KEYWORDS: LD, LED, FSO, VLC, IrDA, RoFSO.

OVERVIEW FOR OPTICAL WIRELESS COMMUNICATION

16 December 2017

Mitsuji Matsumoto

Waseda University, Japan mmatsumoto@waseda.jp

Introduction

Position of OWC(optical wireless system)

IRC(Infrared communication system)

VLC(Visible light communication system)

FSO(Free space optical wireless system)

Conclusion

2

Introduction

• Changes in the social environment, anywhere, anytime, high speed/high quality, easy and seamless, various service/application connections are demanded.

Wireless technology (Radio/Optical) is promising to solve these challenges. • Radio and optical have advantages and disadvantages, but here I introduce the area of OWC (optical Wireless Communication). • In the old wireless standard of the microwave relay system,

BER 0.01%/2,500km has been required and the value of the call loss rate is close to the (3%) of the whole communication network or mobile phone.

• Conventional optical wireless communication has been used as a complementary.

• Areas where best effort communication, or standards can be relaxed.

Characteristics of OWC

• The radiation beam of light travels straight at a - by wide angle (short distance ) or - by narrow angle (long distance) communication. • Wide range of application fields of light include - space(FSO), ground(FSO, VLC, IRC), underwater(VLC) • Further research on - transmitter/receiver optical components, - lightwave propagation technology etc. are important • For popularization, Standardization is also important.

4

Current trend for OWC in Communication Distance and Speed

UWB

10 Gbps

1 Gbps

100 Mbps

10 Mbps

1 Mbps

100 Kbps

1 km 100 m

WiMAX

10 m 10 km 1 m

Bluetooth

ZigBee

WLAN a/b/g

Optical fiber communication

Communication distance

Personal Area Comm.

Optical WLAN

IrDA

Long distance communication

Data rate

100 km

3Gbps Visible light communications Fraunhofer, HHI

1.28Tbps FSO by Sss’a, NICT, Waseda

150Mbps VLC- Li-Fi LAN Fudan

LII or )(exp

VLC- IrDA

5-10Gbps IR Fraunhofer

Near Field Comm.

FSO

ps

Mbps

Mbps

bps

ZigBee

IrDA

UWB

B

OpticalWLAN

3Gbps VcommunFraunhofe

1L

VLC-IrDA

5-10Gbps IRFraunhofer

Near FieldCommCommCC

Appearance of Infrared Data Communication Mobile terminal boom in the 1990's: Newton (PDA),Electronic notebook ,Personal Communicator: Start : Windows 95 OS machine

Information exchange and printout with the desktop PC (conventionally cable connection, FD exchange)

Desktop PC

Printer

Mobile PC

Focusing on infrared technology which has been widely used for remote control of home TV, stereo, air conditioner and so on for the past, it is applied for IR communication.

IrDA launched: In 1993 the consortium, De facto standardization organization Members: approx.100 (U.S.), 43(Japan)

User Scene

Showing pictures on the Big Screen.

Using presentation data from own PDA or cell phone.

8

IrDA Roadmap

10Mbps

Single Image Content

Single Music Content

Video / Music Album Contents

SIR

MIR FIR

VFIR Hyper Multimedia Instant Synchronization

UFIR GigaIR

1998 1995 2006 2009 1994

Giga-IR:2009 KDDI,Rohm,Panasonic, W.U., CEC. EG

UFIR:2006 SHARP,WU,NTT, Stanley, EG

HP IBM MS IrSimple 2005 SHARP NTTDocomoITX-EG,Waseda Univ

1Gbps 100Mbps 1Mbps 100kbps

Text base Contents

1998-2004 IrMC/IrFM 2005-2IrMC/IrSimple 2009- Giga-IR

short distance/1m/high speed

9

IrDA/VLC Protocol Stack

OSI 7

OSI 6

OSI 5

OSI 4

OSI 3

OSI 1

OSI 2

IrDA/VLC Physical Layer

IrLAMP

IrSimple

Multimedia Information Broadcast Information

TCP/IP UDP

Internet Session

Protocols OBEXTM

Other Transport Protocols

Other Session

Protocols

l d f

Personal Area Network Applications

upper layers

TinyTP

Inverted 4PPM Manchester Encoding

IR Transmit Circuit

IR receive circuit

Mod.

