“Workshop on Disaster Relief Systems, Network
Resilience and Recovery”
(Istanbul, Turkey, 11 December 2012)
Research and Development Technologies
for Disaster Resistance Improvement
- Voice Communication System without Power Supply Hideaki Kimura
General Manager, NTT Corporation
kimura.hideaki@lab.ntt.co.jp
Istanbul, Turkey,11 December 2012
Presentation Outline
1. Background of research and development
2. Subjects in optical communication systems
3. Voice communication system without power supply
3.1. Technology for downstream signal
3.2. Technology for upstream signal
4. Conclusions and recommendations
Istanbul, Turkey ,11 December 2012
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Background of research and development
Optical access system based on PON
User 1
PC
Phone
RouterONU
Data Signal
Downstream Wavelength
Upstream Wavelength
Video Signal (Broadcast)
Video Wavelength
CO
User 2
PC
Phone
Router
ONU
Power
Splitter
Optical
Fiber
OLT
CO : Central Office
OLT : Optical Line Terminal
ONU : Optical Network Unit
TDM/TDMA : Time Division Multiplexing and
Time Division Multiple Access
TV
- 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
Istanbul, Turkey ,11 December 2012
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Subject in optical communication systems
Problem communication blackout during power failures
All communication services become unavailable
during power failure !!(Both internet access and telephone)
Conventional PSTN:
Telephone services remain available during power failures.
(thanks to electrical power supply from CO)
Istanbul, Turkey ,11 December 2012
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Subject in optical communication systems
Possible solutions and required functions for PON
- Optical Power Supply
User
Normal
Splitting loss
RouterONU
Router ONU
CO
PC
Phone
RouterONU
PC
Power Supply
Device
Optical
Power
Source
Power restriction for safety
Available power insufficient
CO
Router
Phone
WDM
Splitter
Data
Signal
(VoIP)
Power failure
OLT
(CW Light)
UPS : Uninterruptible Power Unit
VoIP : Voice over Internet Protocol
Normal
Phone
Data
Signal
Power failure
PC
User
WDM : Wavelength Division Multiplexing
CW : Continuous Wave
PC
Phone
- UPS Use
OLT
ONU
UPS
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 communication
services to continue during power failures
Istanbul, Turkey ,11 December 2012
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Voice communication system
without power supply
System configuration
User
Normal
WDM
Splitter
PC
Phone
Router ONU
Data Signal
Power failure
OLT
PC
Phone
Router ONU
CO
Voice Signal
EV-OLT
EV-T
EV-OLT : Emergency Voice - OLT
EV-T : Emergency Voice - Terminal
Telephone services with no power supply !!
Istanbul, Turkey ,11 December 2012
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Voice communication system
without power supply
Downstream system configuration
User
Power
Splitter
Power failure
CO
WDM
Splitter
Voice Signal
EV-T
EV-OLT
Super Low Power Consumption Detector
O/E
: Optical
/ Electrical
O/E : Optical
/ Electrical
E/O
: Electrical
E/O : Electrical
/ Optical / Optical
(SCM Demux / Signal Regeneration)
Audio
Output
Device
SCM Demux
Electrical BPFs
(all passive)
Local
Oscillators
O/E
Conversion
ex. PD
E/O
Conversion
ex. DML
SCM
( User Multiplexing )
SCM
Mux
(Electrical)
Signal
Generation
TDM Demux
DA Conversion
Analog Output
- 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
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Voice communication system
without power supply
Feasibility study of downstream system
*audible over 10 mVp-p
(dB)
20
15
PD
Dip S.W.
