Silicon photonics
Which correctly describes the concept of "linear drive" (called linear pluggable optics, LPO, etc.) in optical transceivers?
- AThe received optical signal is converted to digital inside the module, cleaned up by a DSP, and then retransmitted
- BMany lasers are arranged in a line to send many wavelengths into a single fiber simultaneously
- CThe in-module DSP is omitted, and the signal from the host SerDes is used directly for modulation through linear amplifiers
Show answer and explanation
Answer: C. The in-module DSP is omitted, and the signal from the host SerDes is used directly for modulation through linear amplifiers
In conventional high-speed optical transceivers, a DSP (digital signal processing circuit) in the module re-receives the electrical signal from the host, reshapes and compensates the waveform, and then drives the modulator through a driver. The DSP accounts for a large share of module power consumption. In linear drive, the DSP is omitted and only a linear driver and TIA remain, with signal compensation left to the equalizers in the SerDes on the host side, such as the switch IC. This greatly reduces power consumption and latency. Converting the signal to digital and reshaping it is the conventional configuration using a DSP.