Dem

LED

UART

Universal Asynchronous Receiver and Transmitter

Infrared circuit diagram

1 frame:10 bits

115.2 kb/s

0 1 0

00 01 10 11

Chip

9.6 kbps - 1.152Mbps

4Mbps(

125

Data bit Pair (DBP)

4PPM Data Symbol(DD)

00 1000 01 0100 10 0010 11 0001

T=500 ns

12

Download Data Activity Time

DDAT(A)

Turn Around Time TAT(A)

Turn Around Time TAT(B)

Data Acknowledge DA(B)

Station A Station B

Download Data Activity Time

DDAT(A)

Dead Time

High efficiency technical challenges

Processing Bitmap info

Decoding Bitmap info

Comparison between early stage IrDA and IrSimple systems

Early stage system in case of 4Mbps

IrSimple system In case of 4Mbps

Approx. 6 sec

Approx. 1 sec 500KB photo transfer

13

Connectivity utilization model

• Conscious connection – Point-to-Point Usage

• Personal information transfer (vcard, vcal, etc…) • User initiated synchronization • Financial messaging • Walk-up printing

• Unconscious connection • Voice • Network Synchronization • Shared access device connectivity

–Ericsson, Intel, IBM, Nokia, Toshiba (1800 companies)

Market conditions – maturity of IrDA and Bluetooth

Hype

Maturity

IrDA Bluetooth

1995

1997

Mid-1998

2001 Mid-2003

Peak of Inflated Expectations - IR

Slope of Enlightenment

Technology Trigger - IR

Plateau of Productivity

Peak of Inflated Expectations - BT

Trough of Disillusionment

Source: Gartner Group / IrDA

‘Intersection of Reality’

10

100

1000

115kbps:SIR

Transfer Speed(Mbps)

GigaIR

UFIR,IrBurst (Diffusion LD)

LD

16Mbps:VFIR

4Mbps:FIR

Diffusion LD

1

VLC

Product technology roadmap IrDA)

Audio

White LED

16

Development of Eye Safe Laser Diode

•the spot size:1000 times •measured beam diameter:4mm •100Mbps/1m

Same Approach is possible for miniature IrDA Unit

Source Size of >2mm will be possible with optimized lens

Operating Current is < 1/3 compared with LED

Modulation speed is >100MHz

100Mbps IrDA

Challenges of IR communication

• Speeding up of Light Emitting Element (LD, LED) • Wide range Connectivity (Speed, Distance, Radiation angle) • FDX(Full duplex transmission) and Throughput • High Speed Transmission protocol

(Short Confirmation, Turn Around Time) • Interoperability (Standardization) • Miniaturization (small size) • Killer Application

19

Visible Light Communication (VLC)

• Visible Light communication is a wireless communication technology that uses light that is visible to humans

• Main features of VLC (1) LED lights will be used everywhere (2) Infrastructure is necessary for location services (3) Easy identification of places or things (4) There is no regulation for visible light communication so far

20

Blue LED chip

PN

White light

PN junction

Transparent epoxy resin

Emission

Anode+ Cathode-

LED (semiconductor element emitting)

Visible light wavelength

Definition : Electromagnetic waves of wavelength 380-780 nm visible to human eyes. When it comes into the human eye, it is recognized in the brain as color, each color has its own wavelength.

Visible Light Communication (VLC)

Light emitting method of white LED

Blue LED+ Yellow phosphor Complementary color

White with one-chip LED with blue/green color mixture

White by combination of red / green / blue LED

10

White light emission White light emission White light emission

Blue LED Ye

llow

ph

osph

or

BG mix. R G B

Origin of visible light wireless communication

A.G.Bell’s Photohone (1880)

Visible Light Transmitter Visible Light Receiver

23

Voice Input

Sun Light

Voice Input

Voice Output

Sun Light

Lens

Lens

glass

Reflector

Parabolic mirror

Selenium

VLC characteristics Emits electromagnetic waves focusing on single wavelength with specific photons. Ease of directivity control Luminous efficiency 30 - 100 (lm / W) Regular light spectrum Fast response to current (short-time strobe lighting)

