Search Results for 'wdm'

[Rajguru M. MohanParticipant]

Hi,
As we know studies have been carried out on NG-PON2 enabling technologies, such as 40 G TDM-PON,wavelength division multiplexed PON (WDM-PON), time and wavelength division multiplexed PON (TWDM-PON) and orthogonal frequency division multiplexing PON(OFDM-PON).
And among all these technologies, TWDM-PON has beenselected as the best candidate for NG-PON2 because itsupports backward compatibility, flexibility and static sharing.

At the OLT side, a set of laser diodes such as distributedfeedback (DFB) laser diodes operating at different wave-lengths serve as downstream laser sources, followed by aWDM for multiplexing.
Therefore, ONU must contain tunable trans-mitters and receivers devices. A tunable filter at thereceiver is used to select or tune to any of the fourdownstream wavelengths. In case of upstream wave-lengths, the tunable laser is used to provide colorlessONU (free operation wavelength) to enable easier networklaying and maintenance.
The TWDM-PON ONU tunable transmitter is used totune its wavelength to any of the upstream wavelengths.
any techniques have been developed as candidates ofupstream laser source, including spectral slicing of broad-band sources, remote reflective modulators, and injectionlocking. The most common lasers for upstream lasersource are the directly modulated Fabry-Perot laser diode(FP-LD) and the reflection semiconductor optical amplifier(RSOA.
n addition to RSOA and FP-LD laser sources, there areother lasers such as DFB laser with temperature control(TC), DFB laser with partial TC multi-section distributedBragg reflector laser (electrical control) without cooling,external cavity laser (ECL) with mechanical control with-out cooling, and ECL with thermo/electro/piezo/magneto-optic control without cooling.

Thanks,

[Rajguru M. Mohan]

Hi,
I want to know about application of wideband travelling wave semiconductor optical amplifier in optical communication.
Here i am uploading image of OFDM-WDM PON in which for the uplink, the wideband travelling wave semiconductor optical amplifier (WBTW-SOA) is used to simulate the traveling wave SOA that is based on an identical hidden edge SOA. A transmitter source Tx and CW laser source are coupled by using an optical coupler and the output is applied to WBTW-SOA. The output signal of WBTW-SOA will be sent via the uplink of SMF. Before reaching the PD at the receiver side, EDFA is used to amplify the signal.

Now, i Want to know why wideband travelling wave semiconductor optical amplifier is being used in this design.
What is its functions?

Please explain.

Thanks and regards,
Rajguru

[love kumar]

hi all..

can any one tell me how we can measure crosstalk for DWDM system iin optisystem 14 version ..

[Rajguru M. MohanParticipant]

Hi,
Frequency and phase modulation can still be used in optical communication systems in indirect ways to deal with noise and distortion.
For example, signals can be frequency- or phase-modulated onto a subcarrier before intensity modulating the optical carrier.
Noise performance of an analog signal will be enhanced in addition to the reduction of cross-modulation in frequency-division multiplexing strategies.
In optical fiber is signal distortion due to multiple light paths, or modes, having different distances over the length of the fiber. When light is emitted by a source, the photons (light particles) do not all travel the exact same path.
olarization mode dispersion (PMD) is caused by asymmetric distortions to the fiber from a perfect cylindrical geometry.

WM can be compared to the intermodulation distortion in standard electrical systems. When three wavelengths (λ1, λ 2, and λ 3) interact in a nonlinear medium, they give rise to a fourth wavelength (λ 4), which is formed by the scattering of the three incident photons, producing the fourth photon. This effect is known as four-wave mixing (FWM) and is a fiber-optic characteristic that affects WDM systems.

Thanks

[Duy Le NguyenParticipant]

Hi Rajguru!
Can i ask one question? I’m studying about OFDM-WDM system so I’m making a project – 4QAM Direct detecter OFDM WDM with 16 channels. The results from 1st channel to 10th channel seem ok. But from 12-16th channel, the results aren’t good.
What parameter i should change?

