Time-resolved optical imaging through turbid media using a fast data acquisition system based on a gated CCD camera

Cosimo D’Andrea, Daniela Comelli, Antonio Pifferi, Alessandro Torricelli, Gianluca Valentini and Rinaldo Cubeddu

INFM-Dipartimento di Fisica and IFN-CNR, Politecnico di Milano Piazza Leonardo da Vinci

Milan, Italy

Rui Li

12-01-05

Outline

IntroductionMaterials and Methods

Results and Discussion

Optical Imaging

Tumour detection (e.g. breast tumours)

Noninvasive

Reconstruct reduced scattering (μ’s=μs(1 − g) g = <cosθ> )and absorption coefficients (μa)

Optical Tomography

Forward Model

Inverse Problem

μ’s μa

Clinical Trial

Development of a time-domain optical mammograph and first in vivo applicationsGr¨osenick D, Wabnitz H, Rinneberg H, Moesta K T and Schlag P M1999 Appl. Opt. 38 2927–43

Dual-wavelength time-resolved optical mammograph for clinical studies Cubeddu R, Giambattistelli E, Pifferi A, Taroni P and Torricelli A2001 Photon migration, optical coherence tomography, and microscopy Proc. SPIE vol 4431

Problem

Spatial resolution for clinical applications: 1mm

A huge data set required

Long measurement time

Outline

IntroductionMaterials and Methods

Results and Discussion

Experimental Set-up

Mode-locked Argon Laser

(CR-18, Coherent, CA)

λ:514nm, pulse width: 120ps, repetition rate: 80Mhz

Intensifier tube

(HRI, Kentech, UK)

gated from 200ps to 1ns,

Repetition rate up to 100MHz

CCD camera

(PCO, GmbH, Germany)

Dynamic range: 12 bit

Experimental Set-up

INT CCD

8×8 binning forms an effective pixel

Totally 160×128 effective pixels

Image size: 10cm

Each effective pixel: 0.8×0.8mm2

Experimental Set-up

HRI (High Rate Imager)

Time!

120 images, delayed by 50ps

Each image100ms

Totally less than 30s!

Random Walk Theory

2D 3D

μ’s μa

Random Walk Theory

In an Infinite homogeneous slab

Outline

IntroductionMaterials and Methods

Fast Gated Intensified CCDRandom Walk Theory

Results and Discussion

Homogeneous sample

μ’s=11cm-1 μa=0.05cm-1

Intralipid® (IL)

(Pharmacia, Italy)

and black India ink (Rotring, Germany) contai

ned in a

rectangular glass tank

(15×15×5 cm3)

Image area: 6cm

Measurement of different IL and ink concentration

Inhomogeneous Sample

The inclusions:

solid cylinders (1 cm↕ = 1 cmø) made of agar, IL and ink

Scattering inclusionFWHM

45mm

30mm

15mm

Time-gated Imaging

hom

incI

I

A- inclusion hardly detected!

Outline

IntroductionMaterials and Methods

Fast Gated Intensified CCDRandom Walk Theory

Results and DiscussionScattering inclusionsAbsorbing inclusions

Conlusions

12 bit CCD image 6cm diameter acquisition time of only 30s.

Experimental data were analyzed with theoretical function for a homogeneous medium or using a temporal gate technique.

Localize inclusions and discriminate between absorption or scattering abnormalities.

A diagnostic device for rapidly detecting inclusions.

Later Work

Localization and quantification of fluorescent inclusions embedded in a turbid mediumCosimo D’Andrea, Lorenzo Spinelli, Daniela Comelli, Gianluca Valentiniand Rinaldo CubedduPhys. Med. Biol. 50 (2005) 2313–2327

Critique

Spatial resolution1mm?

Reconstruction μ’s, μa, dimension?

Absorbing inclusion

Later work?

Scattering inclusionFWHM

45mm

30mm

15mm

Thank you!

107-Gb/s optical ETDM transmitter for 100G Ethernet transport

Peter J. Winzer, Greg Raybon, and Marcus DuelkBell Labs, Lucent Technologies

Presented at ECOC (European Conference and Exhibition on Optical Communication)

Presented by Mitul Patel

Outline

Introduction System Overview Transmitter setup Receiver setup Results Conclusions

Introduction

Increased use of Ethernet for data delivery in WAN (wide-area networks) topologies

10G Ethernet has gained much popularity 100G Ethernet is the next logical step (10x

increase typically)

Introduction, con’t

Historical development of Ethernet Speeds

Introduction, con’t

In this paper the first 107-Gb/s optical ETDM (electrical time-division multiplexed) transmitter is presented. This would be suitable for transport of 100G Ethernet

Why 107-Gb/s?– 100-Gb/s data rate + 7% error correction

overhead

System Overview

Both a transmitter and receiver had to be constructed to fully test the system

Transmitter Setup

Generate two identical 53.5 Gb/s PRBS (pseudo-random bit sequence) into 100-Gb/s 2:1 multiplexer

1 PRBS delayed by 1.6 ns

Transmitter, con’t

Eye diagrams before and after multiplexing

Transmitter, con’t

Multiplexer output sent to a MZM (Mach-Zehnder modulator) which modulated a 1550-nm laser.

Transmitter, con’t

MZM (biased at minimum transmission) used to generate a 107 Gb/s optical duobinary modulation.– Duobinary modulation – method to transmit R

bits/s using less than R/2 Hz of bandwidth– http://www.inphi-corp.com/products/whitepapers/DuobinaryModulationForOpticalSystems.pdf

Transmitter, con’t

Pictures show scope diagram and optical spectrum of 107-Gb/s signal.

Receiver Setup

Signal first passed through an optical attenuator and an Erbium-doped fiber amplifier (EDFM) to set the optical signal-to-noise ratio (OSNR)

Then passed through a 2-nm optical bandpass filter

Receiver, con’t

No 107-Gb/s electronic 1:2 demultiplexer was available so they used a 1:2 optical time-division demultiplexer (OTDM) implemented using another MZM (driven at 26.75 GHz, biased at minimum transmission).

Signal converted down to 53.5 Gb/s

Results

After the signal was received it was sent to a bit error rate tester (BERT) for analysis

Tested both a short (27 – 1) bit pattern and a larger (231 - 1) pattern

Both 53.5 Gb/s signals were measured separately by tuning the phase of the drive signal to the demuxing MZM

Results, con’t

Short patterns are almost error-free while the larger patterns level off around 10-6

They attributed this to the MZM’s non-ideal filter characteristics causing amplitude ripple

Results, con’t

However, using the 7% overhead for error correction allows for correcting a 10-3 BER down to 10-16.

Results, con’t

Finally the chromatic dispersion tolerance was measured. 107 Gb/s signal was sent over various lengths of single-mode fiber

Conclusion

Successfully able to demonstrate the first optical ETDM 107 Gb/s transmitter suitable for use in 100G Ethernet.