase shifter based on the Brillouin erbium-doped fiber laser [13], which can provide the pump wave relative to the frequency of at a frequency down-shifted by the lower sideband. Due to this frequency-locking mechanism, the implementation of this phase shifter would be suitable for(13) where is the responsivity of the photodiode in units amps/ watt. It is clear that the phase shift is induced into the resultant sinusoidal current given by (14) where(15) (16) In order to increase the tuning range of the phase shift, we use frequency-selective SBS amplification/depletion of eitherSUN et al.: PHOTONIC RF PHASE SHIFTER BASED ON VECTOR-SUM TECHNIQUE USING SBS IN DSF3209Fig. 2. Implementation of the Brillouin erbium-doped fiber laser for pump wave generation and RF phase shifter.broadband RF signals, and the bandwidth is only limited by that of the EOPM and PD. The implementation of the photonic RF phase shifter is shown in Fig. 2, in which the Brillouin erbium-doped fiber laser is constructed and used for pump wave generation. A continuous wave (CW) is generated from the narrow-linewidth distributed feedback laser diode (DFB-LD). An RF signal from a network analyzer is modulated onto the CW carrier by an EOPM, generating two first-order sidebands, which are out of phase. The following fiber loop is used to implement the Brillouin erbium-doped fiber laser, which consists of 200-m DSF, a tunable optical filter (TOF), and an erbium-doped optical fiber amplifier (EDFA). The PM-generated two first-order sidebands and optical carrier enter the 200-m DSF fiber cavity through the optical circulator. Due to Brillouin scattering in the DSF, the weak backward optical waves are generated and propagate in clockwise direction in the loop. The ultra-narrow TOF is used to suppress other modes and keep the pure pump wave at a frequency relative to the frequency of the lower sidedown-shifted by band. The EDFA is used to boost the pump wave with enough and controllable power. At the upper path of the coupler with a ratio of 10:90, the PM-generated sidebands and carrier are introduced to the 1-km DSF. Simultaneously, the narrow linewidth and high power pump wave is generated from the Brillouin erbium-doped fiber laser in the lower path. Through the 3-dB coupler, the pump wave enters the same DSF in a counterclockwise direction and counter-propagates with the PM-generated optical signals. Two optical isolators (ISOs) are used to ensure unidirectional propagation and prevent the backward signals entering into the loop. After Brillouin processing in the DSF, the SBS amplified/depleted sidebands are mixed with the optical carrier to generate two sinusoidal signals. By the vector-sum technique, the two sinusoidal signals result in a phase-shifted electrical sinusoidal signal at the PD, and the phase shift is determined by the injecting current of the EDFA. This RF phase shifter uses an all optical fiber construction, and thus, is especially suitable to microwave photonics applications. In order to numerically investigate the proposed SBS-based photonic RF phase shifter, we have a simulation on the phase shift and amplitude variation with respect to the pump power of the EDFA according to the theoretical deduction in Section II. The relationship between the SBS gain/nonlinear phase shift and EDFA pump power has been previously studied by Loayssa et al., and a further experiment on the SBS gain and nonlinearFig. 3. Simulated RF amplitude attenuation and phase shift (with and without SBS nonlinear phase shift) versus the pump power of the EDFA.Fig. 4. Proof-of-concept experimental setup.phase shift has been carried out in [13]. Based on these measured results and (15) and (16), we can plot the relationship between RF phase shift/amplitude and the power in the EDFA 980-nm pump. In this simulation, when the EDFA pump powers vary from 10 to 80 mW, both RF phase shift and amplitude variation can be observed. Fig. 3 illustrates the simulation results, where the phase shift of the RF sinusoidal signal has an overall tuning range of more than 85 with respect to the increasing of 980-nm pump power in EDFA. Meanwhile, the amplitude of the signal also suffers the power variation, which is the intrinsic problem in the vector-sum technique and this can be overcome by carried out amplitude compensation in the electrical domain after PD. IV. PROOF-OF-CONCEPT EXPERIMENTS A. Experimental Setup We have also carried out a proof-of-concept experiment to demonstrate the Brillouin processing of the sidebands and the RF phase shift caused by SBS. Fig. 4 illustrates the proof-ofconcept experimental setup. A tunable laser source (TLS) with wavelength resolution of 1 pm is employed to generate a pump wave instead of a Brillouin erbium-doped fiber laser. In this way, we can observe the Brillouin gain/depletion of optical sidebands by simply sweeping the wavelength of the TLS. A CW launched by a DFB-LD with initial power of 8 dBm at 1560 nm is introduced to the EOPM driven by a 12-GHz RF signal from a microwave oscillator source. Two first-order sidebands with out3210IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 58, NO. 11, NOVEMBER 2010of phase are generated and amplified by an EDFA. The bandpass filter (BPF) is used to suppress the noise power induced by the EDFA, and the ISO is used to prevent the pump wave entering into the EDFA and laser. The PM-generated first-order sidebands and optical carrier are injected into the 1-km DSF, the zero-dispersion wavelength of which is around 1560 nm, so the wavelength of the CW optical carrier from the DFB-LD is selected to be 1560 nm in order to eliminate chromatic dispersion in the optical fiber. At the other end of the DSF, a TLS is used to launch the pump wave with controllable power and the wavelength can be swept with a step length of 1 pm. The pump wave transmits