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X. Tang 1 , Z. Ghassemlooy 1 , S. Rajbhandari 1 , W. O. Popoola 1 and C. G. Lee 2

Performance of the Coherent Optical Binary Polarization-Shift-Keying Heterodyne System In Free Space Optical Communications using a Lognormal Atmospheric Turbulence Model. X. Tang 1 , Z. Ghassemlooy 1 , S. Rajbhandari 1 , W. O. Popoola 1 and C. G. Lee 2

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X. Tang 1 , Z. Ghassemlooy 1 , S. Rajbhandari 1 , W. O. Popoola 1 and C. G. Lee 2

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  1. Performance of the Coherent Optical Binary Polarization-Shift-Keying Heterodyne System In Free Space Optical Communications using a Lognormal Atmospheric Turbulence Model X. Tang1, Z. Ghassemlooy1, S. Rajbhandari1, W. O. Popoola1 and C. G. Lee2 1: Optical Communications Research Group, NCRLab, Northumbria University, Newcastle upon Tyne, UK 2: Department of Electronic Engineering, Chosun University, S. Korea Email: fary.ghassemlooy@unn.ac.uk NCRLab MIC-CPE2010, JORDAN

  2. OUTLINE • I. FSO Introduction • Features • Applications • Challenges • ii. Lognormal Turbulence Model • III. System Description • Transmitter • Receiver • IV. Bit Error Probability Analysis • V. Results and Discussions • VI. Conclusion MIC-CPE2010, JORDAN NCRLab

  3. FSO INTRODUCTION • Benefits include • Ultra High Wireless Bandwidth • Most Secure Wireless Transmission • License free operation • Versatile Protocol • Safe to Use All • Major Cost Savings • Reliable Communication • High MTBF (Mean Time Between Failures) The world's first 10 Gig point-to-point deployment - Hollywood California by System Support Solutions, Inc. http://www.mrvfso.com/ NCRLab MIC-CPE2010, JORDAN

  4. FSO INTRODUCTION Typical Free-Space Optics deployments pictured above include point-to-point, multiple point-to-point, and mesh. http://www.mrvfso.com/ NCRLab MIC-CPE2010, JORDAN

  5. Need for speed ? Lasers cost less $ Mbps. http://www.mrvfso.com/ NCRLab MIC-CPE2010, JORDAN

  6. The above chart displays the approximate costs for full duplex 10BaseT, FastE and GigE links at distances from 10 meters to 6000 meters. You will observe that GigE is the real bargain with FSO technology (compared to FastE, 10x throughput for little more cost). http://www.mrvfso.com/ NCRLab MIC-CPE2010, JORDAN

  7. FSO APPLICATIONS FSO has been participated in over 400 link deployments including every continent in USA. http://www.mrvfso.com/ NCRLab MIC-CPE2010, JORDAN

  8. EXAMPLE 1 • Multi-campus University • LightPointe's optical wireless products http://www.freespaceoptics.org/freespaceoptics/topologies/default.cfm NCRLab MIC-CPE2010, JORDAN

  9. EXAMPLE 2 • Last-mile Connectivity NCRLab MIC-CPE2010, JORDAN

  10. EXAMPLES 3 & 4 • Clear Mesh Combines FSO Mesh for Metro Nets • ClearMesh Networks, a start-up based in Pasadena, California, unveiled a wireless optical mesh networking solution capable of delivering business-class services at 5-100 Mbps without requiring licensed spectrum. • Ship-to-shore FSO • Under a Phase II SBIR program sponsored by NAVSEA, LSA has developed a Free Space Optical Ship to Shore Communication System to address development of a Low Probability of Intercept/ Detection (LPI/LPD) communication capability for the littoral environment. NCRLab MIC-CPE2010, JORDAN

  11. FSO OTHER APPLICATIONS • Indoor FSO • MOBILE CARRIER APPLICATIONS • BTS Backhaul Connectivity • FSO Networks • ENTERPRISE APPLICATIONS • Enterprise Connectivity • Health Care • Engineering & Design • Voice & Data • Video • Telco Bypass • Security • Disaster Recovery NCRLab MIC-CPE2010, JORDAN

  12. FSO Challenges • FSO transmission systems loose some of their energy from signal scattering, absorption and scintillation. • Scattering: light signals are redirected as they pass through water particles. • Absorption: some optical energy is converted to heat as it strikes particles (such as smog). • Scintillation: when heated (such as from smokestacks) air cause a bending of the optical beam. NCRLab MIC-CPE2010, JORDAN

  13. The atmosphere behaves like prism of different sizes and refractive indices Phase and irradiance fluctuation ATMOSPHERIC TURBULENCE Result in deep signal fades that lasts for ~1-100 μs Eddies of different sizes and refractive indices • DEPENDS ON: • Altitude, Pressure, Wind speed • Temperature and relative beam size MIC-CPE2010, JORDAN NCRLab

  14. ATMOSPHERIC TURBULENCE MODEL The limitation of the log-normal model is defined by the Ryotov variance rage Irradiance PDF I: The received irradiance at the receiver Ino: The received irradiance without scintillation. σl: Log irradiance variance (turbulence strength indicator) MIC-CPE2010, JORDAN NCRLab

