Dual Drive mach zehnder modulator

[Vishal Sharma]

I am working on optisysytem and in the transmitter block i am using Dual-Drive mach-zehnder modulator. can you please tell me the bandwidth of the modulated signal at the output port of dual-drive mach-zehnder modulator with some refrence.

[Mohamed A. A. Abouseif]

Hi Vishal,
I think the bandwidth of the modulated signal depends on the modulating signal filtering bandwidth.
in the attached example, you can see the difference in the modulated signal after the LiNb Mach-Zehnder modulator at two different values of the input low pass Filter such as 0.2 * Bit rate and 0.9 * Bit rate for example.
if you open the help file of this component, you can see its references:

References:
[1] Cartledge, J. C., Rolland, C., Lemerle, S., and Solheim, A., “Theoretical performance of 10 Gb/s lightwave systems using a III-V semiconductor Mach-Zehnder modulator.”, IEEE Phot. Techn. Letters., 6, 282-284, (1994).

[2] Cartledge, J.C., “Performance of 10 Gb/s lightwave systems based on lithium niobate Mach-Zehnder modulators with asymmetric Y-branch waveguides”. IEEE Phot. Techn. Letters., 7, 1090 -1092, (1995).

Hope that helps,
thanks
Mohamed

[Vishal Sharma]

Thank u Mohamed sir, i think filter bandwidth should be equal to the bandwidth of your message signal. the idea suggested by you is a kind of hit and trial method and if filter the bandwidth is less than the bandwidth of modulated signal then data loss will be there and if it is more then noise content will be there. so is there is any mathematics related to bandwidth of modulated signal in this. what i think is, for example we have NRZ formatted signal at the data rate of R Gbps so the message bandwidth will be R/2. when it is modulated by DD-MZI, it is a kind of amplitude modulation where carrier signal is optical signal so the bandwidth become 2(R/2)=R. but as i use this in simulations, the best results observed at the bandwidth of 3R/2. And i am not getting the point to mathematically calculate it.

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