Chapter05: Design Considerations in Optical Links

Ex5.3.1:Pg-5.7

In [5]:
#Given

B= 15*10**-6 
L= 4 
BER= 1*10**-9 
Ls= 0.5 
Lc= 1.5 
alpha= 6 
Pm= 8 
Pt= 2*Lc +(alpha*L)+(Pm) 
print " The actual loss in fibre in dB =",int(Pt) 
Pmax = -10-(-50) 
print " \nThe maximum allowable system loss in dBm = ",Pmax 
 The actual loss in fibre in dB = 35
 
The maximum allowable system loss in dBm =  40

Ex5.3.2:Pg-5.8

In [8]:
#Given
import math
Ps= 0.1 
alpha = 6 
L= 0.5 
Ps = 10*math.log10(Ps) 
NA= 0.25 
Lcoupling= -10*math.log10(NA**2) 
Lf= alpha*L 
lc= 2*2 
Pm= 4 
Pout = Ps-(Lcoupling+Lf+lc+Pm) 
print " The actual power output in dBm = ",int(Pout) 
Pmin = -35 
print " Minimum input power required in dBm= ",Pmin 
print " As Pmin > Pout, system will perform adequately over the system operating life." 
 The actual power output in dBm =  -33
 Minimum input power required in dBm=  -35
 As Pmin > Pout, system will perform adequately over the system operating life.

Ex5.3.3:Pg-5.8

In [10]:
#Given

Ps= 5 
Lcoupling = 3 
Lc= 2 
L_splicing = 50*0.1 
F_atten  = 25 
L_total = Lcoupling+Lc+L_splicing+F_atten 
P_avail = Ps-L_total 
sensitivity = -40 
loss_margin = -sensitivity-(-P_avail) 
print " The loss margin of the system in dBm= -",loss_margin 
sensitivity_fet = -32 
loss_margin_fet=-sensitivity_fet-(-P_avail) 
print "The loss marging for the FET receiver in dBm= -",loss_margin_fet 
 The loss margin of the system in dBm= - 10.0
The loss marging for the FET receiver in dBm= - 2.0

Ex5.3.4:Pg-5.9

In [12]:
#Given
LED_output = 3 
PIN_sensitivity = -54 
allowed_loss= LED_output -(-PIN_sensitivity) 
Lcoupling = 17.5 
cable_atten = 30 
power_margin_coupling= 39.5 
power_margin_splice=6.2 
power_margin_cable=9.5 
final_margin= power_margin_coupling+power_margin_splice+power_margin_cable 
print " The safety margin in dB =",final_margin
 # Answer in book is wrong...
print " \n***NOTE- Answer wrong in book..."
 The safety margin in dB = 55.2
 
***NOTE- Answer wrong in book...

Ex5.3.5:Pg-5.10

In [14]:
#Given

optical_power=-10 
receiver_sensitivity=-41 
total_margin= optical_power-receiver_sensitivity 
cable_loss= 7*2.6 
splice_loss= 6*0.5 
connector_loss= 1*1.5 
safety_margin= 6 
total_loss= cable_loss+splice_loss+connector_loss+safety_margin 
excess_power_margin= total_margin-total_loss 
print " The system is viable and provides excess power margin in dB=",excess_power_margin 
 The system is viable and provides excess power margin in dB= 2.3

Ex5.4.1:Pg-5.13

In [16]:
#Given
import math
Ttx= 15 
Tmat=21 
Tmod= 3.9 
BW= 25.0 
Trx= 350.0/BW 

Tsys = math.sqrt(Ttx**2+Tmat**2+Tmod**2+Trx**2) 
print " The system rise time in ns.= ",round(Tsys,2) 
 The system rise time in ns.=  29.62