through the circulator and counter-propagates with the PM-modulated optical signals in the DSF, where SBS higher than takes place when the frequency of the TLS is the upper or lower sideband. After the Brillouin processing, the sidebands and carrier are heterodyne mixed at the PD via the circulator. Finally, the beating between two sidebands and optical carrier generates two sinusoidal signals, which produces the summed phase-shifted RF signal by a vector-sum technique. B. Experimental Results The wavelength of the optical carrier from DFB-LD is 1560 nm and the frequency of the RF signal is 12 GHz. Firstly, we characterize the affect of SBS gain on the lower and upper sidebands. By sweeping the wavelength of the TLS, we can inspect the optical spectra of the PM-modulated optical signal by an optical spectra analyzer. When the frequency of the TLS is tuned 21.8 GHz higher than that of the optical carrier, the left sideband is amplified, and this amplification of the left sideband is clearly shown in Fig. 5(a). The gain of the left (upper frequency) sideband is 16 dB for a pump power of 3.8 mW. This different power of the two sidebands can realize the conversion of PM to intensity modulation. Similarly, the right sideband can also be amplified by adjusting the wavelength of the TLS, as shown in Fig. 5(b). By characterizing the optical spectra, is we can also observe that the Brillouin frequency shift around 9.8 GHz in the 1-km DSF. In Fig. 5(a), there is a raised peak besides the left sideband, which results from the Fresnel reflection of the pump wave. This is helpful to adjust the wavelength of the TLS in the experiment operation. However, the reflection would be heterodyne mixed with the optical carrier at PD, producing very high RF signal noise, thus it is necessary to reduce the Fresnel reflections mainly generated at optical fiber connectors in this implementation. We use a digital oscilloscope to track the waveform after the PD in the experiment, as shown in Fig. 6. It is obvious that there is no signal displayed for PM and direct detection without SBS processing. When the TLS launches the pump wave with initial power of 12 dBm, the RF signal is recovered due to the Brillouin amplification/depletion of one of the two sidebands. By increasing the bias current of the EDFA, the amplitude of the waveform is boosted, and the time delay is also observed between the adjacent signals. When the bias current of the EDFA is tuned from 146 to 228 mA, a phase shift of 90 can be observed on the RF signal. It is noted that when the bias current is higher, the noise of the RF signal becomes more serious, and this is caused by the Fresnel reflection of the pump wave. In order to suppressFig. 5. Measured optical spectra at port 3 of the circulator. (a) Upper sideband is amplified. (b) Lower sideband (in frequency domain) is amplified.Fig. 6. Measured waveform for 12-GHz RF signal at different bias current on the EDFA.the noise, refractive index matching liquids can be used to reduce the Fresnel reflections at optical fiber connectors. In addition, due to the frequency-locked mechanism of the Brillouin erbium-doped fiber laser, the carrier frequency of the input RF signal can be tens of gigahertz and only limited by the bandwidth of the phase modulator and PD (higher than 70 GHz).SUN et al.: PHOTONIC RF PHASE SHIFTER BASED ON VECTOR-SUM TECHNIQUE USING SBS IN DSF3211However, the bit rates of the baseband data are lower than the SBS gain linewidth (approximately 50 MHz). This drawback can be overcome by the developing techniques. The SBS gain bandwidth can be extended to 3-dB bandwidth of 1.5 GHz and 10-dB bandwidth of 2 GHz by controlling the spectrum shape of the pump wave using binary phase-shift keying modulation with a pulse pattern generator [19], which allows very high bit rates. V. CONCLUSION A photonic-assisted RF phase shifter has been proposed and demonstrated based on a vector-sum technique using SBS in DSF. PM to intensity modulation conversion is realized by inducing narrow-linewidth SBS gain/depletion spectra and nonlinear SBS phase to the selective optical sideband. This phase-to-intensity modulation conversion results in the phase shift of the summed RF sinusoidal signal after heterodyne mixing at the PD. This vector-sum technique is very stable and available without any separation and combination of the optical sidebands. In addition, the Brillouin erbium-doped fiber laser structure is incorporated in order to make it suitable in broadband required application and prevent the wavelength fluctuation. REFERENCES[1] A. Dreher, N. Niklasch, F. Klefenz, and A. Schroth, “Antenna and receiver system with digital beamforming for satellite navigation and communications,” IEEE Trans. Microw. Theory Tech., vol. 51, no. 7, pp. 1815–1821, Jul. 2003. [2] A. Loayssa and F. Lahoz, “Broad-band RF photonic phase shifter based on stimulated Brillouin scattering and single-sideband modulation,” IEEE Photon. Technol. Lett., vol. 18, no. 1, pp. 208–210, Jan. 2006. [3] Y. Dong, H. He, and W. Hu, “Photonic microwave phase shifter/modulator based on a nonlinear optical loop mirror incorporating a Mach–Zehnder interferometer,” Opt. Lett., vol. 32, no. 7, pp. 745–747, Apr. 2007. [4] P. Peng et al., “40 GHz phase shifter based on semiconductor laser,” Electron. Lett., vol. 44, no. 8, pp. 520–521, Apr. 2008. [5] M. Fisher and S. Chuang, “A microwave photonic phase-shifter based on wavelength conversion in a DFB laser,” IEEE Photon. Technol. Lett., vol. 18, no. 16, pp. 1714–1716, Aug. 2006. [6] P. Peng et al., “RF phase shifter using a distributed feedback laser in microwave transport systems,” Opt. Exp., vol. 17, no. 9, pp. 7609–7614, Apr. 2009. [7] D. B. Adams and C. K. Madsen, “A novel broadband photonic RF phase shifter,” J. Lightw. Technol., vol. 26, no. 15, pp. 2712–2717, Aug. 