On Which Factors MZM extrinction value depends

[Abdullah Baig]

Dear Members
I want to inquire on which factors MZM extriction value depends. I am working on Radio over fiber system. When i set Extrinction ratio 30dB then Min Ber becomes 0 which is incorrect but when i set extrinction ratio under 10dB then Min Ber shows some value.

[Ravil]

Hi Abdullah,

In all telecom. systems (for any propagating wave) the extinction ratio is the ratio between “1” and “0” levels (peak and valley). There is the extinction ratio for two polarization components which is defined in the same manner.
In general, this ratio depends on modulation voltage (half-wave voltage) which in its turn depends on the materials you use and your regime parameters.

[Heitor Galvao]

perfect

[Abdullah Baig]

Dear Ravil Thanks alot for your reply.
Actually in my project i am using 3 laser i-e 1,2,3 with frequency 193.2, 193.21 and 193.14 respectively.

The difference between laser 1 and 3 gives upper lower frequency spectrum 60GHz and Laser 2 and 3 gives upper frequency spectrum 75GHz.In this case which Extrinction ratio should i selecte i-e 1dB,2dB,3dB etc.As Extrinction Ratio =P1/Po

Please check the snap shot
Best Regards

[Damian Marek]

The extinction ratio as Ravil said determines the ratio of power from an “on” state and an “off” state. Typically you would want this to be large, but I am not sure what your goal is. You want to mix the lasers to get different frequencies at your output? In your design what determines the correct extinction ratio?

Regards

[Dr Rk Sethi]

Hi Abdullah Baig,
I think logically your results are good, because When you reduce Extinction ratio then BER increases.

In the Mach Zehnder modulator the extinction ratio is an important parameter of the specifications. The Extinction Ratio value is defined as the relation between the maximum and the minimum power levels of the transfer function. For equal power split between two interferometric branches, there is an infinite extinction ratio. It indicates the signal intensity that the transmitter feds to the fiber. Hence, a higher extinction ratio also allows a greater transmission between repeaters in the long distance transmission systems.
In practice fabrication tolerances make it very difficult to obtain an equal power split between two branches and therefore we get a finite extinction ratio which degrades the quality of the signal. A typical value is between 20-40 dB.

[Abdullah Baig]

Sir Rk Sethi Thanks alot for such Explanatory Answer.
Sir i have optimized my system on 2dB Extinction Ratio and the system is showing good results with good eye opening.
As you said that the typical value is between 20—40dB. But in my case i am using 2dB. Is it Practically possible? Because theoretically it is showing good results.

Hoping for your kind reply
Best Regards

[Ravil]

Hi Abdullah,

As it was discussed before, the result of extinction ratio you are getting are unusual. As Damian said, I would check the parameters you are using for its definition based on your design. For me it looks like inverse ratio…

[Dr Rk Sethi]

HI Abdullah Baig,
You are most Welcome.
Presently I am busy with final submission? I hope your problem have been solved with the advice of the Damian Marek.
I will get back to you very soon.
Regards,

[Author]

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