Search Results for 'wdm'

[Karan AhujaSpectator]

I want to add that the integrated semiconductor optical amplifier (SOA) with a reflective electro-absorption modulator (REAM) is a promising candidate for the colorless optical network unit in a wavelength-division-multiplexed passive optical network (WDM-PON), due to its low chirp and wide bandwidth. However, 40 Gb/s operation of REAMs (bandwidth <; 20 GHz) still encounters severe intersymbol interference. Furthermore, Rayleigh backscattering (RB) and discrete reflections cause strong beat noise in WDM-PONs with single-fiber loopback configuration. In this paper, we present two novel techniques based on electrical equalization for a 40-Gb/s single-feeder WDM-PON based on SOA-REAM. The first method is to employ partial-response (PR) signaling and a noise predictive maximum likelihood (NPML) equalizer at the upstream receiver. The other one combines correlative level (CL) pre-coding with partial-response maximum likelihood (PRML) equalization. We experimentally demonstrate a 40-Gb/s uplink of 20 km using a 20-GHz SOA-REAM in a WDM-PON by both PR-NPML and CL-PRML. The results also verify the superiority of PR-NPML over the previously reported equalizers. Moreover, compared with PR-NPML, CL-PRML further improves the system performance. Experiments prove that the tolerance to beat noise and the receiver sensitivity are enhanced by 4 dB and 0.8 dB, respectively, at a bit error ratio of 2 × 10-4.

Here is the link of this paper
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6360172&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D6360172

[Karan AhujaSpectator]

Also DWDM PON architectures are of high interest and are on the way to becoming commercially realized, the bandwidth can be substantially scaled up compared to common PON networks concepts. AWG based structures for MUX/DEMUX applications in WDM-PON networks are ideal, adapting perfectly to PON architectures, allowing cyclic character and are leveraging the state of the art PLC processing techniques. The recent progress of AWG design concepts for DWDM PON architectures and their athermal packaging techniques, now suitable for mass production in low cost manufacturing countries, are discussed. The state of the art reliability performance for industrial and in particular DWDM PON applications are demonstrated. AWG based DWDM PON network architectures are elaborated comparing other existing PON network concepts.

You may refer to this paper in this regard
http://ieeexplore.ieee.org/xpl/login.jsptp=&arnumber=4054038&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D4054038

[Karan AhujaSpectator]

Hi Sam

I would like to mention that the wavelength-division-multiplexed passive optical network (WDM-PON) has been generally regarded as a promising solution to the next-generation access network that will be required to deliver services over 40 Gb/s. However, fiber dispersion often limits the capacity and reach of WDM-PONs. Compared with dispersion compensation fiber, which is bulky and expensive with significant power loss, digital signal processing is a more suitable way to mitigate chromatic dispersion in PONs. Furthermore, expense is a critical concern in the WDM-PON, due to its need for a large number of lasers and a complex wavelength control mechanism. One practical solution is to reuse the downstream (DS) signal as the carrier for the upstream (US) modulation. In this case, the residual DS signal after remodulation can seriously degrade US transmission. In addition, system performance can be deteriorated by the unwanted reflection as uplinks and downlinks share one wavelength. In this paper, we propose using modified duobinary (MD) coding in the DS to improve its dispersion tolerance and reduce the crosstalk between DS and US induced by remodulation and reflection. MD is a correlative level code that can reduce signal bandwidth and achieve DC balance. We demonstrate a 15 km WDM-PON delivering a 40 Gb/s MD-coded signal in the downlink and a 10 Gb/s on-off keying signal in the uplink. Compared with no coding, the maximal allowable extinction ratio of the DS signal (ERd) is improved by 4 dB. Moreover, the reflection tolerance of the uplink and downlink is enhanced by 5 and 4 dB, respectively. In addition, investigations on the use of different equalizers in the DS to further suppress fiber dispersion confirm that the superior performance of nonlinear equalization in MD-coded transmission and that the network reach can be extended to 25 km by a nonlinear decision feedback equalizer.
Hope this will give you an idea.
http://ieeexplore.ieee.org/xpl/login.jsptp=&arnumber=6645106&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D6645106

Thanks

[Fatin Nabilah]

Hello everyone,

How to plot the graph of the maximum gain in the Dual Port WDM Analyzer in Bidirectional Simulation?. As we know, there a multiple iteration when dealing with Bidirectional Optical Fiber. How can we plot the gain graph?

I’m attach my simulation file below.

[burhan num mina llahParticipant]

Hello Mahmoud Ghorbel,

As Hamza ali has already given you an idea how to deal with loop control parameter. Still for your convenience i will try to repeat it that you need to first drag the Loop Control to the Main layout, Connect the output port of the WDM Mux 8×1 to the first Loop Control input port, Connect the first Loop Control output port to the Optical Fiber input port, Connect the output port of the second EDFA Ideal (connected to the Optical Fiber) to the Loop Control input port.
You may refer to these links for further study. I hope this will help.