2008. [8] Q. Chang, Q. Li, Z. Zhang, M. Qiu, T. Ye, and Y. Su, “A tunable broadband photonic RF phase shifter based on a silicon microring resonator,” IEEE Photon. Technol. Lett., vol. 21, no. 1, pp. 60–62, Jan. 2009. [9] S. Lee et al., “Demonstration of a photonically controlled RF phase shifter,” IEEE Microw. Guided Wave Lett., vol. 9, no. 9, pp. 357–359, Sep. 1999. [10] K. Lee, Y. Jhon, and W. Choi, “Photonic phase shifters based on a vector-sum technique with polarization-maintaining fibers,” Opt. Lett., vol. 30, no. 7, pp. 702–704, Apr. 2005. [11] J. Coward, T. Yee, C. Chalfant, and P. Chang, “A photonic integrated-optic RF phase shifter for phased array antenna beamforming applications,” J. Lightw. Technol., vol. 11, no. 12, pp. 2201–2205, Dec. 1993. [12] W. Xue, F. Ohman, S. Blaaberg, Y. Chen, S. Sales, and J. Mork, “Broadband microwave photonic phase shifter based on polarisation rotation,” Electron. Lett., vol. 44, no. 11, pp. 684–685, May 2008. [13] A. Loayssa, D. Benito, and M. Garde, “Optical carrier Brillouin processing of microwave photonic signals,” Opt. Lett., vol. 25, no. 17, pp. 1234–1236, Sep. 2000.[14] T. Horiguchi et al., “Development of a distributed sensing technique using Brillouin scattering,” IEEE J. Lightw. Technol., vol. 13, no. 7, pp. 1296–1301, Jul. 1995. [15] X. Sun et al., “Characterization of SBS gain and loss spectra using Fresnel reflections and interaction of two sidebands,” in OFC/NFOEC, San Diego, CA, Mar. 2010, Paper JWA11. [16] X. Sun et al., “RF phase shifter based on a vector-sum technique using electrooptic phase modulator and SBS in optical fiber,” in Asia–Pacific Microw. Photon. Conf., Hong Kong, Apr. 2010, Paper TA3-4. [17] H. Chi, X. Zou, and J. Yao, “Analytical models for phase-modulationbased microwave photonic systems with phase modulation to intensity modulation conversion using a dispersive device,” IEEE J. Lightw. Technol., vol. 27, no. 5, pp. 511–523, Mar. 2009. [18] R. Waarts, A. Friesem, and Y. Hefetz, “Frequency-modulated to amplitude-modulated signal conversion by a Brillouin-induced phase change in single-mode fibers,” Opt. Lett., vol. 13, no. 2, pp. 152–154, Feb. 1988. [19] T. Tanemura, Y. Takushima, and K. Kikuchi, “Narrowband optical filter with a variable transmission spectrum using stimulated Brillouin scattering in optical fiber,” Opt. Lett., vol. 27, pp. 1552–1554, Sep. 2002.Xiaoqiang Sun (S’08) was born in Hubei, China, in 1984. He received the B.E. degree in optoelectronics from the Huazhong University of Science and Technology (HUST), Wuhan, China, in 2007, and is currently working toward the Ph.D. degree in electromagnetic field and microwave technique at the Beijing University of Posts and Telecommunications (BUPT), Beijing, China. He has been with the Network Technology Research Center (NTRC), Nangyang Technological University, Singapore, as an exchange student for six months. He is currently with the Key Laboratory of Information Photonics and Optical Communication (IPOC), Ministry of Education, BUPT. His main research interests include radio-over-fiber systems, microwave photonic signal processing, and high-speed optical communications.Songnian Fu was born in Yunnan, China in 1975. He received the B.Sc. and M.Sc. degrees from Xiamen University, Xiamen, Fujian, China, in 1998 and 2001, respectively, and the Ph.D. degree from Beijing Jiaotong University, Beijing, China, in 2004. In 2005, he joined the Network Technology Research Center (NTRC), Nanyang Technological University, Singapore, as a Research Fellow. His research interests include optical packet switching and SOA-based all-optical sub-systems.Kun Xu received the Ph.D. degree in physical electronics from Tsinghua University, Beijing, China, in 2003. He is currently an Associate Professor with the Key Laboratory of Information Photonics and Optical Communication (IPOC), Ministry of Education, Beijing University of Posts and Telecommunications, Beijing, China. His current research interests include high-speed optical communication, all-optical signal processing, and radio-over-fiber techniques.Junqiang Zhou, photograph and biography not available at time of publication.Perry Shum (M’90–SM’02) photograph and biography not available at time of publication.。
All-optical dynamic grating generation based on Brillouin scattering in polarization-maintainingfiberKwang Yong Song,1,*Weiwen Zou,2Zuyuan He,2and Kazuo Hotate21Department of Physics,Chung-Ang University,Seoul,Korea2Department of Electronic Engineering,The University of Tokyo,Tokyo,Japan*Corresponding author:songky@cau.ac.krReceived January30,2008;revised March20,2008;accepted March20,2008;posted March25,2008(Doc.ID92171);published April22,2008We report a novel kind of all-optical dynamic grating based on Brillouin scattering in a polarization main-tainingfiber(PMF).A moving acoustic grating is generated by stimulated Brillouin scattering between writ-ing beams in one polarization and used to reflect an orthogonally polarized reading beam at different wave-lengths.The center wavelength of the grating is controllable by detuning the writing beams,and the3dBbandwidth ofϳ80MHz is observed with the tunable reflectance of up to4%in a30m PMF.