Hello, everyone!
Today, I'd like to share with you a new technology in the optical transmission field: superchannel technology.
A superchannel is an optical channel with a larger bandwidth that binds multiple subcarriers on the WDM side for unified transmission.
The superchannel technology is currently used in scenarios of 37.5 GHz wavelength spacing, under which the cascading of multiple ROADM boards brings a large filtering penalty and therefore guard bands need to be added for normal signal transmission.
Related Terms
Subcarrier: A signal with a single-wavelength spectrum width of 37.5 GHz, 50 GHz, or other values.
Guard band: An idle spectrum added outside of an edge subcarrier to reduce the filtering penalty of the edge subcarrier. The guard band size varies depending on the line modulation formats.
Technology
The superchannel technology uses the multi-subcarrier mode to convert a high-speed baseband data signal into multiple low-speed signals and to modulate these signals into multiple subcarriers. These subcarriers are then combined into a larger-bandwidth optical channel on the WDM side for unified signal transmission.
So, using the Flexible Grid technology, the superchannel improves the spectral efficiency, increases the system transmission capacity, and reduces the penalty in filter cascading.
Application Example
When the spacing between Flexible Grid wavelengths is 37.5 GHz, the cascading of multiple ROADM boards introduces a large filtering penalty. Therefore, guard bands need to be added for normal signal transmission.
Furthermore, if wavelengths are separately used for signal transmission, guard bands need to be added for each and every wavelength.
With the superchannel technology, five wavelengths can be transmitted over a total bandwidth of 200 GHz. However, when the wavelengths are separately used, only four wavelengths can be transmitted simultaneously.
Usage Guidelines:
The subcarriers of a superchannel must share the same modulation format, source node, sink node, and path.
Guard bands need to be added on both sides of a superchannel. If there are adjacent supperchannels, guard bands also need to be added for the adjacent supperchannels. Otherwise, the attenuation of the guard bands cannot be adjusted.
That 's all, thank you!
