spectral Direct detection problem in results

[Eman]

Each chip has a spectral width of 0.8 nm.the rates of 622 Mbps, and 1.25 Gbps for 10 km.At 1550 nm wavelength, the attenuation co-efficient was 0.25 dB/km, and the chromatic dispersion co-efficient was 18 ps/nm-km and the polarization mode dispersion (PMD) co-efficient was 5 ps/p km. The transmit power used was 0 dBm out of the broadband source.The dark current value was 5 nA and the thermal noise co-efficient was 1.8 *10-23 W/Hz for each of the photodetectors.

These the parameters in system.

I have a problem in results.

Attachments:

1. Project2.osd

[Eman]

this the paper

Attachments:

1. Performance-of-OCDMA-systems-with-new-spectral-direct-detection-SDD.pdf

[Damian Marek]

Hey Eman,

You will get a much better BER if you use a low pass filter on the output of the Photodetector PIN component. Use a cutoff frequency of 0.75*Bit rate to extract the signal.

It is usually a better idea to change the Bit rate globally, by double-clicking anywhere on the layout or using the Project Browser in the bottom left corner. This will automatically update the bit sequence generators and also calculate a correct time window for visualizers etc. You will also notice that the low pass filters automatically have a cut-off frequency of 0.75*Bit rate.

[Eman]

hi Damian Marek i made the changes you suggested but result still unreasonable
take a look at it and tell me your suggestion
thanks in advance

Attachments:

1. SDD.osd

[Damian Marek]

The Low Pass Bessel Filters have a cut-off frequency of 0.75*Symbol rate. You should change that for the 0.75*Bit rate, which will cut out a lot more noise. I’m not exactly sure what your application is, but you might want to make sure you are using the gratings correctly in your design. If you are interested in some sort of WDM system, I would think you should use the reflected spectrum from your gratings and not the transmitted spectrum.

Look at the spectrum response of fiber bragg gratings at this webpage:

http://en.wikipedia.org/wiki/Fiber_Bragg_grating

[Eman]

this is the project after modification please take a look at it and tell me if any additional modification can made

Attachments:

1. SDD1.osd

[Roman Ibragimov]

In my opinion, you can decrease lineweight of laser (for example get 0.01 MHz). Also, you need check all parameters in external modulator, maybe wrong bias voltage gets low BER.

[Author]

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