Search Results for 'wdm'

[gaganpreet KaurParticipant]

Thank you Damian for answering to my query. it is first case where noise in WDM analyzer shows -100 dB so probably whole of signal is converted to OSNR. when checked with OSA it shows noise but at different set of frequencies. what does that imply?

[Swapandeep KaurParticipant]

sir in this wdm edfa simulation which i am attaching , the q factor is increasing with distance in absence of self phase modulation, at distance of 50 km , its 3.94, and at distance of 100 km ,it is 4.84. please check…

[Damian MarekParticipant]

I’m away from the office this week, so my responses will be limited. However, I believe this stems from the WDM Analyzer being used incorrectly. Look at the WDM Component Properties and it may give you a more in depth answer but here goes my quick explanation.

The WDM Analyzer calculates the OSNR in two distinct ways in the first method it simply compares the signal power to the Noise bins power. By default noise bins have been changed to be converted to a signal. Most likely any noise in your project has been added to the signal and no noise bins are present giving you an OSNR of 93 dB, which is quite high. Verify with an Optical Spectrum Analyzer if there is any noise present and what the expected OSNR should be.

The second method uses the peak signal power and lets the user choose how far to offset the frequency to choose the noise power. In WDM systems this is normally half the channel bandwidth which corresponds to the frequency directly between channels.

[Amitoj Singh]

Can any body tell me how to start .

Thnking u in anticipation

[Amitoj Singh]

After designing wdm system or simple optical communication system it was found that BER value fluctuates even for the same parameters .If user has taken readings at certain time interval after simulation.If user again simulate that system for same parameters this time BER value came different

[Swapandeep KaurParticipant]

thank you sir. i went through the tutorials but its not explained how the upper pump frequency is set but the values are given directly. I think we are taking wdm transmitter frequencies as 1552 nm (193.1 Thz) and spacing (.8nm) 100 GHz, and channels are 16, then pump frequency should be 1540 nm . but still i am not getting any result. is it because the frequencies at the transmitter are in thz and in raman amplifier in nm? i am attaching the file.

[Tung Tran VanParticipant]

I read some dwdm mux/demux’s datasheet, it usually has a 3dB filter bandwidth of 0.1 nm , even up to 0.45 nm. When increasing the bandwidth of mux/demux, the system performance increases greatly.
But I’m getting a problem, when I use optical fiber & 2 amplifiers: Boost Amp – BA & Pre Amp – PA, I dont know why calculating optical fiber is extremely slow. I have waited 10 minutes and it has not finished yet. When deleting the BA, it run faster.

[alistuParticipant]

You’re welcome Gaganpreet. My perception was from your sentence “… we dont have choice of using advanced modulation formats as we can do for NRZ, RZ …” (even though this was right; we can’t choose advanced modulation formats other than RZ and NRZ). However, there is no other way to consider coding after WDM transmitter as you have mentioned as far as I am concerned.

Regards

[alistuParticipant]

The bandwidth of each channel in WDM depends very much on the bit rate of that channel and the coding scheme adopted. I have noticed in many cases they consider the bandwidth about ” 0.6*Symbol Rate “. To optimize the dedicated bandwidth, you may need to have a trade off between Q-factor and bandwidth efficiency sometimes.

[gaganpreet Kaur]

Hi my query is in some of simulation results WDM analyzer between input and output before receiver detection show OSNR as high as 93 dB but even of my best efforts no acceptable BER or eye diagram is achieved . when i compare it with sample file in terms of power detected at receiver with help of electrical power meter , power is more than in the sample file . my first concern why if more power is received at output and it is possible that we don’t get BER less than 10^-9 when compared to a system which has lower output power but still BER is >10^-9.

My second question is does OSNR andBER relation deifned by
Log10 (BER) = 10.7-1.45 (OSNR) hold true for all system designed in optisystem.
Kindly help it is important.

[gaganpreet KaurParticipant]

Alistu i need to understand theoretical relationship between WDM transmitter BW and MUX bandwidth.i was unable to open the file this hour coz optisystem is available only during working hours at college . but i have never optimized mUx BW and a s result many times i received no output BER or Eye diagram but admitting it i was not even aware of this thing. i will try on my design but i need to know criteria of matching bandwidth of MUX/demux with WDM transmitter BW.

[gaganpreet KaurParticipant]

Thank you so much alistu. but my concern is not using RZ /NRZ or ofn-off keying but as we increase dat rate upto 100 Gbps or 112 Gbps obviously we need modulation formats which accomodate more than 2 bits per symbol such as QAM, PM-DPQSk etc which require a coherent detection system. it is ok to see output by putting all for single channel and checking the output(though i hhhave not tried) but whenever i start design and with all recent research available if i intend to design a 100 channel WDM high data rate system with these advance modulation formats it is tiring to design or externally connect transmitter to each channel. i want to know if i can design such system using a single module as WDM transmitter and simply chosing a new format .

[gaganpreet KaurParticipant]

Sorry to interrupt but i suggest wdm power of 10 dBm is too high. major difference in edfa and Raman amplifier outputs stems from pump frequency . u may use power meter at output of amplifier both EDFA and Raman. difference in output will suggest you if it is matter of meeting minimum power requirements. next you use optical spectrum analyzer and WDM across amplifier again in both cases of EDFA and Raman. it will help you analyze problem area is it low signal availability in case of Raman or increased noise. accordingly you may vary it pump frequncy tuning.i hope it helps.

[Swapandeep KaurParticipant]

and i do not get any result when i replace the edfa by raman amplifier though i increased the wdm transmitter power to 10dbm , more than that is taking too long to execute.

[Swapandeep KaurParticipant]

thank you sir. Since i am implementing a wdm system, i have directly used a wdm transmitter( 16 channel) with 193.1 Thz frequency and 100 Ghz spacing.