OPTICS AND OPTOELECTRONICS VOLUME: 12 |NUMBER: 6 |2014 |SPECIAL ISSUE
VLC T ansmi e wi h Plas ic Op ical Fibe s o
Indoo F ee Space Op ic Ne wo ks
Jan VITASEK, Pe SISKA, S anisla KEPAK, Jakub CUBIK,
Radek POBORIL and Jan LATAL
Depa men o Telecommunica ions, Facul y o Elec ical Enginee ing and Compu e Science,
VSB–Technical Uni e si y o Os a a, 17. lis opadu 15, 708 33 Os a a, Czech Republic.
[email p o ec ed], pe .sisk[email p o ec ed], s anisla .k[email p o ec ed], [email p o ec ed],
adek.pob[email p o ec ed], [email p o ec ed]
Abs ac . This a icle deals wi h he cons uc ion de-
sign o op ical ansmi e o indoo F ee Space Op ic
(FSO) ne wo ks. This op ical ansmi e will be able
o p o ide he ligh ing and communica ion a he same
ime. Thanks o special solu ion in spec al cha ac e is-
ic o ansmi ed ligh i is necessa y o use wo LEDs
adia ion sou ces. The ligh beams o hese LEDs ha e
o be spa ially o e lapped in c issc oss di ec ion and
hen he ansmi e can ealize bo h unc ions. The e
is desc ibed a cons uc ion o op ical ansmi e wi h
plas ic op ical ibe s which me ges wo LED beams o-
ge he and p o ide ligh ing and communica ion a he
same ime.
Keywo ds
Illumina ion, indoo FSO, LED, plas ic op i-
cal ibe , ansmi e , Visible Ligh Communi-
ca ion VLC.
1. In oduc ion
The mos impo an pa ame e s o communica ion o
no mal use a e high da a a e and mobili y. Radio
wi eless ne wo ks could ealize hese wo pa ame e s,
he e o e hey became so success ul. Howe e , use de-
mands on da a a e con inuously inc ease; he e o e
i is necessa y o ind o he solu ions and imp o e-
men s. In his ield op ical links begin g adually mo e
and mo e es ablish, because hey a e able o p o ide
high da a a e and mobili y is also possible. Visible
Ligh Communica ion (VLC) is a p omising example
o op ical echnology, which could be used in indoo
spaces. VLC holds a en ion in academia and indus y
hanks o la ge p og ess in de elopmen o LEDs. Cu -
en LED ea u es a e a he le el, which enables hem
g adually eplace classical illumina ion sou ces (incan-
descen ligh bulbs and luo escen lamps). Mo eo e ,
LEDs could be modula ed a high bi a es in compa -
ison o classical illumina ion sou ces. The e o e LED
ea u es di ec ly challenge using hem o illumina ion
and communica ion a he same ime.
The ad an age o op ical communica ion is high da a
a e, no legisla i e es ic ion, no in e e ences wi h a-
dio links, small size, low powe consump ion and da a
sa e y. On he o he side, i is necessa y o keep limi s
o op ical powe o human eyes and o squa e up wi h
op ical noise.
2. Cu en Indoo F ee Space
Op ic Ne wo ks
Indoo FSO ne wo ks could be di ided acco ding o he
line o sigh be ween ansmi e and ecei e and ac-
co ding o di ec i i y o anscei e s [1]. The o he
classi ica ion is acco ding o used op ical spec um,
which is mo e impo an and mo e in e es ing o his
a icle. P esen ly, he in a ed (IR) ligh o isible ligh
a e used o communica ion indoo [2]. IR ansmis-
sion is de ined by se e al s anda ds wi h di e en bi
a es. The highes bi a e acco ding o I DA asso-
cia ion is 16 Mb·s−1[1]. Using isible ligh o com-
munica ion has se e al ad an ages, which ha e been
men ioned abo e. Mo eo e , VLC also p o ides illu-
mina ion. Se e al expe imen s ha e been done, when
he bi a e g ea ly exceeds 100 Mb·s−1[2]. This is sub-
s an ially mo e han IR can p o ide. This is also he
eason, why using o whi e ligh o illumina ion and IR
o communica ion is no ad an ageous. In addi ion,
s ic e op ical powe limi s hold o IR. As expec ed,
VLC also has a disad an age. This disad an age is
whi e ligh emi ing LED.
