Glarkson UNIVERSITY

WALLACE H. COULTER SCHOOL OF ENGINEERING Technology Serving Humanity

MEMORANDUM

Subject: Progress Report 015- Chaotic LIDAR for Naval Applications: FY14 Q3 Progress Report (4/1/2014- 6/30/2014)

This document provides a progress report on the project "Chaotic LIDAR for Naval Applications' covering the period of 4/1/2014-6/30/2014.

^ol^oBo^H^ William D. Jemison, Professor and Chair, PO Box 5720, Clarkson University, Potsdam, NY 13699-5720

315-268-6509, Fax 315-268-7600, wjemison@clarkson.edu

FY14 Q3 Progress Report: Chaotic LIDAR for Naval Applications

This document contains a Progress Summary for FY14 Q3.

Progress Summary for FY14 Q3

The use of chaotic lidar for underwater system experiments progressed in this quarter. Experiments were set up for ranging using the chaotic system. Channel identification experiments continued, using a high speed receiver and adaptive signal processing.

The chaotic lidar project was presented at the Defense, Sensing, and Security conference in Baltimore, MD on 07 May, with a talk entitled "Chaotic Lidar for Underwater Channel Identification". The slides from this presentation are attached.

William D. Jemison, Professor and Chair, PO Box 5720, Clarkscn University, Potsdam, NY 13699-5720 315-268-6509, Fax 315-268-7600, wjemison@clarkson.edu

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Chaotic Lidar for Underwater Channel Identification

Luke Rumbaugh

Department of Electrical and Computer Engineering

Clarkson University, Potsdam, NY

SPIEDSS2014 Ocean Sensing and Monitoring

07 May 14

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Introduction

Channel Identification

Chaotic Lidar

Preliminary Results

Status and Future Work

Conclusion

Goal: Channel Identification

Context - Intensity-modulated optical systenn operating in water

(sensor, communications, ranging, imaging, mapping)

Problem statement - Measure variation in system response as a function of

frequency of intensity modulation - i.e., transfer function H(f) of the water

Channe Identification

System

Underwater Channel

H(f)

Underwater M(f) Channel

Frequency Response

H(f)=M(f)

p._^l3^rjk son UNIVERSITY Motivation: Hybrid Lidar-Radar m

Modulate optical carrier with radar signals

Modulation discrimination against scattered light - Scattered light decorrelates as

phase randomized

- Decorrelation increases exponentially with frequency

- Electrical discrimination improves performance

Continuous monitoring of modulation response - Decorrelation effect changes

with water conditions

- Would like to explore frequency spectrum to 1 GHz

■■11 LIDAR

Minimize Absoj'ption

Hybrid

AAAA

LIDAR-RADAR Technolog> Radar tranmtission/detection in m imdet-ymter environment

Backscattering from Volumetric Region

Direct Beam: Single Path Length

Received Backscatter: Distributed Path Lengths

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RF SOURCE

m^lHrJK son UNIVERSITY Internally Modulated Fiber Laser

Chaotic ytterbium-doped fiber laser

Uses ultralong cavity (>100 m) to encourage simultaneous, incoherent lasing of many chaotically competing resonant modes

"5 GHz peak at 1064 nm , (perlOdBBW)

b) Time Series

llarkson Fiber Amplifier Simulations

Mathworks.com: "Fiber Lasers and Amplifiers Design Toolbox''

Numerical modeling of fiber amplifiers using cust to solve rate equations

Both steady state and dynamic simulations

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■ Excitation Ratio

Pp 75mW @ 980nm

«-Pg 41 mW @ 1064nm

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Chaotic Lidar Transmitter .EM^:

Chaotic Fiber Laser

High Frequency

Fiber Amplifiers

High Power

Fiber Laser and Amplifier

Gain amplifier on board

Frequency Doubler

Green

Underwater Channel

H(f)

Channel Identification

Frequency Doubler u t» Focusing

optics

Nonlinear crystal

Output optics

Fiber output to free space

Receiver optics

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Translation Stage 20 cm 4 _—__, ► .80 cm

Correlation-based ranging:

• Wideband -> high resolution

• Processing gain -> sensitivity

• Unambiguous thumbtack peak

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Cross-correlation of Reference and Return Channels

Thumbtack peal at target location

0 20 Oefay (cm)

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Chaotic Lidar in Turbid Water (c=5.5)

• Avg. Error = 0.48 cm

A'

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Sub-crn accuracy at 5 attenuation lengths

10 20 30 40 50 60 70 Actual Target Distance Downrange (cm)

80

Channel Identification

Xi(t)

Chaotic lidar Transmitter

Electro-optic I Transnnit Path

X2(t)

Equalization Filter

Approach used in communications channel identification Leverages wideband chaotic signal as probe

Underwater Channel

y(t)

water

z (t) =X2 (t) *heg(t) *hfiit (t)

Adaptive Filter z(t)

e(t)=z(t)-y(t) 6(t)-^0

Underwater M(f) Channel 4^

Frequency Response

H(f)=M(f)f

10

Ilarkson UNIVERSITY System Proof of Concept m^.

Digitized chaotic signal used for channel Identification on known digital filter

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-a --1000

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Channel Identification Experimental Setup

EXPERIMENTAL SETUP

Fiber-Coupled Chaotic Lidar Transmitter

Reference Signal

532 nm

Il064nm

532nm t^

C/APC I

LNA PD

FC/APC

1064 nm

Xa(t)

Reflected Signal

Bias T LNA

X2(t)

^^^^^ Scatter from distributed particles

Water Tank

DC DMM

Highspeed Digitizer

Xa[n]

X2[n]

■Channel Identification Signal Processing Chain

A Backscatter Mf

L I „ asDUT Gain

Adaptive Filter

FC: Fiber coupler; L: Lens; PD: Photodiode; M: Mirror; LNA: Low-noise amplifier; PMT: Photomultiplier tube; RF: Radio frequency; DC: Direct current; DMM: Digital multimeter; DUT: Device under test 12

Channel Identification

15.-15

00 60 XI

WIDEBAND PROBE X: 37,35

I y:-3.112

O Raw Dala (filter + PMT)

—— Smoothed

»Qxi O Raw Data (PMT)

Smoothed Electrical LPF: 39 MHz passbard

O 2

PMT: 1 GHz bandwidth

1500 2fW3 0 SB MHz

IfXB MHz

ia» 2XB

WATER SIMULATION PREDICTIONS

■ Backscatter mth no target • Backscatter with gray target

Backscatter: Rotis off with frequ^ncy Target: Visible at high frequency

100 200 300 400 500 600 Frequency (MHz)

700 800 900 1000

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Status and Future Work .:sN^.

QfDesign high frequency, scalable power transmitter

□[Adaptive receiver to model channel

OTcharacterize electro-optic components

□Water measurements: Show frequency response of scatter, impact on performance

14

Conclusion

New tool for water measurements

- Motivation for channel identification

- Internally modulated fiber laser addresses technology challenges for transmitter

-Adaptive receiver provides usable model of channel

15