Some broadband amplifiers do not have a DC blocking capacitor inside and require power supply at the output end, requiring a biasing device.
Some amplifiers integrate capacitors internally, so there is no need for additional biases.
The driving current required for the laser diode is injected through the DC end of the biasing device;
Communication data is injected through the RF end.
The broadband amplifier feeding circuit is affected by parasitic capacitance parameters at high frequencies, resulting in a sharp decline in performance. Therefore, the feeding needs to use BiasTee.