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In reply to: FTTX
Hello All,
I agree with Dhiman that With the recent advancements in access networks the TDM PON, like Ethernet passive optical network (EPON) and Gigabit Passive optical network (GPON), are now widely used as optical access network solutions to distribute reasonably high bandwidths to the customers through an optical fiber network infrastructure. Researchers are aiming at optical access network concepts known as hybrid WDM/TDM access passive optical networks.
In recent times we have reached various techniques and components of the network that are designed to achieve high data rate transmission to large bandwidth such as tuneable optical add/drop multiplexer (OADM) , colorless ONU , selfhomodyne and differential coding , a reflective semiconductor optical amplifier (SOA) and Bragg reflectors. The passive optical networks are constituted of a centralized
OLT located in the central office and a number of ONUs located at the users premises to some distance away from the OLT.
I hope this will be useful.
RegardsIn reply to: best laser for FSO
Hello everyone,
As mentioned by other forum members about this topic being discussed already i would like to add here that the bandwidth of a Multiplexer or a demultiplexer refers to the bandwidth of the filters used for each channel of the implemented WDM system, whereas the bandwidth in some other components such as amplifiers is the bandwidth of operation of that specific component. There was a lot of confusion regarding this topic and as mentioned by naazira no conclusion was reached. I would suggest you to look at the links and go through them. May be these can help you.I Hope this will be helpful in some or the other way.
RegardsIn reply to: best laser for FSO
Also i want to add that Coarse WDM (CWDM) in contrast to conventional WDM and DWDM uses increased channel spacing to allow less sophisticated and thus cheaper transceiver designs. To again provide 16 channels on a single fiber CWDM uses the entire frequency band between 2nd and 3rd transmission window (1310/1550 nm respectively) including both windows (minimum dispersion window and minimum attenuation window) but also the critical area where OH scattering may occur, recommending the use of OH-free silica fibers in case the wavelengths between 2nd and 3rd transmission window shall also be used. Avoiding this region, the channels 31, 49, 51, 53, 55, 57, 59, 61 remain and these are the most commonly used.
I hope this would help.
You can further refer to this link http://www.fiberoptic.com/adt_dwdm.htmThanks
In reply to: best laser for FSO
Hello Umer,
we know that the amount of bandwidth allotted to each channel in a communications system that transmits multiple frequencies such as fiber optics and it is measured as the spacing between center frequencies (or wavelengths) of adjacent channels and this is what we call chnnel spacing. For your convenience you can refer to http://www.pcmag.com/encyclopedia/term/39575/channel-spacingConventional WDM systems provide up to 16 channels in the 3rd transmission window (C-band, around 1550 nm) of silica fibers.
Dense WDM (DWDM) uses the same 3rd transmission window (C-band) but with denser channel spacing. Channel plans vary, but a typical system would use 40 channels at 100 GHz spacing or 80 channels with 50 GHz spacing. Some technologies are capable of 25 GHz spacing (sometimes called ultra dense WDM). New amplification options (Raman amplification) enable the extension of the usable wavelengths to the L-band, more or less doubling these numbers.In reply to: Q FACTOR
Hello.
I would like to mention that there are various ways to increase the quality factor for various system designs. First you need to specify for what application you are designing your system.
As mentioned by Mr Umer you can increase power to increase the quality factor but it has has an adverse effect on the channel as non linearities come into play but you can increase the transmission power.
I would provide you some links which you could refer to. I hope these will help.Thanks
http://www.ijltet.org/wp-content/uploads/2013/08/4.pdfTopic: Error WDM PON sample
In reply to: Q FACTOR
increase power
depends upon data rate
bw of multiplex
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjtyYrn6M7MAhXHJI4KHatwCPoQFggoMAE&url=http%3A%2F%2Fwww.issr-journals.org%2Flinks%2Fpapers.php%3Fjournal%3Dijisr%26application%3Dpdf%26article%3DIJISR-14-301-03&usg=AFQjCNFq5reRBxXmcjAWxXxd0eJ4Zia2QA&sig2=XBDUgpEACyKBkTx_dUN3jA
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjtyYrn6M7MAhXHJI4KHatwCPoQFggxMAI&url=http%3A%2F%2Foptiwave.com%2Fresources%2Fapplications-resources%2Foptical-system-16-channel-wdm-system-design%2F&usg=AFQjCNEyZq2mPZDpY7lIe2xAxC56d9pFww&sig2=cIvoY4n_YVpblBH8FHl5qA
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwjtyYrn6M7MAhXHJI4KHatwCPoQFgg4MAM&url=http%3A%2F%2Fwww.ciscopress.com%2Farticles%2Farticle.asp%3Fp%3D30886%26seqNum%3D5&usg=AFQjCNEfhAYMaiGnO2FQVPbDgWy3dStH8g&sig2=gxA3_fm2tO1EO96JOuHkhQ
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwjtyYrn6M7MAhXHJI4KHatwCPoQFghKMAY&url=http%3A%2F%2Fwww.ijltet.org%2Fwp-content%2Fuploads%2F2013%2F08%2F4.pdf&usg=AFQjCNHeaC6bKig_RPBJtTxkDJmbw-JAWQ&sig2=DyO-nPL10e4-HC9hnfvZBw
https://books.google.co.in/books?id=8IcNZu1smOwC&pg=PA54&lpg=PA54&dq=wdm++with+high+quality+factor&source=bl&ots=5ugGXyKW60&sig=dreBv4HC8UoPeOheDIoDooKDPCE&hl=en&sa=X&ved=0ahUKEwjtyYrn6M7MAhXHJI4KHatwCPoQ6AEIVjAIIn reply to: best laser for FSO
Hello Umer Ashraf Wani.
