Session 2P1b Radio-Over-Fiber Communication System

Implementation of a Radio over Fiber System in a Geographically-distributed Optical Network Sodr e Arismar Cerqueira, Jr., D. C. Valente e Silva, M. A. Q. R. Fortes, L. F. da Silva, O. C. Branquinho, M. L. F. Abbade, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 GHz Radio over Fiber Transmission System Based on Integrative Cascade MZM Cheng Hong, Siyu Liu, Cheng Zhang, Zhangyuan Chen, Weiwei Hu, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single-mode Modulation Using Injection-locked Fabry-Perot Laser in Radio-over-Fiber System Cheng Zhang, Mingjin Li, Siyu Liu, Cheng Hong, Weiwei Hu, Zhangyuan Chen, . . . . . . . . . . . . . . . . . A Scheme of Photonic Notch Filter Using DGD Method for Radio-over-Fiber Communication Systems Hanhong Gao, Jinxuan Wu, Zhao Tu, Cheng Zhang, Dandan Wu, Weiwei Hu, Zhangyuan Chen, A Scheme of Microwave Photonic Filter Based on Hi-Bi Fiber Dandan Wu, Weiwei Hu, Zhangyuan Chen, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Trend of Designing Rotation Sensors Based on Highly Dispersive Resonating Structures Zinan Wang, Xiaomu Wu, Chao Peng, Rui Hui, Xuefeng Luo, Zhengbin Li, Anshi Xu, . . . . . . . . . .

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Implementation of a Radio over Fiber System in a Geographically-distributed Optical Network

S. Arismar Cerqueira, Jr.1 , D. C. Valente e Silva2 , M. A. Q. R. Fortes1 , L. F. da Silva2 , O. C. Branquinho2 , and M. L. F. Abbade2
2

Optics and Photonics Research Center, UNICAMP, Brazil Faculdade de Engenharia El etrica, Pontif cia Universidade Cat olica de Campinas, Brazil

Abstract The next generation of access networks is rushing the needs for the convergence
of wired and wireless services to oer end users greater choice, convenience and variety in an ecient way [1]. This scenario will require the simultaneous delivery of voice, data and video services with mobility feature to serve the xed and mobile users in a unied networking platform. In other words, new telecom systems require high-transmission bandwidths and reliable mobility. The Radio over Fiber (RoF) technology represent a key solution for satisfying these requirements, since it jointly takes advantage of the huge bandwidth oered by optical communications systems with the mobility and exibility provided by wireless systems. RoF systems consist of heterogeneous networks formed by wireless and optical links. Unlike traditional optical communications networks, in which a baseband signal in transmitted into the optical bers, in RoF systems one or multiple analogous carriers are transported into the bers. The transmission is performed by directly or externally modulating lasers by the analogous radio frequency signal. On the receiver side, the transmitted signal is recovered by using a photodiode. Compared to traditional optical systems, RoF technology provides the advantage of eliminating the gateways, since there is no need for analogous-digital or digital-analogous conversions. This simplies the system complexity and reduces the operational costs. RoF technology has been investigated by many Research Groups in the last years. However, the great majority of works published in literature are based on simulations and/or experiments carried out in laboratories. This work presents an implementation of a Radio over Fiber system based on IEEE 802.15.4 standard, in a geographically-distributed optical network called KyaTera [2]. Lasers were directly modulated by a RF signal at 2.4 GHz with Quadrature Phase Shift Keying (QPSK) modulation. This signal was launched into hundreds of kilometers from KyaTera Network under real conditions of temperature, pressure, humidity and wind. The optical signal was received by a fast photodiode, converted to electrical signal and then retransmitted by an antenna with gain G = 12 dBi. Finally the wireless signal was obtained by a receiver antenna. Simulations based on Split Step Fourier Method were carried out for predicting the system performance. The performance parameters evaluated in the experiments were the electrical Signal to Noise Radio (SNR) and Frame Error Rate (FER) of the transmitted RF signal. Experimental results show no performance degradation of the transmitted radio frequency signal.
REFERENCES

1. Jia, Z., J. Yu, G. Ellinas, and G.-K. Chang, Key enabling technologies for optical wireless networks optical millimeter wave generation wavelength reuse and architecture, Journal of Lightwave Technology, Vol. 25, 34523471, 2007. 2. www.kyatera.fapesp.br.

