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{
"metadata": {
"name": "",
"signature": "sha256:3deb63e976713f6e36585549e6b144389b0fc28fe2982a2838d929f3804cde18"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"chapter8 - Optical receiver operation"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 8.2.1, page 8-6"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"from __future__ import division\n",
"from numpy import log, sqrt, pi, log10\n",
"P=10**-9 #probability of error\n",
"eta=1 #ideal detector\n",
"h=6.626*10**-34 #plank's constant\n",
"c=3*10**8 #speed of light\n",
"lamda=1*10**-6 #wavelength\n",
"B=10**7 #bit rate\n",
"Mn = -log(P) \n",
"print \"The quantum limit at the receiver to maintain bit error rate 10**-9 is (%.1f*h*f)/eta.\" %Mn\n",
"f=c/lamda\n",
"Popt= 0.5*Mn*h*f*B/eta #computing optical power\n",
"Popt_dB = 10 * log10(Popt) + 30 #optical power in dbm\n",
"Popt=Popt*10**12 \n",
"print \"Minimum incident optical power is %.1f W or %.1f dBm.\" %(Popt,Popt_dB) "
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The quantum limit at the receiver to maintain bit error rate 10**-9 is (20.7*h*f)/eta.\n",
"Minimum incident optical power is 20.6 W or -76.9 dBm.\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 8.2.2, page 8-8"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"SN_dB=60 #signal to noise ratio\n",
"h=6.626*10**-34 #plank's constant\n",
"c=3*10**8 #speed of light\n",
"lamda=1.3*10**-6 #wavelength\n",
"eta=1 \n",
"B=6.5*10**6 #Bandwidth\n",
"SN=10**(SN_dB/10) \n",
"f=c/lamda\n",
"Popt= 2*SN*h*f*B/eta #computing optical power\n",
"Popt_dB = 10 * log10(Popt) + 30 #optical power in dbm\n",
"Popt=Popt*10**6 \n",
"print \"Incident power required to get an SNR of 60 dB at the receiver is %.4f microWatt or %.3f dBm\" %(Popt,Popt_dB)\n",
"#Calculation error in the book.They have take SN as 10**5 while calculating, which has lead to an error in final answer\n",
"#answer in the book 198.1nW and -37.71 dBm"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Incident power required to get an SNR of 60 dB at the receiver is 1.9878 microWatt or -27.016 dBm\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 8.3.1, page 8-11"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"lamda=0.85*10**-6 \n",
"h=6.626*10**-34 #plank's constant\n",
"c=3*10**8 #speed of light\n",
"q=1.6*10**-19 #charge of electron\n",
"eta=65/100 #quantum efficiency\n",
"P0=300*10**-9 #optical power\n",
"Id=3.5 #dark current\n",
"B=6.5*10**6 #bandwidth\n",
"K=1.39*10**-23 #Boltzman constant\n",
"T=293 #temperature\n",
"R=5*10**3 #load resister\n",
"Ip= 10**9*eta*P0*q*lamda/(h*c) \n",
"Its=10**9*(2*q*B*(Ip+Id)) \n",
"Its=sqrt(Its) \n",
"print \"rms shot noise current is %.2f nA.\" %(Its) \n",
"It= 4*K*T*B/R \n",
"It=sqrt(It) \n",
"It=It*10**9 \n",
"print \"Thermal noise is %.2f nA.\" %(It) \n",
"#answer given in book for Thermal noise is wrong."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"rms shot noise current is 0.53 nA.\n",
"Thermal noise is 4.60 nA.\n"
]
}
],
"prompt_number": 9
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 8.3.2, page 8-12"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"lamda=0.85*10**-6 \n",
"h=6.626*10**-34 #plank's constant\n",
"c=3*10**8 #speed of light\n",
"q=1.6*10**-19 #charge of electron\n",
"eta=65/100 #quantum efficiency\n",
"P0=300*10**-9 #optical power\n",
"Id=3.5 #dark current\n",
"B=6.5*10**6 #bandwidth\n",
"K=1.39*10**-23 #Boltzman constant\n",
"T=293 #temperature\n",
"R=5*10**3 #load resister\n",
"F_dB=3 #noise figure\n",
"F=10**(F_dB/10) \n",
"Ip=10**9*eta*P0*q*lamda/(h*c) \n",
"Its=10**9*(2*q*B*(Ip+Id)) \n",
"It1= 4*K*T*B*F/R \n",
"SN= Ip**2/(Its+It1) \n",
"SN_dB=10*log10(SN) \n",
"SN=SN\n",
"print \"SNR is %.2e or %.2f dB.\" %(SN,SN_dB) \n",
"#answer given in the book is wrong."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"SNR is 6.25e+04 or 47.96 dB.\n"
]
}
],
"prompt_number": 13
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example 8.4.1, page 8-14"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"Cd=7*10**-12 \n",
"B=9*10**6 \n",
"Ca=7*10**-12 \n",
"R=(2*3.14*Cd*B)**-1 \n",
"B1=(2*3.14*R*(Cd+Ca))**-1 \n",
"R=R/1000 \n",
"B1=B1/10**6 \n",
"print \"\"\"Thus for 9MHz bandwidth maximum load resistance is %.2f Kohm\n",
"Now if we consider input capacitance of following amplifier Ca then Bandwidth is %.2fMHz\n",
"Maximum post detection bandwidth is half.\"\"\"%(R,B1) \n",
"#answer for resistance in the book is wrong"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Thus for 9MHz bandwidth maximum load resistance is 2.53 Kohm\n",
"Now if we consider input capacitance of following amplifier Ca then Bandwidth is 4.50MHz\n",
"Maximum post detection bandwidth is half.\n"
]
}
],
"prompt_number": 14
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Question 7, page 8.44"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"w=25*10**-6 #width\n",
"v=3*10**4 #velocity\n",
"t=w/v #computing drift time\n",
"BW=(2*pi*t)**-1 #computing bandwidth\n",
"rt=1/BW #response time\n",
"rt=rt*10**9 \n",
"print \"Maximum response time is %.2f ns.\" %(rt) \n",
"#Answer in the book is wrong."
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"Maximum response time is 5.24 ns.\n"
]
}
],
"prompt_number": 16
}
],
"metadata": {}
}
]
}
|