©2008OpticalSociety of AmericaOCIS codes:050.2770,060.2310,190.4370,290.5900.A high-speed and reconfigurable dynamic grating canbe used as a powerful tool in communication or sen-sor applications as a tunable opticalfilter,an opticalswitch,and a distributed sensor[1–4].The currentlyavailable scheme is to build up a gain or absorptiongrating in an Er-dopedfiber(EDF)by counterpropa-gating optical waves with the same optical frequency.However,such an EDF-based dynamic grating suf-fers a couple of significant problems,such as diffi-culty in separating the writing and reading beams[1,2]or an amplified spontaneous emission(ASE)noise due to optical pumping[3,4],which can givedisadvantages in practical applications.In this Letter,we demonstrate a novel kind of dy-namic grating based on stimulated Brillouin scatter-ing(SBS)in a polarization-maintainingfiber(PMF).An acoustic phonon generated by SBS between twocounterpropagating writing beams of one polariza-tion is used as a tunable and dynamic grating for theorthogonally polarized reading beam at differentwavelengths satisfying the phase-matching condi-tion.The reflected probe wave experiences an ordi-nary Brillouin shift by the Doppler effect,and the op-tical frequency difference between the writing andthe reading beams is determined by the birefringenceof the PMF.The basic theory,the operation principle,and the experimental configuration are described,and the results are explained using a simplifiedtheory of Brillouin scattering.SBS is generally modeled as a three-wave interac-tion between the pump͑1͒,Stokes͑2͒,and acousticwaves.When a phase-matching condition is satisfied(1−2=B,B being the Brillouin frequency),strongenergy transfer from the pump to the counterpropa-gating Stokes wave takes place generating acousticwaves,which stimulates the process.TheB is givenby following equation[5]:B=2nV a,͑1͒where n,V a,andare the refractive index,the veloc-ity of the acoustic wave,and the optical wavelength,respectively.In a PMF(or any medium with birefrin-gence),optical waves with two principal polarizations(i.e.,x and y polarization)experience differentB’sowing to their different refractive indexes.Consider-ing that the acoustic wave generated by SBS is a lon-gitudinal one that is free of the transversal polariza-tion[6],an interesting condition can be reached thatthe x-and the y-polarized optical waves in a PMFshow the sameB at different wavelengths.When thedispersion of the acoustic wave is ignored,the condi-tion is expressed by following equations:2n x V ax=2n y V ay,͑2͒n xx=n yy,͑3͒where n x,y andx,y(if n xϾn y,yϾx)are the refrac-tive indexes and the optical frequencies in x and y po-larizations,respectively.With⌬n=͑n x−n y͒ 1and⌬=y−x (x ory),Eq.(3)is simplified to⌬=⌬nn.͑4͒Since the SBS-induced acoustic waves can beviewed as moving gratings for the reflection of thepump wave without polarization dependence,it is ex-pected that acoustic waves generated by SBS be-tween the x-polarized pump and Stokes waves at theoptical frequencyx will show strong reflectance tothe y-polarized pump wave at the frequency ofx+⌬.Considering that the intensity and the wave-length of the acoustic waves are easily tuned by con-trolling the x-polarized“writing”beams,one may ex-pect the SBS in a PMF to play a role of a tunabledynamic grating.We composed an experimental setup,as shown inFig.1.For the writing of the dynamic grating,a926OPTICS LETTERS/Vol.33,No.9/May1,20080146-9592/08/090926-3/$15.00©2008Optical Society of America1550nm laser diode was used as a light source,and the output power was divided by a 50/50coupler.A single-sideband modulator (SSBM)and a microwave synthesizer were used to generate the Stokes wave (pump2)of the writing beams,and the output was amplified and polarized by an EDF amplifier (EDFA)and an x polarizer.The Brillouin pump wave (pump1)of the writing beams was prepared by amplifying the original wave with the same polarization as that of pump2.Pump1and the pump2were launched into a PMF in opposite direction to each other through po-larization beam combiners (PBC1,PBC2).The PMF was a PANDA fiber manufactured by Fujikura with a 30m length and a nominal ⌬n ϳ6.2ϫ10−4at the wavelength of 1300nm.For a reading beam (probe),a tunable laser with an operating wavelength near 1550nm was used as a light source after being polar-ized in the y axis.The output was launched into the PMF in the direction of the pump1through a polarization-maintaining circulator and PBC1.The transmitted power of the probe was measured using a power meter,and the backreflected spectrum was monitored using an optical spectrum analyzer (OSA)through a y polarizer.At first,we measured the Brillouin gain spectra of the PMF in the x and y axes.The B in the x axis was measured to be 10.502GHz,and the difference of the B ’s of two polarizations was ϳ3.6MHz,as depicted in the inset of Fig.1,which corresponds to ⌬n ϳ5.0ϫ10−4by Eq.(1).To induce the SBS in the x axis,we launched pump1and the pump2in the x axis with the output powers of 630and 10mW,respectively,setting their frequency offset ͑⌬f ͒to 10.502GHz.For the detection of the dynamic grating,the fre-quency of the probe was tuned at the higher fre-quency region while monitoring the spectrum with the OSA,and the result is shown in Fig.2.When ⌬(the frequency difference between pump1and the probe)was ϳ72.6GHz,a large reflection of the probe was observed (black curve)as a result of the dynamic grating at the frequency detuned from the probe by the same amount as that between pump1and pump2.When one of the pumps (pump1)was turned off,the dynamic grating disappeared as depicted by the gray curve although the probe was still propa-gated as confirmed by the Rayleigh scattering seen at the probe frequency.In both cases,the x -polarizedpumps were observed in spite of the use of the y po-larizer in front of the OSA,which originated from the finite extinction ratio ͑ϳ20dB ͒of the polarizing com-ponents.The small peaks near pump1correspond to the first-and second-order anti-Stokes waves that were suppressed in the SSBM used for the genera-tion of pump2.Figure 3(a)shows the reflectance of the dynamic grating with respect to ⌬,calculated from the ratio of the input and the reflected powers of the probe,while the pump powers were maintained to the same as the first measurement.The maximum reflectance was ϳ4%,and the 3dB width was ϳ80MHz.The overall shape looks asymmetric,which could be at-tributed to the irregularity of the local birefringence in the PMF.We fixed ⌬to 72.6GHz and swept ⌬f ,the fre-quency offset between pump1and pump2.The result is depicted in Fig.3(b),which fits well with a Lorent-zian curve with a 3dB width of 28MHz,similar to the ordinary Brillouin gain spectrum of the fiber.The dependence of the grating reflectance on the pump powers was measured by varying one of the pump powers with the other fixed,while ⌬was kept at 72.6GHz.Figures 4(a)and 4(b)show the reflec-tance of the grating as a function of the power of pump1and pump2,respectively.It is remarkable that the reflectance grows in an exponential form to some definite value with the power of pump1asFig. 