Lesson 3: Optical Systems — WDM Design

why use loop control in circuit

Regards

Burhan

[Aabid BabaParticipant]

Hello Umer,
As far as your query is concerned i will go with what Duy Le has mentioned. There has been lot of confusion over this but i strongly believe that it is the bandwidth of the bandpass filters in WDM MUX and DEMUX. Still if you feel that it is different from what i have understood then please fell free to share the information. It will be very useful. Thanking you.
Regards

[umer ashraf waniParticipant]

the abstract of the paper goes like this
We successfully demonstrate 40 GB/s 8 channels’ DenseWavelength DivisionMultiplexing (DWDM) over free space optical (FSO)
communication system. Each channel is transmitting 5 GB/s data rate in downstream separated by 0.8nm (100GHz) channel
spacing with 1.8GHz filter bandwidth. DWDM over FSO communication system is very effective in providing high data rate
transmission with very low bit error rate (BER). The maximum reach of designed system is 4000m without any compensation
scheme. The simulation work reports minimum BER for Return-to-Zero (RZ) modulation format at different channels 1, 4, and
8 are found to be 2.32

[Duy Le NguyenParticipant]

Hi umer!
Did you mean the bandwidth of the bandpass filter in WDM Mux and Demux blocks?

[–Participant]

Thank you Damian.
Can I use WDM analyzer to measure the Sideband power? I was trying to do so but couldnot measure the sideband power separately. I tried setting the parameters lower and upper frequency limit of the WDM analyzer such that only the sideband comes withing that limit. The figure of the spectrum is attached. Resoultion bandwidth of WDM analyzerwas set to be 0.05.

Thank you

[Hamza Ali Abbas KhanParticipant]

you May also refer to these papers for the same
http://www.ijser.org/researchpaper/analyses-on-the-effects-of-crosstalk-in-a-dense-wavelength-division-multiplexing-dwdm-system.pdf
http://link.springer.com/article/10.1155/ASP.2005.1593

[Hamza Ali Abbas KhanParticipant]

Hi.
A particular signal can accumulate cross-talk from different elements and channels over the network. Cross-talk can be reduced by using several techniques such as wavelength dilation or filter cascading. In this example, we will investigate the effect of interchannel cross-talk at ADM to a ring network. The project is found in the Interchannel crosstalk at ADM in a ring network.osd file. This network contains 4 nodes that communicate over two channels at 193 THz and 193.1 THz. The bit rate is 10 Gbps. ADMs at each node is modeled by using WDM add and WDM drop components. WDM add and drop components are created by using 4th order Bessel filters. The ring is ended with a ring control component which can circulate the signals around ring for a given number of times. The distance between nodes is 12.5 km and we inserted an ideal amplifier just before node 2 to compensate for the total fiber loss in the ring. Dispersion and nonlinear effects of fibers are disabled to isolate the crosstalk effect.
check the Link this may help you.

Interchannel Crosstalk in Metro Networks

Thanks

[Hamza Ali Abbas KhanParticipant]

Hello.
As dispersion increases effect of four wave mixing decreases. For dispersion 16ps/nm FWM effect reduces but chromatic dispersion increases. At zero dispersion FWM effect more hence fiber having dispersion 4ps/nm is used where FWM effect is less and fiber is called Non-Zero dispersion shifted fiber.Due to equal spacing some FWM components overlap DWDM channels. But in unequal spacing there is no overlapping of DWDM channels and wavelength conversion occurs.
As suggested by Mr Umer you can try reducing the channel spacing. That may help.
Thanks

[Zulia Nurul Karimah]

Hi guys, I would like to ask you some questions.
Here I use modulation formats of CSRZ, NRZ, RZ, RZDPSK and RZDQPSK in each systems based on https://optiwave.com/resources/applications-resources/optical-system-advanced-modulation-formats/
The questions are:
1. I put OTDV after the last MZM to see how the signal are modulated in every format. But I’ve been confused why with CSRZ there’s no transition in every bit.
2. Why in NRZ and RZ there’s a delay for 1 bits in the beginning of transmit signal. Fyi, the information bit that I used is 1011.
3. Can you explain me how RZDPSK and RZDQPSK modulated the signal like that?
4. The comparison between receive signal in every format modulation?

Thank you, hope to see the answers soon 🙂

Another parameter that I used:
-18 channel 1271 to 1611 nm
-CWDM
-FTTH
-Bitrate: 2,5 Gbps
-Power transmit: 7 dBm
-Liniar&nonlinear effects

[Aadil RazaParticipant]

thanks for reply. Actually when i draw BER vs received optical power curve for wdm system, i observed this issue. Do you think optisystem always gives 100% accurate reaults whenever we simulate a system?

[Karan AhujaSpectator]

I want to add that the entire commercial free-space optics industry is focused on using semiconductor lasers because of their relatively small size, high power, and cost efficiency. Most of these lasers are also used in fiber optics; therefore, availability is not a problem. From the semiconductor design point of view, two different laser structures are available: edge emitting lasers and surface-emitting lasers. With an edge emitter, the light leaves the structure through a small window of the active layer and parallel to the layer structure. Surface emitters radiate through a small window perpendicular to the layer structure. Edge emitters can produce high power. More than 100 milliwatts at modulation speeds higher than 1 GHz are commercially available in the 850 nm wavelength range. The beam profile of edge-emitting diodes is not symmetrical. A typical value for this elliptical radiation output pattern is 20 × 35 degrees. This specific feature can cause a problem when the output power has to be coupled efficiently into a fiber and external optics such as cylindrical lenses are used to increase the coupling efficiency. Surface-emitting diodes typically produce less power output. However, the beam pattern is close to being symmetrical or round. A typical value for the beam divergence angle is 12 degrees. This feature is beneficial for coupling light into a (round) optical fiber. Besides discussing basic designs of semiconductor lasers, we will also provide information regarding WDM laser sources and look into Erbium Doped Fiber Amplifiers/lasers that have been discussed recently for use in FSO systems.
Here is link of a pdf
http://cdn.intechopen.com/pdfs-wm/47585.pdf