SHF T851 A: The group delay optimized version of the SHF T850 C
Group delay is a measure of how much time delay a signal’s frequency components experience as they pass through (e.g., an amplifier). In an ideal component, group delay should be constant across all relevant frequencies within the system’s bandwidth.
In the SHF T851 A design we managed to improve group delay behavior while roughly keeping the basic parameters such as gain, bandwidth and output power of the predecessor SHF T850 C.
Digital signal processing (DSP) techniques such as pre-emphasis or feed-forward equalization (FFE) can potentially compensate for group delay distortions. To rule out any influence of such DSP, we show a comparison of the the SHF T850 C and the group delay improved T851 A without any pre-compensation or filtering. The signals below were sampled directly with a 120 GHz sampling scope.
It can be clearly seen that the SHF T851 A outperforms the SHF T850 C when comparing the raw signal fidelity beyond 100 GBaud. Even if this effect might be reduced in case a powerful pre-emphasis or filtering is utilized, integrating the SHF T851 A into such system would reduce the need for resource-hungry DSP, simplifies hardware, and reduces latency.
224 Gbps (112 GBaud)
Input
Output of SHF T850 C
Output of SHF T851 A
256 Gbps (128 GBaud)
Input
Output of SHF T850 C
Output of SHF T851 A