An OTN DCI Box is a compact optical transport device for data center interconnect. OTN means Optical. Data Center Interconnect (DCI) systems connect two or more data centers together over tens or up to thousands of kilometers using optical transmission. In this paper, we will discuss the current architecture and the evolution towards 400ZR inter aces along with some related key tech inks with higher rate coherent WDM interfaces. This intermediate domain, encompassing reaches from 500.