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Dispersion vs. receiver

Hello,

In our application we use the PMC5346 S/UNI 155 Lite, an ATM User Network Interface chip for 155 Mbit/s. In addition to this component we use a 1310nm laser module to convert the STM-1 electrical data stream into an OC3 optical data stream and vice versa.

Since a few months our customer is also using non standard Single Mode Fiber (SMF) in combination with a 1550nm laser. Due to his fiber choice we now have to deal with chromatic dispersion. I am investigating the impact of the dispersion and the maximum amount of dispersion that is allowed by the receiver of the PMC5346.

So I am looking for the tolerances on the pulse width of the NRZ signal provided to the receiver of the PMC5346. Due to the dispersion a logic "1' pulse becomes wider, a logic '0' pulse becomes smaller.

I didn't find this information on the web, but I hope someone can help me with some suggestions or tips.

Thank you in advance & kind regards,

Bert

Reply to
Bert
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You can correct for chromatic abberations using an optical delay line. "All" you have to do is collimate light coming out of your dispersing fiber, sent the light to a diffraction grating, image the grating on a mirror and send it back. By varying the distances between the grating and the focussing lens, you can change the phase between wavelength components, thus compensate for dispersion. I just googled for a better explanation on "optical delay line", but that does not seem to give what you want. An explanation of a rapid scanning optical delay line can be found in G.J. Tearney et al, "High-speed phase- and group-delay scanning with a grating-based phase control delay line," Optics Letters

24, 1221-1223 (1999). Of course, you don't want to rapid scan, but if you don't run the galvanometer, you have what you want. Instead, you can use a standard mirror, which is obviously much cheaper.
Reply to
Barry Cense

Bert,

I didn't read this earlier, so maybe this answer is moot:

For a 155Mb/s connection, I don't think that chromatic dispersion will be very influential at all. At 2,5 and 10Gb/s, it becomes an issue, and will limit your transmission length to about 80km or so. This is where dispersion compensation modules come in handy. And will only be applicable for transmission in the 1550nm wavelength window.

You mention using a 1310nm laser, makes me think that you use this single mode fiber for not more than 10-20 km, right. If not, you will need a re-design of your fiber link based on 1550nm optics. I can help you with this if needed.

cheers, Erik

(PS I may also be reached at _wegvoorspam snipped-for-privacy@tmns.com)

Bert wrote:

Reply to
Erik

Bert,

I didn't read your post earlier, so maybe this answer is moot:

For a 155Mb/s connection, I don't think that chromatic dispersion will be very influential at all. At 2,5 and 10Gb/s, it becomes an issue, and will limit your transmission length to about 80km or so. This is where dispersion compensation modules come in handy. And will only be applicable for transmission in the 1550nm wavelength window, because this is where long-distance transport is done in the first place.

You mention using a 1310nm laser in the PMC5346; it makes me think that you use this single mode fiber for not more than 10-30 km, right?

If you need longer distances, you will want to do a re-design of your fiber link based on 1550nm optics from both sides. I can help you with this if needed.

cheers, Erik

(PS I may also be reached at _wegvoorspam snipped-for-privacy@tmns.com)

Bert wrote:

Reply to
Erik Radius

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