Communication possible Light amplitude / intensity (light and dark) Optical wavelength (color) Optical phase (shape)

Optical accesspoint

A modulation scheme effective for illumination optical communication

Basic requirement • Maximize lighting characteristics • Secure reception average power that can ensure desired SNR (BER) • It is less susceptible to disturbance illumination light (fluorescent noise etc.) • Even if any kind of data is modulated, a mechanism that always lights once -------- 4 PPM (Pulse Position Modulation) [Modulation method]

slot Turn On

off

slot

25

on

off

Light receiving element for illumination optical communication

Basic requirement • High sensitivity (receiving ability of weak optical signal) • High-speed response (increase in code transmission speed) • Low noise (SNR degradation of optical signal is small) • High quantum efficiency (large number of carriers, increase in

signal quantity) Main light receiving element: • Single PD/APD (APD: about 3-5 dB higher sensitivity than PD) • Two-dimensional image sensor (array of PD / APD)

Comparison of light receiving methods of single and two-dimensional elements

Sa

1 1

SG2(noise source)

Ss

20

• Point light reception is strong against the influence of background light noise and communication at long distance is possible;

• Since the multiple signals are processed simultaneously, the load is greatly high Fast communication is difficult;

• Flicker occurs at low speed (frame rate is several tens of kHz).

Single PD light receiving surface Ss

SG2(noise source)

Spatial light interference range

Image sensor receiving surface Sa

• Easy structure, high speed operation by element;

• It is weak against influence of background light noise due to surface light reception, making it difficult to communicate over long distances.

Optical Wireless LAN (Omnidirectional system structure)

Access the Internet source) Receiving PLC modem

LED lighting fixture

Down VLC Up IR

Dongle Transmitting PLC modem

PC or Internet

Wi-Fi and Li-Fi

(a) Wi-Fi

Radio wave

Wireless LAN card

Access-point

Light wave

Optical Accesspoint (LED lighting) Ethernet

Optical wireless dongle (b) Li-Fi

Client

Ethernet

Client

Omnidirectional

Challenges Master unit Master unit

Shared space Shared space T1 T1 T2 T2

VLC VLC VLC VLC

Principle of spatial light CSMA / CD (CA):

IEEE 802.3 CSMA/CD (CA): carrier sense multiple access with collision detection/avoidance

(a) no collision (b) collision

Collision Detect

Under water communication

Photos provided by Toyo Electric.

Comparison of underwater data radio propagation method Radio wave sound waves light waves

Distance Long range transmission possible with low frequency

Compared to light and radio waves, attenuation is small and it can be transmitted far away

Damping due to absorption / scattering / light shielding, short distance (average about 15 - 100 m)

speed There is a speed limit. Faster than in air (average about 1500 m / s)

Speed depends on water pressure and water temperature

Sound velocity minimum around 1000 m (approx. 1470 m / s)

capacity The amount of information that can be transmitted with as low frequency as possible is small

Large capacity (easy to control due to visibility)

For seawater and freshwater, fresh water has longer propagation distance at any frequency

Frequency Characteristic in under sea

500 1500 2000 0.0

0.5

1.0 Bay area 450nm

550nm 650nm

1000 Distances (cm)

2000 4000 6000 8000 10000 0.0

0

0.5

1.0

Inte

nsiti

es (a

.u.)

Distilled Water

Abso

rptio

n at

tenu

atio

n

Electro magnetic MW

IR

UV

X-ray VLC

Underwater sonic

Frequency (Hz)

Spectral decay of transmission distance by extinction coefficient

Attenuation of electromagnetic waves (Radio wave/Light) and sound waves in seawater

F/Fo e-cL C(Extinction co.) a(Absorption co.) b(Scattering co.) Fo(Incident parallel light flux)

Ocean environment VLC system (Submarine exploration) by JAMSTEC

Data uplink by VLC Data uplink by VLC

VLC area

Submarine station Max Comm. Distance:100m Speed 1Mbps TWA

Marine environment visible light wireless communication system

Wav

elen

gth

sele

ctiv

e

adap

tatio

n

Data Data

Wavelength selective optical filter

Receiver Transmitter

Underwater Light

PD

Seawater

Lighting & Carrier by White light

1000 times/6500m

Adaptive measures for marine environment

"Shinkai 6500" is a submersible survey ship capable of dive to 6,500 m in depth (1989) -JAMSTEC