Thanks and regards.

[Rajguru M. MohanParticipant]

Hi Ankita,
As we have two types of scattering losses. They are linear scattering and nonlinear scattering.
In linear scattering, attenuation occurs when optical power is transferred from one mode to another keeping frequency unaltered.
There are two categories in linear scattering. They are Rayleigh scattering and Mie scattering.
Rayleigh scattering is the main loss mechanism in the visible range, it is linear scattering of light at scattering centers which are much smaller than the wavelength of the light. Under such circumstances, the scattering occurs with amplitudes which are proportional to the in-coming amplitude, to the fourth power of the inverse wavelength
It is proportional to the fourth power of the operating wavelength.
Rayleigh scattering loss can be minimized by choosing longest possible operating wavelength.
If the size of the defect is greater than one-tenth of the wavelength of light, the scattering mechanism is called Mie scattering.
Non linear scattering occurs when frequency is changed during optical power transfer. The two types of nonlinear scattering are stimulated Brillouin scattering and stimulate Raman scattering. Stimulated Brillouin scattering is a cause of concern in long distance systems, in wavelength division multiplexing (WDM) systems and remote pumping of an erbium doped fiber amplifier (EDFA) through a separate optical fiber. Stimulated Raman scattering creates problems in wavelength division multiplexing (WDM) systems.

Thanks

[Rajguru M. MohanParticipant]

Hi Burhan ma’m
You should check out the CW laser power as being suggested by Dhiman by increasing the laser power to few dbm.
You should Check for Wdm mux bandwidth , filter order if you are not using ideal mux.
You should also vary the channel spacing by varying the frequency of laser, because according to TIU-T, the standard channel spacing are for WDM system are 25 ghz, 50 ghz, 75 ghz and 100 ghz, 200 ghz, 1 thz .
Check the output at different ports in the design.

You could also Vary no. loops of fiber because for small laser power WDM system gives no results at very large transmission length.
Seeking your response.

Thanks and regards
Rajguru

[Rajguru M. MohanParticipant]

Hi Dhiamn,
As we know WDM is the current favorite multiplexing technology for long-haul communications in optical communication
networks since all of the end-user equipment needs to operate only at the bit rate of a WDM channel, which can be chosen
arbitrarily, e.g., peak electronic processing speed. Hence, the major carriers today all devote significant effort to developing
and applying WDM technologies in their businesses.
Recent research interests in WDM networks include network
control and management, fault management, multicasting,
1818 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 18, NO. 10, OCTOBER 2000
physical-layer issues, IP over WDM, traffic grooming, and optical
packet switching, just to name a few.
In a wavelength-routed WDM network, a control mechanism is needed to set up and take down all-optical connections.
Studies have been conducted to examine different approaches to
protect WDM optical networks from single fiber-link failures.

And many issues and challenges in WDM system must be studied.

[Rajguru M. MohanParticipant]

Hi,
I have links which help you get more ideas about TWDM POn:
http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6289432
https://www.researchgate.net/publication/257774133_Key_technologies_and_system_proposals_of_TWDM-PON
https://www.osapublishing.org/jlt/abstract.cfm?uri=jlt-31-4-587

GPON WDMPON & TWDMPON

https://advanceseng.com/electrical-engineering/flexible-twdm-pon-wdm-overlay-converged-services/
http://www.journals.elsevier.com/optical-fiber-technology/most-downloaded-articles/

Thanks

[Duy Le Nguyen]

Hi everyone!

I’m making the OFDM WDM project. And when i’m trying to figure BER vs SNR, I realize we can’t get BER = 10e-012 because the limit of sequence lenght is 2^30 bits. But in some paper use Optisystem for simulation , I see they can get BER with wide change (example: 10^-2 to 10^-12). So how can I do that?
If you have time please answer me.

Thanks and regards.

