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   "source": [
    "# Chapter 25 : Fiber Optic Systems"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example 1 : pg 919"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
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   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The system margin is 7.011 dB\n"
     ]
    }
   ],
   "source": [
    " \n",
    "# page no 919\n",
    "# prob no 25_1\n",
    "#calculate the system margin\n",
    "#given\n",
    "from math import log10\n",
    "span_length = 40#in km\n",
    "Pin_mW = 1.5\n",
    "signal_strength_dBm = -25\n",
    "fiber_length = 2.5#in km\n",
    "loss_per_slice_dB = 0.25\n",
    "f_loss_dB_per_km = 0.3\n",
    "loss_connector_dB = 4\n",
    "#calculations\n",
    "Pin_dBm = 10 * log10(Pin_mW)\n",
    "splices = span_length / fiber_length - 1\n",
    "fiber_loss = span_length * f_loss_dB_per_km\n",
    "splice_loss = splices * loss_per_slice_dB\n",
    "T_loss = fiber_loss + splice_loss + loss_connector_dB\n",
    "P_out = Pin_dBm - T_loss\n",
    "sys_margin = P_out - signal_strength_dBm\n",
    "#results\n",
    "print 'The system margin is',round(sys_margin,3),'dB'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example 2 : pg 921"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The maximum permissible value for the pulse-spreading constant is 2.22 ns/km\n"
     ]
    }
   ],
   "source": [
    " \n",
    "# page no 921\n",
    "# prob no 25_2\n",
    "#calculate the max permissible value\n",
    "#given\n",
    "L=45;#in km\n",
    "dt=100.;#in ns\n",
    "#calculations\n",
    "#The maximum permissible value for the pulse-spreading constant is \n",
    "D=dt/L;\n",
    "#results\n",
    "print 'The maximum permissible value for the pulse-spreading constant is',round(D,2),'ns/km'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example 3 : pg 922"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a) The maximum bit rate for NRZ 0.00743 GHz\n",
      "b) The maximum bit rate for NRZ 0.00371 GHz\n"
     ]
    }
   ],
   "source": [
    " \n",
    "# page no 922\n",
    "# prob no 25_3\n",
    "#calculate the max bitrate in both cases#given\n",
    "#given\n",
    "from math import sqrt\n",
    "L=45.;\n",
    "T_Rtx=50.; T_Rrx=75.; T_Rf=100.;\n",
    "#calculations and results\n",
    "T_RT=sqrt(T_Rtx**2 + T_Rrx**2 + T_Rf**2);\n",
    "# a) for NRZ\n",
    "fb=1/T_RT;\n",
    "print 'a) The maximum bit rate for NRZ',round(fb,5),'GHz'\n",
    "# b) for RZ\n",
    "fb=1/(2*T_RT);\n",
    "print 'b) The maximum bit rate for NRZ',round(fb,5),'GHz'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example 4 : pg 924"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Dispersion is 1.0 ns/km\n",
      "Total rise time is 5.0 ns\n"
     ]
    }
   ],
   "source": [
    " \n",
    "# page no 924\n",
    "# prob no 25_4\n",
    "#calculate the total rise time and dispersion\n",
    "#given\n",
    "Bl=500.;#in MHz-km\n",
    "L=5.;#in km\n",
    "#calculations and results\n",
    "# using the bandwidth-distance product formula dispersion is given as\n",
    "D=500/Bl;\n",
    "print 'Dispersion is',D,'ns/km'\n",
    "# Total rise time is given as\n",
    "T_rt= D*L;\n",
    "print 'Total rise time is',T_rt,'ns'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example 5 : pg 924"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The maximum acceptable dispersion is 0.139 ns/km\n",
      "The bandwidth-distance product is 3608.439 MHz-km\n"
     ]
    }
   ],
   "source": [
    " \n",
    "# page no 924\n",
    "# prob no 25_5\n",
    "#calculate the max acceptable dispersion and bandwidth-distance product\n",
    "#given\n",
    "from math import sqrt\n",
    "T_Rrx=3.*10**-9;\n",
    "T_Rtx=2.*10**-9;\n",
    "fb=100.*10**6;#in bps\n",
    "L=25;#in km\n",
    "#calculations and results\n",
    "T_RT = 1/(2*fb)\n",
    "# we have to compute rise time therefore\n",
    "T_rf= sqrt(T_RT**2 - T_Rtx**2 - T_Rrx**2)\n",
    "# dispersion per km is\n",
    "D= T_rf/L;\n",
    "print 'The maximum acceptable dispersion is',round(D/10**-9,3),'ns/km'\n",
    "# using the bandwidth-distance product\n",
    "Bl=500/D;\n",
    "print 'The bandwidth-distance product is',round(Bl*10**-9,3),'MHz-km'"
   ]
  }
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