sequence lenght effects on optical systems

[Ashu verma]

Greetings everyone
I have read a article and found this
optical communication system, generally the pseudorandom bit sequence (PRBS) are used as data signals for modulating the DWDM channels. The longer word length (WL) develops the more bit patterns in PRBS. The selection of number of bits in PRBS directly affects the system performance because longer the WL means easy to evaluate the performance, on the other hand, shorter the WL means condense the calculation time and the memory requirements. Therefore, it is essential to illuminate how long the WL is vital to estimate the nonlinear crosstalk’s precisely.
The SRS crosstalk can be increased due to the presence of successive number of “1” bits, which is directly proportional to the WL as it determines the maximum possible length of the successive ‘1’ bits. That means longer the WL, maximum the probability of occurrence in successive “1s”.

found this paper very interesting which defines effect of world length on non linearities.i am little confused now about the dependence of sl on system pergormance.Take a look at thishttp://www.sciencedirect.com/science/article/pii/S106852001300059X
This explaines SRS effect on system performance with wL .As WL increase there is increase in non linear effects

Now i need to know ,is this effect in all the systems or only in system where hoa is used or raman fiber is thrre?
Regards

[alistu]

Hi Sam,

I think the aforementioned effect very much depends on the type of the system one is using. For example, in an OFDM scheme, ones and zeros are first coded and then IDFT is taken from them. So their form is completely changed when they enter the line and it’s not anymore like ones enter more power to the line than zeros. So while the effects might be true and great enough to be measured in some cases, some systems might be less prone to that and therefore it wouldn’t be accurate to generalize this. As for the systems without HOAs, one must do some research to get to a conclusion for sure, while it again depends on the whole system settings and modulation schemes used.

Regards

[Ashu verma]

Thank you Alistu,now i am confused that in case of simple dwdm system results change when i change the SL without using any HOA.I think raman fiber cause this type of effects? If raman cause this then this also effects ither systems too where fsmf used.I got your point about ofdm and i think its correct.Damian explaines this better ,because as far as this paper is concerend ,it is also implemented in optisystem as i have full dessertation of author .Alistu how to now conclude this factor if i have explain this ?

[alistu]

I believe there is no reason for confusion, since the paper does not mention that the effect happens only in case hyper optical amplifiers are used. The paper just studies the case with HOAs, and it doesn’t mean it cannot occur for any other system. As I pointed out, it cannot be genaralized based on some observations in some specific systems.

[Ashu verma]

Alistu ,i have seen this in otdm systems when i practised ,ocdma systems ,wdm systems then how would i get to know that which specific does not vary with SL?so know i go for that wl does not effect system performance but in some specific systems it effects ? I am not getting the accurate point.however i agree that auther havnt mention that it can only happen system which include HOA

[alistu]

As far as my experience can tell, this effect cannot be seen in OFDM systems in a way that you can certainly attribute it to the word length. So I’m guessing (out of my own experience, without being sure) unless you increase WL by a very great amount, the effect is not that much.

I think for every system one can increase the WL and see if they can observe any PATTERNED changes. So I suggest that you do this if the accuracy of results from a system are very important. Nevertheless, simulations that can be repeated for systems of the same type by anyone and yet give more or less the same result would be scientific and reliable.

[Ashu verma]

Thank you alistu,i will try to analyze this effect for shorter as well as longer sl and get back if doubt is there.besides it, it would be great to work on this topic as it relates to non linear effects directly.

[Author]

Posts