bit rate

[faysal sarker]

what is the meaning of the two bit rate at the given attachment.and which one is the data transfer rate?

[Dr Rk Sethi]

1st one is the Global data rate and second is the PRBS generator data rate.
The data transfer rate is given by the PRBS generated data rate.

[Ravil]

Hi faysal sarker,

As it has been noticed correctly by Rk Sethi, the first bit rate (from Layout 1 Parameters table) shows data transmission rate through your whole system (from output of your transmitter to the input of your receiver). The second table shows the bit rate of data generated by information source and launched to your transmission system. These two bit rates are differ due to implementation of different multiplexing and modulating schemes as well as the signal coding.

[Abhishek Shrama]

Hi ,I have also a Doubt,In case if we do not use script mode in PRBS and enter data rate in PRBS at normal mode then on which data rate system perform ? Can we disable a Bit rate in global parameter window.Can we put iteration on Data rate in same layout?

[Ravil]

Dear Abhishek,

In my opinion, script affects the Global data rate first. As I indicated below, this data rate can be calculated through ‘the time window which, in its turn, is a sequence length over the generated bit rate’. I don’t think that you can disable the Global data rate since it is used for the calculation. However, I am not sure if that option is available in the last versions of OptiSystem. Not sure what you mean by ‘iteration in data rate’…

[Ashu verma]

Well said RK sethi and Ravil.Abhishek if you use script mode then it use the data rate of system.If you use normal then this is the data rate of PRBS but system data rate is, as in global parameter window.Am i right ravil and Sethi ?

[Ravil]

Yes, Sam Sung. The system data rate is in the Global parameter window and the data transfer rate is given by the PRBS.

[faysal sarker]

please give me some source from where i can get explicit information regarding Global data rate and the PRBS generator data rate.

[alistu]

Hi Faysal,
Here are the links to some of the sources you might find useful:

OptiSystem – Getting Started

https://cdn.optiwave.com/wp-content/uploads/2015/03/15145539/OptiSystem_Tutorials_Volume_1.pdf?d20331

Hope they’re useful for you.

cheers

[Ravil]

Hi faysal,

I am pretty sure that the information you are requesting can be found in OptiSystem manuals. The example of Global data rate usage is shown in Lesson 6 (if I am not mistaken) online. You can also check the optsystem documents for the information about global parameter window optisystem>documents>global parameter. In general, you can calculate the Global data rate through the time window which, in its turn, is a sequence length over the generated bit rate.

[LALIT VERMA]

By this discussion can i interpret that while design a system global parameter bit rate can differ from prbs generator specially for sac ocdma system.

[Ravil]

Hi Lalit,

Yes, you understood it right. These two parameters can be different.

[Taiwo Ambali Abiola]

I think the explanation is still the same. Any parameter on a component or “module” run on a “script” automatically takes value from the global parameter. However, when such parameter is set on “normal”, it takes the manual value set for it. Read more about it in the documentation. When a module parameter is set on “script” and the value there is pointing to a parameter available on “global parameter” such as (bit rate, sequence length, time window, sample per bit and etc), it automatically take the value from the “global parameter”.

A bit rate is the one you set on the PRBS either by accessing global parameter bit rate or through “normal” setting. it is possible to be different from the global parameter bit rate if you change it to “normal” and you assign a value. I hope is a bit clear?

[K. Esakki Muthu]

Ravil,
if you keep global bit rate and the PRBS bit rate then we can get proper results i think. that should be same for getting proper eye diagram and BER? Am I right?

[alistu]

Hi Esakkimutho,
I don’t think that’s necessarily correct. The bit rate applied to the implemented system is the one defined in the PRBS, and not the one in global parameters. We had a discussion in which there was another bit rate defined for PRBS, which you can read in here:

Sac ocdma with MD code

[K. Esakki Muthu]

Dear Alistu,
I have tried this personally, if we keep Global bit rate and PRBS bit rate different, then the results are different.

[alistu]

Dear Esakkimuthu, Very carefully I used the word “not necessarily” about what you have mentioned in your previous comment. The reason for what you have experienced is that the global bit rate defines some other global parameters and in some cases, this might cause problem. I have also experienced such cases, but in many cases it was ok.

[Taiwo Ambali Abiola]

As for SAC-OCDMA, I think it is a function of how many transmitting points you have. For instance, if you have 4 transmitters, and each PRBS is running with 10Gbps bit rate, the overall data rate is 10X4 which is 40Gbps. I stand to be corrected if I have made mistake please.

[Ashu verma]

Hello Taiwo
You explained very well about the confusion regarding Bit rate for script mode and normal mode.Also the concept of total bit rate after multiplexing of no. of channels is right explained by you is right.Ravil gave some good points and links given by alisthu are very important for any beginner to use optisystem.

[Taiwo Ambali Abiola]

Really! Thanks alot Sam sung

[gaganpreet Kaur]

First one is the bit rate which goberns the complete system while pseudi random geebrator bit rate specifies the bit rate to b used by the transmitter.this bit rate is rate of input sequence generated which will modulate the laser source.

[Gurpreet Kaur]

i hve a query related to same that if my prbs bit rate is 4gbps and i am using 3 users, then the global parameter bit rate should be set to 12gbps?
and at the receiver side if i am using low pass bessel filter for single user then which bit rate is to be used for setting its cut off frequency? as in filter it is in script form 0.75*bit rate. so i shall simulate with prbs data rate or the global one?

[alistu]

Hi Gurpreet, What you must do is to set the bit rate in global parameters to the bit rate of each user, which is 4 Gbps in your case. Then be careful that random sequence bit generators you use have their bit rates determined in script mode and the script should refer to the global bit rate, which it is on default.

[alistu]

You have asked about the filters’ cut-off frequency. If you are using the filters for each user, you must as well consider the bit rate of each user in this case. The “bit rate” mentioned in the script of the filter is also the one that is determined in the global parameters. So setting the value of every parameter which might be used in many components in the global parameters and using the script mode for them can sometimes be really time saving, so you would just change it in the global parameters and its value changes for all of the components.

[Ashu verma]

Hi Gurpreet
Alisth have explained well about your question.I just want to add that run your system with script mode and change data rate in global parameter window.For filter(electrical low pass) ) 0.75*Bit rate is a cut off frequency,you can change it to o.8* bit rate and see the results beacaus for my some of systems it works well.In optiwaves example of CSRZ,MDRZ and DPSK they have considered cut-off frequency 0.8* Bit rate.

[Gurpreet Kaur]

thanks alistu and sam sung for this.

[Ashu verma]

Welcome Gurpreet
All the forum participants are here to help each other.Please also participate more and help other new members as well as senior members.I am glad that suggestions made by me or from other senior members help you.Beat of luck for your future research work.Share more,Guide more and Learn more

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