  15. SYSTEM DESCRIPTION - TRANSMITTER Vmatch applied to the 3 dB coupler is used for wavelength matching The PolSK modulator is based on the LiNbO3 device of which the operating wavelength is 1550 nm [1]. LD: laser diode PBS: polarizing beam splitter Va controls the amount of light launched in x and y polarizations x and y are the axes of polarization used to represent digital symbol ‘0’ and ‘1’, respectively. Vb controls the relative phase of the two polarizations [1] S. Benedetto, A. Djupsjobacka, B. Lagerstrom, R. Paoletti, P. Poggiolini, and G. Mijic, IEEE Photonics Technology Letters, vol. 6, pp. 949-951, August 1994. MIC-CPE2010, JORDAN NCRLab

  16. SYSTEM DESCRIPTION - RECEIVER LO: local oscillator; DC: directional coupler; BPF: bandpass filter; LPF: lowpass filter. Pr,lo : signal power ωr.lo: angular frequencies Фr,lo : phase noises m(t): the binary information MIC-CPE2010, JORDAN NCRLab

  17. THE STOKES PARAMETERS The 2PolSK modulation is based on the definition of the Stokes parameters S0, S1, S2 and S3 [1]: {ni(t)}i=0,1,2,3: the noise contribution which are independent of the received SOP and have the same variance. Note that the proposed 2PolSK refers only to the parameter S1. A digital symbol ‘0’ is assumed to have been received if S1 is above the threshold zero and ‘1’ otherwise. [1] E. Collett, "The stokes polarization parameters," in Polarized light: fundamentals and applications New York: Marcel Dekker, Inc., 1993, pp. 33-66. MIC-CPE2010, JORDAN NCRLab

  18. POLARIZATION-SHIFT-KEYING Why ? • Less sensitive to the amplitude fluctuation and is highly insensitive to the phase noise [1]; • A constant envelope modulation which is more resistant to the self-phase modulation (SPM) and cross-phase modulation (XPM) induced crosstalk [2]; • Can be well maintained over a long distance propagation in FSO [3]; • At the receiver, influence of the phase noise and the frequency offset can be eliminated thus ensuring reduced power penalty for a given BER performance. [1] M. Nazarathy and E. Simony, "Error probability performance of equi-energy combined transmission of differential phase, amplitude, and polarization," Journal of Lightwave Technology, vol. 25, pp. 249-260, January 2007. [2] M. N.-A.-S. Bhuiyan, M. Matsuura, H. N. Tan, and N. Kishi, "Polarization insensitive wavelength conversion for polarization shift keying signal based on four wave mixing in highly non-linear fiber " 14th OECC 2009, pp. 1-2, 13-17 July 2009. [3] X. Zhao, Y. Yao, Y. Sun, and C. Liu, "Circle polarization shift keying with direct detection for free-space optical communication " Optical Communications and Networking, , vol. 1, pp. 307-312, September 2009. MIC-CPE2010, JORDAN NCRLab

  19. BIT ERROR PROBABILITY ANALYSIS The conditional BER of the received irradiance: The unconditional probability Pe is obtained by averaging Pec over the log normal irradiance fluctuation statistics: This result is same as the BER expression of FSK. As regards the system sensitivity, PolSK and FSK techniques have complete equivalence [1]. [1] R. Calvani, R. Caponi, F. Delpiano, and G. Marone, "An experiment of optical heterodyne transmission with polarization modulation at 140 Mbit/s bitrate and 1550 nm wavelength " GLOBECOM '91, vol. 3, pp. 1587-1591, 2-5 December 1991 MIC-CPE2010, JORDAN NCRLab

  20. RESULTS AND DISCUSSION The simulated and calculated BERs performance against the SNR in an AWGN channel without turbulence Pec Both simulated and theoretical curves match very closely which confirms the validity of the simulation. MIC-CPE2010, JORDAN NCRLab

  21. RESULTS AND DISCUSSION The fading penalty against turbulence variances for a range of BERs Pe • For a fixed BER, the fading penalty increases with the turbulence variance • Fading penalty is higher for lower values of BER at the same turbulence level MIC-CPE2010, JORDAN NCRLab

  22. RESULTS AND DISCUSSION The BER performances of 2ASK, 2PolSK and 2PSK against the SNR in the AWGN channel with various turbulence variances Pe 7.1 dB 3 dB 3 dB MIC-CPE2010, JORDAN NCRLab

  23. CONCLUSIONS • The analytical conditional and unconditional error probabilities for a coherent optical 2PolSK heterodyne system adopted for an FSO communication link through the weak atmospheric turbulence channel was calculated and verified using computer simulations; • Results show the susceptibility of 2PolSK scheme when operated in a turbulence environment. A fading penalty of ~ 8.1 dB is observed at a turbulence variance of 0.3 at a BER of 10-9; increasing to ~ 17.2 dB at a turbulence variance of 0.9; • The comparative study of 2PolSK, 2ASK and 2PSK showed that PSK offers the highest immunity to the turbulence followed by 2PolSK. MIC-CPE2010, JORDAN NCRLab

  24. QUESTIONS AND ANSWER THANK YOU!!! MIC-CPE2010, JORDAN NCRLab

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