3 ms·
Prisms for wave division multiplex keep on getting more color channels while speed of light stays the same. What is the physical limit of prisms?
by crb002 10y ago
Prisms for wave division multiplex keep on getting more color channels while speed of light stays the same. What is the physical limit of prisms?
- crispyambulance 10y agoThe prisms aren't the limiting factor. The limiting factor is the fact that the optical signal for any given channel will "widen" in bandwidth when you modulate it. Some modulation schemes are better than others and you can do some tricks like using orthogonal polarizations. At the end of the day, if you modulate a signal at higher and higher rates, it takes more and more bandwidth. That's your real limiting factor.
- mmmBacon 10y agoSort of. We are able to shape these spectra now to improve the spectral efficiency (when using colorless muxing). The next generation of coherent modems will have a 25G granularity and SW will tune the modem to maximize capacity for a given reach. Higher order modulation requires more SNR so this is the real limitation. For relatively short reaches the modulation order will increase. This improves the spectral efficiency. For longer reaches lower order modulation will be needed but the baud rate can increase. We can can however use other wavelength bands like L band to double the capacity. You are already seeing this in new submarine cables.
- mmmBacon 10y agoThere is plenty of BW available in the fiber. A nit, we don't use prisms to combine and separate the colors. We are getting more data in the fiber by increasing the modulation complexity and by making advances in forward error correction. We are seeing FECs now that have 12.3dB gain and are approaching the Shannon Limit.