1.Experimental setup:LD,laser diode;SSBM,single-sideband modulator;EDFA,Er-doped fiber ampli-fier;PBC,polarization beam combiner;OSA,optical spec-trum analyzer.The inset is the Brillouin gain spectra of the fiber under test in x and ypolarizations.Fig.2.Optical spectra monitored by an OSA in the gen-eration of dynamic grating.The gray curve corresponds to the case that one (pump1)of the writing beams is turned off,and the black curve with both writing beams turnedon.Fig.3.(Color online)(a)Reflectance of the dynamic grat-ing as a function of ⌬,the frequency difference between the pump1and the probe.(b)Reflectance of the dynamic grating at a fixed ⌬͑72.6GHz ͒as a function of the ⌬f ,the frequency offset between pump1and pump2.The curve shows the result of a Lorentzian fit.May 1,2008/Vol.33,No.9/OPTICS LETTERS 927shown in Fig.4(a),while it is linearly dependent on the power of pump2as depicted in Fig.4(b),where the result matches well with a linear fit with the slope of 3.8ϫ10−4͑/mW ͒.The slight inconsistency in the reflectance values of Figs.4(a)and 4(b)came from long-term drift of the optical frequencies of the pump and the probe lasers,whose effect was negli-gible in each measurement.The difference in dependence of the grating reflec-tance on the pump powers can be explained by the re-lation of the Brillouin gain and the reflectance.In the generation of the dynamic grating,the increased power of pump2through the gain of the SBS can be viewed as the reflection of pump1.Additionally,we may assume that pump1and the probe experience al-most the same reflectance,since they share the same acoustic grating.Therefore,if the pump depletion is ignored (i.e.,small reflection of pump1),the reflec-tance of the dynamic grating R can be estimated from the gain of the SBS [5]as follows:R =P probe out P probein Ϸ⌬P 2P 1=P 2͑e ͑g B P 1L eff /A eff ͒−1͒P 1,͑5͒where g B ,L eff ,A eff ,P 1,and P 2are the Brillouin gain coefficient,the effective length of the fiber,the mode effective area,the power of pump1,and the power of pump2,respectively.In Eq.(5),one can see that the reflectance of the grating linearly depends on P 2,and the reflectance will grow in an exponential form ac-cording to P 1if the gain is large enough.The final point in Fig.4(a)with pump1of 800mW looks devi-ated from the form of the exponential growth,which could be attributed to the gain saturation with the pump depletion due to too large amplification of pump2.The reflectance offset appearing in the lin-early fitted graph of Fig.4(b)can be attributed to the amplification of the SBS noise induced by the strong pump1.We think detailed properties of the grating can be explained by coupled wave equations (by five-wave mixing instead of the three-wave one in the ordinary case of the SBS),and there could be more factors that have an effect on the grating reflectance such as the probe power.Further research is needed on this point.The relation between the optical frequencies of pump1and the probe under the condition of the dy-namic grating generation is depicted in Fig.5,which shows good linearity as expected from Eq.(3).In the measurement,the powers of the pumps and the probe were kept constant,and the variation of B was negligible ͑Ͻ1MHz ͒.In conclusion,we have demonstrated a novel all-optical dynamic grating based on stimulated Bril-louin scattering in a polarization-maintaining fiber.The center frequency of the grating was ϳ72.6GHz detuned from the writing beam frequency,and the re-flectance as well as the peak frequency could be tuned by controlling the power and the frequency of the writing beam.Considering the high sensitivity of the dynamic grating to local birefringence [see Eq.(4)]as well as the high on–off extinction ratio ͑Ͼ60dB ͒,the spectral flexibility [7],and the short re-sponse time ͑ϳ10ns ͒[5]of the SBS,we believe the SBS-based dynamic grating has large potential for practical applications such as an all-optical switch and a highly sensitive fiber sensor.The authors are grateful to Luc Thévenaz from EPFL in Lausanne,Switzerland,for his contribution to the development of the idea.This work was sup-ported by the “Grant-in-Aid for Creative Scientific Research”and the “Global Center of Excellence Pro-gram”from the Ministry of Education,Culture,Sports,Science and Technology,Japan.K.Y.Song was supported by the Korea Research Foundation Grant funded by the Korean Government (MOE-HRD)(KRF-2007-331-C00116).References1.S.J.Frisken,Opt.Lett.17,1776(1992).2.B.Fischer,J.L.Zyskind,J.W.Sulhoff,and D.J.DiGiovanni,Opt.Lett.18,2108(1993).3.X.Fan,Z.He,Y.Mizuno,and K.Hotate,Opt.Express 13,5756(2005).4.X.Fan,Z.He,and K.Hotate,Opt.Express 14,556(2006).5.G.P .Agrawal,Nonlinear Fiber Optics ,2nd ed.(Academic,1995).6.W.Zou,Z.He,and K.Hotate,IEEE Photon.Technol.Lett.18,2487(2006).7.M.González Herráez,K.Y.Song,and L.Thávenaz,Opt.Express 14,1395(2006).Fig.5.(Color online)Optical frequency of the probe as a function of the frequency of pump1under the condition of the dynamic grating generation.The line is the result of a linearfit.Fig.4.(Color online)Reflectance of the dynamic grating as a function of pump power in the case of (a)pump1varied and pump2fixed to 10mW,and (b)pump2varied and pump1fixed to 200mW.The line is the result of a linear fit.928OPTICS LETTERS /Vol.33,No.9/May 1,2008。
