solution

SolutionsofChapter8-9

1.A116couplerhasoneinputportand16outputports,alloutputportsareequal.

Iftheinputsignalpoweris-10dBm，computerthepowerofoneoutputport.

Solution:



out

1163412dB

PdBm10dBm1222dBm





Whenlightistransmittingfromafiberofcoreradiusatoonehavingcore

radiusb,suppoabandthebothfibersarestep-indexandmultimode.

Computertheloss.

Solution:

2

outin

2

2

out

101010

2

in

b

PP

a

P

bb

Loss(dB)10log10log20log(dB)

Paa





athree-wavelengthfiber-gratingdemultiplexer,showinghowthetotal

threewavelengths1



,2



,3



canbedetectedindividually.(Hint,Fig.9.48inthe

textbook)

Solution:

t2gratingsaredesignedtoreflectat

wavelength

3

,andtransmittheothertwowavelengths,whiletheright2gratingsaredesigned

toreflectatwavelength

2

,andtransmitthewavelength

1

.Thus,thetotalthreewavelengths

canbedetectedindividually

-portdirectionalcoupler(DC)showsbelow,assume

12

PP,writethe

expressionsofThroughputLoss,TapLoss,Directionality,ExcessLossand

SplittingRatio.

Solution:

1)ThroughputLoss

L

THP

=-10log(P

1

/P

0

)

2)TapLoss

L

TAP

=-10log(P

2

/P

0

)

3)Directionality

L

D

=-10log(P

3

/P

0

)

4)ExcessLoss

L

E

=-10log[(P

1

+P

2

)/P

0

]

5)SplittingRatio

SR=(P

1

/P

2

)

increaingratingperiodfromanincreaintemperatureis0.1%per℃.

1)Calculatethegratingperiod.

2)Whatisthechangeinresonantwavelengthper℃?Givetheanswerinnm/℃.

Solution:assumetherefractiveindexoffibercoreis1.5

1)accordingto(9.19)inpage304,wecanget:

2





,hereismeasuredinthefibercore,so

0

1550

516.7

2221.5

nm

n









2)

0

0.1%0.1%0.5167

516.7

0.5167

221.51.55

CCC

nnm

C