You could use 10 Ghz as well. we have had a number of discussion over wdm MUX bandwidth over here but a conclusive statement could not be reached as to should the BW of WDM-MUX be n x10Ghz , where n is the no. of channels.
Links to few relevant discussions: https://optiwave.com/forums/topic/bandwidth-parameter-for-each-component/
About channel spacing, i believe you need to just change the wavelength to modify the channel spacing, or is it something else that you are asking?
Best Wishes
Naazira BadarIn reply to: best laser for FSO
I am not sure about channel spacing. You may refer to few threads here that mention channel spacing be it equal channel spacing or unequal channel spacing.
Here are few links. You may refer to them
http://link.springer.com/chapter/10.1007%2F978-1-4020-8741-7_1#page-1
https://www.researchgate.net/publication/261320396_Duobinary_modulation_format_and_unequal_channel_spacing_integration_to_suppress_four-wave_mixing_crosstalk_in_WDM_systems
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5876926&abstractAccess=no&userType=instAlso go through these threads https://optiwave.com/forums/topic/bande-width/
Hope this will be useful.
Regards
Burhan
In reply to: best laser for FSO
Hello Umer,
I have already replied to your query in other thread. Still for your convenience i will repost it here. In addition to that, i would suggest you to use 10 to 20 GHz bandwidth not 80 Ghz.
Well as far as your query regarding bandwidth of Multiplexer is concerned, i would like to mention that the bandwidth of a Multiplexer or a Demultiplexer actually refers to the bandwidth of the filters used for each channel of the implemented WDM system whereas the bandwidth in some other components such as amplifiers is the bandwidth of operation of that specific component.
i will suggest you to increase the bandwidth from 10 GHz which is a default value to 20 GHz and check for the results. In my opinion, When the bandwidth is reduced, many signals with higher frequencies get distorted as they fall out of the pass band of the filter. This means they cannot be correctly detected at the receiver. This is the basic and complete theoretical explanation of why the bandwidth reduction causes system degradation.
I hope this will be helpful. This has been already discussed previously. I will suggest you to go through these links.Regards
Burhan
In reply to: interfacing
Hello Umer,
Well as far as your query regarding bandwidth of Multiplexer is concerned, i would like to mention that the bandwidth of a Multiplexer or a Demultiplexer actually refers to the bandwidth of the filters used for each channel of the implemented WDM system whereas the bandwidth in some other components such as amplifiers is the bandwidth of operation of that specific component.
i will suggest you to increase the bandwidth from 10 GHz which is a default value to 20 GHz and check for the results. In my opinion, When the bandwidth is reduced, many signals with higher frequencies get distorted as they fall out of the pass band of the filter. This means they cannot be correctly detected at the receiver. This is the basic and complete theoretical explanation of why the bandwidth reduction causes system degradation.
I hope this will be helpful. This has been already discussed previously. I will suggest you to go through these links.Regards
Burhan
In reply to: best laser for FSO
can u mention the upper power limit
also i have one more query regarding Band width of WDM and channel spacing
If i am simulating an 8 channel WDM system with frequency varying from 193.1 to 193.8, what should be the BW of Multiplexr? 10Ghz r 80Ghz
and how can i simulate the same system for different channel spacing. kindly let me know.
regards
umer ashrafIn reply to: interfacing
i have one more query regarding Band width of WDM and channel spacing
If i am simulating an 8 channel WDM system with frequency varying from 193.1 to 193.8, what should be the BW of Multiplexr? 10Ghz r 80Ghz
and how can i simulate the same system for different channel spacing. kindly let me know.
regards
umer ashrafIn reply to: Multibeam FSO
Hello Marvi,
I would like to mention that multibeam FSO network has provided a significant improvement in the link distance, received optical power, geometrical loss, and scalability. The network performance has been analyzed, and the study concludes that a maximum channel spacing beyond 0.4 nm is applicable for this network. The power receiver sensitivity difference of the receiver for different wavelengths at a BER of 10−9 was noted to be a small value, which is approximately less than 1 dB. Meanwhile, in terms of scalability, four users can access data each at 1.25 Gb/ss, which is considered suffi- cient compared to conventional multibeam technique accessing data to only one EU. The hybrid WDM/multibeam FSO network can be a good candidate to solve the last mile problem and the rapid increase in capacity demand without requiring
new FSO transceivers. At the moment, the evaluation is going on for a real-time system operating in heavy rain as compared to simulation presented here. In the future, increasing the capacity of the hybridWDM/multibeam FSO network can be studied and implemented to reach up to 32 channels.Refer to this paper http://download.springer.com/static/pdf/356/art%253A10.1007%252Fs11107-014-0482-y.pdf
Hope this will helpRegards
Burhan
In reply to: Dqpsk wdm
Also try to go through this paper too.
https://www.researchgate.net/publication/3293389_Impact_of_nonlinear_phase_noise_on_direct-detection_DQPSK_WDM_systemsIt mentions that the performance degradation of differential quadrature phase-shift keying (DQPSK) wavelength-division-multiplexed (WDM) systems due to self-phase modulation (SPM)- and cross-phase modulation (XPM)-induced nonlinear phase noise is evaluated. The XPM-induced nonlinear phase noise is approximated as Gaussian distribution and summed together with the SPM-induced nonlinear phase noise. Here 10-Gb/s system is demonstrated, whose walk off length is larger than 40-Gb/s systems’, are more sensitive to XPM-induced nonlinear phase noise than 40-Gb/s systems. Furthermore, DQPSK WDM systems show lower tolerance to both SPM- and XPM-induced nonlinear phase noise than differential phase-shift keying WDM systems.
Hope this is what you are looking for.
Regards
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