Login

Search the forums now!

Welcome, Guest. Please login or register.

November 01, 2025, 08:47:34 am
Pages: [1]   Go Down

Author Topic: photonics question  (Read 1072 times)  Share 

0 Members and 2 Guests are viewing this topic.

Shark 774

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 261
  • Respect: +1
photonics question
« on: May 23, 2011, 06:18:53 pm »
0
I just have no idea with the attached question... I picked D, which is wrong. Can somebody explain that correct answer(s)? I am not confident at all with photonic communication systems, any basic tips would be greatly appreciated, cheers.

Logged

Vincezor

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 332
  • Respect: +11
  • School: Glen Waverley Secondary College
  • School Grad Year: 2011
Re: photonics question
« Reply #1 on: May 23, 2011, 07:24:57 pm »
0
Quote from: Shark 774 on May 23, 2011, 06:18:53 pm
I just have no idea with the attached question... I picked D, which is wrong. Can somebody explain that correct answer(s)? I am not confident at all with photonic communication systems, any basic tips would be greatly appreciated, cheers.



If anything, it wouldn't be D. this is because at point P the signal has already been modulated (D could be an example of input signal)

I don't quite understand what they mean by 'single-frequency signal' but I'll assume this won't have anything to do with the Y-axis values (Therefore not C)

As point P is just before it is going to get demodulated, I believe it is still a pulsating light that is proportional to the information signal.

I'm going to go with A, but only because I don't understand what they mean by 'amplitude of light wave', and 'light intensity' makes more sense to me :S
Logged
2010: Systems Engineering 44            

2011: Specialist Mathematics 37 | Mathematical Methods (CAS) 43 | Physics 39 | Chemistry 42 | English 41

ATAR: 98.50

2012: Eng/Law @ Monash

xZero

  • Victorian
  • Forum Leader
  • ****
  • Posts: 898
  • Respect: +68
Re: photonics question
« Reply #2 on: May 23, 2011, 08:28:48 pm »
0
I'm quite sure that the intensity of light is somehow proportional to the amplitude of the light, so I'm guessing A and B
Logged
2009: Chinese SLA
2010: English, Maths method[45,A+ A+ A+], Specialist maths[44,A+,A,A+], Physics[40,A,A+,A+], Psychology Atar:94.75
2011-2015: Bachelor of Aerospace Engineering/Science @ Monash

Methods/Spesh/Physics tuition

luffy

  • Victorian
  • Forum Leader
  • ****
  • Posts: 520
  • Respect: +23
  • School Grad Year: 2011
Re: photonics question
« Reply #3 on: May 23, 2011, 08:37:45 pm »
0
Quote from: xZero on May 23, 2011, 08:28:48 pm
I'm quite sure that the intensity of light is somehow proportional to the amplitude of the light, so I'm guessing A and B

The question does say "one or more" in bold... Therefore, they are probably expecting two answers. Thus, it would be A & B.
Logged

Shark 774

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 261
  • Respect: +1
Re: photonics question
« Reply #4 on: May 23, 2011, 10:00:22 pm »
0
The answer given was B and D and I think I just figured it out:
It can't be A, because you can't have negative light intensity. It wouldn't be C because there is no modulation in the wave. D could work because there is modulation and you CAN have a negative amplitude and B could work because there is modulation and no negative values. Or can you also not have a negative amplitude of a light wave? What do you reckon?
« Last Edit: May 23, 2011, 10:19:32 pm by Shark 774 »
Logged

Vincezor

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 332
  • Respect: +11
  • School: Glen Waverley Secondary College
  • School Grad Year: 2011
Re: photonics question
« Reply #5 on: May 23, 2011, 11:30:39 pm »
0
Quote from: Shark 774 on May 23, 2011, 10:00:22 pm
The answer given was B and D and I think I just figured it out:
It can't be A, because you can't have negative light intensity.

*Facepalm* wasn't thinking straight. My bad!

I guess D could work, but I just keep thinking that the carrier wave must have a higher frequency than the input signal. Then again, we aren't given the characteristic of this input so thus it is possible that it is correct... I guesss..
Logged
2010: Systems Engineering 44            

2011: Specialist Mathematics 37 | Mathematical Methods (CAS) 43 | Physics 39 | Chemistry 42 | English 41

ATAR: 98.50

2012: Eng/Law @ Monash

Shark 774

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 261
  • Respect: +1
Re: photonics question
« Reply #6 on: May 24, 2011, 08:11:43 am »
0
Quote from: Vincezor on May 23, 2011, 11:30:39 pm
Quote from: Shark 774 on May 23, 2011, 10:00:22 pm
The answer given was B and D and I think I just figured it out:
It can't be A, because you can't have negative light intensity.

*Facepalm* wasn't thinking straight. My bad!

I guess D could work, but I just keep thinking that the carrier wave must have a higher frequency than the input signal. Then again, we aren't given the characteristic of this input so thus it is possible that it is correct... I guesss..

Yeah we weren't given the characteristics, and there is no scale on the time axis so there is nothing to say that it isn't high frequency. Thanks for your response.
Logged
Pages: [1]   Go Up