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60 GHz Radio over Fiber Transmission System Based on Integrative Cascade MZM
Cheng Hong, Siyu Liu, Cheng Zhang, Zhangyuan Chen, and Weiwei Hu State Key Laboratory on Advanced Optical Communication Systems & Networks Peking University, Beijing, China

Abstract We experimentally demonstrated a Radio over ber transmission system which

works in 60 GHz band with 2.5 Gbps bit Rate over 22 km SMF, using an integrative cascade MZM modulator. Introduction: Radio over ber technology is considered to be a potential solution to the broadband access networks. Making use of convergence of mobility of wireless and good transmission channel property of optical ber, Radio over ber technology can easy transmit several Gigabit per second. Here we experimentally demonstrated the transmission system for 2.5 Gps on 60 GHz microwave over 22 km SMF. Cascade MZM modulation method is a simple way to generate two coherence optical modes to beat in photodetector for producing microwave signal. Experimental Setup and Result:

1E-5 1E-6

DFB

MZM MZM

EDFA
1E-7 1E-8 1E-9 1E-10

22km SMF

30 GHz
BER

2. 5Gbps

Mix

PD 60GHz

BER

1E-11 1E-12

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

received opti -Pw (dBm)

Figure 1: Experiment setup.

Figure 2: Received BER.

The experimental setup is show as Fig. 1. An integrative cascade MZM as modulator. One MZM is used as microwave carrier modulator bias at null point; the other is used as data modulator and set at linear bias point. The transmission bit error rate is verse received optical power is show as Fig. 2. Conclusions: A primary demonstration of downlink Radio over system is realized by an integrative cascade MZM as modulator and coherent demodulation receiver. ACKNOWLEDGMENT This work is supported by The National High Technology Research and Development Program of China (863Program) under Grant 2006AA01Z261 and The National Natural Science Foundation of China (NSFC) under Grant 60736003.
REFERENCES

1. Koonen, T., Fiber to the home/ber to the premises: What, where, and when?, Proc. IEEE, Vol. 94, No. 5, 911934, May 2006.

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Single-mode Modulation Using Injection-locked Fabry-Perot Laser in Radio-over-Fiber System

Cheng Zhang, Mingjin Li, Siyu Liu, Cheng Hong, Weiwei Hu, and Zhangyuan Chen State Key Laboratory on Advanced Optical Communication Systems & Networks Peking University, Beijing, China

Abstract Radio-over-Fiber (RoF) system has been considered a promising technology for future broadband wireless communication. Recently, many schemes have been proposed to realize a low-cost and high-performance RoF system. The commonly used method to generate millimeter wave (MMW) in these systems is optical heterodyning technique which use two correlated optical modes to beat a high-quality MMW. And usually the data is uploaded to the MMW by just modulating these two modes. However, standard modulation of two correlated modes will suer from chromatic dispersion which results in a radio frequency (RF) fading and limits the transmission distance. Single-mode modulation is proposed to overcome this problem. But the former method using a Mach-Zehnder (MZ) interferometer lter is too complex to be practical. In this paper, we propose a new approach to realize single-mode modulation using injection-locked Fabry-Perot laser dioxide (FPLD). In the experiment setup, the DFB lasers output is coupled into an intensity modulator which is driven by the reference frequency at 15 GHz from a signal generator. The modulator output is sent to an optical notch lter to select the rst-order sidebands whose mode-spacing is 30 GHz. An EFDA and an attenuator are used to get the proper injection power and its output is connected with a 60 GHz mode-spacing FPLD through a three-port optical circulator (OC) for single-mode injection-locking. A polarization controller (PC) is used to control the input state of polarization to the FP laser diode. The intermediate frequency (IF) signal is uploaded by modulating the current of FPLD. Finally, the single locked mode and the other reected mode are transmitted for 44.4 km and sent to a 70 GHz photo detector (PD) for 30 GHz MMW generation. The electrical signal sidebands on both sides of 30 GHz carrier are measured for dierent IF. Another experiment using standard dual-mode modulation has also been done to for comparing data. Figure 1 compares the side power after 44.4 km SMF transmission for both single-mode modulation and dual-mode modulation. Dierent RF powers for single-mode modulation are also test in our experiment. Compared to dual-mode modulation, it can be found that the proposed single-mode modulation is immune to RF signal fading due to the chromatic dispersion.