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3. Cu en Visible Ligh
Communica ion VLC
Whi e LEDs a e key elemen s o Visible Ligh Com-
munica ion VLC. Whi e ligh c ea ion is no simple
issue, which e lec s in VLC ea u es. P esen ly, VLC
uses he whole emi ed spec um o whi e LED o da a
ansmission.
The e exis wo main me hods, how o c ea e a whi e
ligh using LEDs. The i s me hod uses mo e colo
ligh sou ces; he o he me hod uses a blue ligh sou ce
and a sui able wa eleng h con e e , e.g. yellow phos-
pho [3] [4]. The i s ype o whi e LED consis s o
h ee ligh sou ces (blue, g een, ed) which a e sup-
plied in co ec p opo ion. This me hod is mo e com-
plex and mo e expensi e [2], bu enables o c ea e any
o he colo . VLC needs powe LEDs o a su icien
co e age o equi ed space by ligh . The o wa d cu -
en o powe LED is up o 700 mA [5]. I powe LED
should p o ide illumina ion and communica ion a he
same ime, i has o be modula ed as enough. Bu
qui e high o wa d cu en can limi he modula ion
a e hanks o swi ching on and o [6].
The o he ype o whi e LED consis s o a blue ligh
emi ing chip. A po ion o blue ligh exci es a yel-
low phospho (Y ium Aluminium Ga ne Y3Al5O12),
which c ea es yellow ligh . Mixing o blue and yellow
ligh s c ea es a whi e ligh . The modula ion a e is
limi ed by slow esponse o phospho . This me hod is
simple and cheape .
Thanks hese limi a ions we p oposed a new ype
o ansmi e o indoo FSO ne wo ks which uses
only a pa o isible spec um o da a ansmission.
The pa o o iginal spec um emi ed by whi e LED
is pu posely supp essed by op ical no ch il e . The
supp essed pa is hen eplaced by ligh om ano he
LED which will be modula ed. Bo h hese LEDs c ea e
oge he o iginal whi e ligh . The ad an age is, ha
whi e powe LED emi s con inuously, he e o e he dis-
ad an ages o high cu en swi ching o phospho delay
do no appea . The use ul da a will be ansmi ed by
a na ow spec al LED, which eplaces he supp essed
pa . I will be supplied by lowe o wa d cu en and
he e o e i can be modula ed as e . The p oblem is
how o me ge wo op ical beams om he powe LEDs
spa ially oge he . The aim o his a icle is no a de-
sc ip ion o new VLC me hod, i has been desc ibed
in [7] and [8]. The aim is a solu ion o p oblem how
o spa ially me ge wo op ical beams oge he in o one
beam.
Nowadays, VLC is e y in e es ing a ea o esea ch,
many calls and p ojec a e aimed a imp o ing and
sea ching new possibili ies o VLC.
4. Spa ial Me ging o Beams
om LEDs
The one solu ion o his p oblem has been ound and
p esen ed in [9]. We ha e hough ou , se and mea-
su ed s ill ano he solu ion. The basis o beams me g-
ing a e again pa abolic e lec o s [10], which we e se
o he powe LEDs and beamspli e 50T/50R. The
beamspli e 50T/50R me ges wo op ical beams in
powe and spa ial p ope ies co ec ly and i c ea es
o iginal whi e ligh . The disad an age o beamspli e
50T/50R is a de lec ion o a hal o op ical powe . In
[9], a mi o was used o pa allel di ec ion o beam.
The basis o his ype o op ical ansmi e is wo
plas ic op ical ibe s [11]. The plas ic op ical ibe s
we e chosen hanks o hei la ge diame e . The di-
ame e o cladding is 10 mm; he diame e o co e is
8.6 mm. O he op ical p ope ies a e summa ized in
Tab. 1. The ligh which passed h ough beamspli e
would be e y di icul o couple in classical op ical
ibe and he loss o op ical powe would be g ea .