零中频接收机设计2013年09月24日13:09eechina分享关键词：零中频,接收机作者在：冷爱国，TI公司China Telecom system摘要相较传统的超外差接收机，零中频接收机具有体积小，功耗和成本低，以及易于集成化的特点，正受到越来越广泛关注，本文结合德州仪器（TI）的零中频接收方案（TRF3711），详细分析介绍了零中频接收机的技术挑战以及解决方案。
概述零中频接收机在几十年前被提出来，工程中经历多次的应用实践，但是多以失败告终，近年来，随着通信系统要求成本更低，功耗更低，面积更小，集成度更高，带宽更大，零中方案能够很好的解决如上问题而被再次提起。
本文将详细介绍零中频接收机的问题以及设计解决方案，结合TI的零中频方案TRF3711测试结果证明，零中频方案在宽带系统的基站中是可以实现的。
1、超外差接收机1.1超外差接收机问题为了更好理解零中频接收的优势，本节将简单总结超外差接收机的一些设计困难和缺点。
图一是简单超外差接收机的架构，RF信号经过LNA(低噪声放大器)进入混频器，和本振信号混频产生中频信号输出，镜像抑制滤波器滤出混频的镜像信号，中频滤波器滤除带外干扰信号，起到信道选择的作用，图中标示了频谱的搬移过程及每一部分的功能。
在超外差接收机种最重要的问题是怎样在镜像抑制滤波器和信号选择滤波器的设计上得到平衡，如图一所示，对滤波器而言，当其品质因子和插损确定，中频越高，其对镜像信号的抑制就越好，而对干扰信号的抑制就比较差，相反，如果中频越低，其对镜像信号的抑制就变差，而对干扰信号的抑制就非常理想，由于这个原因，超外差接收机对镜像滤波器和信道滤波器的选择传输函数有非常高的要求，通常会选用声表滤波器(SAW)，或者是采用高阶LC滤波器，这些都不利于系统的集成化，同时成本也非常高。
在超外差接收机中，由于镜像抑制滤波器是外置的，LNA必须驱动50R负载,这样还会导致面积和放大器噪声，增益，线性度，功耗的平衡性问题。
第48卷第S1期红外与激光工程2019年4月Vol.48No.S1Infrared and Laser Engineering Apr.2019利用循环移频环路产生的倍频因子可调谐太赫兹信号解陶然,王肇颖,袁泉,蒋振坤,葛春风(天津大学精密仪器与光电子工程学院，天津300072)摘要：太赫兹(THz)波在电磁波频谱中占有很重要的地位，THz技术是国际科技界公认的一个非常重要的交叉前沿领域。
因此，提出了一种以循环移频环路(RFSL)为基础产生THz信号的微波光子学系统。
输入光信号经由RFSL多次移频后在高速光电探测器中拍频产生THz信号。
在RFSL中，基于射频(RF)控制的单边带(SSB)调制器是光信号移频的主要器件，每经过一次SSB调制器，光信号将产生一个与RF信号频率相等的移频间隔。
THz信号的倍频因子由光在环路中循环的圈数控制。
THz信号的频率随着倍频因子的增加而增加，频率大小为倍频因子与移频间隔的乘积。
实验上实现了THz 信号的倍频因子从1~25可调谐，测量了拍频获得的5~20GHz微波信号光谱和电谱，测量了20GHz 信号功率以及中心频率的稳定性，并最终实验获得了0.25THz的信号。
关键词：太赫兹信号；循环移频环路；单边带调制器；倍频因子中图分类号：TN249文献标志码：A DOI：10.3788/IRLA201948.S125001Generation of THz signal based on recirculating frequency-shifting loop with tunable frequency multiplication factorXie Taoran,Wang Zhaoying,Yuan Quan,Jiang Zhenkun,Ge Chunfeng(College of Precision Instrument and Opto-electronics Engineering,Tianjin University,Tianjin300072,China)Abstract:Terahertz(THz)waves occupy a very important position in the electromagnetic spectrum.THz technology is recognized as a major cross-cutting frontier in the international scientific and technology community.Photonic generation of THz signal using a recirculating frequency-shifting loop(RFSL)was proposed and experimentally demonstrated.The frequency of optical source was shifted by the RFSL and beats with each other in a high-speed photodetector to generate a THz signal.In the RFSL,the single sideband(SSB)modulator driven by a radio frequency(RF)signal was a key component for frequency-shifting.The frequency multiplication factor(FMF)of the THz signal was controlled by the lap number circulating in the loop.The frequency of the THz signal increased with the improvement of FMF and equals to the frequency multiplication factor multiplied by the frequency of RF signal.Experimentally, tunable signals from5GHz to20GHz were generated and the FMF was successfully tuned from1to25.The stability of the power and center frequency was detected when the frequency of the signal was 20GHz.0.25THz signal was finally generated by this system.Key words:THz signal;recirculating frequency-shifting loop;single-sideband modulator;frequency multiplication factor收稿日期：2018-12-01；修订日期：2019-01-14基金项目：国家自然科学基金(61275084，61377078)；天津市自然科学基金(18JCYBJC16800)作者简介：解陶然(1993-)，男，硕士生，主要从事高频微波信号产生方面的研究。
1.PCM原理抽样量化与编码:sampling,quantizing and coding话路:speech channel幅值: amplitude value抽样频率: sampling frequency抽样速率: sampling rate脉冲流: stream of pulses重复率: repetition rate编码过程: coding process模拟信号: analog signal传输质量: transmission quality数字通信: digital communication数字传输: digital transmission含噪声的环境: noisy environment传输路由: transmission path信噪比 :signal-to-noise ratio信号电平 :signal levels噪声功率: noise power地面系统: terrestrial system二进制传输: binary transmission反向操作: reverse operation8-位码序列: 8-digit sequence接受端: receiving terminal帧格式 :frame format同步字 :synchronization word实现这三项功能的方案 :the schemes for performing these three functions一串幅值: a series of amplitude values电话质量的话路 a speech channel of telephone quality一个8位二进制码的序列: a sequence of 8-binary digits理论上的最小抽样频率 :a minimum theoretical sampling frequency占据着300Hz到3.4kHz频率范围的话路: a voice channel occupying the range 300Hz to 3.4kHz 每个样值8-位码: 8-digits per sample value汽车点火系统的打火: the sparking of a car ignition system重复率为64kHz的脉冲流: the stream of the pulses with a repetition rate of 64kHz真实信号与噪声信号的关系: relationship of the true signal to the noise signal由卫星上接受到的信号 :the signal received from a satellite一条特定消息中的全部信息 :the complete informatian about a particular message被传信号的波形 :the shape of the transmitted signal由传输路由引入的衰减: the attenuation introduced by transmission path将抽样的幅值转换成一串脉冲的单元 :the unit that converts sampled amplitude value to a set of pulses涉及到第一路，第二路及其他各路的序列: a sequence relating to channel 1,2 and so on被称为同步字的独特码序列: a unique sequence of pulses called synchronization word地面系统 :terrestrial system脉冲的“有”或“无” : the presence or absence of the pulses高速的电子开关: a high-speed electronic switch时分多路复用器 :the time division multiplexer时分多路复用 :Time Division Multiplexer2.异步串行数据传输串行接口 serial interface显示终端 CRT terminal发送器与接收器 transmitter and receiver数据传输 data transmission数据流 data stream闲置状态 the idle state传号电平 mark level空号电位 space level起始位 start bit停止位 stop bitT秒的持续时间 duration of T seconds奇偶校检位 parity bit错误标志 error flag传输错误 transmission error下降沿 fallinf edge符号间的空格 intersymbol space接收机的定时 receiver timing本地时钟 local clock磁带 magnetic tape控制比特 control bit逻辑1电平 logical 1 level二进制数据 binary data明显的缺点 obvious disadvantage异步串行数据传输 asynchronous serial data transmission最为流行的串行接口 the most popular serial interface所传送的数据 the transmitted data发送器与接收器的时钟 the clocks at the transmitter and receiver电传机的时代 the era of teleprinter一个字符的点和划 the dots and dashs of a character符号间空格持续时间的三倍 three times the duration of intersymbol space被称为字符的比特组 the group of bits called characters由7或8个比特的信息组成的固定单元 the invariable units comprising 7 or 8 bits of information 由接收机本地产生的时钟 a clock generated locally by the receiver在字符后所收到的奇偶校检位 the received parity bit following the character起始位的下降沿 the falling edge of the start bit数据链路面向字符的特性 the character-oriented nature of the data link3.