Frequency (GHz)

Figure 1: Received electrical power for dierent modulation frequency after 44.4 km SMF transmission. ACKNOWLEDGMENT

This work is supported by The National Natural Science Foundation of China (NSFC) under Grant 60736003.

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269

A Scheme of Photonic Notch Filter Using DGD Method for Radio-over-Fiber Communication Systems
Hanhong Gao, Jinxuan Wu, Zhao Tu, Cheng Zhang, Dandan Wu, Weiwei Hu, and Zhangyuan Chen State Key Laboratory of Advanced Optical Communication Systems & Networks Peking University, Beijing, China

Abstract Microwave photonics has been a popular research eld. The photonic lters can
provide a large tunability and a high Q factor besides advantages such as low loss, light weight, immunity to electromagnetic interference and capability to overcome electronic bottleneck. Therefore, a number of photonic microwave lters have been reported in the literature. Several methods have been demonstrated using ber delay lines, most of which use several xed lengths of ber to achieve stepped time delay. It is recently demonstrated that non-uniformly spaced taps can implement a photonic microwave lter with an arbitrary band-pass response, which would have the same spectral characteristics as a photonic microwave delay-line lter with true negative or complex coecients. Another particular application of interest is the transversal microwave lter, which can be classied as two kinds: optically coherent and optically incoherent. Besides, a tunable ring resonator in polymeric wave-guides was exploited to implement an integrated photonic microwave band-pass lter operating at around 10 GHz. We propose a recongurable and continuously tunable photonic notch lter implementing a technique using a dierential group delay (DGD) element including a tunable laser source, a polarization beam splitter (PBS), an adjustable optical delay line, three polarization-preserving bers (PPF) and one polarization-preserving ber coupler. First, electro-optical modulator (EOM) modulates the laser output with RF signal. After passing PBS, the beam separates into two with orthogonal polarizations, which will travel separately along two PPF. In addition, one beam will experience delay through adjustable optical delay line. Therefore they will experience dierent time delay. They are combined using the polarization-preserving coupler and the electric signal is detected by photo detector (PD). Finally, a vector network analyzer is used to measure the characters of this microwave photonic lter. The time delay is set to about 100 ps, and a lter with free spectral range (FSR) approximately 10 GHz is realized. The notch rejection ratio is larger than 20 dB. By varying the time delay, dierent FSR will be accomplished. Whats more, the central frequency of laser source is adjusted deviating from the previous frequency from 0 to 10 GHz. In the meantime the lter varies from low-pass lter to band-pass lter and back to low-pass lter. This lter conguration has several advantages comparing with previous schemes. Firstly, adjustable optical delay line can be used to adjust FSR of the lter, making it continuously tunable. This delay line can achieve a wide range of FSR. Secondly, it is recongurable through the adjustment of the central frequency of the laser source. The lter frequency response can be changing from band-pass lter to low-pass lter. Lastly, this conguration can be used in varieties of radio-over-ber communication systems to achieve a better lter performance. ACKNOWLEDGMENT

This work is supported by the National Undergraduate Innovative Test Program and the National Natural Science Foundation of China (NSFC) under Grant No. 60736003.

