LiNb Intensity Modulation

[Ibn Aziz]

Q. Hi every one, I need ur help

I am using Dual-port Linb MZM for Intensity modulation (externally modulation) so what are the parameters like switching bias voltage, switching RF voltage, bias voltage1, bias voltage2 and Vpi meant to be ? and hw I use them to do Intensity modulation.?

kindly help me to understand how I wil work with it for doing Intensity modulation.

I got a file from the forum but could understand it kindly help to understand all three mode of operation.

I wil be very thakful to u..

Best Regards
Best Wishes

[Dr Rk Sethi]

The MZ modulator is the basic building block used in optical communication links for modulation; it is based on the principle of interference using the electro-optic crystal. It modulates the output intensity as a function of the externally applied voltage.

It is implemented using two 3 dB couplers, connected by two equal lengths’ waveguides. Because of the electro-optic effects the externally modulated applied voltage results in the change in the refractive indices in the waveguide section. The various signal paths can results in additive and subtractive interference at the output as a function of the applied voltage. This results in the modulation of the output intensity as a function of the voltage.

[Parikhit Dutta]

Hello,

If you notice the equation expressed for the o/p of a Lithium Niobate MZM in the OptiSystem Component Library file which you can find in ‘Documentation’ sub-folder of OptiSystem folder, it is expressed in terms of the i/p optical field, insertion loss, electric voltages given onto the two arms of the Lithium Niobate MZM, DC bias voltages (Vbias1 and Vbias2), switching modulation (VpiRF) and switching bias (VpiDC) voltages. As Sir Sethi mentioned in the previous post, the electric voltages applied to the two arms result in a change of refractive indices in the two arms of the MZM.

The o/p optical field when expanded results in a expression containing cosine of cosine terms which can be expressed in terms of Bessel functions. Theoretically the o/p optical field contains infinite terms-an optical component at the same frequency as the i/p optical component and components at frequencies offset from the i/p optical component. Thus, if the frequency of sinusoidal is fs and that of the optical i/p is fo, the o/p optical field will contain components at frequencies, fo, (fo + n*fs), (fo – n*fs) where n = 1, 2, 3, …

* As far the properties are concerned, VpiDC and VpiRF are usually the same and set to Vpi.
* The ‘normalize electric field’ is usually left checked. If unchecked the peak amplitude of the sinusoidal signals for modulating the two arms has to be set accordingly.
* The modulation voltages (modulation voltage 1 -> Vmod1 and modulation voltage 2 -> Vmod2) are the peak amplitude of the sinusoidal signals and are divided by 2 when the ‘normalize electric field’ is checked.
* The bias voltages are the DC bias voltages, Vbias1 and Vbias2.
* By setting suitable values of Vpi, Vmod1, Vmod2, Vbias1 and Vbias2, the output optical field can be tuned to contain only even components (n = 2, 4, …), odd components (n = 1, 3, …) or both. The primary component can also be suppressed.

[Ibn Aziz]

Thanks alot Parikhit Dutta for ur kind response.

Best Regards
Stay Bless

[Anu Prasad]

Hello everyone..

I too need your help. Actually i was working on a 12-tupling scheme of millimeter wave generation. But i am not able to get the required sidebands at 193.04 and 193.16 THz. Instead i am getting sidebands at 193.06 and 193.14 THz. Also i dont know whether tochange any of the parameters of polarization controller. Please help me to give settings to both the modulators. I am attaching the project file worked on Optisystem 13. Kindly provide me with appropriate suggestions so that i can come out with desired results. Waiting for your kind reply.

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