Regarding RF-FSO

[Saruchi Attri]

Hii everyone,
I am working on free pace optics using optisystem v12. Please tell me how we can transmitt Rf Signal in FSO Link.
Thanks
Saruchi

[prakash jat]

hi saruchi
as we are transmitting rf over fiber we can also send as on fso by replacing fiber by fso

[Saruchi Attri]

Thanx prakash
But i dont even have any idea that how to transmit RF signal over fiber also. please give me any idea.
Thanx

[prakash jat]

Take as: PN seq.-> nrz-> multiply with sine wave-> mzm with source -> fso -> pin-> multiply wtih same sine wave -> 3 r genrator -> see the signalv using osc.

[Dr. Dhiman Kakati]

Hello Saruchi Attri,
you may find the following steps helpful, For radio over free space you have to use the concept of Radio Over Fiber,

Here we modulate the output of CW laser with applying the electrical pulse to th RF plates of the Mach Zehnder modulator and take the optical waveform an apply to second MZM where you need to apply a sine wave at the RF plates of your required RF frequency. This is a kind of analog modulation and you can easily extract the radio frequency at the receiver side and from that the data transmitted. please check the last two samples available at the Optisystem samples folder “Microwave and RF optical systems”.

Regards,
Dhiman

[Dr. Dhiman Kakati]

In the Free space optics (FSO) link in place single mode fiber (SMF) we use the FSO componet. That is the difference with the two sample files. I may also provide some other working samples (I need to check for the working one) tomorrow when I would be able to access Optisystem software.

regards,
Dhiman

[Saruchi Attri]

Thanx Prakash and Dhiman
your suggestions were very helpful. But in my design I am using OFDM modulation and by using RF signal it is creating problem in generation of constellation diagarm. I have attached the osd file here. please tell meif the design is correct.

Regards
Saruchi

[Dr. Dhiman Kakati]

Hi Saruchi Attri,
I am looking into your design file to find some solution. But I want to mention one thing that for the FSO channel you are taking an attenuation of 0.11 dB/km which is far lesser that fiber i.e. 0.2 dB/km whereas it is 20 dB/km. So please change that value to respective default one though it is for simulation you can take but that system will not be practical one. i will let you know If I get a solution to your issue. Thanking you.

Regards,
Dhiman

[Saruchi Attri]

Thank you Dhiman,
I was changing the attenuation to get the results. System wasn’t working at high attenuation that’s why I have reduced that. please find any solution if you can.
Regards,
saruchi

[Dr. Dhiman Kakati]

hi Saruchi, I am also new to OFDM So Gokul Boro may help you properly in your case, i would request Gokul to respond to this. Thanking you.

Regards,
Dhiman

[Saruchi Attri]

Thank you Dhiman,
I appreciate your help.
Regards

[SAHIL SINGH]

Hello Saruchi Attri,

I agree with the point of view of Dhiman that for radio over free space you have to use the concept of Radio Over Fiber,you must take into consideration the fact that we modulate the output of CW laser with applying the electrical pulse to th RF plates of the Mach Zehnder modulator and take the optical waveform and apply to second MZM where you need to apply a sine wave at the RF plates of your required RF frequency.Also do check the last two samples available at the Optisystem samples folder “Microwave and RF optical systems”.

Regards,
Sahil Singh

[Saruchi Attri]

Thank you Sahil,
I will do it and I will ask for the help again if I got stuck at some point.
Regard,
Saruchi

[SAHIL SINGH]

Hi Saruchi,

Just try to do it as mentioned in the previous post.. It will surely work for you… You are free to seek suggestions anytime and we will try to the best of our ability to have a workable solution… All the best

Regards
Sahil Singh

[rahul kumar]

Hi Saruchi Attri,
First design the system as per your requirements and then replace single mode fiber with Free space optics(fso).
You should refer to the optisystem samples file and try to learn from there.

Free Space Optics (FSO)

Free Space Optical Links [Optical System]

log-normal channel in FSO

Please refer to following links.

[rahul kumar]

Hi,
As we use wireless optical channel component, that is also free-space optics, can be used for large distances where the atmospheric attenuation is not the major source of penalties, but the pointing angle is. e.g. satellite communications. The impaired link performance from pointing errors between the transmitter and receiver for satellite communications.
https://www.osapublishing.org/jocn/abstract.cfm?uri=jon-2-6-178
http://www.ciitresearch.org/dl/index.php/pdcs/article/view/PDCS092009004
http://www.ijcaonline.org/archives/volume104/number10/18235-9224
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1268928
The above links will help you.

[Saruchi Attri]

Hii everyone.
Thank you for your suggestions.
I have tried what you guys have mentioned, but the problem of constellation diagram remains the same. I am attaching the osd file here plzz check if system is correct. Any one have knowledge about OFDM please do rply. I want to ask one more thing that which system should perform better practically, simple FSO or RF-FSO.
Regards
Saruchi Attri

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