synchronous heterodyne receivers

[Muhammad Zubair Khan Niazi]

I want to implement synchronous heterodyne receiver in optisystem. how it is possible to implement phase-locked loop with APD and amplifiers? please Help!

[Muhammad Zubair Khan Niazi]

here is the block diagram of receiver. I want to implement it in optisystem. please help!

[Aabid Baba]

Hello Zubair,
As far as your query is concerned, it has been already mentioned in one of the threads by Damian. I would be sharing the link. I hope this will help you and I believe this might give you an idea about how to implement a feedback system in optisystem.
Try going through this link.

Feedback and Individual Samples [Optical System]

Regards

[Hamza Ali Abbas Khan]

Hi.
As already mentioned by Mr.Aabid that this has been already discussed on the forum before, I want to add that It has been rightly mentioned that in OptiSystem a signal is generally expressed as a sampled signal, which is passed to a component in one chunk. To perform time domain calculations, like feedback, the sampled signal must be converted to individual samples, which consist only of a single signal value and its corresponding position in time. This allows OptiSystem to propagate the samples through different components at different times. The attached project file Electric_Phase_Locked_Loop.osd is an example of an electrical feedback system.
You can follow the tutorial on this example at:

Electrical PLL

I hope this will be helpful to you.
Thanks
Regards

[Aabid Baba]

Hello Hamza Ali Abbas,
Thank you for providing the example . This will be largely helpful to Muhammad Zubair as far as his requirement is concerned.
Regards

[Muhammad Zubair Khan Niazi]

Respected Friends
thanks for help. As same i have implemented in my receiver section but failed to demodulate the signal. i am attaching my work in optisystem. kindly check and point out the mistake(s) in my work.
MAIN PURPOSE:
demodulate signal by using PLL.
1) system works correctly uptill Photodiode and AGC amplifiers. Ahead i am facing problem to demodulate signal by using phase locked loop (PLL).
Highly thankful.

[Aabid Baba]

Hello Muhammad Zubair,
I don’t have access to the tool at the moment so I can’t view your .osd file right now.
you using which visualiser after the photodiode to visualise the signal?
Actually I am not aware about the functionality of phase locked loop in optisystem. What component are you exactly using for demodulation of the signal. I would be glad if you share this information.
Regards

[Muhammad Zubair Khan Niazi]

Hello Dear Aabid Bada!
i am attaching snapshot of my work, please check this out,after photodiode and AGC amplifier i want to demodulate signal using PLL.

[Muhammad Zubair Khan Niazi]

here is the paper i want to simulate.

[Aabid Baba]

Hello Muhammad Zubair,
I am not able to infer the functionality of your design. In case of demodulation what are you using combiner for?

[Muhammad Zubair Khan Niazi]

Hello Aabid Baba,
what should i used instead of combiner? how to move forward? after AGC amplifier?

[Aabid Baba]

Hello Muhammad Zubair,
The way you have used your components in the design I don’t think it forms a proper feedback loop. You better look at the example provided by Hamza Ali.
If still you face a problem I suggest you to private message Damian. He would definitely help you in this regard.

Regards

[Muhammad Zubair Khan Niazi]

okk thanks Aabid Baba!

[Karan Ahuja]

Hi.

I am attaching link of one paper which expains the impact of atmospheric turbulence-induced scintillation and phase aberrations on the performance of free-space optical links in which the receiver uses modalwavefront compensation and synchronous homodyne or heterodyne detection. It defines a mathematical model for the signal received after propagation through the atmosphere and after modal compensation. By noting that the down converted electrical signal current can be characterized as the sum of many contributions from different coherent regions
within the aperture, It also shows that the PDF of this signal can be described by a modified Rice distribution. The parameters describing the PDF depend on the turbulence conditions and the number of modes compensated at the receiver. We have provided analytical expressions for the symbol error probability (SEP) for synchronous detection of M-PSK with additive white Gaussian noise, and have used them to study the effect of various parameters on performance, including signal level, aperture diameter, turbulence strength, and the number of modes compensated. We have separately quantified the effects of amplitude fluctuations and wavefront phase distortion on system performance, and have identified two different regimes of turbulence, depending on the receiver aperture diameter normalized to the coherence diameter of the wavefront phase. When the normalized aperture diameter is relatively small, amplitude scintillation dominates and, as phase fluctuations have little impact, performance is virtually independent of the number of modes compensated. When the normalized aperture is larger, amplitude fluctuations become negligible, and phase fluctuations become dominant, so that high-order phase compensation may be needed to improve performance to acceptable levels. We have found that for most typical link designs, wavefront phase fluctuations are the dominant impairment, and compensation of a modest number of modes can reduce performance penalties by several decibels.
Here is the link. You may refer to it. Hope it helps
http://ee.stanford.edu/~jmk/pubs/performance.coherent.atmospheric.compensation.optics.express.8-08.pdf

Thanks

[Karan Ahuja]

I want to add that The performance of an optical heterodyne receiver for communication through the clear-air turbulent atmosphere is considered. Optimum and certain suboptimum adaptive processors are developed for receivers that synchronously demodulate the IF signal and those that use envelope demodulation. Error probabilities are presented demonstrating the effects of turbulence level, signal strength, and spatial diversity on binary orthogonal communication systems. In addition, a simple expression is developed for the optimum aperture size of an optical heterodyne receiver.A receiver sensitivity expression applicable for both PSK homodyne and heterodyne optical fiber transmission systems is derived taking account of polarization misalignment, reduced modulation depth, preamplifier thermal noise, power coupling ratio of the fiber coupler, local oscillator excess intensity noise, and reference phase errors. From a comparison of recent studies on system performance degradation due to laser phase noise a generalized expression relating beat linewidth to phase error variance for pilot carrier and Costas phase-locked-loop receivers is defined.

[Karan Ahuja]

I would suggest you to go through following links. I am sure these will help you.
https://www.osapublishing.org/ao/abstract.cfm?uri=ao-19-4-582

http://ieeexplore.ieee.org/xpl/login.jsptp=&arnumber=1075536&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F50%2F23177%2F01075536.pdf%3Farnumber%3D1075536

http://ee.stanford.edu/~jmk/pubs/performance.coherent.atmospheric.compensation.optics.express.8-08.pdf

https://books.google.co.in/booksid=1FbDg3PyCocC&pg=PA305&lpg=PA305&dq=synchronous+heterodyne+receiver+in+optical+communication&source=bl&ots=DqFpJkAuZ6&sig=Z9KUCIxLWk3ersuttXCSlQM3EY4&hl=en&sa=X&ved=0ahUKEwjn6_mZ98vNAhULipQKHQIyByIQ6AEIRjAH#v=onepage&q=synchronous%20heterodyne%20receiver%20in%20optical%20communication&f=false

https://books.google.co.in/booksid=S4LW20vn7F0C&pg=PA280&lpg=PA280&dq=synchronous+heterodyne+receiver+in+optical+communication&source=bl&ots=aV9537Ap_K&sig=Ne5bdWyApVbzsbl8sm4CmML1qU&hl=en&sa=X&ved=0ahUKEwjn6_mZ98vNAhULipQKHQIyByIQ6AEITTAJ#v=onepage&q=synchronous%20heterodyne%20receiver%20in%20optical%20communication&f=false

Thanks

[Aabid Baba]

Hello Muhammad Zubair,
You are welcome anytime. I hope you problem gets resolved as soon as possible.
All the best (y). Regards

[Author]

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