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A Scheme of Microwave Photonic Filter Based on Hi-Bi Fiber

Dandan Wu, Weiwei Hu, and Zhangyuan Chen State Key Laboratory of Advanced Optical Communication Systems & Networks Peking University, Beijing, China

Abstract Over the past several decades Microwave photonic lter (MPFs) has attracted a
lot of interest due to the processing of radio-frequency (RF) signals in the optical domain, saving bulky OE and EO conversion parts, and with the advantages of wide bandwidth, immunity to electromagnetic interference, low loss, tunability and recongurability, therefore they are widely applied to phased-array beamforming, radar, mobile communications, and radio-over-ber (ROF) systems. The MPFs can be operated in incoherent or coherent regime. Incoherent lters are more stable against environmental conditions. Therefore, until now many kinds of incoherent MPFs have been reported in literatures. The conventional incoherent MPFs have been proposed using dierent optical delay lines or electrically summing congurations, then the intensity of the modulated light outputs from dierent taps are added. However, the former limited the free spectrum range (FSR) of the MPFs, and the later lost the advantages of optical domain signal processing. Recently, polarization synthesizing method has been reported to realize incoherent operation, which is based on dierential group delay (DGD) element with two ber delay lines. In this paper, we propose a novel structure of microwave photonic lter shown in Fig. 1. The radio frequency (RF) signal of a network analyzer drives an electrooptic modulator that modulates the output of a tunable laser source. The modulated optical signal transmits along a coupler and a three-port polarization beam splitter (PBS). One of the optical beams transmits clockwise along fast-axis of the Hi-Bi ber, and the other transmits anti-clockwise along slow-axis of the Hi-Bi ber. Because the Hi-Bi ber has a large refractive index dierence between its fast and slow axis, the time delay dierence will be induced. The two orthogonal optical signals, which are dierently delayed, are combined without interference and directed to the output of the coupler.

laser

EOM

PBS

Hi-Bi Fiber

Network Analyzer

PD

Figure 1: The experiment conguration of Microwave Photonic Notch Filter. Theoretical calculation show that the MPF structure can provide approximately 10 GHz FSR corresponding to the 100 ps time delay. The notch rejection ratio is larger than 20 dB. This MPF has several advantages comparing with previous schemes. First, its more stable and simpler due to using only one ber delay line, which can implement a wide range of FSR. Second, through the employment of temperature controller or PZT to adjust the length of the Hi-Bi ber, the MPF will be tunable and recongurable. The detailed experimental results will be discussed in the manuascript. ACKNOWLEDGMENT

This work is supported by The National Natural Science Foundation of China (NSFC) under Grant 60736003.

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The Trend of Designing Rotation Sensors Based on Highly Dispersive Resonating Structures
Zinan Wang, Xiaomu Wu, Chao Peng, Rui Hui, Xuefeng Luo, Zhengbin Li, and Anshi Xu State Key Laboratory on Advanced Optical Communication Systems & Networks School of Electronics Engineering and Computer Science, Peking University, 100871, China

Abstract Rotation sensors, which are also known as gyroscopes, are widely used for industrial
and military purpose. The basic idea of it is to detect the phase shift induced by the Sagnac eect in a closed loop [1]. Over the past few decades, gyroscope designing based on dierent structures have been intensively studied [111], and highly dispersive structures are mostly considered [4 11]. Its recognized that dispersion cannot inuence the magnitude of the Sagnac eect [2, 12]. But there are dierent manifestations in highly dispersive medium and resonator structure. For rotation sensors based on highly dispersive medium, as Doppler eect is proposed to be the intrinsic reason to enhance their sensitivity, they suit only situations when relative motion exists between the interferometer and the medium [10]. But its dierent for sensors based on highly dispersive resonating structures, such as coupled-resonator slow-light waveguide structures [9] and various photonic crystal geometries. These structures may possess huge Q-factor and they are extremely susceptible to the phase perturbation in the light path. The Sagnac eect will induce additional phase shift in the light path when such a structure is rotating, and then inuence its response. The total phase shift will be enlarged as a result. It shows that the highly dispersive resonating structure will improve the sensitivity in rotation sensing [10]. An example of highly dispersive resonating structures is the CRIT (coupled-resonator-induced transparency) structure, which has highly dispersive property with low absorption at its resonant frequency [13]. The gyroscope based on this CRIT structure is proved to be highly sensitive, and it has the potential to be made in a compact size [11]. The active CRIT structure, where the dispersion can be optically tailored, can further increase the performances of CRIT based gyroscopes [14]. Electrodynamics in rotating optical elements is quite useful in designing rotation sensors. This is widely used in modeling the Sagnac eect [8, 1518]. One way of using it is the application in the Finite-Dierence Time-Domain (FDTD) algorithm [18]. This FDTD method is a promising tool to accurately analyze, design and optimize rotation sensors.
REFERENCES

