Question

please I am really confused what is the laser pulse and what is the pulse width or the resolution and what does it mean , and what the difference physically between picoseconds and femto seconds pulse width if i inject them to fiber which i want to measure the backscattered light along this fiber

Answer 1

well.. a laser pulse is a laser light which is turned on only for a very small fraction of time, unlike the laser BEAM..

so the pulse width is the time for which the laser is switched on, and so the laser light will be that much

for example

if i have a pulse width of 1 nano second.. then you know light travels 3 X 10^8 m/s .. so in one nano second it woudl have travelled .3m, hence, when i say a laser light is 1 nano second pulse width long, it means its .3 m long..
is that what you wanteD?

Answer 2

pico - 10^ -12

femto (fermi) 10^-15

Answer 3

so after this 0.3m the pulse disappear ? for example now I am using pulsed laser with pulse width 60 pico seconds , and repetition rate of 20 MHz , and I am using some lenses and mirrors to focus the light into a 1 meter fiber cable (which i want then to measure the back scattered light) . can you please explain to me how the pulse is travelling and what is the effect of pico second pulse width. what if I am using femto second laser , how this effect the resolution of the measurement !? Thank you :)

Answer 4

omg.. i think you require a proper engineering answer :P.. m not much into optical fibre communication to be able to tell you the differences :-/ sorry