panalty:eye openining(in DB)

[aasif bashir dar]

i wish to ask the significance of this parameter in the after simulation BER analyzer analysis.i also saw the graph wich have nagative values of panalty ,,, what does the graph mean???

responses will be appreciated

with regards

[aasif bashir dar]

hi all,
i request you all to explain this graph to me , if any one can understand it properly.
please explain only the attached graph .

responses will be welcomed,

with regards

[aasif bashir dar]

graph is here

Attachments:

1. 

   penality.png
   

[ZULKARNAIN]

hi AASif …
in one of the post in optiwave it was discussed by alistu .Hope it will help you..
Power penalty means when a parameter in the system changes and results in degradation of the eye-opening, the amount of power that compensates for the degradation is called “power penalty”. For this, you would have to do the simulation before the change in that certain parameter (implementation1), and then after that change in that parameter (implementation2). Then you should increase the power in implementation2 to the point where eye diagram becomes the same as implementation1. The value of the power you have added is the power penalty.
For your reference i am attaching the link.
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjPqZeBjLTLAhXCj44KHWiZAYAQFggnMAA&url=http%3A%2F%2Foptiwave.com%2Fforums%2Ftopic%2Feye-opening-penality%2F&usg=AFQjCNGZaOo5sTVethkp0YUPfH5UuLrvDQ&sig2=OVldjRBuWWqQQKkJR_ALLA

[ZULKARNAIN]

As for as graph is concerned which you uploaded, i am not able to understand it.
regards

[aasif bashir dar]

hi
zulkarnain

i know every bit of basic theory of eye opening penalty, and i already had dicussed that in my previous posts.

i want to the explanation of the graph which i have uploaded here , very badly.

still thanks for the reply

with regards

[umer syed]

hlo aasif bashir..
the X axis in the graph are not defined..Is it penalty versus frequency..if it iz…iz the frequency in Ghz or in Mhz

[aasif bashir dar]

hi umer,

i my self put that unspecified as it can be any parameter,

for convence i will mention it here that it is the channel length(taken in the loop nO)

with regards

[umer syed]

hi aasif
if the parameter is channel length then the graph is wrong one..
The expected power penalty due to dispersion is given by a parabolic function of the ratio of symbol rate to dispersion limited
bandwidth times a coefficient, “c,” which relates to the roll-off of a raised cosine receiver response. If we wish to examine
this in terms of dispersion power penalty versus total dispersion. First we need to know the spectral width of the laser.
For multilongitudinal mode (MLM) laser, usually Fabry-Perot (FP) type, the spectral width is the root-mean-square spectral
width, and for single-longitudinal mode (SLM) lasers, usually distributed feedback (DFB) lasers, the spectral width is the
width at the 20 dB down points divided by 6.07. This is the Gaussian spectral width at the 20 dB down point.

with regards

[aasif bashir dar]

hi umer syed,

the graph is not wrong,it is the simulated result of .osd file.

i only mentioned of interpretting the graph , i didnt mentioned to make comment of erongness or rightness of graph.thanks for reply

with regards

[umer syed]

hi asif…
sry i misinterpretted it…
actually negative power penalties do occurs in OOFDM transmission signals…..the resulting negative power penalty is independentof both cyclic prefix and signal modulation format. Furthermore the negative power penalty is controllable by applying adaptive modulation and/or variation in DMLoperating condition.The negative power penalty is a direct result of the negative dispersion fiber-enabled compensation of the DML positive transient frequency chirp.
The physical mechanisms behind the negative power
penalty can be explained as follows: The optical-domain OOFDM signal phase cannot be preserved perfectly in the electrical domain due to subcarrier intermixing upon square-law photon detection in the receiver. As the unwanted subcarrier intermixing effect decreases with decreasing the optical phase at the input facet of the PIN, thus the MetroCor fiber-induced reduction in the DML-modulated
OOFDM signal phase gives rise to the observed negative power penalty. Whilst, for coherent OOFDM MetroCor transmission systems, the OOFDM signal phase can be preserved perfectly in the electrical domain, no negative power penalties exist.
The above physical explanations imply that a partial elimination of the subcarrier intermixing effect should be able to increase the obtained power penalty and simultaneously extend the transmission distance over which the minimum power penalty is observed.
i have also attached a pdf file..
hope this will help

with regards

Attachments:

1. 12311.pdf

[aasif bashir dar]

hi syed
i still did not clarification regarding the graph. i want you to be to the point that i need the clarifification or explaination of graph.

futher more the pdf you have upload provides the provision of the nagative penality… i want its significance.

hope some one will this confusion soon..

with regards

[Ranjeet Kumar]

Hi,
Sir, the above graph being plotted doesn’t have clearance regarding axes :horizontal axis vs vertical axis. Please name both axes.