Tab. 1: Op ical p ope ies o plas ic op ical ibe .
Ti le Symbol Value
Co e Diame e d18.6 mm
Ou e Diame e d210 mm
Re ac i e Index: n11.492
Co e
Re ac i e Index: n21.343
Cladding
Nume ical Ape u e NA 0.65
Spec al T ans. Range ∆λ380–750 nm
The i s beam om beamspli e ’s ou pu is coupled
in o he i s plas ic ibe ; he o he beam om o he
beamspli e ou pu is coupled in o he o he plas ic
ibe . Fo coupling beams in o plas ic ibe s wo ach o-
ma ic lenses AC254-030-A-ML [12] we e used. The
lens is ach oma ic double s o isible pa o spec um.
The diame e o lens is 25.4 mm; ocal leng h is 30 mm.
All impo an pa ame e s o ach oma ic lens a e w i -
en in Tab. 2.
Tab. 2: Impo an pa ame e s o ach oma ic lens.
Ti le Symbol Value
Lens Diame e D25.4 mm
Focal Lengh 30.0 mm
Back Focal Lengh b22.9 mm
Radius o Cu a u e R120.9 mm
Radius o Cu a u e R2-16.7 mm
Radius o Cu a u e R3-79.8 mm
Cen e Thickness c112.0 mm
Cen e Thickness c22.0 mm
Edge Thickness e8.8 mm
When he ligh is coupled in o plas ic op ical ibe s,
he ends o plas ic ibe s could be sui able loca ed on
he ceiling o oom and pe o m he bes ligh co e-
age o oom. Fo sui able co e age wo ibe s will
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no be su icien , he e o e ano he ligh di iding in o
mo e ibe s is supposed, which ensu es equi ed co e-
age. The ends o ibe s will be specially modi ied o
e ec i e oom co e age. In his a icle he coupling
om beamspli e in o plas ic op ical ibe s is sol ed.
The scheme o op ical ansmi e is in Fig. 1.
whi e
LED
communica ion
LED
beam
spli e
op ical
il e
plas ic op ical
ibe
plas ic op ical
ibe
ach oma ic
lens
ach oma ic
lens
Fig. 1: Scheme o op ical ansmi e .
The cons uc ion o his ansmi e depends on he
co ec placing o plas ic ibe s inpu s o he u mos
ligh coupling. Fo his pu pose a simula ion in so -
wa e Ligh Tools was done and i s esul s we e e i ied
in labo a o y on ansmi e p o o ype which was se
om op ical componen s on op ical able.
5. Simula ions in Ligh Tools
So wa e Ligh Tools enables modelling o a ious op i-
cal sys ems. I s unique design and analyzing ea u es
combined wi h i s simple way o ope a ion, i s suppo
o a quick design and op imiza ion make ob aining o
esul s acco ding o he p ede ined condi ions possible.
This so wa e includes a la ge componen lib a y. I is
possible o change many pa ame e s. The esul s a e
e y p ecise [13].
In so wa e Ligh Tools he op ical ansmi e wi h
plas ic op ical ibe s was c ea ed, as shown in Fig. 2.
The a ge o simula ion was o ind ou whe he i is
possible o couple he beams om beamspli e in o
plas ic ibe s. The impo an elemen is ach oma ic
lens which collima es he beam in i s ocus. Thanks
o he so wa e Ligh Tools i was possible o simula e
how small beam spo he ach oma ic lens c ea es and
in wha dis ance om he end o lens i is. In his
place, he inpu s o plas ic ibe s we e placed o he
bes ligh coupling.
Fig. 2: Simula ion in Ligh Tools.
