The　existing　busbar　energy　extraction　and　laser　energy　supply　methods　on　the　high-voltage　side　of　a　light-transmitting　current　transformer　suffer　from　the　problems　of　power　supply　dead　zones,　low　energy　conversion　efficiency,　and　insufficient　service　life.　Thus　an　ultra-low　power　optoelectronic　transmission　system　scheme　based　on　four-level　coding　and　weak　light　communication　is　proposed.　First,　a　three-state　gate　circuit　is　designed　to　encode　the　sampling　clock　and　data　signal　of　the　signal　sampling　module　into　a　four-level　signal.　Then,　the　four-level　signal　is　converted　into　an　optical　signal　and　transmitted　to　the　low-voltage　side　through　an　optical　fiber　using　an　ultra-high　brightness　and　ultra-low　power　LED.　Finally,　the　signal　is　decoded　at　the　low　voltage　side　using　a　high-sensitivity　avalanche　photodiode　detector　for　weak　light　detection　and　then　input　to　the　decoding　circuit.　The　ultra-low　power　system　is　applied　to　the　light-transmitting　current　transformer　for　experimental　verification.　The　results　show　that　it　can　meet　the　requirements　of　0.2-level　accuracy,　and　the　average　power　consumption　of　the　high-voltage　side　can　be　reduced　to　3.91　mW.　Because　of　the　ultra-low　power　consumption　of　the　system,　the　high-voltage　side　can　adopt　a　reliable　energy　supply　scheme　such　as　a　large-capacity　battery　or　low-power　photovoltaic　system.　This　solves　the　problem　of　power　supply　and　improves　stability　and　reliability.　©　2024　Power　System　Protection　and　Control　Press.　All　rights　reserved.