Hideaki Kimura General Manager, NTT Corporation [email protected]

Research and Development Technologies for Disaster Resistance Improvement

- Voice Communication System without Power Supply -

Hideaki KimuraGeneral Manager, NTT Corporation

[email protected]

Istanbul, Turkey,11 December 2012

“Workshop on Disaster Relief Systems, Network Resilience and Recovery”

(Istanbul, Turkey, 11 December 2012)

Presentation Outline

Istanbul, Turkey ,11 December 2012 2

1. Background of research and development 1. Background of research and development

2. Subjects in optical communication systems 2. Subjects in optical communication systems

3. Voice communication system without power supply 3. Voice communication system without power supply

3.2. Technology for upstream signal 3.2. Technology for upstream signal

4. Conclusions and recommendations 4. Conclusions and recommendations

3.1. Technology for downstream signal 3.1. Technology for downstream signal

Background of research and development


Optical access system based on PON

CO

ONU

User 2

TV

Router

PC

Phone

User 1

ONURouter

PC

Phone

OLT

Data SignalDownstream WavelengthUpstream WavelengthVideo Signal (Broadcast)Video Wavelength

- Fiber To The Home (FTTH) services - users number increasing rapidly- Passive Optical Networks (PONs) provide economical broadband services- PONs employ TDM/TDMA for multiple user access

FTTH will become LIFELINE services as PSTN PSTN : Public Switched Telephone Networks

CO : Central OfficeOLT : Optical Line TerminalONU : Optical Network UnitTDM/ TDMA : Time Division Multiplexing and

Time Division Multiple Access

PowerSplitter

OpticalFiber


Subject in optical communication systemsProblem communication blackout during power failures

Telephone services remain available during power failures.(thanks to electrical power supply from CO)

All communication services become unavailableduring power failure !!(Both internet access and telephone)

Conventional PSTN:

CO

User

Data SignalONURouter

PC

Phone

Normal

ONURouter

PC

Phone

Power failure

OLT


Possible solutions and required functions for PON

- Optical Power Supply

CO

WDMSplitter

OLT

OpticalPowerSource

User

DataSignal

(CW Light)

ONURouter

PC

Phone

Normal

ONURouterPC

Phone

Power failure

Power SupplyDevice

WDM : Wavelength Division MultiplexingCW : Continuous Wave

Available power insufficient

Power restriction for safety

Splitting loss

- UPS UseUser

DataSignal(VoIP)ONURouter

PC

Phone

Normal

ONU

RouterPC

Phone

Power failure

UPS

CO

OLT

UPS : Uninterruptible Power UnitVoIP : Voice over Internet Protocol

Available time restriction(storage battery)

Available about half an hour

Required of primary functions for systems equivalent to PSTN- No time restriction- Multiple users

Propose an optical access system that enables voice communicationservices to continue during power failures

Subject in optical communication systems

Voice communication systemwithout power supply


CO

User

WDMSplitter

Data SignalONU

Normal

Router

PC

Phone

OLT

EV-OLT

ONU

Power failure

Router

PC

Phone

EV-T

ONURouter

PC

Phone Voice Signal

EV-OLT : Emergency Voice - OLTEV-T : Emergency Voice - Terminal

Telephone services with no power supply !!

System configuration



Downstream system configuration

- Sub-Carrier Multiplexing (SCM) is used for user multiplexing - Proposed detector (all passive components)

driven with received optical signal power

We have confirmed downstream system feasibility

O/E : Optical / ElectricalE/O : Electrical / Optical

COPowerSplitter

WDMSplitter

EV-OLT

Power failure

EV-TVoice Signal

User

Super Low Power Consumption Detector(SCM Demux / Signal Regeneration)

AudioOutputDevice

O/EConversion

ex. PD

SCM DemuxElectrical BPFs

(all passive)

SCM( User Multiplexing )Local

Oscillators

SignalGeneration

TDM DemuxDA ConversionAnalog Output

SCMMux

(Electrical)

E/OConversion

ex. DML



Feasibility study of downstream system

L8C8D

IP S

.W.8

DIP

S.W

.1

L1C1

PD

*no bias

GeDiode

EarPhone

Prototype Detector：- ch number : 8ch (MAX : 8user multiplexing)- each channel manually switched

L

CPD Diode

Dip S.W.

Frequency characteristic

Input optical power : -15dBm

We confirmed feasibility of user demultiplexing and voice signalregeneration by transmitted optical signal power

0

5

10

15

20ch1ch2ch3ch4ch5ch6ch7ch8

(dB)

-5Frequency (kHz)

100 150 200 250 300 350 400 450 500

1kHz SIN AM

5mV / div

0.5ms / div

*audible over 10 mVp-p

circuit diagram

Picture



Upstream system configuration

COPowerSplitter

WDMSplitterPower failure

Voice Signal

User

EV-T EV-OLT

MixtureSignal

SeparatedEach User’s

Signal

O/E ADC

LoopbackLight

Source

BSSDSP

Blind Speech Separation( User Demultiplexing )

CW Light

Voice ModulatedLoopback Light

Voice Pressure

Voice - IntensityModulation

Optical Loopback(Voice Signal Generation)

RandomMixture

- Optical loopback techniques is used for signal generationBut each user’s signals without timing control are randomly mixed …

- Blind Speech Separation (BSS) employed for user demultiplexing

ADC : Analog-to-Digital ConverterDSP : Digital Signal Processing



Upstream system configuration- Blind Speech Separation (BSS) Technique -

Mixing process model

- Utilizing phase differences (delays) of each source (user) - Voice signals have sparseness property in the time-frequency domain

