Foundations — Photonic and optical interconnects

6.5.15 · D1 · Hardware › Advanced & Emerging Architectures › Photonic and optical interconnects

Parent note padhne se pehle, tumhe har woh symbol khud se banana hai jo woh tumhare saamne phenkta hai. Neeche, har ek ko milega: plain words → picture → topic ko isko kyun chahiye, is order mein ki har ek uske upar waale par tikaa ho.

1. Bits, electrons, aur photons — woh teen "cheezein" jo move ho rahi hain

Topic ko isko kyun chahiye: poora chapter "bits electrons par sawari karte hain" (copper) aur "bits photons par sawari karte hain" (photonics) ke beech ek contest hai. Tum winner ko judge nahi kar sakte bina dono contestants ko jaane. Dekho Copper interconnects and RC delay.

2. Length $L$ aur "per-length" quantities ka idea

Kai electrical properties per metre quote ki jaati hain aur phir $L$ se multiply ki jaati hain:

"Per-length" kyun? Ek lamba wire sirf kai choti wires ka ek line mein sequence hai. Har chota piece apna resistance add karta hai (woh series mein stack hote hain, $R$ badhta hai) aur charge store karne ke liye apni thodi surface ($C$ badhta hai). Toh dono $R$ aur $C$, $L$ ke saath badhte hain — yeh yaad rakho, yeh $L^2$ wall ka beej hai.

3. "$\times$" ke roop mein multiplication aur symbol $\tau$

Per-length forms substitute karne par: $\tau =RC=(rL)(cL)=rc{L}^2$

Square kyun matter karta hai: ek $L$ $R$ se aaya, ek $L$ $C$ se aaya. Do cheezein jo dono length ke saath badhti hain, multiply hone par, length-squared deti hain. Wire double karo → chaar baar delay. Yahi woh wall hai jise photonics dodge karta hai.

4. Speed of light $c$, refractive index $n$, aur $v=c/n$

Length $L$ ki waveguide se light ka transit time phir hai $t=\frac{L}{v}=\frac{nL}{c}.$

Topic ko isko kyun chahiye: notice karo $t$, $L$ ke saath first power mein badhta hai — linear, squared nahi. Yeh akela fact, copper ke $L^2$ se contrast mein, pure topic ki physics ka dil hai. Full detail Refractive index and speed of light in media mein hai.

5. Wavelength $\lambda$ aur light ke "colours"

6. Bit rate $B$, channel count $N$, aur sum $B_{\text{total}}=NB$

Kyunki independent colours ek doosre se churaaye bina add hote hain: $B_{\text{total}}=N\times B.$

Ek sum kyun aur max kyun nahi? Ek shared electrical bus mein, streams turns lete hain (woh time divide karte hain), toh zyaada streams add up nahi hote. Independent colours simultaneously chalte hain, toh unki rates add hoti hain. Example: $N=40$ colours at $B=25\text{Gb/s}$ dete hain $B_{\text{total}}=1000\text{Gb/s}=1\text{Tb/s}$ ek line par.

7. Fields, phase $\Delta \varphi$, aur symbol $e^{i\theta }$

Yeh teen parent mein modulator maths ko unlock karte hain.

8. Power $P$, energy-per-bit $E_{\text{bit}}$, aur current $I=R_{\lambda }P$

Yeh foundations topic ko kaise feed karte hain

Equipment checklist

Right side hide karo aur khud test karo — agar koi line tumhe rok de, uska section upar se dobara padho.