1200 times/ 6500m/ 3 person

doc.: IEEE 802.11-17/0962r2

Specialty Areas (Low Volumes)

Mass Market (Very High Volumes)

Very Low Data rates (simple protocols )

The IEEE 802 OWC standards Very High Data rates (complex protocols )

Optical Camera Communications in

802.15.7m - Limited MAC relevance

eas

(complex pro

802.15.13 - MAC based on

802.15

802.15.7- 2011

Mass Marke

ols )

Potential LC for 802.11 - MAC based on 802.11

Submission Slide 36 Nikola Serafimovski (pureLiFi)

Reference:An overview on high speed optical wireless/light communications

OWC/LC WiFi area

IEEE 802.11 can bring high-speed LC to the mass market faster and in a more comprehensive manner other SDO

ITU-T Study Group G.vlc • Based on G.hn – Home Networking standard • Customer Premises Equipment may use G.hn 802.15.7r1 • Originally based on 802.15.4 - Not designed for networking, e.g., No 48 bit MAC address, different security,… 802.15.13 • Based on 802.15.7r1 with focus on Muli- Gigabit/s Optical Wireless Communications suitable for speciality wireless networks Problem Neither effort has the comprehensive ecosystem of partners required for mass market adoption of LC. Proposed – 802.11 has unique ecosystem • Chipset vendors, Network Infrastructure, Device Integrators, • End Customer and Operators

doc.: IEEE 802.11-17/0962r2

LC can address a number of different use-cases

July 2017

This is just an illustration of the possible use-cases. Additional use-cases such as in-home, virtual reality and more can also be considered.

Submission Slide 38 Nikola Serafimovski (pureLiFi)

Depending on the deployment scenario and application, the FSO communication system is suitable for terrestrial, ocean and space based communication.

For space-based communication,

Deep space communication Inter-satellite communication Satellite to Ground communication Manned spacecraft ]

In the case of terrestrial communication,

Metro network extension Last mile access Enterprise connectivity Remote located settlements Fiber backup Temporary line in case of disaster, etc.

FSO Application scenarios

FSO

FTTH

39 999993999

Mountainous terrain

Backhaul (~5 km)

RoFSO transceiver remote base station Metro network

extension

Remote located settlements

RoFSO link Optical fiber link RF based links RoFSO transceiver

No fiber connectivity

Internet

1550nm 1550nm

Transmitting Terminal

Receiving Terminal

Opt. Beam

Optical fiber Optical fiber

Atmospheric turbulence

How to realize Ultra High Speed and Reliable Optical Link through the atmosphere, based on the compatibility with existing fiber infrastructure using 1550 nm wavelength

What are the challenges of FSO?

40

Direct coupling high-speed FSO system

• No O/E & E/O conversion • Uses 1550nm wavelength • Compatibility with existing fiber infrastructure. • Protocol and data rate independent. Seamless connection of space

and optical fiber. • broad bandwidth (InGaAs) and no power limitations • Tracking control mechanism

Provide high speed physical transmission path and services equivalent to optical fiber.

By Direct coupling between optical fiber and free-space

10μm

1550nm

Transmitting Module

Receiving Module

Opt. Beam

Optical fiber Optical fiber

Atmospheric Turbulence

41

Influence of atmosphere on FSO

Because transmission environment of FSO is the atmosphere, so there are many influences on the system performance, including attenuation due to rain, fog, snow and especially turbulence due to the variation of temperature and pressure, etc.

Among them, effects of fog and turbulence are severe. However, in the case of fog, we can overcome by some way for example increase transmission power or pre-amplifier gain.

