path: root/Optical_Fiber_Communication_by_A_Kalavar/6-Optical_Sources.ipynb

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 {
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	   "source": [
       "# Chapter 6: Optical Sources"
	   ]
	},
{
		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.14_1: Single_longitudinal_mode.sce"
		   ]
		  },
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"// Example 6.14.1  page 6.42\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"// This is example does not consist of any numerical computation\n",
"\n",
"printf('\nQuestion - What do you understand by single longitudinal mode laser or SLM? ')\n",
"printf('\nAnswer - \nIn laser operation optical gain alone is not sufficient for laser operation but a minimum amount of gain is also necessary.\nThis gain can be achieved when laser is pumped above threshold level.\nIn simplest laser structure we have p-n junction.Active layer is sandwitched between p and n type layers of higher bandgap material. Such broad area semiconductor laser need high threshold current and light confinement becomes difficult.\nGain guided semiconductor laser limit the current injection over a narrow stripe thus overcome the problem of light confinement.They are also called stripe geometry lasers.\nIn index guided laser an in index step is introduced to form waveguide.\nIn buried heterostructure laser the active region in buried by layers of lower refractive indices.\nWhen width and thickness of the active layer is controlled, light can be made to emerge in a single spatial mode, but the problem arises when such lasers oscillate in many longitudinal modes in Fabry Perot cavity.\nThe spectral width obtained is about 2-4 nm which can be tolerated for 1.3 micrometer operation, but for systems operating near 1.55 micrometer at higher bit rates such multimode lasers can not be used. At such times laser which emit light in a single longitudnal mode are required to give higher bit rates than 1 Gb/s. They are called Single Longitudinal Mode (SLM) lasers.');"
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		   "metadata": {},
		   "source": [
			"## Example 6.21_1: Determine_total_recombination_lifetime_and_internally_generated_power_emission.sce"
		   ]
		  },
  {
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"source": [
"// Example 6.21.1  page 6.59\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"tr=50;      //radiative recombination lifetime\n",
"tnr=85;     //non-radiative recombination lifetime\n",
"h=6.624d-34;  //plank's constant\n",
"c=3d8;      //speed of light\n",
"q=1.6d-19;  //charge of electron\n",
"i=35d-3;    //current\n",
"lamda=0.85d-6;      //wavelength\n",
"\n",
"t=tr*tnr/(tr+tnr);          //computing total recombination time\n",
"eta=t/tr;                   //computing internal quantum efficiency\n",
"Pint=eta*h*c*i/(q*lamda);   //computing internally generated power\n",
"Pint=Pint*10^3\n",
"\n",
"printf('\nTotal recombinaiton time is %.2f ns.\nInternal quantum efficiency is %.3f.\nInternally generated power is %.1f mW.',t,eta,Pint);\n",
"\n",
"//answer in the book for Internal quantum efficiency is 0.629, deviation of 0.001.\n",
"//answer in the book for Internally generated power is 32.16 mW, deviation of 0.04 mW."
   ]
   }
,
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		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.21_2: EX6_21_2.sce"
		   ]
		  },
  {
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"source": [
"// Example 6.21.2  page 6.59\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"tr=30;      //radiative recombination lifetime\n",
"tnr=100;     //non-radiative recombination lifetime\n",
"h=6.624d-34;  //plank's constant\n",
"c=3d8;      //speed of light\n",
"q=1.6d-19;  //charge of electron\n",
"i=40d-3;    //current\n",
"lamda=1310d-9;      //wavelength\n",
"\n",
"t=tr*tnr/(tr+tnr);          //computing total recombination time\n",
"eta=t/tr;                   //computing internal quantum efficiency\n",
"Pint=eta*h*c*i/(q*lamda);   //computing internally generated power\n",
"Pint=Pint*10^3\n",
"\n",
"printf('\nTotal recombinaiton time is %.2f ns.\nInternal quantum efficiency is %.3f.\nInternally generated power is %.2f mW.',t,eta,Pint);\n",
"\n",
"//answer in the book for Total recombinaiton time is 23.07 ns, deviation of 0.01ns."
   ]
   }
,
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		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.21_3: Determine_total_recombination_lifetime_and_internally_generated_power.sce"
		   ]
		  },
  {
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	   "outputs": [],
"source": [
"// Example 6.21.3  page 6.60\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"tr=50;      //radiative recombination lifetime\n",
"tnr=110;     //non-radiative recombination lifetime\n",
"h=6.624d-34;  //plank's constant\n",
"c=3d8;      //speed of light\n",
"q=1.6d-19;  //charge of electron\n",
"i=40d-3;    //current\n",
"lamda=0.87d-6;      //wavelength\n",
"\n",
"t=tr*tnr/(tr+tnr);          //computing total recombination time\n",
"eta=t/tr;                   //computing internal quantum efficiency\n",
"Pint=eta*h*c*i/(q*lamda);   //computing internally generated power\n",
"Pint=Pint*10^3\n",
"\n",
"printf('\nTotal recombinaiton time is %.2f ns.\nInternal quantum efficiency is %.4f.\nInternally generated power is %.2f mW.',t,eta,Pint);\n",
"\n",
"//answers in the book with slight deviaitons\n",
"//Total recombinaiton time is 34.37 ns, deviation of 0.01ns.\n",
"//Internal quantum efficiency is 0.6874, deviaiton of 0.0001.\n",
"//Internally generated power is 39.24 mW, deviation of 0.02mW."