* Phase differences clustering* Designing binary mask to pick up slots from each cluster

Source kSource1

J

ljklJk

Sensor j

lj1

lJ1

DelayDt

Sparseness of speech

Time frame

Frequenc

y

Sparse rarely overlap

400

800

Phase difference clustering

Histogram

0-200 200(ms)Phase difference

Mask width

Mask



Upstream system configuration-Utilizing Multi Wavelength Light Sources

and Phase Difference Caused by GVD -

k+1

lk+1

tk+1

Source k Source k

j+1

ljk

lj+1k

from / toCO

lktk

Sensor j

lu2lu1

Dtk

Acoustic system Optical loopback access system

GVD : Group Velocity Dispersion

Available for calculation of phase differenceusing received mixture signals at each wavelength

Sensor corresponds toeach wavelength( j+1 = lu1, j = lu2)



Upstream system configuration- Frequency up-conversion -

~ 100ns~ 100ns

- Phase differences by GVD become very small

Acoustic system Optical loopback access system

about 100 ms about 100 nsAbout 3 orders ofmagnitude smaller

- Difficulty to detect small phase differences

Voice Signal

Required High Performance ADCs

Directly Application

Available forConventional ADCs

Frequency Up-Conversion

- Applying BSS to up-conversion + voice frequency rage

Modulatinghigh frequency(~ MHz order )

carrier

l1l2



Upstream system configuration- System design with BSS and frequency up-conversion -

ADC

LBLS1

LBLS2

MOD1

MOD2

O/E1DEM 1

DEM 2

DEM NO/E2

BSSDSP

High Frequency ( MHz order )

lk ≠ lk+1

l1

l2l1

l2

lk+1

User k+1

User klk

tk+1

LBLS : LoopBack Light SourceMOD : (optical) ModulatorDEM : Demodulator

- Demodulation after separation by BSS procedure> Applying synchronous detection using DSP



Feasibility study- Simulation conditions -

COUser A

(Level Baseline)

User C

User B

0 km4 km

10 km

: 1575 nm(Attenuation : 0.24 dB / km): 1300 nm

(Attenuation : 0.41 dB / km)

l1

l2

C1 : 0 ns

C3 : 20 ns

C2 : 50

Parameter Value

Sampling Rate 10 MHz

Modulation Frequency fc 4 MHz

Mask Width D ± 10 ns

Simulation condition and parameters

- Ignore splitting loss and signal degradation of transmission


Feasibility study- Simulation results -


Phase difference histogram

input SIR output SIR SDR

User A 2.93 6.51 4.85

User B -10.3 4.64 -2.05

User C -4.71 6.78 4.04

Mixed voices

Separated User A

Separated User B

Separated User C

We confirmed separation by subjective assessment

(dB)Reference : evaluation standards in acoustic system

SIR Gain > 9 dB , SDR > 9 dB

SIR / SDR SIR : Signal to Interference RatioSDR : Signal to Distortion Ratio

(male)

(female)

(female)

-100 -50 0 50 100(ns)Phase Difference

His

tog

ram User A

User B

User C

0

400

800

1200C1

C3

C2



Feasibility study- Experimental conditions -

ASE LS

ASE LS

LN Mod

4MHzSIN wave

OSC

User AVoice Signal

User B / CVoice Signal

1 x 2Coupler

1 x 2Coupler

10/4kmSMF

10/4kmSMF

FG

*Spectral slicing

WDMCoupler

FG

LN Mod

PD-TIA

PD-TIA

AOM

AOM

: 1575nml1

: 1300nm

Experiment conditions- Experimental setup

(i) user A vs. user B (ii) user A vs. user C

ASE : Amplified Spontaneous EmissionLS : Light SourceLN Mod : Lithium Niobate ModulatorFG : Function GeneratorAOM : Acousto-Optic ModulatorSMF : Single Mode Fiber

PD-TIA : Photo Diode - Trans Impedance AmplifierOSC : Oscilloscope

User ACO

User B10 km

0 kmC1 : 0 ns

C2 : 50 ns

: 1575 nm: 1300 nm

l1

CO

User C

0 km4 km

: 1575 nm: 1300 nm

l1l2

User AC1 : 0 ns

C3 : 20


Feasibility study- Experimental results -


(i) user A vs. user B

(ii) user A vs. user C

Mixed voices

Separated User A

Separated User B

SIR / SDR


User A 9.89 8.79 0.72

User B -9.89 1.03 -3.99

(i)

(ii)


User A 4.15 6.64 8.38

User C -4.15 3.31 3.47

(i)

(ii)

(dB)

(male)

Mixed voices

Separated User A

Separated User C

(female)

(male)

(female)

We confirmed separationby subjective assessment

200

0

400

600

800

-100 -50 0 50 100

User A

User B

C1

C2

(ns)Phase Difference

His

tog

ram

200

0

400

600

800

-100 -50 0 50 100

User A

User C

C1

C3

(ns)Phase Difference

His

tog

ram

Conclusions and recommendations


We introduced an optical access system that enables voice communication without power supply, which is an important problem of optical communication systems, during power failure in a user’s house. Proposed system employees low threshold Ge-diode radio technique and SCM for downstream signal and DSP techniques for upstream signal.

Now, optical communication system is one of life lines such as water, electric, gas and so on. Furthermore, we think that an importance of communication system will be increase, certainly although there is habitat segregation with a mobile system.

Documents

Hideaki Kimura General Manager, NTT Corporation [email protected]