For many cases of practical problem, optical turbulence is the limiting factor in reliable free-space optical communication link performance. In particular, the problem in guiding the light beam to the SMF is that the fluctuation of the atmospheric fluctuation : Scintillation

42

Beam wander

Scintillation (intensity fluctuations)

Time

Transmit power Received power

Combined effect T

T

T

T

Problem when guiding the light beam to the SMF

In general, atmospheric fluctuations are refracted and change the direction of travel when passing through the boundary of air masses with slightly different densities. (ex. heat haze or blinking of stars). Beam wander: a phenomenon when the direction of optical beam changes when relatively macroscopic air mass is passed. Daily, Seasonal variation. Scintillation or intensity fluctuation : a phenomenon that the received power fluctuates at short cycles (1-10ms) when the light beam propagates in the atmosphere. (the particle diameter is smaller than the beam diameter and it becomes active when the temperature is high and the humidity is high) 43

Scintillation

Turbulent flow cellTurbulent flow ce ell

Distortion of wavefront

Detection system

filter

After 1km transmission, 100 mm radius lens, λ=800nm 0ms 33ms 66ms

Ex:Change of beam pattern by scintillation

Time (sec) R

elat

ive

pow

er

rece

ived

0 0.5 1.0 0

0.5

1.0

Andrews Larry.C., Phillips R.L., Cynthia Y. Hopen; “Laser Beam Scintillation With Applications”

44

Po1 Po2

PD

500μm

Conventional system

Ip1= Ip2

To mitigate atmospheric effects Tracking system is required

SMF

10μm

Direct coupling FSO system

FSO antenna

Transmitter Receiver wide beam (5m/1km)

Beam divergence, θ

FSO antenna

Transmitter Receiver narrow beam (10cm/1 km)

PD: Photodiode (Si, InGaAs; SMF: Single Mode Fiber 45

0 1000 2000 3000

1

2

3

Inten

sity (

V)

0 1000 2000 30000

1

2

3

Inten

sity (

V)

0 0.5 1 1.5 2 2.5 3

x 104

0.5

1

1.5

2

2.5

3

Time (msec)

Inten

sity (

V)

Time: 6:04 am, Temp: 28.4 0 C

Time: 13:04 pm, Temp: 38.8 0 C

Time: 20:04 pm, Temp: 32.2 0 C

Intensity change at different times of fine weather

Cn2 in in summer and winter

Evaluation of atmospheric turbulence

46

Strong

Weak

Moderate

Cn2 is refractive index structure constant, used to indicate atmospheric turbulence strength

σI2 : scintillation index (Normalized intensity variance)

Weak : 10-15≤ Cn2 <10-14

moderate: 10-14 ≤ Cn2 ≤ 5 10-14

strong: 5 10-14 ≤ Cn2

2

2

2

I

III

6/116/722 23.1 LkCnI

(Rytov variance)

Strong: at noon of fine day Weak: sunrise, sunset, rainy days

))4/(206.11)/2(23.1/( 6/726/116/72

2

2 lDLI

IICn

10Gbps Transmission

10Gbps BERT 2006 January 26-27

1.0E-12

1.0E-11

1.0E-10

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

18:00 20:00 22:00 0:00 2:00 4:00 6:00

Time

BER

Bit Error Rate Sync Loss Sec. Power

Rec.

Pow

er [d

Bm]

0

-10

-20

-30

-40

47

Four channel 1550 nm data link operating at 2.5 Gbps WDM

2.5 Gbps X 4 channels with output power 100mW/wavelength Stable communication was achieved with no fluctuation or interference between wavelengths (an output power of 100 mW per wavelength )

WDM received signal spectrum BER and received power characteristics

18:00 21:00 24:00 03:0010

-12

10-10

10-8

10-6

10-4

10-2

100

Time

-60

-50

-40

-30

-20

-10

0

1550.1 nm BER1550.9 nm BERReceived power

Date: 23 ~ 24 November 2005

Rec

eive

d P

ower

(dB

m)

Log(

BE

R)

(Error free)

WDM Experiment setup and results

1549.3 nm

1550.1 nm

1550.9 nm

1551.7 nm

ITU Grid 100GHz spacing

48

Digital TV broadcasting BER and received optical power characteristics.

RoFSO Movie image transmission result

Digital TV broadcasting signal transmission

0:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:0010-10

10-8

10-6

10-4

10-2

100

BER

11 December 2008

Time

BER Layer ABER Layer BReceived power (dBm)

0:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00-25

-20

-15

-10

-5

0

Rec

eive

d po

wer

(dB

m)Error correction limit

A-Layer 1seg video

B-Layer 12-segment video

49

8- /32- DFBs

EDFA1 (Booster)

AWG

. . .