   ]
   }
,
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		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.22_1: Determine_optical_power.sce"
		   ]
		  },
  {
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"// Example 6.22.1  page 6.68\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"f1=10d6;    //frequency\n",
"f2=100d6\n",
"t=4d-9;\n",
"Pdc=280d-6;     //optincal output power\n",
"\n",
"w1=2*%pi*f1;    //computing omega\n",
"Pout1=Pdc*10^6/(sqrt(1+(w1*t)^2));      //computing output power\n",
"\n",
"w2=2*%pi*f2;    //computing omega\n",
"Pout2=Pdc*10^6/(sqrt(1+(w2*t)^2));      //computing output power\n",
"\n",
"printf('Ouput power at 10 MHz is %.2f microwatt.\nOuput power at 100 MHz is %.2f microwatt.\nConclusion when device is drive at higher frequency the optical power reduces.\nNOTE - calculation error. In the book square term in the denominater is not taken.',Pout1,Pout2);\n",
"\n",
"BWopt = sqrt(3)/(2*%pi*t);\n",
"BWelec = BWopt/sqrt(2);\n",
"BWopt=BWopt*10^-6;\n",
"BWelec=BWelec*10^-6;\n",
"\n",
"printf('\n3 dB optical power is %.2f MHz.\n3 dB electrical power is %.2f MHz.',BWopt,BWelec);\n",
"\n",
"\n",
"//calculation error. In the book square term in the denominater is not taken.\n",
"//answers in the book - \n",
"//Ouput power at 10 MHz is 228.7 microwatt.(incorrect)\n",
"//Ouput power at 100 MHz is 175 microwatt.(incorrect)\n",
"//3 dB optical power is 68.8 MHz, deviation of 0.12\n",
"//3 dB electrical power is 48.79 MHz, deviation of 0.06 "
   ]
   }
,
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		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.22_2: To_calculate_emitted_optical_power_as_percent_of_internal_optical_power.sce"
		   ]
		  },
  {
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"source": [
"// Example 6.22.2  page 6.69\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"n1=3.5;  //refractive index\n",
"n=1;    //refractive index of air\n",
"F=0.69; //transmission factor\n",
"\n",
"eta = 100*(n1*(n1+1)^2)^-1;     //computing eta\n",
"\n",
"printf('\neta external is %.1f percent i.e. small fraction of intrnally generated opticalpower is emitted from the device.',eta);\n",
"printf('\n\n OR we can also arrive at solution,\n');\n",
"\n",
"r= 100*F*n^2/(4*n1^2);      //computing ratio of Popt/Pint\n",
"\n",
"printf('\n Popt/Pint is %.1f percent',r);\n",
"\n",
"printf('\nNOTE - printing mistake at final answer.\nThey have printed 40 percent it should be 1.4 percent');"
   ]
   }
,
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		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.22_3: Find_operating_lifetime.sce"
		   ]
		  },
  {
"cell_type": "code",
	   "execution_count": null,
	   "metadata": {
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"source": [
"// Example 6.22.3  page 6.73\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"beta0=1.85d7;\n",
"T=293;      //temperature\n",
"k=1.38d-23; //Boltzman constant\n",
"Ea=0.9*1.6d-19;\n",
"theta=0.65; //thershold\n",
"\n",
"betar=beta0*%e^(-Ea/(k*T));\n",
"t=-log(theta)/betar;\n",
"\n",
"printf('\nDegradation rate is %.2e per hour.\nOperating lifetime is %.1e hour.',betar,t);\n",
"\n",
"//answer in the book for Degradation rate is 6.4e-09 per hour, deviation of 0.08e-9\n",
"//answer in the book for Operating lifetime is 6.7e+07 hour, deviaiton of 0.1e1"
   ]
   }
,
{
		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.3_1: Find_operating_wavelength.sce"
		   ]
		  },
  {
"cell_type": "code",
	   "execution_count": null,
	   "metadata": {
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"source": [
"// Example 6.3.1  page 6.7\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"x=0.07;\n",
"Eg=1.424+1.266*x+0.266*x^2;\n",
"lamda=1.24/Eg;      //computing wavelength\n",
"printf('\nWavlength is %.3f micrometer.',lamda);"
   ]
   }
,
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		   "cell_type": "markdown",
		   "metadata": {},
		   "source": [
			"## Example 6.3_2: Find_out_number_of_longitudinal_modes_and_frequency_separation.sce"
		   ]
		  },
  {
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	   "execution_count": null,
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"source": [
"// Example 6.3.2  page 6.12\n",
"\n",
"clc;\n",
"clear;\n",
"\n",
"n=1.7;      //refractive index\n",
"L=5d-2;     //distance between mirror\n",
"c=3d8;      //speed of light\n",
"lamda=0.45d-6;  //wavelength\n",
"\n",
"k=2*n*L/lamda;      //computing number of modes\n",
"delf=c/(2*n*L);     //computing mode separation\n",
"delf=delf*10^-9;\n",
"\n",
"printf('\nNumber of modes are %.2e.\nFrequency separation is %.2f GHz.',k,delf);\n",
""
   ]
   }
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