Search Results for 'wdm'

[jyoti rainaSpectator]

hi dhiman sir..thanx for replying.
I hv taken an example from the optiwave samples for wdm systems.. it had 16 channels.. i changed it to 4 channels so that i could start frm basic..
when changing to 4 channel i got this waveform which is different from the one i got when i simulated the sample example..
now i ll try changing the filter as suggested by damian sir.. i hope it works well.. anyway thanx a lot

[jyoti rainaSpectator]

hi Damian sir.. thanx fr replying to my query.
what is the thing i hv to do to set them right.. do i hv to change filter setting of wdm mux demux only or the all filters frm the receiver side..i m also using low pass bessel filtr with order 4..
i ll try to check and see this..anywyz thanx agn fr the kind help.

[Ranjeet KumarParticipant]

Hi Aasif sir,
WDM wavelengths are positioned in a grid having exactly 100 GHz (about 0.8 nm) spacing in optical frequency, with a reference frequency fixed at 193.10 THz (1552.52 nm). The main grid is placed inside the optical fiber amplifier bandwidth, but can be extended to wider bandwidths. Today’s DWDM systems use 50 GHz or even 25 GHz channel spacing for up to 160 channel operation.
According to you “lambda= velocity of light/frequency=3000000000/193.1THz=1553.6nm (approx) but when changed laser frequency units from THz to nano meter(nm) …. to my surprise it shows 1552.524381149663nm”
The difference is nearly 0.8 nm.
It is due to channel spacing because by default channel spacing is 100 ghz(0.8 nm).
http://www.fiberoptic.com/adt_dwdm.htm

[Ranjeet KumarParticipant]

Hi Fayiqa ma’m
All the TWDM ONTs must be colorless. The ONT transceiver must be able to tune to the correct wavelengths in upstream and downstream during end-user provisioning.
We can use a variety of techniques to control the wavelength in the upstream direction from the ONT to the OLT. Temperature is the primary parameter of control. all TWDM ONTs must be colorless. The ONT transceiver must be able to tune to the correct wavelengths in upstream and downstream during end-user provisioning.

Operators can use a variety of techniques to control the wavelength in the upstream direction from the ONT to the OLT. Temperature is the primary parameter of control.
n the long-term, it is hoped that photonic integrated circuits will provide other economical solutions to wavelength control.

In the downstream direction, thermo-controlled thin-film filters can be integrated into the ONT receiver to allow tuning. Photonic integrated circuits may provide a future solution.

[Ranjeet KumarParticipant]

Hi Sahil singh,
Yeah, i am sure about changing the order bandwidth and cutoff frequency of different filter at the receivers end to get better results as per our requirement of design in WDM system.
usually changing using filter order of 3 or 4 gives better results then using order 2.

[Zakarya SaidiParticipant]

Hi Ranjeet Kumar,
Your osd file attached is 8 channel RZ wdm system and not CSRZ. please check it again and let me know if I’m wrong.

Thanks

[Ranjeet KumarParticipant]

Hi Jyoti,
For simple Wdm system we could use EDFA amplifiers in addition to this we should use symmetric compensation technique to get better results as it compensate the losses in fiber caused by dispersion.
In long haul DWDM sytsem we should use hybrid (EDFA+ Raman) amplifier for better results.
We should use different amplifiers according to requirement as both amplifiers have advantage and disadvantages as

Advantages of EDFA
EDFA has high pump power utilization (>50%)
Directly and simultaneously amplify a wide wavelength band (>80nm) in the 1550nm region, with a relatively flat gain
Gain in excess of 50 dB
Low noise figure suitable for long haul applications

Disadvantages of EDFA
Size of EDFA is not small
It can not be integrated with other semiconductor deviecs

Advantages of Raman amplifier
Variable wavelength amplification possible
Compatible with installed SM fiber
Can result in a lower average power over a span, good for lower crosstalk and Very broadband operation may be possible

Disadvantages of Raman amplifiers
High pump power requirements, high pump power lasers have only recently arrived
Sophisticated gain control needed
Noise is also an issue

[Ranjeet KumarParticipant]

Hi Jyoti Raina,
I AGREE to points of Dhiman as he said Your results are as expected, because when the Q-factor will go high the BER will definitely become low. and BER of near to value 1 is not acceptable.
BER of value greater than 10^-07 is not acceptable .
I will also ask you to reduce transmitter power because 10 dbm is very high, You should reduce transmitter power to upto 4 dbm.
Here i am attaching 32 channel CSRZ WDM SYSTEM for long haul communication system.
Sometimes we could change the filter order and bandwidth to get better results.
Hope my response could help you.

[Ranjeet KumarParticipant]

HELLO ZAKARYA,
For wdm mux we could have the following parameters values as:
Frequency 193.1
Frequency spacing 100
Bandwidth 100
Insertion loss 0
Depth 100
Filter type Gaussian
Filter order 2

While for WDM demux we should have following parameters values as:
Frequency 193.1
Frequency spacing 100
Bandwidth 100
Insertion loss 0
Depth 100
Filter type Gaussian
Filter order 4

Here i am attaching 8 channel CSRZ WDM SYSTEM.

[Sanjeev kumarParticipant]

Hello friends
As where as i concerned to the above posted matter. i always saw that whenever we combine the data like in DWDM or SCM we use the concept of power combiner and power splitter at receiver whereas fork is always used to analysis for testing reason like what signal the component is actual generating so that it could be analysed at the receiver whether the sent signal is matching with the transmitter signal(analysed suing fork) or not. thank you

[jyoti raina]

helo evryone..
i am facing a prblm.. i dont know why my mux’ed signal is like this..it is very haphazard and not so clear…i m designing a four channel wdm system.. i hv taken a sample frm the example folder and it was for 16 channel wdm system..thr i checked the waveform was clear havng 16 distinct signals..bt nw whn i changd it to 4 channel wdm..the ber got betr bt now this happens.
check the picture plz and help plz..
thanx in advance

[Zakarya SaidiParticipant]

Hi Naazira Badar and FAYIQA NAQSHBANDI,

the problem is not increase or decrease the wdm bandwidth for getting better results (no rule for that). From some of my experiences, this variation depends on the modulation scheme used and also the length of the fiber…

with Regards

[Naazira BadarParticipant]

Hi all..
I have checked my results on values less than 10 Ghz , and results were seen to be improving.
I had checked on 8 channel wdm system. I’m still not sure how this bandwidth parameter of wdm mux/demux affect performance.
It would be really good if this thing gets clear.

Regards
Naazira.

[FAYIQA NAQSHBANDISpectator]

HELLO ZAKARYA SAIDI..
Well you have made an important point here..you know it was discussed in some post regarding selection of bandwidth of WDM multiplexer and it was mentioned there the performance gets better with increasing the bandwidth but explanation was given on basis of simulation..the theoretical reason was not mentioned..here i would like to ask u if u can share that paper where bandwidth is set based ob bit rate…

it will be highly helpful..
Thanks & regards

[Zakarya SaidiParticipant]

HI Fayiqa,
Thanks for your suggestions. Actually I have seen a paper and it mentions that the bandwidth of wdm multiplexer depends of the modulation format inserted and the bit rate. furthermore, it sets the bandwidth for a bit rate 4*10 gbit/s (4 channels) like
-for RZ modulation B=4*bitrate
-for NRZ modulation B=2*bitrate
-for CSRZ,DRZ and MDRZ B=16GHZ
My question is how does he get this ??
I did the same simulation but I got bad eye diagram in the case of RZ and CSRZ.