数据通信地下电缆 underground cable通信卫星 communication satellite微波设备 microwave facilities调制器与解调器 modulator and demodulator缓冲器 buffer定时信号 timing signals同步脉冲 synchronization pulses时隙 time slot移位寄存器 shift register传输媒体 transmission medium线形衰弱 linear attenuation信息安全 information security键盘 keyboard数据终端 data terminals某种类型的数据转换设备 some type of data conversion equipment视频显示终端 visual display terminal称为数据调制解调器的双向数据发送接收机 two-way data transmistter-receiver called a data modem 全双工的数据传输系统 full-duplex data trandmission system由数据处理器的运算速率所决定的速率 the rate determined by the operating speed of the data processor由接口部件来的定时信号 timing signals from the interface assembly磁心存储器 magnetic core memories线性衰减和时延特性 linear attenuation and delay characteristics传输损伤 transmission impairments语音中的冗余特性 the redundant nature of speech在数据发送器中的编码过程 coding process in the data transmitter二进制的不归零信号 binary nonreturn-to-zero signal4.互联网网络资源：network resource信息服务：information services远程终端：remote terminals互联的系统：interconnected systems命令：command电子邮件：electronic mail主机：host无线信道：wireless channels搜索工具：searching tools用户界面：user interface存取：access文本信息：textual messages协议：protocol超文本协议：hypertext protocol分布在全世界的计算机的巨大网络：gaint network of computers located all over the world主干系统：backbone system全国范围的网络：nationwild network电子会议：electronic conferences实时对话：live conversation最大的信息库the largest repository of the computers on the net网络设备资源：network facilities resources在网上的绝大多数计算机：the vast majority of the computer on the netUNIX操作系统：the UNIX operating system在因特网和你的PC机之间传送数据的方法：a way to move data between the internet and your PC 方便的搜索工具：the convenient searching tools联网的超文本协议：the network hypertext protocol5.光纤通信介绍光纤通信:optical fiber communications光源：light source波长：wavelength激光器：laser色散：dispersion传输介质：transmission medium多模光纤：multi-mode fiber长途干线：long-houl trunks单模光纤：singer-mode fiber带宽：bandwidth带宽用户：wideband subscriber纤维光学：fiber-optics商用技术：commercial technologe门限电流：threshod current光检测器：photodetector波分复用：wavelength multiplexing纤维光网络：fiber-optic network视频带宽：video bandwidth长途传输：long distance transmission中继距离：repeater spacing已装光纤的总长度：the total length of installed fiber长途通信系统：long-haul telecommunication system低衰减的石英纤维：the low-loss silica fiber衰减接近瑞利极限的光纤：fibers with losses approaching the Rayleigh limit室温下的门限电流：room temperature threshold currents较长波长区：the longer wavelength region用户接入工程：subscriber access project部件性能和可靠性的改进：improvements in component performance and reliability已安装的光纤系统的数据速率：data rates for installed fibre optic system每秒吉比特：gigabit per second range波分复用：wavelength multiplexing带宽用户环路系统：widebend subscriber loop system多纤连接器：multifibre connectors设计寿命：projected lifetime光源：light source单模光纤：single-mode fibre分布反馈式激光器：distributed-feedback laser信息容量：information capacity交换体系：switching hierarchy带宽业务：broadband services9.蜂窝式移动电话系统蜂窝式移动电话：cellular mobile telephone服务性能：services performance频谱：frequency spectrum频带：frequency band微处理器：microprocessor移动手机：mobile unit广播业务：broadcast servise天线：antenna子系统：subsystems移动用户：mobile subscriber服务能力：service capability利用率：utilization带宽：bandwidth单边带：single-sideband扩频：spread spectrum大规模集成电路：large scale integrated circuits蜂窝点：cellular site蜂窝交换机：cellular switch无线机架：radio cabinet呼叫处理：call processing频谱利用率：frequency spectrum utilization有限的指定频带：the limited assigend ferquency band 服务区：servise area复杂的特性和功能：complicated features and functions大规模集成电路技术：large-scale integraesd circuit technology试验性的蜂窝系统：developmental cellular system中央协调单元：central coordinating element蜂窝管理：cellular administration传统移动电话的运行限制：operational limitiation of conventional mobile telephone system 有限的服务能力：limitied service capability无线通信行业：radio communcation industry可用的无线电频谱：available radio frequency spectrum所分配的频带：the allocated frequency band移动收发信机：mobile transceiver技术上的可行性：techological feasibility严格的频谱限制：severe spectrum limitations调频广播业务：FM broadcasting services传播路径衰耗：propagration path loss多径衰耗：multipath fading电话公司地方局:telephone company zone offices10.全球移动通信系统个人通信 personal communcation通信标准 communcation standrads固定电话业务 fixed telephone services网络容量 network capability移动交换中心 mobile switching center国际漫游 international roaming宽带业务 broadband services接口转换 interface conversion频谱分配 frequency allocation模拟方式 analogue mode蜂窝通信原理 cellular communcation principe拥塞 jamming蜂窝裂变 cellular splitting基站 base station寄存器 register收费功能 billing function接入方法 access method突发脉冲传输方式 brusty transimission mode开销信息 overhead information切换算法 handover algorithms短消息服务 short message services技术规范 technical specificationtotal access communcation system 全接入的通信系统global mobile communcation system 全球移动通信系统time division multiple access 时分多址facsimile and short message services 传真和短消息服务fixed communcation networks 固定通信网络a more personalized system 更加个性化的系统the cost and quality of the link 链路的价格和质量market growth 市场的发展fixed telephone service 固定电话服务coxial cable 同轴电缆interface convision 接口转换cellular communcation priciple 蜂窝通信原则frequency reuse and cell splitting 频率复用和蜂窝裂变cochannel interference 共信道干扰theoretical spectual capability 理论上的频谱容量micro-cellular system 微蜂窝系统base station transceiver 基站收发信机subscriber register 用户寄存器burst transmission mode 突发脉冲传输模式overhead information 开销信息advanced handover algorithms 先进的切换算法facsimile and short message services 传真和短消息服务the GSM technique specications GSM技术规范说明一1 . 研究二进制的传输可见, 只要简单地去判别脉冲的“有”和“无”, 我们就获得了一条消息的全部信息。
电光调制• 基础EOM （Electrooptic Modulator ）将信息加载于激光的过程称之为调制，完成这一过程的装置称为调制器，激光称为载波，起控制作用的低频信息称为调制信号。
电光在激光器外的光路中进行调制，为外调制。
（内调制：加载调制信号在激光振荡过程中进行，调制信号改变激光器的震荡参数，从而改变激光输出。
激光谐振腔内放置元件。
）• 分类调幅、调频、调相、强度调制1. 振幅调制使载波的振幅随调制信号而变化，简称调幅。
produces an output signal that has twice the bandwidth of the original baseband signal.激光载波的电场强度为：0000()cos()E t A t ωφ=+ 调制信号()m m co a t A s t ω=A m 和m ω分别是调制信号的振幅和角频率。
调制之后，激光振幅0A 与调制信号成正比。
其调幅波的表达式为：000000000000()[1cos ]cos()()cos()cos[()cos[]]()22a a am m m t t m m t A A E t A m E t A t t ωωφωφωωφωωφ=+=-+++++++ 0/m a m A A =为调幅系数。
