Optical Output Power Of Laser Emission

[ZULKARNAIN]

How to study the nature of optical output power from a laser depending on various parameters of the Laser and the input signal.

[aasif bashir dar]

hi zulkarnain,
optisytem implemenatation of to study the nature of optical output power from a laser depending on various parameters of the Laser and the input signal, i guess is simple.

you just connect some laser to receiver.

but before i suggest you some thing , you please it abit further.

with regards

[ZULKARNAIN]

Thankyou Aasif for your reply and valuable time.
Well i have to study the different kinds of modulations techniques like Electo-Absorption Modulation,Electro-Optic Modulation and Direct-Current modulation by varying the various parameters.

[ZULKARNAIN]

Will you please tell me how to connect the circuit components to study the various parameters.

[alistu]

Hi Zulkarnain,

For your purpose, I believe the OptiSystem samples are quite useful. Almost any particular component you would like to know how to set up you can find by searching through in OptiSystem samples. In cases you did not find a particular component set up in there, name it so I would attach it if I could.

Regards

[aasif bashir dar]

hi zulkarnain,

i think if you have optisystem , the optisystem samples are quit handy for you to study the nature of optical output power from a laser depending on various parameters of the Laser and the input signal.

if dont have optisystem samples. you can visit optiwave site for further information.

with regards

[ZULKARNAIN]

Thank you Alistu and Asif.
In the setup i used a random bit sequence generator and Non-Return-To-Zero Pulse generator. If we are using a random sequence generator,then why are we using Non-Return-To-Zero Pulse generator.Is it used for the modulation of the bit sequence generated by random sequence generator.
Could you tell me if we can use a Return-To-Zero Pulse generator in place of Non-Return-To-Zero Pulse generator.

[alistu]

You’re welcome. Using NRZ or RZ in the system has nothing to do with the PRBS generator or User defined bit sequence generator being used in the implementation. RZ and NRZ are the formats of the bits generated by the bit generating component, whether we have defined them or they have randomly been defined.

[aasif bashir dar]

hi zulkernain,
you can use both Return-To-Zero Pulse generator in place of Non-Return-To-Zero Pulse generator.

since you have to also check the nature of optical output power from a laser depending on input signal.the RZ, NRZ or any other pulse format is your input

with regards

[aasif bashir dar]

hi zulkarnian ;
if you would used the the data for transmission purposes ,then performance of Return-To-Zero Pulse and Non-Return-To-Zero Pulse generator pulse will have to be selected as per needs.
example optical band of RZ is sligtly greter than NRZ, hence suffers little for dispersion than RZ

with regards

[alistu]

Hi Zulkarnain,

I would like to add that even though both RZ and NRZ have both their own advantages and disadvantages, a very important aspect of implementing NRZ in practice is the fact that it is more according to current protocols and standards in comparison to RZ in therms of encoding schemes it uses.

Regards

[ZULKARNAIN]

THANKYOU AASIF FOR YOUR REPLY.

[ZULKARNAIN]

What should be the power of the laser. It is showing a default value of 0dBm.Also is there any limit for the power level of the laser as if we increase the power level at the input, it will result in greater output .Also is there any relation of ISI with input power level.

[alistu]

Hi Zurkarnain,

There are two limits to increasing laser power in practical systems: Firstly, if the power exceeds a certain value, nonlinear effects emerge in the optical fiber. Secondly, practical lasers with higher power are more costly and offer more impairments such as higher spectral linewidth.

Regards

[aasif bashir dar]

hi zulkarnian ,

0dbm means 1milliwatt.
power in dbm = log power(in milli watt)/1mw
there is no logic behind behind increasing power to vary high value.
however you can change power of laser as you wish for simulation purposes.

i suggest to please explain what are you up to

with regards

[ZULKARNAIN]

Thank you aasif for your reply.
I know that odBm means 1mw,but i was asking for the increase in the power level of the laser to values greater than 0dBm as voltages greater than threshold level of the laser will result in greater output.

[aasif bashir dar]

hi zulkarnain,
incresing power will utimately will lead to higher output and greater sensitivity at the detector,
however for practical considerations incresing power to the very high level is not good idea. it will leadto non linear effects and thermal effects at both transmitter and detectors.

with regards

[ZULKARNAIN]

1.How can we increase the switching speed of the laser since the input frequency in very high,so the switching speed of the laser should also be high to avoid errors.
2.Is the switching speed of the laser related to the bias voltage of the laser.

[ZULKARNAIN]

That means if we are increasing the power to higher levels it may lead to burnout of the laser.

[alistu]

Instead of increasing the laser power in your implementation (which may not be compatible with some standards) to get better results, I suggest that you use optical amplifier and put it before the transmission line to amplify the signal injected into power. This type of amplifier is referred to as “Power booster”.

[aasif bashir dar]

hi zulkarnian,

i suggest to clear the working of components first,
there is nothing in switching of laser , since you are using cw laser (contineous wave laser).

with regards

[aasif bashir dar]

hi zulkarnain ,
you are taking about dmls i.e directly modulated lasers, if soo then switching speed is of necessary consideration for the lasers, because the data rate may be in 100;s of gbps in some networks.
more over we have to check for the extinction ratio(i.e on of ratio) for sauch laser

with regards

[ZULKARNAIN]

Thank you aasif for your kind reply and your valuable time for replying my queries.
i understood that switching speed in critical in dmls and also the value of ER should be high,otherwise if high power is transmitted but ER is less, the power transmitted is useless as probability of error at receiver is much more.

[aasif bashir dar]

yor are welcome zulkarnain

[Ranjeet Kumar]

Hi zulkarnain,
We can study the optical output power of laser by connecting it to optical receiver through optical fiber and we can connect an attenuater in between them. Now we can vary parameters of laser like power in dbm (mw) and we check the optical output power the receiver ends by optical power meters.

[ZULKARNAIN]

Hi ranjeet..
Thankyou for your reply..
Can you explain why we have to use an attenuater in between receiver and optical fiber?

[Aabid Baba]

hi all,
As far as i understand , ranjeet has a point of telling you that you could vary certain parameters like power and length as he mentioned above while in cooperating attenuation for different parameter values. Well i guess this could help you for understanding various scenarios where you could study output power and the effect of changing different parameters on the output power.
Regards

[Jojo Mathew]

Hello zulkarnain
This is a reply to your query “That means if we are increasing the power to higher levels it may lead to burnout of the laser.”
I think by increasing we just increase the frequency of the wave.
Corrections are welcome.
Regards.

[Jojo Mathew]

Hi Zulkaran
This is a reply to your comment “Will you please tell me how to connect the circuit components to study the various parameters”
Connection of the components should in a systematic without voilating any fundamental concept of optical communication.
Then analyyze and verify the results step by step.. You will surely get the correct results without any error.

Hope your query has been resolved.
Regards.

[Jojo Mathew]

Hello Asif
This is a reply to your comment as “i think if you have optisystem , the optisystem samples are quit handy for you to study the nature of optical output power from a laser depending on various parameters of the Laser and the input signal. If dont have optisystem samples. you can visit optiwave site for further information.”
I think insted of visiting optiwave site for the information, it can be done by using the optisystem kits.
Regards.

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