<<

elliptical forallothervaluesof 90 of are difference components field electric two fixed the of amplitudes a the and degrees, has polarized Circularly difference elliptically of values the by groups three into classified be may light Polarized system; reference field; electric the where be expressed: can vector the location, any at t time at components vector Let proportional tothemeansquareofelectricfieldamplitude. electric The to consistofpartiallypolarizedorfullylight. beam light unpolarized. of direction example, the around propagation, randomly fluctuates Light function oftime. a as vector field electric the by plane transverse the in out traced 's optical the visualizing when field electric the we just field, sketch usually electric the to perpendicular always is field magnetic and field an electric oscillating an which in wave electromagnetic . vector of types all to common is that property a is Polarization components. 1(b) of difference phase relative a with components field function Figure directions, y and x the in respectively. Thephasedifferenceis field electric the of phases the are δ oscillating

the over time.(a)withaphasedifference,(b)nodifference. Fig.

, z polarization

there

is Ex E be

is

x x . 1

same 1

field In

called of

in , Spatial and

the

shows most

between

polarized classical and is time. the In

vector.

E so (ie. magnetic no direction

y

any

natural x-y representation Ey

What isPolarization? are the amplitudes of the x and y components of naturally

that,

e Figure phase δ electric of

x

: other plane. , the

= Polarization

e Its light. , linearly a

is the ; and frequency; angular the is y 90°

on are the unit vectors of the x-y orthogonal x-y the of vectors unit the are or

x optical of difference 1(a)

case,

General Photonics Corporation 909.590.5473 and and By produced average, unpolarized

Linearly field propagation.

of

propagate superposition polarized,

beam shows Ex y δ light x- the power

, Ex,andEy. is electric vectors and = defined

light

Ey

between polarized no is

can δ light y- the

is

= if ). modeled electric

direction through

beam circularly

δ

field its a The

be two in Then, x - (sunlight, in scalar of

plane the

represented terms

the δ polarization light components the orthogonal field y . can

space.

the as x-y two is

x- quantity

components of be polarized has

of

favored. a

and polarization

firelight) δ plane

polarization orthogonal the considered δ .

sinusoidal Since no x and x In

y-vector

state electric

pattern that by ( Figure phase

δ

as

=0).

and For the

its δ

is is is y a polarization. linear vertical designates V point opposite diametrically the chosen and arbitrarily An sphere states. the point on polarization points other elliptical All represent polarizations. linear equator the indicate on Points light. polarized circularly unique right-hand a and to corresponds state point polarization given Any form. polarization the change will retarder given any how predicting of It wave. electromagnetic propagating a of polarization in changes The Poincaré SphereandStokesVectors DOP canalsobeexpressedas: partially polarizedlight. DOP=1, Whenever with avaluebetween0and1. The degreeofpolarization(DOP)isdefinedby: which arethecoordinatesofonepointonPoincarésphere. If hand circularlypolarizedlightintensities. and intensities, light polarized linearly intensities, light polarized linearly where propagation oflight),theStokesvectorcanbeexpressedas: In physical interpretationrelatedtointensitymeasurement. related The

we provides a

Poincaré Stokes

given on normalize H Fig. 2Poincarésphererepresentationofpolarizationstates I

0

to on is the total power of the light, the of power total the is it www.generalphotonics.com the

DOP=0,

is Poincaré a Oxyz

the

parameters sphere. totally convenient

sphere

equator [ S

1 reference S light

polarized. 2 The sphere

is S

designates

3 is

way used ] by ] have two said

system representation. of

S

poles

Intermediate to a 0 to ,

representing

simple we describe

I be +45 horizontal

of (Oz will I unpolarized, ,

L the I ,

-45 -45

I I physical being R get x are the left and right and left the are

,

sphere are the cases I y

polarized the are the x- and y- y- and x- the are They linear

the polarization the

SOP

represent correspond

and interpretation

45° also direction polarization, [

s whenever light, and 1

s have 2

s -93- -45° left- and and

3

of to ], a

FAQS Applictia on Guide Accessories Special Polaritizaon OCT Products Modules INSTRUMENTSINSTRUMENTS Components INSTRUMENTS Special Polaritizaon FAQS Applictia on Guide Accessories Components OCT Products Modules INSTRUMENTS -94- while time, over constant fairly are fiber the of asymmetries a be may it or process, manufacturing the from fiber the in inherent out-of-round, or oval slightly and is core fiber the where strand, fiber-optic the of asymmetry the are the of causes directly slightly at travel fiber a inside light of components polarization different PMD What isPMD? slightly differenttimes,andthestateofpolarizationchanges. at fiber the exit parts two the the because broadened becomes pulse Consequently, speeds. different at travel pulse the of parts other the along principal transmits pulse the of the part of and one axes, along principal transmits pulse was the of it part then which in polarization, polarization of state launched. same the and in fiber the through emerges transmits pulse the fiber’s then the of axes, either principal with aligned polarization its with material If relative a experience phase differenceastheypropagatethroughthematerial. will axes two light the a of along components projected polarization two the result, a As axis. through principal other the in light plane-polarized than faster medium travels the axis principal one into launched light polarized transmits Therefore, Birefringence isalsocalleddoublerefraction. (n refraction, Usually, the of properties . the express to axes called axes principal orthogonal special two use may One different. are directions different along polarized light of speeds transmission If refraction ofthemedium. of index the is n and , a in light of speed the is c where be expressedas: same In What isBirefringence? light, respectively. where

result e an the ). a

mechanical

homogenous The optical stands

speed I pol light

different of

by

, this axis. However, difference through such I the mechanical

unp

the pulse regardless is

for

are the of polarized light and unpolarized and light polarized of intensity the are can index Because

as

propagating stresses birefringence speeds, polarization

a is or the

be if medium.

of between

launched

isotropic we ordinary stress expressed

refraction of of

launch as General Photonics Corporation 909.590.5473 on

polarization the shown

ν

on the =c/n If mode

n

in into medium's index medium, of 0

a and n and the

the

an fiber. is medium through the a

in pulse

a . deployed fiber (n anisotropic

measure Figure

optical e 0 state. is called birefringence. birefringence. called is )

The light

and with birefringence, made

is

different asymmetry

This 3. birefringent, extraordinary

fiber. propagates randomly fiber. of

of It PMD

how medium, speed, a occurs The

birefringent The indices is fast

oriented inherent the may

caused

ν plane- at major when index , can can ,

light

two

the

the be of PMD iscalleddifferentialgroupdelay(DGD). fiber mechanical stressduetomovementortemperaturechangeofthe is about3.2timestheaverageDGDofafiber. Figure any values in fixed Because terms

two polarizationcomponentstravelwithdifferentspeeds. the because broadens pulse optical An an and birefringence. axis, effective fast and slow a having plate retardation single a orientations Fig. particular

can value 3. over 3 www.generalphotonics.com of of As vary, A

its for time. real average an

time

dynamic Fig. 4MaxwelliandistributionofDGDS resulting and a fiber approximation,

The given

follows DGD, is probability

like properties, section in

and many a the dynamic

a

the Maxwellian of

retardation of fiber in

fiber. PMD maximum a series. DGD

has aspect

does Rather,

with plates a distribution It

distribution instantaneous is to not a

equivalent

with PMD. certain it have

is different

described 1st shown a value of

single, to order DGD DGD

at in