Diode
C
5mV / div
0.5ms / div
10
circuit diagram
L
1kHz SIN AM
ch1
ch2
ch3
ch4
ch5
ch6
ch7
ch8
5
0
100 150
-5
200 250 300 350
400 450 500
Frequency (kHz)
Frequency characteristic
Picture
Input optical power : -15dBm
Prototype Detector：
- ch number : 8ch (MAX : 8user multiplexing)
- each channel manually switched
We confirmed feasibility of user demultiplexing and voice signal
regeneration by transmitted optical signal power
Istanbul, Turkey ,11 December 2012
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Voice communication system
without power supply
Upstream system configuration
User
CO
Power WDM
Splitter Splitter
Power failure
EV-T
EV-OLT
Voice Signal
Random
Mixture
Optical Loopback
( User Demultiplexing )
(Voice Signal Generation)
CW Light
Voice - Intensity
Modulation
Blind Speech Separation
Voice Modulated
Loopback Light
Voice Pressure
Separated
Loopback
Each User’s
Light
Signal
Source Mixture
Signal
O/E
ADC
BSS
DSP
ADC : Analog-to-Digital Converter
DSP : Digital Signal Processing
- Optical loopback techniques is used for signal generation
But each user’s signals without timing control are randomly mixed …
- Blind Speech Separation (BSS) employed for user demultiplexing
Istanbul, Turkey ,11 December 2012
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Voice communication system
without power supply
Upstream system configuration
- Blind Speech Separation (BSS) Technique Histogram
Delay
Dt
Frequency
Sparse  rarely overlap
Mask width
800
Mask
400
Time frame
-200
0
200 (ms)
Phase difference
Mixing process model Sparseness of speech Phase difference clustering
- 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
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Voice communication system
without power supply
Upstream system configuration
- Utilizing Multi Wavelength Light Sources
and Phase Difference Caused by GVD Sensor corresponds to
each wavelength
( j+1 = lu1, j = lu2)
GVD : Group Velocity Dispersion
Acoustic system
Optical loopback access system
Available for calculation of phase difference
using received mixture signals at each wavelength
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Voice communication system
without power supply
Upstream system configuration
- Frequency up-conversion -
- Phase differences by GVD become very small
about 100 ms
About 3 orders of
magnitude smaller
about 100 ns
Optical loopback access system
Acoustic system
- Difficulty to detect small phase differences
Voice Signal
Required High
Performance ADCs
l1
l2
Available for
Conventional ADCs
Modulating
~ 100ns high frequency
Directly Application
(~ MHz order )
~ 100ns
carrier
Frequency Up-Conversion
- Applying BSS to up-conversion + voice frequency rage
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Voice communication system
without power supply
Upstream system configuration
- System design with BSS and frequency up-conversion -
LBLS : LoopBack Light Source
MOD : (optical) Modulator
DEM : Demodulator
- Demodulation after separation by BSS procedure
> Applying synchronous detection using DSP
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Voice communication system
without power supply
Feasibility study
- Simulation conditions -
C1 : 0 ns
User A
(Level Baseline)
CO
C3 : 20 ns
0 km
User C 4 km
C2 : 50 ns 10 km
User B
l1 : 1575 nm
Parameter
Value
Sampling Rate
10 MHz
Modulation Frequency fc
4 MHz
Mask Width
D
± 10 ns
(Attenuation : 0.24 dB / km)
l2 : 1300 nm
(Attenuation : 0.41 dB / km)
Simulation condition and parameters
- Ignore splitting loss and signal degradation of transmission
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Voice communication system
without power supply
Feasibility study
- Simulation results Phase difference histogram
C1
Histogram
1200
User A
800
User C
Mixed voices
Separated User A
(male)
Separated User B
(female)
Separated User C
(female)
SIR : Signal to Interference Ratio
SIR / SDR SDR : Signal to Distortion Ratio
C3
400
User B
C2
0
-100
-50
0
50
100
(ns)
Phase Difference
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
Reference : evaluation standards
in acoustic system
SIR Gain > 9 dB , SDR > 9 dB
(dB)
We confirmed separation by subjective assessment
Istanbul, Turkey ,11 December 2012
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Voice communication system
without power supply
Feasibility study
- Experimental conditions C1 : 0 ns
User A
C2 : 50 ns 10 km
User B
0 km
CO
l1 : 1575 nm
C1 : 0 ns
CO
User A 0 km
C3 : 20 ns 4 km
User C
l1 : 1575 nm
l2 : 1300 nm
: 1300 nm
(i) user A vs. user B
(ii) user A vs. user C
Experiment conditions
l2
- Experimental setup
Istanbul, Turkey ,11 December 2012
ASE : Amplified Spontaneous Emission
LS : Light Source
LN Mod : Lithium Niobate Modulator
FG : Function Generator
AOM : Acousto-Optic Modulator
SMF : Single Mode Fiber
PD-TIA : Photo Diode - Trans Impedance Amplifier
OSC : Oscilloscope
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Voice communication system
without power supply
Feasibility study
- Experimental results 800
C1
(i)
Histogram
600
User A
400
200
(ii)
User B
C2
0
-100
-50
0
50
100
Phase Difference (ns)
(i) user A vs. user B
Histogram
600
User C
C3
200
0
-100
-50
0
50
100
Phase Difference (ns)
(male)
Separated User B
(female)
Mixed voices
Separated User A
(male)
Separated User C
(female)
(i)
C1
400
Separated User A
SIR / SDR
800
User A
Mixed voices
input SIR
output SIR
SDR
User A
9.89
8.79
0.72
User B
-9.89
1.03
-3.99
input SIR
output SIR
SDR
User A
4.15
6.64
8.38
User C
-4.15
3.31
3.47
(ii)
We confirmed separation
by subjective assessment
(dB)
(ii) user A vs. user C
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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.
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