Experimental validation of an undersea free space laser network physical layer simulator David Rashkin*, Fraser Dalgleish**, Ionut Cardei*, Bing Ouyang**, Anni Vuorenkoski**, Mihaela Cardei* *Florida Atlantic University, Department of Computer and Electrical Engineering and Computer Science, Boca Raton, Florida **Ocean Visibility and Optics Lab, Harbor Branch Oceanographic Institute, Fort Pierce, Florida

Agenda Introduction Physical Layer Simulator Experimental Setup Results Discussion / Future Work Questions

Introduction Complete network simulator requires accurate physical layer model Gbps communication requires laser sources capable of sub-nanosecond pulses With these timing requirements, it is necessary to understand how the channel affects the pulses Use 95% CL BER as performance metric

Physical Layer Simulator Modulator Channel Model PMT Detector Model Demodulator

Modulator Inputs:  Sampling interval (1 ns)  Source laser peak power (160 mW)  Source laser variance (~ 3-5%)  Modulation scheme (PPM-16)  Pulse repetition rate (100Mhz, 200Mhz, 250Mhz, 500Mhz)  Bitstream (pseudorandom) Outputs:  1 dimensional array representing clean signal

Channel Model Inputs:  Beam attenuation coefficient (c)  Absorption coefficient (a)  Scattering phase function  Position and orientation of source and receivers in 3D space  Beam divergence  Receiver half-angle, radius and acceptance shape Outputs:  Two impulse response matrices, one for a receiver in forward direction and another for a receiver collecting the backscattered signal

Channel Model

PMT Detector Model Inputs:  1 dimensional array representing simulated signal in terms of optical power  Source laser wavelength  Detector quantum efficiency  Detector gain Outputs:  1 dimensional array representing noisy signal in terms of voltage

PMT Detector Model Shot noise limited Continuous Poisson random variable Per-sample noise drawn from multivariate Gaussian distribution

Demodulator Inputs:  1 dimensional array representing noisy signal  Pulse repetition rate (frequency)  Sampling interval  Modulation scheme Outputs:  Demodulated bitstream

Experimental Setup North Lab West Lab East Lab Movable Catwalk (Z) Linear Drive (X,Y) 3 Axis Deployment Carriage 12.5 x 7.5 x 2.5 m Turbidity controlled using ISO A1 Ultrafine Arizonta Test Dust Beam attenuation and absorption coefficients measured using Wet Labs AC9

Experimental Setup Omicron A nm pulsed laser,160mW peak power Agilent 81130A pulse generator Hamamatsu R9880U-210 PMT PXI 5154 high speed 8-bit digitizer (1 Gsps)

Results

Discussion / Future Work Off axis cases Full duplex / half duplex communication System design tool NLOS communication scenarios At-sea data

Acknowledgments ONR Joe Shirron, Metron Inc. Tom Giddings, Metron Inc. Benjamin Metzer, HBOI Walter Britton, HBOI Brian Ramos, HBOI Drew Krupski, HBOI

Questions? ?

Previous Work [1] Dalgleish, Fraser; Vuorenkoski, Anni; Ouyang, Bing; Caimi, Frank; Shirron, Joseph; Giddings,Thomas; Mazel, Charles, “Experimental and analytical channel impulse Response investigation for distributed laser serial imaging and non line of sight communications sensors in turbid coastal conditions”, In Proc. Ocean Optics XXI, Glasgow, UK. October [2] Vuorenkoski, A. K., Dalgleish, F. R., Metzger, B., Giddings, T. E. and Shirron, J. J. "Multi-path effects on optical communications links," Proc. ONR/NASA Ocean Optics XX. Sept 27th-Oct 1st Anchorage, AK. [3] Rashkin, D.; Cardei, I.; Cardei, M.; Dalgleish, F.; Giddings, T., "Detector noise model verification for undersea free space optical data links," Oceans, 2012, vol., no., pp.1,7, Oct [4] Ouyang, B. Dalgleish, F. R. Vuorenkoski, A.K., Britton, W.B., Ramos B. and Metzger, B., "Visualization for Multi- static Underwater LLS System using Image Based Rendering", IEEE Journal of Oceanic Engineering (accepted)