DQPSK vs 16QAM

[Dr. Dhiman Kakati]

Hi all,
While designing a fiber transmission system which detection scheme is advantageous i.e. coherent or non-coherent detection if we consider the case of long distance transmission. let us consider the DQPSK and 16 QAM, which among these two will give more long distance transmission or distance of transmission does not depend on modulation scheme. I am looking for theoretical concept. i want to no which modulation scheme provide more immunity to fiber attenuation and dispersion.

Thanks.

With Regards

[alistu]

Hi Dhiman,

Theoretically, for higher order modulations the decision boundary in constellation plane is smaller. Therefore, more power should be used to achieve the same BER. This extra power may cause nonlinearities to step in and corrupt the signal. Therefore this way you may be limited using higher order modulations for long distances.

Regards

[Dr. Dhiman Kakati]

I agree to you Alistu, I found that in case of transmission distance DQPSK is more advantageous than the 16-QAM as it has more decision boundary so it will provide more transmission distance. on the other hand 16-QAM is good for higher bit rate but not for higher transmission distance as the constellation points are closer. Thaanks Alistu for the reply.

Regards,
Dhiman

[alistu]

You’re welcome Dhiman. A compromise between the two can also be used in optical systems, especially in future passive optical networks in my opinion, where the reach is expected to be longer and the number of subscribers increased compared to the prevailing optical access systems.

Regards

[Dr. Dhiman Kakati]

Hi Alistu, The sub carriers you have mentioned in the above comment, is it the same as that of OFDM or its multiplexing of carriers, Which one would be beneficial.

Regards,
Dhiman

[alistu]

I have used the word “subscriber” in my above comment. The word “user” is another word that is commonly used instead of “subscriber” in the papers. Of course, in passive optical network proposed schemes based on OFDMA technique (and not in OFDM), sometimes each subscriber has their own subcarrier.

[Dr. Dhiman Kakati]

Thanks for your kind reply, Now to be more clear regarding this can you please refer me any design or paper which will help me to better understand this.

Regards,
Dhiman

[alistu]

You’re welcome. Indeed! Please refer to the paper “OFDMA-PON for future generation metro-access networks” by J.M. Senior in which diagrams of the aforementioned access scheme can be found:

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6458042&newsearch=true&queryText=ofdma%20pon

Regards

[Shahid]

Dear Dhiman, I’m want to make a DQPSK transmitter and receiver but I haven’t found in the library of Optisystem.
Can you share your DQPSK Design/System?

Thanks

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