Chiyambi cha Ukadaulo wa PAM4

Musanamvetse ukadaulo wa PAM4, kodi ukadaulo wa modulation ndi chiyani? Ukadaulo wa modulation ndi njira yosinthira ma signal a baseband (ma signal amagetsi osaphika) kukhala ma signal otumizira mauthenga. Pofuna kuonetsetsa kuti kulumikizana kuli bwino komanso kuthana ndi mavuto pakutumiza ma signal kutali, ndikofunikira kusamutsa ma signal spectrum kupita ku njira yolumikizira ma frequency ambiri kudzera mu modulation kuti atumize mauthenga.

PAM4 ndi njira yosinthira ma pulse amplitude modulation (PAM) ya dongosolo lachinayi.

Chizindikiro cha PAM ndi ukadaulo wotchuka wotumizira ma signal pambuyo pa NRZ (Non Return to Zero).

Chizindikiro cha NRZ chimagwiritsa ntchito milingo iwiri ya chizindikiro, yapamwamba ndi yotsika, kuyimira 1 ndi 0 ya chizindikiro cha digito, ndipo chimatha kutumiza chidziwitso cha logic cha 1 pang'ono pa wotchi iliyonse.

Chizindikiro cha PAM4 chimagwiritsa ntchito milingo inayi yosiyanasiyana ya chizindikiro potumiza chizindikiro, ndipo nthawi iliyonse ya wotchi imatha kutumiza ma bits awiri a chidziwitso cha logic, chomwe ndi 00, 01, 10, ndi 11.
Chifukwa chake, pansi pa mikhalidwe yomweyi ya baud rate, bit rate ya PAM4 signal ndi kawiri kuposa ya NRZ signal, zomwe zimapangitsa kuti transmission igwire bwino ntchito komanso kuchepetsa ndalama.

Ukadaulo wa PAM4 wakhala ukugwiritsidwa ntchito kwambiri pankhani yolumikizirana kwa ma signali mwachangu. Pakadali pano, pali module ya transceiver ya 400G yochokera ku ukadaulo wa PAM4 modulation wa malo osungira deta ndi module ya transceiver ya 50G yochokera ku ukadaulo wa PAM4 modulation wa netiweki yolumikizirana ya 5G.

Njira yogwiritsira ntchito module ya 400G DML optical transceiver kutengera PAM4 modulation ndi iyi: potumiza zizindikiro za unit, njira 16 zolandilidwa za zizindikiro zamagetsi za 25G NRZ zimalowetsedwa kuchokera ku unit yamagetsi, zomwe zimakonzedwa kale ndi purosesa ya DSP, PAM4 modulated, ndi njira 8 zotulutsira zizindikiro zamagetsi za 25G PAM4, zomwe zimayikidwa pa driver chip. Zizindikiro zamagetsi zothamanga kwambiri zimasinthidwa kukhala njira 8 za zizindikiro zamagetsi zothamanga kwambiri za 50Gbps kudzera mu njira 8 za lasers, zophatikizidwa ndi wavelength division multiplexer, ndikupangidwa kukhala njira imodzi ya 400G high-speed optical signal output. Polandira zizindikiro za unit, chizindikiro chowala cha 1-channel 400G high-speed optical chimalowetsedwa kudzera mu unit ya optical interface, chimasinthidwa kukhala chizindikiro chowala cha 8-channel 50Gbps high-speed optical kudzera mu demultiplexer, chimalandiridwa ndi optical receiver, ndikusinthidwa kukhala chizindikiro chamagetsi. Pambuyo pobwezeretsa wotchi, kukulitsa, kulinganiza, ndi kuchotsera PAM4 ndi chipangizo chopangira DSP, chizindikiro chamagetsi chimasinthidwa kukhala njira 16 za chizindikiro chamagetsi cha 25G NRZ.

Gwiritsani ntchito ukadaulo wa PAM4 modulation pa ma module a 400Gb/s. Module ya 400Gb/s yochokera pa modulation ya PAM4 imatha kuchepetsa kuchuluka kwa ma laser ofunikira kumapeto kwa transmitter ndikuchepetsanso kuchuluka kwa olandila ofunikira kumapeto kwa receiver chifukwa chogwiritsa ntchito njira zapamwamba kwambiri poyerekeza ndi NRZ. PAM4 modulation imachepetsa kuchuluka kwa zigawo za optical mu optical module, zomwe zingabweretse zabwino monga kuchepetsa ndalama zosonkhanitsira, kuchepetsa kugwiritsa ntchito mphamvu, komanso kukula kochepa kwa ma phukusi.

Pali kufunikira kwa ma module a 50Gbit/s optical mu ma network a 5G transmission ndi backhaul, ndipo yankho lochokera ku zipangizo za 25G optical komanso lowonjezeredwa ndi PAM4 pulse amplitude modulation format likugwiritsidwa ntchito kuti likwaniritse zofunikira zotsika mtengo komanso zapamwamba za bandwidth.

Pofotokoza zizindikiro za PAM-4, ndikofunikira kusamala kusiyana pakati pa kuchuluka kwa baud ndi kuchuluka kwa bit. Pa zizindikiro zachikhalidwe za NRZ, popeza chizindikiro chimodzi chimatumiza deta pang'ono, kuchuluka kwa bit ndi kuchuluka kwa baud ndizofanana. Mwachitsanzo, mu 100G Ethernet, pogwiritsa ntchito zizindikiro zinayi za 25.78125GBaud potumiza, kuchuluka kwa bit pa chizindikiro chilichonse ndi 25.78125Gbps, ndipo zizindikiro zinayi zimapeza kutumiza kwa chizindikiro cha 100Gbps; Pa zizindikiro za PAM-4, popeza chizindikiro chimodzi chimatumiza deta pang'ono, kuchuluka kwa bit komwe kungatumizidwe ndi kawiri kuposa kuchuluka kwa baud. Mwachitsanzo, pogwiritsa ntchito njira zinayi za zizindikiro za 26.5625GBaud potumiza mu 200G Ethernet, kuchuluka kwa bit pa njira iliyonse ndi 53.125Gbps, ndipo njira zinayi za zizindikiro zimatha kufikira kutumiza kwa chizindikiro cha 200Gbps. Pa 400G Ethernet, ikhoza kukwaniritsidwa ndi njira 8 za zizindikiro za 26.5625GBaud.