Optical power adjustment system and optical power adjustment apparatus

An optical power adjustment system comprising:

• a multi-mode light source comprising a source output port configured to output a multi-mode optical signal, and wherein the multi-mode optical signal comprises N transverse-mode optical signals, and wherein N=2M and M is an integer greater than 1;
• a mode demultiplexer configured to convert the N transverse-mode optical signals into N fundamental-mode optical signals, wherein the mode demultiplexer comprises:
• a demultiplexer input port coupled to the source output port;
• and
• a demultiplexer output port configured to output the N fundamental-mode optical signals;
• and
• an optical power adjustment apparatus comprising:
• an adjustment input port coupled to the demultiplexer output port;
• an adjustment output port;
• M optical power adjustment modules, wherein each optical power adjustment module comprises a plurality of phase shifters, wherein the M optical power adjustment modules are sequentially arranged from the adjustment input port to the adjustment output port, wherein the M optical power adjustment modules are coupled together in series, wherein the M optical power adjustment modules comprise a Kth optical power adjustment module comprising 2K−1 multi-mode interferometers (MMIs), wherein each MMI comprises 2M−K+1 input ports and 2M−K+1 output ports, wherein 1≤K≤M, wherein an Ith input port or a (2M−K+1−I+1)th input port in the 2M−K+1 input ports is coupled to one phase shifter of the phase shifters, and wherein 1≤I≤2M−K+1;
• and
• a control apparatus, wherein the control apparatus is electrically coupled to the M optical power adjustment modules, and wherein the control apparatus is configured to adjust the phase shifters in the Kth optical power adjustment module to enable a first phase difference between a first optical signal input from the Ith input port of each MMI and a second optical signal input from the (2M−K+1−I+1)th input port of the MMI to be 0 or an integer multiple of 2π, and enable a first output optical power of an Ith output port of each MMI to be the same as a second output optical power of a (2M−K+1−I+1)th output port of the MMI.