In so wa e Ligh Tools a measu ing plain was c e-
a ed. This measu ing plain was placed in dis ance
18 mm om he end o ach oma ic lens and he sim-
ula ion was un. The e alua i e c i e ion was a Full
Wid h a Hal Maximum (FWHM). A a ge was o
ind such dis ance in which a beam spo is he na ow-
es . The esul s calcula ed by simula ion a e summa-
ized in Tab. 3. F om his able i is ob iously ha he
na owes beam spo is in dis ance 24 mm om he
end o ach oma ic lens.
Tab. 3: Simula ion o he na owes beam spo .
Dis ance FWHMxFWHMy
[mm] [mm] [mm]
18 8.59 8.59
19 8.54 8.54
20 8.47 8.48
21 8.41 8.41
22 8.40 8.41
23 8.39 8.39
24 8.37 8.38
25 8.41 8.41
26 8.44 8.43
27 8.49 8.48
28 8.53 8.54
29 8.59 8.59
30 8.66 8.65
Fu he i was simula ed in Ligh Tools how much o
op ical powe eaches he co e o plas ic op ical ibe
and how much eaches he cladding. The so wa e cal-
cula ed ha 96.6 % o op ical powe , which passed
h ough he lens, eaches he co e in he i s one way,
in he o he one way i was 96.4 % o op ical powe .
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6. Measu emen in Labo a o y
The simula ion in so wa e Ligh Tools showed ha i
is possible o se an op ical ansmi e wi h plas ic
op ical ibe s. In labo a o y on op ical able, he op-
ical ansmi e was cons uc ed. The scheme is in
Fig. 2. The cons uc ed ansmi e is consonan wi h
ansmi e which was c ea ed in so wa e Ligh Tools.
I was measu ed in which dis ance om he end o
ach oma ic lens he spo o me ged beam is he na -
owes . Fo his pu pose a measu emen was done, i s
aim was o measu e he beam spo in se e al dis ances
om he end o ach oma ic lens and o ind in such way
he dis ance in which he beam spo is he na owes .
Two mo o ized linea ansla ion s ages and powe me-
e wi h pho ode ec o we e used o measu emen .
Beam p o iles we e measu ed in se e al dis ances
om he end o ach oma ic lens. The powe me e was
placed in dis ance 18 mm om he end o ach oma ic
lens. Powe me e mo ed in ans e se di ec ion wi h
s ep 1 mm. In his he beam p o iles we e measu ed
in he ange om −15 mm o 15 mm. Then he pow-
e me e was mo ed in dis ance 19 mm om he end
o ach oma ic lens and he beam p o ile was measu ed
again. In his way he beam p o iles we e measu ed up
o dis ance 30 mm om he end o ach oma ic lens. Fo
each dis ance a g aph o ela i e op ical powe was se
o measu e FWHM. The measu ed esul s a e summa-
ized in Tab. 4. I is ob iously om his able ha he
na owes beam spo was in dis ance 24 mm om he
end o ach oma ic lens. This esul is consonan wi h
he simula ion in Ligh Tools which is summa ized in
Tab. 3. The p o ile o beam spo in y-axis di ec ion
was also measu ed in dis ance 24 mm. FHWMywas
8.99 mm in his dis ance.
Tab. 4: Measu emen o he na owes beam spo .
Dis ance FWHMx
[mm] [mm]
18 9.42
19 9.35
20 9.25
21 9.18
22 9.13
23 9.11
24 9.04
25 9.13
26 9.18
27 9.25
28 9.35
29 9.54
30 9.73
7. Conclusion
The simula ion and he eal measu emen o op i-
cal ansmi e wi h plas ic op ical ibe s in es iga ed
abo e all he coupling o ligh beams in o plas ic ibe s
by ach oma ic lenses. The simula ion showed ha
he beam could be ocused o couple in o plas ic op-
ical ibe , because he beam spo is enough na ow.
The Ligh Tools calcula ed how much pe cen o op i-
cal powe couples in o op ical ibe . The measu emen
ound he posi ion in which he op ical powe is he
g ea es . A e ha he measu emen o beam p o iles
behind he ach oma ic lens was done.
The simula ion measu ed na owe FWHM han he
measu emen . I is gi en by highe p ecision o simu-
la ion in compa ison o measu emen . The impo an
is ha he na owes beam spo is in dis ance 24 mm
om he end o ach oma ic lens. Simula ion and mea-
su emen ag eed well.
