Simple Bi-directional Link

Find the corrected file

Hi shahid,
I have redesigned your system file by doing sone cirrections,but couldnt able to upload it.I have uploaded it twice
Any How ,your system having the errors due to some open port components .i suggest you to see the optiwave BPon sample in the samples library.Or you csn visit the link

Broadband Optical System Based on a Passive Optical Network (BPON)

You can design or remodify this system according to your project requirement.Change data rate and you will get the desired results.i have a question why you aee doing this for only single user for bidirectional? You can increase users by setting value at power splitter.
I will tey again to attach modified file if to do so.

Welcome shahid,file is working for both the directions at 2.5 Gbps and you can analyze this system using power meter as you checked before in your file and optical spectrum too.Let me know if you will need any help

Hi Shahid
You have no need to use Dynamic switch as you are using only one Tx.
For buffer working read this

Because the majority of OptiSystem components will not calculate if a signal is not available at the input ports, the Iterations and Initial delay parameter will help the user to avoid a situation in which the simulation will not perform because a component cannot find signals at the input port – and the system will be deadlocked.

The concept of multiple iterations and delays is very confusing, because it does not have a physical meaning. It is a simulation technique and requires an understanding of the calculation scheduler of OptiSystem.
If you need to know more go through this optiwave tutorial

Lesson 5: Bidirectional Simulation — Working with Multiple Iterations

Well, you didn’t tell me about it but if the parameter that you are referring to is something like a delay caused after the signal passing the optical fiber, then it is no wonder why it has the same amount for both users, as both users’ signals are being passed through the same channel with the same wavelength.

Hi Alisthu,You have Copied the correct script from the optiwave BPON example,but Shaid talking about the swithcing timings for two users.The script ypu introduced is for 8 users ,that is why the dynamic y select 1 operates on TimeSlot * (1/Bit rate) *Sequence length / 8 and the next dynamic y select 2 use the value TimeSlot * (1/Bit rate) *Sequence length / 8 + Time window/8.Hope you got my point

Thanks Alisthu for your reply.Its a pleasure to share and discuss the views and concept with you,every time we get to know very new things.Keep it up

Welcome shaid,as Alisthu said,share your queries and we will discuss here to get a fruitful result.i have one question about the system you are simulating that you have took a value of 2.5 G for downstream as well as upstream.As far as i know upstream in GPON is of 1.25 G? Increased data rate effects you r users supported.

Hi shaid,I have pounted out the upstream bit rate according to ITU standards for GPON.However you run your system on 2.5 Gbps ,no issues in that.Even you go for NGPON1 with more data rate .If you want to change the upstream data rate go to PRBS ,set it to normal mode and then enter value 1.25 G.For downstream it is same 2.5G.How many nom of users you have splitted in system? For how much length?

Hi Shaid
I will check your file ,This a common problem in setting the bit rate differnt than Bit rate mentioned in global window.Even this happened to me many times.After modification i will let you knoe,what exactly the problem is.

Found the problem! Well, not exactly but I found the way to skip the problem. Put the global Bit rate parameter equal to 1.25GHz and in the script, put the bit rate for the to ONUs equal to the global bit rate. Put the PRBS for downstream “2*Bit rate”. Some properties of the upstream must match global properties I guess.

Here is the way to interpret the eye diagram:

– The eye opening corresponds to the additive noise in the signal.

– The eye overshoot or undershoot correspond to the peak distortion the signal sees in its path.

– The eye width corresponds to timing synchronization and jitter effects

– And finally, eye closure corresponds to inter-symbol interference in the system.

Using these, you can understand the destructive effects in your system by looking at the eye patterns. I hope this is helpful.

Hello Shaid,As Alisthu said your system file is correct,you can now increase the users if you want.2.5Gbps is not a issue with this system.However for the more practical signal you can use a WDm multiplexer rather than the ideal one.You can set the extinction ratio of the CW transmitter to 30 as EML.ER 10 refers to DML direct modulatated laser.Same advice for the lazers for upstream also.

OOPS ,By observing your file with a great care i found htat you have implemented WDM -PON not TDM for downstream.Shaid your system is not correct from the view of WDm PON,but correct in terms of ey diagram.You have used 2 different wavelengths for downstream and another 2 for upstream.But you havent demultiplex any wavelength at receiver side of both the cases.So how would you come to know which wavelength you are observing.It is not oblivious that your first wavelength signal go to the first port of power splitter.Same in the case of upstream.You have to choose the correct demultiplexing technique for each certain wavelength.Mow you are receiving combined signal at each eye diagram.

I have found the correct way to implement this system.Use AWG for the routing od the each particular wavelength to particular port.AWG just provide you different wavelengths at different output ports attache to the input port collectively.
Basically AWG is a component or devise used to combine or saprate the signals with different wavelengths.For better understanding you can go through the link i have mentioned below
http://www.rp-photonics.com/arrayed_waveguide_gratings.html

WDM Components – AWG Demultiplexer

Here is a example of solution of everything by optiwave samples
https://optiwave.com/download-1/wdm-pon/
You canalso find this system in optisyste 13.If you dont have then v13 then let me know.AWG is there in optisyste 7 and you can utilize that.For further help ,stay active and take a look at ny all replies step by step.Hope you will understand it Thank you

As for your question about the insertion loss, I think 4-5 dB is in many cases realistic for them. However, in many research papers the ideal MUX has been used and this does not prevent generating results and making the point you want to with the simulation. In your case, it can depend on whether you are reproducing a paper and what type of MUX has been used in that paper.

Hello Shaid,I have seen your system and just replaced a photo detector with default one .I have used a besel filter selecting one wasvelength 1546 and i observed better performance of the system .BER resuced to 10^-16 to 10^-18-19 .So i would like you to use optical filter .Rest your system is good.You may increase no. of users by splitting each wavelength 1:n for total supported users.

The MAin use of optical filtres here is to select the wavelength of specific channel which is observed at ONU.In case of Shaid,4 wavelengths has been used 2 for US and another 2 for DS.Now the question is how different wavelengths demultiplexed from a combined data stream.One way is to use AWG for routing.Another is placing 4 optical filters with the specific freq. corresponding to the transmitter side as we do in WDM demux.Here function of optical filter is not to filter noise or passing the the band.

Shaid asked above about the use of peak frequency at the photodetector whether it is PIN or APD.As far as i know you can only get the desired stream of required wavelength by filtering it out.If you selected the one wavelength in PIN down sampling even though you will get the some part of other wavelength too.This is the reason of the boosting in output when we use Bessel filter for specific wavelength.

Hello Shaid,Yes you can use. Alisthu question is here for the use of CW laser without external prbs and line coding.I think ER defination we can find on google easily

Hi all,

This topic is being closed as the main question has been answered. If the original poster has more questions please start a new discussion with the proper title and explanation.

Regards