Ex5.4.2:Pg-5.14

In [19]:
#Given
import math

Ttrans = 1.75*10**-9 
Tled = 3.50*10**-9 
Tcable=3.89*10**-9 
Tpin= 1*10**-9 
Trec= 1.94*10**-9 
Tsys= math.sqrt(Ttrans**2+Tled**2+Tcable**2+Tpin**2+Trec**2) 
Tsys=Tsys*10**9  # converting in ns for dislaying...
print " The system rise time in ns= ",round(Tsys,2)
Tsys=Tsys*10**-9 
BW= 0.35/Tsys 
BW=BW/1000000.0  # converting in MHz for dislaying...
print " \nThe system bandwidth in MHz =",round(BW,2)
 The system rise time in ns=  5.93
 
The system bandwidth in MHz = 58.99

Ex5.4.3:Pg-5.14

In [21]:
#Given
import math
Ttx= 8*10**-9 
Tintra= 1*10**-9 
Tmodal=5*10**-9 
Trr= 6*10**-9 
Tsys= math.sqrt(Ttx**2+(8*Tintra)**2+(8*Tmodal)**2+Trr**2) 

BWnrz= 0.7/Tsys 
BWnrz=BWnrz/1000000  # converting in ns for dislaying...
BWrz=0.35/Tsys 
BWrz=BWrz/1000000  # converting in ns for dislaying...
print " Maximum bit rate for NRZ format in Mb/sec= ",round(BWnrz,2)
print " \nMaximum bit rate for RZ format in Mb/sec= ",round(BWrz,2) 
 Maximum bit rate for NRZ format in Mb/sec=  16.67
 
Maximum bit rate for RZ format in Mb/sec=  8.33

Ex5.4.4:Pg-5.15

In [24]:
#Given
import math
Ts= 10*10**-9 
Tn=9*10**-9 
Tc=2*10**-9 
Td=3*10**-9 
BW= 6*10**6 
Tsyst= 1.1*math.sqrt(Ts**2+(5*Tn)**2+(5*Tc)**2+Td**2) 
Tsyst=Tsyst*10**9  # converting in ns for displying...
Tsyst_max = 0.35/BW 
Tsyst_max=Tsyst_max*10**9  # converting in ns for displying...
print " Rise system of the system in ns= ",round(Tsyst,2)
print " \nMaximum Rise system of the system in ns= ",round(Tsyst_max,2)
print " \nSpecified components give a system rise time which is adequate for the bandwidth and distance requirements of the optical fibre link." 
 Rise system of the system in ns=  51.99
 
Maximum Rise system of the system in ns=  58.33
 
Specified components give a system rise time which is adequate for the bandwidth and distance requirements of the optical fibre link.

Ex5.5.1:Pg-5.18

In [31]:
#Given

del_t_1 = 10*100*10**-9 
Bt_nrz_1 = 0.7/(del_t_1*1000000) 
Bt_rz_1 = 0.35/(del_t_1*1000000) 
print "First case."
print " \nBit rate for nrz in Mb/sec= ",Bt_nrz_1 
print " \nBit rate for rz in Mb/sec= ",Bt_rz_1 
del_t_2 = 20*1000*10**-9 
Bt_nrz_2 = 0.7/(del_t_2*1000000) 
Bt_rz_2 = 0.35/(del_t_2*1000000) 
print " \n\nSecond case" 
print " \nBit rate for nrz in Mb/sec= ",Bt_nrz_2 
print " \nBit rate for rz  in Mb/sec= ",Bt_rz_2 
del_t_3 = 2*2000*10**-9 
Bt_nrz_3 = 0.7/(del_t_3*1000) 
Bt_rz_3 = 0.35/(del_t_3*1000) 
print " \n\nThird case" 
print " \nBit rate for nrz in BITS/sec= ",int(Bt_nrz_3) 
print " \nBit rate for rz  in BITS/sec= ",Bt_rz_3 
First case.
 
Bit rate for nrz in Mb/sec=  0.7
 
Bit rate for rz in Mb/sec=  0.35
 

Second case
 
Bit rate for nrz in Mb/sec=  0.035
 
Bit rate for rz  in Mb/sec=  0.0175
 

Third case
 
Bit rate for nrz in BITS/sec=  174
 
Bit rate for rz  in BITS/sec=  87.5