PCs

40 Gbps PRBS (231-1)

IM

data recovery

OC1 Terminal 1

OTBF

EDFA2

EDFA3 PD OA OA

OC2

Loopback

Patchcord to roof (20 m)

1.28Tbit/s Transmission

32x40Gbps error-free transmission for more than one hour under the daylight condition

Terminal 2

Achieved 1.28 Tera bits per second world record transmission for a wireless system using a system based a similar concept. E. Ciaramella, Y. Arimoto, G.Contestable, M. Presi, A. D’ Errico, V. Guanno, and M. Matsumoto, ” 1.28 Terabit/s (32x40 Gbit/s) WDM Transmission System for Free Space Optical Communications,” IEEE Journal Areas in Com. vol. 27, no. 9, Dec. 2009. 50

Institute of Communication, Information and Perception Technologies (TeCIP), Scuola Superiore Sant’Anna (SSS), Pisa Italy

Mitigation techniques by present system

Fiber Coupling

FPM

51

• We adopted adaptive optics to compensate the influence of light propagating in the atmosphere in real time. In particular, we adopted an optical axis control method using ultra-compact, biaxial, galvano mirror with fast response.

• The internal angle control is performed by monitoring the deflection angle by two-dimensional driving, and it operates stably up to 2 kHz in both azimuth (Az) and elevation (El) directions.

Optical Transceiver

Optical fiber

LD

LD

PD LD

LD

PD

PD PD Lens

Optical Transceiver

Elec.Sig. Elec.Sig.

Lens

Bidirectional FSO communication

BS BS

FP FP

Beacon

QPD QPD

PID PID

High Speed Mirror High Speed Mirror Lens Lens

Bidirectional FSO communication

Optical Fiber Input/Output

Optical Fiber Input/Output

2. New developed system: Ultra-compact moving coil type galvanometer mirror actuator

1. Conventional System

Optical fiber

52

• O/E/O conversion • Received by Large PD • Rough tracking by beacon signal

• No O/E/E conversion • Received by Fiber core • Rough tracking by beacon signal

QPD

QPD PID Fine

Tracking VCM

Fine Tracking VCM

Opt. Fiber

Opt. Fiber Opt.Fiber

BS

BS

Lens

Lens

Cont. sig

Cont. Sig

Info. Sig.

Info. sig.

Opt.Fiber

PID

VCM having the function of converting electric energy into kinetic energy with a magnetic field as a medium

3. Future system using closed loop voice coil actuator

Magnet Coil

Connecter Hall sensor

FSO Terminal Evolution-2

53

1. Development of eye-safe laser region Light wavelength: 1550 nm (1 wavelength) · Beacon light: 800-900nm unnecessary 2. Reduction in tracking servo technology, reduction in size, improvement in accuracy · Sensor: GPS, direction sensor, gyro · Control: VCM

1) We developed an FSO system which uses narrow beam transmission with direct coupling to the SMF fiber core and without performing O/E and E/O conversion, which make the communication link bandwidth and protocol transparent. Using technologies such as WDM and EDFA, high data rate in the order of several Gbps was demonstrated.

2) Evaluating the received optical power level and the propagation link quality for a continuous period of more than one year, the operating data rate exceeding 1.5 Gbps was demonstrated at a distance of 1-km with the link availability above 99.9%.

3) In the absence of severe weather conditions such as atmospheric turbulence, heavy rain, thick fog, snow and storm, the ISDB-T and W-CDMA signals were transmitted using the FSO system and good performance was achieved.

4) The obtained results confirm the technical feasibility and practicality of utilizing the FSO system as a universal platform for providing 5G wireless services.

Conclusion in FSO

54

Further Study

1) Development of a high-speed communication system between satellite stations, satellites, aircraft, railroads, ships and ground stations.

2) Realize a simple, inexpensive, robust FSO system and aim to spread FSO.

3) Consideration of standardization accompanying increase of multiple standards.

4) Further experiments are needed to gather data for statistical analysis of system performance under different weather conditions.

5) Building Initial Setting Free, Eye safe

55

OVERVIEW FOR OPTICAL WIRELESS COMMUNICATION

Thank you for your attention

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