Methods and apparatus for coherent signal amplification and detection

摘要

A coherent receiver generates a reference signal 401 with a defined phase and inputs the reference signal and a first data signal 111 to a first mixer 500. The first mixer outputs first 501 and second 502 mixed signals. The first mixed signal and a second data signal 121 are input to a first detection unit 610. Similarly, the second mixed signal and a third data signal 122 input are input to a second detection unit 620. The first and second detection units output first 710 and second 720 difference signals, respectively, which are summed 8. As shown in Figure 4, if there more than 3 input signals, additional mixers 510, 520 are provided. Each of these additional mixers receives an output from another mixer (e.g. the first mixer) and a data signal and outputs mixed signals to two detection units, two mixers or a mixer and a detection unit. The mixers may be arranged in a hierarchical array comprising multiple layers 50, 51, of mixers. The invention may be applied to continuous variable quantum key distribution (CV-QKD) to distribute the power of a reference beam without exceeding the saturation power of a detection unit.