[Rajguru M. MohanParticipant]

Hi Jyoti,
Now i would like to share advantage and disadvantage of EDFA:
Characteristics of EDFAs (advantages):
High power transfer efficiency from pump to signal power (> 50%).
Wide spectral band amplification with relative flat gain (>20 dB) – useful for
WDM applications.
Saturation output > 1 mW (10 to 25 dBm).
Gain-time constant long (>100 msec) to overcome patterning effects and intermodulation
distortions ( low noise).
Large dynamic range.
Low noise figure.
Polarization independent.
Suitable for long-haul applications.
Disadvantages of EDFAs:
Relatively large devices (km lengths of fiber) – not easily integrated with other
devices.
ASE – amplified spontaneous emission. There is always some output even with
no signal input due to some excitation of ions in the fiber – spontaneous noise.
Cross-talk effects.
Gain saturation effects.

[Rajguru M. MohanParticipant]

Hi Tanveer,
What exactly do you want to design?
What is its applications?
Are you want to design Hybrid ring and bus wdm architecture?
Please specify the design you really want to design.

Seeking your response.

[Rajguru M. MohanParticipant]

Hi albaity,
As the effective area of the fundamental mode is a measure of the area over which the energy in the electric field is distributed.
This parameter is important for DWDM applications.
We know the effective area of a single mode optical fiber is obtained by this relation :

A eff= pi * W2( lambda )
Typical single-mode fibers, as used e.g. for optical fiber communications,
have effective mode areas of the order of 100 μm2.
Large mode area fibers have several times higher mode areas, sometimes even above 1000 μm2.
On the other hand, there are some photonic crystal fibers with mode areas below 10 μm2.

According to optiwave component library pdf file the effective area of fiber is chosen to 80 μm2.
And it is fixed defaukt value.
I think this value is best.

Seeking your response.

[Rajguru M. MohanParticipant]

Hi Love kumar,
Thank you so much for such valuable information.
I have read both papers, both are useful and important specially the second one:
Time- and Wavelength-Division Multiplexed Passive Optical Network (TWDM-PON) for Next-Generation PON Stage 2 (NG-PON2) of
JOURNAL OF LIGHTWAVE TECHNOLOGY.
By reading this we get valuable information about time- and wavelength-division multiplexed passive
optical network (TWDM-PON), tunable receiver, tunable transmitter.

I want to share some important information about TWDM to all of you :
Among all of the proposals for different technologies of NGPON2, TWDM-PON
has attracted the majority support from global vendors and was
selected by the FSAN community in the April 2012 meeting as a
primary solution to NG-PON2. TWDM-PON increases the aggregate
PON rate by stacking XG-PONs via multiple pairs of
wavelengths. An XG-PON system offers the access rates of 10
Gb/s in downstream and 2.5 Gb/s in upstream. A TWDM-PON
system with four pairs of wavelengths is able to provide 40 Gb/s
and 10 Gb/s in downstream and upstream, respectively. Each
TWDM-PON ONU can provide peak rates up to 10 Gb/s downstream
and 2.5 Gb/s upstream. This meets the rate requirements
of NG-PON2.
Hence TWDM is most important technologies for NGPON2.

Thanks

[Rajguru M. MohanParticipant]

Hi Fadil Paloi,
First of all i suggest you to use symmetrical no. of channels like- 2,
4, 8, 16, 32, 64 and so on.
Because in all the design i have seen suggest to use symmetrical
number of channels.
As we also know that non-linearities effects increases as data rate increases.
Also dispersion and other losses increases.
So, lowering of q-factor and increament of BER is expected to occur.

I suggest you to use some advanced modulation formats like csrz, drz, mdrz and dpsk,
because it supports high data rate and long haul transmission.

Here i am uploading 32 channel CSRZ wdm system at data rate of 40 gbps.
Also use dispersion compensation techniques namely pre, post or symmetrical.
According to me i symmetrical dispersion compensation techniques is best of all three.