调幅波的频谱三个频率成分：第一项是载频分量，二、三项是因调制而产生的新分量，为边频分量。
PS:Single-sideband modulationArefinement of amplitude modulation uses transmitter power and bandwidth more efficiently.Single -sideband modulation avoids the bandwidth doubling and takes advantage of the fact that the entire original signal is encoded in either one of these sidebands.00()()cos( 2)()sin(2)()ssb s t s t t s t t f f quadrature amplitude modulation ππ=- 单边带调制最常用的是滤波法是分双边带信号形成和无用边带抑制两步完成的。
一种改进的光载波抑制产生光毫米波的方法陈罗湘;黄诚;陈林【摘要】为了延长光毫米波的传输距离,提出了一种改进的光载波抑制产生光毫米波的方法.在中心站采用马赫-曾德尔调制器将射频信号调制到光载波上产生光载波抑制调制光信号,再将产生光信号的2个边带分离,将2.5Gbit/s数据信号调制到其中1个边带上,再与未调信号耦合后产生光毫米波并通过光纤传送至基站.在基站中通过光电转换器产生电毫米波.从理论上分析了这种光毫米波的传输特性并通过实验验证了光毫米波在光纤中可以传输40km.仿真和实验结果表明,这种方式产生的光毫米波具有很好的抗色散能力,延长了传输距离.【期刊名称】《激光技术》【年(卷),期】2008(032)006【总页数】4页(P659-662)【关键词】光通信;光纤无线通信系统;光毫米波产生;光载波抑制【作者】陈罗湘;黄诚;陈林【作者单位】湘潭职业技术学院,信息工程系,湘潭,411102;湖南大学,计算机与通信学院,长沙,410082;湖南大学,计算机与通信学院,长沙,410082;湖南大学,计算机与通信学院,长沙,410082【正文语种】中文【中图分类】TN929.11引言光纤无线通信系统(radio over fiber,ROF)将成为未来超宽带无线接入的最理想的通信方式，人们已对ROF研究了多年[1-13]。
光毫米波产生方法是降低ROF系统代价的最关键的技术之一。
迄今为止，已提出的光毫米波的产生的方法有3种：直接强度调制、外部强度调制和远程外差技术[1-13]。
基于外部调制器的光毫米波产生方案具有较高的可靠性，可降低代价，因而最有可能成为ROF系统中产生光毫米波的首选技术[5]。
采用外部调制器产生光毫米波的方法有3种：单边带调制(single sideband,SSB)，双边带调制(double sideband,DSB)以及光载波抑制(optical carrier supression,OCS)。
Printed circuit board 印刷电路板Parallel plate capacitor 平板电容器Screwdriver 螺丝刀Dielectric 电介质，绝缘体Trimmer 微调电容器Perfect conductor 理想导体Equivalent resistance 等效电阻Magnetic field 磁场Diode 二极管Triode 三极管Series circuit 串联电路Parallel circuit 并联电路Tuning circuit 调谐电路Potential difference 电位差Open-circuit 开路Short-circuit 短路Level 电平Carrier 载波Impedance 阻抗Integrated 集成电路Faithfully 忠实的如实的Stripe 斑纹条纹Vacuum 真空Resonance 共振共鸣Passive component 无源器件Circuit board 电路板Fidelity 保真度Hybrid 混合的Semiconductor 半导体Potentiometer 电位计Component 成分分量Wafer 晶片Dissipation 消耗分散Operational amplifier 运算放大器High-gain 高增益的Feedback 反馈Differential amplifier 微分放大器Common-mode 共模Package 包装包裹Non-inverting input 同相输入Negative feedback 负反馈Filter 滤波器Inverting amplifier 反相放大器Pin 引脚引线8 pin dual-in-line 8引脚双列直插式Non-inverting 同相Inverting 反相Canonically 规范的Logic level 逻辑电平Flip-flop 触发器Non-transparent 不透明的Disambiguation 解疑Toggle flip-flop 反转触发器Latch 锁存器门闩Timing diagram 计时图时序图Inverter 变换器逆变器Transparent 透明的Qualitative 性质上的质的Quantitative 数量的Independent 自变量Electrical charge 电荷Entity 存在实体Duration 持续时间时长Girth 周围尺寸周长Cylinder 圆筒圆柱体Radius 半径Complex 复数的Tractable 易处理的易控制的Finite 有限的Converge 收敛聚合Mean-squared value 均方值Rms root mean square 均方根Ramp 斜坡Indefinitely 无限的Deterministic 确定的Probabilistic 概率性的Binary 二进制的M-ray signal M元信号Axis 轴Quantization 量子化Rounding off 舍入Aperiodic 非周期性的Periodicity 周期性的Ad infinitum 永远无限的Everlasting 永恒的Extract 抽取Hydraulic 水力的水压的Algorithm 算法Accessible 可连接的Linearity线性线性度Homogeneity 均匀性齐次性K fold k倍 k重Superposition 叠加重叠Decomposition 分解Carbon microphone 炭粒传声器碳晶话筒Granule 小粒微粒Instantaneous 瞬间的即时的Dynamic 动态的Prophetic 预言的先知的Lumped-parameter system 集总参数系统Distributed-parameter system 分布参数系统Partial differential equation 偏微分方程Acoustic 声学的LTI 线性时不变Algebraic 代数的Polynomial 多项式Unit impulse 单位脉冲Unit step 阶跃Subsystem 子系统Amplitude 振幅Sampling 取样Power series 幂级数Notation 表示法注释Unity magnitude 同一量级Unit 最小整数The region of convergence 收敛域Absolutely summable 绝对可和In the mean-square sense 在均方意义下Laurent series 洛朗级数Time shifting 时移性质Multiplication by an exponentialsequence 序列指数加权Differentiation of x（Z） z域微分Conjugation of a complex sequence 复序列的共轭Convolution of sequence 序列的卷积Initial-value theorem 初值定理The order of summation 求和的顺序Orthogonality 正交性Duality 二元性Modulo 以……为模Symmetry 对称性Impulse 脉冲Switchboard 交换台交换板Verbal 语言Copper 铜线Antenna 天线Teleprinter 电传打印机Data bank 数据库Propagate 传播Channel 通道Baseband 基带Modulation 调制Demodulation 解调反调制Sinusoid 正弦曲线Carrier 载波Modulator 调制器Demodulator解调器Bandpass 带通Frequency 频分多路转换Lowpass 低通Amplitude modulation 幅度调制Double-sideband modulation 双边带调制Single-sideband modulation 单边带调制Vestigial sideband modulation 残留边带调制Quadrature amplitude modulation 正交调幅Frequency modulation 调频Phase modulation 调相Detector 探测器Passband 通频带Automatic gain control 自动增益控制Superheterodyne receiver 超外差式收音机Matched filter 匹配滤波器Intersysmbol interference 符号间干扰码间干扰Synchronize 同时发生Line code 一行代码Unipolar 单极的Non-return-to-zero 不归零Quantize 量化数字转换Pulse-amplitude modulation 脉冲幅调制Pulse-width modulation 脉宽调制Pulse-position modulation 脉位调制Pulse-code modulation 脉冲码调制Differential PCM 差动式脉马灯Computer-aided instruction 计算机辅助教学Synth 合成Frame 帧Playback 回放Synthesizer 合成器Retention 保存Musical instrument digital interface 乐器数字接口Buzzword 流行词VCR vedio cassette recorder 录像机Mixer 混频器Full-motion vedio 视频素材全运动图像Resolution 分辨率Data compression 数据压缩Remotely 远程的Graphical 图解的生动的Facility 设备Peripheral 外围的不重要的Cluster 群簇集群Subnet 子网Connectivity 联通性Ethernet 以太网Token ring 令牌环网Collective 集体的共同的Distributed 分布的Asynchronous transfer mode 异步传输模式Frame relay 帧中继Configuration 配置Layout 布局Peer-to-peer network 对等网络Spreadsheet 电子表格Client、sever network 客户机、服务器网络Virtual 虚拟的Hybrid 混合的Collision 冲突Mainframe computer 主计算机Hub 集线器Expandablility 可扩充性Route 路由Broadcast 广播Clockwise 顺时针Anticlockwise 逆时针方向的Medium access control 媒体访问控制Bandwidth 带宽Twisted-pair cable 双绞线Coaxial cable 同轴电缆Optical fibre cable 光纤Shielded twisted-pair 屏蔽双绞线Wrapper 外壳Interference 干扰Cabling 布线Crossover cable 交叉线Straight-through cable 直通线Retain 保留Insulation 绝缘Electromagnetic 电磁干扰Crosstalk 串话干扰Susceptibility 敏感度Modify 修改更正Switch 交换机Gateway 网关Destined 指定的Switch table 交换表Routing table 路由表Propagate 传播Radio frequency 无线电频率Access point 接入点Functionality 功能性Accommodate 调节和解Alternative 替换物Protocol 协议Layer 层Well-defined 定义明确的Abstraction 抽象观念Unwieldy 笨重的不实用的Raw 原始的Nansecond 纳秒Simultaneously 同时的联立的Sequentially 相继的连续的Drown 淹没Buffer 缓冲区Flow regulation 流量调节Static 静态的Dynamic 动态的Bottleneck瓶颈Congestion 拥挤Jitter 抖动Addressing 寻址Heterogeneous 异种的异构的Nonexistent 不存在的Error-free 无错误的Delivery 递交交付Multiple 多重的多路的Chained 链接的Session 会话对话Synchronization 同步的Crash 崩溃Syntax 语法Semantics 语义学http hyper text transfer protocol 超文本传输协议world wide web 万维网。