The simula ion and he measu emen showed ha
i is possible o se an op ical ansmi e wi h plas-
ic op ical ibe s. This ansmi e is no inished ye ,
u he i is necessa y o deal wi h dis ibu ion o ligh
coupled in o plas ic op ical ibe s.
O he nex s ep is a cons uc ion o modula o wi h
sui able modula ion and line code o bi a e es ing.
I seems ha OOK wi h Manches e coding should be
in e es ing o his VLC ansmi e .
Acknowledgmen
This a icle was c ea ed wi h he ac i e suppo by
he Minis y o Educa ion o he Czech Republic
wi hin he p ojec s no. SP2014/77, SP2014/147 and
SP2015/182 o he VSB–Technical Uni e si y o Os-
a a. This a icle was also suppo ed by p ojec s
VG20102015053, TA03020439 and TA04021263. The
esea ch has been pa ially suppo ed by he p ojec
No. CZ.1.07/2.3.00/20.0217 "The De elopmen o
Excellence o he Telecommunica ion Resea ch Team
in Rela ion o In e na ional Coope a ion" wi hin he
ame o he ope a ion p og amme "Educa ion o com-
pe i i eness" inanced by he S uc u al Funds and
om he s a e budge o he Czech Republic.
Re e ences
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SUN. Op ical wi eless communica ions: IR o
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[2] GHASSEMLOOY, Z., W. POPOOLA and S. RA-
JBHANDARI. Op ical Wi eless Communica ions:
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Abou Au ho s
Jan VITASEK was bo n in Opa a. In 2009 he ini-
shed M.Sc. s udy a B no Uni e si y o Technology,
Facul y o Elec ical Enginee ing and Communica ion.
In 2014 he inished Ph.D. s udy a Depa men o
Telecommunica ions, VSB–Technical Uni e si y o
Os a a. His in e es s a e F ee Space Op ics, indoo
F ee Space Op ics ne wo ks and isible ligh commu-
nica ion. He is a membe o SPIE. He is engaged in
p ojec dealing wi h VLC.
Pe SISKA was bo n in 1979 in K ome iz. In
2005 he comple ed his M.Sc. s udies a VSB–
Technical Uni e si y o Os a a. Th ee yea s la e
he comple ed his Ph.D. s udies. He is cu en ly
employed a he Depa men o Telecommunica ions.
He is in e es ed in op ical communica ions, ibe op ic
senso s and Dis ibu ed Tempe a u e Sensing sys ems.
S anisla KEPAK was bo n in 1987 in Os-
a a. In 2009 he ecei ed Mas e ’s deg ee in he ield
o Telecommunica ions. He is cu en ly Ph.D. s uden ,
and he wo ks in he ield o op ical communica ions
and ibe op ic senso sys ems.
Jakub CUBIK was bo n in 1986 in Olomouc.
In 2011 he ecei ed Mas e ’s deg ee in he ield o
Telecommunica ions. He is cu en ly Ph.D. s uden ,
and he wo ks in he ield o op ical communica ions
and ibe op ic senso sys ems.
Radek POBORIL was bo n in Valasske Mezi ici.
He ecei ed his M.Sc. deg ee om he VSB–Technical
Uni e si y o Os a a, Facul y o Elec ical Enginee -
ing and Compu e Science in 2013. Cu en ly in a
Ph.D. s uden , he ocuses on op ical echnologies and
especially on WDM/TDM PON.
Jan LATAL was bo n in P os ejo . In 2008 he
was awa ded his M.Sc. deg ee a VSB–Technical Uni-
e si y o Os a a, Facul y o Elec ical Enginee ing
and Compu e Science, Depa men o Elec onics and
Telecommunica ions. He is cu en ly Ph.D. s uden ,
and he wo ks in he ield o Wi eless Op ical Commu-
nica ions, Op ical Communica ions and Dis ibu ed
Tempe a u e Sensing Sys ems.
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