PM-QPSK

[Monika Mehra]

I want to study the effect of nonlinearities on PM-QPSK coherent system with the help of DSP component.I tried to compensate the dispersion using subsystems . I want to ask that to study the impact of nonlinearities, should i switch off the dispersion in SMF and DCF and enable dispersion compensation , carrier phase estimation and disable nonlinear compensation in DSP component or should I disable the dispersion and nonlinear compensation and enable carrier phase estimation in DSP component. which will give me the accurate result.

[Ashu verma]

Hello Monika,If you want to study the non-linear effects and you have already used dispersion compensation module then there is no need to disable dispersion from SMF and DCF.Effects of non linearities can be seen at high powers.DSP component you are using from optiwave example? Or you tried to design your new one from matlab?

[alistu]

Hi Monika, You have mentioned that you are using subsystems for compensation for the dispersion. May I ask what kind of dispersion compensating you are using? In case you are using DCF, I’d do what Sam Sung suggested. Otherwise, I’d disable the dispersion. If you enable nonlinear compensation, you won’t be able to see the nonlinear effects, unless you want to see how nonlinear effects are compensated.

[Monika Mehra]

thanks samsung and alitsu for ur replies. Now I want to draw a graph between Power per channel and Q factor or BER for WDM-PMQPSK system. I am using PM_QPSK Coherent transmitter. How can i select power per channel from PM-QPSK transmitter.
In some papers I have seen that the graphs are drawn between Power/channel and OSNR at some prescribed BER i.e at BER<10e-3 or some other value. How can We select particular value for BER to draw graph.
kindly reply

[alistu]

Hi Monika,

If you are using one DP_QPSK for each WDM channel, then the power per channel power will be the same as that determined for each DP_QPSK. Otherwise, it depends on how you use optical sources in your system.

When I want to analyze a system at a constant BER, I use “iteration” to repeat the simulation, so that each time I simulate, I have a better chance of getting the BER I intend to get from one of the iterations. This is merely my experience.

[Monika Mehra]

When I made back to back DP_QPSK coherent optical system with and without DSP I got different results in both the cases in terms of BER. For the circuit having DSP component I got BER 0 but without DSP I got BER 0.5. The screen shot of the circuits is attached.Kindly check the circuit and suggest me which circuit should I use to study the effect of nonlinearities in DP-QPSK system.

[alistu]

I am not able to open the osd file you have attached. When I try to open it, I see the error “Access denied”. suggesting “If the file is under a restricted access folder, please move the file to another folder, then try again”. Although the folder was not restricted access, I moved the file to another folder and still the same error is given.

[Monika Mehra]

I am attaching the the osd files. kindly check the circuit and suggest me which circuit should I use to study the effect of nonlinearities in DP-QPSK system.

[alistu]

I think if you intend to show the effect of nonlinearity, then perhaps you can use both, suggesting the system would have these problems due to nonlinearity and by using compensation like the one used, the nonlinearity effect is mitigated (and explain if this was expected and how). This might give more insight.

[Alessandro Festa]

Dear Monika, trying to transmit 100G without DSP is almost impossible, this is why you are obtaining 0.5 BER when disabling it.

[Monika Mehra]

thanks Alessandro for ur reply. so I should go with the circuit having DSP component.

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