OFDM

[SAM SAM]

Dear all
Can you help me in implementing an OFDM GPON system with data rate in excess of 40 Gbps.

Best Regards

[Aabid Baba]

Hello Sam,
As far as your query about implementation of PON system is concerned, I would suggest you to go through optisystem sample folder where number of examples are shown implementing PON systems. However I am not sure about the data rate you want.You may need to upgrade it yourself.
For your convenience I am attaching links of few papers that have implemented it using optisystem.I would suggest you to go through these papers to gain some idea about the implementation of PON systems.

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6645106
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4054038
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6360172

I hope this would be helpful to you.
Regards

[Hamza Ali Abbas Khan]

Hi.

I would suggest you to look for the optisystem sample files. You can find the example “OFDM Modulator” in those sample folders. There is also another sample named “OFDM demodulator” that has the exact same implementation.
And as fas as theoretical aspect of the implementation is concerned i agree with karan ahuja that OFDM has the ability to transmit information with high data rates which has made it popular. OFDM has been used in many different applications in the RF domain
such as digital audio broadcasting (DAB), digital video broadcasting (DVB), and Wireless Local Area Networking (WLAN). OFDM was introduced to
optical domain in 2005, and has since been studied and investigated in two main techniques classified according to the detection scheme. The first technique is the direct detection optical OFDM (DDOFDM) and the second technique is the coherent optical OFDM (CO-OFDM). A direct detection optical OFDM aims for simpler transmitter or receiver than CO-OFDM for lower costs. DD-OFDM has an advantage that it is more immune to impulse clipping noise. Coherent Optical OFDM (COOFDM) is the next generation technology for optical communications since it integrates the advantages of both coherent systems and OFDM systems. COOFDM provides linear detection and high spectral efficiency. The CO-OFDM system has the ability to overcome many optical fiber restrictions such as Chromatic Dispersion (CD) and Polarization Mode Dispersion (PMD).

I hope this would help.
Thanks
Regards

[Karan Ahuja]

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

[Karan Ahuja]

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 Ahuja]

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

[Aabid Baba]

Hello Karna,
Thanks for sharing the information. It is indeed very very helpful as far as WDM PON systems providing 40 Gbps data rate are concerned. Thanking you.

Regards

[burhan num mina llah]

Hello Sam Sam,

I would suggest you to go through the links
http://ieeexplore.ieee.org/xpl/login.jsptp=&arnumber=6360172&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D6360172
http://ieeexplore.ieee.org/xpl/login.jsptp=&arnumber=4054038&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D4054038
http://ieeexplore.ieee.org/xpl/login.jsptp=&arnumber=6645106&url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D6645106

Hope these will be beneficial to you.

Best Wishes

Burhan

[Aabid Baba]

Hello everyone,
Thank you for sharing these links. These may prove to be very helpful for Sam. And I want to mention here that I have already seen some papers which have achieved 40 Gbps data rate for these PON systems. They have made use of externally modulated Continuous wave lasers and also I have noticed that instead of Fabry parot filters , they have used Fiber Bragg grating as filter because of the response of these finer Bragg gratings. I hope this will definitely help Sam .

Regards

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