M-ary encoding

[Prarthana Kashyap]

Hi everyone,
I studied about digital modulation techniques and found that “In digital communications, the modulating wave consists of binary data or an M-ary encoded version of it and the carrier is sinusoidal wave.” so my question is what is M-ary encoding how can we do M-ary encoding in optisystem, I have found here a M-ary encoder but how does it works. please anyone explain this.

With regards,
Prarthana Kashyap

[Abdallah Ismail]

It is simply digital to analog converter.

[Prarthana Kashyap]

Hi abdallah, if it is simply a digital to analog converter the an analog signal is going to modulate the light in case of optical communication, then it is not a digital modulation. Will you please explain in details. Thank you..

Regards,

[alistu]

Hi Prarthana,

Digital signals in OptiSystem are either in binary form or in M-ary form. When the digital data only has two logical values of ‘0’ and ‘1’, it is called binary and otherwise, the data is M-ary. Many encoding components such as QAM receive binary input data and generate M-ary data in the output.

Regards

[Prarthana Kashyap]

Thanks Alistu for the reply, How the M-ary data will look like, can you explain with some graphical representation how the bits will look like. or in case of M-ary encoding there will be more than one threshold. I have seen in many cases that the threshold detector is having some more values of threshold i.e. my question is will it require multiple no of threshold values in case of detection.

Regards

[alistu]

If the M-ary signal has more than two levels, then the threshold detector needs more than one threshold. For example, for a signal formerly produced by a 4-QAM encoder, you only need one threshold, since the M-ary values should be either ‘1’ or ‘-1’ and therefore, there are only two levels for the signal.

[Prarthana Kashyap]

Thank you alistu for the reply, I am still waiting for the circuit which can produce such kind of multilevel signals. because I am not finding the circuit in the help section of the component also.

Regards,
Prarthana

[alistu]

I don’t think it has special circuitry different from an electrical component making a multilevel signal. In OptiSystem, signals have been divided into binary, M-ary, electrical and optical and the format of the vectors produced in each case are different. So it refers to the format of vectors rather than the circuitry.

Regards

[Dr. Dhiman Kakati]

Dear Prerthana, I have attached here with some m-ary visualizer graph, from it you can understand how the M-ary encoded signal look like, regarding how to generate the M-ary pulse the internal circuitry of M-ary pulse generator is not there but you may find some mathematics in the components pdf at page no. 279, the conditions are explained there very nicely. the method of generation is same as that of QAM pulse generator any other of the same kind in the library. Thanks.

Regards

[Dr. Dhiman Kakati]

again the attachment failed. please find here..

Regards

[Prarthana Kashyap]

Thank you Dhiman.. I am still looking for the circuit for generation of this king of pulse..

Regards

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