[umer syed]

hi ranjeetkumar…
it is actually power penalty in dB versus transmission length in kms…

[aasif bashir dar]

yeah umar, you are right about axis, but i need explanation.

with regards

[Aabid Baba]

Hello asif ,
As discussed in recent post about eye penalty that eye penalty is somehow related Power penalty which means when a parameter in the system changes and results in degradation of the eye-opening, the amount of power that compensates for the degradation is called “power penalty”.
As far as your graph is concerned , you have not mentioned what are you plotting and against what , so it is a bit difficult to explain the graph.
regards

[aasif bashir dar]

hi all,
please i am well aware of the theoretical aspects that;;;
as far as the graph is concerned the x-axis the any parameter(e.g link lengthh) and the y-axis is the panality in the decibal scale.

now can you please explain the graph to me in detailedc mannure.

with regards

[Aabid Baba]

Hello asif,
Here i would rather take up to the theoretical aspect of eye penalty and infer information from the graph itself.
Now as you mentioned that x-axis is the length of the link and y-axis the penalty , now what i infer from the graph is that with length of the link increasing , more losses are associated with transmission because the length has increased here and to compensate those losses , the requirement of the parameter (say power) increases linearly and then suddenly the requirement drops. Now since you are implementing the system you might be knowing the reason here. Please do explain it if you resolve it.

Regards

[umer syed]

hi aasif sir,
i suggest you please also vist the other post of same problem;

nagative eye opening penality

with regards

[aasif bashir dar]

hi umar,
yeah i was asking for the same explanation, i got slight idea what it could be. but once i will be sure about that, i would like to share that here also.

now i hope no body will share THEORETICAL aspects of panlty for eye opening and every one will focus on the graph
with regards

[aasif bashir dar]

hi aabid,
more losses are associated with transmission because the length has increased hand to compensate those losses , the requirement of the parameter (say power) increases linearly and then suddenly the requirement drops..

i now think that nagative penalty(db) means that we should decrease power so as to reduce the effect of eye closure.

with regards

[Aabid Baba]

Hello asif,
Well for my liking, The penalty should not decrease so abruptly and there must be some logic why the response is such. I would suggest you to simulate a simple and basic design and keep length very small and check for the graph and next time you simulate , increase the length by 5Kms and check for the graph again. repeating it , see where exactly does the curve fall.. May be that would help our understanding.

Regards

[aasif bashir dar]

hi all,
i my self thinks now that penalty for eye opening can be both positive and nagative

case1:positive penalty: in this situation we require to compenate the losses of any parameter in design such as length.

case2:nagative penalty: there may be case where excess of power may create nonlinearities and other thermal noise at reciver end,

hence we should reduce the power, threfoe the penality is nagative.>>>>>>>>>>>>.

with reagards

[FAYIQA NAQSHBANDI]

Hi all,
In my opinion power penalty can’t be negative because :
1. you say it the power required to compensate losses in the fiber link or any other parameter in the system due to which the loss is caused.
2. there is no logic to apply negative power. To my understanding it must always be positive because the theory suggests so But yeah i can’t be sure shot here.
Opinions and logics do vary.
Anyways, thanks and regards

[Aabid Baba]

Hello fayiqa,
I agree with your response. You have made an important and a valid point regarding the negative penalty. you have justified your response and i believe that power penalty can’t be negative ( taking your opinion in consideration). I also believe that there what for do we require negative power if there are no losses at all.
regards

[umer syed]

yeah great explanation by asif bashir dar

[aasif bashir dar]

you are welcome

a conclusive and coherent discussions are always welcomed

[Naazira Badar]

Hi All.
I think Aabid has rightly explained the negative penalty. In that region, the extra power needed for compensation of performance degradation is not needed.

Regards.

[Jojo Mathew]

Hello Asif,
Your graph is not complete. Untill and unless you dont mention tthe dependent and the independent variables ,solving your query will be difficult. Please upload the graph that clearly shows all the parameters.
Regards.

[Ranjeet Kumar]

thank you umar sir,
i was confused about horizontal axis.

[aasif bashir dar]

hi jjo mathew,
taking about completeness of graph,
well it had been already already discussed in reply #32166

well i already had pointed my view about the significance of the both nagative and positve panelity in above replies….

i suggest you to go through them, and then discuss what can you point out from them here.(you thought about the signifance of graph may vary)
that is why we are discussing it here and want to have some conclusive remarks about the query.

with regards

[Tanveer]

thank you all especially aasif bashir and umer syed for such so much valuable information about the graphs and their different aspects…
hope this healthy discussion will be helpful for the forum members if the future,,,,
with regards
tanveer

[SAHIL SINGH]

hi all,

Nice discussion and thanks aasif bashir dar for such valuable information… Such valuable logics are indeed welcome on the forum

Regards

Sahil Singh

[Author]

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