Laser used in WDM transmitter

[Marvi grover]

i am attaching a system designed in optisystem. kindly take a look at the transmitter part and let me know if it is a valid system. Is it possible to use a single continuous wave laser as the source(for a WDM system), split its output using a fork and then use MUX for wavelength division multiplexing??. also here the modulator is used after the MUX. will this system produce a multiplexed output.

i shall be really grateful for any help provided

thankyou

[alistu]

Hi Marvi,

You’d better use CW laser array as the laser source. Also, you should use a separate PRBS generator for each user, otherwise it negates the reason for using WDm in the first place. I suggest you use WDM transmitter component in transmitters library, which contains both PRBS generation part and the optical power source.

Regards

[Marvi grover]

Hi Alistu,
thank you so much for replying.

Actually i saw this system in a research paper published in Springer. but i was not convinced with the working of this system.there it is shown as an improvement of the system which uses a laser array, in order to reduce its complexity, the author used a single laser.
i wanted to further optimize this system. so should i continue with this system or should i use the array only??

i have attached the paper for your reference. please have a look once and suggest the i should work on this or not.

[alistu]

Thank you for the paper. In the system design, a fork has been used instead of power splitter at the transmitter. Since there is no such component in reality, I believe it is like using an array of lasers or a laser with much more power together with a splitter. So if you want to implement system II of the paper, you should use a splitter and a laser who has 20dB power at each output branch of the splitter.

[Marvi grover]

okk. Thanks Alistu
but i have one more doubt, the power splitter would split the laser power into multiple ports but the wavelength of light coming out from each port of the splitter would be same because we are using one laser as the source. so how will wavelength division multiplexing happen beacause we need different wavelengths for WDM.
i also want to know if there is a multiwavelength laser available in optisystem???

thankyou

[alistu]

You’re welcome. As I mentioned in my first reply, CW laser array consistes of several lasers each with a different wavelength from others and can be used in WDM systems. I am not quite sure about what has been done in the paper to produce multiple wavelengths (if actually they have been produced), so can you please upload your implementation of the paper so as to examine it?

[Marvi grover]

okk. I am attaching the file. please check if the wavelength division multiplexing is actually happening. the BER analyser might show a perfect eye diagram because i have made the component noises negligible. The actual paper has been implemented in optisystem 11.

[alistu]

Thank you for the attachment. There is no change in the signal in the output of the multiplexer when compared with laser spectrum, except for the fact that its power has increased due to fork being used (which multiplies the power as we discussed). I don’t really understand why the author has even used WDM for this purpose. BTW, The impact factor of the journal is around 0.6, so I wouldn’t trust the results so much.

[Marvi grover]

Hi Alistu. .. I got some justification for the above discussed system. Actually the MUX used in optisystem has inbuilt filters at each of its input channels which have some central frequency(each channel has a different central frequency). so each input of the mux filters only that particular frequency and allows it to go further. so in this way the wavelengths are seperated.

but i wanted to know if the Laser used in the system emitted only one fixed frequency or it emits a small band of frequencies???

Regards

[alistu]

Even though the parameters you mentioned have in-built filters and their spacing can be determined and so on, if you use OSA visualizers to see the spectrum after the laser and after the MUX, you will notice there is absolutely no change in the spectrum except for the fact that the power has increased due to the reason I mentioned before.

[Marvi grover]

ok. Thanks a lot Alistu.

[Marvi grover]

ok . again thanks a lot alistu.
i am really grateful for your help. one last question… the ‘fork’ present in the optisystem is available practically or not???

[alistu]

You’re welcome Marvi. The fork system copies the input and sends it to the output. So if the total output power is measured, it is more than the input power. This component is not based on a real component, but it may be useful in the simulations, as you can see it being used in OptiSystem samples.

Regards

[Marvi grover]

ok.. Thanks A lot Alistu .

[alistu]

You’re welcome. Another strange thing about the implementation in the paper is the fact that one PRBS generator is used. So I don’t think using an access method such as WDM is of any use, since only one user is available here and it is a kind of point-to-point communication. I thought this was worth mentioning because it is also something you should consider beside laser frequency.

Regards

[Marvi grover]

yes Alistu, even i had the same doubt. multiplexing is being done before modulation.
i am trying to use some new components to improve the system.

i am not able to find out the 32 bit version of optisystem 14 or 13 or 12 for the 30 day trial use.
as my laptop is 32 bit, so 64 bit version is not getting installed on it. can you please suggest me how to download the 32 bit version.

Regards

[alistu]

Unfortunately, I don’t know what can be done about it, except for what I have suggested in your other topic. Of course, you can reinstall a 64-bit windows operating system to be able to use the current version. 64-bit version makes better use of RAM than 32-bit, it is generally better to use that if possible.

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