1. Post, E. J., Sagnac eect, Rev. Mod. Phys., Vol. 39, 475493, 1967. 2. Arditty, H. J. and H. C. Lefevre, Sagnac eect in ber gyroscopes, Opt. Lett., Vol. 6, 401403, 1981. 3. Bergh, R. A., H. C. Lefevre, and H. J. Shaw, An overview of ber-optic gyroscopes, J. Lightwave Technol., Vol. 2, 91107, 1984. 4. Lefevre, H. C., The Fiber-optic Gyroscope, Artech House Publishers, 1993. 5. Leonhardt, U. and P. Piwnitski, Ultrahigh sensitivity of slow-light gyroscope, Phys. Rev. A, Vol. 62, 055801, 2000. 6. Steinberg, B. Z., Rotating photonic crystals: A medium for compact optical gyroscopes, Phys. Rev. E, Vol. 71, 056621, 2005. 7. Matsko, B., A. A. Savchenkov, V. S. Ilchenko, and L. Maleki, Optical gyroscope with whispering gallery mode optical cavities, Opt. Commun., Vol. 233, 107112, 2004. 8. Steinberg, B. Z. and A. Boag, Splitting of microcavity degenerate modes in rotating photonic crystals the miniature optical gyroscopes, J. Opt. Soc. Am. B, Vol. 24, 142151, 2006. 9. Scheuer, J. and A. Yariv, Sagnac eect in coupled-resonator slow-light waveguide structures, Phys. Rev. Lett., Vol. 96, 053901, 2006. 10. Peng, C., Z. Li, and A. Xu, Rotation sensing based on a slow light resonating structure with high group dispersion, Appl. Opt., Vol. 19, 41254131, 2007. 11. Peng, C., Z. Li, and A. Xu, Optical gyroscope based on a coupled resonator with the alloptical analogous property of electromagnetically induced transparency, Appl. Opt., Vol. 15, 38643875, 2007.

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12. Leeb, W. R., G. Schiner, and E. Scheiterer, Optical ber gyroscopes: Sagnac or Fizeau eect, Appl. Opt., Vol. 18, 12931295, 1979. 13. Smith, D., H. Chang, K. A. Fuller, A. T. Rosenberger, and R. W. Boyd, Coupled-resonatorinduced transparency, Phys. Rev. A, Vol. 69, 063804, 2004. 14. Dumeige, Y., T. Nguy en, L. Ghi sa, S. Trebaol, and P. F eron, Measurement of the dispersion induced by a slow-light system based on coupled active-resonator-induced transparency, Phys. Rev. A, Vol. 78, 013818, 2008. 15. Shiozawa, T., Phenomenological and electron-theoretical study of the electrodynamics of rotating systems, Proc. IEEE, Vol. 61, 16941702, 1973. 16. Anderson, J. L. and J. W. Ryon, Electromagnetic radiation in accelerated systems, Phys. Rev., Vol. 181, 17651775, 1969. 17. Van Bladel, J. Relativity and Engineering, Springer, Berlin, 1984. 18. Peng, C., R. Hui, X. Luo, Z. Li, and A. Xu, Finite-dierence time-domain algorithm for modeling Sagnac eect in rotating optical elements, Appl. Opt., Vol. 8, 52775290, 2008.